Hydrocarbons (contain hydrogen and carbon atoms)
Hydrocarbons are a class of chemicals that contain only hydrogen and carbon atoms. Some have hydrogen with rings of carbon atoms, called polycyclic aromatic hydrocarbons or PAHs. Hydrocarbons with additives, such as gasoline, also are included. Typical substances include automotive gasoline, benzene, butadiene, fuel oils, jet fuels, and various PAHs. PAHs include naphthylene and over 100 different substances formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat. PAHs are found in coal tar, crude oil, creosote, and roofing tar, but a few are used in medicines or to make dyes, plastics, and pesticides. This list is not all inclusive.