USE OF PERSONAL MEASUREMENTS FOR OZONE EXPOSURE ASSESSMENT - A PILOT-STUDY

During summer 1991, we collected indoor, outdoor, and personal ozone c oncentration data as well as time-activity data in State College, Penn sylvania. 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 pi lot study demonstrate that fixed-site ambient measurements may not ade quately represent individual exposures. Outdoor ozone concentrations s howed substantial spatial variation between rural and residential regi ons. 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 conce ntrations of a single indoor microenvironment may not represent those of other indoor microenvironments. Personal exposures were significant ly correlated with both indoor (r = 0.55) and outdoor (r = 0.41) conce ntrations measured at home sites. Multiple regression analyses identif ied indoor ozone concentrations as the most important predictors of pe rsonal exposures. However, models based on time-weighted indoor and ou tdoor concentrations explained only 40% of the variability in personal exposures. When the model included observations for only those partic ipants 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 o utdoor microenvironments must be considered to estimate personal ozone exposures accurately.