Effects of air pollution on emergency room visits for respiratory illnesses in Montreal, Quebec

Am J Respir Crit Care Med. 1997 Feb;155(2):568-76. doi: 10.1164/ajrccm.155.2.9032196.


As an approach to evaluating the public health burden from current air pollution levels, we examined the relationship of daily emergency room (ER) visits for respiratory illnesses (25 hospitals, average 98 visits/d) to air pollution in Montreal, Canada, from June through September, 1992 and 1993. Air pollutants measured included ozone (O3), particulate matter diameter < 10 microm (PM10) and < 2.5 microm (PM2.5), the sulfate fraction of PM2.5 (SO4), and aerosol strong acidity (H+). Temporal trends, autocorrelation, and weather were controlled for in time-series regressions. For 1992, no significant associations with ER visits were found. However, 33% of the particulate data were missing. For 1993, 1-h maximum O3, PM10, PM2.5, and SO4 were all positively associated with respiratory visits for patients over 64 yr of age (p < 0.02). An increase to the mean level of 1-h maximum O3 (36 ppb) was associated with a 21% increase over the mean number of daily ER visits (95% confidence interval [CI]: 8 to 34%). Effects of particulates were smaller, with mean increases of 16% (4 to 28%), 12% (2 to 21%) and 6% (1 to 12%) for PM10, PM2.5, and SO4, respectively. Relative mass effects were PM2.5 > PM10 >> SO4. Ozone and PM10 levels never exceeded 67 ppb and 51 microg/m3, respectively (well below the U.S. National Ambient Air Quality Standards of 120 ppb and 150 microg/m3, respectively). The present findings have public health implications with regard to the adverse health effects of urban photochemical air pollution on older individuals.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Air Pollutants / adverse effects*
  • Air Pollutants / analysis
  • Child
  • Child, Preschool
  • Emergency Service, Hospital / statistics & numerical data*
  • Epidemiologic Methods
  • Female
  • Humans
  • Infant
  • Lung Diseases / epidemiology
  • Lung Diseases / etiology*
  • Male
  • Middle Aged
  • Ozone / analysis
  • Quebec / epidemiology
  • Urban Health


  • Air Pollutants
  • Ozone