What Is Air Pollution?

Photograph of students listening to a NPS air resources division presenter during a field trip to Rocky Mountain NP, Colorado.
Students learn about air pollution impacts during a field trip to Rocky Mountain NP, Colorado.

NPS Photo

Air pollution consists of gasses, liquids, or particles in the air that can have serious effects on human health, wildlife, vegetation, lakes, streams, soils, and visibility in NPS areas. Whether an air pollutant is a problem depends on how much there is of it, how long it stays around, and in some cases weather.

The Environmental Protection Agency has set National Ambient Air Quality Standards for several pollutants in order to protect public health and the environment. These include fine particles, sulfur dioxide, nitrogen oxides, ground-level ozone, carbon monoxide, and lead.

Air pollutants of concern include:

  • Ground-level ozone forms near the Earth’s surface when volatile organic compounds (from gasoline, solvents, and vegetation) react with nitrogen oxide emissions in the presence of sunlight. This is different from the ozone layer in the upper atmosphere, which protects us from harmful ultraviolet radiation.
  • Sulfur and nitrogen compounds are produced by power plants and factories. Additional nitrogen pollution comes from cars and agricultural sources including crop fertilizer and animal waste.
  • Particle pollution comes from wind-blown dust and smoke from burning fossil fuels as well as forest and grassland fires.
  • Toxic compounds include metals (such as mercury) and chemicals (such as pesticides). Most human-caused mercury in the atmosphere comes from coal-burning power plants. Toxic chemicals come mainly from the production and use of agricultural and consumer products.
  • Greenhouse gases that contribute to human-caused climate change include carbon dioxide from burning fossil fuels and biomass, methane from livestock operations, black carbon from incomplete combustion, and even ground-level ozone.
Many NPS areas participate in ozone and particulate matter health advisory, conduct air quality monitoring programs, and support special studies that help increase understanding about the impacts of pollution in National Parks.

Last updated: April 2, 2018

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