Volatile Organic Compounds
A vast range of the organic compounds are emitted into the atmosphere through a range of natural and anthropogenic processes; in the latter case, particularly associated with vehicle exhaust emissions and fuel volatilization, paints and solvent usage.
1,3-Butadiene and benzene, which are well-known carcinogens, are of particular concern to public health.
Other aromatic compounds-toluene, ethyl benzene, and xylenes (together with benzene, often termed BTEX) - are also of concern for public health; they are both carcinogenic in their own right, and substantial contributors to the VOC pool, which leads to the formation of atmospheric ozone and secondary organic aerosol.
Depending on location, the BTEX compounds may form a substantial fraction of upto 40% of petroleum.
Related compounds, including naphthalene and polycyclic aromatic hydrocarbons (PAHs) such as anthracene are the subject of increasing attention.
A substantial fraction of such semivolatile species is usually present in the particulate form, rather-than vapor phase; measurement of PHAs, therefore, requires consideration of both the gaseous- and aerosolbound components.