| Water contamination by VOCs is widespread. This contamination results in human exposure through multiple routes including inhalation, ingestion, and/or dermal absorption. Although dermal absorption is known to be important, there is considerable uncertainty about the accuracy of current estimates of the dermal permeability coefficient (Kp) for many VOCs due the fact that its estimation is based invalidated models. In this study, we present an experimental, in vivo, direct approach for measuring the VOC dermal uptake in humans from contaminated water.; This study was successful in detecting dermal uptake from water contaminated with low-levels of VOCs. Results for 8 male and 3 female adults suggest that the percent absorbed in 100ml solution over the one hour exposure was 13.5, 14.9, 20.8, and 7.3 for chloroform, 111-TCA, toluene, and MTBE, respectively, with a corresponding mean Kp of 0.166 (SD: 0.108), 0.167 (SD: 0.107), 0.250 (SD: 0.064), and 0.109 (SD: 0.157) cm/hr.; We observed considerable inter- and intra-subject variability in dermal uptake, and this variability created large confidence intervals around our mean estimates. Nonetheless, because our observed estimates are all significantly greater than those accepted by the EPA, we have shown that the EPA is likely relying on underestimates of actual uptake.; The second dimension to this study was to evaluate the effectiveness of using a breath measurement as a biomarker to detect or reflect VOC dermal exposure. Breath samples used for this purpose were collected before, during, and after VOC exposure in parallel with the task of VOC aqueous concentration monitoring. Breath samples were collected via a single-breath exhalation into Summa canisters and were analyzed by a gas chromatography/mass spectrometry detector (GC/MS). Results for one female and one male showed significant exposure-related elevation (p < 0.05) in the breath level during and after exposure for chloroform and 111-TCA (p < 0.10 for 111-TCA during exposure). For MTBE, the fact that no breath pattern effect was observable was consistent with our inability to find a detectable dermal uptake. In the case of toluene, we were able to estimate dermal uptake but no clearly discernible pattern was detected via the breath biomarker, perhaps because most of the uptake was metabolized, leaving only a small, undetectable percentage to be excreted through exhalation. (Abstract shortened by UMI.)... |
