Aerosols and Pollution Sources

Air contains not only gases but also solid particles and liquid droplets called aerosols. Natural examples include mineral dust, sea salt, pollen, spores, and wildfire smoke particles. Fuel burning by vehicles, power plants, and industry also emits soot and other particles or gases that form secondary aerosols in the air. These are important human-caused sources of air pollution, but their relative contribution depends on location, weather, and particle type; not all dust or pollen is human-caused pollution.