The Maine Maximum Exposure Guidelines were established by the Maine CDC in 1984 and are updated every five years or so. They are similar to the EPA National Primary Drinking Water Standards in establishing limits for exposure to chemicals in drinking water. However, unlike the EPA standards, they are not legally enforceable, and they are based more on considerations of health than practical or political expediency.
The most recent edition was released in December, 2016, with changes to manganese, uranium, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Here’s a summary of the 2016 MEG updates: MEGchanges2016 (1 pg. .pdf)
Where do the Maine MEGs come from?
From the Maine CDC working document “Procedures for Developing Maximum Exposure Guidelines (2011, 9 pg.pdf)”:
The Maine Center for Disease Control and Prevention (MECDC) Environmental and Occupational Health Program (EOHP) develops Maximum Exposure Guidelines (MEGs) to assist risk managers, homeowners and others in making decisions regarding the suitability for human consumption of drinking water contaminated by chemicals.
MEGs are not promulgated by rule making and therefore are not issued as legally enforceable drinking water “standards.” Rather, MEGs represent the MECDC’s most recent recommendations for concentrations of chemical contaminants in drinking water below which there is minimal risk of a deleterious health effect resulting from long-term ingestion of contaminated water.
The MEGs are intended to be solely health-based guidelines, and do not take into account analytical methods, treatment technology, or economic impacts. This is in contrast to the legally enforceable drinking water standards called Maximum Contaminant Levels (MCLs). MCLs are promulgated under the Safe Drinking Water Act for the purpose of regulating public drinking water supplies, and allow for consideration of the technical and economic feasibility of attaining a standard. Most MCLs are promulgated as national standards by the U.S. Environmental Protection Agency (USEPA).