About HBSLs

What are the benefits of using HBSLs?

  • The use of Health-Based Screening Levels (HBSLs) approximately doubles the number of human-health benchmarks available for unregulated compounds measured by the National Water-Quality Assessment (NAWQA) Program, increasing the number of compounds with benchmarks by 24%.
  • The most recent U.S. Environmental Protection Agency (USEPA) toxicity information is used to calculate HBSLs, therefore, HBSLs provide a mechanism for the timely incorporation of updated toxicity information in the interpretation of water-quality data.
  • HBSLs can be used as planning tools to help prioritize contaminants that may merit further study or monitoring and to provide an early indication of contaminant concentrations of potential human-health concern in water resources.
  • Because HBSLs supplement existing USEPA drinking-water standards and guidelines, they provide a basis for a more comprehensive evaluation of contaminant-occurrence data in a human-health context than by using USEPA benchmarks alone. Prior to the calculation of HBSLs for unregulated contaminants without existing drinking-water guideline values, the ability to evaluate the human-health context of their occurrence on a basis consistent with USEPA benchmarks was limited.