Perfluorooctanoic Acid Uptake by Alfalfa (Medicago sativa) and Bioavailability in Sprague-Dawley Rats

Perfluorooctanoic acid (PFOA) is a perfluorinated alkyl substance used as a surfactant in a wide variety of industrial and consumer products. Over the past decade, concern has increased over the presence of PFOA in biosolids from wastewater treatment plants used as fertilizer on agricultural lands because of the potential for PFOA to enter the food chain. In this study, the uptake of 14C-PFOA from soil by alfalfa and 14C-PFOA bioavailability from consumption of this alfalfa was evaluated in Sprague-Dawley rats. Alfalfa leaves accumulated 14C-PFOA up to 4 to 5 μg/g of dry leaf, approximately 10 times higher than accumulation in the stem. Alfalfa was ground for feeding to 15 female Sprague-Dawley rats (175 to 200 g). Animals within metabolism cages were fed 10 g of feed (6 g of alfalfa plus 4 g of ground rat chow) twice daily for 14 days (equivalent to 50 μg of 14C-PFOA per kg per day). At the end of the feeding period, three rats were euthanized for sample collection on each of withdrawal days 0, 3, 7, 11, and 14. During the feeding and withdrawal phases, urine and feces were collected daily. At necropsy, blood, liver, kidney, adipose, muscle, skin, brain, heart, adrenal glands, spleen, lungs, and thymus were removed and assayed for 14C-PFOA by combustion and liquid scintillation counting. Rats had eliminated 72.8% ± 3.4% of the total dose via urine at 14 days, but urinary radioactivity fell below the level of detection by day 3 of the withdrawal period. Fecal elimination was 6.5% ± 1.2% of the dose and fell below the level of detection by day 2 of the withdrawal period. The rapid and high elimination via urine indicates that a majority of the dose was absorbed. The uptake of 14C-PFOA into alfalfa was low from soil with a high organic concentration; however, 14C-PFOA was highly bioavailable from the alfalfa when used as a feed component for rats. This study provides data for regulators investigating 14C-PFOA bioavailability and disposition in animals or animal products exposed to contaminated feed.