National Water-Quality Assessment (NAWQA) Program

U.S. Geological Survey
Fact Sheet 2005-3059

Health-Based Screening Levels and their Application to Water-Quality Data

By P.L. Toccalino, J.S. Zogorski, and J.E. Norman

To supplement existing Federal drinking-water standards and guidelines, thereby providing a basis for a more comprehensive evaluation of contaminant-occurrence data in a human-health context, USGS began a collaborative project in 1998 with USEPA, the New Jersey Department of Environmental Protection, and the Oregon Health & Science University to calculate non-enforceable health-based screening levels. Screening levels were calculated for contaminants that do not have Maximum Contaminant Level values using a consensus approach that entailed (1) standard USEPA Office of Water methodologies (equations) for establishing Lifetime Health Advisory (LHA) and Risk-Specific Dose (RSD) values for the protection of human health, and (2) existing USEPA human-health toxicity information.

Table of Contents

Screening levels expand human-health context for NAWQA findings
Evaluating ground-water data in a human-health context in New Jersey
Plans for application at the National scale
Contacts for additional information
The NAWQA Program

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For further information about this report, contact the National Water-Quality Assessment Program office.

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