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USGS Updates Health-Based Screening Levels

This post was originally published on this site

The U.S. Geological Survey (USGS) National Water-Quality Program has updated information in its searchable online database of Health-Based Screening Levels (HBSLs) for sources of drinking water. All HBSL values in the database have been updated to reflect the U.S. Environmental Protection Agency’s (EPA) most recent methods and exposure assumptions for establishing drinking-water guidelines.

HBSLs are non-enforceable benchmark concentrations of contaminants in water. These screening levels supplement federal drinking-water standards and guidelines, which are not available for many of the hundreds of contaminants analyzed in sources of drinking water. Using HBSLs can provide a human-health context when evaluating the quality of sources of drinking water and help prioritize monitoring efforts.

As a result of the update, HBSLs were added, changed, or removed for 107 contaminants, including 4 contaminants for which HBSLs were replaced with new EPA Human Health Benchmarks for Pesticides (HHBPs). Altogether, this update increases the number of contaminants with HBSLs from 155 to 175.

The USGS database of more than 800 contaminants allows users to easily find information on drinking-water benchmarks and guidelines, and includes guidance on the use of benchmarks. For user convenience, the online HBSL database also provides current EPA drinking-water benchmarks (MCLs and HHBPs).