Air Quality Scale in Quebec and Montreal

Posted on July 16th 2015
Share: aqicn.org/faq/2015-07-16/air-quality-scale-in-quebec-and-montreal

Flag of Quebec.svg
The Fleurdelisé, flag of Quebec.
(attribution: wikipedia)

The Air Quality data for Montreal and Quebec has been available for a while, but we recently got few questions about the AQI scale used in this part of Canada. One of them is from Marie A., who asked:

I would like to know why the Air Quality Index on your web site is different from the AQI on the Montreal's website? Do you recalculate anything to meet the US EPA AQI standards? If so, how? With what data?

For example, date July 14th 2:00pm, most of the indexes on your website range from 53 to 65 (one index is 37) and it is supposed to be realtime AQI. On the website of Montreal city, date July 14th 2:00pm, most of indexes range from 16 to 37 and it is realtime AQI as well.

So, can you explain me the difference and what the standards details you are using?
This is indeed a very good question. and we will explain in this article the different scales in use, how the scales compare to each other, and how the convertion can be done.


oOo

As we explained in one of our previous articles, all the AQI figures published on the World Air Quality Index project are currently [1] using the US EPA standard. Neither Montreal nor Quebec are expection to this rule, so this confirms that the values displayed on the page city/montreal are using the US EPA standard.

This is the reason for the difference between the World Air Quality Index project readings and the Montreal city website ( montreal.qc.ca): The Montreal city EPA (Environment Protection Agency) is using its own proper AQI scale, which is clearly described on the same website. To make it slighly more "complex", Quebec is actually using another AQI scale (specified at this link) compared to Montreal (tabarnac!). And of course, Canada is using yet another scale, called AQHI for Air Quality Health Index - but that's something we already wrote about in another article.

The summary of Montreal and Quebec AQI breakpoints are listed in this table:

Pollutant Quebec Montreal
Averaging Period Reference Value Averaging Period Reference Value
Fine Particles (PM2.5) 3 hours 35µg/m3 3 hours 35µg/m3
Ozone (O3) 1 hour 82 ppb 1 hour 160 µg/m3
Nitrogen dioxide (NO2) 1 hour 213 ppb 1 hour 400 µg/m3
Sulfur dioxide (SO2) 4 minutes mobile 213 ppb 10 minutes mobile 500 µg/m3
Carbon monoxide (CO) 1 hour 30 ppm 1 hour 35 µg/m3


oOo

In order to convert the values to the US EPA standard, the raw concentrations expressed in milligrams or ppb/ppm (particle count per billion/million) are required. Unfortunately, neither Montreal nor Quebec county is providing those raw concentrations. Instead they are only providing the Air Quality readings already converted to their own respective AQI scales. But this actually not a problem, since the re-convertion to concentration can be done using this simple linear formula:
Raw concentration (pollutant) = Reference value (pollutant) * AQI }(pollutant) / 50
For instance, if an PM2.5 AQI value of 18 is publised on Montreal city website, then the raw concentration in milligrams is 18*35/50 = 12.6 mg/m3. Note that for Ozone, CO, SO2 and NO2 the unit is different for Quebec and Montreal (ppb for Quebec - US standard, and mg for Montreal EU standard), but that is just an additional convertion (partly explained in this article).

Note that the PM2.5 AQI is based on 3-hours average, while on the World Air Quality Index project, the hourly PM2.5 Instant Cast AQI reporting is used. Since it is not possible to deduct the hourly data from the 3 hours average, this actually means that the PM2.5 AQI reported on the World Air Quality Index project for Montreal and Quebec is not exactly an "Instant Cast" reporting.

oOo

So, last, here is the visual comparison of 3 AQI scales (US EPA, Quebec and Montreal) for PM2.5 and Ozone (note that for Ozone, the ppm unit is used - so the convertion from mg to ppm is done for Montreal).

One interresting point to notice is that both Quebec and Montreal are using the AQI value of 25 as the breakpoint between Good (green) and Aceptable (yellow), while for the US EPA, this breakpoint is set at 50. So, all in all, when comparing apple-to-apple with the right convertion and breakpoints in mind, the reported AQI range is very similar between the US EPA standard and Quebec / Montreal standards.



[1] We are now working on an option which will allow users to select any AQI scale they want.



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Note: This article is part of a series on Worlwide Air Quality scales.

For more information about specific countries or continent, please refer to thoses articles:
Thailand and Malysia
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India
-
China
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Hong Kong / Canada (Air Quality Health Index)
-
South America
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Australia
-
Quebec and Montreal
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Singapore
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Poland
-
Indonesia
.
For information about the 24 hours averaging used or Ozone and Particulate Matter (PM2.5), please refer to those two articles: Ground Ozone Index - PM2.5 Instant Cast


Click here to see all the FAQ entries
  • Nitrogen Dioxyde (NO2) in our atmosphere
  • Ozone AQI Scale update
  • Kriging Interpolation

  • Read or publish comments (they rely on Disqus)

    대기질 및 환경 오염 측정에 관하여 :

    대기질 지수 단계에 대하여

    AQI지수구분구간의미
    0 - 50좋음대기오염 관련 질환자군에서도 영향이 유발되지 않을 수준
    51 -100보통환자군에게 만성 노출시 경미한 영향이 유발될 수 있는 수준
    101-150민감군영향환자군 및 민감군에게 유해한 영향이 유발될 수 있는 수준
    151-200나쁨환자군 및 민감군(어린이, 노약자 등)에게 유해한 영향 유발, 일반인도 건강상 불쾌감을 경험할 수 있는 수준
    201-300매우나쁨환자군 및 민감군에게 급성 노출시 심각한 영향 유발, 일반인도 약한 영향이 유발될 수 있는 수준
    300+위험환자군 및 민감군에게 응급 조치가 발생되거나, 일반인에게 유해한 영향이 유발될 수 있는 수준
    (Reference: see airkorea.or.kr)

    대기질과 오염에 대해 더 많은 것을 알아보려면 위키피디아의 대기질 문서(영어)을 보거나 대기질과 건강에 대한 AirNow 가이드(영어)를 참조해보세요.

    매우 유용한 베이징의 의학박사 Richard Saint Cyr MD의 건강 관련 팁을 보려면 www.myhealthbeijing.com 의 블로그를 확인하세요.


    사용안내: 모든 대기 질 데이터는 발행 당시에 검증되지 않았으며, 품질 보증으로 인해 이러한 데이터는 예고없이 언제든지 수정 될 수 있습니다. 세계 대기 품질 지수 프로젝트는이 정보의 내용을 편집함에있어 합당한 기술과 관심을 행사했으며 어떤 상황에서도 세계 대기 품질 지수 (World Air Quality Index) 프로젝트 팀 또는 그 대리인은이 데이터의 공급으로 인해 직접 또는 간접적으로 발생하는 손실, 상해 또는 손해에 대해 계약, 불법 행위 또는 기타의 책임을지지 않습니다.



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    Temperature unit:
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