Perfluorinated Compounds

To support an administrative hearing regarding a landfill expansion permit, Gradient evaluated potential impacts to groundwater and surface water quality near the landfill. We compared chemical concentrations in landfill leachate, groundwater monitoring wells, and nearby surface water with regulatory benchmarks. We used multiple lines of evidence, including an evaluation of the effectiveness of the landfill liner system and temporal evolution of PFAS concentrations in leachate, to estimate the scale of potential surface water impacts if the landfill was expanded.

Gradient conducted site research and evaluated the extent of perfluorinated alkyl substances (PFAS) at multiple locations throughout the US. Our evaluation included a review of potential PFAS transport from industrial facilities, landfills, and fire training areas to soil, groundwater, surface water, and sediment. Gradient also compiled information on remediation activities and water treatment systems.

Gradient wrote a white paper on the history of analytical method development for the analysis of per- and polyfluoroalky substances (PFAS) in environmental and biological matrices. The goal was to define the data quality standards relevant for different analytical methods, matrices and time periods.

In the context of setting drinking water limits, Gradient evaluated the scientific support for the commonly-used default assumption of 10 to 20% of exposure being attributable to drinking water (referred to as relative source contribution or RSC). We assessed the relative intakes of PFOS from various sources and evaluated the implications of alternative RSC values on PFOS drinking water guidelines. The analysis was presented at a toxicology conference.