In vitro estimation of oral bioaccessibility of brominated flame retardants in indoor dust by fasted and fed physiologically extraction test

Aim: There is a dearth of information on in vitro oral bioaccessibility, challenging the evaluation of the health risks arising from indoor dust exposure to the brominated flame retardants, tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HBCDD). Here, we estimate the human oral bioaccessibility of TBBPA and HBCDD in indoor dust by applying the standardized bioaccessibility test under fasting (UBM-like test) and fed (FOREhST test) conditions. 

Methods: In vitro bioaccessibility of HBCDD and TBBPA of sixteen indoor dust samples was conducted under fasted and fed states. In the fed test, food components, including healthy and unhealthy food. The concentrations of HBCDD and TBBPA were analyzed using LC-MS/MS. Bioaccessibility was calculated from the ratio of the amount of HBCDD and TBBPA in a simulated gut solution to that in indoor dust. The average daily dose (EDD_{bioaccessibility}) was calculated from the estimated daily intake and percentage of bioaccessibility. 

Results: The concentration of TBBPA and HBCDD in indoor dust ranged from 137 to 14,671 ng g^-1 and < 0.7 to 528 ng g^-1, respectively. A higher bioaccessible concentration was observed in the small intestine than in the stomach and mouth. The condition of the fed state with food containing fat showed greater bioaccessibility of TBBPA and HBCDD at 74.0% ± 9.5% and 62.2% ± 10.1%, respectively. In contrast, the fed state with lower fat food containing fiber presented the lowest bioaccessibility with a mean of 54.7% ± 10.7% for TBBPA and 53.7% ± 10.8% for HBCDD. Moreover, children are more exposed than adults, especially those who ingest indoor dust with fatty food. 

Conclusion: The oral bioaccessibility of TBBPA and HBCDD in indoor dust was highest in the fed state with fatty food, followed by fasted and fed states with lower fat, higher fiber food. Similarly, the estimated daily dose (EDD_{bioaccessibility}) for children exceeded that for adults. Therefore, this study indicated that food consumption is a factor influencing the bioaccessibility of TBBPA and HBCDD present in indoor dust.