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Air pollution

Air pollution is a broad term applied to all chemical and biological agents that modify the natural characteristics of the atmosphere.

Some definitions also consider physical perturbations such as noise pollution, heat, radiation or light pollution as air pollution. Some definitions include the term harmful as a requisite to consider a change to the atmosphere as pollution.

Table of contents
1 Causes
2 Contaminants
3 Further Reading
4 Sources


The sources of air pollution are divided in two groups: anthropogenic (caused by human activity) and natural.

Natural sources include:

Anthropogenic sources are mostly related to burning different kinds of fuel. They include:


Contaminants of air can be divided in particles and gases.

Particles are classified by their sizes. A usual division is in PM10 and PM2.5. PM10 are particles whose size is less than 10 microns (0.01 mm); they are dangerous to humans because they can be breathed and reach the lungs. PM2.5 are particles whose size is less than 2.5 microns (0.0025 mm), and they are even more dangerous because they can pass the alveoli and reach the blood.

Important pollutant gases include:

The worst single incident of air pollution to occur in the United States occurred in Donora, Pennsylvania in late October, 1948

See also:

Further Reading