Ms. Hoang is an Environmental Scientist with GSI Environmental, with expertise in chemical exposure and human health risk assessment. She received a M.S. in Environmental Health, with a specialty in Industrial Hygiene, from the University of California at Berkeley. Ms. Hoang's research experience includes evaluating chemical hazards from occupational processes, environmental media, commercial and residential buildings, consumer products, and food. She has worked on PFAS projects involving AFFF in drinking water, manufacturing releases, coatings in consumer products, and has evaluated the health risks from food chain transfer of PFAS from biosolids used to grow crops and homegrown produce.
Health Risk Assessment of Ingested per- and Polyfluoroalkyl Substances in Meat and Milk of Cattle Fed Crops Grown on Biosolids-Amended Soil
The land application of biosolids has received intense public and regulatory scrutiny in recent months due to concerns over environmental contamination and human exposure to per- and polyfluoroalkyl substances (PFAS). At environmental pH, terminally stable perfluoroalkyl acids like PFOA, PFOS, and PFHxS exist as anions that are soluble, mobile, and able to migrate from soils to plants. When animals ingest crops grown on biosolids-amended soil, PFAS can transfer from plants to animal tissue, and ultimately to humans that ingest animal products. We evaluated the potential health effects to humans that consume meat and milk from cows fed crops grown on biosolids-amended soil. The calculations utilized both measured and modeled plant concentrations of PFAS to predict meat and milk concentrations of PFAS that could be ingested by humans. Our objective was to determine whether the long-term land application of PFAS-containing biosolids may pose human health concerns when livestock are fed crops grown on biosolids-amended soil. We calculated concentrations of PFAS in the meat and milk of dairy cattle based on site-specific measurements of PFAS in soil at a farm where land-application of Class A biosolids has been practiced for years. These calculations utilized plant transfer factors to estimate PFAS concentrations in crops; crop concentrations were used with plant-to-meat and plant-to-milk transfer factors to calculate PFAS concentrations in the meat and milk of dairy cattle assumed to have been fed a diet consisting entirely of crops grown on the site. Parallel calculations of PFAS concentrations in meat and milk were completed based on site-specific measurements of PFAS in crops. Human exposure to PFAS was evaluated using both sets of meat and milk concentrations and a suite of exposure factors selected to provide upper-bound estimates of intake. Chemical-specific reference doses (RfDs) were used to assess potential health impacts from PFOS, PFOA, PFNA, PFHxS, PFHxA, and PFBS. Pathway-specific hazard quotients and cumulative hazard indices demonstrated that long-term daily ingestion of meat and/or milk from animals fed exclusively on crops grown on biosolids-amended soil does not present concerns for human health when PFAS are present in biosolids at concentrations consistent with those of our site. Our analyses also showed that measured PFAS concentrations in site soils show little to no evidence of PFAS accumulation at the site despite a 16-year history of biosolids land application. These results indicate that for the PFAS we evaluated at our site, the long-term use of PFAS-containing biosolids as a soil amendment for crops fed to livestock that are ultimately ingested by humans does not present a concern for human health.