At levels exceeding the federal limit, nitrate can cause methemoglobinemia, also known as blue baby syndrome, where a child suffers from oxygen deprivation in the blood. Nitrate-contaminated water has been linked to adverse reproductive effects and changes in thyroid function. A 2010 study by the National Cancer Institute found that women consuming nitrate-contaminated water face a greater risk of thyroid cancer. A 2012 publication from the same group reported a link between nitrate intake and sub-clinical hypothyroidism in women.
According to the International Agency for Research on Cancer, once ingested, nitrate is converted into N-nitroso compounds such as nitrosamines and nitrosamides by bacteria in our digestive systems. These substances damage DNA and cause cancers in multiple animal species and different organs, including the stomach, bladder, colon, esophagus and blood.
Human epidemiological research linked nitrate intake from water with increased risk of cancer. A 2001 study led by Peter Weyer at the University of Iowa found an association between long-term nitrate exposures from drinking water and increased risks of bladder and ovarian cancers in women.
National Cancer Institute studies consistently find that ingestion of nitrate from drinking water, especially in the range of 5 to 10 mg/L, increases the risk of colon, kidney, ovarian and bladder cancers. These risks are highest for people with low vitamin C intake, high consumption of red meat and for smokers – all conditions that increase the formation of N-nitroso compounds in the body.
What Is Methemoglobinemia?
Methemoglobinemia is the most significant health problem associated with nitrate in drinking water. Blood contains an iron-based compound called hemoglobin, which carries oxygen. When nitrite is present, hemoglobin can be converted to methemoglobin, which cannot carry oxygen. In the blood of adults, enzymes continually convert methemoglobin back to hemoglobin, and methemoglobin levels normally do not exceed 1 percent. Newborn infants have lower levels of these enzymes, and their methemoglobin level is usually 1 to 2 percent. Anything above that level is considered methemoglobinemia.
Few clearcut symptoms are associated with methemoglobin levels between 1 and 10 percent. At higher levels, symptoms of cyanosis usually appear. Babies with this condition have bluish mucous membranes and may also have digestive and respiratory problems. At methemoglobin levels above 20 to 30 percent, the primary effects result from the blood's severely reduced oxygen-carrying capacity and are referred to as anoxia. At methemoglobin levels around 50 to 70 percent, brain damage or death can occur.
Once diagnosed, methemoglobinemia can be readily reversed, although with anoxia permanent damage may have occurred. Methemoglobinemia can be prevented by restricting consumption of nitrite and nitrate and by limiting the opportunities bacteria have to reduce nitrate in food to nitrite before consumption.
Consuming drinking water with nitrate levels near the drinking water standard does not normally increase the methemoglobin level of humans beyond infancy. Some individuals, however, may have increased susceptibility to methemoglobinemia due to exposure to antioxidant medications and chemicals, or other conditions that may inhibit the body's ability to reconvert methemoglobin to hemoglobin (such as pregnancy or certain rare diseases).
Nitrate in drinking water starts affecting the health of the general populace at levels in the range of 100 to 200 mg/l nitrate-N, but the effect on any given person depends on many factors, including other sources of nitrate and nitrite in the diet. Some of the nitrate consumed can be converted in the body to nitrite, which under appropriate circumstances can combine with amines (portions of protein molecules often found in foods, medications, cigarette smoke, decaying plants, soil, and sometimes water) to form nitrosamines, well- documented cancer-causing substances. So far, the only studies linking nitrate in drinking water with cancer have involved nitrate levels that are quite high (at or above 100-200 mg/l nitrate-N).
At Epic Water Filters several of our products were designed and tested to remove Nitrate from tap water.