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Water: Stage 1 Disinfectant and Disinfection Byproduct Rule

Fact Sheet on the Stage 1 Disinfectants and Disinfection Byproducts Rule: New Health Effects Data Available

The Environmental Protection Agency has published a second Notice of Data Availability (NODA) in support of the proposed Drinking Water Stage 1 Disinfectants and Disinfection Byproducts (DBP) Rule. Several significant new pieces of health effects information have become available since the publication of the November 3, 1997 DBP Notice of Data Availability. EPA encourages public comment on the Agency's evaluation of the data. In addition, EPA is requesting comment on several issues related to the simultaneous compliance of the Stage 1 DBP rule and the Lead and Copper Rule. 

What changes to the 1994 proposed Disinfectants and Disinfection Byproducts Rule is EPA considering?
EPA is considering making the following revisions to the 1994 proposal and is requesting public comment.

  • Revising the Maximum Contaminant Level Goal (MCLG) for chlorite from 0.08 milligrams per Liter (mg/L) to 0.80 mg/L and the Maximum Residual Disinfection Level Goal (MRDLG) for chlorine dioxide from 0.3 mg/L to 0.8 mg/L.
  • Revising the MCLG for chloroform from zero to 0.30 mg/L.
  • EPA is also considering a new approach for estimating the potential upper bound cancer cases that can be attributed to exposure from DBPs in chlorinated water. This approach would change the estimated number of cases per year from 10,000 to a range of 1,100 -9,300.
The Maximum Contaminant Levels and Maximum Residual Disinfection Levels in the 1994 proposal, and confirmed in the 1997 FACA process, will not change.

What is the proposed Stage 1 Disinfectant and Disinfection Byproduct Rule?
The Stage 1 D/DBP Rule will strengthen control of chemical disinfectants and their potentially cancer-causing byproducts, in drinking water. The Safe Drinking Water Act, as amended in 1996, requires EPA to develop this rule as part of a group of standards which address the risk trade-offs between microbiological contaminants and disinfection byproducts. These rules, collectively called the microbial and disinfection byproducts (M/DBP) rules, are the first to address the waterborne pathogen, Cryptosporidium, in drinking water. The Stage 1 DBP Rule and the Interim Enhanced Surface Water Treatment Rule (IESWTR), proposed in July 1994, are expected to be finalized in November 1998.

Who has been involved in developing these rules?
To help meet the deadlines for the IESWTR and Stage 1 DPBR and to maximize stakeholder participation, in February 1997, the Microbial/Disinfection Byproducts Advisory Committee was established under the Federal Advisory Committee Act. The goal of the group was to collect, share and analyze new information and data, and to build consensus on the regulatory implications of this new information. The committee consists of 17 members representing EPA, state and local public health and regulatory agencies, local elected officials, drinking water suppliers, chemical and equipment manufacturers, and public interest groups.

How will the proposed rule strengthen control of disinfectants and DBPs?
Key components of the 1994 proposal include setting public health goals and enforceable standards for a variety of disinfection byproducts. The public health goals, which are not enforceable, are called Maximum Contaminant Level Goals (MCLGs) and Maximum Residual Disinfection Level Goals (MRDLGs). The enforceable standards are called Maximum Contaminant Levels (MCLs) and Maximum Residual Disinfection Levels (MRDLs). MRDLs set limits on residual disinfectants in the distribution system.

The proposal set MCLGs for chloroform, bromodichloromethane, bromoform, bromate, dichloroacetic acid, dibromochloromethane, trichloroacetic acid, chloral hydrate, and chlorite; lowered the existing MCL for total trihalomethanes (TTHMs); set an MCL for five haloacetic acids (HAA5) (ie., the sum of the concentrations of mono-, di-, and trichloroacetic acids and mono- and dibromoacetic acids); and set MRDLGs and MRDLs for chlorine, chloramine and chlorine dioxide. EPA also, for the first time, proposed MCLGs for two inorganic DBPs, bromate and chlorite.

The rule also identifies Best Available Technologies for compliance with the MCLs for TTHMs, HAA5, bromate, and chlorite; and with the MRDLs for chlorine, chloramine and chlorine dioxide. Additionally, the rule proposes a treatment technique that would require surface water systems and groundwater systems under the direct influence of surface water that use conventional treatment or precipitative softening to remove DBP precursors by enhanced coagulation or enhanced softening.

How do I comment on the NODA?
First, obtain and read a copy of the Notice of Data Availability. Read the notice online or request a copy from the Safe Drinking Water Hotline at 800-426-4791.

The notice was originally open for comment until April 30, 1998. EPA has reopened the comment period until June 8, 1998. Send written comments to: DBP NODA Docket Clerk, Water Docket (MC-4101), U.S. Environmental Protection Agency, 401 M Street, S.W., Washington, D.C. 20460. Submit electronic comments to ow-docket@epamail.epa.gov. Please use an unencrypted ASCII or Word Perfect format.

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