Aerosols

A number of environmental problems are associated with aerosols, the vast majority of them associated with aerosols produced by human activities. For example, smoke released during the incomplete combustion of fossil fuels results in the formation of at least two major types of aerosols that may be harmful to plant and animal life. One type consists of finely divided carbon released from unburned fuel. This soot can damage plants by coating their leaves and reducing their ability to carry out photosynthesis. It can also clog the alveoli, air sacs in human lungs, and interfere with a person's respiration.

A second type of harmful aerosol is formed when stack gases, such as sulfur dioxide and nitrogen oxides, react with oxygen and water vapor in the air to form sulfuric and nitric acids, respectively. Mists containing these acids may be carried hundreds of miles from their original source before conglomeration occurs and the acids fall to Earth as "acid rain." Considerable disagreement exists about the precise nature and extent of the damage caused by acid rain. But there seems to be little doubt that in some locations it has caused severe harm to plant and aquatic life.