Volatile organic compounds (VOCs) are
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
s that have a high
vapour pressure
Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phase ...
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 trait known as
volatility.
VOCs are responsible for the odor of scents and
perfume
Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...
s as well as
pollutant
A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like o ...
s. VOCs play an important role in communication between animals and plants, e.g. attractants for pollinators, protection from predation, and even inter-plant interactions. Some VOCs are dangerous to human health or cause harm to the
environment.
Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Most VOCs are not acutely
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 subs ...
, but may have long-term chronic health effects.
Definitions
Diverse definitions of the term VOC are in use.
Canada
Health Canada classifies VOCs as organic compounds that have boiling points roughly in the range of . The emphasis is placed on commonly encountered VOCs that would have an effect on air quality.
European Union
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 de ...
defines a VOC as "any organic compound as well as the fraction of
creosote
Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics.
Some creosote types were ...
, having at 293.15 K a vapour pressure of 0,01 kPa or more, or having a corresponding volatility under the particular conditions of use;". The VOC Solvents Emissions Directive was the main policy instrument for the reduction of industrial emissions of volatile organic compounds (VOCs) in the European Union. It covers a wide range of solvent-using activities, e.g. printing, surface cleaning, vehicle coating, dry cleaning and manufacture of footwear and pharmaceutical products. The VOC Solvents Emissions Directive requires installations in which such activities are applied to comply either with the emission limit values set out in the Directive or with the requirements of the so-called reduction scheme. Article 13 of The Paints Directive, approved in 2004, amended the original VOC Solvents Emissions Directive and limits the use of organic solvents in decorative paints and varnishes and in vehicle finishing products. The Paints Directive sets out maximum VOC content limit values for paints and varnishes in certain applications. The Solvents Emissions Directive was replaced by the
Industrial Emissions Directive
The Industrial Emissions Directive (Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control)) is a European Union directive which commits Europea ...
from 2013.
China
The
People's Republic of China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
defines a VOC as those compounds that have "originated from automobiles, industrial production and civilian use, burning of all types of fuels, storage and transportation of oils, fitment finish, coating for furniture and machines, cooking oil fume and fine particles (PM 2.5)", and similar sources. The Three-Year Action Plan for Winning the Blue Sky Defence War released by the State Council in July 2018 creates an action plan to reduce 2015 VOC emissions 10% by 2020.
India
The
Central Pollution Control Board
The Central Pollution Control Board (CPCB) of India is a statutory organization under the Ministry of Environment, Forest and Climate Change (Mo.E.F.C.C.). It was established in 1974 under the Water (Prevention and Control of pollution) Act, 1 ...
of India released the
Air (Prevention and Control of Pollution) Act in 1981, amended in 1987, to address concerns about
air pollution in India
Air pollution in India is a serious environmental issue. Of the 30 most polluted cities in the world, 21 were in India in 2019. As per a study based on 2016 data, at least 140 million people in India breathe air that is 10 times or more over the ...
. While the document does not differentiate between VOCs and other air pollutants, the CPCB monitors "oxides of nitrogen (NO
x), sulphur dioxide (SO
2), fine particulate matter (PM10) and suspended particulate matter (SPM)".
United States
![Thermal-oxidizer-rto](https://upload.wikimedia.org/wikipedia/commons/e/ea/Thermal-oxidizer-rto.jpg)
The definitions of VOCs used for control of precursors of
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 inten ...
used by the
U.S. Environmental Protection Agency
The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...
(EPA) and state agencies in the US with independent outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process. Prominent is the VOC regulation issued by the
South Coast Air Quality Management District
The South Coast Air Quality Management District, also using the acronym South Coast (AQMD), formed in 1976, is the air pollution agency responsible for regulating stationary sources of air pollution in the South Coast Air Basin and the Coachell ...
in California and by the
California Air Resources Board
The California Air Resources Board (CARB or ARB) is the "clean air agency" of the government of California. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Moto ...
