I happened to check the NEA haze reporting site on 19 Oct 15, Mon at 10pm. I was shocked to note that the 1 hr average PM2.5 reading was 442 microgram per cubic meter for West Spore, which was worst hit by haze that night. (it hit 471 at 11 pm).
I noted down the various reporting on NEA as there is a wide variation in the data range. These readings are all from NEA site as at 10pm on 19/10/15 :-
* 24 hrs average PM2.5 = 89 microgram per cubic meter, which translated to 138 PSI
* 3 hrs average = 152 PSI
* 1 hr average PM2.5 = 442 microgram per cubic meter.
NEA does not translate 1hr PM2.5 into PSI
I looked at the real time reporting on Aqicn website and it was 214 PSI.
We can see that the NEA averaged 24 hrs and 3 hrs data do not reflect that the current situation and there is a wide margin between them and Aqicn real time reading.
Officially, based on NEA averaged 24 hrs data - it was in the unhealthy range only.
However, Aqicn real time reflected that it was at very unhealthy range.
As for NEA data given in microgram per cubic meter, most folks are not familiar with the unit of measurement and its associate level of health advisory is also not widely known to public.
Officially, our health advisory is only link to 24 hrs average PSI.
Just like 3hrs PSI reading, NEA 1 hr PM2.5 is not link to health advisory.
Index Category PSI 24hrPM2.5 in microgram per cubic meter
Good 0-50 0-12
Moderate 51-100 13-55
Unhealthy 101-200 56-150
Very Unhealthy 201-300 151-250
Hazardous above 301 above 251
Knowing that the real time data will be higher than the NEA 1hr average which at 442-471 is pretty alarming given that the unhealthy range is 56 microgram per cubic meter. Since there is no health advisory for 1 hrs, the sensible safety approach is to adopt the 24 hrs health advisory.
US EPA adopts 35 microgram per cubic meter for 24 hrs PM2.5 which is a more stringent standard than S'pore.
In conclusion, it is obvious that NEA needs to improve their method of reporting which is currently confusing and yet does not reflect the current situation. NEA 24 hrs PSI healthy advisory only tells us if we have been exposed, what has been our exposure level. BUT it does not tell us what will be our real time exposure for us to be proactive in taking safety precautions.
What is the point of giving 3 hrs average when it neither reflect current situation nor is it link to health advisory? 1 hr average PM2.5 better reflects the current situation but it is also not link to health advisory. Besides, public are not familiar with its unit of measurement.
- NEA should educate the public on it just like they do with PSI health index category.
- Provide the microgram per cubic meter table next to the PSI health index table (we have to dig it up as not easily accessible)
- Provide public with real time 1 hour PM2.5 data (without averaging it down)
- Convert it to PSI reading (to minimise public confusion)
- Remove the 3 hrs averaged PSI data as it is useless