What is the Can-EQI?

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The Canadian Index of Environmental Quality (Can-EQI) is a composite measure of environmental conditions at the neighbourhood level for Canada's largest 30 cities. The index is comprised of nine indicators, including air quality (fine particulate matter and nitrogen dioxide), greenness (NDVI), distance to blue spaces (oceans, lakes, rivers), lengths of major roads, distance to fossil fuel power plants, UV exposure, heat wave and cold wave temperatures. Data distributions for each indicator are split into deciles (10 categories) and a value between 1 and 10 is assigned to data for each indicator depending on its relationship to human health. For example, lower EQI scores are assigned to higher concentrations of air pollution, whereas higher scores are assigned to areas closer to blue spaces. The score for each indicator is multiplied by 1.1 so that the sum of all scores is out of a potential score of 100. Datasets were averaged over a five-year period centered on the 2016 census year (2014-2018).

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Can-EQI values are calculated for dissemination areas or DAs. DAs are small areas typically comprised of between 400-800 people and is the smallest geographic areas for which Canadian census data are distributed by Statistics Canada. For each city we selected DAs that were roughly aligned with "population centres" but added or removed DAs if they included largely commercial or industrial activities (e.g. airports) or did not exhibit "urban" characteristics. The current version of the index includes 28,026 DAs and 55% of the Canadian population.

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Considerations

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A natural tendency when presented with scores for different cities and neighbourhoods is to rank or order from highest to lowest and to compare scores. There are several issues to keep in mind when evaluating scores from the Can-EQI:

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• ​Can-EQI scores are calculated at the DA level of geography. Scores for each city are an average or median of the scores for all DAs within the city. Figure 2 in the article shows the spread of scores across all DAs within each city.

• Can-EQI scores are "relative". Values for indicators that comprise the score are drawn from a distribution of values for all cities and the DAs within them. Therefore the scores are only relative to conditions elsewhere and not to any desirable score based on guidelines or regulation.

• In general, the quality of the environment in Canada and in most Canadian urban centres is high when compared to urban areas in other countries of similar population size. For example, concentrations of several air pollutants have been in decline for several decades.

• Can-EQI scores are calculated for each DA and thus do not account for the ability of those who live in any DA to access environments elsewhere. We know from mobility studies that people do not spend all of their time in their residential neighbourhood (much of it is sleeping) and realistically experience environmental conditions in other locations, better or worse.

For further information:

Davis Z, de Groh M, Rainham DG. The Canadian Environmental Quality Index (Can-EQI): Development and calculation of an index to assess spatial variation of environmental quality in Canada's 30 largest cities. Environment International 2022; 170: 107633. https://doi.org/10.1016/j.envint.2022.107633.

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