(CARB). However, this specific use of the term VOCs can be misleading, especially when applied to
indoor air quality
Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduce ...
because many chemicals that are not regulated as outdoor air pollution can still be important for indoor air pollution.
Following a public hearing in September 1995, California's CARB uses the term "reactive organic gases" (ROG) to measure organic gases. The CARB revised the definition of "Volatile Organic Compounds" used in their consumer products regulations, based on the committee's findings.
In addition to
drinking water
Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
, VOCs are regulated in pollutant discharges to surface waters (both directly and via sewage treatment plants) as hazardous waste, but not in non-industrial indoor air.
The
Occupational Safety and Health Administration
The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) regulates VOC exposure in the workplace. Volatile organic compounds that are classified as
hazardous materials are regulated by the
Pipeline and Hazardous Materials Safety Administration
The Pipeline and Hazardous Materials Safety Administration (PHMSA) is a United States Department of Transportation agency created in 2004, responsible for developing and enforcing regulations for the safe, reliable, and environmentally sound oper ...
while being transported.
Biologically generated VOCs
File:Limonene-2D-skeletal.svg, Limonene
Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the oil of citrus fruit peels. The -isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring a ...
, a common biogenic VOC, is emitted into the atmosphere primarily by trees which grow in coniferous forest
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All exta ...
s.
Most VOCs in earth's atmosphere are biogenic, largely emitted by plants.
[
Biogenic volatile organic compounds (BVOCs) encompass VOCs emitted by plants, animals, or microorganisms, and while extremely diverse, are most commonly ]terpenoid
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes" ...
s, alcohols, and carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
s (methane and carbon monoxide are generally not considered). Not counting 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 Ea ...
, biological sources emit an estimated 760 teragrams of carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
per year in the form of VOCs. The majority of VOCs are produced by plants, the main compound being isoprene. Small amounts of VOCs are produced by animals and microbes. Many VOCs are considered secondary metabolites
Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fungi, animals, or plants, which are not directly involved in the nor ...
, which often help organisms in defense, such as plant defense against herbivory
Plant defense against herbivory or host-plant resistance (HPR) describes a range of adaptations evolved by plants which improve their survival and reproduction by reducing the impact of herbivores. Plants can sense being touched, and they can ...
. The strong odor emitted by many plants consists of green leaf volatiles, a subset of VOCs. Although intended for nearby organisms to detect and respond to, these volatiles can be detected and communicated through wireless electronic transmission, by embedding nanosensors and infrared transmitters into the plant materials themselves.
Emissions are affected by a variety of factors, such as temperature, which determines rates of volatilization and growth, and sunlight, which determines rates of biosynthesis. Emission occurs almost exclusively from the leaves, the stomata in particular. VOCs emitted by terrestrial forests are often oxidized by hydroxyl radicals in the atmosphere; in the absence of NOx pollutants, VOC photochemistry recycles hydroxyl radicals to create a sustainable biosphere-atmosphere balance. Due to recent climate change developments, such as warming and greater UV radiation, BVOC emissions from plants are generally predicted to increase, thus upsetting the biosphere-atmosphere interaction and damaging major ecosystems. A major class of VOCs is the terpene
Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ...
class of compounds, such as myrcene
Myrcene, or β-myrcene, is a monoterpene. A colorless oil, it occurs widely in essential oils. It is produced mainly semi-synthetically from '' Myrcia'', from which it gets its name. It is an intermediate in the production of several fragrances. ...
. Providing a sense of scale, a forest 62,000 km2 in area, the size of the US state of Pennsylvania
Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
, is estimated to emit 3,400,000 kilograms of terpenes on a typical August day during the growing season. Researchers investigating mechanisms of induction of genes producing volatile organic compounds, and the subsequent increase in volatile terpenes, has been achieved in maize using (Z)-3-hexen-1-ol and other plant hormones.
Anthropogenic sources
Anthropogenic sources emit about 142 teragrams (1.42 × 1011 kg) of carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
per year in the form of VOCs.
