Residue Distribution and Daily Exposure of Per- and Polyfluoroalkyl Substances in Indica and Japonica Rice

Per-and polyfluoroalkyl substances (PFAS) have excellent chemical stability but have adverse environmental impacts of concern. Furthermore, bioaccumulation of PFAS in rice varieties -which is the essential staple food crop in Asia -has not been verified. Therefore, we cultivated Indica (Kasalath) and Japonica rice (Koshihikari) in the same Andosol (volcanic ash soil) paddy field and analyzed the air, rainwater, irrigated water, soil, and rice plants for 32 PFAS residues, throughout the cultivation to human consumption. During the rice cultivation period, the cultivation environment in atmospheric particulate matter (PM) constituted perfluoroalkyl carboxylic acids (PFCAs), with minimal perfluorinated sulfonic acids (PFSAs). Furthermore, perfluorooctanesulfonic acid (PFOS) migrates at a PM > 10 to drop in a cultivation field and was conducive to leakage and accumulation of PFCAs in air particles in the field environment. Moreover, precipitation was a sources of irrigation water contamination, and cultivated soil with a high carbon content could capture PFSAs and PFCAs (over C₁₀). There were no major differences in residual PFAS trends in the rice varieties, but the distribution of PFAS in the growing soil, air, and rainwater differed. The edible white rice part was mainly affected by irrigation water in both varieties. Monte Carlo simulations of daily exposure assessments of PFOS, PFOA, and perfluorononanoic acid showed similar results for Indians consuming Indica rice and Japanese consuming Japonica rice. The results indicate that the ultratrace PFAS residue concentrations and their daily exposure were not cultivar-specific.

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