Impact of microenvironments and personal activities on personal PM 2.5 exposures among asthmatic children

摘要

Personal activity patterns have often been suggested as a source of unexplained variability when comparing personal particulate matter (PM 2.5) exposure to modeled data using central site or microenvironmental data. To characterize the effect of personal activity patterns on asthmatic children's personal PM 2.5 exposure, data from the Windsor, Ontario Exposure Assessment Study were analyzed. The children spent on an average 67.1±12.7% (winter) and 72.3±22.6% (summer) of their time indoors at home where they received 51.7±14.8% and 66.3±19.0% of their PM 2.5 exposure, respectively. In winter, 17.7±5.9% of their time was spent at school where they received 38.6±11.7% of their PM 2.5 exposure. In summer, they spent 10.3±11.8% 'indoors away from home', which represented 23.4±18.3% of their PM 2.5 exposure. Personal activity codes adapted from those of the National Human Activity Pattern Survey and the Canadian Human Activity Pattern Survey were assigned to the children's activities. Of the over 100 available activity codes, 19 activities collectively encompassed nearly 95% of their time. Generalized estimating equation (GEE) models found that, while indoors at home, relative to daytime periods when sedentary activities were conducted, several personal activities were associated with significantly elevated personal PM 2.5 exposures. Indoor playing represented a mean increase in PM 2.5 of 10.1 μg/m 3 (95% CI 6.3-13.8) and 11.6 μg/m 3 (95% CI 8.1-15.1) in winter and summer, respectively, as estimated by a personal nephelometer.