Air Quality Health Index (AQHI)

What is the Air Quality Health Index (AQHI)?

The Air Quality Health Index is a scale designed to help you understand what the quality of the air around you means to your health. It is a tool developed by health and environmental professionals to communicate the health risk posed by air pollution.

It is designed to help you make decisions to protect your health and the environment by:

  • Limiting short-term exposure to air pollution
  • Adjusting your activity during episodes of increased air pollution and encouraging physical activity on days when the index is lower
  • Reducing your personal contribution to air pollution

The Index provides specific advice for people who are especially vulnerable to the effects of air pollution as well as the general public.

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What is the scale for the new AQHI?

The AQHI is measured on a scale ranging from 1-10+. The AQHI index values are also grouped into health risk categories as shown below. These categories help you to easily and quickly identify your level of risk.

  • 1-3 Low health risk
  • 4-6 Moderate health risk
  • 7-10 High health risk
  • 10 + Very high health risk

More information on the scale and the AQHI categories External Link.

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How is Ontario’s AQHI calculated?

The formula developed to calculate the Air Quality Health Index is based on research conducted by Health Canada using health and air quality data collected in major cities across Canada.

The Air Quality Health Index represents the relative risk of a mixture of common air pollutants which are known to harm human health. Three pollutants were chosen as indicators of the overall outdoor air mixture:

  • Ground-level ozone (O3)
  • Fine particulate matter (PM2.5)
  • Nitrogen dioxide (NO2)

In Ontario, the AQHI number also considers hourly comparisons of individual pollutant concentrations to Ontario’s Ambient Air Quality Criteria (AAQC).
If hourly air pollutant concentrations are higher than Ontario’s AAQC, and the AQHI value is in the low or moderate risk categories, then the Air Quality Health Index value is replaced with the appropriate High or Very High risk value. This adjustment is relevant for:

  • Ozone
  • Nitrogen dioxide (NO2)
  • Sulphur dioxide (SO2)
  • Carbon monoxide (CO)
  • Total reduced sulphur (TRS) compounds

If the following pollutant thresholds are exceeded when the Air Quality Health Index is Low or Moderate risk (6 or less), then the AQHI is replaced with the appropriate High or Very High risk value (7 or greater):

  • 80 parts per billion for ozone
  • 200 parts per billion for nitrogen dioxide
  • 250 parts per billion for sulphur dioxide
  • 30 parts per million for carbon monoxide
  • 27 parts per billion for and total reduced sulphur compounds

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What is the difference between the Air Quality Index I am used to and the AQHI?

The Air Quality Health Index is a new approach to communicating about air quality that offers more protective health information. The Air Quality Health Index presents the immediate health risk of the combined effects of the air pollution (smog) mixture.

The Air Quality Health Index is a personal health protection tool for individual Ontarians, especially those most at risk: children, seniors, and people with diabetes, heart and lung disease. The old Air Quality Index had a scale of 0-100+, with values usually in the range of 10-60, and poor air quality designated as values above 50. The Air Quality Health Index is a simplified scale from 1-10+ with three categories “low, moderate and high risk” within this range.

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When did Ontario stop reporting the Air Quality Index?

On June 24, 2015, in partnership with Environment Canada, the Ontario Ministry of the Environment and Climate Change adopted the national Air Quality Health Index to report air quality in Ontario.

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What can the AQHI tell me about the health risks I may experience due to the current local air quality?

The Air Quality Health Index provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality. Occasionally, when the amount of air pollution is abnormally-high, the number may exceed 10.

The higher the number, the greater the health risk and our need to take precautions.

The index describes the level of health risk associated with this number as ‘low’, ‘moderate’, ‘high’ or ‘very high’, and suggests steps we can take to reduce our exposure.

It also forecasts local air quality and provides associated health advice.

The index does not measure the effects of odour, pollen, dust, heat or humidity on your health.

You can refer to Today’s Air Quality to check the quality of outdoor air in Halton before heading off to work or play. And you can use the forecasts to plan your activities, whether over the next hour or the next day.

Seniors, children and people suffering from diabetes, heart or lung disease, can use the index to assess the immediate risk air pollution poses to your health and take steps to lessen that risk.

Even if you’re relatively healthy, fit and active, you can consult the index to decide when and how much to exercise or work outdoors.

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How can I find the current AQHI for my area?

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