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Bioaccessibility of Fipronil Sorbed to Soil and House Dust
Citation:
Starr, J., W. Li, S. Graham, Dan Stout, K. Bradham, AND B. Schumacher. Bioaccessibility of Fipronil Sorbed to Soil and House Dust. American Chemical Society National Meeting, Boston, MA, August 16 - 20, 2015.
Impact/Purpose:
The National Exposure Research Laboratory (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA mission to protect human health and the environment. HEASD research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
Fipronil is a phenylpyrazole insecticide with uses ranging from soil treatment, to the control of household pests and ectoparasites on pets. Soils and house dusts readily sorb fipronil and when these soils and dusts are ingested, the fipronil may become bioaccessible for uptake by the circulatory system.We measured the bioaccessibility of fipronil sorbed to 38 matched soil and house dust pairs collected during a national probabilistic survey of residential homes in the United States. Prior to performing the assay, we screened all samples to determine native concentrations of fipronil, its common metabolites, and the physicochemical properties of the soils and dusts. We used an in vitro, three- compartment human digestive (saliva, gastric, and intestinal) model to desorb the fipronil, and polyacrylate fibers to separate free fipronil from fipronil sorbed to dissolved organic content. Samples were analyzed using liquid chromatography- tandem mass spectrometry and we used linear regression to calculate the correlation of fipronil bioaccessibility with carbon content.The mean carbon content of the soils (3.1 ± 2.4%) was less than that of the dusts (18.6 ± 6.9%). The percent carbon in each dust sample was higher than its matched soil, however the percent carbon of matched soils and dusts was not correlated (p > 0.05). Fipronil bioaccessibility ranged from 10% to 98% and higher carbon in both soils and dust resulted in lower fipronil bioaccessibility. Fipronil bioaccessibility and carbon content were highly correlated in both dust (p < 0.0001) and soils (p < 0.0001). A bioaccessibility- carbon regression model that included both soils and dusts was also significant (p < 0.0001).In these samples, the carbon content of the house dust and soil samples predicted the bioaccessibility of fipronil. The higher carbon content of the dusts resulted in lower fipronil bioaccessibility compared to soils.
