Biosolids Hazard Evaluation and Risk Assessments

Every farmer knows that growing crops takes patience, land, water, and fertilizer—sometimes in the form of biosolids that are applied in the fields. After twenty years of land application of biosolids, a farm in Southern California needed our help with litigation and asked us to perform a hazard evaluation and human health risk assessment. Litigation alleged that that trace chemicals, including perfluoroalkylated substances (PFAS), accumulate through repeated agricultural land application and may cause human and environmental health effects.

Our role? To determine whether there was a scientific basis for banning agricultural application of Class A-EQ biosolids, based on the allegations. We 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. Additionally, we provided our expertise to the technical review and strategic consulting on the potential for exposure and risk assessment issues associated with the litigation at this site.

With previously published data on PFAS plant uptake not readily available, our site-specific information on plant uptake allowed for a more refined risk assessment that demonstrated that there was no concern associated with using biosolids—our risk assessment work was key in assisting the client with their litigation.