What is polycyclic aromatic hydrocarbons?

polycyclic aromatic hydrocarbons — Polycyclic aromatic hydrocarbons (PAHs) are a class of very stable organic molecules. They are flat molecules made only of carbon and hydrogen atoms. PAH molecules are quite common and highly carcinogenic. They are one of the by-products of combustion from automobiles and airplanes, and some are present in charcoal broiled hamburgers.