Nitrate (NO3) and Nitrite (NO2) are nitrogen-containing compounds that can be found in water and soils.  The presence of nitrate and nitrite generally indicates contamination from a pasture, manure pile, decomposed vegetation or agricultural fertilizers, or sewage, though it may come from erosion of natural deposits.

Nitrates change to nitrites in the body, which reduces oxygen uptake by the hemoglobin and could result in methaemoglobinaemia (blue baby syndrome), which is potentially fatal in infants.


Health Limits - Nitrate:

Maine Maximum Exposure Guideline limit: 10 mg/L
USA Primary Drinking Water Standard limit: 10 mg/L

Health Limits - Nitrite:

Maine Maximum Exposure Guideline limit: 1.0 mg/L
USA Primary Drinking Water Standard limit:  1.0 mg/L

Additional Resources:

Maine Division of Environmental Health, "Nitrate/Nitrite" (webpage)

USA CDC "Nitrate in Drinking Water" (webpage)

Water Quality Association Fact Sheet: "Nitrate/Nitrite" (2014, 6 pg. .pdf):

MEL Test Methods for Nitrate, Nitrite

Drinking Water – EPA Method 300.0 Rev. 2.1 (SDWA Compliant)
Wastewater –EPA Method 300.0 Rev. 2.1 (NPDES Compliant)
Solids & NPW –SW846 Method 9056A (SW846/RCRA Compliant)

Sample Requirements


Container: plastic, glass
Volume: 60 mL
Hold Time: 48 HOURS
Preservation: Cold, ≤6ºC


Container: plastic, glass
Volume: n/a
Hold Time: 14 days
Preservation: Cold, ≤6ºC

NPK 13.00.45 Fertilizer