Benzo 'a''yrene (B''a''P or B ) is a

polycyclic aromatic hydrocarbon A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, incine ...

and the result of incomplete combustion of

organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...

at temperatures between and . The ubiquitous compound can be found in coal tar, tobacco smoke and many foods, especially grilled meats. The substance with the formula C₂₀H₁₂ is one of the

benzopyrene A benzopyrene is an organic compound with the formula C20H12. Structurally speaking, the colorless isomers of benzopyrene are pentacyclic hydrocarbons and are fusion products of pyrene and a phenylene group. Two isomeric species of benzopyrene ...

s, formed by a

benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

ring fused to

pyrene Pyrene is a polycyclic aromatic hydrocarbon (PAH) consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is . This yellow-green solid is the smallest peri-fused PAH (one where the rings are fused thro ...

. Its

diol A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol may also be called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. They are used as protecting gro ...

epoxide In organic chemistry, an epoxide is a cyclic ether, where the ether forms a three-atom ring: two atoms of carbon and one atom of oxygen. This triangular structure has substantial ring strain, making epoxides highly reactive, more so than other ...

metabolites, more commonly known as BPDE, react with and bind to

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

, resulting in mutations and eventually cancer. It is listed as a Group 1 carcinogen by the

IARC IARC may refer to: * International Aerial Robotics Competition * International Age Rating Coalition * International Agency for Research on Cancer * International Arctic Research Center * Israel Association of Radio Communication * iArc, South Ko ...

. In the 18th century a scrotal cancer of chimney sweepers, the

chimney sweeps' carcinoma Chimney sweeps' cancer, also called soot wart or scrotal cancer, is a squamous cell carcinoma of the scrotum. It has the distinction of being the first reported form of occupational disease, occupational cancer, and was initially identified by P ...

, was already known to be connected to soot.

Description

Benzo 'a''yrene (B''a''P) is a

found in

coal tar Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It is a type of creosote. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoria ...

with the formula C₂₀H₁₂. The compound is one of the

s, formed by a

ring fused to

, and is the result of incomplete combustion at temperatures between and .

Sources

The main source of atmospheric B''a''P is residential wood burning. It is also found in

, in automobile exhaust fumes (especially from

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

s), in all smoke resulting from the combustion of organic material (including

cigarette smoke Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C ...

), and in

charbroil A charbroiler (also referred to as a chargrill, char-broiler or simply broiler) is a commonly used cooking device consisting of a series of grates or ribs that can be heated using a variety of means, and is used in both residential and commerci ...

ed food. A 2001

National Cancer Institute The National Cancer Institute (NCI) coordinates the United States National Cancer Program and is part of the National Institutes of Health (NIH), which is one of eleven agencies that are part of the U.S. Department of Health and Human Services. ...

study found levels of B''a''P to be significantly higher in foods that were cooked well-done on the

barbecue Barbecue or barbeque (often shortened to BBQ worldwide; barbie or barby in Australia and New Zealand) is a term used with significant regional and national variations to describe various cooking methods that employ live fire and smoke to coo ...

, particularly

steak A steak is a cut of meat sliced across muscle fibers, sometimes including a bone. It is normally Grilling, grilled or Pan frying, fried, and can be diced or cooked in sauce. Steaks are most commonly cut from cattle (beefsteak), but can also ...

chicken The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and w ...

with skin, and

hamburger A hamburger (or simply a burger) consists of fillings—usually a patty of ground meat, typically beef—placed inside a sliced bun or bread roll. The patties are often served with cheese, lettuce, tomato, onion, pickles, bacon, or chilis ...

s: Cooked meat products have been shown to contain up to 4 ng/g of B''a''P, and up to 5.5 ng/g in fried chicken and 62.6 ng/g in overcooked charcoal barbecued beef. B''a''P is discharged in wastewater by industries such as

smelter Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron, copper, silver, tin, lead and zin ...

s, particularly

iron and steel Ferrous metallurgy is the metallurgy of iron and its alloys. The earliest surviving prehistoric iron artifacts, from the 4th millennium BC in Egypt, were made from meteoritic iron-nickel. It is not known when or where the smelting of iron from ...

mills and

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

smelters.

History

In the 18th century, young British

chimney sweep A chimney sweep is a person who inspects then clears soot and creosote from chimneys. The chimney uses the pressure difference caused by a hot column of gas to create a draught and draw air over the hot coals or wood enabling continued combust ...

s who climbed into chimneys suffered from

, a scrotal cancer peculiar to their profession, and this was connected to the effects of

soot Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. Soot is considered a hazardous substance with carcinogenic properties. Most broadly, the term includes all the particulate matter produced b ...

in 1775, in the first work of

occupational cancer Occupational cancer is cancer caused by occupational hazards. Several cancers have been directly tied to occupational hazards, including chimney sweeps' carcinoma, mesothelioma, and others. Types of hazards Occupational exposure to chemicals, dus ...

epidemiology and also the first connection of any

chemical mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more elements or compounds mechanically mixed together in any proporti ...

to cancer formation. Frequent

skin cancer Skin cancers are cancers that arise from the Human skin, skin. They are due to the development of abnormal cells (biology), cells that have the ability to invade or metastasis, spread to other parts of the body. It occurs when skin cells grow ...

s were noted among fuel industry workers in the 19th century. In 1933, B''a''P was determined to be the compound responsible for these cases, and its carcinogenicity was demonstrated when skin tumors occurred in laboratory animals repeatedly painted with coal tar. B''a''P has since been identified as a prime carcinogen in cigarette smoke.

Toxicity

Nervous system

Prenatal exposure Pregnancy is the time during which one or more offspring gestates inside a woman's uterus. A multiple pregnancy involves more than one offspring, such as with twins. Conception usually occurs following vaginal intercourse, but can also oc ...

of B''a''P in rats is known to affect learning and memory in rodent models. Pregnant rats eating B''a''P were shown to negatively affect the brain function in the late life of their offspring. At a time when

synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

s are first formed and adjusted in strength by activity, B''a''P diminished

NMDA ''N''-methyl--aspartic acid, or ''N''-methyl--aspartate (NMDA), is an amino acid derivative that acts as a specific agonist at the NMDA receptor mimicking the action of glutamate, the neurotransmitter which normally acts at that receptor. Unl ...

receptor-dependent nerve cell activity measured as mRNA expression of the NMDA NR2B receptor subunit.

Immune system

B''a''P has an effect on the number of

white blood cell White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are cells of the immune system that are involved in protecting the body against both infectious disease and foreign entities. White blood cells are genera ...

s, inhibiting some of them from differentiating into

macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

s, the body's first line of defense to fight infections. In 2016, the molecular mechanism was uncovered as damage to the macrophage membrane's lipid raft integrity by decreasing membrane cholesterol at 25%. This means less immunoreceptors

CD32 CD32 (cluster of differentiation 32), also known as FcγRII or FCGR2, is a surface receptor glycoprotein belonging to the Ig gene superfamily. CD32 can be found on the surface of a variety of immune cells. CD32 has a low-affinity for the Fc r ...

(a member of the Fc family of immunoreceptors) could bind to

IgG Immunoglobulin G (IgG) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ant ...

and turn the white blood cell into a macrophage. Therefore, macrophage membranes become susceptible to bacterial infections.

Reproductive system

In experiments with male rats,

subchronic {{Short pages monitor {{Aryl hydrocarbon receptor modulators IARC Group 1 carcinogens Polycyclic aromatic hydrocarbons PBT substances