Risk assessment for perfluorooctanoic acid (PFOA) in air, blood serum and water: mortality from liver and kidney disease

Background Cancer and non-cancer associations have been observed with PFAS (perfluoroalkyl and polyfluoroalkyl) substances in the general population, in populations from locally contaminated environments and in exposed workers. Methods A quantitative risk assessment on the PFAS substance perfluorooctanoic acid (PFOA) was conducted for six outcomes using two occupational mortality studies that reported sufficient data to estimate exposure-relationships in relation to serum PFOA levels. Excess lifetime mortality risks were calculated using a life table procedure that applies an exposure response to time-dependent PFOA serum levels for a surviving hypothetical population from ages 20 to 85. Both occupational and general population exposures were described as serum levels, and as air and drinking water concentrations. Results The estimated occupational inhalation concentrations conferring the benchmark one-per-thousand lifetime risk were 0.21 µg/m 3 for chronic kidney disease, 1.0 µg/m 3 for kidney cancer and (from the two studies) 0.67 and 1.97 µg/m 3 for chronic liver disease. Specific excess lifetime risks estimated in the general population at current PFOA serum levels (~ 1 ng/mL) range 1.5–32 per 100 000 which corresponds to drinking water concentrations of less than 10 ppt. Conclusion Over eight outcome risk estimates, the serum PFOA concentrations conferring 1/1000 occupational lifetime risk ranged 44 to 416 ng/mL corresponding to air concentrations ranging 0.21 to 1.99 µg/m 3 . The analyses provide a preliminary PFOA quantitative risk assessment for liver and kidney disease mortality which, together with reported assessments for several other end-points, would inform policy on PFAS.