Estimating Volatile Organic Compound Concentrations in Selected Microenvironments Using Time–Activity and Personal Exposure Data

Abstract

Repeated measures of personal exposure to 14 volatile organic compounds (VOC) were obtained over 3 seasons for 70 healthy, nonsmoking adults living in Minneapolis–St. Paul. Matched data were also available for participants' time–activity patterns, and measured VOC concentrations outdoors in the community and indoors in residences. A novel modeling approach employing hierarchical Bayesian techniques was used to estimate VOC concentrations (posterior mode) and variability (credible intervals) in five microenvironments: (1) indoors at home; (2) indoors at work/school; (3) indoors in other locations; (4) outdoors in any location; and (5) in transit. Estimated concentrations tended to be highest in “other” indoor microenvironments (e.g., grocery stores, restaurants, shopping malls), intermediate in the indoor work/school and residential microenvironments, and lowest in the outside and in-transit microenvironments. Model estimates for all 14 VOC were reasonable approximations of measured median concentrations in the indoor residential microenvironment. The largest predicted contributor to cumulative (2-day) personal exposure for all 14 VOC was the indoor residential environment. Model-based results suggest that indoors-at-work/school and indoors-at-other-location microenvironments were the second or third largest contributors for all VOC, while the outside-in-any-location and in-transit microenvironments appeared to contribute negligibly to cumulative personal exposure. Results from a mixed-effects model indicate that being in or near a garage increased personal exposure to o-xylene, m/p-xylene, benzene, ethylbenzene, and toluene, and leaving windows and doors at home open for 6 h or more decreased personal exposure to 13 of 14 VOC, all except trichloroethylene.

This research was funded by a STAR (Science to Achieve Results) Grant (R825241) from the U.S. Environmental Protection Agency, National Center for Environmental Research. We thank the individuals who participated in the study and acknowledge the contributions of the field team. We also thank the 3M Corporation for donating some of the organic vapor monitors used in this study. The help and support provided by the Minnesota Pollution Control Agency were essential to the success of this project. Ken Sexton was a member of the Division of Environmental and Occupational Health at the University of Minnesota School of Public Health when this study was conducted.