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Sex-, species-, and chain length-dependent renal elimination is the hallmark of mammalian elimination of perfluorocarboxylates (PFCAs) and has been extensively studied for almost 30 years. In this review, toxicokinetic data of PFCAs (chain lengths ranging from 4 to 10) in different species are compared with an emphasis on their relevance to renal elimination. PFCAs vary in their affinities to bind to serum albumins in plasma, which is an important factor in determining the renal clearance of PFCAs. PFCA-albumin binding has been well characterized and is summarized in this review. The mechanism of the sex-, species-, and chain length-dependent renal PFCA elimination is a research area that has gained continuous interest since the beginning of toxicological studies of PFCAs. It is now recognized that organic anion transport proteins play a key role in PFCA renal tubular reabsorption, a process that is sex-, species-, and chain length-dependent. Recent studies on the identification of PFCA renal transport proteins and characterization of their transport kinetics have greatly improved our understanding of the PFCA renal transport mechanism at the molecular level. A mathematical representation of this renal tubular reabsorption mechanism has been incorporated in physiologically based pharmacokinetic (PBPK) modeling of perfluorooctanoate (PFOA). Improvement of PBPK models in the future will require more accurate and quantitative characterization of renal transport pathways of PFCAs. To that end, a basolateral membrane efflux pathway for the reabsorption of PFCAs in the kidney is discussed in this review, which could provide a future research direction toward a better understanding of the mechanisms of PFCA renal elimination.

A high spatial and temporal resolution atmospheric model is used to evaluate the potential contribution of fluorotelomer alcohol (FTOH) and perfluorocarboxylate (PFCA) emissions associated with the manufacture, use, and disposal of DuPont fluorotelomer-based products in North America to air concentrations of FTOH, perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) in North America and the Canadian Arctic. A bottom-up emission inventory for PFCAs and FTOHs was developed from sales and product composition data. A detailed FTOH atmospheric degradation mechanism was developed to simulate FTOH degradation to PFCAs and model atmospheric transport of PFCAs and FTOHs. Modeled PFCA yields from FTOH degradation agree with experimental smog-chamber results supporting the degradation mechanism used. Estimated PFCA and FTOH air concentrations and PFCA deposition fluxes are compared to monitoring data and previous global modeling. Predicted FTOH air concentrations are generally in agreement with available monitoring data. Overall emissions from the global fluorotelomer industry are estimated to contribute approximately 1-2% of the PFCAs in North American rainfall, consistent with previous global emissions estimates. Emission calculations and modeling results indicate that atmospheric inputs of PFCAs in North America from fluorotelomer-based products will decline by an order of magnitude in the near future as a result of current industry commitments to reduce manufacturing emissions and lower the residual fluorotelomer alcohol raw material and trace PFCA product content.

Abstract: This study is the first to evaluate the rate of formation of perfluorooctanoate (PFO) from the aerobic biodegradation of a fluorotelomer-based urethane polymer and to use this information to assess the global environmental significance of this source. A fluorotelomer-based urethane polymer product test substance was studied in four aerobic soils over two years to determine the rate at which the fluorotelomer side-chains covalently bonded to the polymer backbone were cleaved and subsequently transformed to form the anions of perfluorocarboxylic acids including PFO. Over the two year duration of the experimental study, a polymer biodegradation half-life of 102 years (range: 28–241) was calculated for the urethane polymer based on regression analysis of the rate of PFO formation in four test soils. When this half-life was applied to the estimated total historic production, use and disposal of fluorotelomer-based urethane polymer, the annual potential global generation of PFO was estimated to be less than one tonne per year. [Copyright &y& Elsevier]