Forum peeps, I've posted this before but the air tonight made me think it's time to post again. Here is a link to the real air quality index for SP: http://aqicn.org/city/singapore/central/
These guys use all the data provided by Singapore to calculate the index. The level of "harm" attached to different numbers in the scale is based on EPA standards. For some reason Singapore only relates their measurement of possible harm/health concerns to PSI, which is an outdated way of doing it. On any given day the above index will have a worse overall "rating" than that communicated by the NEA because of this. No idea why the NEA doesn't use this method as they do post all the individual pollutant measurements publicly...and really they are usually pretty good at these types of things.
Perhaps if enough people start referring to this instead of PSI they'll relent.