The major source of man-made VOCs are:
* Fossil fuel use and production, e.g. incompletely combusted fossil fuels or unintended evaporation of fuels. The most prevalent VOC is ethane
Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petroc ...
, a relatively inert compound.
*Solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
s used in coatings, paints
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 ...
, and inks. Approximately 12 billion litres of paint are produced annually. Typical solvents include aliphatic hydrocarbons, ethyl acetate
Ethyl acetate ( systematically ethyl ethanoate, commonly abbreviated EtOAc, ETAC or EA) is the organic compound with the formula , simplified to . This colorless liquid has a characteristic sweet smell (similar to pear drops) and is used in glues ...
, glycol ether
Glycol ethers are a class of chemical compounds consisting of alkyl ethers that are based on glycols such as ethylene glycol or propylene glycol. They are commonly used as solvents in paints and cleaners. They have good solvent properties while h ...
s, and acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscib ...
. Motivated by cost, environmental concerns, and regulation, the paint and coating industries are increasingly shifting toward aqueous solvents.
*Compressed aerosol products, mainly butane and propane, estimated to contribute 1.3 billion tonnes of VOC emissions per year globally.
* Biofuel use, e.g., cooking oils in Asia and bioethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a hyd ...
in Brazil.
*Biomass combustion, especially from rain forests. Although combustion principally releases carbon dioxide and water, incomplete combustion affords a variety of VOCs.
Indoor VOCs
Concentrations of VOCs in indoor air may be 2 to 5 times greater than in outdoor air, sometimes far greater. During certain activities, indoor levels of VOCs may reach 1,000 times that of the outside air. Studies have shown that emissions of individual VOC species are not that high in an indoor environment, but the total concentration of all VOCs (TVOC) indoors can be up to five times higher than that of outdoor levels. New buildings experience particularly high levels of VOC off-gassing indoors because of the abundant new materials (building materials, fittings, surface coverings and treatments such as glues, paints and sealants) exposed to the indoor air, emitting multiple VOC gases. This off-gassing has a multi-exponential decay trend that is discernible over at least two years, with the most volatile compounds decaying with a time-constant of a few days, and the least volatile compounds decaying with a time-constant of a few years. New buildings may require intensive ventilation for the first few months, or a ''bake-out'' strategy. Existing buildings may be replenished with new VOC sources, such as new furniture, consumer products, and redecoration of indoor surfaces, all of which lead to a continuous background emission of TVOCs, requiring improved ventilation.
Numerous studies show strong seasonal variations in indoors VOC emissions, with emission rates increasing in summer. This is largely due to the rate of diffusion of VOC species through materials to the surface, increasing with temperature. Most studies have shown that this leads to generally higher concentrations of TVOCs indoors in summer.
Indoor air quality measurements
Measurement of VOCs from the indoor air is done with sorption tubes e. g. Tenax (for VOCs and SVOCs) or DNPH-cartridges (for carbonyl-compounds) or air detector. The VOCs adsorb on these materials and are afterwards desorbed either thermally (Tenax) or by elution
In analytical and organic chemistry, elution is the process of extracting one material from another by washing with a solvent; as in washing of loaded ion-exchange resins to remove captured ions.
In a liquid chromatography experiment, for exam ...
(DNPH) and then analyzed by GC-MS/FID
A fid is a conical tool traditionally made of wood or bone. It is used to work with rope and canvas in marlinespike seamanship. A fid differs from a marlinspike in material and purposes. A marlinspike is used in working with wire rope, natural ...
or HPLC. Reference gas mixtures are required for quality control of these VOC-measurements. Furthermore, VOC emitting products used indoors, e.g. building products and furniture, are investigated in emission test chambers under controlled climatic conditions. For quality control of these measurements round robin tests are carried out, therefore reproducibly emitting reference materials are ideally required.[ Other methods have used silcosteel canisters with constant flow inlets to collect samples over several days. These methods are not limited by the adsorbing properties of materials like Tenax.
