TV haze broadcast of 1 hr reading is NOT in PSI

Many are not aware that there is a difference in PSI reading and ug/m3 (microgram per meter cube). This is because the health warning levels are different.

NEA 24 hour average reading is in PSI. However NEA 1 hour average reading is in ug/m3.

S'pore official health advisory is based on 24 hours average PSI reading. For our personal health concern, we should base our activities on 1 hour real time reading ie to stay indoor or not, when to use face mask.

Table 1 : Health advisory by NEA in PSI for 24 hour averaged reading:
0 -50        Good
51-100     Moderate
101-200   Unhealthy
201-300   Very Unhealthy
above 300 Hazardous

Table 2 : Health advisory by NEA in ug/m3 for 1 hour averaged reading,
0-55        Normal
56-150    Elevated 
151-250  High
above 250 Very High

Table 3 below is the previous descriptive reference from NEA website from past years which is no longer found in their current site :

Table 3:
Index Category           PSI            24hrPM2.5 ug/m3
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

As there is no safety limit given for 1 hr reading, we could take the unhealthy range level as 56 ug/m3 and above.

For the haze reading broadcast over TV provided by NEA, the 24 hr data is in PSI. But the 1 hr data does not have a unit a measurement attached to it - this may mislead the public into thinking it is in PSI. We can see from Table 3 - unhealthy level is at 56 ug/m3.

NEA is not helping the public as they could have easily converted the reading into PSI which the public is familiar with. They could have also used the same descriptive for both 24 and 1 hour data. Public may not understand that 'elevated' is 'unhealthy'.  


NOTE : 

1) US EPA adopts 35 ug/m3 as unhealthy limit for 24 hrs PM2.5 which is a more stringent standard than S'pore.

2) For real time 1 hourly data on haze please refer to : aqicn.org  - which provides air pollution Air Quality Index (AQI) for more than 60 countries in the world. AQI descriptive :

0-50                 Good

51-100             Moderate

101-150           Unhealthy for sensitive groups

151-200           Unhealthy

201-300           Very Unhealthy

301-500           Hazardous