What is the nitrate threshold in drinking water?

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Nitrates in drinking water are limited to protect infants from methemoglobinemia, a condition where nitrate is converted to nitrite in the body and reduces the blood’s ability to carry oxygen. Infants are most vulnerable due to their developing physiology, so a maximum level is set to keep water safe for all, especially bottle-fed babies. The standard limit used in many guidelines is 10 mg per liter as nitrate (NO3-). This value reflects a balance between practical water quality and protection from the potential health risk. Some guidelines report this as nitrate-nitrogen, which is a different unit but corresponds to the same safety goal; if you see nitrate-nitrogen, the numeric value will differ, but the protection level is equivalent. The other numbers are not used as the regulatory limit, since they don’t align with the established safety threshold.