Estimation of personal ozone exposure using ambient concentrations and influencing factors

Evidence is limited regarding whether ambient monitoring can properly represent personal ozone exposure. We conducted a longitudinal panel study to measure personal exposure to ozone using real-time personal ozone monitors. Corresponding ambient ozone concentrations and possible influencing factors (meteorological conditions and activity patterns) were also collected. We used linear mixed-effect models to analyze personalambient ozone concentration associations and possible influencing factors. Ambient ozone concentrations were around two to three times higher than personal ozone (43.1 mu g/m(3) on average) and their correlations were weak with small slopes (0.35) and marginal R square (R-M(2)) values (0.24). Larger R-M(2) values were found under high temperature (> 29.5 degrees C), low humidity (< 62.1%), good ventilation conditions (> 4 h) and for individuals spent longer time outdoors (> 0.6 h). In final model, personal ozone exposure was positively associated with ambient concentrations and ventilation conditions, but inversely correlated with ambient temperature and humidity. The models explained > 50% of personal ozone concentration variabilities. Our results highlight that ambient ozone concentration alone is not a suitable surrogate for individual exposure assessment. Meteorological conditions (temperature and humidity) and activity patterns (windows opening and outdoor activities) that affecting personal ozone exposure should be taken into account.