What happens to PAHs when they enter the environment?
• PAHs enter the air mostly as releases from volcanoes, forest fires, burning coal, and automobile exhaust. • PAHs can occur in air attached to dust particles. • Some PAH particles can readily evaporate into the air from soil or surface waters. • PAHs can break down by reacting with sunlight and other chemicals in the air, over a period of days to weeks. • PAHs enter water through discharges from industrial and wastewater treatment plants. • Most PAHs do not dissolve easily in water. They stick to solid particles and settle to the bottoms of lakes or rivers. • Microorganisms can break down PAHs in soil or water after a period of weeks to months. • In soils, PAHs are most likely to stick tightly to particles; certain PAHs move through soil to contaminate underground water. • PAH contents of plants and animals may be much higher than PAH contents of soil or water in which they live.
