UC Irvine

Halogenated flame-retardants are chemical compounds added to consumer products to delay fire ignition. Research studies have shown potential effects on human health, including ill effects on neurodevelopment. Therefore, it is important to investigate environmental scenarios that contribute to human exposure. Most exposure assessment studies regarding flame-retardants sample dust from the floor of the home only and assume 24 hours spent at home. To address current knowledge gaps, I investigated 10 microenvironments on the University of California, Irvine campus by collecting dust from elevated surfaces (ESD) and floors (FD). I measured concentrations of the following flame-retardant chemicals in each type of dust collection and across microenvironments: polybrominated diphenyl ether (PBDE) congeners were BDE-28, BDE-47, BDE-66, BDE-85, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-206, BDE-209 and the non-PBDEs were EH-TBB, BEH-TEBP, BTBPE, DBDPE, HBCD, TCEP, TCIPP, TDCIPP, and TBBPA. Secondly, I collected time activity diaries and estimated external flame-retardant exposure for individuals (N = 43) based on time spent across microenvironments and using ESD and FD chemical exposure estimates. Thirdly, I used a one-compartment pharmacokinetic model to estimate individual internal dose following exposure for the flame-retardant chemicals: BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-209. Finally, I used meta-analysis of epidemiological studies on the association between the flame-retardant BDE-47 and infant motor development to estimate benchmark doses. The results are as follows: the ESD was statistically significantly higher than FD for 5 PBDEs and 3 non-PBDEs; estimates of human exposure to most chemicals through ESD are statistically significantly higher for ∑PBDE and ∑non-PBDEs than through FD; the body burden estimates were statistically significantly higher from ESD compared to FD; and 1%, 5%, and 10% benchmark doses for BDE-47 are 43.01, 1083, 61050 ng/g lipid of BDE-47, respectively. The conclusions are that estimates assuming continuous unidimensional exposure likely underestimate flame-retardant exposure and benchmark doses for BDE-47 that use human data are much higher than the reference dose based on animal data and uncertainty factors. The implications of this research are that exposure estimates made with FD may underestimate exposure and reference doses may overestimate risk.