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Air pollution is the contamination of air due to the presence of substances in the
atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
that are harmful to the
health Health, according to the World Health Organization, is "a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity".World Health Organization. (2006)''Constitution of the World Health Organiza ...
of
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s and other
living beings Life form (also spelled life-form or lifeform) is an wikt:entity, entity that is Life, living, such as plants (flora) and animals (fauna). It is estimated that more than 99% of all species that ever existed on Earth, amounting to over five billi ...
, or cause damage to the
climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
or to materials. There are many different types of air pollutants, such as gases (including
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
,
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
,
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
, nitrous oxides,
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
,
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
and
chlorofluorocarbons Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propa ...
),
particulates Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
(both organic and inorganic), and biological molecules. Air pollution can cause diseases, allergies, and even death to humans; it can also cause harm to other living organisms such as animals and food crops, and may damage the
natural Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
environment (for example,
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
,
ozone depletion Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...
or
habitat degradation Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
) or
built environment The term built environment refers to human-made conditions and is often used in architecture, landscape architecture, urban planning, public health, sociology, and anthropology, among others. These curated spaces provide the setting for human ac ...
(for example,
acid rain Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid ...
). Air pollution can be caused by both human activities and natural phenomena. Air pollution is a significant
risk factor In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...
for a number of pollution-related diseases, including
respiratory infection Respiratory tract infections (RTIs) are infectious diseases involving the respiratory tract. An infection of this type usually is further classified as an upper respiratory tract infection (URI or URTI) or a lower respiratory tract infection (LRI ...
s,
heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...
,
COPD Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce mu ...
,
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
and
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
. Growing evidence suggests that air pollution exposure may be associated with reduced IQ scores, impaired cognition, increased risk for psychiatric disorders such as depression and detrimental
perinatal Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal devel ...
health. The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the
cardiovascular system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, and the individual's health status and genetics. Outdoor air pollution attributable to fossil fuel use alone causes ~3.61 million deaths annually, making it one of the top contributors to human death, with anthropogenic ozone and PM2.5 causing ~2.1 million. Overall, air pollution causes the deaths of around 7 million people worldwide each year, or a global mean loss of life expectancy (LLE) of 2.9 years, and is the world's largest single environmental health risk, which has not shown significant
progress Progress is the movement towards a refined, improved, or otherwise desired state. In the context of progressivism, it refers to the proposition that advancements in technology, science, and social organization have resulted, and by extension wi ...
since at least 2015. Indoor air pollution and poor urban air quality are listed as two of the world's worst
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...
pollution problems in the 2008
Blacksmith Institute Pure Earth is a New York City-based international not-for-profit organization founded in 1999 that works to identify, clean up, and solve pollution problems in low- and middle-income countries, where high concentrations of toxic pollution have dev ...
World's Worst Polluted Places report. The scope of the air pollution crisis is large: 90% of the world's population breathes dirty air to some degree. Although the health consequences are extensive, the way the problem is handled is considered largely haphazard or neglected. Productivity losses and degraded quality of life caused by air pollution are estimated to cost the world economy $5 trillion per year but, along with health and mortality impacts, are an externality to the contemporary
economic system An economic system, or economic order, is a system of Production (economics), production, resource allocation and Distribution (economics), distribution of goods and services within a society or a given geographic area. It includes the combinati ...
and most human activity, albeit sometimes being moderately regulated and monitored. Various pollution control technologies and strategies are available to reduce air pollution. Several international and national legislation and regulation have been developed to limit the negative effects of air pollution. Local rules, when properly executed, have resulted in significant advances in
public health Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the det ...
. Some of these efforts have been successful at the international level, such as the
Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion Ozone depletion consists of two related events observed sinc ...
, which reduced the release of harmful
ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
depleting chemicals, and the 1985 Helsinki Protocol, which reduced sulphur emissions, while others, such as international action on climate change, have been less successful.


Sources of air pollution


Anthropogenic (human-made) sources

These are mostly related to the burning of fuel. * Stationary sources include: **
fossil-fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ma ...
power plants and
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
power plants both have smoke stacks (see for example
environmental impact of the coal industry The health and environmental impact of the coal industry includes issues such as land use, waste management, water and air pollution, caused by the coal mining, processing and the use of its products. In addition to atmospheric pollution, coal ...
) ***Oil and gas sites that have methane leaks ** burning of traditional biomass such as
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
, crop waste and dung. (In developing and poor countries, traditional biomass burning is the major source of air pollutants. It is also the main source of particulate pollution in many developed areas including the UK & New South Wales. Its pollutants include PAHs.) ** manufacturing facilities (factories) *** a 2014 study found that in China equipment-, machinery-, and devices-manufacturing and construction sectors contributed more than 50% of air pollutant emissions. This high emission is due to high
emission intensity An emission intensity (also carbon intensity or C.I.) is the emission rate of a given pollutant relative to the intensity of a specific activity, or an industrial production process; for example grams of carbon dioxide released per megajoule o ...
and high emission factors in its industrial structure. ** waste incineration (incinerators as well as open and uncontrolled fires of mismanaged waste, making up about a fourth of municipal solid terrestrial waste) ** furnaces and other types of fuel-burning heating devices * Mobile sources include
motor vehicles A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on Track (rail transport), rails (such as trains or trams) and is used for the transportation of pe ...
, trains (particularly
diesel locomotive A diesel locomotive is a type of railway locomotive in which the prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conveyed to the driving whee ...
s and
DMUs A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also ...
), marine vessels and aircraft as well as rockets and re-entry of components and
debris Debris (, ) is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can refer to ...
. The air pollution externality of cars enters the air from the
exhaust gas Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...
and car tires (including
microplastics Microplastics are fragments of any type of plastic less than in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems from a v ...
). Vehicles were reported to be "producing about one-third of all U.S. air pollution" and are a major driver of
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. * Agriculture and forest management strategies using controlled burns. Practices like
slash-and-burn Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area. The downed veget ...
in forests like the Amazon cause large air pollution with the
deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...
. Controlled or prescribed burning is a practice used in forest management, agriculture, prairie restoration, and greenhouse gas reduction. Foresters can use controlled fire as a tool because fire is a natural feature of both forest and grassland ecology. Controlled burning encourages the sprouting of some desirable forest trees, resulting in a forest renewal. There are also sources from processes other than combustion: * Fumes from
paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...
,
hair spray Hair spray (also hair lacquer or spritz) is a common cosmetic hairstyling product that is sprayed onto hair to protect against humidity and wind. Hair sprays typically consist of several components for the hair as well as a propellant. Ingr ...
, varnish,
aerosol spray Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. It comprises a can or bottle that contains a payload, and a propellant under pressure. When the container's valve is opened, the payload is forced out ...
s and other solvents. These can be substantial; emissions from these sources was estimated to account for almost half of pollution from
volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a ...
in the Los Angeles basin in the 2010s. * Waste deposition in landfills produces methane. *
Nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...
s, toxic gases, germ warfare, and rocketry are examples of military resources. * Agricultural emissions and emissions from meat production or livestock contribute substantially to air pollution ** Fertilized farmland may be a major source of nitrogen oxides.


Natural sources

*
Dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
from natural sources, usually large areas of land with little vegetation or no vegetation *
Methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
, emitted by the
digestion Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...
of food by
animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s, for example
cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
*
Radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...
gas from
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
within the
Earth's crust Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
. Radon is a colorless, odorless, naturally occurring, radioactive
noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...
that is formed from the decay of radium. It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after
cigarette A cigarette is a narrow cylinder containing a combustible material, typically tobacco, that is rolled into thin paper for smoking. The cigarette is ignited at one end, causing it to smolder; the resulting smoke is orally inhaled via the opp ...
smoking. *
Smoke Smoke is a suspension of airborne particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product ...
and
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
from
wildfires A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...
. During periods of active wildfires, smoke from uncontrolled biomass combustion can make up almost 75% of all air pollution by concentration. * Vegetation, in some regions, emits environmentally significant amounts of
volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a ...
(VOCs) on warmer days. These VOCs react with primary anthropogenic pollutants – specifically, NOx, SO2, and anthropogenic organic carbon compounds – to produce a seasonal haze of secondary pollutants. Black gum, poplar, oak and willow are some examples of vegetation that can produce abundant VOCs. The VOC production from these species result in ozone levels up to eight times higher than the low-impact tree species. *
Volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
activity, which produces
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
,
chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
, and ash particulates


Emission factors

Air pollutant Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different type ...
emission factors are reported representative values that aim to link the quantity of a pollutant released into the ambient air to an activity connected with that pollutant's release. The weight of the pollutant divided by a unit weight, volume, distance, or time of the activity generating the pollutant is how these factors are commonly stated (e.g., kilogrammes of particulate emitted per tonne of coal burned). These criteria make estimating emissions from diverse sources of pollution easier. Most of the time, these components are just averages of all available data of acceptable quality, and they are thought to be typical of long-term averages. There are 12 compounds in the list of
persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
s.
Dioxin Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 *Dibenzo-1,4-dioxin, the parent compound also known as ...
s and
furan Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly ...
s are two of them and intentionally created by combustion of organics, like open burning of plastics. These compounds are also endocrine disruptors and can mutate the human genes. The
United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
has published a compilation of air pollutant emission factors for a wide range of industrial sources. The United Kingdom, Australia, Canada and many other countries have published similar compilations, as well as the
European Environment Agency The European Environment Agency (EEA) is the agency of the European Union (EU) which provides independent information on the environment. Definition The European Environment Agency (EEA) is the agency of the European Union (EU) which provides i ...
.


