Previously, NEA provides 3 hours average for both PM10 and PM2.5 reading on their website. But for public data announcement, they used PM10 (eg over the media)
But the PM2.5 is always much higher than PM10. So now they use 24 hours average on PM2.5 to bring the figure lower and closer to that of PM10 (which is still base on 3 hours averaging).
Data for public safety should be simple, clear and easy to understand. Why confuse the public with different reference of PM particle size and also different hours of averaging ? Besides, the health advisory reference level for PM10 and PM2.5 is also different. (PM10 above 100 PSI is unhealthy, while PM2.5 above 40 is unhealthy).
NEA should adopt best safety practice and use PM2.5 reading given on the spot. What is the point of giving us historical reading as we cannot make decision and take precaution base on what is already over. Their current messy method of PSI reading reporting is a disservice to the public.
PM2.5 are respiratory hazard and some of those PM 2.5 could be carcinogenic. We would want to avoid if not minimise exposure to these 2.5 micron particles. We should never carry on as usual and get used to the haze ! Complacency is an enemy to our health.