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Posts for tag: methemoglobinemia


The health implications of exposure to nitrates in drinking water were first reported in the scientific literature by Comly in 1945 after observing ashen-gray skin discoloration known as cyanosis in infants in Iowa, where well water was used in formula preparation. Since then, most studies on the health effects of nitrates in drinking water have focused on infants because they are thought to be the most vulnerable to this exposure. More recent evaluations of the health implications of nitrates in drinking water have examined reproductive and developmental effects.

When the delicate balance of nitrogen compounds maintained in nature is tilted by diverse human activities such as fossil fuel combustion, use of nitrogen compounds in fertilizers, and the release of nitrogen in wastewater and the water cycle then the risk of exposure to higher than normal levels in our food or water occurs. The attendant risk of serious health concerns rise accordingly.

Four years after its formation in 1970 the Environmental Protection Agency (EPA) was directed by Congress to monitor the levels of contaminants at which no adverse health effects are likely to occur and acceptable for potable water in our communities called the Safe Drinking Water Act. The maximum contaminant level goals (MCLG) indexed and monitored by the EPA are determined by considering possible health risks from exposure over a lifetime ( Contaminants monitored are not limited to nitrates and nitrites alone and include any physical, chemical, biological or radiological substances or matter in water. The current standards for acceptable water levels of nitrates are skewed towards what is considered safe for infants.

The potential toxicity of nitrates in contaminated water is enhanced when it occurs or is changed to a peculiar state of combination with oxygen known as nitrite. This form is readily capable of effecting changes with the blood when ingested that make it difficult for the red blood cells to carry out their normal process of oxygen transport and delivery to the tissues. Cumulatively with continued exposure, the amount of red blood cells affected could rise to dangerous levels and cause symptoms affecting different body systems in diverse ways due to oxygen debt and asphyxiation at the cellular level within the body which leads to death without urgent treatment. Newborn infants are especially vulnerable to the effects of nitrites and nitrates. Their body chemistry harbors the conditions necessary for activation of these compounds within the gastrointestinal tract and setting off the cascade. Newborn exposure to higher than normal levels of nitrates and nitrites should be a clinical consideration in the infant with marked irritability without an identifiable cause, or ashen –gray skin discoloration when a credible environmental threat exists. Prompt medical attention should be sought immediately. This condition is known as methemoglobinemia.

The biochemical processes leading to formation of nitrites from ingested nitrates are different in older persons and their body systems offer more resilience and opportunities for detoxification by the body itself. These defense mechanisms in older persons can be overwhelmed when sustained exposure to higher than acceptable levels of nitrates occur. The risk to pregnant mothers has unfortunately been the focus of limited scientific scrutiny. Researchers in Bulgaria (Tabacova et al) in 1997 looked at pregnancy outcomes in a population of mothers selected from areas with high levels of nitrates in their environment and proven higher than acceptable levels of markers of nitrate and nitrite toxicity in body fluids. The results did show adverse outcomes in these pregnancies, however the small size of the population studied and problems factoring the necessary adjustments for confounding variables required by scientific orthodoxy limits the application of their results to general and diverse populations. Experimental animal studies using pigs and laboratory mice on nitrate or nitrite exposure and adverse reproductive and developmental outcomes provide moderate evidence for an association between exposure to nitrate and fetal loss, neonatal mortality, maternal toxicity, and decrease in number of litters and live births. However epidemiologic evidence for increased risk for adverse reproductive and developmental outcomes in humans from exposure to nitrate in drinking water is sparse as mentioned above but has not been completely excluded. 

A report published by the CDC in 1996 on a cluster of spontaneous abortions in LaGrange, Indiana, cited nitrate-contaminated water from private wells as the possible cause. The cases included a 35-year-old woman who experienced four consecutive miscarriages and a 37-year-old and a 20-year-old who each experienced one miscarriage. All three women lived within 1 mile of each other and were in the first trimester of pregnancy at the time of the miscarriages. Testing of the wells serving the homes of the women found nitrate to be the only elevated contaminant. The wells had nitrate levels over the MCL (maximum contaminant level) for the three women, respectively. Although these incidents of spontaneous abortion may have been related to the ingestion of nitrate contaminated drinking water, other possible explanations such as genetic defects in the fetuses and cluster by chance as in the study from Bulgaria could not be ruled out

Caution and avoidance of exposure is best in pregnant mothers when a credible environmental threat is identified as more research adds to the current body of medical knowledge on this subject.


This information is for educational purposes only and not a substitute for professional medical care or advice. Always follow your healthcare provider’s instructions.