In vitro dermal absorption of flame retardant chemicals

Flame retardant chemicals may be used in furniture fabric in the future to reduce the flammability of the fabric. As a part of the process to evaluate the potential for exposure to these chemicals, this study examined the in vitro dermal absorption of two flame retardant chemicals. The chemicals wer e [C-14]decabromodiphenyl oxide (DBDPO) and [C-14]tris-(1,3-dichloro-2-prop yl)phosphate (TDCP). Skin from the adult hairless female mouse (SKH1) was r emoved and mounted in flow-through diffusion cells. The chemicals, at three dose levels (DBDPO: 6, 30 and 60 nmol; TDCP: 20, 100 and 200 pmol), were a pplied in a volatile vehicle (tetrahydrofuran for DBDPO; acetone for TDCP) to the skin. Fractions of receptor fluid, pumped below the skin, were colle cted over a 24-h period. The skin was washed with solvent (tetrahydrofuran for DBDPO; ethanol for TDCP) to remove unabsorbed chemical 24 h after appli cation. The receptor fluid, skin wash and skin were analyzed for chemical-d erived radioactivity. The skin from the high-dose group of both chemicals, and the receptor fluid from TDCP high-dose samples, were analyzed for paren t compound and metabolites by HPLC. The 24-h cumulative percent of the dose of DBDPO in the receptor fluid was very low (0.07-0.34%). The applied dose of DBDPO detected in the skin ranged from 2 to 20%. The lowest dose of DBD PO had the highest percentage of the dose (20%) in the skin. The major port ion of the applied dose was removed by washing the skin 24 h after applicat ion of DBDPO, and ranged from 77 to 92%. HPLC analysis of homogenate extrac t prepared from the high-dose of DBDPO-treated skin showed the presence of DBDPO and a minor unknown peak. TDCP was readily detected in the receptor f luids 39-57% of the applied dose of TDCP was in the receptor fluid by 24 h. The solvent wash removed 11-25% of the dose from the skin and 28-35% remai ned in it. RPLC analysis of the skin homogenate extract and receptor fluid extract from the TDCP high-dose treated samples showed the presence of pare nt Compound and a minor unknown peak. TDCP more readily penetrated hairless mouse skin and diffused into the receptor fluid than DBDPO. TDCP has a low er molecular weight and log octanol:water partition coefficent than DBDPO. The differences in the physico-chemical properties of these two chemicals m ost likely explains their dissimilar absorption through hairless mouse skin . (C) 2001 Published by Elsevier Science Ltd.