Pollutants

An air pollutant is a material in the air that can have adverse effects on humans and the ecosystem. The substance can be solid particles, liquid droplets, or gases. A pollutant can be of natural origin or man-made. Pollutants are classified as primary or secondary. Primary pollutants are usually produced by processes such as ash from a volcanic eruption. Other examples include
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
gas from motor vehicle exhausts or
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact.
Ground level ozone Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the atmosphere of Earth, Earth's atmosphere), with an average concentration of 20–30 parts per billion by v ...
is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants. Pollutants emitted into the atmosphere by human activity include: *
Carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
(): Because of its role as a
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
it has been described as "the leading pollutant" and "the worst climate pollutant". Carbon dioxide is a natural component of the atmosphere, essential for plant life and given off by the human
respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
. This question of terminology has practical effects, for example as determining whether the U.S. Clean Air Act is deemed to regulate emissions. currently forms about 410 parts per million (ppm) of
earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
, compared to about 280 ppm in pre-industrial times, and billions of metric tons of are emitted annually by burning of
fossil fuels A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ...
. increase in earth's atmosphere has been accelerating. *
Sulfur oxide Sulfur oxide refers to many types of sulfur and oxygen containing compounds such as SO, SO2, SO3, S7O2, S6O2, S2O2, etc. Sulfur oxide (SO''x'') refers to one or more of the following: * Lower sulfur oxides (S''n''O, S7O2 and S6O2) * Sulfur mono ...
s (SOx): particularly sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus
acid rain Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid ...
is formed. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources. *
Nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...
s (NOx): Nitrogen oxides, particularly
nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...
, are expelled from high temperature combustion, and are also produced during
thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...
s by
electric discharge An electric discharge is the release and transmission of electricity in an applied electric field through a medium such as a gas (ie., an outgoing flow of electric current through a non-metal medium).American Geophysical Union, National Research C ...
. They can be seen as a brown
haze Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classificati ...
dome above or a plume downwind of cities. Nitrogen dioxide is a chemical compound with the formula NO2. It is one of several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown toxic gas has a characteristic sharp, biting odor. *
Carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
(CO): CO is a colorless, odorless, toxic gas. It is a product of
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
of fuel such as natural gas, coal or wood. Vehicular exhaust contributes to the majority of carbon monoxide let into the atmosphere. It creates a smog type formation in the air that has been linked to many lung diseases and disruptions to the natural environment and animals. *
Volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a ...
(VOC): VOCs are a well-known outdoor air pollutant. They are categorized as either methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life of methane in the atmosphere. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound often associated with industrial use. * Particulate matter/particles, also known as particulate matter (PM), atmospheric particulate matter (APM), or fine particles, are microscopic solid or liquid particles suspended in a gas. Aerosol, on the other hand, is a mixture of particles and gas. Volcanoes, dust storms, forest and grassland fires, living plants, and sea spray are all sources of particles. Aerosols are produced by human activities such as the combustion of fossil fuels in automobiles, power plants, and numerous industrial processes. Averaged worldwide, anthropogenic aerosols – those made by human activities – currently account for approximately 10% of our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer. Particulates are related to respiratory infections and can be particularly harmful to those with conditions like
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
. * Persistent free radicals connected to airborne fine particles are linked to cardiopulmonary disease. * Toxic
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s, such as
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
and mercury, especially their compounds. *
Chlorofluorocarbons Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propa ...
(CFCs): Emitted from goods that are now prohibited from use; harmful to the ozone layer. These are gases emitted by air conditioners, freezers, aerosol sprays, and other similar devices. CFCs reach the stratosphere after being released into the atmosphere. They interact with other gases here, causing harm to the ozone layer. UV rays are able to reach the earth's surface as a result of this. This can result in skin cancer, eye problems, and even plant damage. *
Ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
: Emitted mainly by agricultural waste. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous. In the atmosphere, ammonia reacts with
oxides of nitrogen Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...
and sulfur to form secondary particles. *
Odor An odor (American English) or odour (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is caused by one or more volatilized chemical compounds ...
s: Such as from garbage, sewage, and industrial processes. * Radioactive pollutants: Produced by
nuclear explosions A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, tho ...
, nuclear events, war explosives, and natural processes such as the
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
of
radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...
. *
Polycyclic Aromatic Hydrocarbons A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
(PAHs): a group of aromatic compounds formed from the incomplete combustion of organic compounds including coal and oil and tobacco. Secondary pollutants include: * Photochemical
smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and '' fog'' to refer to smoky fog due to its opacity, and odor. The word was then inte ...
: particles are formed from gaseous primary contaminants and chemicals. Smog is a type of pollution that occurs in the atmosphere. Smog is caused by a huge volume of coal being burned in a certain region, resulting in a mixture of smoke and sulphur dioxide. Modern smog is usually caused by automotive and industrial emissions, which are acted on in the atmosphere by UV light from the sun to produce secondary pollutants, which then combine with the primary emissions to generate photochemical smog. *
Ground level ozone Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the atmosphere of Earth, Earth's atmosphere), with an average concentration of 20–30 parts per billion by v ...
(O3): Ozone is created when NOx and VOCs mix. It is a significant part of the troposphere. It's also an important part of the ozone layer, which can be found in different sections of the stratosphere. Photochemical and chemical reactions involving it fuel many of the chemical activities that occur in the atmosphere during the day and night. It is a pollutant and a component of smog that is produced in large quantities as a result of human activities (mostly the combustion of fossil fuels). *
Peroxyacetyl nitrate Peroxyacetyl nitrate is a peroxyacyl nitrate. It is a secondary pollutant present in photochemical smog. It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen dioxide gas. It is a lachrymatory substance, meaning tha ...
(C2H3NO5): similarly formed from NOx and VOCs. Minor air pollutants include: * A large number of minor
hazardous air pollutants Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...
. Some of these are regulated in USA under the Clean Air Act and in Europe under the Air Framework Directive. * A variety of
persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
s, which can attach to particulates Persistent organic pollutants are organic compounds that are resistant to environmental degradation due to chemical, biological, or photolytic processes (POPs). As a result, they've been discovered to survive in the environment, be capable of long-range transmission, bioaccumulate in human and animal tissue, biomagnify in food chains, and pose a major threat to human health and the ecosystem. File:Air pollution by industrial chimneys.jpg, Before flue-gas desulfurization was installed, the emissions from this power plant in
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...
contained excessive amounts of
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
. File:Thermal-oxidizer-rto.jpg,
Thermal oxidiser A thermal oxidizer (also known as thermal oxidiser, or thermal incinerator) is a process unit for air pollution control in many chemical plants that decomposes hazardous gases at a high temperature and releases them into the atmosphere. Princip ...
s are air pollution abatement options for
hazardous air pollutant The National Emission Standards for Hazardous Air Pollutants (NESHAP) are air pollution standards issued by the United States Environmental Protection Agency (EPA). The standards, authorized by the Clean Air Act, are for pollutants not covered by ...
s (HAPs),
volatile organic compounds Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a ...
(VOCs), and odorous emissions. File:NASA - Human Fingerprint on Global Air Quality.webm, This video provides an overview of a NASA study on the human fingerprint on global air quality.


Exposure

The risk of air pollution is determined by the pollutant's hazard and the amount of exposure to that pollutant. Air pollution exposure can be measured for a person, a group (such as a neighborhood or a country's children), or an entire population. For example, one would want to determine a geographic area's exposure to a dangerous air pollution, taking into account the various microenvironments and age groups. This can be calculated as an inhalation exposure. This would account for daily exposure in various settings (e.g. different indoor micro-environments and outdoor locations). The exposure needs to include different ages and other demographic groups, especially infants, children, pregnant women, and other sensitive subpopulations. For each specific time that the subgroup is in the setting and engaged in particular activities, the exposure to an air pollutant must integrate the concentrations of the air pollutant with regard to the time spent in each setting and the respective inhalation rates for each subgroup (playing, cooking, reading, working, spending time in traffic, etc.). A little child's inhaling rate, for example, will be lower than that of an adult. A youngster engaging in strenuous exercise will have a faster rate of breathing than a child engaged in sedentary activity. The daily exposure must therefore include the amount of time spent in each micro-environmental setting as well as the kind of activities performed there. The air pollutant concentration in each microactivity/microenvironmental setting is summed to indicate the exposure. For some pollutants such as
black carbon Chemically, black carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuel ...
, traffic related exposures may dominate total exposure despite short exposure times since high concentrations coincide with proximity to major roads or participation in (motorized) traffic. A large portion of total daily exposure occurs as short peaks of high concentrations, but it remains unclear how to define peaks and determine their frequency and health impact. In 2021, the WHO halved its recommended guideline limit for tiny particles from burning fossil fuels. The new limit for
nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...
(NO2) is 75% lower. Growing evidence that air pollution—even when experienced at very low levels—hurts human health, led the WHO to revise its guideline (from 10 µg/m³ to 5 µg/m³) for what it considers a safe level of exposure of particulate pollution, bringing most of the world—97.3 percent of the global population—into the unsafe zone.


Indoor air quality

A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time.
Radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...
(Rn) gas, a
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
, is exuded from the Earth in certain locations and trapped inside houses. Building materials including
carpet A carpet is a textile floor covering typically consisting of an upper layer of pile attached to a backing. The pile was traditionally made from wool, but since the 20th century synthetic fibers such as polypropylene, nylon, or polyester hav ...
ing and plywood emit
formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...
(H2CO) gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry.
Lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
paint can degenerate into
dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
and be inhaled. Intentional air pollution is introduced with the use of air fresheners,
incense Incense is aromatic biotic material that releases fragrant smoke when burnt. The term is used for either the material or the aroma. Incense is used for aesthetic reasons, religious worship, aromatherapy, meditation, and ceremony. It may also b ...
, and other scented items. Controlled wood fires in cook stoves and
fireplace A fireplace or hearth is a structure made of brick, stone or metal designed to contain a fire. Fireplaces are used for the relaxing ambiance they create and for heating a room. Modern fireplaces vary in heat efficiency, depending on the design. ...
s can add significant amounts of harmful smoke particulates into the air, inside and out. Indoor pollution fatalities may be caused by using
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...
s and other chemical sprays indoors without proper ventilation. Carbon monoxide poisoning and fatalities are often caused by faulty vents and chimneys, or by the burning of
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
indoors or in a confined space, such as a tent. Chronic
carbon monoxide poisoning Carbon monoxide poisoning typically occurs from breathing in carbon monoxide (CO) at excessive levels. Symptoms are often described as "flu-like" and commonly include headache, dizziness, weakness, vomiting, chest pain, and confusion. Large e ...
can result even from poorly-adjusted
pilot light Merker Tankless water heating, tankless gas-fired water heater from the 1930s, with pilot light clearly visible through the aperture in the front cover. The large opening allowed for the manual lighting of the pilot light by a lit match or taper ...
s. Traps are built into all domestic
plumbing Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery ...
to keep sewer gas and
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
, out of interiors. Clothing emits
tetrachloroethylene Tetrachloroethylene, also known under the systematic name tetrachloroethene, or perchloroethylene, and many other names (and abbreviations such as "perc" or "PERC", and "PCE"), is a chlorocarbon with the formula Cl2C=CCl2 . It is a colorless li ...
, or other dry cleaning fluids, for days after
dry cleaning Dry cleaning is any cleaning process for clothing and textiles using a solvent other than water. Dry cleaning still involves liquid, but clothes are instead soaked in a water-free liquid solvent. Tetrachloroethylene (perchloroethylene), known i ...
. Though its use has now been banned in many countries, the extensive use of
asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere b ...
in industrial and domestic environments in the past has left a potentially very dangerous material in many localities.
Asbestosis Asbestosis is long-term inflammation and pulmonary fibrosis, scarring of the human lung, lungs due to asbestos, asbestos fibers. Symptoms may include shortness of breath, cough, wheezing, and chest pain, chest tightness. Complications may include ...
is a chronic inflammatory medical condition affecting the tissue of the
lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s. It occurs after long-term, heavy exposure to asbestos from asbestos-containing materials in structures. Those with asbestosis have severe
dyspnea Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathing, breathe well enough. The American Thoracic Society defines it as "a subjective experience of brea ...
(shortness of breath) and are at an increased risk regarding several different types of
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
. As clear explanations are not always stressed in non-technical literature, care should be taken to distinguish between several forms of relevant diseases. According to the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
(WHO), these may be defined as asbestosis, lung cancer, and peritoneal mesothelioma (generally a very rare form of cancer, when more widespread it is almost always associated with prolonged exposure to asbestos). Biological sources of air pollution are also found indoors, as gases and airborne particulates.
Pet A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence ...
s produce dander, people produce dust from minute skin flakes and decomposed hair,
dust mites House dust mites (HDM, or simply dust mites) are various species of acariform mites belonging to the family Pyroglyphidae that are found in association with dust in dwellings. They are known for causing allergies. Biology Species The curren ...
in bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane,
mold A mold () or mould () is one of the structures certain fungus, fungi can form. The dust-like, colored appearance of molds is due to the formation of Spore#Fungi, spores containing Secondary metabolite#Fungal secondary metabolites, fungal seco ...
forms on walls and generates
mycotoxins A mycotoxin (from the Greek μύκης , "fungus" and τοξίνη , "toxin") is a toxic secondary metabolite produced by organisms of kingdom Fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' ...
and spores,
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
systems can incubate Legionnaires' disease and mold, and
houseplant A houseplant, sometimes known as a pot plant, potted plant, or an indoor plant, is an ornamental plant that is grown indoors. As such, they are found in places like residences and offices, mainly for decorative purposes. Common houseplants are us ...
s, soil and surrounding
gardens A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate both ...
can produce
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
, dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature.


