Tissue histology and depuration of per- and polyfluoroalkyl substances (PFAS) from dairy cattle with lifetime exposures to PFAS-contaminated drinking water and feed

Plasma, milk and tissue samples were collected from 30 dairy cattle (0.4 to 8.9 years of age) with lifetime exposures to perfluoroalkyl substances (PFAS) removed from a PFAS-contaminated farm and provided PFAS-free feed and water. Twenty cattle were slaughtered 2 weeks after removal from the farm and tissues were collected for histological and residue analyses. Milk and/or plasma were collected from all remaining cattle at 2-week intervals and milk samples were collected daily but were analyzed at the same intervals as plasma samples. The remaining cattle were slaughtered 20 and 22 weeks after the initial set of 20 animals were slaughtered. While many incidental and normal background findings were noted on histological evaluation, no consistent histological finding was associated with PFAS exposure. Perfluoroalkyl carboxylic acids (PFCA) and perfluoro butane sulfonic acid (PFBS) were not generally detected in milk, plasma and tissues, but perfluoroalkyl sulfonic acids (PFSA) were quantifiable throughout the 22-week withdrawal period in most matrices. Estimated plasma half-lives of perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), linear perfluorooctane sulfonic acid (L-PFOS), perfluoro-3-methyl heptanesulfonate (3Me-PFOS) and perfluoro-6-methyl heptanesulfonate (6Me-PFOS) ranged from 4 to 10 weeks, but the estimates were associated with large confidence intervals. Across animal status (heifer, lactating, dry), natural log transformed (Ln) plasma residues of PFHxS and L-PFOS were generally well correlated with Ln-transformed PFHxS and L-PFOS residues in lung, muscle, liver and kidney (R², 0.7572 to 0.9394) whereas the strongest relationships of Ln-transformed L-PFOS residues among tissues were between lung and liver, kidney and muscle (R², 0.8287 to 0.9138).