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TA9 Ecological Risk Assessment and Landscape Ecological Modeling
() Application of Health-Based Screening Levels to a national assessment of VOCs in ambient ground water.
Toccalino, P1, Norman, J1, Phillips, R1, Zogorski, J2, Moran, M2, Wilber, W3, 1 Oregon Health & Science University, Beaverton, OR, USA2 U.S. Geological Survey, Rapid City, SD, USA3 U.S. Geological Survey, Reston, VA, USA
ABSTRACT- A national-scale pilot effort is underway to test an approach for communicating findings from the U.S. Geological Survey's (USGS) National Water-Quality Assessment (NAWQA) Program in a human-health context. Many aquifers sampled in the NAWQA Program are used as drinking-water sources, and water-quality conditions have historically been assessed by comparing measured contaminant concentrations to established drinking-water standards and guidelines. Because drinking-water standards and guidelines do not exist for many analyzed contaminants, Health-Based Screening Levels (HBSLs) were developed collaboratively by the USGS, U.S. Environmental Protection Agency (USEPA), New Jersey Department of Environmental Protection, and Oregon Health & Science University, using USEPA toxicity values and USEPA Office of Water methodologies. HBSLs are estimates of benchmark concentrations in water that: (a) may be of potential human-health concern, and (b) can be used as threshold values to which measured contaminant concentrations in ambient water can be compared. Ground-water samples collected during 1992-2001 from 394 public-supply, 1,978 domestic, and 1,748 monitoring wells were analyzed for 87 volatile organic compounds (VOCs). Measured VOC concentrations were compared to Maximum Contaminant Levels (MCLs) and HBSLs, when available. Benchmark Quotients (BQs), defined as ratios of measured VOC concentrations to MCLs and HBSLs, were calculated for each detected VOC with available USEPA toxicity values. The initial objective of this pilot effort is to identify VOCs of potential human-health interest in the Nation's ambient ground-water resources based on the magnitude and distribution of BQs and detection frequencies. Preliminary findings will be presented in the context of well type, regional patterns, and land use.
Key words: ground water, Health-Based Screening Level (HBSL), volatile organic compound (VOC), human health
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