Relative Contribution of Dermal Contact with Indoor Dust to Overall Human Exposure to Perfluoroalkyl Substances

Perfluoroalkyl substances (PFAS) have been quantified in household dust samples all over the world. This presents an exposure hazard via ingestion and dermal contact. Based on previously-reported bioaccessibility and bioavailability data, human dermal exposure to PFAS via dermal contact with indoor dust was estimated for the following six PFAS: C5-C8-perfluorocarboxylic acids (PFCAs), plus C4 and C7-perfluorosulfonic acids (PFSAs). Exposure for people from five countries (Sweden, Japan, Canada, Australia and Norway) was estimated and compared for two age groups (adults and toddlers) under two exposure scenarios (summer and winter). S6PFAS exposure via dermal uptake from dust during summer ranged from 25–767 pg/kg bw/week and 91–2761 pg/kg bw/week for adults and toddlers, respectively. In general, dermal uptake of PFAS from dust was 10 times lower in winter than in summertime. Perfluorohexanoic acid (PFHxA) made the highest contribution to dermal exposure to S6PFAS in all countries except Norway, where PFOA > PFHxA. Dermal exposure to S6PFAS via dermal contact with dust was compared to published exposure estimates via inhalation, indoor dust ingestion, and diet for a cohort of Norwegian adults for which temporally-consistent exposure data were available. Of our target PFAS, dermal exposure of this cohort via contact with dust was greatest for PFOA (2.1 pg/kg bw/day in summer), followed by PFHxA (1.4 pg/kg bw/day in summer). In general, dermal contact with dust did not contribute substantially to overall human exposure to PFSAs, compared to PFCAs. For PFCAs, dermal exposure is a potentially important pathway, with dermal exposure to dust alone contributing to similar levels of exposure as indoor air inhalation for certain compounds. Consequently, this pathway should not be dismissed in future exposure assessments, especially if other sources of dermal exposure to PFAS, e.g., personal care products and fabrics, are considered.