Polycyclic aromatic hydrocarbons
From Glossary of Meteorology
polycyclic aromatic hydrocarbons
(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.