]
Regulation of indoor VOC emissions
In most countries, a separate definition of VOCs is used with regard to indoor air quality that comprises each organic chemical compound that can be measured as follows: adsorption from air on Tenax TA, thermal desorption, gas chromatographic separation over a 100% nonpolar column ( dimethylpolysiloxane). VOC (volatile organic compounds) are all compounds that appear in the gas chromatogram between and including ''n''-hexane and ''n''-hexadecane. Compounds appearing earlier are called VVOC (very volatile organic compounds); compounds appearing later are called SVOC (semi-volatile organic compounds).
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
, Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
(AgBB/DIBt), Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
, Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...
(TEK regulation), and Italy
Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...
(CAM Edilizia) have enacted regulations to limit VOC emissions from commercial products. European industry has developed numerous voluntary ecolabels and rating systems, such as EMICODE, M1, Blue Angel, GuT (textile floor coverings), Nordic Swan Ecolabel, EU Ecolabel
EU Ecolabel or EU Flower is a voluntary ecolabel scheme established in 1992 by the European Union.
Logo
The label includes a green flower with inclined green "ϵ" (epsilon, Greek epsilon) as the flower, surrounded by 12 blue stars. On EU Ecolabe ...
, and Indoor Air Comfort. In the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, several standards exist; California Standard CDPH Section 01350 is the most common one. These regulations and standards changed the marketplace, leading to an increasing number of low-emitting products.
Health risks
Respiratory
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 gre ...
, allergic
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic der ...
, or immune effects in infants or children are associated with man-made VOCs and other indoor or outdoor air pollutants.
Some VOCs, such as styrene
Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...
and limonene
Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the oil of citrus fruit peels. The -isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring a ...
, can react with nitrogen oxides or with ozone to produce new oxidation products and secondary aerosols, which can cause sensory irritation symptoms. VOCs contribute to the formation of tropospheric 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 Earth's atmosphere), with an average concentration of 20–30 parts per billion by volume (ppbv), with c ...
and smog.
Health effects include eye, nose, and throat irritation
Throat irritation can refer to a dry cough, a scratchy feeling at the back of the throat, a sensation of a lumpy feeling, something stuck at the back of the throat, or possibly a feeling of dust in the throat. The symptoms are unpleasant and usuall ...
; headaches, loss of coordination, nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
; and damage to the liver, kidney, and 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 p ...
. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, 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 breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing di ...
, declines in serum cholinesterase
The enzyme cholinesterase (EC 3.1.1.8, choline esterase; systematic name acylcholine acylhydrolase) catalyses the hydrolysis of choline-based esters:
: an acylcholine + H2O = choline + a carboxylate
Several of these serve as neurotransmitters ...
levels, nausea, vomiting, nose bleeding, fatigue, dizziness.
The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic to those with no known health effects. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes.
Ingestion
While null in comparison to the concentrations found in indoor air, benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
, toluene
Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) a ...
, and methyl tert-butyl ether
Methyl ''tertiary''-butyl ether (MTBE), also known as methyl tert-butyl ether and ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly sol ...
(MTBE) were found in samples of human milk and increase the concentrations of VOCs that we are exposed to throughout the day. A study notes the difference between VOCs in alveolar breath and inspired air suggesting that VOCs are ingested, metabolized, and excreted via the extra-pulmonary pathway. VOCs are also ingested by drinking water in varying concentrations. Some VOC concentrations were over the EPA’s National Primary Drinking Water Regulations and China’s National Drinking Water Standards set by the Ministry of Ecology and Environment
The Ministry of Ecology and Environment, formerly the Ministry of Environmental Protection of the People's Republic of China, and prior to 2008 known as the State Environmental Protection Administration, is a department of the State Council of t ...
.
