Detection and intake assessment of organophosphate flame retardants in house dust in Japanese dwellings

The demand for phosphorus flame retardants (PFRs) has recently increased as an alternative to polybrominated diphenyl ether (PBDE). PFRs have been detected in house dust, but little is known about the concentrations of PFRs in private homes and the effects on human health. We measured the levels of 10 PFRs in indoor floor dust and upper surface dust from 128 Japanese dwellings of families with children in elementary school. The median (min–max) concentrations (μg/g) of PFRs were as follows: tris(2-butoxyethyl) phosphate (TBOEP), 30.88 (< 0.61–936.65); tris(2-chloro-iso-propyl) phosphate (TCIPP), 0.74 (< 0.56–392.52); and triphenyl phosphate (TPHP), 0.87 (< 0.80–23.35). These values exceeded 50% detection rates, and the rates are median over the LOD in floor dust. The concentrations (μg/g) of TBOEP 26.55 (< 0.61–1933.24), TCIPP 2.23 (< 0.56–621.23), TPHP 3.13 (< 0.80–27.47), tris(2-chloroethyl) phosphate (TCEP) 1.17 (< 0.65–92.22), and tributyl phosphate (TNBP) 0.74 (< 0.36–60.64) exceeded 50% detection rates in the upper surface dust. A significant positive correlation (P < 0.05) between the concentrations of TCIPP and TBOEP was shown in floor dust and upper surface dust (n = 48). Estimated median and 95th percentile daily intake was calculated for toddlers and elementary school children and was compared with reference dose values (RfD) from the literature. For TBOEP, the estimated 95th percentile intake from floor dust was 14% of RfD for toddlers and 4% for school children. The estimated intake from upper surface dust was somewhat lower. Estimated median intake of TBOEP and median intake for the other PFRs were less than 1% of the RfD. TBOEP, TCIPP and TPHP were the main PFRs in the dust. The median levels of PFRs are well below the RfD values.