Air Pollution


Learning Objective

  • Identify the four major effects of air pollution.

Key Points

    • Air pollution results from the introduction of harmful compounds into the atmosphere.
    • Pollutants are introduced from both natural and man-made sources.
    • Major pollutants include particulate matter, ozone, sulfur dioxides, and nitrogen dioxide.


  • acid rainacidic precipitation, the result of sulfur dioxide and nitrogen oxides reacting with water in the atmosphere

Air pollution is the presence of harmful molecules or particulates, both natural and man-made, in the atmosphere.

Effects of Air Pollution

Increases in these atmospheric molecules and particles result in:

  1. The greenhouse effect: an elevation in the Earth’s surface temperature due to the absorption of electromagnetic radiation by atmospheric gases.
  2. Decreased stratospheric ozone: a depletion in ozone levels caused by the release of refrigerants, which produce free radicals that catalyze the decomposition of ozone.
  3. Acid rain: acidic precipitation that occurs when the pollutants sulfur dioxide and nitrogen oxide react with water in the atmosphere.
  4. Increased ozone concentrations at ground levels: an increase in surface ozone that contributes to smog.
Air pollutionThe output of industrial manufacturing processes is a major source of air pollution.

Major Pollutants and Their Effects

The main air pollutants produced by humans are:

  1. Sulfur oxides (SOx)
  2. Nitrogen oxides (NOx)
  3. Carbon monoxide (CO)
  4. Carbon dioxide (CO2)
  5. Volatile organic compounds (VOCs)
  6. Particulates
  7. Free radicals
  8. Metals
  9. Chlorofluorocarbons (CFCs)
  10. Ammonia (NH3)
  11. Odors
  12. Radioactive compounds

Air pollutants are considered primary when the harmful particles are directly emitted into the atmosphere; secondary pollutants are products of reactions that occur following emission. Secondary pollutants include:

  1. Smog
  2. Ground level ozone (O3)
  3. Peroxyacetyl nitrate

Air pollution is also a problem indoors, where poor health has been linked to pollutants like radon, VOCs, lead paint, combustion particulates, carbon monoxide, and asbestos. Air pollution contributes to poor health through respiratory conditions, heart disease, and lung cancer. Approximately 3.3 million deaths worldwide are attributed to indoor and outdoor air pollution, with children in developing countries at particular risk for illness or disease.