How valid is our PSI reading?

There are some days that I can FEEL, SEE and SMELL the unbearable particulates in the air. And yet at night when I watch the news, NEA always assure the public that the PSI reading is in the moderate range of <100. href="http://app.nea.gov.sg/psi/">http://app.nea.gov.sg/psi/] and realise that they have their PSI reading based on the detection of PM10 (particulate matter <10um). href="http://www.epa.gov/air/particles/">http://www.epa.gov/air/particles/], EPA groups particle pollution into two categories:

• "Inhalable coarse particles," such as those found near roadways and dusty industries, are larger than 2.5 micrometers and smaller than 10 micrometers in diameter [PM10].
• "Fine particles," such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries and automobiles react in the air [PM2.5]

So, the big question is: Why is Singapore NEA still monitoring PM10 as the criteria for our PSI readings? It's PM2.5 that is more relevant for our case! PM2.5 are the most dangerous particulates. Because of their small size, they reside in our respiratory system for a very long time. No doubt PM2.5 is difficult to monitor and USEPA itself doesn't even list that as a monitoring requirement, but PSI is basically crap if they don't reflect the core issue! And why must our standards be defined based on USEPA? Set our own!

Lastly, NEA briefly mentioned that readings were monitored " through a number of telemetric networks of monitoring stations positioned strategically throughout Singapore". No specific locations were given. Which makes me wonder...so how strategic is strategic?