Title: Absorption and excretion of 14C-perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in beef cattle Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2011
Publication Date: June 13, 2011
Citation: Lupton, S.J., Huwe, J.K., Smith, D.J., Dearfield, K., Johnston, J.J. 2011. Absorption and excretion of 14C-perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in beef cattle. 7th Annual LC/MS/MS Workshop on Environmental Application and Food Safety, June 13-14, 2011, Buffalo, NY. Technical Abstract: Perfluoroalkyl compounds such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are industrial chemicals that are environmentally persistent. Both PFOS and PFOA are found in biosolids, and the application of these contaminated biosolids to pastures has raised concerns about possible human exposure through the accumulation of PFOA and PFOS in edible tissues of these animals. As such, the United States Department of Agriculture (USDA) has undertaken a study to determine the absorption, distribution, metabolism, and excretion of PFOA and PFOS in beef cattle following oral exposure. A study protocol was developed and approved by the Institutional Animal Care and Use and the USDA Radiation Safety Committees. Four Lowline Angus steers (281 – 366 kg) were given single oral bolus doses containing 14C-labeled PFOA (1 mg/kg, 0.6 mCi per steer) and unlabeled PFOS (10 mg/kg). Serum and plasma were collected from each steer prior to and at various intervals after dosing. Quantitative urine and fecal collections were made during the same period every day from each steer. Cattle were slaughtered 28 days after dosing. Radioactivity in the serum, plasma, and urine was determined by liquid scintillation counting (LSC) and in the feces and tissues by combustion analysis followed by LSC. PFOA and PFOS concentrations were determined by liquid chromatography-quadrupole time of flight mass spectrometry (LC-QToF). 14C-PFOA derived radioactivity was completely absorbed and excreted in the urine within 8 days of dosing (100.6 ± 3.3% of the dose). LC-QToF analysis confirmed that the majority of 14C was parent PFOA and not metabolites. Radiocarbon in blood and urine peaked between 24 and 36 hrs post dose. Minimal amounts of radioactivity were excreted in the feces (2-3%) and no PFOA derived radioactivity was detected in tissues. In contrast to PFOA, urinary excretion of PFOS was minimal (0.054 ± 0.0071% of the dose). PFOS in urine and plasma peaked about 2-3 days post-dose and remained elevated in urine and plasma through the course of the study. Studies in rodents and non-human primates have estimated PFOA half-lives of 10-30 d. One exception is female rats which have rapid urinary excretion rates with half lives of 3-5 hr. Our data indicated that PFOA is rapidly excreted by steers with a half-life of 24 hr and would be unlikely to accumulate in edible tissues. PFOS half-lives are longer than that of PFOA, for non-human primates it is estimated at 200 days and for humans it is on the order of years. PFOS levels in this study remained elevated indicating a half-life much longer than 28 days and that PFOS accumulation in edible tissues is likely. Tissues and feces from this study are currently being analyzed for PFOS.