Commonly referred to as PAHs, these compounds form easily by heating almost any organic or carbon-rich material; for example, PAHs form when red meat is burnt, and they have been found to be linked to cancer. Aromatic hydrocarbons contain flat rings of carbon atoms, usually six carbons arranged in a hexagon; polycyclic means that the molecules contain more than one "aromatic" ring.

see 'PAH'

PAHs comprise one category of base/neutral acid or extractable compounds and are a group of chemicals that are formed during the burning of coal, oil, gas, wood, or other organic substance. Some PAHs are contained in asphalt used for paving roads or runways. There are more than 100 different PAH compounds and they are found throughout the environment in air, water, and soil. Most PAHs do not appear alone in the environment but, rather, in complex mixtures of many individual PAHs, which may be carcinogenic or noncarcinogenic.

a group of organic chemicals that includes several petroleum products and their derivatives.

a class of chemical compounds composed of fused six-carbon rings. PAHs are commonly found in petroleum oils and are emitted from various combustion processes (automobile exhaust, burning of wood and coal)

Organic compounds that include only carbon and hydrogen with a fused ring structure containing at least two benzene (six-sided) rings. PAHs may also contain additional fused rings that are not six-sided. The combustion of organic substances is a common source of atmospheric PAHs.

compounds produced during the burning of organic material such as wood and fossil fuels and are a component of uncombusted petroleum

The PAHs are widely distributed throughout the marine environment and commonly occur in sediments in urban coastal and estuarine areas. Sources include crude oil, petroleum products and residues from combustion of fossil fuels. They are composed of fused benzene rings, with or without alkyl substituents (e.g., methyl groups).

formed by industrial processes and during combustion of fossil fuels and other substances; include some potent carcinogens.

PAHs come from both natural and human-made sources, and are formed during the incomplete burning of coal, oil, gas, garbage, or other organic substances; some PAHs are manufactured. Forest fires are the largest natural source of PAHs in Canada. The greatest human-made sources of PAHs are aluminum smelters, coking plants, creosote-treated products, spills of petroleum products and transportation. PAHs have been identified as probably cancer-causing, and are suspected reproductive and respiratory toxins.

(Hydrocarbures aromatiques polycycliques [HAP]) Organic compounds composed of two or more benzene rings, where adjacent rings share two carbon atoms; nonaromatic rings may also be present.

compounds found in combustion tars, created in the burning of nearly all fuels, which are metabolically activated (especially in the liver) to a mutagenic and carcinogenic form. These are probably the most important human chemical carcinogens and are suspected of being responsible for many of human cancers other than solar ultraviolet induced skin cancers. Tobacco smoke is by far the most important source of humans. They are also found in relatively large quantities on charcoal broiled meats.

Also known as polynuclear aromatic hydrocarbons (PNAs) formed during incomplete combustion of fuels (coal and petroleum products) and cellulosic material (wood, paper, tobacco). They are multiringed hydrocarbon compounds (aromatics) that share two or more carbon atoms by two or more rings. Many compounds in this group are carcinogenic.

(Abbreviated PAHs.) Class of large aromatic molecules composed of several benzene rings fused together. Some PAHs show very high carcinogenic and mutagenic activity. They are found in organic residues, such as soot, coal tar, and combustion exhaust. Due to their low volatility, PAHs are usually taken up onto organic aerosols, which facilitates their inhalation.