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Air Quality Health Index

Air pollution is a concern for everyone who breathes. Air quality is of even more importance for those living with lung disease and those who work or exercise outdoors.

The Ontario Ministry of Environment and Climate Change provides air quality readings in different areas of the province through the Air Quality Health Index (AQHI).

The AQHI is an important tool that can help guide you in reducing your risks from the effects of air pollution. It’s now available throughout Ontario, providing current and forecast air quality readings and guidance on health risks.

What the AQHI measures

The AQHI measures these three important pollutants:

  1. Ozone (O3)
  2. Particulate matter 2.5 microns (PM2.5) in diameter and less (1 micron is 1/1000 of a mm)
  3. Nitrogen dioxide (NO2)

The AQHI scale

The AQHI scale goes from 1 to 10+. The lower the number, the better the air quality and the lower the health risk from outdoor air pollution. The scale below shows the AQHI values and their associated colours, and the categories from “low risk” to “very high risk”.

Air quality health index from 1 (low risk) to 10+(very high risk)
AQHI Categories, Values and Associated Colours

Are you at risk?

Use the chart below for steps to take based on the AQHI level and whether or not you are in the “at risk population”.

Air Quality Health Index Health Messages Steps to take
AQHI Health Messages

Tips to protect your breathing

Follow these tips to protect your lungs and breathing from air pollution:

  • Check the current and forecast maximums in your community at www.airqualityontario.com or www.airhealth.ca or at other media such as television, newspaper or radio
  • Follow the AQHI health messages based on whether or not you are in the “at risk population”
  • Avoid areas that have a higher pollution level, such as near major roads
  • Exercise indoors if the AQHI level is too high
  • Ask your health-care provider about protecting your lungs when air quality is poor
  • Sign up for air quality alerts at www.airqualityontario.com/alerts/signup.php or hear recorded messages at 1-800-387-7768 or 416-246-0411 (local in Toronto).

Protect your breathing by accessing your local AQHI readings at www.airhealth.ca