From 1 April 2014 onwards, the 24-hour PM2.5 concentration levels has been Incorporated into the PSI. The PSI now reflects a total of 6 pollutants – sulphur dioxide (SO2), particulate matter (PM10) and fine particulate matter (PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3).
Under the new PSI system, the health advisory will be based on the new 24-hour PSI as it now directly takes into account PM2.5.