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Update: August 1992

Current Massachusetts Regulatory Limit
MMCL = 10 mg/L as the sum of nitrate and nitrite. ORS has adopted the MCL published by the U.S. EPA.

Federal Regulatory Limit
The MCL for nitrate/nitrite is equal to the MCLG of 10 mg/L.

Basis for Criteria
The MCLG for nitrate/nitrite is based on the potential for exposure to nitrate and nitrite greater than the MCLGs for the individual constituents to result in adverse health effects, in particular, methemoglobinemia. The value for the sum of nitrate and nitrite is established to be protective of infants and children.

Since both nitrate and nitrite result in methemoglobin toxicity, the toxicity of nitrate and nitrite may be additive. The joint standard was proposed to account for the possible additive toxicity of these two chemicals and also to protect against the deterioration of drinking water quality since the presence of nitrite in water is indicative of water contaminated with sewage. The combined standard does not replace the individual standards for nitrate and nitrite.

The individual MCLGs for nitrate and nitrite as well as the joint nitrate/nitrite MCLG were all derived based on the RfD presented below. Both the MCLGs for nitrate and nitrite were derived based on the RfD presented below and assuming that a 4 kg infant ingests 0.64 L of formula per day. Since the toxicity database for nitrite is much smaller than the toxicity database for nitrate and due to the demonstrated direct toxicity of this chemical, U.S. EPA applied an uncertainty factor of 10 to derive the nitrite MCLG (54 FR 22062). The joint standard is based on the consideration of data for the individual constituents.

RfD: 1.6 mg/kg/day
UF: 1 MF: 1

Chronic toxicity, developmental and reproductive toxicity were considered.

Critical Effects 
Methemoglobinemia in infants.

Nitrate in the human body is reduced to nitrite. Nitrite binds to hemoglobin and is responsible for the formation of methemoglobin which decreases the oxygen carrying capacity of the blood.

The RfD is based on information described by Walton (1951) from a survey conducted by the American Public Health Association (APHA) to identify clinical cases of infantile methemoglobinemia that were associated with ingestion of nitrate-contaminated water. Of a total of 214 cases of methemoglobinemia for which data were available on nitrate levels in water, none occurred in infants consuming water containing <10 mg nitrate-nitrogen/L (1.6 mg nitrate-nitrogen/kg/day).

Cancer Assessment: U.S. EPA has classified nitrate and nitrite as Group D carcinogens based upon inadequate data in animals and humans. A risk assessment is underway for these substances by the U.S. EPA.


Analytical Information
: 0.4 mg/l

Analytical Methods
300 ion selective electrode
353.1 Hydrazine Reduction
300 Ion Selective electrode

PQLs and analytical methods may have been updated since this guidance value was last revised. Updated analytical methods for drinking water and their associated PQLs may be found at US EPA Drinking Water Analytical Methods .

Other Regulatory Data
Any Health Advisories, Reference Doses (RfDs), cancer assessments or Cancer Potency Factors (CPFs) referenced in this document pertain to the derivation of the current guidance value. Updated information may be obtained from the following sources:

Health Advisories - The U.S. EPA provides guidance for shorter-term exposures for chemicals based on their non-cancer effects. Current health advisories may be more current than those used to derive MCLs and may be found at US EPA Current Drinking Water Health Advisories .

RfDs, cancer assessments and CPFs - For specific information pertaining to derivation of drinking water criteria, consult the Federal Register notice that announces the availability of the most current guidance for that chemical. In addition, information on other current RfDs and CPFs as well as cancer assessments for specific chemicals may be found in the U.S. EPA Integrated Risk Information System (IRIS) at Please note that the information in IRIS may differ from that used in the derivation process as published in the Federal Register notice.

Federal Register. November 13, 1985. Part IV. Environmental Protection Agency. 40 CFR Part 141. National Primary Drinking Water Regulations: Synthetic Organic Chemicals, Inorganic Chemicals and Microorganisms; Proposed Rule. (50 FR 46936).

Federal Register. May 22, 1989. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary and Secondary Drinking Water Regulations; Proposed Rule. (54 FR 22062).

Federal Register. January 30, 1991. Part II. Environmental Protection Agency. 40 CFR Parts 141, 142, and 143. National Primary Drinking Water Regulations; Final Rule. (56 FR 3526).

Walton, G. 1951. Survey of literature relating to infant methemoglobinemia due to nitrate contaminated water. Am. J. Public Health. 41:986-996.