The U.S. Environmental Protection Agency (EPA) finalized two related drinking water protection rules on Dec. 15 - one that reduces the risk of disease-causing microorganisms from entering water supplies and the other that requires water systems to limit the amount of potentially harmful disinfection byproducts (DBPs) that end up in drinking water.

Signed as EPA enters the 31st anniversary year for the Safe Drinking Water Act, the rules were proposed in August 2003, and were developed from consensus recommendations from a federal advisory committee comprised of state and local governments, tribes, environmental, public health and water industry groups.

"Clean drinking water is a key ingredient to keeping people healthy and our economy strong," says EPA administrator Stephen Johnson. "Over the past seven years, EPA has worked collaboratively with stakeholders to develop regulations that will provide a balance between the need to disinfect drinking water and protect citizens from potentially harmful contaminants."

The rules are important public health measures that will decrease the incidence of gastrointestinal illnesses caused by microbial contaminants and reduce potential cancer risks associated with disinfectant byproducts in drinking water. Finalizing the two rules represents the last phase of a congressionally required rulemaking strategy under the 1996 Amendments to the Safe Drinking Water Act.

Long Term 2 Enhanced Surface Water Treatment Rule

The Long Term 2 Enhanced Surface Water Treatment Rule (LT2) increases monitoring and treatment requirements for water systems that are prone to outbreaks of Cryptosporidium, a waterborne pathogen. Consuming water with Cryptosporidium causes gastrointestinal illness, which can be severe in people with weakened immune systems, such as infants or the elderly, and could be fatal in people with severely compromised immune systems, such as cancer and AIDS patients. LT2 will improve public health by reducing illness due to Cryptosporidium and other harmful microorganisms in drinking water.

The rule requires that public water systems that are supplied by surface water sources monitor for Cryptosporidium. Those water systems that measure higher levels of Cryptosporidium or do not filter their water must provide additional protection by using options from a "microbial toolbox" of treatment and management processes, such as ultraviolet disinfection and watershed control programs.

The rule also addresses risks of contamination in systems that store treated drinking water in open reservoirs, where water quality can be compromised by exposure to outdoor elements. The rule requires open reservoirs to either be covered or receive added treatment.

Stage 2 Disinfection Byproducts Rule

The Stage 2 Disinfection Byproducts Rule (Stage 2 DBP) was developed to balance the benefits and risks posed by drinking water disinfection. While disinfection is commonly known as one of the major public health advances of the 20th century, it also creates harmful byproducts that are formed when disinfectants, such as chlorine, combine with naturally occurring materials in water.

The final rule targets water systems that have the greatest risk of high DBPs by using more-stringent methods for determining compliance. Under the rule, water systems are required to find monitoring sites where higher levels of DBPs are likely to occur, and use these new locations for compliance monitoring. If DBPs are found to exceed drinking water standards at any of these new monitoring locations, water systems must begin to take corrective action.

The final rules will be published in the Federal Register in January. Pre-publication copies and additional information may be found on the EPA Web site at www.epa.gov/safewater/disinfection.