Division of Environmental and Community Health

Maine Center for Disease Control & Prevention

A Division of the Maine Department of Health and Human Services

DHHSMeCDCEnvironmental and Community HealthDrinking WaterCompliance & EnforcementRegulated Contaminants → Nitrate/Nitrite

Nitrates and Nitrites

Page Index

Maximum Contaminant Level

Health Effects


Additional Resources

Nitrates and nitrites are nitrogen-oxygen chemical units that combine with various organic and inorganic compounds. They come from the breakdown of nitrogen compounds in the soil, where flowing ground water picks them up. High levels of nitrates and nitrites in groundwater are usually due to human activities, but can sometimes be found naturally in groundwater. The major sources of nitrates and nitrites in drinking water are runoff from fertilizer use, sewage – especially leakage from septic tanks – and erosion of natural deposits.


Maximum Contaminant Level (MCL)

The Environmental Protection Agency (EPA) has established the following standards for nitrate and nitrite in drinking water:

  • Nitrate:  10 ppm (milligrams per liter, mg/L)
  • Nitrite:  1 ppm (milligrams per liter, mg/L)

Health Effects of Nitrates and Nitrites

Drinking large amounts of nitrates and nitrites is particularly threatening to infants (for example, when mixed in formula). Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.



The following treatment method(s) have proven to be effective for removing nitrate to below 10 mg/L or 10 ppm:

  • Ion exchange
  • Reverse Osmosis
  • Electrodialysis

The Drinking Water Program recommends that water systems seek advice from a water treatment professional to determine the most effective treatment based on the characteristics of their specific water system. Contact your Public Water System Inspector before installing or making any changes to treatment in your public water system.


Additional Resources

Updated 2/10/2023