Impact of precursors and bioaccessibility on childhood PFAS exposure from house dust

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 (138) ranged from 3.0 to 2640 mu g kg-1 with PFOS (1.5-675 mu g kg-1), PFHxS (1.0-405 mu g kg-1) and PFOA (1.0-155 mu g 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 mu g kg-1) with median post-TOP assay PFCA (C4-C8) concentrations (92.3-170 mu g 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 mu g 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 1PFOA, 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.

Automated summary

This study examined the impact of precursors and bioaccessibility on children's exposure to PFAS in house dust from Adelaide, Australia. They found high concentrations of PFAS and significant changes in concentrations after the TOP assay. The bioaccessibility of PFAS was determined and found to be higher for PFCA compared to PFSA. The estimated daily intake of PFAS was calculated, showing a significant decrease when considering dust-specific bioaccessibility values. However, a worst-case scenario analysis showed potential higher exposure levels. Overall, the study highlights the importance of understanding PFAS exposure pathways. Rating: 8/10