PFASs are a family of synthetic chemicals containing a fully (per-) or partly (poly-) fluorinated carbon chain connected to a carboxylate, sulfonate, or other functional group. Our scientists' experience includes modeling the movement of PFAS from the primary impacted source through the environment, evaluating both direct and indirect exposure pathways, and using biomonitoring data to understand human exposures. In addition, we have developed toxicity values, performed dose response assessments and hazard evaluations for a variety of PFASs, and conducted historical exposure reconstructions.

Project Example: Hazard Evaluation and Human Health Risk Assessment for a Farm After Land Application of Biosolids

Project Overview: Cardno ChemRisk was asked to perform a hazard evaluation and human health risk assessment for a farm in Southern California after twenty years of land application of biosolids as part of litigation. The purpose of these assessments was to determine whether there was a scientific basis for banning agricultural application of Class A-EQ biosolids, based on the allegations that trace chemicals, including perfluoroalkylated substances (PFASs), accumulate through repeated agricultural land application and may cause human and environmental health effects.

Our Approach: For this project, Cardno ChemRisk performed a hazard evaluation and human health risk assessment for a farm in Southern California after twenty years of land application of biosolids. As part of this project, Cardno ChemRisk also designed and conducted some of the sampling for soil, biosolids, groundwater, irrigation water, and plant silage to provide site-specific values for the partitioning of PFAS from biosolids and soil into plants and irrigation water. As consulting experts, Cardno ChemRisk provided technical review and strategic consulting on the potential for exposure and risk assessment issues associated with the litigation at this site.

Our Value: Cardno ChemRisk has extensive experience using applied risk science to help fill data gaps associated with the novel risk assessment scenarios. Because of this experience, we advised our client on the utility of collecting site-specific data on the partitioning of PFAS to plants as part of the risk assessment. At the time, published data on PFAS plant uptake was not readily available and the site-specific information on plant uptake allowed for a more refined risk assessment that demonstrated that there was no concern associated with using biosolids. This risk assessment was key in assisting the client with this litigation.

Project Example: Emerging Contaminant Regulatory Toxicology Support for a Federal Agency

Project Overview: Cardno ChemRisk assisted a Federal agency with ongoing scientific projects for emerging contaminants including technical reviews, information research, strategic analysis, and development of recommendations and agency guidance. This project includes tasks related to PFAS risk evaluation activities undertaken by the U.S. EPA and state health agencies. To date, Cardno ChemRisk has developed a framework for the evaluation of agency risk evaluations of PFAS and other emerging contaminants and performed a technical review of recently developed state-level PFAS drinking water guidance values. Our team has also initiated work on a revised guidance document for the selection and/or derivation of toxicity values for remedial investigations and remedial action objectives.

Our Approach: In developing the framework for evaluation, Cardno ChemRisk staff incorporated previous experience and understanding of the risk assessment and risk characterization processes, drawing on existing agency and peer-reviewed guidance for best practices in the field. Using extant information as a baseline, our team provided a detailed protocol for assessing the potential hazard of emerging contaminants and the derivation of associated toxicity values. The guidance details key elements for review in hazard evaluation and toxicity value derivation, which include the selection of critical studies; selection of appropriate dose-response models; uncertainty factor selection; derivation of quantitative values including Reference Dose (RfD) or Reference Concentration (RfC), maximum contaminant level (MCL) calculations, and cancer slope factors; and evaluation of uncertainty and overall confidence in the methods and derived values. This framework is now being applied to ongoing reviews of state and EPA PFAS toxicity values.

Our Value: The Cardno ChemRisk team brings extensive experience in regulatory risk assessment and includes toxicologists with experience working in governmental health agencies and non-profit organizations. Further, the team has been evaluating the regulation of PFASs and other emerging contaminants for more than a decade, allowing for a deep understanding of the constantly-evolving scientific and policy questions surrounding these substances. This experience contributed to targeted frameworks and technical reviews that will be used to guide the agency’s overarching policies as well as specific site-based remedial strategies.