A health protection goal for chloroform in drinking water may be loosened from zero to 0.3 milligrams per liter, according to a March 31 Environmental Protection Agency notice (63 FR 15674).
The suggested change for chloroform represents the first time EPA has set a health goal for a carcinogenic substance in drinking water at a level other than zero. The action was taken under the agency's new cancer risk assessment guidelines. EPA is asking for comments on the possible change.
The revised maximum contaminant level goal for chloroform, which is a nonenforceable goal, is based on a new assessment by EPA, according to the notice of data availability. The new assessment shows that there is a safe level of exposure to chloroform other than zero, according to EPA.
Although EPA is considering a less stringent MCLG for chloroform, which is a trihalomethane, the proposed maximum contaminant level for total trihalomethanes will not be loosened. EPA proposed in 1994 a 0.080 mg/L maximum contaminant level, while the current MCL is 0.10 mg/L. MCLs are not set separately for the four trihalomethanes: chloroform, bromodichloromethane, chlorodibromomethane, and bromoform.
MCLs, which are enforceable, are based on the MCLGs set by the agency.
The notice of data availability, which is similar to proposed rule, summarizes new health effects information for disinfectants and disinfection byproducts (D/DBP) received and analyzed by EPA since a previous notice in November 1997 (212 DEN A-1, 11/3/97). That 1997 notice summarized information that had become available since EPA proposed in July 1994 a Stage I disinfectants and disinfection byproducts rule (Stage I D/DBP) to reduce the level of exposure from these substances in drinking water. This 1994 proposal contained the tighter MCL for total trihalomethanes (114 DEN A-11, 6/29/94).
''This sets the precedent for EPA not using the default assumption of setting the MCLG for a carcinogen at zero,'' said Fred Pontius, with the American Water Works Association in Denver. ''The real question is, 'Will this open the door for doing so with other contaminants? What will this mean for arsenic and other contaminants such as radium 226 and 228?,' '' he asked. AWWA represents the water utilities regulated by the contaminant levels.
Sets a Precedent
Disinfection byproducts are compounds formed by the reaction of a disinfectant such as chlorine with organic material in the water supply. In recent years they have been suspected of causing adverse health effects, but health effects data on the disinfection byproducts have been limited.
Under the Safe Drinking Water Act Amendments of 1996, the Stage I Disinfectant and Disinfection rule must be made final by November 1998. A Stage II D/DBP rule must be final by May 2002. The Stage II rule will incorporate data from an earlier information collection rule and new research data.
The agency is developing a package of rules to balance the control of health risks from these compounds against the risk from microbial organisms such as giardia lamblia, cryptosporidium, bacteria, and viruses that are controlled by disinfection.
In other key issues in the recent notice, EPA said it is considering changing the proposed maximum contaminant level goal for chlorite from 0.08 milligrams per liter to 0.8 mg/L based on new information since 1994. The agency also is considering changing the proposed maximum residual disinfectant level goal for chlorine dioxide from 0.3 mg/L to 0.8 mg/L. Maximum residual disinfectant levels are similar in concept to maximum contaminant levels--MCLs set limits on contaminants and MRDLs set limits on residual disinfectants in the distribution system. MRDLs are enforceable by EPA.
Other Key Issues
EPA said it is considering maintaining the current maximum contaminant level goal of zero for dichloroacetic acid and an MCLG of zero for bromate as in the 1994 rule
The Stage I D/DBP rule would apply to community water systems and nontransient noncommunity water systems that treat their water with a chemical disinfectant for either primary or residual treatment. A community water system is defined by EPA as a public water system that serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. A noncommunity nontransient system is defined as a public water system that regularly serves at least 25 of the same nonresidents per day for more than six months per year.
In addition, certain requirements for chlorine dioxide would apply to transient noncommunity water systems because of the short-term health effects from high levels of chlorine dioxide, according to EPA.
In other changes in the March 31 notice, EPA updated health effects information. Relying on new studies, the agency estimated that of 54,500 bladder cancer cases per year nationwide, about 2 percent to 17 percent could be associated with DBPs in chlorinated water.
Health Effects Data
The agency also included the results of a California study released in February that showed a possible link between DBPs and miscarriages in pregnant women (30 DEN A-3, 2/13/98). ''EPA believes that while this study does not prove that exposure to [trihalomethanes] causes early term miscarriages, it does provide important new information that needs to be pursued and that the study adds to the weight-of-evidence which suggests that exposure to DBPs may have an adverse effect on humans.''
EPA also requested comments on several issues related to the simultaneous compliance with the Stage I D/DBP rule with the proposed lead and copper rule. In comments on the 1997 notice of data availability, some utilities had expressed concerns over their ability simultaneously to comply with both.
Comments (an original and three copies) should be sent by April 30 to DBP NODA Docket Clerk, Water Docket (MC-4101), EPA, 401 M St. S.W., Washington, D.C. 20460.
General information on the notice may be obtained by calling the Safe Drinking Water Hotline at 800 426-4791. Technical information may be obtained by calling Vicki Dellarco at (202) 260-7336 or Mike Cox at (202) 260-1445.
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