Health effects

Even at levels lower than those considered safe by United States regulators, exposure to three components of air pollution, fine
particulate Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The te ...
matter,
nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...
and
ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
, correlates with cardiac and respiratory illness. In 2020, pollution (including air pollution) was a contributing factor to one in eight deaths in Europe, and was a significant
risk factor In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...
for pollution-related diseases including
heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...
,
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
and
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
. The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing,
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
and worsening of existing respiratory and cardiac conditions. These effects can result in increased medication use, increased doctor or
emergency department An emergency department (ED), also known as an accident and emergency department (A&E), emergency room (ER), emergency ward (EW) or casualty department, is a medical treatment facility specializing in emergency medicine, the acute care of pati ...
visits, more hospital admissions and premature death. The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, and the individual's health status and genetics. The most common sources of air pollution include particulates, ozone, nitrogen dioxide, and sulfur dioxide. Children aged less than five years who live in developing countries are the most vulnerable population in terms of total deaths attributable to indoor and outdoor air pollution. Under the Clean Air Act (CAA), U.S. EPA sets limits on certain air pollutants, including setting limits on how much can be in the air anywhere in the United States. New research demonstrates that the biological and health outcomes of mixed exposures (Example PM + Ozone) could be significantly greater than individual exposures.Air pollution has both acute and chronic effects on human health, affecting a number of different systems and organs. It ranges from minor upper respiratory irritation to chronic respiratory and heart disease, lung cancer, acute respiratory infections in children and chronic bronchitis in adults, aggravating pre-existing heart and lung disease, or asthmatic attacks. In addition, short and long term exposures have also been linked with premature mortality and reduced life expectancy.


Mortality

The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
estimated in 2014 that every year air pollution causes the premature death of some 7 million people worldwide. Studies published in March 2019 indicated that the number may be around 8.8 million. A 2022 review concluded that air pollution was responsible for 6.67 (5.90–7.49) million premature deaths in 2019. It concluded that since 2015 little real
progress Progress is the movement towards a refined, improved, or otherwise desired state. In the context of progressivism, it refers to the proposition that advancements in technology, science, and social organization have resulted, and by extension wi ...
against (superordinate)
pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
, which remained at ~9 million earlier deaths, can be identified. Causes of deaths include
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
s,
heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...
, COPD, lung cancer, and lung infections. Urban outdoor air pollution is estimated to cause 1.3 million deaths worldwide per year. Children are particularly at risk due to the immaturity of their respiratory organ systems. In 2015, outdoor air pollution, mostly by PM2.5, was estimated to lead to 3.3 (95% CI 1.61–4.81) million premature deaths per year worldwide, predominantly in Asia. In 2021, the WHO reported that outdoor air pollution was estimated to cause 4.2 million premature deaths worldwide in 2016. A 2020 study indicates that the global mean loss of life expectancy (LLE; similar to YPLL) from air pollution in 2015 was 2.9 years, substantially more than, for example, 0.3 years from all forms of direct violence, albeit a significant fraction of the LLE is unavoidable. Moreover, communities with the most exceptional aging have low ambient air pollution, suggesting a link between air pollution levels and
longevity The word " longevity" is sometimes used as a synonym for "life expectancy" in demography. However, the term ''longevity'' is sometimes meant to refer only to especially long-lived members of a population, whereas ''life expectancy'' is always d ...
. A study published in 2022 in '' GeoHealth'' concluded that eliminating energy-related fossil fuel emissions in the United States would prevent 46,900–59,400 premature deaths each year and provide $537–$678 billion in benefits from avoided PM2.5-related illness and death.


By region

India and China have the highest death rate due to air pollution. India also has more deaths from asthma than any other nation according to the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
. In December 2013 air pollution was estimated to kill 500,000 people in China each year. There is a positive correlation between
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...
-related deaths and air pollution from motor vehicle emissions. Annual premature European deaths caused by air pollution are estimated at 430,000 to 800,000. An important cause of these deaths is nitrogen dioxide and other nitrogen oxides (NOx) emitted by road vehicles. In a 2015 consultation document the UK government disclosed that nitrogen dioxide is responsible for 23,500 premature UK deaths per annum. Across the
European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...
, air pollution is estimated to reduce
life expectancy Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of its birth, current age, and other demographic factors like sex. The most commonly used measure is life expectancy at birth ...
by almost nine months.


Guidelines

The US EPA has estimated that limiting ground-level ozone concentration to 65 parts per billion (ppb), would avert 1,700 to 5,100 premature deaths nationwide in 2020 compared with the 75 ppb standard. The agency projected the more protective standard would also prevent an additional 26,000 cases of aggravated asthma, and more than a million cases of missed work or school. Following this assessment, the EPA acted to protect public health by lowering the National Ambient Air Quality Standards (NAAQS) for ground-level ozone to 70 ppb. A new economic study of the health impacts and associated costs of air pollution in the
Los Angeles Basin The Los Angeles Basin is a sedimentary Structural basin, basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an wikt:anomalous, anomalous group of east-west trending chains of mountai ...
and
San Joaquin Valley The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven c ...
of Southern California shows that more than 3,800 people die prematurely (approximately 14 years earlier than normal) each year because air pollution levels violate federal standards. The number of annual premature deaths is considerably higher than the fatalities related to auto collisions in the same area, which average fewer than 2,000 per year. A 2021 study found that outdoor air pollution is associated with substantially increased mortality "even at low pollution levels below the current European and North American standards and WHO guideline values" shortly before the WHO adjusted its guidelines.


Major causes

The largest cause is air pollution generated by
fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
combustion – mostly the production and use of cars, electricity production, and heating. A study by
Greenpeace Greenpeace is an independent global campaigning network, founded in Canada in 1971 by Irving Stowe and Dorothy Stowe, immigrant environmental activists from the United States. Greenpeace states its goal is to "ensure the ability of the Earth t ...
estimates there are 4.5 million annual premature deaths worldwide because of pollutants released by high-emission power stations and vehicle exhausts.
Diesel exhaust Diesel exhaust is the gaseous exhaust produced by a diesel type of internal combustion engine, plus any contained particulates. Its composition may vary with the fuel type or rate of consumption, or speed of engine operation (e.g., idling or at ...
(DE) is a major contributor to combustion-derived particulate matter air pollution. In several human experimental studies, using a well-validated exposure chamber setup, DE has been linked to acute vascular dysfunction and increased thrombus formation. A study concluded that PM2.5 air pollution induced by the contemporary free
trade Trade involves the transfer of goods and services from one person or entity to another, often in exchange for money. Economists refer to a system or network that allows trade as a market. An early form of trade, barter, saw the direct excha ...
and consumption by the G20 nations causes two million premature deaths annually, suggesting that the average lifetime consumption of about ~28 people in these countries causes at least one premature death (average age ~67) while developing countries "cannot be expected" to implement or be able to implement countermeasures without external support or internationally coordinated efforts.


Primary mechanisms

The WHO estimates that in 2016, ~58% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke. The mechanisms linking air pollution to increased cardiovascular mortality are uncertain, but probably include pulmonary and systemic inflammation.


Contemporary annual deaths

A study by scientists of U.K. and U.S. universities that uses a high spatial resolution model and an updated concentration-response function concluded in 2021 that 10.4 million global excess deaths in 2012 and 8.7 million in 2018 – or – were due to air pollution generated by
fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
combustion, significantly higher than earlier estimates and with spatially subdivided mortality impacts. According to the WHO air pollution accounts for 1 in 8 deaths worldwide.


Cardiovascular disease

A 2007 review of evidence found that for the general population, ambient air pollution exposure is a risk factor correlating with increased total mortality from cardiovascular events (range: 12% to 14% per 10 µg/m3 increase) . Air pollution is also emerging as a risk factor for stroke, particularly in developing countries where pollutant levels are highest. A 2007 study found that in women, air pollution is not associated with hemorrhagic but with ischemic stroke. Air pollution was also found to be associated with increased incidence and mortality from coronary stroke in a cohort study in 2011. Associations are believed to be causal and effects may be mediated by vasoconstriction, low-grade inflammation and
atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
. Other mechanisms such as autonomic nervous system imbalance have also been suggested.


Lung disease

Research has demonstrated increased risk of developing asthma and
chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce ...
(COPD) from increased exposure to traffic-related air pollution. Additionally, air pollution has been associated with increased hospitalization and mortality from asthma and COPD. COPD includes diseases such as
chronic bronchitis Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...
and
emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alve ...
. The risk of lung disease from air pollution is greatest for the following groups of people: infants and young children, whose normal breathing is faster than that of older children and adults; the elderly; those who work outside or spend a lot of time outside; and those who have heart or lung disease. A study conducted in 1960–1961 in the wake of the
Great Smog The Great Smog of London, or Great Smog of 1952, was a severe air pollution event that affected London, England, in December 1952. A period of unusually cold weather, combined with an anticyclone and windless conditions, collected airborne poll ...
of 1952 compared 293 London residents with 477 residents of Gloucester, Peterborough, and Norwich, three towns with low reported death rates from chronic bronchitis. All subjects were male postal truck drivers aged 40 to 59. Compared to the subjects from the outlying towns, the London subjects exhibited more severe respiratory symptoms (including cough, phlegm, and dyspnea), reduced lung function ( FEV1 and peak flow rate), and increased sputum production and purulence. The differences were more pronounced for subjects aged 50 to 59. The study controlled for age and smoking habits, so concluded that air pollution was the most likely cause of the observed differences. More studies have shown that air pollution exposure from traffic reduces lung function development in children and lung function may be compromised by air pollution even at low concentrations. It is believed that much like
cystic fibrosis Cystic fibrosis (CF) is a rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. O ...
, by living in a more urban environment serious health hazards become more apparent. Studies have shown that in urban areas people experience
mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
hypersecretion, lower levels of lung function, and more self-diagnosis of chronic bronchitis and emphysema.


