The Environmental Protection Agency has set certain National Ambient Air Quality Standards based on needs by The Clean Air Act, as part of its amendment in 1990. These needs were as a precautionary measure against different wide-spread pollutants from a variety of sources. These pollutants are considered harmful to the environment and the health of the general public. The National Ambient Air Quality Standards were set based on two types of national air quality standards determined by The Clean Air Act. These two types are primary standards and secondary standards.
Primary standards involves setting limits on pollutants that may be harmful to the health of the public and, in particular, individuals that are sensitive including children, asthmatics, elderly and others with respiratory ailments. Secondary standards sets limits on pollutants that may harm the welfare of the public as well as damaging crops, animals, vegetation, buildings and also protecting from visibility impairment. These National Ambient Air Quality Standards, however, are not set in stone as The Clean Air Act needs a review periodically of the criteria set in which these standards were set as well as the standards.
The process used in determining the National Ambient Air Quality Standards has also been revised and modified by the Environmental Protection Agency to include advice and reviews completed by the Clean Air Scientific Advisory Committee. Their determinations are based on an assessment report as to the risk or estimated risks of exposure that come from other alternative forms.
When the National Ambient Air Quality Standards were set by the Environmental Protection Agency (EPA), they were based on six major pollutants, which they referred to as “criteria” pollutants. These six pollutants include Carbon Monoxide (CO), Nitrogen Dioxide (NO2), Lead (Pb), Ozone (O3), Particulate Matter (PM) and Sulfur Dioxide (SO2).
Carbon monoxide is gas that is both odorless and colorless as well as being a poisonous gas when it’s in high levels. About 60% of the carbon monoxide emissions in the nation come as a result of the exhaust from motor vehicles. In certain cities, 95% of the CO comes from automobile exhausts. Other sources of CO are cigarette smoke, woodstoves, space heaters, industrial factories emitting fuel combustion and carbon black manufacturing. Lead is found in manufactured products such as motor vehicles and industries. The phasing out of leaded gasoline has helped control lead emissions a lot.
Although these two gases are the highest levels of the pollutants, all six of the above are determined to be dangerous and hazardous according to the National Ambient Air Quality Standards and are treated as such.