Air pollution occurs when harmful or excessive quantities of substances including gases, particles, and biological molecules are introduced into Earth’s atmosphere.
It may cause diseases, allergies and even death to humans; it may also cause harm to other living organisms such as animals and food crops, and may damage the natural or built environment.
Both human activity and natural processes can generate air pollution.
It is typically separated into two categories: outdoor air pollution and indoor air pollution.
Outdoor Air Pollution
It involves exposures that take place outside of the built environment. Examples include:
- Fine particles produced by the burning of fossil fuels (i.e. the coal and petroleum used in energy production)
- Noxious gases (sulfur dioxide, nitrogen oxides, carbon monoxide, chemical vapors, etc.)
- Ground-level ozone (a reactive form of oxygen and a primary component of urban smog)
- Tobacco Smoke
Indoor Air Pollution
It involves exposures to particulates, carbon oxides, and other pollutants carried by indoor air or dust. Examples include:
- Gases (carbon monoxide, radon, etc.)
- Household products and chemicals
- Building materials (asbestos, formaldehyde, lead, etc.)
- Outdoor indoor allergens (cockroach and mouse dropping, etc.)
- Tobacco smoke
- Mold and pollen
In some instances, outdoor air pollution can make its way indoors by way of open windows, doors, ventilation, etc.
What Causes Air Pollution?
“Most air pollution comes from energy use and production,” says John Walke , director of the Clean Air Project, part of the Climate and Clean Air program at NRDC.
“Burning fossil fuels releases gases and chemicals into the air.” And in an especially destructive feedback loop, air pollution not only contributes to climate change but is also exacerbated by it. “Air pollution in the form of carbon dioxide and methane raises the earth’s temperature,” Walke says.
“Another type of air pollution is then worsened by that increased heat: Smog forms when the weather is warmer and there’s more ultraviolet radiation.”
Climate change also increases the production of allergenic air pollutants including mold (thanks to damp conditions caused by extreme weather and increased flooding) and pollen (due to a longer pollen season and more pollen production).