Green Roof Resource

With the opening of the Olympic Games a few days away, air quality in the city is increasingly a concern. It is now possible to view air quality around the city thanks to a joint effort by Mapufacture, Inc. and Fortius One. The map shows values from air quality sampling stations around Beijing, China.

The air pollution index (API) indicates air quality for SO2, NO2, and PM10 (particulate matter that is 10 micrometers in diameter or less). The API cannot be directly compared to other air quality indices from other locations. The USA and Canada both use AQI, air quality index, which is similar to API but the indices are set according to different formulas based upon concentration. Hong Kong uses a different API, which can cause confusion when comparing the air quality of the two cities. While the indices cannot be compared, each index is used to evaluate when the air quality is safe or dangerous to public health according the location’s guidelines. The API for Beijing has the following ratings:

Generally, an AQI or API is set such that ratings of 100 or below are safe while ratings above 100 may be dangerous to at least some of the population. However, the formulas vary, and the specific concentration of that threshold varies according to the country or location where the index is used.

The World Health Organization (WHO) has established guidelines according to concentration, which is much more straightforward. Using concentration allows for comparison of air quality across borders. However, even the standards issued by the WHO are not standardized across pollutants (in time) as you can see below.

Source: WHO. 2006. WHO Air Quality Guidelines for particulate matter, ozone, nitrogen dioxide, and sulfur dioxide. WHO/SDE/PHE/OEH/06.02

While we can now view daily air quality in Beijing, where within the city the data is taken, and the proximity of the sampling stations to the Olympic venues, we are not able to compare it to WHO standards. Nevertheless, this is still pretty neat.