Table 1 Major sources of ambient air pollutants
From: DNA methylation: a potential mediator between air pollution and metabolic syndrome
Pollutant | Major sources |
|---|---|
Ozone (O3) | Formed from nitrogen oxide species and volatile organic compounds by human activities (largely the combustion of fossil fuel) |
Particulate matter (PM) | Naturally occurring, originates from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants, and various industrial processes also generate significant amounts of aerosols |
Carbon monoxide (CO) | Is a product of fuel combustion such as natural gas, coal, or wood. Vehicular exhaust contributes to the majority of carbon monoxide in the atmosphere |
Sulfur dioxide (SO2) | Is produced by volcanoes and in industrial processes. Combustion of coal and petroleum generates sulfur dioxide, as they often contain sulfur compounds |
Lead | Ore and metals processing and piston engine aircraft operating on leaded aviation fuel. Other sources include waste incinerators, utilities, and lead–acid battery manufacturers. The highest lead concentration in air is usually found near lead smelters |
Nitrogen dioxide (NO2) | Nitrogen dioxide is expelled from high-temperature combustion and is also produced during thunderstorms by electric discharge |
Polycyclic aromatic hydrocarbons (PAHs) | Are formed during the incomplete burning of coal, oil, gas, and tobacco |