Six pollutants have been identified as particularly important indicators of air quality. They are:
- Ozone
- Carbon monoxide
- Nitrogen oxides
- Sulfur dioxide
- Small particles (ten microns or smaller)
- Lead
Of these pollutants, ozone is the compound of greatest concern for painting and coating operations. The formation of ozone can be triggered indirectly when paint solvents are released into the air.
Ozone high in the stratosphere protects the earth's surface from ultraviolet radiation from the sun, but ozone close to the ground is a highly irritating gas which can damage the lungs in very small quantities. Near the ground, ozone is formed when sunlight breaks down volatile organic compounds (VOCs) in the presence of nitrogen oxides. (Nitrogen oxides are formed in high temperature combustion, such as in power plants and internal combustion engines.)
VOCs can come from many sources, including paint solvents. The formation of ozone causes those solvents to have potentially harmful consequences at much lower concentrations than you might expect from the toxicity of the solvents themselves.
Because of the potential for solvent vapors to lead to the formation of ozone, painting and coating operations can be very stringently regulated in certain locations.
See EPA's webpage on the Six Common Air Pollutants.
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