In environmental science, the term usually refers to the hydrocarbons, especially those found in air pollution. In 1988, the five most abundant of these hydrocarbons in urban air were isopentane, n-butane, toluene, propane, and ethane; each of these compounds has unburned gasoline as its primary source. In the presence of sunlight, hydrocarbons react with ozone, nitrogen oxides, and other components of polluted air to form compounds that are hazardous to plants, animals, and humans. In 1995, volatile organic compounds ranked third behind carbon monoxide and particulate matter (which includes dust, smoke, soot, and chemical liquid droplets from various sources) and just above sulfur and nitrogen oxides in annual pollutant emissions in the United States.

See Also

Air Pollution Control; Air Quality