Those pollutants which have been identified by the Environmental Protection Agency (EPA) appearing to have the greatest threat to human health are known as, “Criteria Pollutants,” (Withcott & Laposata, 2012). They include, “carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, and lead,” (Withcott, 2012). The threat to human health of each of these pollutants is so great that the EPA has established a cap on the amount of concentrations which are permissible in the air outdoors.

The concern with carbon monoxide gas is that it may bond with the hemoglobin in human blood, effectively robbing the ability of hemoglobin to bond with oxygen (Withcott, 2012).

Sulfur dioxide is a by-product of coal combustion. This colorless may react with oxygen and the gas escapes into the atmosphere during combustion. Once airborne, sulfur dioxide may react to creat sulfur trioxide and sulfuric acid, eventually returning to earth in the form of acid rain, which is harmful to the environment (Withcott, 2012).

Nitrogen dioxide is an odoriferous gas which contributes to the formation of smog and acid deposits, both harmful to the human respiratory system (Withcott, 2012). Most of the nitrogen dioxide in the United States comes from combustion engine emissions. The remainder comes from industry (Withcott, 2012).

Tropospheric ozone is another colorless gas and is a major contributor to smog. Its harmful effects on humans comes from its oxygen component taking part in reactions which may cause damage to living tissue and respiratory issues. Tropospheric ozone is the pollutant which most often exceeds EPA standards (Withcott, 2012).

Particulate matter consists of airborne particles which if, inhaled, causes severe respiratory events. It contains dust particles, carbon, as well as secondary pollutants like nitrates and sulfates (Withcott, 2012).

Lead is another EPA-regulated pollutant that is extremely harmful to humans. It is introduced into the atmosphere as particulate matter through the emissions of internal combustion gasoline engines. Once it settles back on the earth or in water, lead can enter the food chain. When ingested, it can, “accumulate in body tissues, cause central nervous system malfunctions, birth defects, and developmental problems in children,” (Withcott, 2012).


Withcott, J. & Laposata, M. (2012). Essential environment: The science behind the stories (4th ed). Boston: Pearson.

Reply back to this discussion with 100 words count and APA format and citation. Mainly tell this person what a good job discussing the 6 criteria pollutants that the EPA focuses on and negatively affects human health. Elaborate on the 6 criteria as well.

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