ISOMER-SPECIFIC ACCUMULATION OF PERFLUOROOCTANE SULFONATE IN THE LIVER OF CHICKEN EMBRYOS EXPOSED IN OVO TO A TECHNICAL MIXTURE

Prior to its recent phaseout perfluorooctane sulfonate (PFOS) was produced by electrochemical fluorination processes which yielded technical mixtures composed of linear isomer (similar to 65-79%) and several branched isomers (similar to 21-35%) Because PFOS can biomagnify in wildlife birds that occupy higher trophic levels are at increased risk of exposure We hypothesized that the pharmacokinetic properties of PFOS are isomer specific in developing chicken (Gallus gallus domesticus) embryos exposed to technical grade PFOS (T-PFOS) In the present study T PFOS was composed of 62 7% linear isomer (L PFOS), and 37 3% branched isomer including six mono(trifluoromethyl) branched isomers and four bis(trifluoromethyl)-branched isomers Concentrations of 0 1 5 or 100 mu g/g of T PFOS were injected into the air cell of chicken eggs prior to incubation After pipping compared with T PFOS the PFOS isomer profile in embryonic liver tissue for the 0 1 mu g/g dose group showed 21% enrichment in the proportion of L PFOS with a corresponding decrease in the proportion of branched isomers Not all branched isomers were discriminated against at equal rates The proportion of two mono(trifluoromethyl)-branched isomers and three bis(trifluoromethyl) branched isomers decreased to a greater degree than other branched isomers In contrast, the mono branched isomer P6MHpS was overrepresented in the low dose group In the higher dose groups L-PFOS was still enriched but only by approximately 10% which indicated a dose-dependent change in isomer composition relative to T PFOS These results show that accumulation of PFOS in chicken embryo livers is dependent on the presence and position of branches on the alkyl backbone This supports the hypothesis that the pharmacokinetics of PFOS are isomer specific in biota, and may help explain why wildlife PFOS burdens are dominated by L PFOS relative to T PFOS mixtures Environ Toxicol Chem 2011 30 226-231 (C) 2010 SETAC