The increase of aromatics, olefins, and other organic compounds in the fuels used leads to an increase in the emission of aromatic S. Benzene, toluene, ethylbenzene, and xylene, collectively termed BTEX, are the most abundant among the aromatic volatile hydro carbons. Evaporated and liquid gasoline are the next most abundant contributors in most areas. Refinery, forest fire, and other industrial source contributions are area specific.