Revisions to the Unregulated Contaminant Monitoring Rule (UCMR 4) for Public Water Systems and Announcement of a Public Meeting

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The U.S. Environmental Protection Agency (EPA) is proposing a Safe Drinking Water Act (SDWA) rule that requires public water systems to collect occurrence data for contaminants that may be present in tap water but are not yet subject to EPA's drinking water standards set under SDWA. This rule, revised every five years as required by SDWA, benefits public health by providing EPA and other interested parties with scientifically valid data on the national occurrence of selected contaminants in drinking water, such as cyanotoxins associated with harmful algal blooms. This data set is one of the primary sources of information on occurrence, levels of exposure and population exposure the Agency uses to develop regulatory decisions for emerging contaminants in the public drinking water supply. This proposal identifies eleven analytical methods to support water system monitoring for a total of 30 chemical contaminants/groups, consisting of ten cyanotoxins/groups; two metals; eight pesticides plus one pesticide manufacturing byproduct (hereinafter collectively referred to as "pesticides"); three brominated haloacetic acid groups of disinfection byproducts; three alcohols; and three semivola