Dermal absorption
The presence of VOCs in the air and in groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...
has prompted more studies. Several studies have been performed to measure the effects of dermal absorption of specific VOCs. Dermal exposure to VOCs like 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 ...
and toluene downregulate antimicrobial peptides on the skin like cathelicidin LL-37, human β-defensin 2 and 3. Xylene
In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are s ...
and formaldehyde worsen allergic inflammation in animal models. Toluene also increases the dysregulation of filaggrin
Filaggrin (filament aggregating protein) is a filament-associated protein that binds to keratin fibers in epithelial cells. Ten to twelve filaggrin units are post-translationally hydrolyzed from a large profilaggrin precursor protein during termi ...
: a key protein in dermal regulation. this was confirmed by immunofluorescence to confirm protein loss and western blotting to confirm mRNA loss. These experiments were done on human skin samples. Toluene exposure also decreased the water in the trans-epidermal layer allowing for vulnerability in the skin’s layers.
Limit values for VOC emissions
Limit values for VOC emissions into indoor air are published by AgBB, AFSSET, California Department of Public Health
The California Department of Public Health (CDPH) is the state department responsible for public health in California. It is a subdivision of the California Health and Human Services Agency. It enforces some of the laws in the California Health ...
, and others. These regulations have prompted several companies in the paint and adhesive industries to adapt with VOC level reductions their products. VOC labels and certification programs may not properly assess all of the VOCs emitted from the product, including some chemical compounds that may be relevant for indoor air quality. Each ounce of colorant A colourant/colour additive (British spelling) or colorant/color additive (American spelling) is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing ...
added to tint paint may contain between 5 and 20 grams of VOCs. A dark color, however, could require 5–15 ounces of colorant, adding up to 300 or more grams of VOCs per gallon of paint.
VOCs in healthcare settings
VOCs are also found in hospital and health care environments. In these settings, these chemicals are widely used for cleaning, disinfection, and hygiene of the different areas. Thus, health professionals such as nurses, doctors, sanitation staff, etc., may present with adverse health effects such as 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, co ...
; however, further evaluation is required to determine the exact levels and determinants that influence the exposure to these compounds.
Studies have shown that the concentration levels of different VOCs such as halogenated and aromatic hydrocarbons differ substantially between areas of the same hospital. However, one of these studies reported that ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
, isopropanol, ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...
, and acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscib ...
were the main compounds in the interior of the site. Following the same line, in a study conducted in the United States, it was established that nursing assistants are the most exposed to compounds such as ethanol, while medical equipment preparers are most exposed to 2-propanol
Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable organic compound with a pungent alcoholic odor. As an isopropyl group linked to a hydroxyl group (chemical formula ) it is the sim ...
.
In relation to exposure to VOCs by cleaning and hygiene personnel, a study conducted in 4 hospitals in the United States established that sterilization and disinfection workers are linked to exposures to d-limonene
Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the essential oil, oil of citrus fruit peel (fruit), peels. The -isomer, occurring more commonly in nature as the fragrance o ...
and 2-propanol, while those responsible for cleaning with chlorine-containing products are more likely to have higher levels of exposure to α-pinene
α-Pinene is an organic compound of the terpene class, one of two isomers of pinene. It is an alkene and it contains a reactive four-membered ring. It is found in the oils of many species of many coniferous trees, notably the pine. It is also ...
and chloroform. Those who perform floor and other surface cleaning tasks (e.g., floor waxing) and who use quaternary ammonium, alcohol, and chlorine-based products are associated with a higher VOC exposure than the two previous groups, that is, they are particularly linked to exposure to acetone, chloroform, α-pinene, 2-propanol or d-limonene.
Other healthcare environments such as nursing and age care homes have been rarely a subject of study, even though the elderly and vulnerable populations may spend considerable time in these indoor settings where they might be exposed to VOCs, derived from the common use of cleaning agents, sprays and fresheners. In a study conducted in France, a team of researchers developed an online questionnaire for different social and age care facilities, asking about cleaning practices, products used, and the frequency of these activities. As a result, more than 200 chemicals were identified, of which 41 are known to have adverse health effects, 37 of them being VOCs. The health effects include skin sensitization, reproductive and organ-specific toxicity, carcinogenicity
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 sub ...
