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Update: May 2004

Current Massachusetts Regulatory Limit
For chlorinated
supplies only, the haloacetic acids MMCL = 0.060 mg/L and is the sum of the concentrations of mono-, di-, and trichloroacetic acids and mono-and dibromoacetic acids

Federal Regulatory Limit
Under its Disinfectants and Disinfection Byproducts Rule (Federal Register, December 16, 1998 - Volume 63, Number 241), U.S. EPA set the MCL for haloacetic acids at 0.060 mg/L. U.S. EPA did not set a Maximum Contaminant Level Goal (MCLG) for the group of haloacetic acids although there are MCLGs for some of the individual constituents, including dichloroacetic acid (zero) and trichloroacetic acid (0.3 mg/L). Monochloroacetic acid, bromoacetic acid, and dibromoacetic acid are regulated with this group but have no MCLGs.

Basis for Criteria
The five haloacetic acids (HAA5) are byproducts of the disinfection process. The MCL of 0.06 mg/L was set based on the potential for an increased risk of cancer (U.S. EPA, 1998a). U.S. EPA believes that by meeting MCLs for HAA5 and total trihalomethanes (TTHM) (other disinfection byproducts), water suppliers will also control the formation of other disinfection byproducts not currently regulated that may also adversely affect human health (U.S. EPA, 2002).

Critical Effects
Results from toxicology studies indicate that several disinfection byproducts (including the HAA5 chemicals dichloroacetic acid and trichloroacetic acid) may be carcinogenic in laboratory animals. Exposure to other disinfection byproducts, including several HAA5 has also been associated with adverse reproductive or developmental effects in laboratory animals (U.S. EPA, 1998b).

Cancer Assessment:
U.S. EPA has not conducted a cancer assessment for the HAA5s. However, several of the individual HAA5 constituents have been evaluated and qualitative descriptors of their carcinogenicity are provided below.

  • Information for monochloroacetic acid is inadequate for assessment of human carcinogenic potential.
  • Dichloroacetic acid is likely to be a carcinogen to humans.
  • There is suggestive evidence that trichloroacetic acid is carcinogenic. (U.S. EPA, 2004)

Disinfection Byproducts

Analytical Information
: See specific method. (57 FR 31776: 7-17-92)

Analytical Methods
U.S. EPA Method 552.1; 552.2; Standard Method 6251 B (U.S. EPA, 1998)

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.

Please note that there are individual RfDs and Health Advisories for some of the individual constituents of the HAA5s. 

U.S. EPA (U.S. Environmental Protection Agency). December 16, 1998a. National Primary Drinking Water Regulations. Disinfectants and Disinfection Byproducts. Final Rule. Fed. Reg. 63:241:69406.

U.S. EPA (U.S. Environmental Protection Agency). December 1998b. Stage 1 Disinfectants and Disinfection Byproducts Rule. U.S. EPA 815-F-98-010.

U.S. EPA (U.S. Environmental Protection Agency). July 2002. List of Contaminants and Their MCLs. U.S. EPA 816-F-02-013.

U.S. EPA (U.S. Environmental Protection Agency). Winter 2004. 2004 Edition of the Drinking Water Standards and Health Advisories.