Nitrates in drinking water or food can pose several health risks, particularly when they are converted into nitrites in the body. Here are the key health effects associated with nitrates:

Methemoglobinemia (“Blue Baby Syndrome”): 

Nitrates can be reduced to nitrites in the body, which can bind to hemoglobin in the blood, reducing its ability to carry oxygen. This is especially dangerous for infants under six months old, as their digestive systems are more likely to convert nitrates to nitrites. The condition, known as methemoglobinemia, can cause symptoms such as shortness of breath, cyanosis (bluish skin), and, in severe cases, can be fatal if untreated.

Increased Cancer Risk: 

Long-term exposure to high levels of nitrates has been associated with an increased risk of certain cancers, particularly stomach and esophageal cancer. This is because nitrites can react with amines in the stomach to form nitrosamines, which are known carcinogens. While the evidence is not conclusive, studies suggest a potential link between chronic nitrate exposure and cancer.

Thyroid Dysfunction: 

High nitrate levels may interfere with iodine uptake by the thyroid gland, potentially leading to thyroid dysfunction, such as hypothyroidism. This can affect metabolism and overall hormonal balance, particularly with prolonged exposure.

Reproductive and Developmental Effects: 

Some studies suggest that high nitrate exposure may be linked to adverse reproductive outcomes, such as reduced fertility, and developmental issues in fetuses, including neural tube defects. However, more research is needed to establish a definitive connection.

Cardiovascular Effects: 

In some cases, elevated nitrate levels and the resulting nitrite formation can affect blood pressure and cardiovascular health. While low levels of nitrates from natural sources (like vegetables) may have a beneficial effect on blood pressure, excessive exposure from contaminated water sources can be harmful.

Vulnerable Populations:

Infants, pregnant women, and individuals with certain pre-existing conditions (e.g., reduced stomach acidity or specific enzyme deficiencies) are particularly susceptible to the adverse effects of nitrates. 

Regulatory Limits:

The U.S. Environmental Protection Agency (EPA) has set a maximum contaminant level (MCL) for nitrates in drinking water at 10 mg/L (measured as nitrogen) to protect against these health risks, particularly methemoglobinemia in infants. 

If you are concerned about nitrate exposure, it is advisable to test drinking water sources, especially in areas near agricultural activity or wastewater treatment facilities, and use appropriate filtration systems if necessary.