Cancer (lung cancer)

Around 300,000 lung cancer deaths were attributed globally in 2019 to exposure to fine particulate matter, PM2.5, contained in air pollution. A review of evidence regarding whether ambient air pollution exposure is a risk factor for cancer in 2007 found solid data to conclude that long-term exposure to
PM2.5 Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
(fine particulates) increases the overall risk of non-accidental mortality by 6% per a 10 microg/m3 increase. Exposure to PM2.5 was also associated with an increased risk of mortality from
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
(range: 15% to 21% per 10 microg/m3 increase) and total cardiovascular mortality (range: 12% to 14% per a 10 microg/m3 increase). The review further noted that living close to busy traffic appears to be associated with elevated risks of these three outcomes – increase in lung cancer deaths, cardiovascular deaths, and overall non-accidental deaths. The reviewers also found suggestive evidence that exposure to PM2.5 is positively associated with mortality from coronary heart diseases and exposure to SO2 increases mortality from lung cancer, but the data was insufficient to provide solid conclusions. Another investigation showed that higher activity level increases deposition fraction of aerosol particles in human lung and recommended avoiding heavy activities like running in outdoor space at polluted areas. In 2011, a large Danish epidemiological study found an increased risk of lung cancer for people who lived in areas with high nitrogen oxide concentrations. In this study, the association was higher for non-smokers than smokers. An additional Danish study, also in 2011, likewise noted evidence of possible associations between air pollution and other forms of cancer, including cervical cancer and brain cancer. A study presented in 2022 outlined the biological basis for how air pollution causes cancer.


Kidney disease

In 2021, a study of 163,197 Taiwanese residents over the period of 2001–2016 estimated that every 5 μg/m3 decrease in the ambient concentration of PM2.5 was associated with a 25% reduced risk of chronic kidney disease development. According to a chord study involving 10,997 atherosclerosis patients, higher PM 2.5 exposure is associate with increased albuminuria.


Fertility


NO2

In women undergoing
IVF In vitro fertilisation (IVF) is a process of fertilisation where an egg is combined with sperm in vitro ("in glass"). The process involves monitoring and stimulating an individual's ovulatory process, removing an ovum or ova (egg or eggs) f ...
treatment, increases in NO2 both at the patient’s address and by the IVF lab were significantly associated with a lower
live birth rate Pregnancy rate is the success rate for getting pregnant. It is the percentage of all attempts that leads to pregnancy, with attempts generally referring to menstrual cycles where insemination or any artificial equivalent is used, which may be simpl ...
. In the general population, there is a significant increase in
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical lo ...
rate in women exposed to NO2 compared to the non-exposed group.


CO

CO exposure is significantly associated with
stillbirth Stillbirth is typically defined as fetal death at or after 20 or 28 weeks of pregnancy, depending on the source. It results in a baby born without signs of life. A stillbirth can result in the feeling of guilt or grief in the mother. The term ...
in the second and third trimester.


Polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
s (PAHs) have been associated with reduced fertility. Benzo(a)pyrene (BaP) is a well-known PAH and carcinogen which is often found in exhaust fumes and cigarette smoke. PAHs have been reported to administer their toxic effects through oxidative stress by increasing the production of
Reactive Oxygen Species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () p ...
(ROS) which can result in inflammation and cell death. More long-term exposure to PAHs can result in
DNA damage DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...
and reduced repair. Exposure to BaP has been reported to reduce
sperm motility Sperm motility describes the ability of sperm to move properly through the female reproductive tract (internal fertilization) or through water (external fertilization) to reach the egg. Sperm motility can also be thought of as the ''quality'', whi ...
and increasing the exposure worsens this effect. Research has demonstrated that more BaPs were found in men with reported fertility issues compared to men without. Studies have also shown that BaPs can affect
folliculogenesis :''Although the process is similar in many animals, this article will deal exclusively with human folliculogenesis.'' In biology, folliculogenesis is the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains a ...
and ovarian development by reducing the number of ovarian germ cells via triggering cell death pathways and inducing inflammation which can lead to ovarian damage.


Particulate Matter

Particulate matter (PM) refers to the collection of solids and liquids suspended in the air. These can be harmful to humans when exposed to in day to day life, and more research has shown that these effects may be more extensive than first thought; particularly on male fertility. Within the spectrum of PM there are different weights, such as
PM2.5 Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
which are tiny particles of 2.5 microns in width or smaller, compared with
PM10 Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The te ...
which are classified as 10 microns in diameter or less. In a study based in California it was found that as exposure to PM2.5 increased sperm motility decreased and morphology became more abnormal. Similarly, in Poland exposure to PM2.5 and PM10 lead to an increase in the percentage of cells with immature
chromatin Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in r ...
(DNA that has not fully developed or has developed abnormally). In Turkey, a study looked at the fertility of men who work as toll collectors and are therefore exposed to high levels of traffic pollutants daily. Traffic pollution often has high levels of PM10 alongside
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
and nitrous oxides. In this study group there were significant differences in
sperm count A semen analysis (plural: semen analyses), also called seminogram or spermiogram, evaluates certain characteristics of a male's semen and the sperm contained therein. It is done to help evaluate male fertility, whether for those seeking pregna ...
and motility when compared to a control group with limited air pollution exposure. In women, whilst overall effects on fertility did not seem significant there was an association was found between increased exposure to PM10 and early miscarriage. Exposure to smaller particulate matter, PM2.5, was seen to have an effect on conception rates in women undergoing
IVF In vitro fertilisation (IVF) is a process of fertilisation where an egg is combined with sperm in vitro ("in glass"). The process involves monitoring and stimulating an individual's ovulatory process, removing an ovum or ova (egg or eggs) f ...
but not with live birth rates.


Ground-level ozone pollution

Ground-level ozone Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the atmosphere of Earth, Earth's atmosphere), with an average concentration of 20–30 parts per billion by v ...
(O3), when in high concentrations, is regarded as an air pollutant and is often found in smog in industrial areas. O3 is largely produced by chemical reactions involving NOx gases (nitrous oxides, especially from combustion) and volatile organic compounds in the presence of sunlight. There is limited research pertaining to the effect that ozone pollution does have on fertility. At present, there is no evidence to suggest that ozone exposure poses a deleterious effect on spontaneous fertility in either females or males. However, there have been studies which suggest that high levels of ozone pollution (often a problem in the summer months) do exert an effect on in vitro fertilisation (IVF) outcomes. In fact, within an IVF population, NOx and ozone pollutants were linked with reduced rates of live birth. Furthermore, whilst most research on this topic is focused on the direct human exposure of air pollution, other studies have analysed the impact of air pollution on gametes and embryos within IVF laboratories. Multiple studies have reported a marked improvement in
embryo quality Embryo quality is the ability of an embryo to perform successfully in terms of conferring a high pregnancy rate and/or resulting in a healthy person. Embryo profiling is the estimation of embryo quality by qualification and/or quantification of va ...
, implantation and pregnancy rates after IVF laboratories have implemented air filters in a concerted effort to reduce levels of air pollution. Therefore, ozone pollution is considered to have a negative impact on the success of
assisted reproductive technologies Assisted reproductive technology (ART) includes medical procedures used primarily to address infertility. This subject involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), cryopreservation of gametes ...
(ART) when occurring at high levels. However, ozone is thought to act in a biphasic manner where a positive effect on live birth is observed when ozone exposure is limited to before IVF embryo implantation. Conversely, a negative effect is demonstrated upon exposure to ozone after embryo implantation. In addition to this, retrospective and prospective studies evaluating the effect of several traffic pollutants (of which ground-level ozone is one) highlighted a significant decrease in live birth rates and miscarriages. In terms of male fertility, ozone is reported to cause a significant decrease in sperm concentration measured in semen after exposure. Similarly, sperm vitality (the proportion of alive spermatozoa in a sample) was demonstrated to be diminished in a handful of studies. This demonstrates that ozone air pollution exhibits a significantly negative effect of air pollution on this parameter. However, findings on the effect of ozone exposure on male fertility are somewhat discordant, highlighting the need for further research.


Children

In the United States, despite the passage of the Clean Air Act in 1970, in 2002 at least 146 million Americans were living in
non-attainment area In United States environmental law, a non-attainment area is an area considered to have air quality worse than the National Ambient Air Quality Standards as defined in the Clean Air Act Amendments of 1970 (P.L. 91-604, Sec. 109). Non-attainment a ...
s – regions in which the concentration of certain air pollutants exceeded federal standards. These dangerous pollutants are known as the
criteria pollutant The U.S. National Ambient Air Quality Standards (NAAQS, pronounced ) are limits on atmospheric concentration of six pollutants that cause smog, acid rain, and other health hazards. Established by the United States Environmental Protection Agency ...
s, and include ozone, particulate matter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. Protective measures to ensure children's health are being taken in cities such as
New Delhi New Delhi (, , ''Naī Dillī'') is the capital of India and a part of the National Capital Territory of Delhi (NCT). New Delhi is the seat of all three branches of the government of India, hosting the Rashtrapati Bhavan, Parliament House ...
, India, where buses now use
compressed natural gas Compressed natural gas (CNG) is a fuel gas mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of , usually in cy ...
to help eliminate the "pea-soup" smog. A recent study in Europe has found that exposure to ultrafine particles can increase
blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
in children. According to a WHO report in 2018, polluted air leads to the poisoning of millions of children under the age of 15, resulting in the death of some six hundred thousand children annually.


Prenatal exposure

Prenatal exposure to polluted air has been linked to a variety of
neurodevelopmental disorder Neurodevelopmental disorders are a group of disorders that affect the development of the nervous system, leading to abnormal brain function which may affect emotion, learning ability, self-control, and memory. The effects of neurodevelopmental ...
s in children. For example, exposure to polycyclic aromatic hydrocarbons (PAH) was associated with reduced IQ scores and symptoms of
anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...
and depression. They can also lead to detrimental
perinatal Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal devel ...
health outcomes that are often fatal in developing countries. A 2014 study found that PAHs might play a role in the development of childhood
attention deficit hyperactivity disorder Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...
(ADHD). Researchers have also begun to find evidence for air pollution as a risk factor for
autism spectrum disorder The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
(ASD). In Los Angeles, children who were living in areas with high levels of traffic-related air pollution were more likely to be diagnosed with autism between 3–5 years of age. The connection between air pollution and neurodevelopmental disorders in children is thought to be related to epigenetic dysregulation of the primordial germ cells, embryo, and fetus during a critical period. Some PAHs are considered endocrine disruptors and are lipid soluble. When they build up in adipose tissue, they can be transferred across the placenta. In addition to all, air pollution has been associated with the prevalence of preterm births.


