The Air Quality Health Index (AQHI) is a scale designed in
Canada to help understand the impact of
air quality on health. It is a health protection tool used to make decisions to reduce short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution. The Air Quality Health Index also provides advice on how to improve air quality by proposing behavioral change to reduce the
environmental footprint. This index pays particular attention to people who are sensitive to air pollution. It provides them with advice on how to protect their health during air quality levels associated with low, moderate, high and very high health risks.
History
Air quality in
Canada has historically been reported by the
US Air Quality Index in various provinces. Significantly, AQI values reflect air quality management objectives, which are based on the lowest achievable emissions rate, and not exclusively concern for human health. The AQHI was created with a different goal - to report on the specific health risks posed by air pollution. As such, the AQHI represents a paradigm shift in communicating air quality information to the public.
The Air Quality Health Index (AQHI) is a federal program jointly coordinated by
Health Canada
Health Canada (HC; french: Santé Canada, SC)Health Canada is the applied title under the Federal Identity Program; the legal title is Department of Health (). is the Structure of the Canadian federal government#Departments, with subsidiary unit ...
and
Environment Canada
Environment and Climate Change Canada (ECCC; french: Environnement et Changement climatique Canada),Environment and Climate Change Canada is the applied title under the Federal Identity Program; the legal title is Department of the Environment ( ...
. However, the AQHI program would not be possible without the commitment and support of the provinces, municipalities and NGOs. From air quality monitoring to health
risk communication Risk communication is a complex cross-disciplinary academic field that is part of risk management and related to fields like crisis communication. The goal is to make sure that targeted audiences understand how risks effect to them or their communit ...
and community engagement, local partners are responsible for the vast majority of work related to AQHI implementation.
The AQHI has been rolled out across Canada and has replaced the AQI as the public face of air quality information.
Originally launched as a pilot project in the
British Columbia Interior
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in 2005 followed by
Nova Scotia in 2006 and Toronto in 2007, as of 2016 it was implemented in 122 locations across Canada.
Overview
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 AQHI provides a local air quality current value as well as a local air quality maximums forecast for today, tonight and tomorrow and provides associated health advice.
As it is now known that even low levels of air pollution can trigger discomfort for the sensitive population, the index has been developed as a continuum: The higher the number, the greater the health risk and 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 that can be taken to reduce exposure.
Formula inputs
The formulation of the national AQHI is based on the observed relationship of
nitrogen dioxide (NO
2), ground-level
ozone (O
3) and
fine particulate matter
Particulates – also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) – are microscopic particles of solid or liquid matter suspended in the air. The ter ...
(PM
2.5) with mortality from an analysis of several Canadian cities. Significantly, all three of these pollutants can pose health risks, even at low levels of exposure, especially among those with pre-existing health problems.
When developing the AQHI, Health Canada's original analysis of health effects included five major air pollutants: airborne particulate matter, ozone, and nitrogen dioxide (NO
2), as well as
sulphur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
(SO
2), and
carbon monoxide (CO). The latter two pollutants provided little information in predicting health effects and were removed from the AQHI formulation.
The AQHI does not measure the effects of odour,
pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
, dust, heat or humidity.
Calculation
The national AQHI is based on three-hour average concentrations of ground-level ozone (O
3), nitrogen dioxide (NO
2), and fine particulate matter (PM2.5). O
3 and NO
2 are measured in parts per billion (ppb) while PM2.5 is measured in micrograms per cubic metre (µg/m
3).
The AQHI is calculated on a community basis (each community may have one or more monitoring stations).
First, the average concentration of the three substances (O
3, NO
2, PM2.5) is calculated at each station within a community for the 3 preceding hours. This is considered valid only if at least 2 out of 3 hours are available at the station. If more than 1 of the preceding 3 hours is missing the station average is set to "Not Available". This part of the process results in three "station parameter averages" for each station.
Second, the 3 hour "community average" for each parameter is calculated from the 3 hour substance averages at the available stations. If no stations are available for a parameter, that parameter is set to "Not Available". This part of the process results in three community parameter averages.
Third, if all three community parameter averages are available, a community AQHI is calculated. The formula is: