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CASRN: 10599903

Update: May 2004

Current Massachusetts Regulatory Limit
The MMCL is the MRDL 4 mg/L (monochloramine, measured as free chlorine). ORS has adopted the MRDL for chloramines published by the U.S. EPA. Although this standard is termed an MMCL, the basis of this value is still the U.S. EPA MRDL. [3] 

Federal Regulatory Limit
The Maximum Residual Disinfectant Level (MRDL) for chloramines of 4 mg/L (monochloramine measured as free chlorine) was established under the U.S. EPA's Disinfection Byproducts Rule (Federal Register, December 16, 1998 - Volume 63, Number 241). An MRDL is an enforceable standard, analogous to an MCL, which recognizes the benefit of adding a disinfectant to drinking water on a continuous basis and maintaining a residual to control for pathogens in the distribution system. The MRDL is set as close as feasible to the Maximum Residual Disinfection Level Goal (MRDLG). The MRDLG is a nonenforceable health goal based only on health effects and does not reflect the benefit of the addition of the chemical for control of waterborne microbial contaminants. The MRDL for chloramines is equal to the MRDLG for chloramines. 

Basis for Criteria
Chloramines are formed when chlorination is conducted in the presence of ammonia. U.S. EPA has set an MRDLG for chloramines of 4 mg/L, assuming a 70 kg adult ingests 2 L/day water, based on the RfD presented below.

RfD oral = 0.1 mg/kg/day (U.S. EPA, 1994; U.S. EPA, 1998)
UF: 100 (10 = interspecies; 10 = intraspecies)
MF: 1

The MRDLG is based on a NOAEL of 9.5 mg/kg/day for lack of toxicity in a chronic rodent drinking water study to which was applied an uncertainty factor of 100 to account for inter- and intra- species differences (U.S. EPA, 1994). Derivation of the MRDLG is: MRDLG = 0.1 mg/kg/day x 70 kg/2 L/day = 3.5 mg/L (4.0 mg/L).

Critical Effects
Although short-term single-dose exposures to chloramines in drinking water have not resulted in adverse effects in human subjects, in another study acute hemolytic anemia was reported in hemodialysis patients when tap water used for dialysis baths was disinfected with chloramines. Chloramines produced oxidant damage to red blood cells and inhibited the metabolic pathway used by red blood cells to prevent and repair such damages. Longer-term oral studies in rodents showed decrease body and organ weights, effects to the liver appearing to be related to decreased water consumption due to unpalatability of chloramines in water and a suggestion of immunotoxicity. Chloramines appear to be weakly mutagenic based on positive results in two bacterial assays (U.S. EPA, 1994). 

Cancer Assessment
U.S. EPA believes that the available cancer epidemiological data provides important information that contributes towards the weight-of-evidence evaluation of the potential health risks associated with chlorinated drinking water. However, U.S. EPA does not believe at this time that the cancer studies are sufficient to establish a causal relationship between exposure to chlorinated drinking water and cancer. 

disinfectant byproduct

Analytical Information

Analytical Methods
Free, combined, and total chlorine: ASTM Method D1253-86;
Standard Methods 4500-Cl D, 4500-Cl F and 4500-Cl G.
Total chlorine: Standard Methods 4500-Cl E and 4500-Cl I

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

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

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. December 16, 1998. Part IV. 40 CFR Parts 9, 141, and 142. National Primary Drinking Water Regulations. Disinfectants and Disinfection Byproducts. Final Rule. (63 FR 69390).

U.S. EPA. 1994. Draft Drinking Water Health Criteria Document for Chloramines. Office of Science and Technology. Office of Water.

[3] MRDL = maximum residual disinfectant level - the highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

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