Air quality index

An Air Quality Index (AQI) reading below 32 indicates good or very good air quality. A reading between 32 and 49 indicates moderate air quality, and an AQI reading from 50 to 99 indicates poor air quality. A reading over 99 indicates very poor air quality.

What is the air quality index (AQI)?

The Air Quality Index (AQI) from the Ministry of Environment and Climate Change is an indicator of air quality, based on air pollutants that have negative effects on human health and the environment. The pollutants include ozone, fine particulate matter, nitrogen dioxide, carbon monoxide, sulfur dioxide and total reduced sulfur compounds.

If the AQI falls below 32, air quality is considered good or very good. An AQI reading between 32 and 49 indicates moderate air quality, and an AQI reading from 50 to 99 indicates poor air quality. A reading over 99 indicates very poor air quality.

For current real-time air quality data from AQI monitoring sites across Ontario, please visit Air Quality Ontario.

How can I get air quality information?

1. By visiting the Air Quality Ontario website. This site provides AQI readings, ambient air pollution data and air quality forecasts, as well as information on what to do when a smog alert is issued.
2. You can also subscribe to the Ministry of Environment’s Smog Alert Network, and receive an automatic email whenever the ministry issues a smog watch or smog advisory.
3. By telephone you can get AQI readings from recorded messages by calling 1.800.387.7768 toll-free. To get AQI readings in French, call 1.800.221.8852 toll-free.

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This item was last modified on June 24, 2015