, mutagenicity
In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer i ...
, and endocrine-disrupting properties. Furthermore, in another study carried out in the same European country, it was found that there is a significant association between breathlessness in the elderly population and elevated exposure to VOCs such as toluene and o-xylene, unlike the remainder of the population.
Analytical methods
Sampling
Obtaining samples for analysis is challenging. VOCs, even when at dangerous levels, are dilute, so preconcentration is typically required. Many components of the atmosphere are mutually incompatible, e.g. 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 organic compounds, peroxyacyl nitrates and many organic compounds. Furthermore, collection of VOCs by condensation in cold traps also accumulates a large amount of water, which generally must be removed selectively, depending on the analytical techniques to be employed.[
]Solid-phase microextraction
Solid phase microextraction, or SPME, is a solid phase extraction sampling technique that involves the use of a fiber coated with an extracting phase, that can be a liquid (polymer) or a solid (sorbent), which extracts different kinds of analytes ( ...
(SPME) techniques are used to collect VOCs at low concentrations for analysis. As applied to breath analysis, the following modalities are employed for sampling: gas sampling bags, syringes, evacuated steel and glass containers.[
]
Principle and measurement methods
In the U.S., standard methods have been established by the National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH) and another by U.S. OSHA. Each method uses a single component solvent; butanol
Butanol (also called butyl alcohol) is a four-carbon alcohol with a formula of C4 H9 O H, which occurs in five isomeric structures (four structural isomers), from a straight-chain primary alcohol to a branched-chain tertiary alcohol; all are a bu ...
and hexane
Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14.
It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...
cannot be sampled, however, on the same sample matrix using the NIOSH or OSHA method.
VOCs are quantified and identified by two broad techniques. The major technique is gas chromatography (GC). GC instruments allow the separation of gaseous components. When coupled to a flame ionization detector
A flame ionization detector (FID) is a scientific instrument that measures analytes in a gas stream. It is frequently used as a detector in gas chromatography. The measurement of ion per unit time make this a mass sensitive instrument. Standalo ...
(FID) GCs can detect hydrocarbons at the parts per trillion levels. Using electron capture detectors, GCs are also effective for organohalide
Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (fluorine, chlorine, bromine or iodine – ) resulting in the formation of organofluorine compounds, organochlori ...
such as chlorocarbons.
The second major technique associated with VOC analysis is mass spectrometry, which is usually coupled with GC, giving the hyphenated technique of GC-MS.
Direct injection mass spectrometry techniques are frequently utilized for the rapid detection and accurate quantification of VOCs. PTR-MS is among the methods that have been used most extensively for the on-line analysis of biogenic and anthropogenic VOCs. PTR-MS instruments based on time-of-flight mass spectrometry
Time-of-flight mass spectrometry (TOFMS) is a method of mass spectrometry in which an ion's mass-to-charge ratio is determined by a time of flight measurement. Ions are accelerated by an electric field of known strength. This acceleration res ...
have been reported to reach detection limit
The limit of detection (LOD or LoD) is the lowest signal, or the lowest corresponding quantity to be determined (or extracted) from the signal, that can be observed with a sufficient degree of confidence or statistical significance. However, the ...
s of 20 pptv after 100 ms and 750 ppqv after 1 min. measurement (signal integration) time. The mass resolution
In mass spectrometry, resolution is a measure of the ability to distinguish two peaks of slightly different mass-to-charge ratios ''ΔM'', in a mass spectrum.
Resolution and resolving power
There are two different definitions of resolution an ...
of these devices is between 7000 and 10,500 m/Δm, thus it is possible to separate most common isobaric VOCs and quantify them independently.