Infants

Ambient levels of air pollution have been associated with
preterm birth Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks Gestational age (obstetrics), gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 we ...
and
low birth weight Low birth weight (LBW) is defined by the World Health Organization as a birth weight of an infant of or less, regardless of gestational age. Infants born with LBW have added health risks which require close management, often in a neonatal inten ...
. A 2014 WHO worldwide survey on maternal and perinatal health found a statistically significant association between low birth weights (LBW) and increased levels of exposure to PM2.5. Women in regions with greater than average PM2.5 levels had statistically significant higher odds of pregnancy resulting in a low-birth weight infant even when adjusted for country-related variables. The effect is thought to be from stimulating
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
and increasing
oxidative stress Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily Detoxification, detoxify the reactive intermediates or to repair the resulting damage. Disturbances ...
. A study by the University of York found that in 2010 exposure to PM2.5 was strongly associated with 18% of preterm births globally, which was approximately 2.7 million premature births. The countries with the highest air pollution associated preterm births were in South and East Asia, the Middle East, North Africa, and West sub-Saharan Africa. In 2019, ambient particulate matter pollution in Africa resulted in at least 383 000 early deaths, according to new estimates of the cost of air pollution in the continent. This increased from 3.6% in 1990 to around 7.4% of all premature deaths in the area. The source of PM2.5 differs greatly by region. In South and East Asia, pregnant women are frequently exposed to indoor air pollution because of wood and other
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
fuels being used for cooking, which are responsible for more than 80% of regional pollution. In the Middle East, North Africa and West sub-Saharan Africa, fine PM comes from natural sources, such as
dust storm A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transp ...
s. The United States had an estimated 50,000 preterm births associated with exposure to PM2.5 in 2010. A study performed by Wang, et al. between the years of 1988 and 1991 has found a correlation between
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
(SO2) and total suspended particulates (TSP) and preterm births and low birth weights in Beijing. A group of 74,671 pregnant women, in four separate regions of Beijing, were monitored from early pregnancy to delivery along with daily air pollution levels of sulfur Dioxide and TSP (along with other particulates). The estimated reduction in birth weight was 7.3 g for every 100 µg/m3 increase in and 6.9 g for each 100 µg/m3 increase in TSP. These associations were statistically significant in both summer and winter, although, summer was greater. The proportion of low birth weight attributable to air pollution, was 13%. This is the largest attributable risk ever reported for the known risk factors of low birth weight. Coal stoves, which are in 97% of homes, are a major source of air pollution in this area. Brauer et al. studied the relationship between air pollution and proximity to a highway with pregnancy outcomes in a Vancouver cohort of pregnant woman using addresses to estimate exposure during pregnancy. Exposure to NO, NO2, CO, PM10 and PM2.5 were associated with infants born small for gestational age (SGA). Women living less than 50 meters away from an expressway or highway were 26% more likely to give birth to a SGA infant.


"Clean" areas

Even in areas with relatively low levels of air pollution, public health effects can be significant and costly, since a large number of people breathe in such pollutants. A study published in 2017 found that even in areas of the U.S. where ozone and PM2.5 meet federal standards, Medicare recipients who are exposed to more air pollution have higher mortality rates. A 2005 scientific study for the British Columbia Lung Association showed that a small improvement in air quality (1% reduction of ambient PM2.5 and ozone concentrations) would produce $29 million in annual savings in the
Metro Vancouver The Metro Vancouver Regional District (MVRD), or simply Metro Vancouver, is a Canadian political subdivision and corporate entity representing the metropolitan area of Greater Vancouver, designated by provincial legislation as one of the 28 ...
region in 2010. This finding is based on health valuation of lethal (death) and sub-lethal (illness) affects. In 2020, scientists found that the boundary layer air over the Southern Ocean around Antarctica is 'unpolluted' by humans.


Central nervous system

Data is accumulating that air pollution exposure also affects the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
. Air pollution increases the risk of dementia in people over 50 years old. Childhood indoor air pollution may negatively affect cognitive function and neurodevelopment. Prenatal exposure may also affect neurodevelopment. Studies show that air pollution is associated with a variety of developmental disabilities, oxidative stress, and neuro-inflammation and that it may contribute to Alzheimer's disease and Parkinson's disease. Researchers at the
University of Rochester The University of Rochester (U of R, UR, or U of Rochester) is a private university, private research university in Rochester, New York. The university grants Undergraduate education, undergraduate and graduate degrees, including Doctorate, do ...
Medical Center found that early exposure to air pollution causes the same changes in the brain as
autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
and
schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...
. This study was published in the journal ''
Environmental Health Perspectives ''Environmental Health Perspectives'' (''EHP'') is a peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work (peers). It functions as a form of self-regulation by qua ...
'', in June 2014. It also showed that air pollution also affected
short-term memory Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recit ...
, learning ability, and impulsivity. Lead researcher Deborah Cory-Slechta said that: In a study of mice, air pollution also has a larger negative impact on males than on females. In 2015, experimental studies reported the detection of significant episodic (situational) cognitive impairment from impurities in indoor air breathed by test subjects who were not informed about changes in the air quality. Researchers at the
Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher le ...
and SUNY Upstate Medical University and Syracuse University measured the cognitive performance of 24 participants in three different controlled laboratory atmospheres that simulated those found in "conventional" and "green" buildings, as well as
green buildings Green building (also known as green construction or sustainable building) refers to both a structure and the application of processes that are environmentally responsible and resource-efficient throughout a building's life-cycle: from plannin ...
with enhanced ventilation. Performance was evaluated objectively using the widely used Strategic Management Simulation software simulation tool, which is a well-validated assessment test for executive decision-making in an unconstrained situation allowing initiative and improvisation. Significant deficits were observed in the performance scores achieved in increasing concentrations of either
volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s (VOCs) or
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
, while keeping other factors constant. The highest impurity levels reached are not uncommon in some classroom or office environments. Higher PM2.5 and concentrations were shown to be associated with slower response times and reduced accuracy in tests.


Agricultural effects

In India in 2014, it was reported that air pollution by
black carbon Chemically, black carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuel ...
and ground level ozone had reduced crop yields in the most affected areas by almost half in 2011 when compared to 1980 levels. After air pollutants enter the agricultural environment, they not only directly affect agricultural production and quality but also enter agricultural waters and soil.


Economic effects

Air pollution costs the world economy $5 trillion per year as a result of productivity losses and degraded quality of life, according to a joint study by the
World Bank The World Bank is an international financial institution that provides loans and grants to the governments of low- and middle-income countries for the purpose of pursuing capital projects. The World Bank is the collective name for the Interna ...
and the
Institute for Health Metrics and Evaluation The Institute for Health Metrics and Evaluation (IHME) is a research institute working in the area of global health statistics and impact evaluation at the University of Washington in Seattle. The Institute is headed by Christopher J.L. Murray ...
(IHME) at the
University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...
. These productivity losses are caused by deaths due to diseases caused by air pollution. One out of ten deaths in 2013 was caused by diseases associated with air pollution and the problem is getting worse. The problem is even more acute in the
developing world A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...
. "Children under age 5 in lower-income countries are more than 60 times as likely to die from exposure to air pollution as children in high-income countries." The report states that additional economic losses caused by air pollution, including health costs and the adverse effect on agricultural and other productivity were not calculated in the report, and thus the actual costs to the world economy are far higher than $5 trillion.


Other effects

Artificial air pollution may be detectable on Earth from distant vantage points such as other planetary systems via atmospheric SETI – including NO2 pollution levels and with telescopic technology close to today. It may also be possible to detect extraterrestrial civilizations this way.


Historical disasters

The world's worst short-term civilian pollution crisis was the 1984
Bhopal Disaster The Bhopal disaster, also referred to as the Bhopal gas tragedy, was a chemical accident on the night of 2–3 December 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh, India. Considered the world's ...
in India. Leaked industrial vapours from the Union Carbide factory, belonging to Union Carbide, Inc., U.S.A. (later bought by
Dow Chemical Company The Dow Chemical Company, officially Dow Inc., is an American multinational chemical corporation headquartered in Midland, Michigan, United States. The company is among the three largest chemical producers in the world. Dow manufactures plastic ...
), killed at least 3787 people and injured from 150,000 to 600,000. The United Kingdom suffered its worst air pollution event when the 4 December
Great Smog The Great Smog of London, or Great Smog of 1952, was a severe air pollution event that affected London, England, in December 1952. A period of unusually cold weather, combined with an anticyclone and windless conditions, collected airborne poll ...
of 1952 formed over
London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
. In six days more than 4,000 died and more recent estimates put the figure at nearer 12,000. An accidental leak of anthrax spores from a
biological warfare Biological warfare, also known as germ warfare, is the use of biological toxins or infectious agents such as bacteria, viruses, insects, and fungi with the intent to kill, harm or incapacitate humans, animals or plants as an act of war. Bio ...
laboratory in the former
USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...
in 1979 near Sverdlovsk is believed to have caused at least 64 deaths. The worst single incident of air pollution to occur in the US occurred in
Donora, Pennsylvania Donora is a borough in Washington County, Pennsylvania, United States, approximately south of Pittsburgh on the Monongahela River. Donora was incorporated in 1901. It got its name from a combination of William Donner and Nora Mellon, banker ...
, in late October 1948, when 20 people died and over 7,000 were injured.


Reduction and regulation

Pollution prevention seeks to prevent pollution such as air pollution and could include adjustments to industrial and business activities such as designing sustainable manufacturing processes (and the products' designs) and related legal regulations as well as efforts towards renewable energy transitions. Efforts to reduce particulate matter in the air may result in better health. The
9-Euro-Ticket The 9-Euro-Ticket was a German scheme through which passengers could travel for 9 euros per month on local and regional transport in all of Germany. The tickets were valid for June, July, or August 2022. The offer aimed at reducing energy use ...
scheme in Germany which allowed people to buy a monthly pass allowing use on all local and regional transport (trains, trams and busses) for 9
euro The euro ( symbol: €; code: EUR) is the official currency of 19 out of the member states of the European Union (EU). This group of states is known as the eurozone or, officially, the euro area, and includes about 340 million citizens . ...
(€) for one month of unlimited travel saved 1.8 million tons of CO2 emissions during its three month implementation from June to August 2022.


Pollution control

Various pollution control technologies and strategies are available to reduce air pollution.Fensterstock, Ketcham and Walsh, The Relationship of Land Use and Transportation Planning to Air Quality Management, Ed. George Hagevik, May 1972. At its most basic level,
land-use planning Land use planning is the process of regulating the use of land by a central authority. Usually, this is done to promote more desirable social and environmental outcomes as well as a more efficient use of resources. More specifically, the goals ...
is likely to involve zoning and transport infrastructure planning. In most developed countries, land-use planning is an important part of social policy, ensuring that land is used efficiently for the benefit of the wider economy and population, as well as to protect the environment.
Titanium dioxide Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insolubl ...
has been researched for its ability to reduce air pollution.
Ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
light will release free electrons from material, thereby creating free radicals, which break up VOCs and gases. One form is superhydrophilic. Pollution-eating
nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 1 ...
s placed near a busy road were shown to absorb toxic emission from around 20 cars each day.


