Ministère de l'Environnement
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2018 Annual Regional Air Quality Index Statistics

The Air Quality Index (AQI) was calculated for 24 meteorological regions in 2018, with Montréal subdivided into four sub-regions.

The percentage of “Good” or “Acceptable” AQI days varied from 91% in Montréal (332 out of 365 days) to 100% in the Mont-Laurier, Laurentides, Montmagny, Estrie, Gatineau, Haute-Gatineau, Vaudreuil-Huntingdon, Beauce, Québec, and Lachute regions.

Air quality was deemed “poor”* most often in Montréal in a proportion of 9% (33 out of 365 days). This was only a slight variation from the 2017 proportion of 8%.

Overall, the AQI was rated “good” 53% of the time, “acceptable” 45% of the time and “poor” 2% of the time. Compared to 2017, the AQI “acceptable” figure increased by 9%, while the “good” figure decreased.

*This is the case when the concentration of at least one of the contaminants used to calculate the AQI is greater than the hourly reference value at any one of the regional stations.

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