What benchmarks are used to assess potential human-health effects?
Potential human-health effects are not directly assessed in this study, but a screening level assessment was done to identify and prioritize compounds that may warrant further investigation. To help place detections of compounds in a human-health context, annual mean concentrations were compared to the U.S. Environmental Protection Agency’s (USEPA) Maximum Contaminant Levels (MCLs) for regulated compounds, and to U.S. Geological Survey’s (USGS) Health-Based Screening Levels (HBSLs) for unregulated compounds. HBSLs are non-enforceable guidelines that were developed by the USGS in collaboration with USEPA and others using USEPA methodologies and the most current USEPA peer-reviewed, publicly available human-health risk assessments and toxicity information (see USGS Fact Sheet 2005-3059, and the Web site, USGS Health-Based Screening Levels.
