Contaminants Resulting from Agriculture or Industry - Nitrate
Nitrate is a common contaminant of drinking
water closely associated with agricultural activities. Nitrate
in groundwater results primarily from fertilizer use (Gustafson,
1993). Fertilizer nitrogen that is not taken up by plants can
leach its way into the soil in the form of nitrate. Nitrate
(NO3) is a chemical ion, formed of one nitrogen atom and three
oxygen atoms. Nitrate, in itself, is not normally dangerous
to the human body except when it loses an oxygen atom, reducing
to nitrite (NO2).
Nitrate in drinking water is particularly dangerous to infants and small children. In proportion to their body weight, infants consume a much larger amount of water than older children and adults. Also, a baby’s immature digestive system facilitates the reduction of nitrate to nitrite much more easily than a mature, adult digestive tract. Nitrate ingestion, at or exceeding the MCL of 10 milligrams per liter, can lead to a disease called methemoglobinemia in infants. This disease occurs when reduced nitrite ions react with hemoglobin to form methemoglobin. This altered form of the blood protein is unable to carry oxygen to the body’s systems, leading to asphyxia in severe cases (Gustafson, 1993). Though, methemoglobinemia, as a result of nitrate-contaminated drinking water, usually occurs only in infants, women who are pregnant can be vulnerable to the disease, as well.
Nitrate, when contained in drinking water in extreme levels
(100-200 mg/l), can also cause cancer. Such high levels of nitrate
can react with protein compounds in the body to form nitrosamine,
a well-documented, cancer-causing agent. The main danger of
nitrate is to infants less than six months old.
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