Energy transition

Since a large share of air pollution is caused by combustion of
fossil fuels A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ...
such as
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...
and
oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
, the reduction of these fuels can reduce air pollution drastically. Most effective is the switch to clean power sources such as
wind power Wind power or wind energy is mostly the use of wind turbines to electricity generation, generate electricity. Wind power is a popular, sustainable energy, sustainable, renewable energy source that has a much smaller Environmental impact of wi ...
,
solar power Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovoltaic e ...
,
hydro power Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a w ...
which do not cause air pollution. Efforts to reduce pollution from mobile sources includes expanding regulation to new sources (such as cruise and transport ships, farm equipment, and small gas-powered equipment such as
string trimmer A string trimmer, also known by the portmanteau strimmer and the trademarks Weedwacker, Weed eater and Whipper Snipper. is a garden tool for cutting grass, small weeds, and groundcover. It uses a whirling monofilament line instead of a blade, ...
s,
chainsaw A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pru ...
s, and
snowmobiles A snowmobile, also known as a Ski-Doo, snowmachine, sled, motor sled, motor sledge, skimobile, or snow scooter, is a motorized vehicle designed for winter travel and recreation on snow. It is designed to be operated on snow and ice and does not ...
), increased
fuel efficiency Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
(such as through the use of hybrid vehicles), conversion to cleaner fuels, and conversion to
electric vehicle An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. It can be powered by a collector system, with electricity from extravehicular sources, or it can be powered autonomously by a battery (sometimes cha ...
s. A very effective means to reduce air pollution is the transition to
renewable energy Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...
. According to a study published in
Energy and Environmental Science ''Energy & Environmental Science'' is a monthly peer-reviewed scientific journal publishing original (primary) research and review articles. The journal covers work of an interdisciplinary nature in the biochemical and biophysical sciences and ch ...
in 2015 the switch to
100% renewable energy 100% renewable energy means getting all energy from renewable resources. The endeavor to use 100% renewable energy for electricity, heating, cooling and transport is motivated by climate change, pollution and other environmental issues, ...
in the United States would eliminate about 62,000 premature mortalities per year and about 42,000 in 2050, if no biomass were used. This would save about $600 billion in
health costs Health economics is a branch of economics concerned with issues related to efficiency, effectiveness, value and behavior in the production and consumption of health and healthcare. Health economics is important in determining how to impro ...
a year due to reduced air pollution in 2050, or about 3.6% of the 2014 U.S. gross domestic product. Air quality improvement is a near-term benefit among the many societal benefits from
climate change mitigation Climate change mitigation is action to limit climate change by reducing Greenhouse gas emissions, emissions of greenhouse gases or Carbon sink, removing those gases from the atmosphere. The recent rise in global average temperature is mostly caus ...
.


Alternatives to pollution

There are now practical alternatives to the principal causes of air pollution: * Strategic substitution of air pollution sources in transport with lower-emission or, during the lifecycle, emission-free forms of
public transport Public transport (also known as public transportation, public transit, mass transit, or simply transit) is a system of transport for passengers by group travel systems available for use by the general public unlike private transport, typical ...
and bicycle use and infrastructure (as well as with remote work, reductions of work, relocations, and localizations) **
Phase-out of fossil fuel vehicles Phase-out of fossil fuel vehicles means stopping selling and using vehicles which are powered by fossil fuels, such as gasoline (petrol), diesel, kerosene and fuel oil: it is one of the three most important parts of the general fossil fuel phase ...
is a critical component of a shift to
sustainable transport Sustainable transport refers to ways of transportation that are sustainable in terms of their social and environmental impacts. Components for evaluating sustainability include the particular vehicles used for road, water or air transport; th ...
; however, similar infrastructure and design decisions like
electric vehicle An electric vehicle (EV) is a vehicle that uses one or more electric motors for propulsion. It can be powered by a collector system, with electricity from extravehicular sources, or it can be powered autonomously by a battery (sometimes cha ...
s may be associated with similar pollution for production as well as mining and resource exploitation for large numbers of needed batteries as well as the energy for their recharging * Areas downwind (over 20 miles) of major airports have more than double ''total particulate emissions in air'' than other areas, even when factoring in areas with frequent ship calls, and heavy freeway and city traffic like Los Angeles.
Aviation biofuel An aviation biofuel or bio-jet fuel Note: About">Investable Universe>About' or bio-aviation fuel (BAF) is a biofuel used to power aircraft and is said to be a sustainable aviation fuel (SAF). The International Air Transport Association (IATA) co ...
mixed in with jetfuel at a 50/50 ratio can reduce jet derived cruise altitude particulate emissions by 50–70%, according to a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
led 2017 study (however, this should imply ground level benefits to urban air pollution as well). * Ship propulsion and idling can be switched to much cleaner fuels like natural gas. (Ideally a
renewable source Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, the movement of water, and geothermal heat. Although most renewable energy ...
but not practical yet) * Combustion of fossil fuels for space heating can be replaced by using
ground source heat pumps A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that uses a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through ...
and
seasonal thermal energy storage Seasonal thermal energy storage (STES), also known as inter-seasonal thermal energy storage, is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever nee ...
. * Electricity generated from the combustion of fossil fuels can be replaced by nuclear and renewable energy. Heating and home stoves, which contribute significantly to regional air pollution, can be replaced with a much cleaner fossil fuel, such as natural gas, or, preferably, renewables, in poor countries. * Motor vehicles driven by fossil fuels, a key factor in urban air pollution, can be replaced by electric vehicles. Though lithium supply and cost is a limitation, there are alternatives. Herding more people into clean public transit such as electric trains can also help. Nevertheless, even in emission-free electric vehicles, rubber tires produce significant amounts of air pollution themselves, ranking as 13th worst pollutant in Los Angeles. *Reducing travel in vehicles can curb pollution. After Stockholm reduced vehicle traffic in the central city with a congestion tax, nitrogen dioxide and PM10 pollution declined, as did acute pediatric asthma attacks. * Biodigesters can be utilized in poor nations where
slash and burn Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area. The downed veget ...
is prevalent, turning a useless commodity into a source of income. The plants can be gathered and sold to a central authority that will break them down in a large modern biodigester, producing much needed energy to use. * Induced humidity and ventilation both can greatly dampen air pollution in enclosed spaces, which was found to be relatively high inside subway lines due to braking and friction and relatively less ironically inside transit buses than lower sitting passenger automobiles or subways.


Control devices

The following items are commonly used as pollution control devices in industry and transportation. They can either destroy
contaminant Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination Wi ...
s or remove them from an exhaust stream before it is emitted into the atmosphere. * Particulate control ** Mechanical collectors ( dust cyclones, multicyclones) **
Electrostatic precipitator An electrostatic precipitator (ESP) is a filterless device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit. In con ...
s: An electrostatic precipitator (ESP), or electrostatic air cleaner, is a particulate collection device that removes particles from a flowing gas (such as air), using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulates such as dust and smoke from the air stream. ** Baghouses: Designed to handle heavy dust loads, a dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system (distinguished from air cleaners which utilize disposable filters to remove the dust). ** Particulate scrubbers: A wet scrubber is a form of pollution control technology. The term describes a variety of devices that use pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants. * Scrubbers **
Baffle spray scrubber Baffle spray scrubbers are a technology for air pollution control. They are very similar to spray towers in design and operation. However, in addition to using the energy provided by the spray nozzles, baffles are added to allow the gas stream ...
**
Cyclonic spray scrubber Cyclonic spray scrubbers are an air pollution control technology. They use the features of both the dry cyclone and the spray chamber to remove pollutants from gas streams. Generally, the inlet gas enters the chamber tangentially, swirls throug ...
**
Ejector venturi scrubber An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic ...
**
Mechanically aided scrubber Mechanically aided scrubbers are a form of pollution control technology. This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers. In addition to using liquid sprays or the exhaust strea ...
**
Spray tower A spray tower (or spray column or spray chamber) is gas-liquid contactor used to achieve mass and heat transfer between a continuous gas phase (that can contain dispersed solid particles) and a dispersed liquid phase. It consists of an empty c ...
**
Wet scrubber The term wet scrubber describes a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the ...
* control **
LO-NOx burner A LO burner is a type of burner that is typically used in utility boilers to produce steam and electricity. Background The first discovery Around 1986 John Joyce (of Bowin Cars fame), an influential Australian inventor, first learned about oxi ...
s **
Selective catalytic reduction Selective catalytic reduction (SCR) is a means of converting nitrogen oxides, also referred to as with the aid of a catalyst into diatomic nitrogen (), and water (). A reductant, typically anhydrous ammonia (), aqueous ammonia (), or a urea () ...
(SCR) **
Selective non-catalytic reduction Selective non-catalytic reduction (SNCR) is a method to lessen nitrogen oxide emissions in conventional power plants that burn biomass, incineration, waste and coal. The process involves injecting either ammonia or urea into the firebox of the boil ...
(SNCR) ** NOx scrubbers **
Exhaust gas recirculation In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide () emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust ...
**
Catalytic converter A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
(also for VOC control) * VOC abatement ** Adsorption systems, using activated carbon, such as
Fluidized Bed Concentrator A fluidized bed concentrator (FBC) is an industrial process for the treatment of exhaust air. The system uses a bed of activated carbon beads to adsorb volatile organic compounds (VOCs) from the exhaust gas. Evolving from the previous fixed-bed an ...
** Flares **
Thermal oxidizer A thermal oxidizer (also known as thermal oxidiser, or thermal incinerator) is a process unit for air pollution control in many chemical plants that decomposes hazardous gases at a high temperature and releases them into the atmosphere. Principl ...
s **
Catalytic converter A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
s **
Biofilter Biofiltration is a pollution control technique using a bioreactor containing living material to capture and biologically degrade pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and ...
s ** Absorption (scrubbing) **
Cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
condensers __NOTOC__ Condenser may refer to: Heat transfer * Condenser (heat transfer), a device or unit used to condense vapor into liquid. Specific types include: ** HVAC air coils ** Condenser (laboratory), a range of laboratory glassware used to remove ...
** Vapor recovery systems *
Acid gas Acid gas is a particular typology of natural gas or any other gas mixture containing significant quantities of hydrogen sulfide (H2S), carbon dioxide (CO2), or similar acidic gases. A gas is determined to be acidic or not after it is mixed with w ...
/ SO2 control **
Wet scrubber The term wet scrubber describes a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the ...
s ** Dry scrubbers ** Flue-gas desulfurization * Mercury control ** Sorbent injection technology ** Electro-catalytic oxidation (ECO) ** K-Fuel *
Dioxin Dioxin may refer to: * 1,2-Dioxin or 1,4-Dioxin, two unsaturated heterocyclic 6-membered rings where two carbon atoms have been replaced by oxygen atoms, giving the molecular formula C4H4O2 *Dibenzo-1,4-dioxin, the parent compound also known as ...
and
furan Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly ...
control * Miscellaneous associated equipment ** Source capturing systems **
Continuous emissions monitoring system Continuous emission monitoring systems (CEMS) are used as a tool to monitor the effluent gas streams resulting from combustion in industrial processes. CEMS can measure flue gas for oxygen, carbon monoxide and carbon dioxide to provide informati ...
s (CEMS)


Monitoring

Spatiotemporal monitoring of air quality may be necessary for improving air quality, and thereby the health and safety of the public, and assessing impacts of interventions. Such monitoring is done to different extents with different regulatory requirements with discrepant regional coverage by a variety of organizations and governance entities such as using a variety of technologies for use of the data and sensing such mobile IoT sensors, satellites, and monitoring stations. Some websites attempt to map air pollution levels using available data.


