|HAKK, HELDUR - Retired ARS Employee|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2020
Publication Date: 11/24/2020
Citation: Lupton, S.J., Hakk, H. 2020. Perfluorooctanoic acid (PFOA) uptake by alfalfa (Medicago sativa) and bioavailability in Sprague-Dawley rats. Journal of Food Protection. 84:688–694. https://doi.org/10.4315/JFP-20-389.
Interpretive Summary: Perfluorooctanoic acid (PFOA), an industrial chemical used in the production of a wide range of products including Teflon® and Scotchgard™, is widely distributed in the environment. Municipal waste biosolids, which may contain relatively large quantities of PFOA, are sometimes spread on pastures and/or crop land. We reasoned that an important route of PFOA exposure in food animals may be the uptake of PFOA from soil by forages, and the subsequent ingestion of contaminated forage by livestock. Experiments were performed to measure the uptake of PFOA by alfalfa and to measure the transfer of PFOA from alfalfa into rat tissues. PFOA was transferred from soil to alfalfa stems and leaves, and PFOA was readily transferred to rats after ingestion of contaminated alfalfa. Although readily absorbed, PFOA was also rapidly excreted in urine of rats. This study demonstrated that PFOA in soil could serve as an exposure route for livestock if forage was grown on soil containing PFOA residue.
Technical Abstract: Perfluorooctanoic acid (PFOA) is a perfluorinated alkyl substance (PFAS) used as 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 having the potential to enter the food chain. In this study, the uptake of 14C-PFOA from soil by alfalfa was determined, as was the bioavailability of 14C-PFOA-incurred into alfalfa in Sprague-Dawley rats. Alfalfa leaves accumulated PFOA to as high as 4-5 ug/g of dry leaf, approximately 10 times higher than accumulation in the stem. Alfalfa was ground for feeding to 15 female Sprague-Dawley rats (175-200 g). Animals within metabolism cages were fed 10 g of feed (6 g alfalfa + 4 g ground rat chow) twice a day for 14 days (equivalent to 50 ug-PFOA/kg/day). At the end of the feeding period, rats (n=3) were sacrificed at withdrawal days of 0, 3, 7, 11, and 14 days. During the feeding and withdrawal phases, urine and feces were collected daily. At sacrifice, blood, liver, kidney, adipose, muscle, skin, brain, heart, adrenals, spleen, lungs, and thymus were removed and assayed for 14C-PFOA by combustion and LSC analysis. Rats eliminated 72.8 ± 3.4% of the total dose via urine at 14-days, but urinary radioactivity fell below the LOD by day 3 of the withdrawal period. Fecal elimination was 6.5 ± 1.2 % of the dose and fell below the LOD by 2 days of withdrawal. The rapid and high elimination via urine indicates that a majority of the dose was absorbed.