From ‘Hourly PSI readings would allow for better decision-making’, 28 Sep 15, Voices, Today
(Tan Zhi Rui): Amid the annual haze, I would like to again strongly make the case for the National Environment Agency (NEA) to provide hourly Pollutant Standards Index (PSI) readings instead of three-hour averages.
Singapore is a small country and a slight shift in prevailing winds can cause sudden significant changes in air quality. With a three-hour-average PSI, lower PSI levels for the earlier two hours can lower the reading when the haze has already reached a hazardous level in the third hour.
The NEA’s FAQs on PSI webpage states that its health advisory is based on the 24-hour PSI as it is a “better reflection of the total exposure”, and health effects have been mostly studied based on this measure. In comparison, the three-hour PSI is only “an indicative measure” that the public may use “to make adjustments to their daily activities if they wish to do so”.
I understand that public health planning is more effectively done on a daily, 24-hour basis. However, logically and given a choice, most people would refer to a shorter time frame to avoid exposure to the worst hours of the haze.
While the use of three-hour averages may moderate PSI readings and prevent undue panic, it is irresponsible not to provide a more accurate hourly measure for Singaporeans to protect themselves, especially when the NEA has the data.
This is particularly incongruous given that the hourly PM2.5 readings are available on the NEA website, which are equally “highly variable when the wind drives smoke haze from place to place” as stated by the NEA.
In NEA director Fong Peng Keong’s response, he cited ‘insufficient evidence’ from recent studies of sub-daily or shorter PM2.5 exposure for the ‘development of a 1-hour PSI based on exposure to PM2.5 for a 1 hour period’. In 2013, Minister Grace Fu urged the public to pay more attention to the 24 hour reading instead of the fluctuating 3-hourly average. Ng Eng Hen said giving 3 separate readings would ‘confuse’ the public. You’re talking about people who’re accustomed to dealing with all sorts of national health coverage schemes. So nope, we won’t be ‘confused’. We’re a smart nation. We voted the PAP back into power, for God’s sake.
The Government’s argument is that 24 hour readings are ‘backed by long-term epidemiological studies’, and are internationally accepted methods of assessing the health impact of air quality, but doesn’t explain whether these studies take into account tiny nations like ours when the 3 hour average can fluctuate from low 200’s in the afternoon and drop to 80 by late evening (like yesterday 3 Oct 2015, for example).
There was a time in 2006 when the NEA didn’t even promote 3 hourly readings, citing ‘unnecessary alarm‘ if these were published instead of the 24 hour readings. These days, you don’t even need to check the actual PSI to get ‘alarmed’ by the haze. Simply looking out of the window and taking a sniff would do (though the NEA later clarified that low visibility may not mean a high PSI). Or you could check out this ‘no bullshit PSI readings’ website if you really want to know what the one-hourly PSI is. But honestly, aside from statisticians and academics, how many of us actually care about the 24-hour PSI? Since 2006, we’ve complained that it has no practical use, and only serves as ‘post-mortem’ data for the good folks at NEA to crunch before the next haze comes around. It’s probably as useful a gauge as today’s weather if you’re wondering whether to bring the brolly out tomorrow. Even if you had exposed yourself to what’s considered a ‘very unhealthy’ 24 hour PSI for just one day, nobody will be able to tell you for certain your risk of getting lung or heart disease in 5 years.
There’s no reason why our top scientists in NEA would not be able to derive one-hour PSIs on the back of a napkin. So my guess is that they’re afraid of people overreacting to spot PSI levels and neglecting the supposedly more trustworthy 24 hour ones. Which means panic buying of N95 masks, people suddenly taking an interest in library books (to hide from the haze), conspiracy theories about cloud-seeding or hoaxers sending mass SMSes about fake holidays and office shutdowns. Oh wait, all that’s already happened, hourly PSI or not.