Tropospheric Pollutants

Earth's atmosphere consists of five layers. The troposphere is the lowest layer. Its boundaries begin on the ground and extend to a height of about 23,000 to 65,000 feet above sea level. Pollutants trapped in the troposphere cause environmental damage and lead to serious health conditions.

Ozone

• Ozone, an oxygen gas, occurs naturally throughout the atmosphere. In the stratosphere, the ozone layer reduces the amount of ultraviolet radiation reaching the planet's surface; however, it becomes a pollutant in the troposphere. Ozone in the troposphere results from the interaction of ultraviolet light with nitrous oxides and hydrocarbons that are emitted by industrial processes and automobiles. According to the University Corporation for Atmospheric Research, this pollutant causes respiratory problems in people, damages crops and forests and destroys materials, such as rubber and nylon.

Greenhouse Gases

• Greenhouse gases are chemical compounds that absorb sunlight as it reflects off the Earth's surface and trap heat in the troposphere. These gases include carbon dioxide, nitrous oxides, methane and gases used in aerosols. The U.S. Energy Information Administration estimates that carbon dioxide emissions from the burning of fossil fuels account for about 82 percent of the nation's total greenhouse gas emissions. Landfills, fertilizers, coal mines and industrial processes release nitrous oxides and methane into the atmosphere. The accumulation of greenhouse gases in the troposphere results in rising temperatures on the surface, which causes changes in sea levels and weather patterns.

Carbon Monoxide

• Carbon monoxide is a colorless, odorless gas formed by the incomplete burning of carbon in fuel. The U.S. Environmental Protection Agency (EPA) estimates that motor vehicle exhaust produces approximately 56 percent of all carbon monoxide emissions in the U.S. Forest fires, residential wood burning and industrial processes, such as chemicals manufacturing, emit carbon monoxide into the troposphere. Carbon monoxide leads to serious health conditions, according to the EPA. It affects the central nervous system and the cardiovascular system. This pollutant also contributes to the formation of smog.

Nitrogen Oxides

• The breakdown of nitrogen gas in the troposphere produces nitrogen oxides, such as nitrogen dioxide and nitrogen monoxide. These pollutants result from lightning, vehicle exhaust and burning biomass. Catalytic converters installed in automobiles help decrease emissions of nitrogen oxides. These compounds react with water vapor to form nitric acid, a component of acid rain and contributor to the formation of the ozone hole in the stratosphere.

Sulfur Oxides

• Sulfur oxides are toxic compounds containing sulfur. They lead to respiratory problems in people, according to Windows to the Universe, an educational website of the National Earth Science Teachers Association (NESTA). Volcanoes and oil and coal combustion produce sulfur oxides. These pollutants combine with water vapor to create sulfuric acid, a component of acid rain.

Volatile Organic Compounds

• Volatile organic compounds, or VOCs, are organic compounds that exist in gaseous form in the lower atmosphere but are solids or liquids at normal temperatures and pressure. They result from human activities, such as agriculture, industrial processes, automobile exhaust, oil refining and solvent usage. Natural processes, including emissions from forest fires, trees, plants and wild animals, also release VOCs into the troposphere. VOCs contribute to stratospheric ozone depletion, smog formation and the greenhouse effect.