Perfluorooctanoic acid (PFOA) transport in soil and absorption and distribution in alfalfa (Medicago sativa)

Authors: Lupton, Sara; CASEY, FRANCIS - North Dakota State University; Smith, David; Hakk, Heldur

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2021
Publication Date: 9/30/2021
Citation: Lupton, S.J., Casey, F., Smith, D.J., Hakk, H. 2021. Perfluorooctanoic acid (PFOA) transport in soil and absorption and distribution in alfalfa (Medicago sativa). Journal of Food Protection. 85:164-172. https://doi.org/10.4315/JFP-21-276.
DOI: https://doi.org/10.4315/JFP-21-276

Interpretive Summary: Perfluorooctanoic acid (PFOA), an industrial chemical used in the production of a wide range of products for surfactants and coatings, such as Teflon® and Scotchgard™, is widely distributed in the environment and found in humans and wildlife. Because municipal waste biosolids containing large quantities of PFOA are spread on cattle pastures and crop land annually, it was hypothesized that an important route of PFOA exposure for food animals may be the uptake of PFOA by crops and the subsequent ingestion of those crops by livestock. Experiments were performed to study the transport of PFOA through soil and it’s uptake by alfalfa plants, an important animal forage. PFOA was taken up into alfalfa roots, stems and leaves, and although uptake was rapid, it occurred at low levels. Downward soil transport of PFOA was decreased by the presence of alfalfa plants in the soil. The results demonstrated that PFOA in soil could potentially be an exposure route for livestock consuming forage grown on that soil.

Technical Abstract: Perfluorooctanoic acid (PFOA) has been extensively used as a surfactant in a variety of consumer and industrial products and is frequently found in biosolids from waste water treatment plants. When present in biosolids applied to croplands, PFOA has potential to contaminate feed and fodder used by livestock, but the extent of PFOA transfer from soil to plants is not well characterized. In this study, a single dose of [14C]-PFOA (4.97 mg/kg) was applied to unplanted soil or to soil containing growing alfalfa. [14C]-PFOA transport through unplanted soil and uptake by alfalfa roots, stems, and leaves was monitored over a 10-week study period. Radiocarbon was measured in roots, stems, and leaves 7 days after PFOA application to soil. The PFOA accumulation was greatest in the leaves throughout the 10-week sampling sequence. By week 10, PFOA peak migration through unplanted soil had reached a depth of 22.8 ± 2.5 cm. In contrast, PFOA had migrated to only 7.5 ± 2.5 cm in soil containing alfalfa plants. The greatest predictor of PFOA concentration in alfalfa leaves was PFOA concentration in the top 5 cm of soil; PFOA concentrations at lower depths were not correlated with alfalfa PFOA levels. The rate of PFOA transport through soil may be slowed by the presence of forage materials, however accumulation of PFOA in edible portions of forage plants may increase food animal exposure to PFOA residues.