Nitrates & Nitrites in Drinking Water

The principle sources of nitrate contamination in water are thus fertilizers, animal waste and septic tanks. The water supplies most vulnerable to nitrate contamination are in agricultural areas and in well waters having a close or hydraulic relationship to septic tanks. Nitrate in drinking water can be responsible for a temporary blood disorder in infants called methemoglobinemia (blue baby syndrome).

Contaminant  In Water As Maximum Contaminant Level





MCL* = 10.0 mg/L (as N)
MCLG** (goal) = 10.0 mg/L (as N)

Health Canada MAC** = 10 mg/L (as N)

WHO† Guideline:
11.3 mg/L (as N)
50 mg/L (as NO3-1)



MCL*= 1.0 mg/L (as N)
MCLG** (goal) = 1.0 mg/L (as N)

Health Canada MAC*** = 1 mg/L (as N)

WHO† Guideline = 1 mg/L (as N)

Sources of Contaminant

  • Human sewage and livestock manure
  • Fertilizers
  • Erosion of natural deposits

Potential Health Effects

  • Methemoglobinemia (blue baby syndrome)
  • Most potential health effects are seen in infants under the age of 6 months

Treatment Methods

Point-of-Entry (POE)

Point-of-Use (POU)

  • Reverse Osmosis with thin film composite membrane
  • Anion Exchange (Type I and II, Cl- form, subject to competing sulfates)
  • Nitrate "Selective" Anion Exchange resins
  • Distillation
  • Electrodialysis

*Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

**Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

***MAC - Maximum Acceptable Concentration

WHO† - World Health Organization

Click here for national data on nitrate occurrence from the U.S. Geological Survey.

Click here to open WQA's Technical Fact Sheet on Nitrates and Nitrites.

Click here to access all of WQA's Technical Fact Sheets.