Health-based air quality objectives (HBAQOs)

Health-based air quality objectives will identify safe exposure levels of outdoor air pollutants of concern for human health.

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Under the Air Quality Management System, the federal, provincial and territorial governments work together to revise and update the Canadian Ambient Air Quality Standards (CAAQS). There are CAAQS for 4 major outdoor air pollutants:

CAAQS have been developed to protect human health and the environment.

In addition to CAAQS, Health Canada is developing health-based air quality objectives (HBAQOs) as there are other pollutants in outdoor air that can be harmful to human health.


Health Canada uses HBAQOs to assess health risks. In comparison, the CAAQS represent government commitments to continuously improve air quality across the country, based on health effects, environmental effects, feasibility and achievability.

We will conduct public consultations on the HBAQOs before we finalize and publish them.

Process to prioritize outdoor air pollutants

Health Canada consulted federal, provincial, territorial, municipal and other air partners to identify priority pollutants for the development of HBAQOs. This process had 3 steps:

  1. Developing the inventory of pollutants considered to be candidates for HBAQO development

    Health Canada created a list of candidate air pollutants by compiling:

    • air pollutants identified internationally as potential priorities
    • pollutants commonly released to or measured in outdoor air in Canada
  2. Prioritizing based on health risk

    Health Canada scored and ranked candidate air pollutants according to:

    • concerns for human health
    • the potential for exposure in outdoor air in Canada
  3. Selecting final candidates

    Following consultation with federal, provincial, territorial and municipal governments and other air partners, Health Canada selected a group of priority candidate pollutants for HBAQO development. These air pollutants are:

    • arsenic
    • benzene
    • formaldehyde
    • carbon monoxide
    • PM10, that is, particles with a diameter of 10 microns and smaller

Contact us

If you would like more information on Health Canada's process to prioritize outdoor air pollutants for HBAQO development, please contact us at:

Telephone: 1-833-223-1014 (toll free)
Subscribe to the air quality email subscription list

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