There are various activities or factors which are responsible for releasing pollutants into the atmosphere. Here is a short list.
Anthropogenic (or man-made) sources:
- Stationary sources include smoke stacks of power plants, manufacturing factories and waste incinerators.
Mobile sources include motor vehicles, marine vessels, and aircraft.
Controlled burn practices in agriculture and forest management.
- Fumes from paint, hair spray, varnish, aerosol sprays and other solvents
- Waste deposition in landfills, which generate methane.
- Military resources, such as nuclear weapons, toxic gases, germ warfare and rocketry.
- Dust from natural sources.
- Radon gas from radioactive decay within the Earth's crust.
- Vegetation, in some regions, emits environmentally significant amounts of VOCs on warmer days.
- Volcanic activity, which produces sulfur, chlorine, and ash particulates.