Some possible sources of air pollution include:
- Mobile sources such as cars, buses, planes, trucks, and trains, which produce a significant amount of pollution, especially from automobile emissions. Mobile sources account for more than half of air pollution in places like the United States.
- Stationary sources such as power plants, oil refineries, industrial facilities, and factories that emit large amounts of pollution from a single location.
- Area sources including agricultural areas, cities, and wood-burning fireplaces that contribute collectively to air pollution.
- Natural sources such as wind-blown dust, wildfires, volcanoes, and pollen. These can sometimes be significant but usually do not cause ongoing pollution problems.
- Industrial activities like cement production, mining, plastic and rubber production, and construction, which cause particle and chemical pollution.
- Transportation emissions from road vehicles, diesel trains, ships, and planes.
- Household sources such as burning firewood, agricultural waste, coal, and charcoal for cooking and heating, as well as gas stoves and heating systems emitting pollutants indoors.
- Agricultural emissions including methane from cattle digestion and ammonia from fertilizers.
- Waste burning and microbial decay from open dumps, which release soot, methane, and other toxins.
- Photochemical reactions in the atmosphere causing secondary pollutants like ozone, formed from sunlight reacting with gases emitted by vehicles and industry.
These sources emit various harmful gases and particles including nitrogen oxides, sulfur dioxide, particulate matter (PM10, PM2.5), volatile organic compounds, carbon monoxide, benzene, and heavy metals, which contribute to smog, health problems, and environmental damage.
