Class of organic compounds composed of multiple fused aromatic rings, formed by incomplete combustion of organic matter and present in coal tar, creosote, fuel oil, asphalt, and soot. Benzo(a)pyrene is the prototypical Class 1 human carcinogen of the class.
PAHs are produced wherever organic matter burns incompletely: wildfires, internal combustion engines, coal combustion, and historical coal-gasification and creosote-treating operations. Sixteen PAHs are tracked routinely under U.S. EPA Method 8270 (the EPA-16 list), with benzo(a)pyrene as the indicator carcinogen and benchmark for relative potency calculations across the class.
Environmental fate is driven by hydrophobicity: PAHs sorb strongly to soil and sediment and dissolve poorly in water, so plumes are short and source mass is concentrated. Remediation routes include thermal treatment (the dominant choice for creosote and coal-tar sites), bioremediation (slow, partial), soil washing (effective when fines fraction is small), and stabilization/solidification (acceptable for some land uses).
Also known as: PAH, PAHs, polycyclic aromatic hydrocarbons, polynuclear aromatic hydrocarbons.
Petroleum Hydrocarbons: treatment approach
The full spectrum of petroleum-derived organic compounds — crude oil, condensate, diesel, gasoline, jet fuel, and bunker fuel — reported analytically as total petroleum hydrocarbons (TPH) in gasoline-range (C6–C10), diesel-range (C10–C28), and heavy-range (C28–C40) fractions.
Per- and polyfluoroalkyl substances: a class of more than 12,000 synthetic compounds built around exceptionally stable carbon-fluorine bonds. PFAS is the family name, not a single chemical. PFOA and PFOS are two specific members of this class.
Perfluorooctanoic acid: a specific eight-carbon long-chain PFAS compound, historically used in non-stick coatings and AFFF firefighting foam. Classified by IARC in 2023 as Group 1, carcinogenic to humans.
Perfluorooctane sulfonic acid: a specific eight-carbon long-chain PFAS compound, historically the active surfactant in 3M Scotchgard and AFFF firefighting foam. Classified by IARC in 2023 as Group 2B, possibly carcinogenic to humans.
Polychlorinated dibenzo-p-dioxins and related furans: highly persistent, fat-soluble chlorinated compounds formed as unintended byproducts of combustion, chlorine-based manufacturing, and herbicide production, with TCDD among the most toxic substances ever characterized.