Nitrate in Drinking Water

🩨 Health Effects

Nitrate is acutely dangerous for infants under 6 months, causing methemoglobinemia ("blue baby syndrome") where the blood loses its ability to carry oxygen. For adults and older children, short-term exposure above the MCL may cause similar issues. Long-term exposure at lower levels is being studied for possible cancer links.

📍 Sources in Water

The primary source is agricultural fertilizer runoff, which enters groundwater and streams. Animal waste from feedlots and septic system leakage also contribute significantly. Nitrate is most common in rural agricultural areas and in surface-influenced groundwater.

✅ What To Do

Do not give tap water above the MCL to infants or use it to mix formula. Boiling does NOT remove nitrate; it concentrates it. Use bottled water or a reverse osmosis filter (NSF/ANSI 58 certified) for infant formula and drinking water. Pregnant women should also use caution.

📜 Regulation History

The EPA set the nitrate MCL at 10 mg/L (as nitrogen) under the original 1975 National Interim Primary Drinking Water Regulations, and it has remained unchanged. This standard was based on preventing infant methemoglobinemia. The WHO guideline is 50 mg/L as nitrate (equivalent to about 11.3 mg/L as nitrogen), slightly less strict than the US standard.

🔬 How To Test Your Water

Home test strips for nitrate are widely available for $10-$20 and provide a quick screening. For a definitive result, send a sample to a state-certified lab ($15-$30). Private well owners in agricultural areas should test annually, especially in spring after fertilizer application.

💧 Which Filters Remove Nitrate?

Reverse osmosis (NSF/ANSI 58 certified) is the most effective home treatment, removing 80-95% of nitrate. Ion exchange units designed for nitrate removal also work well. Standard carbon filters and water softeners do not remove nitrate; make sure any filter you purchase is specifically certified for nitrate reduction.

🔗 Related Contaminants