Air Pollution

The Atmosphere

Troposphere is the innermost layer if the atmosphere, to about 17 kilometers (11 miles) above sea level; it contains about 75-80% of the earth's air.

Stratosphere is the layer from about 17 to 48 kilometers (11-30 miles)
above the earth's surface. The stratosphere contains a layer of ozone that shields the earth from much (about 95%) of the ultraviolet radiation coming from the sun.

Ozone (O3) is a human-made pollutant in the troposphere but a naturally produced, essential component of the stratosphere. There is evidence that some human activities are decreasing the amount of beneficial ozone in the atmosphere and increasing the harmful ozone in the troposphere.

Outdoor Air Pollution

Primary pollutants are those emitted directly into the troposphere in a potentially harmful form.

Secondary pollutants are formed when primary pollutants react with one another or with basic components of the air to form new pollutants.

Photochemical smog (brown-air smog) - A mixture of primary and secondary pollutants formed under the influence of sunlight.

Industrial smog (gray-air smog) ­ Largely sulfur oxides and particulates (smoke) from burning fuels.

Some Major Air Pollutants

Pollutant	Class	Primary/Secondary	Characteristics
Dust	particulate	primary	solid particles
Lead	particulate	primary	solid particles
Sulfuric Acid	particulate	secondary	liquid droplets
Nitrogen dioxide	nitrogen oxide	primary	gas, redish brown color
Sulfur dioxide	sulfur oxide	primary	colorless gas with strong odor
Carbon monoxide	carbon oxide	primary	colorless, odorless gas
Carbon dioxide	carbon oxide	primary	colorless, odorless gas
Methane	hydrocarbon	primary	colorless, odorless gas
Benzene	hydrocarbon	primary	liquid with sweet smell
Chlorine	air toxic	primary	yellow-green gas
Ozone	photochemical oxidant	secondary	pale blue gas with sweet smell

Regional Outdoor Air Pollution from Acid Deposition

Tall smokestacks on coal-burning power plants, smelters, and other industrial plants emit oxides and particulates above the inversion layer and are dispersed by the wind. While local air pollution may be decreased, general air pollution downwind is increased.

Acid deposition in the United States is a particular problem in the Northeast, Appalachians, and the mountains to the east of Los Angeles, California. It also is a problem in southeastern Canada and western Europe. Acid deposition is particularly bad in China which gets some 73% of its energy from burning coal.

Health and Economic Effects

Contributes to human respiratory diseases

Can leach toxic metals from water pipes into drinking water

Damages buildings, statues, metals, car finishes, etc.

Decreases atmospheric visibility

Lowers profits and causes job losses because of lower productivity in fisheries, forests, and farms

Environmental Effects

Loss of fish populations

Contamination of lakes and streams

Damages plants

Leaches plant nutrients from soils

Lowers crop productivity

Kills or weakens trees

FYI

According to the EPA, gas powered mowers, blowers, and other small-engine machines produce 10% of the air pollution in the U.S.

On a per-horsepower basis, one hour of mowing with a gas powered mower relaeases as many hydrocarbons as a car driven 50 miles.

When refueling lawn equipment, users spill an estimated 17 million gallons of fuel each year, which is 6 million gallons more than that released in the Exxon Valdez spill.