Persistent and emerging brominated flame retardants in indoor dust and human hair from remote agro-pastoral areas of Inner Mongolia: Pollution characteristics, source apportionment, and human exposure

The widespread use of brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs), poses significant environmental and health risks, yet data on their contamination in remote agro-pastoral regions remain scarce. This study systematically investigated the pollution characteristics, sources, and human exposure risks of PBDEs and NBFRs in indoor dust and human hair from 11 households in Inner Mongolian grasslands. Results revealed that PBDEs were ubiquitous in all dust samples (median ∑ 10 PBDEs: 15.8 ng/g dw, with a 95% confidence interval of 2.88-48.1 ng/g dw), dominated by BDE-209 (73.6–100%), reflecting legacy Deca-BDE usage despite regulatory restrictions. NBFRs (median ∑NBFRs: 0.77 ng/g dw, 95% CI: 0.42-1.14 ng/g dw) in dust were predominated by hexabromobenzene (HBB, 41.7%) and pentabromobenzylacrylate (PBBA, 18.8%). In human hair, PBDEs (median ∑ 10 PBDEs: 6.77 ng/g dw, 95% CI: 2.31-52 ng/g dw) showed comparable levels to urban populations, with BDE-209 contributing 71.7–99.7%, while NBFRs (median ∑NBFRs: 0.64 ng/g dw, 95% CI: 0.23-1.97) mirrored dust profiles (HBB: 43.4%), suggesting dust as a likely exposure route ( r = 0.575–0.699, p < 0.05). Source analysis identified Penta-/Octa-BDE degradation and industrial applications (plastics/textiles for pTBX-PBBz-PBT; electronics for PBBA-HBB) as key contributors. Human age-dependent accumulation patterns was observed, with higher PBDEs in the elderly and increasing PBBz/PBT levels with age ( r = 0.528–0.564, p < 0.05). Despite lower dust contamination than urban areas, hair-based exposure highlighted non-dust pathways (e.g., air inhalation) for low-brominated congeners. These findings underscore the persistent risks of legacy PBDEs and emerging NBFRs in remote regions, advocating for stricter lifecycle management of BFR-containing products and long-term health monitoring.