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The United States Environmental Protection Agency's (USEPA) Regional Screening tables were recently updated. These Regional Screening tables are typically revised and posted twice per year. The Regional Screening Levels (RSLs) presented in these tables are risk-based concentrations that are derived from equations that take into account exposure assumptions, in addition to USEPA toxicity data. RSLs are used in the initial screening of contaminated sites, including Superfund sites, such that particular areas, contaminants, and conditions at the sites are identified and receive further attention from USEPA. The screening levels are considered to be protective of human health over a lifetime and do not consider any ecological risk endpoints.

As part of the update, the RSLs for several chemicals were adjusted to reflect changes in their toxicity values and chemical-specific parameters. Specifically, the inhalation unit risk for dibromochloromethane was deleted when it was withdrawn by Cal EPA. Additionally, toxicity values for nine chemicals were added, because these chemicals have new Provisional Peer-Reviewed Toxicity Values (PPRTV), 11 chemicals were changed from old Health Effects Assessment Summary Table (HEAST) toxicity values to updated PPRTV toxicity values, common chemical names for 24 pesticides were replaced with their technical names, and melting point values were added to the parameter table for all chemicals. Furthermore, all of the physicochemical parameter values were revised to be consistent with those used to determine the USEPA Vapor Intrusion Screening Levels (VISLs).