| Trichloroethene Levels in Human Blood and Exhaled Breath from Controlled Inhalation Exposure Joachim D. Pleil,1 Jeffrey W. Fisher,2 and Andrew B. Lindstrom1 1National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711 USA
2Toxicology Division, Armstrong Laboratory, Wright-Patterson Air Force Base, Ohio 45433 USA Abstract
The organic constituents of exhaled human breath are representative of bloodborne concentrations through gas exchange in the blood/breath interface in the lungs. The presence of specific compounds can be an indicator of recent exposure or represent a biological response of the subject. For volatile organic compounds, sampling and analysis of breath is preferred to direct measurement from blood samples because breath collection is noninvasive, potentially infectious waste is avoided, the sample supply is essentially limitless, and the measurement of gas-phase analytes is much simpler in a gas matrix rather than in a complex biological tissue such as blood. However, to assess the distribution of a contaminant in the body requires a reasonable estimate of the blood level. We have investigated the use of noninvasive breath measurements as a surrogate for blood measurements for (high) occupational levels of trichloroethene in a controlled exposure experiment. Subjects were placed in an exposure chamber for 24 hr ; they were exposed to 100 parts per million by volume trichloroethene for the initial 4 hr and to purified air for the remaining 20 hr. Matched breath and blood samples were collected periodically during the experiment. We modeled the resulting concentration data with respect to their time course and assessed the blood/breath relationship during the exposure (uptake) period and during the postexposure (elimination) period. Estimates for peak blood levels, compartmental distribution, and time constants were calculated from breath data and compared to direct blood measurements to assess the validity of the breath measurement methodology. Blood/breath partition coefficients were studied during both uptake and elimination. At equilibrium conditions at the end of the exposure, we could predict actual blood levels using breath elimination curve calculations and a literature value partition coefficient with a mean ratio of calculated:measured of 0.98 and standard error (SE) = 0.12 across all subjects. blood/breath comparisons at equilibrium resulted in calculated in vivo partition coefficients with a mean of 10.8 and SE = 0.60 across all subjects and experiments and 9.69 with SE = 0.93 for elimination-only experiments. We found that about 78% of trichloroethene entering the body during inhalation exposure is metabolized, stored, or excreted through routes other than exhalation. Key words: blood/breath measurement, breath sampling, partition coefficients, time constants, trichloroethene, uptake and elimination models. Environ Health Perspect 106:573-580 (1998) . [Online 12 August 1998] http://ehpnet1.niehs.nih.gov/docs/1998/106p573-580pleil/ abstract.html Address correspondence to J.D. Pleil, U.S. EPA, NERL (MD-44) , S-239C Environmental Research Center Annex, 79 Alexander Drive, Research Triangle Park, NC 27711 USA. We thank the anonymous subject volunteers for their generous participation in the exposure scenarios. We are grateful for the technical assistance from J. Bowyer, P. Kizakevich, M. McCartney, L. Van Hoose, and K. Hudnell. Special thanks go to the QA/QC and research personnel from ManTech, Research Triangle Park, NC, and Dayton, OH. Chamber facilities and operation, subjects, and medical personnel were provided by Research Triangle Institute under U.S. Army Medical Research and Development Command Project 4970-04, grant # DAMD17-91-C-1007. Samples and analytical confirmation for QA/QC standards for breath work were provided by ManTech Environmental Technology, Inc., under EPA contract 68-D0-0106. Blood analyses were performed by ManTech Environmental Technology, Inc., under Air Force contract # F-41624-96-C-9010. This work has been funded by the U.S. EPA and the U.S. Air Force. It has been subjected to agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Received 29 December 1997 ; accepted 28 April 1998.
The full version of this article is available for free in HTML format. |
