Ozone personal exposures and health effects for selected groups residing in the Fraser Valley

Due to concern regarding poor ambient air quality in the Fraser Valley, a series of exposure and health effects assessments were performed to evaluate the impact of summer photochemical air pollution. In 1992 and 1993, three groups of individuals were selected for personal monitoring of ozone exposure, based on prior expectations of their activity patterns. The first group spent a majority of the work day indoors or commuting, the second group spent more time outdoors and the third group spent the entire personal monitoring period outdoors. Time-activity data were collected for the first two groups and differences in personal ozone exposures were found to be associated with the fraction of time a person spent outdoors. Similarly, differences among groups in the mean ozone exposure were associated with time spent outdoors. These results and other exposure information were used to design a study of the health impacts of summer ambient air pollution that was conducted during the time period of the Pacificʹ93 field campaign. Aerosol acidity levels in the Fraser Valley were observed to be very low in 1992 so the health study focused on the effects of ozone exposure. The subjects were adult farm workers (26 male, 32 female; mean age 44.4, range 10–69) who spent the entire working day outdoors (a subset of group 3 above). Lung function measurements were made twice daily on each subject, once before and once after their work shift, from 23 June–26 August 1993. Ambient O3 concentrations were measured continuously at several nearby locations. In a regression model including individual lung function level, date, temperature and daily maximum O3, a statistically significant (p < 0.001) negative association was observed between ozone and lung function. This association between ozone and reduced lung function was still apparent the following day, suggesting a persistent ozone effect. These results indicate that exposure to ambient O3 concentrations below either the U.S. NAAQS (120 ppb) or the Canadian Air Quality Objective (82 ppb) may have an adverse effect on the lung function of people engaged in outdoor work for several hours a day.