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Earth and Space > Air Pollutants

Air pollutants arise from industrial, commercial and personal processes. Many are the result of burning fuels and processes involved in transportation and the manufacturing industries. The biggest air pollutants are listed below.

Pollutant Major Sources Notes
Carbon monoxide (CO) Motor-vehicle exhaust; some industrial processes Health standard: 10 mg/m3 (9 ppm) over 8 hr; 40 mg/m3 over 1 hr (35 ppm)
Sulfur dioxide (SO2) Heat and power generation facilities that use oil or coal containing sulfur; sulfuric acid plants Health standard: 80 µg/m3 (0.03 ppm) over a year; 365 µg/m3 over 24 hr (0.14 ppm)
Particulate matter Motor-vehicle exhaust; industrial processes; refuse incineration; heat and power generation; reaction of pollution gases in the atmosphere Health standard: 50 µg/m3 over a year; 150 µg/m3 over 24 hr; composed of carbon, nitrates, sulfates, and many metals including lead, copper, iron, and zinc
Lead (Pb) Motor-vehicle exhaust; lead smelters; battery plants Health standard: 1.5 µg/m3 over 3 months
Nitrogen dioxide (NO2) Motor-vehicle exhaust; heat and power generation; nitric acid; explosives; fertilizer plants Health standard: 100 µg/m3 (0.05 ppm) over a year; reacts with hydrocarbons and sunlight to form photochemical oxidants
Ozone (O3) Formed in the atmosphere by reaction of nitrogen oxides, hydrocarbons, and sunlight Health standard: 235 µg/m3 (0.12 ppm) over 1 hr