&EPA
United States
Environmental Protection
Agency
Office of Water
4603
EPA811-F-94-003
June 1994
 EPA Efforts to Reduce Risks from Microbial Contaminants
 and Disinfectants/Disinfection By-products
 Balancing Risks

    Public water systems use disinfection to kill
    harmful microbial contaminants that can cause
    illness, and may even be fatal for those with
    weak immune systems. However, disinfection
    and the resulting by-products also pose risks,
    including potential increases in cancer rates and
    liver and kidney damage. The challenge is to
    strike an appropriate balance between these
    two risks so that public health is adequately
    protected.
 Regulatory Negotiation

   To help meet this challenge, EPA convened a
    negotiating team in November 1992 to assess
    the risks and determine the most appropriate
    course of action. The negotiating team
    included representatives from:

     - Public water systems
     - State and local health agencies
     - Environmental organizations
     - Consumer groups
     - Federal, state, and local governments

   The negotiators agreed to a three-part pro-
    gram:
                         1.  Modest interim controls of disinfectants
                         and disinfection by-products (D/DBP). and
                         microbial contaminants

                         Based on existing data, interim controls were
                         determined for controlling D/DBPs and microbial
                         contaminants. These controls are being pro-
                         posed by EPA as a D/DBP rule and an en-
                         hanced surface water treatment (ESWT) rule for
                         microbial control.

                         Under the proposed D/DBP rule, communities
                         would be required to meet new standards for
                         disinfectants and disinfection by-products. The
                         existing standard for trihalomethanes would be
                         lowered and extended to cover all systems,
                         regardless of size. The rule would also establish
                         six new  maximum contaminant levels to control
                         excessive use of disinfectants and reduce by-
                         product formation.

                         The ESTW rule proposes a number of treatment
                         options for protecting water systems against
                         harmful protozoa, such as Giardia and
                         Cryptosporidium. and viruses. It would require
                         systems with poorer source water to provide
                         greater control than is currently required under
                         the existing surface water treatment regulation. A
                         sanitary survey would be required every five
                         years so that public water systems would peri-
                         odically evaluate the effectiveness of their
                         operations. The proposed rule would apply to
                         those systems serving 10,000 people or more;
                         however, the sanitary survey would also be
                         applicable to those systems serving less than
                         10,000 people.

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&EPA
United States
Environmental Protection
Agency
Office of Water
4603
EPA811-F-94-003
June 1994
 EPA Efforts to Reduce Risks from Microbial Contaminants
 and Disinfectants/Disinfection By-products
 Balancing Risks

    Public water systems use disinfection to kill
    harmful microbial contaminants that can cause
    illness, and may even be fatal for those with
    weak immune systems. However, disinfection
    and the resulting by-products also pose risks,
    including potential increases in cancer rates and
    liver and kidney damage. The challenge is to
    strike an appropriate balance between these
    two risks so that public health is adequately
    protected.
 Regulatory Negotiation

   To help meet this challenge, EPA convened a
    negotiating team in November 1992 to assess
    the risks and determine the most appropriate
    course of action. The negotiating team
    included representatives from:

     - Public water systems
     - State and local health agencies
     - Environmental organizations
     - Consumer groups
     - Federal, state, and local governments

   The negotiators agreed to a three-part pro-
    gram:
                         1. Modest interim controls of disinfectants
                         and disinfection by-products (D/DBP). and
                         microbial contaminants

                         Based on existing data, interim controls were
                         determined for controlling D/DBPs and microbial
                         contaminants. These controls are being pro-
                         posed by EPA as a D/DBP rule and an en-
                         hanced surface water treatment (ESWT) rule for
                         microbial control.

                         Under the proposed D/DBP rule, communities
                         would be required to meet new standards for
                         disinfectants and disinfection by-products.  The
                         existing standard for trihalomethanes would be
                         lowered and extended to cover all systems,
                         regardless of size. The rule would also establish
                         six new  maximum contaminant levels to control
                         excessive use  of disinfectants and reduce by-
                         product formation.

                         The ESTW rule proposes a number of treatment
                         options for protecting water systems against
                         harmful protozoa, such as Giardia and
                         Cryptosporidium. and viruses. It would require
                         systems with poorer source water to provide
                         greater control than is currently required under
                         the existing surface water treatment regulation. A
                         sanitary survey would be required every five
                         years so that public water systems would peri-
                         odically evaluate the effectiveness of their
                         operations. The proposed rule would apply to
                         those systems serving 10,000 people or more;
                         however, the sanitary survey would also be
                         applicable to those systems serving less than
                         10,000 people.

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