1 State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
2 Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West Montreal, Quebec H4B 1R6, Canada.
3 Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China.
4 Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
5 State Environmental Protection Key Laboratory of Environmental Health Impact Assessment of Emerging Contaminants, School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Environmental Protection Key Lab of Environmental Big Data and Intelligent Decision-making, School of

Indoor exposure to organic flame retardants (FRs) has raised extensive concern due to associated adverse health effects. Indoor-exposure induced daily intakes of six widely used FRs individually ranged 0.002-611 ng/day and 0.02-463 ng/day, respectively, for adults and 2-6-year-old children; and resulting internal exposure levels ranged 0.1-159 and 2.1-4500 ng/g lipid, respectively. A proportion of 0.001-5.9% and 0.006-10.3% of individual FRs emitted into indoor air ultimately entered bodies of adults and children respectively. Tris(2-chloroisopropyl)phosphate dominated in emissions, whilst 2-ethylhexyl-2,3,4,5-tetrabromobenzoate dominated in human bodies. Hand-to-mouth contact was the most important exposure pathway for less volatile FRs including most brominated FRs, whilst inhalation was the predominant intake pathway of tris(2-chloroisopropyl)phosphate. Relative importance of 29 environmental, behavioral and physiological parameters was ranked to explore key drivers influencing exposure and accumulation of FRs in humans. Results suggested that frequent bathing and handwashing can reduce exposure effectively, especially for children. Bodyweight and lipid fraction were only positively related to internal accumulation and body-weight-normalized concentrations of compounds with low metabolic rates (half-lives =10³ h) in humans. Our findings help control indoor exposure to FRs and are supportive of human exposome studies in the future.