Transfer of Per- and Polyfluoroalkyl Substances (PFAS) from Feed into the Eggs of Laying Hens. Part 2: Toxicokinetic Results Including the Role of Precursors.

A feeding study was performed to examine the bioaccumulation of per- and polyfluoroalkyl substances (PFAS) in laying hens' tissues and plasma and feed-to-egg transfer rates and half-lives. A 25 day exposure was followed by a 42 day depuration period. A target analysis revealed substantial amounts of the precursors N-methyl and N-ethyl perfluorooctane sulfonamidoacetic acid (Me- and EtFOSAA), perfluorooctane sulfonamidoacetic acid (FOSAA), and perfluorooctane sulfonamide (FOSA). In tissues and eggs, the highest bioaccumulation was found for PFHxS, PFHpS, PFOS, and PFOA. Low levels of PFHxS (all samples), PFOS, and FOSAA (in yolk) were measurable even after the depuration period. The egg elimination half-lives of PFOS and aforementioned precursors were estimated to be 4.3 days, while the transfer rates of PFOS and all precursors taken together were 0.99. The transfer rate of PFOA was around 0.49. PFHxS and PFHpS showed apparent transfer rates of >100%, which is hypothesized to indicate the presence of precursors.

Transfer of Per- and Polyfluoroalkyl Substances (PFAS) from Feed into the Eggs of Laying Hens. Part 1: Analytical Results Including a Modified Total Oxidizable Precursor Assay.

The group of per- and polyfluoroalkyl substances (PFAS) comprises thousands of chemicals, which are used in various industrial applications and consumer products. In this study, a feeding experiment with laying hens and feed grown on a contamination site was conducted, and PFAS were analyzed in the feed and eggs to assess the transfer of PFAS into eggs. A targeted analysis of perfluoroalkyl acids (PFAAs) and different sulfonamides was performed. Additionally, the total oxidizable precursor (TOP) assay was modified by fully oxidizing small amounts of the samples instead of oxidizing their extracts in order to overcome potential losses during extraction. Targeted analysis showed the presence of known PFAAs and four sulfonamides in the feed and egg yolk samples. In the plant-based feed, short-chain PFAAs, methyl and ethyl perfluorooctane sulfonamidoacetic acid (Me- and EtFOSAA), and perfluorooctane sulfonic acid (PFOS) were the most abundant PFAS. In the eggs, PFOS, FOSAA, and its alkylated homologues showed the highest concentrations. The TOP assay revealed the presence of substantial amounts of precursors with different chain lengths from C4 to C8. The highest relative increase of PFOA after oxidation was observed in egg yolk from the end of the exposure period (828%). The results of this study demonstrate the transfer of PFAAs and their precursors into hens' eggs and emphasize the contribution of (known and unidentified) precursors to the overall PFAS burden in edible products. The modified TOP assay approach was shown to be a powerful tool to better assess the total burden of samples with PFAS.