RESUMO
The efficacy of RemBind® 300 to immobilize per- and polyfluoroalkyl substances (PFAS) in aqueous film forming foam (AFFF)-impacted soil (∑28 PFAS 1280-8130 ng g-1; n = 8) was assessed using leachability (ASLP) and bioaccumulation (Eisenia fetida) endpoints as the measure of efficacy. In unamended soil, ∑28 PFAS leachability ranged from 26.0 to 235 µg l-1, however, following the addition of 5% w/w RemBind® 300, ∑28 PFAS leachability was reduced by > 99%. Following exposure of E. fetida to unamended soil, ∑28 PFAS bioaccumulation ranged from 18,660-241,910 ng g-1 DW with PFOS accumulating to the greatest extent (15,150-212,120 ng g-1 DW). Biota soil accumulation factors (BSAF) were significantly (p < 0.05) higher for perfluoroalkyl sulfonic acids (PFSA; 13.2-50.9) compared to perfluoroalkyl carboxylic acids (PFCA; 1.2-12.7) while for individual PFSA, mean BSAF increased for C4 to C6 compounds (PFBS: 42.6; PFPeS: 52.7; PFHxS: 62.4). In contrast, when E. fetida were exposed to soil amended with 5% w/w RemBind® 300, significantly lower PFAS bioaccumulation occurred (∑28 PFAS: 339-3397 ng g-1 DW) with PFOS accumulation 23-246 fold lower compared to unamended soil. These results highlight the potential of soil amendments for reducing PFAS mobility and bioavailability, offering an immobilization-based risk management approach for AFFF-impacted soil.
RESUMO
This study investigated the impact of precursors and bioaccessibility on childhood per- and polyfluoroalkyl substances (PFAS) exposure in house dust (n = 28) from Adelaide, Australia. Sum PFAS concentration (∑38) ranged from 3.0 to 2640 µg kg-1 with PFOS (1.5-675 µg kg-1), PFHxS (1.0-405 µg kg-1) and PFOA (1.0-155 µg kg-1) constituting the major perfluoroalkyl sulfonic (PFSA) and carboxylic acids (PFCA). The total oxidizable precursor (TOP) assay was applied to estimate concentrations of unmeasurable precursors that may undergo oxidation to measurable PFAS. Sum PFAS concentration post-TOP assay changed 3.8-112-fold (91.5-62,300 µg kg-1) with median post-TOP assay PFCA (C4-C8) concentrations (92.3-170 µg kg-1) increasing significantly (13.7-48.5-fold). As incidental dust ingestion is a significant exposure pathway for young children, PFAS bioaccessibility was determined using an in vitro assay. Sum PFAS bioaccessibility ranged from 4.6 to 49.3 % with significantly (p < 0.05) higher PFCA (10.3-83.4 %) bioaccessibility compared to PFSA (3.5-51.5 %). When in vitro extracts were assessed post-TOP assay, PFAS bioaccessibility changed (7-1060 versus 137-3900 µg kg-1) although percentage bioaccessibility decreased (2.3-14.5 %) due to the disproportionately higher post-TOP assay PFAS concentration. PFAS estimated daily intake (EDI) was calculated for a 'stay-at-home' 2-3-year-old child. Inclusion of dust specific bioaccessibility values resulted in a 1.7-20.5-fold decrease in ∑PFOA, PFOA and PFHxS EDI (0.02-1.23 ng kg bw-1 day-1) compared to default absorption assumptions (0.23-5.4 ng kg bw-1 day-1). However, when 'worst-case scenario' precursor transformation was considered, EDI calculations were 4.1-187-fold higher that the EFSA tolerable weekly intake value (equivalent to 0.63 ng kg bw-1 day-1), although this was moderated when exposure parameters were refined through PFAS bioaccessibility incorporation (0.35-17.0-fold higher than the TDI). Irrespective of exposure scenario, EDI calculations were below the FSANZ tolerable daily intake values for PFOS (20 ng kg bw-1 day-1) and PFOA (160 ng kg bw-1 day-1) for all dust samples analysed.
