Mechanisms influencing the BFR distribution patterns in office dust and implications for estimating human exposure

The availability of indoor dust for human exposure by hand adhesion depends on size of dust particle. This paper investigates the distribution patterns of brominated flame retardants (BFRs) with particle size in indoor dust. A mixed sample of office dust was obtained from twenty eight high-level offices at Haidian District, Beijing, China. The composite dust (<2mm) was classified into thirteen size fractions (F1-F13: 2000-900-500-400-300-200-100-75-50 μm, 39.58 ± 33.56 μm, 27.93 ± 23.79 μm, 20.15 ± 17.92 μm, 11.38 ± 15.01 μm and 5.64 ± 6.78 μm), by which 18BFRs contents were analyzed. Dust adhered to floc (FD) was also sampled for a separate analysis and was found to contain extremely high level of BFR concentration. The BFR level determined from all fractions of the sampled office dust ranged from ND (not detected) (F1, BDE28, 66) to 5455.4 (FD, BDE209) ng g(-1), in which BDE 209 and BTBPE (1,2-bis (2,4,6-tribromphenoxy) ethane) were found to be the most abundant BFR residue. The influencing factors of BFR distribution patterns in office dust were deduced to be specific surface area, organic content of particles, and origin process (fragmentation and absorption) of BFRs. Selection of dust fraction was demonstrated to be influential on both BFR analytical results and human exposure estimation.