Air pollution and disability days in Toronto: results from the national population health survey.

The influence of air pollution on disability days in Toronto during the period 1994-1999 was examined using data from Canada's National Population Health Survey. A model of disability days (the sum of days spent in bed and days when the respondent cut down on usual activities) during the 2 weeks prior to the interview was constructed by sequentially examining the influence of time period, personal characteristics, weather, and air pollution. After adjusting for these other factors, only the effects of carbon monoxide and particulate matter of median diameter less than 2.5 microm (PM2.5) were statistically significant (respectively, 30.8% (95% CI 1.2-69.0) and 21.9% (95% CI 3.8-43.0) increase in disability days for a change in concentration equal to the interquartile range of the 2-week average pollutant concentration). PM2.5 was more strongly associated with disability days in the warm season. Results of multipollutant models were difficult to interpret in that effect sizes appeared to be influenced by covariation among pollutants. With the exception of warm season results for PM2.5, findings were not sensitive to alternative analytical approaches. While these results are suggestive of significant effects of the urban air pollution mix at relatively low ambient concentrations, the precise contribution of individual pollutants could not be determined.