Chemical fingerprinting and breath analysis
The exhaled human breath contains a few thousand volatile organic compounds and is used in breath biopsy to serve as a VOC biomarker
In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, p ...
to test for diseases, such as 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 tissues of the lung. Lung carcinomas derive from transformed, malign ...
. One study has shown that "volatile organic compounds ... are mainly blood borne and therefore enable monitoring of different processes in the body." And it appears that VOC compounds in the body "may be either produced by metabolic processes or inhaled/absorbed from exogenous sources" such as environmental tobacco smoke
Passive smoking is the inhalation of tobacco smoke, called secondhand smoke (SHS), or environmental tobacco smoke (ETS), by persons other than the intended "active" smoker. It occurs when tobacco smoke enters an environment, causing its inhalat ...
. Chemical fingerprinting and breath analysis of volatile organic compounds has also been demonstrated with chemical sensor arrays, which utilize pattern recognition for detection of component volatile organics in complex mixtures such as breath gas.
Metrology for VOC measurements
To achieve comparability of VOC measurements, reference standards traceable to SI-units are required. For a number of VOCs gaseous reference standards are available from specialty gas suppliers or national metrology institutes, either in the form of cylinders or dynamic generation methods. However, for many VOCs, such as oxygenated VOCs, monoterpene
Monoterpenes are a class of terpenes that consist of two isoprene units and have the molecular formula C10H16. Monoterpenes may be linear (acyclic) or contain rings (monocyclic and bicyclic). Modified terpenes, such as those containing oxygen func ...
s, or 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 ...
, no standards are available at the appropriate amount of fraction due to the chemical reactivity or adsorption
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which ...
of these molecules. Currently, several national metrology institutes are working on the lacking standard gas mixtures at trace level concentration, minimising adsorption processes, and improving the zero gas.[ The final scopes are for the ]traceability Traceability is the capability to trace something. In some cases, it is interpreted as the ability to verify the history, location, or application of an item by means of documented recorded identification.
Other common definitions include the capab ...
and the long-term stability of the standard gases to be in accordance with the data quality objectives (DQO, maximum uncertainty of 20% in this case) required by the WMO/GAW
Gaw or GAW may refer to:
People
* Gaw (surname), a Gaelic-language surname
Places
* Gaw, Myanmar, a town in Thandwe District, Rakhine State
* Gaw Township, a township of Rakhine State
Other uses
* Game & Watch, electronic handheld games ...
program.
See also
* Aroma compound
An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently v ...
* Criteria air contaminants
* Fugitive emissions
Fugitive emissions are leaks and other irregular releases of gases or vapors from a pressurized containment – such as appliances, storage tanks, pipelines, wells, or other pieces of equipment – mostly from industrial activities. In addition ...
* Non-methane volatile organic compound Non-methane volatile organic compounds (NMVOCs) are a set of organic compounds that are typically photochemically reactive in the atmosphere—marked by the exclusion of methane. NMVOCs include a large variety of chemically different compounds, suc ...
* Organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
* VOC contamination of groundwater VOCs (volatile organic compounds) are a dangerous contaminant of groundwater, leading to groundwater pollution. They are generally introduced to the environment through careless industrial practices.
Overview
VOCs are responsible for a number of ...
* Volatile Organic Compounds Protocol
The Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution Concerning the Control of Emissions of Volatile Organic Compounds or Their Transboundary Fluxes (known as the Volatile Organic Compounds Protocol or the VOC Protocol) is ...
References
External links
Volatile Organic Compounds (VOCs) web site of the Chemicals Control Branch of Environment Canada
VOC emissions and calculations
Examples of product labels with low VOC emission criteria
KEY-VOCS: Metrology for VOC indicators in air pollution and climate change, a European Metrology Research Project.
VOCs in Paints
{{DEFAULTSORT:Volatile Organic Compound
Building biology
Organic compounds
Pollutants
Smog
Flavors
Perfumes
Pollution
Occupational safety and health