THC (Total Hydro Carbons)
Hydrocarbon emissions are a product of partial fuel combustion, fuel evaporation and refueling losses caused by spillage and vapor leakage. Hydrocarbons react with nitrogen oxides and sunlight to form ozone. Some hydrocarbons are toxic and may be carcinogenic.
Polycyclic Aromatic Hydrocarbons, also known as PAH, are chemical compounds that consist of fused aromatic rings and that do not contain heteroatoms and that do not carry substituents. Many of them are known or suspected carcinogens. They are formed by incomplete combustion of carbon-containing fuels such as wood, coal, diesel, fat, or tobacco.