Hourly PM2.5 haze readings now graded to indicate pollution level

The National Environment Agency is phasing out 3-hour PSI updates following the enhancement of its hourly PM2.5 readings with banding to reflect current levels of haze pollution.

Unsure of what PM2.5 readings in haze updates actually mean? Don't worry, now you would be better informed by the government's system monitoring harmful fine particles during a haze.

The National Environment Agency (NEA) has enhanced its hourly PM2.5 readings with four bands to indicate the current level of pollution by fine particles to accompany the figures, the agency said in a statement today.

This would serve as a guide for people who need to adjust their plan for an immediate activity, it said.

The four ranges, which come with band numbers and descriptors, are:

I Normal - 0 to 55 ug/m3 or micrograms per cubic metre
II Elevated - 56 to 150 ug/m3
III High - 151 to 250 ug/m3
IV Very High - 251 ug/m3 and above

With the enhancements, the updates now serve as a clearer indicator of the prevailing air quality and as a result, the 3-hour Pollutant Standards Index (PSI) will be phased out, said the agency.

In Singapore, the main air pollutant during a haze situation is fine particulate matter (PM2.5).

NEA started publishing PM2.5 figures in 2014 as they are said to be a better indicator of air quality.

They are based on near real-time readings whereas the 24-hour PSI and 3-hour PSI that the agency has been providing are rolling averages of readings taken during longer periods.

But still, many people did not understand what the PM2.5 numbers meant and how they should respond to them when overwhelmed by haze created largely by forest and peatland fires in Indonesia. The readings just provided numbers, with no classification or explanation.

Now, the updates will also be accompanied by a general health guide which Government agencies have issued to the public during periods of haze. (See below).

There will be no health advisory based on the one-hour updates because the results of recent studies on shorter-period PM2.5 exposure could not provide conclusive evidence to justify any medical advisory, said NEA. Also, one-hour readings can be volatile, tending to fluctuate throughout the day.

So the agency does not advise specifically what people should do when the haze moves into the 'Elevated' band, for instance. But common sense would tell those at risk to start taking precautions and refer to the health guide if the level persists for hours or jumps to the 'High' band.

Read also: Scientists warn of health damage from Indonesia's haze fires

Use 24-hour PSI when making plans for the next day

With the enhancement of PM2.5 updates, the 3-hour PSI will no longer be relevant. It will be phased out by the end of the year.

The 24-hour PSI daily forecast will continue to play its more important role as it helps in the formulation of health advisories and enables government agencies to make major decisions, such as the cancellation of school classes or outdoor events.

This integrated index incorporates PM2.5 as well as other key pollutants of concern - sulphur dioxide (SO2), coarser particulate matter (PM10), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3).

The public is advised to use the 24-hour forecast when making plans for the next day, like going to school or work.

Each reading will continue to be accompanied by its respective health advisory for the various classifications of people - healthy persons, elderly, children and pregnant women.

For instance, people from all age and health groups can continue with normal activities when the PSI is rated 'Good' or 'Moderate'. (See below for the full guide)

The changes in NEA's haze readings will be reflected on its Haze microsite (https://www.haze.gov.sg) and myENV app. The round-the-clock PSI Forecast will be featured prominently to encourage more people to use it.

The dreaded haze period is nearly here

The start of the dry season in Indonesia usually spells the start of hazy conditions in the region.

The period from June to October every year has seen unmanageable forest and peatland fires allegedly connected with palm oil, pulp and paper industries.

Last year's haze saw a bigger crisis as the fires raged on with intensity and length, exacerbated by the El Nino weather phenomenon.

Enveloping Indonesia and its neighbours like Singapore and Malaysia, the haze caused deaths, widespread illnesses, flights to be grounded and schools to be closed.

In Singapore, the one-hour PM2.5 reading hit an alarming high of 471 micrograms per cubic metre last October.

However, experts believe that any impending haze hitting Singapore this year might not be as severe as last year because of the subsiding El Nino phenomenon, which was believed to have ended recently. Quickly taking over is another weather system, La Nina, which has drenched the region with heavy rains in recent weeks.

chenj@sph.com.sg

Read also:

Can South East Asia be haze-free by 2020?

Haze cost Singapore estimated $700 million last year: Minister Masagos

Efforts to stop Indonesian haze fires may not work for 2016

Last year's haze hit many parts of Singapore, including Sengkang housing estate.