Air quality modeling

Numerical models either on a global scale using tools such as GCMs (
general circulation model A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic ter ...
s coupled with a pollution module) or CTMs (
Chemical transport model A chemical transport model (CTM) is a type of computer numerical model which typically simulates atmospheric chemistry and may give air pollution forecasting. Chemical transport models and general circulation models While related general circ ...
) can be used to simulate the levels of different pollutants in the atmosphere. These tools can have several types (
Atmospheric model An atmospheric model is a mathematical model constructed around the full set of primitive dynamical equations which govern atmospheric motions. It can supplement these equations with parameterizations for turbulent diffusion, radiation, mois ...
) and different uses. These models can be used in forecast mode which can help policy makers to decide on appropriate actions when an air pollution episode is detected. They can also be used for climate modeling including evolution of air quality in the future, for example the IPCC (
Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to advance scientific knowledge about climate change caused by human activities. The World Meteorological Organization (WMO) a ...
) provides climate simulations including air quality assessments in their reports (latest report accessible through thei
site
.


Regulations

In general, there are two types of air quality standards. The first class of standards (such as the U.S. National Ambient Air Quality Standards and E.U. Air Quality Directive) set maximum atmospheric concentrations for specific pollutants. Environmental agencies enact regulations which are intended to result in attainment of these target levels. The second class (such as the North American air quality index) take the form of a scale with various thresholds, which is used to communicate to the public the relative risk of outdoor activity. The scale may or may not distinguish between different pollutants.


Canada

In
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, air pollution and associated health risks are measured with the Air Quality Health Index (AQHI). It is a health protection tool used to make decisions to reduce short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution. The AQHI is a federal program jointly coordinated by Health Canada and Environment Canada. However, the AQHI program would not be possible without the commitment and support of the provinces, municipalities and NGOs. From air quality monitoring to health risk communication and community engagement, local partners are responsible for the vast majority of work related to AQHI implementation. The AQHI provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality. Occasionally, when the amount of air pollution is abnormally high, the number may exceed 10. The AQHI provides a local air quality current value as well as a local air quality maximums forecast for today, tonight and tomorrow and provides associated health advice. As it is now known that even low levels of air pollution can trigger discomfort for the sensitive population, the index has been developed as a continuum: The higher the number, the greater the health risk and need to take precautions. The index describes the level of health risk associated with this number as 'low', 'moderate', 'high' or 'very high', and suggests steps that can be taken to reduce exposure. The measurement is based on the observed relationship of nitrogen dioxide (NO2), ground-level ozone (O3) and particulates (PM2.5) with mortality, from an analysis of several Canadian cities. Significantly, all three of these pollutants can pose health risks, even at low levels of exposure, especially among those with pre-existing health problems. When developing the AQHI, Health Canada's original analysis of health effects included five major air pollutants: particulates,
ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
, and
nitrogen dioxide Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...
(NO2), as well as
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
(SO2), and
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
(CO). The latter two pollutants provided little information in predicting health effects and were removed from the AQHI formulation. The AQHI does not measure the effects of odour,
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
, dust, heat or humidity.


Germany

TA Luft Germany has an air pollution control regulation titled "Technical Instructions on Air Quality Control" (''Technische Anleitung zur Reinhaltung der Luft'') and commonly referred to as the ''TA Luft''. The first version of the ''TA Luft'' was establ ...
is the German air quality regulation.


Governing urban air pollution

In Europe, Council Directive 96/62/EC on ambient air quality assessment and management provides a common strategy against which member states can "set objectives for ambient air quality in order to avoid, prevent or reduce harmful effects on human health and the environment ... and improve air quality where it is unsatisfactory". On 25 July 2008 in the case ''Dieter Janecek v Freistaat Bayern'', the
European Court of Justice The European Court of Justice (ECJ, french: Cour de Justice européenne), formally just the Court of Justice, is the supreme court of the European Union in matters of European Union law. As a part of the Court of Justice of the European Un ...
ruled that under this directive citizens have the right to require national authorities to implement a short term action plan that aims to maintain or achieve compliance to air quality limit values. This important
case law Case law, also used interchangeably with common law, is law that is based on precedents, that is the judicial decisions from previous cases, rather than law based on constitutions, statutes, or regulations. Case law uses the detailed facts of a l ...
appears to confirm the role of the EC as centralised regulator to European nation-states as regards air pollution control. It places a
supranational Supranational or supra-national may refer to: * Supranational union, a type of multinational political union * Supranational law, a form of international law * Supranational legislature, a form of international legislature * Supranational curre ...
legal obligation on the UK to protect its citizens from dangerous levels of air pollution, furthermore superseding national interests with those of the citizen. In 2010, the
European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body o ...
(EC) threatened the UK with legal action against the successive breaching of
PM10 Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The te ...
limit values. The UK government has identified that if fines are imposed, they could cost the nation upwards of £300 million per year. In March 2011, the
Greater London Built-up Area The Greater London Built-up Area, or Greater London Urban Area, is a conurbation in south-east England that constitutes the continuous urban sprawl of London, and includes surrounding adjacent urban towns as defined by the Office for National Sta ...
remained the only UK region in breach of the EC's limit values, and was given three months to implement an emergency action plan aimed at meeting the EU Air Quality Directive. The City of London has dangerous levels of PM10 concentrations, estimated to cause 3000 deaths per year within the city. As well as the threat of EU fines, in 2010 it was threatened with legal action for scrapping the western congestion charge zone, which is claimed to have led to an increase in air pollution levels. In response to these charges,
Boris Johnson Alexander Boris de Pfeffel Johnson (; born 19 June 1964) is a British politician, writer and journalist who served as Prime Minister of the United Kingdom and Leader of the Conservative Party from 2019 to 2022. He previously served as F ...
,
Mayor of London The mayor of London is the chief executive of the Greater London Authority. The role was created in 2000 after the 1998 Greater London Authority referendum, Greater London devolution referendum in 1998, and was the first Directly elected may ...
, has criticised the current need for European cities to communicate with Europe through their nation state's
central government A central government is the government that is a controlling power over a unitary state. Another distinct but sovereign political entity is a federal government, which may have distinct powers at various levels of government, authorized or dele ...
, arguing that in future "A great city like London" should be permitted to bypass its government and deal directly with the European Commission regarding its air quality action plan. This can be interpreted as recognition that cities can transcend the traditional national government organisational hierarchy and develop solutions to air pollution using global governance networks, for example through transnational relations. Transnational relations include but are not exclusive to national governments and intergovernmental organisations, allowing sub-national actors including cities and
regions In geography, regions, otherwise referred to as zones, lands or territories, are areas that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and t ...
to partake in air pollution control as independent actors. Global city partnerships can be built into networks, for example the
C40 Cities Climate Leadership Group – The C40 Cities Climate Leadership Group is a group of 97 cities around the world that represents one twelfth of the world's population and one quarter of the global economy. Created and led by cities, C40 is focused on fighting climate change a ...
, of which London is a member. The C40 is a public 'non-state' network of the world's leading cities that aims to curb their greenhouse emissions. The C40 has been identified as 'governance from the middle' and is an alternative to intergovernmental policy. It has the potential to improve urban air quality as participating cities "exchange information, learn from best practices and consequently mitigate carbon dioxide emissions independently from national government decisions". A criticism of the C40 network is that its exclusive nature limits influence to participating cities and risks drawing resources away from less powerful city and regional actors.


Hotspots

Air pollution hotspots are areas where air pollution emissions expose individuals to increased negative health effects. They are particularly common in highly populated, urban areas, where there may be a combination of stationary sources (e.g. industrial facilities) and mobile sources (e.g. cars and trucks) of pollution. Emissions from these sources can cause
respiratory disease Respiratory diseases, or lung diseases, are pathology, pathological conditions affecting the organs and tissues that make gas exchange difficult in Breathing, air-breathing animals. They include conditions of the respiratory tract including the t ...
, childhood
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
,
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
, and other health problems. Fine particulate matter such as diesel soot, which contributes to more than 3.2 million premature deaths around the world each year, is a significant problem. It is very small and can lodge itself within the lungs and enter the bloodstream. Diesel soot is concentrated in densely populated areas, and one in six people in the U.S. live near a diesel pollution hot spot. While air pollution hotspots affect a variety of populations, some groups are more likely to be located in hotspots. Previous studies have shown disparities in exposure to pollution by race and/or income. Hazardous land uses (toxic storage and disposal facilities, manufacturing facilities, major roadways) tend to be located where property values and income levels are low. Low
socioeconomic Socioeconomics (also known as social economics) is the social science that studies how economic activity affects and is shaped by social processes. In general it analyzes how modern societies progress, stagnate, or regress because of their l ...
status can be a proxy for other kinds of
social vulnerability In its broadest sense, social vulnerability is one dimension of vulnerability to multiple stressors and shocks, including abuse, social exclusion and natural hazards. Social vulnerability refers to the inability of people, organizations, and socie ...
, including race, a lack of ability to influence regulation and a lack of ability to move to neighborhoods with less environmental pollution. These communities bear a disproportionate burden of environmental pollution and are more likely to face health risks such as cancer or asthma. Studies show that patterns in race and income disparities not only indicate a higher exposure to pollution but also higher risk of adverse health outcomes. Communities characterized by low
socioeconomic Socioeconomics (also known as social economics) is the social science that studies how economic activity affects and is shaped by social processes. In general it analyzes how modern societies progress, stagnate, or regress because of their l ...
status and racial minorities can be more vulnerable to cumulative adverse health impacts resulting from elevated exposure to pollutants than more privileged communities. Blacks and Latinos generally face more pollution than whites and Asians, and low-income communities bear a higher burden of risk than affluent ones. Racial discrepancies are particularly distinct in
suburb A suburb (more broadly suburban area) is an area within a metropolitan area, which may include commercial and mixed-use, that is primarily a residential area. A suburb can exist either as part of a larger city/urban area or as a separate ...
an areas of the
Southern United States The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, or simply the South) is a geographic and cultural region of the United States of America. It is between the Atlantic Ocean ...
and metropolitan areas of the
Midwestern The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...
and
Western United States The Western United States (also called the American West, the Far West, and the West) is the region comprising the westernmost states of the United States. As American settlement in the U.S. expanded westward, the meaning of the term ''the Wes ...
. Residents in public housing, who are generally low-income and cannot move to healthier neighborhoods, are highly affected by nearby refineries and chemical plants.


Cities

Air pollution is usually concentrated in densely populated metropolitan areas, especially in developing countries where cities are experiencing rapid growth and environmental regulations are relatively lax or nonexistent. Urbanization leads to a rapid rise in premature mortality due to anthropogenic air pollution in fast-growing tropical cities. However, even populated areas in developed countries attain unhealthy levels of pollution, with
Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...
and
Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus (legendary) , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg , map_caption ...
being two examples. Between 2002 and 2011 the incidence of lung cancer in
Beijing } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...
near doubled. While smoking remains the leading cause of lung cancer in China, the number of smokers is falling while lung cancer rates are rising .
Tehran Tehran (; fa, تهران ) is the largest city in Tehran Province and the capital of Iran. With a population of around 9 million in the city and around 16 million in the larger metropolitan area of Greater Tehran, Tehran is the most popul ...
was declared the most polluted city in the world on May 24, 2022.


