Are Nitrates in Drinking Water Harmful?
The EPA's maximum contaminant level for nitrate is 10 milligrams per liter, and its drinking water regulations list the sources as runoff from fertilizer use, leaking septic tanks, sewage and erosion of natural deposits.
ATSDR says exposure to nitrate and nitrite mainly occurs through food and water, and that most people are not exposed to levels that would cause health problems. It says some people who ate food or drank fluids with unusually high nitrite levels developed methemoglobinemia, a decreased ability of the blood to carry oxygen to tissues, and reports that IARC determined ingested nitrate and nitrite is probably carcinogenic to humans under stomach conditions that can produce cancer-causing N-nitroso compounds.
Private wells need testing. The CDC advises well owners to test their water at least once every year for total coliform bacteria, nitrates, total dissolved solids and pH.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Regulatory filingThe EPA says its maximum contaminant level for nitrate in groundwater used for drinking is 10 mg/l. US EPA ↗
- Regulatory filingThe EPA's drinking water regulations list nitrate sources as runoff from fertilizer use, leaking septic tanks, sewage and erosion of natural deposits. US EPA ↗
- Government sourceATSDR says exposure to nitrate and nitrite mainly occurs through food and water, and most people are not exposed to levels that would cause health problems. ATSDR, CDC ↗
- Government sourceATSDR says some people who ate or drank unusually high levels of nitrite experienced methemoglobinemia, a decreased ability of the blood to carry oxygen to tissues. ATSDR, CDC ↗
- Government sourceATSDR reports that IARC determined ingested nitrate and nitrite is probably carcinogenic to humans under conditions in the stomach that can produce cancer-causing N-nitroso compounds. ATSDR, CDC ↗
- Government sourceThe CDC advises testing well water at least once every year for total coliform bacteria, nitrates, total dissolved solids and pH level. CDC ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.