- What is Ontario’s Air Quality Index?
- How can I find out what the AQI is?
- How is the AQI determined?
- What do the AQI readings mean?
- Information and Resources
What is Ontario’s Air Quality Index?
The Ministry of the Environment is a partner in a pilot project launched by Toronto Public Health, Environment Canada and Health Canada to provide the public with information on the health risks associated with various levels of smog. The Toronto project is the first pilot project being conducted in Ontario for the national Air Quality Health Index being launched by the federal government. It relies on air quality data from MOE’s air monitoring network to determine health risks. If you require more information on the pilot project, please visit the Toronto Public Health AQHI site.
The Air Quality Index (AQI) is an indicator of outdoor air quality in Ontario. The lower the AQI, the better the air quality.
Using a network of air monitoring stations, 40 state-of-the-art AQI monitoring stations, the Ministry of the Environment takes real-time air quality data from the monitoring sites and produces AQI reading for each location. The ministry AQI readings are reported to the public and news media at set intervals each day. The data is also used to issue smog watches and advisories.
Six key air pollutants are monitored by the ministry as part of the AQI - sulphur dioxide, ozone, nitrogen dioxide, total reduced sulphur compounds, carbon monoxide and fine particulate matter. These pollutants were chosen because they have an adverse effect on humans and the environment at high levels.
How can I find out what the AQI is?
You can access the index values by calling the ministry's automatic
telephone answering device (English recording:1-800-387-7768
or in Toronto 416-246-0411. French recording: 1-800-221-8852).
The AQI can also be obtained from the ministry's Web site at www.airqualityontario.com
How is the AQI determined?
At the end of each hour, the concentration of each pollutant
that the AQI station monitors is converted into a number ranging
from zero upwards, using a common scale, or index. The pollutant
with the highest number at a given hour becomes the AQI reading.
As the air quality changes, the AQI reading increases or decreases.
The lower the AQI reading, the cleaner the air.
What do the AQI readings mean?
The AQI scale ranges from 0 to 100. Higher numbers mean higher health risks. A Smog Watch is issued when there is a 50% chance of a smog day within the next 3 days. When the AQI is expected to get higher than 50 in the next 24 hours, a Smog Alert (or Smog Advisory) is issued.
If the air quality value is below 32, the air quality is considered relatively good.
If the AQI value is in the range of 32 to 49 (moderate category), there may be some adverse effects on very sensitive people.
An index value in the 50 to 99 range (poor category), may have some short-term adverse effects on the human or animal populations, or may cause significant damage to vegetation and property.
An AQI value of 100 or more (very poor category) may cause adverse effects on a large proportion of those exposed.
To learn about AQI levels in your community, check out www.airqualityontario.com.
Information and Resources
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Last modified: July 19 2007.