Absorption, Distribution, and Milk Secretion of the Perfluoroalkyl Acids PFBS, PFHxS, PFOS, and PFOA by Dairy Cows Fed Naturally Contaminated Feed

Abstract

The transfer of the perfluoroalkyl acids (PFAAs) perfluorobutanesulfonate (PFBS), perfluorohexanesulfonate (PFHxS), perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) from feed into tissue and milk of dairy cows was investigated. Holstein cows (n = 6) were fed a PFAA-contaminated feed for 28 days. After the PFAA-feeding period, three cows were slaughtered while the others were fed PFAA-free feed for another 21 days (depuration period). For PFAA analysis plasma, liver, kidney, and muscle tissue, urine, and milk were sampled and analyzed using high-performance liquid chromatography (HPLC) with tandem mass spectrometry (MS/MS). The average daily intake of dairy cows was 3.4 ± 0.7, 4.6 ± 1.0, 7.6 ± 3.7 and 2.0 ± 1.2 μg/kg body weight (bw) for PFBS, PFHxS, PFOS, and PFOA, respectively. Overall, PFBS, PFHxS, PFOS, and PFOA showed different kinetics in dairy cows. In plasma, concentrations of PFBS (mean = 1.2 ± 0.8 μg/L) and PFOA (mean = 8.5 ± 5.7 μg/L) were low, whereas PFHxS and PFOS continuously increased during the PFAA-feeding period up to maximal concentrations of 419 ± 172 and 1903 ± 525 μg/L, respectively. PFOS in plasma remained constantly high during the depuration period. PFOS levels were highest in liver, followed by kidney, without significant differences between feeding periods. The highest PFHxS levels were detected in liver and kidney of cows slaughtered on day 29 (61 ± 24 and 98 ± 31 μg/kg wet weight (ww)). The lowest PFAA levels were detected in muscle tissue. At the end of the feeding study, cumulative secretion in milk was determined for PFOS (14 ± 3.6%) and PFHxS (2.5 ± 0.2%). The other two chemicals were barely secreted into milk: PFBS (0.01 ± 0.02%) and PFOA (0.1 ± 0.06%). Overall, the kinetics of PFOA were similar to those of PFBS and substantially differed from those of PFHxS and PFOS. The very low concentration of PFBS in plasma and milk, the relatively high urinary excretion, and only traces of PFBS in liver (0.3 ± 0.3 μg/kg ww) and kidney (1.0 ± 0.3 μg/kg ww) support the conclusion that PFBS does not accumulate in the body of dairy cows.

Per- and polyfluorinated substances (PFASs): Environmental challenges

“…Angus cattle was a fast excreter for PFOA, with a 1 mg/kg bw dose being totally excreted (urine) within nine days [203], but not for PFOS, for which about one third of the dose (8 mg/kg bw ) was still present in the plasma after 28 days, thus becoming a potential exposure source for carnivorous humans [204]. Greatly different kinetics for PFOS and PFHxS versus PFOA and PFBA were confirmed in cows fed with contaminated feed [157]. PFOS serum half-life was 1-2 months in mice and rats, ~4 months in cynamolgus monkeys; liver/serum distribution ratios were different [205].…”

“…PFOA serum levels can then increase significantly with on-going drinking water exposure [26]. Cows, and hence, dairy milk are not sheltered against PFAS pollution [156,157].…”

Pathways and factors for food safety and food security at PFOS contaminated sites within a problem based learning approach

“…Accounting for the modeled animal exposure (ng kg À1 bw d À1 ) via water, forages, and top soil, the correspondent concentration in edible tissues (muscle, liver, milk) was derived from animal toxicokinetics data of feeding trials with contaminated grass silage and hay reported in sheep and cow by Kowalczyk et al (2012Kowalczyk et al ( , 2013, and from the observational study in dairy cows by Vestergren et al (2013). Carry-over rates (COR), as ratio between the total amount of PFOS in the tissue/milk of the considered farmed species and the total amount ingested by the animal were derived from the sheep study for liver (9.1), and muscle (11.6).…”

Occurrence of Perfluorooctanoic Acid and Perfluorooctane Sulfonate in Milk and Yogurt and Their Risk Assessment

“…Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are the two most frequently detected chemicals in blood and milk in the general population [10]. Because of their long elimination half-lives in humans (3.8 years for PFOA, 5.4 years for PFOS) [11], exploring the pathways of human exposure to these two compounds is necessary.…”