| Use of Personal Measurements for Ozone Exposure Assessment: A Pilot Study L-J. Sally Liu,1 Petros Koutrakis,1 Helen H.
Suh,1 James D. Mulik,2 and Robert M. Burton2 1Department of Environmental Health, Harvard
School of Public Health, Boston, MA 02115 USA; 2Atmospheric
Research and Exposure Assessment Laboratory, U.S. Environmental Protection
Agency, Research Triangle Park, NC 27711 USA Abstract
During summer 1991, we collected indoor, outdoor, and personal ozone concentration data as well as time-activity data in State College, Pennsylvania. These concentrations were measured for 23 children and their homes using passive ozone samplers. Outdoor concentrations were also measured at a stationary ambient monitoring site. Results from this pilot study demonstrate that fixed-site ambient measurements may not adequately represent individual exposures. Outdoor ozone concentrations showed substantial spatial variation between rural and residential regions. Ignoring this spatial variation by using fixed-site measurements to estimate personal exposures can result in an error as high as 127%. In addition, evidence from our pilot study indicates that ozone concentrations of a single indoor microenvironment may not represent those of other indoor microenvironments. Personal exposures were significantly correlated with both indoor (r = 0.55) and outdoor (r = 0.41) concentrations measured at homes. Multiple regression analyses identified indoor ozone concentrations as the most important predictors of personal exposures. However, models based on time-weighted indoor and outdoor concentrations explained only 40% of the variability in personal exposures. When the model included observations for only those participants who spent the majority of their day in or near their homes, an R2 of 0.76 resulted when estimates were regressed on measured personal exposures. It is evident that contributions from diverse indoor and outdoor microenvironments must be considered to estimate personal ozone exposures accurately. Key words: exposure modeling, ozone, passive sampler, personal exposure assessment. Environ Health Perspect 101:318-324(1993) . Address correspondence to L-J.S. Liu, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Building I, G-13B, Boston, MA 02115 USA. Part of this study has been funded by the U.S. Environmental Protection Agency under cooperative agreement to Harvard School of Public Health no. CR816 740-02. This paper has been subjected to EPA peer and administrative review, and it has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. This work was also supported the Electric Power Research Institute (contract no. RP 1630-59) . We acknowledge Mary Ann Allan and Janice Yager for their contributions. This study could not have been done without the intensive field work of Mark Davey, Dave Decapria, Carolyn Shively, Jeffrey Myers, Erik Selekman, Glenn Hunter, and Robert Surh. Ben Rosenthal's dedicated lab analysis is highly appreciated. Discussions with Mike Wolfson, David Wypij, Louise Ryan, Barry Ryan, George Allen, and Sue Froehlich of the Harvard School of Public Health were extremely helpful. Received 4 Dec 1992 ; revised 25 May 1993.
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