Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/25/2017
Publication Date: 8/20/2017
Citation: Lupton, S.J., Hakk, H. 2017. Perfluorooctanoic acid uptake by alfalfa (Medicago sativa) and subsequent bioavailability from feeding to Sprague-Dawley rats [abstract]. Dioxin 2017. August 20-25, 2017. Vancouver, Canada. Paper No. 9955.
Interpretive Summary: .
Technical Abstract: Perfluoroctanoic acid (PFOA) is a perfluorinated compound (PFC) used as a surfactant in industrial and consumer products such as coatings for paper and textile fabrics, fire-fighting foam, and household items . Over the past decade, concern has increased over the presence of PFOA in wastewater treatment plants and the biosolids from these plants which are used as fertilizer on agricultural lands . Use of biosolids could result in release of PFOA into the environment accompanied by transport through the soil and/or uptake by agricultural crops, such as alfalfa, that are used to feed livestock, which may then contaminate consumer food products. A study was undertaken to quantify the uptake of 14C-PFOA by alfalfa and also the bioavailability of 14C-PFOA from alfalfa in a model species, the Sprague-Dawley rat. Three planters (3 ft x 10 ft with a depth of 1.5 ft) containing a greenhouse soil (70-80% peat moss) mixed with 14C-PFOA to a final concentration of 5 mg/kg soil was used for planting. Alfalfa stem and leaves from weekly samplings were combusted and 14CO2 was quantified by liquid scintillation counting (LSC). Plants were harvested when buds were first observed, collections dried, and stored for use in the bioavailability feeding study. Leaf and stem concentrations of 14C-PFOA were determined separately, The leaves accumulated PFOA as high as 4-5 µg/g dry leaf, approximately 10 times higher than accumulation in the stem. The variable concentrations observed in the stems and leaves of alfalfa plants between cuttings during the experiment are similar to those measured in an uptake study by Stahl et al . Alfalfa harvests were combined and ground for feeding to 15 female Sprague-Dawley rats (175-200 g; SD rats). Animals were fed 10 g of feed (6 g alfalfa + 4 g ground rat chow) twice a day in metabolism cages for 14 days at 50 ug/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 entire feeding study, urine and feces collections were made daily. At sacrifice, tissues (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. The rats eliminated 72.8 ± 3.4% of the chronic dose via urine over the 14 day feeding period, with urine concentrations falling below the LOD within 3 days after the start of the withdrawal period. Feces elimination was much less than urine (6.5 ± 1.2 % of the dose), once again levels fell below the LOD within 2 days of the start of the withdrawal period. The rapid and high elimination via urine indicates that a majority of the dose was absorbed, which is consistent with other exposure routes (i.e. gavage, intramuscular) . The remaining rat tissues are currently being analyzed.