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- The Canadian Air Quality Health Index (AQHI) has a similar approach as the DAPPS in that it sums the health effects of individual pollutants (Stieb et al, 2008). Relations between excess mortality and pollutant concentrations were not derived from WHO published RR-s (as in the DAPPs) but rather determined on the basis of Canadian urban air quality monitoring and mortality data. This is an important difference. Though the pure toxicity of pollutants can be regarded as constant and country or site independent, health outcomes of pollution episodes do differ depending on other factors, such as overall life expectancy, smoking habits and other life-style and environmental health factors. Likewise, the air pollution mixture can be rather site specific. The level of correctness achieved by the Canadian approach is therefore also a limitation: Stieb et al (2008) discussion their AQHI, mention that it is typical for Canadian urban environments and might not apply to rural areas. Hong Kong, intending to update their API with a Canadian style AQHI, will have to make their own epidemiological analysis to get the correct coefficients of for the AQHI calculation.
The Canadian AQHI cannot be summarised in concentration bands such as the other AQI-s
discussed. Some important features of the AQI are summarised below (Stieb et al 2008):
The AQHI is meant to enable the public to protect themselves from acute health effects of air pollution. The averaging time for all pollutants (including PM) was therefore set Page 35 of 43 AQ Communication D2.3/V7 part II to the past 3 hours (being a compromise between stable results and the shortest possible averaging time).
The AQHI should include at a minimum NO2, O3, and PM10 or PM2.5. Since most pollutants are mutually correlated these three capture (in the Canadian situation) the health effects of the occurring pollutant mixtures.
The communication material associated to the AQHI was developed and tested together with stakeholder groups. Categories were defined to take into account the relative frequency of the bands. ‘An excessive frequency of days at higher levels was avoided to avoid saturation of individuals who might than be inclined to ignore the index.’ Table A.5 health messages Canadian AQHI
A1.2 Policy/standards based indices Policy & standards based indices set the class borders relative to air quality standards or other (policy) considerations.9 The bands are to a large extent arbitrary (in the sense that they don’t depend on epidemiological evidence linking concentrations to health impacts) and can therefore be adapted to the prevailing concentrations. This way certain communication objectives can be better served such as assuring a fair frequency distribution of the bands and avoiding that the worst category occurs to often; and more importantly avoiding that the air quality always looks good whilst this is not true from a long-term exposure perspective (this is often a problem with health based indices).
In the UK the public reported this issue (G. Fuller, p.c.) and in the Netherlands we also encountered this confusion. In the review of the UK AQI (section 3.9) some attention is given to the problems of averaging times (COMEAP, 2011). They conclude that no ready solution exists to solve this problem. However they also mention (section 2.3) that ‘Health effects may occur even at low concentrations of particles and therefore an arbitrary index was devised.’ So, in order to convey an appropriate message (particle pollution is never safe) a grid was devised that suits the information objective. The fact that the UK adopted (and maintained after the review) this approach in an otherwise health based short-term exposure AQI shows how serious the issue is.
Two examples are given (though many exist):
Fist the EU CAQI that features the concept of mandatory pollutants and the traffic background approach (each area is represented by two AQI numbers) Second the Pearl River delta RAQI because it is regionally used in China.
As a matter of fact some of the health and behavioural advice AQI-s also use a standard to fix one of the bands.
If a short-term exposure standard exists it usually forms the difference between the ‘good’ and the ‘medium’ bands.
RAQI index The RAQI compares the prevailing daily concentrations to the set concentration targets for four pollutants. The four ratios thus obtained are summed. The RAQI therefore deviates from the often used ‘highest iAQI determines the AQI’ approach. See excerpts from: wwwapp.gdepb.gov.cn/raqi3/capi_ENG_detail.html
The RAQI is a measure of the aggregate level of major air pollutants. The RAQI for the Pearl River Delta (PRD) regional air quality monitoring network is derived from the concentrations of 4 major air pollutants, namely respirable suspended particulates (RSP or PM10), sulphur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3). The higher the index value, the higher the overall level of regional air pollution.
The RAQI is divided into 5 grades. The categorization of the RAQI grades, their corresponding
index values and air quality conditions are as shown below:
The formula for calculating the RAQI is as follows:
where Ic stands for the RAQI, an indicator of the aggregate pollution level of four pollutants, namely, SO2, NO2, PM10 and O3. With respect to SO2, NO2 and PM10, Ci means the daily average concentration while Ri represents the daily average concentration limit of the corresponding pollutants as specified in the Class 2 NAAQS (GB 3095 – 1996 – revised version). With respect to O3, Ci means the highest hourly average of a day while Ri represents the 1-hour average concentration limit in the Class 2 NAAQS. The Class 2 NAAQS (GB 3095 – 1996 – revised version) apply to residential, mixed commercial/residential, cultural, industrial and village areas. The concentration limits for various pollutants in the standards are listed in the table below.
A2. Apps and websites some examples Apart from the CNEMC and various EMC/city websites there are several other sources of air quality information. In this annex I discuss some of the websites and apps displaying information on China. This is not meant as an exhaustive review and whatever was not available in English (or could be translated by Google Chrome) isn’t discussed anyway.
