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Dermal uptake of three brominated phenols: tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), and 2,4,6-tribromophenol (TBP).
Citation:
Richards, A., G. Knudsen, M. Hughes, AND L. Birnbaum. Dermal uptake of three brominated phenols: tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), and 2,4,6-tribromophenol (TBP). Society of Toxicology, San Antonio, Texas, March 11 - 15, 2018.
Impact/Purpose:
High production volume brominated flame retardants are used in consumer products, resulting in ubiquitous human exposure. Although the major route of exposure to these chemicals is oral uptake, dermal contact is likely via contaminated dust. This study examined the dermal absorption (dose retained in skin) and penetrance (dose recovered in receptor fluid (in vitro) or tissue/excreta (in vivo)) of three brominated flame retardants using rat for in vivo studies and rat and human skin for in vitro studies. The studies indicate all three chemicals are likely to be dermally bioavailable and dermal contact with these agents should be considered an important route of exposure. OPPTS is one organization that would be interested in this study.
Description:
Three brominated phenols, TBBPA, TBBPA-BDBPE, and TBP, were assayed to determine dermal absorption and penetrance. All three chemicals are high production volume brominated flame retardants (BFR) used in consumer products, resulting in ubiquitous human exposure. TBBPA, a reactive flame retardant commonly used in printed circuit boards and other polycarbonate resins, was shown to cause uterine epithelial tumors in a NTP 2-year cancer bioassay. Little toxicity data are available for TBBPA’s replacement alternative TBBPA-BDBPE, but its additive usage poses a higher risk of migration into environmental matrices. TBP is used as a wood fungicide and reactive flame retardant and has been shown to disrupt thyroid signaling. Although the major route of exposure to these chemicals is oral uptake, dermal contact is likely via contaminated dust. In the studies presented here, independent trials of a single dose of 100 nmol/cm2 skin (~1 µCi [14C]/cm2) of each BFR were applied to whole rat skin (in vivo) or split-thickness human and rat skin (in vitro) to calculate in vivo human percutaneous uptake. Following application, absorption (retained in dosed skin) and penetrance (recovered in receptor fluid [in vitro] or tissues/excreta [in vivo]) were assessed over 24h. In vivo penetration and absorption in rat skin was 67% and 5% for TBP, 8% and 15% for TBBPA, and 1% and 26% for TBBPA-BDBPE. In human skin, in vitro penetration and absorption was 0.2% and 17% for TBBPA and 0.2% and 53% for TBBPA-BDBPE. In rat skin, in vitro penetration and absorption was 3.5% and 9.3% for TBBPA and 0.3 and 23% for TBBPA-BDBPE. HPLC-radiometric analyses of in vitro perfusate and in vivo skin extracts showed TBBPA was not metabolized by skin. These studies indicate that all three chemicals are likely to be dermally bioavailable and dermal contact with these agents should be considered an important route of exposure. (Supported by the Intramural Research Program at NCI/NIEHS. This abstract does not necessarily represent US EPA policy.)