Chemical identification and toxicity
Polycyclic aromatic hydrocarbons (PAHs) are composed of two or more fused rings made up of carbon and hydrogen atoms (see IPCS 1998 in supporting documents). They have at least one aromatic ring and can contain 5-membered, non-aromatic rings. The PAH chemical class includes unsubstituted and alkylated compounds and belongs to a broader polycyclic aromatic compound (PAC) class that also includes N-, S-, and O-substituted PAHs as well as heterocyclic compounds containing N, S, or O atoms within the ring structure. For the purposes of this document, PAHs and related compounds are referred to generally as PAHs or by a description of the defining structural modification (e.g., oxygenated PAHs, N-heterocyclics).