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Metabolism of PAHs occurs via the cytochrome P450-mediated mixed function oxidase system with oxidation or hydroxylation as the first step. They are rapidly distributed in a wide variety of tissues with a marked tendency for localization in body fat. PAHs are highly lipid soluble and thus readily absorbed from the gastrointestinal tract of mammals. Many PAHs have toxic, mutagenic and/or carcinogenic properties. Atmospheric deposition is a major source for PAHs in soil. The removal of PAHs from the atmosphere by dry and wet deposition processes are strongly influenced by their gas/particle partitioning. Atmospheric partitioning of PAH compounds between the particulate and the gaseous phases strongly influences their fate and transport in the atmosphere and the way they enter into the human body. PAHs are found in the ambient air in gas-phase and as sorbet to aerosols. Major anthropogenic sources of PAHs include residential heating, coal gasification and liquefying plants, carbon black, coal-tar pitch and asphalt production, coke and aluminum production, catalytic cracking towers and related activities in petroleum refineries as well as and motor vehicle exhaust. Emissions from anthropogenic activities predominate nevertheless, some PAHs in the environment originate from natural sources such as open burning, natural losses or seepage of petroleum or coal deposits, and volcanic activities.
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants generated primarily during the incomplete combustion of organic materials (e.g.