Occurrence, Source Profiles, and Human Exposure to PBDEs and Alternative Brominated Flame Retardants in Vehicle Dust from a Hot-Climate Region

Brominated flame retardants (BFRs) are widely used in automotive polymers and electronic components, yet vehicles remain an underexplored microenvironment for human exposure, particularly in hot climates. This study characterized the occurrence, profiles, sources, and health risks of polybrominated diphenyl ethers (PBDEs) and selected alternative BFRs in dust from 80 vehicles (domestic cars and taxis; model years 2015–2022) operating in Jeddah, Saudi Arabia. Dust samples were collected using a standardized vacuuming protocol, extracted and cleaned up by solvent extraction and silica SPE, and analyzed using GC–NCI–MS. We quantified selected PBDE congeners and several alternative BFRs, including DBDPE and TBB. BDE-209 and DBDPE dominated the BFR burden in vehicle dust, while lower-brominated PBDEs occurred at much lower levels, consistent with the global phase-out of Penta- and Octa-BDE. Taxis generally exhibited higher central tendency values for key congeners than domestic vehicles, reflecting longer in-vehicle time, higher occupancy, and more intensive use. Multivariate analysis (PCA and correlation) indicated two main source groupings: (i) legacy Penta-BDE–related congeners associated with polyurethane foams and textile furnishings, and (ii) Octa/Deca-BDE and DBDPE linked to hard plastics and electronic components. Human exposure assessment showed that dust ingestion overwhelmingly dominated BFR intake, with dermal and inhalation pathways contributing minimally. Non-carcinogenic hazard indices (HI) for all congeners were well below unity, and incremental lifetime cancer risk (ILCR) values for BDE-209 fell within or near commonly accepted risk ranges, although taxi drivers consistently showed higher exposure than domestic drivers. Overall, while risk estimates suggest low to moderate concern for adults under current conditions, the persistence, bio-accumulative potential, and mixture toxicity of BFRs, coupled with extreme thermal conditions inside vehicles, underscore the need for continued monitoring, material substitution, and targeted risk-reduction strategies in automotive interiors.