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CONTROLLED, SHORT-TERM DERMAL AND INHALATION EXPOSURE TO CHLOROFORM
Citation:
Gordon, S. M., D. Kenny, P. J. Callahan, M. C. Brinkman, L A. Wallace, AND D. L. Ashley. CONTROLLED, SHORT-TERM DERMAL AND INHALATION EXPOSURE TO CHLOROFORM. Presented at ISEA 2000 Exposure Analysis in the 21st Century: Integrating Science, Policy and Quality of Life, Monterey Peninsula, CA, October 24-27, 2000.
Impact/Purpose:
The primary study objectives are:
1.To quantify personal exposures and indoor air concentrations for PM/gases for potentially sensitive individuals (cross sectional, inter- and intrapersonal).
2.To describe (magnitude and variability) the relationships between personal exposure, and indoor, outdoor and ambient air concentrations for PM/gases for different sensitive cohorts. These cohorts represent subjects of opportunity and relationships established will not be used to extrapolate to the general population.
3.To examine the inter- and intrapersonal variability in the relationship between personal exposures, and indoor, outdoor, and ambient air concentrations for PM/gases for sensitive individuals.
4.To identify and model the factors that contribute to the inter- and intrapersonal variability in the relationships between personal exposures and indoor, outdoor, and ambient air concentrations for PM/gases.
5.To determine the contribution of ambient concentrations to indoor air/personal exposures for PM/gases.
6.To examine the effects of air shed (location, season), population demographics, and residential setting (apartment vs stand-alone homes) on the relationship between personal exposure and indoor, outdoor, and ambient air concentrations for PM/gases.
Description:
Studies were conducted to determine the uptake by humans of chloroform as a result of controlled short-term dermal and inhalation exposures. The approach used continuous real-time breath analysis to determine exhaled-breath profiles and evaluate chloroform kinetics in the human body. In the first study, real-time breath analysis was used to measure dermal absorption of chloroform while showering. Six subjects (3 male, 3 female) showered in water containing chloroform (at ~ 70-90 ug/L) at two temperatures (36 C and 42 C) for 30 min. Water temperature had a powerful effect on dermal absorption; the mean amount of chloroform exhaled varied from 0.4 plus/minus 0.3 ug at 36 C to 2.6 plus/minus 1.1 ug at 42 C. This finding, which will need to be incorporated into existing and future models of dermal absorption, likely results from increased blood flow to the skin at the higher temperatures. Uptake and elimination residence times (tau uptake = 10.3 plus/minus 3.1 min; tau decay = 7.0 plus/minus 0.8 min) were similar to those determined in an earlier investigation (Gordon et al., 1998).
In the second study, four of the original six subjects were exposed on five separate occasions (one subject participated twice) to 90-100 ppb chloroform-d for 2 hours, followed by exposure to clean air for 20-30 min. Exhaled breath was continuously sampled and analyzed with the real-time breath technology; blood samples were simultaneously collected from 3 of the subjects (6 samples during exposure; 6 samples post-exposure). The uptake and decay of chloroform in the blood was estimated by fitting the exposure and post-exposure breath and blood data to a multi-compartmental model that estimated residence times. The measurements also provided information on the chloroform blood:breath concentration ratio and the fraction of breath chloroform exhaled unchanged at equilibrium (~0.2).
This abstract has been reviewed in accordance with U.S. Environmental Protection Agency's peer and administrative review policies and approved for publication.