A2.1 Apps At the time of writing the IOS app store had four (English language) air quality apps for China.
The review was done on the versions available on May 29 2013.
The app Beijing/Shanghai air quality only presents data for either city in the name of the app. The data is obtained from the US consulate/embassy only and only covers PM 2.5. Since other pollutants occasionally determine the index. So to present this as the AQI is wrong/misleading. Access to the daily report of the BJEPB is offered as well. (In Chinese, functionality unclear to me). The AQI used (Chinese or US) is not clear but I suspect it is the US. In 2014 the access to BJEPB has disappeared.
One app is simply called PM2.5 suggesting that it only deals with PM2.5. However inside the app information is given for the full range of six pollutants (requires some navigation to find it) as a two day trend. 10 The trend information is accompanied by meteo information.
The presentation is not very polished but is the most comprehensive combination of information that is released in all four apps. Data can be selected for a number of cities/monitoring sites. The fact that the background picture changes depends on the AQI level (from green park, blue sky, to muddy coloured scene with low visibility is a nice gimmick. The AQI used is not mentioned though I assume it is the US (brief check on levels and AQI). In 2014 the app has hardly developed and it doesn’t work as smooth as it used to (with latest ipad OS?).
Air Quality was an attractive app (2013) and currently (end 2014) is a very attractive and comprehensive app providing both MEP and US embassy/consulate data. All kind of selections are possible, cities can be compared; weather info is included. The app shows trends for the past hours, days and months. The app doesn’t provide the calculation background so the user can’t verify if the correct approaches were used for the hourly index calculation. A map with individual monitoring sites is provided and users can toggle between actual concentrations and the AQI.
The fact that cities across china can be compared makes the app interesting, the possibility to access trends and see the situation in town for different pollutants makes the app interesting to play with. The app is useful for many of the communication objectives identified. It is also not clear which AQI is used (US or China). However it does provide background information for each pollutant, including health effects, and provides There seems to be a link to this app and the website http://www.aqicn.info/?map see next section. Perhaps the app taps into the website for information and graphics?
reference to both the Chinese and US AQI grids. Well documented. Some health advice is given (open windows, suitable for sports, etc.) though it doesn’t follow the exact wording of the Chinese nor the US AQI11. Very nice app, hard to beat!
Air Quality China is an attractive app providing both MEP and US embassy/consulate data.
The user can select the cities and compare city averages to other Chinese cities. It shows nice graphs for monitoring sites for the last 24 hours and the last 30 days. You can select if the overall AQI shown is based on the city average, the average of your selection or the highest station in a city or the highest in your selection of monitoring sites. The app allows the user to select hourly and daily averaging times and the use of the US or the Chinese AQI (again a choice of four options). The displayed results don’t show what AQI option was selected, so someone who wants to compare the two and switches settings often can be misled. Apparently the feature was not included to be used in this – interesting - way The last two apps operate smoothly and have interesting features. NB: not all non-government apps are good/informative: I came across some dysfunctional and apps with a bad presentation and interface as well.
The ventilation advice is a risky as it might not be appropriate/correct. This was extensively discussed in the main text. Also the advice to wear/not to wear masks is questionable as only certain masks, and only if they are worn in the proper way, provide protection.
PM2.5: not the best interface but a very comprehensive set of data. Note that PM2.5 drops sharply as humidity drops. This could be due to a change in wind direction (unfortunately not shown). Providing a whole range of information makes people understand what drives the occurring air pollution. The app apparently relies on bits of international code: some menu items (as well as the adds in the free version) are in Dutch.
Air Quality: rich in features, decide what you want to see on the map; relative rankings of cities and monitoring sites. Making cities comparable can be part of raising awareness. Health advice in this app is nicely displayed with text and graphics but the remarks on wearing masks and ventilation are not the official advice (and questionable in my view).
- The website http://www.aqicn.info/?map allows the visitor to compare air quality in China to that in many other Asian countries in real time. This website (available since 2008?) used to have the Chinese API but has now switched to the US-AQI. The website has a FAQ section where questions received, are answered. You can leave comments, it has a poll, etc. so facilities for
user interaction and feedback are available. All in all it is pretty complete in documenting what it does and where information comes from. The site is linked to the app PM2.5 (see above).
It also provides information on a type of mask that is able to reduce PM2.5 particles though it doesn’t provide information on how to wear masks (as the US embassy website does).
The site is interesting as it allows the visitor to see air quality in Asia. By converting all raw measurement data that the site manages to obtain and presenting everything in the same AQI it assures that the data are comparable (assuming all calculations are done correctly and that true raw data is used). How the site manages monitoring data from areas where less than the full range of observations are used is not clear. As far as I know it is one of the few cross-border air quality comparison sites and the only one (?) covering Asia.
In 2014 this site now covers much of the world, including Europe and the US.
Other websites covering air quality in several countries at the same time:
www.airqualitynow.eu (some 100 European cities - 2006) www.obsairve.eu (European monitoring data, supported by modelling - 2012)