INITIAL UPTAKE KINETICS IN HUMAN SKIN EXPOSED TO DILUTE AQUEOUS TRICHLOROETHYLENE IN-VITRO

In vitro uptake of C-14-labeled trichloroethylene (TCE) from dilute (s imilar to 5-ppb) aqueous solutions into human surgical skirt was measu red using accelerator mass spectrometry (AMS). We analyzed 105 breast- tissue samples obtained from three subjects, representing 27 separate exposure experiments conducted at similar to 20 degrees C for 0, 1, 5, 15, 30, or 60 min. The AMS data obtained positively correlate with (p approximate to 0) and vary significantly nonlinearly with (p = 0.0094 ) exposure duration. These data are inconsistent (p approximate to 0) with predictions made for TCE by a proposed U.S. Environmental Protect ion Agency (USEPA) dermal exposure model, even when uncertainties in i ts recommended parameter values for TCE are consider-ed, but are consi stent (p = 0.17) with a I-compartment model for exposed skin-surface t issue governed in vitro by a maximum effective permeability of K-p = 0.28 cm h(-1) (+/-7.0%) and a first-order rate constant of k(l) = 1.2 h(-1) (+/-16%). The apparent compartment depth is estimated to be appr oximately 40-100 mu m, i.e., to comprise much or all of the epidermis. In contrast, the USEPA model implies only negligible TCE penetration beyond SC during a I-h exposure. The Kd estimate based on the 1-compar tment model fit is consistent with estimates for TCE based on in vivo studies, which supports the hypothesis that the USEPA model underpredi cts short-term dermal uptake of TCE from water It is shown that for hu mans, this fit also implies that normalized total uptake of TCE from w afer by short-term dermal contact in vivo is predicted to be fK(p), w here f is similar to 80% for longer normothermic exposures and similar to 95% during a brief hot shower or bath. This study illustrates the power of AMS to facilitate analyses of contaminant biodistribution and uptake kinetics at very low environmental concentrations.