Projections

According to a projection, by 2030 half of the world's pollution emissions could be generated by Africa. Potential contributors to such an outcome include increased burning activities (such as the burning of open waste), traffic, agri-food and chemical industries, sand dust from the Sahara, and overall
population growth Population growth is the increase in the number of people in a population or dispersed group. Actual global human population growth amounts to around 83 million annually, or 1.1% per year. The global population has grown from 1 billion in 1800 to ...
. According to OECD, by 2050 outdoor air pollution (particulate matter and ground-level ozone) is projected to become the top cause of environmentally related deaths worldwide.


See also

*
Air pollutant concentrations Air pollutant concentrations, as measured or as calculated by air pollution dispersion modeling, must often be converted or corrected to be expressed as required by the regulations issued by various governmental agencies. Regulations that define a ...
*
Air pollution measurement Air pollution measurement is the process of collecting and measuring the components of air pollution, notably gases and particulates. The earliest devices used to measure pollution include rain gauges (in studies of acid rain), Ringelmann charts ...
*
Air stagnation Air stagnation is a phenomenon which occurs when an air mass remains over an area for an extended period. Stagnation events strongly correlates with poor air quality. Due to light winds and lack of precipitation, pollutants cannot be cleared from t ...
*
ASEAN Agreement on Transboundary Haze Pollution The ASEAN Agreement on Transboundary Haze Pollution is a legally binding environmental agreement signed in 2002 by the member states of the Association of Southeast Asian Nations to reduce haze pollution in Southeast Asia. The Agreement ...
*
Asian brown cloud The Indian Ocean brown cloud or Asian brown cloud is a layer of air pollution that recurrently covers parts of South Asia, namely the northern Indian Ocean, India, and Pakistan. Viewed from satellite photos, the cloud appears as a giant brown st ...
*
Atmospheric chemistry Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteoro ...
*
Beehive burner A wood waste burner, known as a teepee burner or wigwam burner in the United States and a beehive burner in Canada, is a free-standing conical steel structure usually ranging from 30 to 60 feet in height. They are named for their resemblance to ...
*
BenMAP The Environmental Benefits Mapping and Analysis Program (BenMAP) is an open source, Windows-based computer program created by the U.S. Environmental Protection Agency that estimates the health benefits from improvements in air quality. State, loc ...
*
Best Available Control Technology A State Implementation Plan (SIP) is a United States state plan for complying with the federal Clean Air Act, administered by the Environmental Protection Agency (EPA). The SIP, developed by a state agency and approved by EPA, consists of narrat ...
* Critical load *
Emission standard Emission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over ...
*
Emissions & Generation Resource Integrated Database The Emissions & Generation Resource Integrated Database (eGRID) is a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States. eGRID is issued by the U.S. Environmental Protecti ...
*
Environmental agreement An international environmental agreement or sometimes environmental protocol, is a type of treaty binding in international law, allowing them to reach an environmental goal. In other words, it is "an intergovernmental document intended as legall ...
*
Environmental racism Environmental racism or ecological apartheid is a form of institutional racism leading to landfills, incinerators, and hazardous waste disposal being disproportionally placed in communities of colour. Internationally, it is also associated with ...
*
Flue-gas emissions from fossil-fuel combustion Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced ...
*
Global Atmosphere Watch The Global Atmosphere Watch (GAW) is a worldwide system established by the World Meteorological Organizationa United Nations agencyto monitor trends in the Earth's atmosphere. It arose out of concerns for the state of the atmosphere in the 1960s. ...
*
Global dimming Global dimming is the reduction in the amount of global direct irradiance at the Earth's surface that has been observed since systematic measurements began in the 1950s. The effect varies by location, but worldwide it has been estimated to be of ...
*
Great Smog The Great Smog of London, or Great Smog of 1952, was a severe air pollution event that affected London, England, in December 1952. A period of unusually cold weather, combined with an anticyclone and windless conditions, collected airborne poll ...
of London *
Haze Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classificati ...
* Health Effects Institute (HEI) *
Indicator value Indicator value is a term that has been used in the ecology of plants for two different indices. The older usage of the term refers to Ellenberg's indicator values from 1974, which are based on a simple ordinal classification of plants according t ...
*
Intake fraction Intake fraction is a measurement of pollution and it can be used in the determination of the environmental health impact of a pollutant source. Intake fraction is the ratio of the mass of a pollutant inhaled or ingested to the mass of the pollutant ...
*
International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...
* International Day of Clean Air for Blue Skies *
Kyoto Protocol The Kyoto Protocol was an international treaty which extended the 1992 United Nations Framework Convention on Climate Change (UNFCCC) that commits state parties to reduce greenhouse gas emissions, based on the scientific consensus that (part ...
* Light water reactor sustainability * List of smogs by death toll *
Lowest Achievable Emissions Rate A State Implementation Plan (SIP) is a United States state plan for complying with the federal Clean Air Act, administered by the Environmental Protection Agency (EPA). The SIP, developed by a state agency and approved by EPA, consists of narrativ ...
*
NASA Clean Air Study __NOTOC__ The NASA Clean Air Study was a project led by the National Aeronautics and Space Administration (NASA) in association with the Associated Landscape Contractors of America (ALCA) in 1989, to research ways to clean the air in sealed envir ...
*
Non-exhaust emissions Non-exhaust emissions come from wearing down motor vehicle brake pads, tires, roads themselves, and unsettling of particles on the road. This particulate matter is made up of micrometre-sized particles and causes negative health effects, includi ...
* Organic molecular tracers *
Particulate matter sampler A particulate matter sampler is an instrument for measuring the properties (such as mass concentration or chemical composition) of particulates in the ambient air. Types Two different types of particulate matter samplers exist that measure pa ...
*
Polluter pays principle In environmental law, the polluter pays principle is enacted to make the party responsible for producing pollution responsible for paying for the damage done to the natural environment. It is regarded as a regional custom because of the strong supp ...
*
Regulation of greenhouse gases under the Clean Air Act The, United States Environmental Protection Agency (EPA) began regulating greenhouse gases (GHGs) under the Clean Air Act ("CAA" or "Act") from mobile and stationary sources of air pollution for the first time on January 2, 2011. Standards for ...
* Rubber pollution *
Tire fire Tire fires are events that involve the combustion of large quantities of tires, usually waste tires, typically in locations where they are stored, dumped, or processed. They exist in two forms: as fast-burning events, leading to almost immediate ...


References


Further reading

* Brimblecombe, Peter. ''The Big Smoke: A History of Air Pollution in London Since Medieval Times'' (Methuen, 1987) * Brimblecombe, Peter. "History of air pollution." in ''Composition, Chemistry and Climate of the Atmosphere'' (Van Nostrand Reinhold (1995): 1–18 * * Cherni, Judith A. ''Economic Growth versus the Environment: The Politics of Wealth, Health and Air Pollution'' (2002
online
* Corton, Christine L. ''London Fog: The Biography'' (2015) * Currie, Donya. "WHO: Air Pollution a Continuing Health Threat in World's Cities," ''The Nation's Health'' (February 2012) 42#
online
* Dewey, Scott Hamilton. ''Don't Breathe the Air: Air Pollution and US Environmental Politics, 1945–1970'' (Texas A & M University Press, 2000) * Gonzalez, George A. ''The politics of air pollution: Urban growth, ecological modernization, and symbolic inclusion'' (SUNY Press, 2012) * * Grinder, Robert Dale. "The Battle for Clean Air: The Smoke Problem in Post-Civil War America" in Martin V. Melosi, ed., ''Pollution & Reform in American Cities, 1870–1930'' (1980), pp. 83–103. * Mingle, Jonathan, "Our Lethal Air" eview of Gary Fuller, ''The Invisible Killer...''; Beth Gardiner, ''Choked...''; Tim Smedley, ''Clearing the Air...''; U.S. Environmental Protection Agency, ''Integrated Science Assessment for Particulate Matter (External Review Draft, 2018)''; and Chartered Clean Air Scientific Advisory Committee, ''Letter to EPA Administrator on the EPA's Integrated Science Assessment for Particulate Matter, 11 April 2019''], ''
The New York Review of Books ''The New York Review of Books'' (or ''NYREV'' or ''NYRB'') is a semi-monthly magazine with articles on literature, culture, economics, science and current affairs. Published in New York City, it is inspired by the idea that the discussion of i ...
'', vol. LXVI, no. 14 (26 September 2019), pp. 64–66, 68. "Today, 91 percent of people worldwide live in areas where air pollution levels exceed the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
's recommended limits. ... ere is no safe level of exposure to fine particulate matter. ... Most of these fine particles are a by-product of ... burning ...
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...
,
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
,
diesel Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...
,
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
,
trash Trash may refer to: Garbage * Garbage, unwanted or undesired waste material ** Litter, material discarded in inappropriate places ** Municipal solid waste, unwanted or undesired waste material generated in a municipal environment Arts, enter ...
 ... These particles can get past the defenses of our
upper airways The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose t ...
to penetrate deep into our
lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s and reach the
alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...
 ... From there, they cross into the
bloodstream The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and spread throughout the body. They can travel through the
nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes th ...
, up the olfactory nerve, and lodge ... in the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
. They can form deposits on the lining of
arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pu ...
, constricting
blood vessels The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
and raising the likelihood of ...
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
s and
heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which may tr ...
s. ey exacerbate respiratory illnesses like
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
and
chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce ...
 ... There's ... evidence linking air pollution exposure to an increased risk of Alzheimer's and other forms of
dementia Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
." (p. 64.) * Mosley, Stephen. The chimney of the world: a history of smoke pollution in Victorian and Edwardian Manchester. Routledge, 2013. * Schreurs, Miranda A. ''Environmental Politics in Japan, Germany, and the United States'' (Cambridge University Press, 2002
online
* Thorsheim, Peter. ''Inventing Pollution: Coal, Smoke, and Culture in Britain since 1800'' (2009)


External links


Air Pollution: Everything You Need to Know
Guide by the Natural Resources Defense Council (NRDC)
Global real-time air quality index map

Air Quality Index (AQI) Basics

AQI Calculator
AQI to Concentration and Concentration to AQI for five pollutants
International Conference on Urban Air Quality
.
UNEP Urban environmental planning




from the
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...

World Health Organization Fact Sheet on Air quality and health

Centre for Research on Energy and Clean Air

The Mortality Effects of Long-Term Exposure to Particulate Air Pollution in the United Kingdom
UK Committee on the Medical Effects of Air Pollution, 2010.
Ground Level Ozone Pollution
at
EPA The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
.gov {{DEFAULTSORT:Air Pollution Articles containing video clips Climate forcing Pollution