Population Reports' Q&As

Meeting the Urban Challenge

Pollution and Health

What are some of the major urban air pollutants?

• Suspended particulate matter and ozone are some of the major urban air pollutants. Suspended particulate matter-small particles floating in the air-is generated from natural sources, such as volcanoes and dust storms, as well as from human activities such as vehicle, incinerator, and industrial emissions. Due to their small size, suspended particulate matter tends to float longer in the air than larger particles, which usually settle quickly. Suspended particulate matter is small enough to be inhaled (57).
• Ozone is a secondary pollutant formed when oxides of nitrogen and unburned volatile organic hydrocarbons, mostly from vehicle exhausts, combine in the atmosphere with oxygen in the presence of sunlight. Ozone is a main component of atmospheric smog (not to be confused with the stratospheric ozone layer, which protects the earth from harmful ultraviolet radiation from the sun) (34, 47).

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