Major Elements of Six-Year Review
The major issues EPA considers in conducting the Six-Year Review of national primary drinking water regulations include the elements listed below. Select the links below to learn more about each review element, which can vary somewhat based on the type of contaminant.
- Initial Review is conducted to identify regulations for which a detailed technical review would not be appropriate in the current review cycle.
- Health Effects information is reviewed for drinking water contaminants to identify the national primary drinking water regulations for which there is potential to revise the maximum contaminant level goalThe maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non-enforceable health goals. (MCLG) and maximum contaminant levelThe highest level of a contaminant that is allowed in drinking water as delineated by the National Primary Drinking Water Regulations. These levels are based on consideration of health risks, technical feasibility of treatment, and cost-benefit analysis. (MCL).
- Contaminant Occurrence and Exposure Analysis information on the frequency, levels and geographic distribution of contaminants is analyzed to determine how changing an MCL or required treatment technique may affect health risks of water consumers and impact compliance costs for public water systems.
- Analytical Method Improvements are evaluated to determine whether there have been advances in laboratory technology to potentially enable a revision to the MCL for a regulated contaminant.
- Treatment Methods Feasibility review is conducted to ascertain there are technologies that could support a potentially lower MCL or a new treatment technique requirement.
- Risk-Balancing is conducted to address whether a change to an MCL and/or treatment technique will affect the risk from one or more other contaminants, and, if so, to consider revisions that will balance these overall risks.
- Implementation Issues are considered based upon EPA's or states’ experience in implementing the regulations as written.
More detailed information on all the issues EPA considers in developing Six-Year Review can be found in the EPA Protocol for the Fourth Six-Year Review support document.