Estimation of recent exposures to volatile organic chemicals using alveolar air measurements

Abstract

Volunteers were exposed in a chamber to a mixture of volatile organic compounds (VOC) containing dichloromethane (75092), n-hexane (110543), 1,1,1-trichloroethane (71556), trichloroethylene (79016), toluene (108883), ethylbenzene, (100414), xylene (1330207), and n-decane (124185), at a concentration ranging from 1,100 to 9,350 micrograms/cubic meter. The exposure period lasted either 2 or 10 hours. There were four male and one female subjects. During the exposure participants were either at rest or physically active on an exercise bicycle. Subjects were monitored in a clean, outdoor environment at rest after the exposure period for 4 or 24 hours. Samples of alveolar air were collected before, during and after exposure, and analyzed for VOCs. The study results indicated that it was possible to use a post exposure breath measurement to accurately predict VOC concentrations in exposure air in many situations. In order to use this method in the field, it is necessary to make certain assumptions regarding exposure duration and the time since exposure stopped and sample collection occurred. Using parameters averaged by chemical among individuals did not significantly affect the average accuracies of prediction achieved. When parameters were averaged by chemical class the uncertainties in the predictions increased. A dramatic impact on VOC concentrations in breath was noted due to activity, and a knowledge of ventilation during exposure is used to improve the accuracies of prediction when using at rest parameters. The authors suggest that a larger group of subjects be used in order to determine the effects of metabolic and other differences between individuals in the group.