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Richard T. Burnett,¹ Sabit Cakmak,¹ Jeffrey R. Brook,² and Daniel Krewski¹

¹Environmental Health Directorate, Health Canada, Ottawa, Ontario, Canada; ²Atmospheric Environment Service, Environment Canada, Downsview, Canada

Abstract

In order to address the role that the ambient air pollution mix, comprised of gaseous pollutants and various physical and chemical measures of particulate matter, plays in exacerbating cardiorespiratory disease, daily measures of fine and coarse particulate mass, aerosol chemistry (sulfates and acidity) , and gaseous pollution (ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide) were collected in Toronto, Ontario, Canada, in the summers of 1992, 1993, and 1994. These time series were then compared with concurrent data on the number of daily admissions to hospitals for either cardiac diseases (ischemic heart disease, heart failure, and dysrthymias) or respiratory diseases (tracheobronchitis, chronic obstructive lung disease, asthma, and pneumonia) . After adjusting the admission time series for long-term temporal trends, seasonal variations, the effects of short-term epidemics, day of the week effects, and ambient temperature and dew point temperature, positive associations were observed for all ambient air pollutants for both respiratory and cardiac diseases. Ozone was least sensitive to adjustment for the gaseous and particulate pollution measures. However, the association between the health outcomes and carbon monoxide, fine and coarse mass, sulfate levels and aerosol acidity could be explained by adjustment for exposure to gaseous pollutants. Increases in ozone, nitrogen dioxide, and sulfur dioxide equivalent to their interquartile ranges corresponded to an 11% and 13% increase in daily hospitalizations for respiratory and cardiac diseases, respectively. The inclusion of any one of the particulate air pollutants in multiple regression models did not increase these percentages. Particle mass and chemistry could not be identified as an independent risk factor for the exacerbation of cardiorespiratory diseases in this study beyond that attributable to climate and gaseous air pollution. We recommend that effects of particulate matter on health be assessed in conjunction with temporally covarying gaseous air pollutants. Key words: air pollution, heart disease, ozone, particulate matter, respiratory disease. Environ Health Perspect 105:614-620 (1997)

Address correspondence to R.T. Burnett, Environmental Health Directorate, Health Canada, 203 Environmental Health Center, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0L2.

We thank the Ontario Ministry of Health for providing the hospital admissions data and the Ontario Ministry of Environment and Energy for providing the gaseous pollution data.

Received 11 December 1996 ; accepted 25 February 1997.