SINGAPORE — Air quality in Singapore hit unhealthy levels on Saturday (Sept 14) as the Pollutant Standards Index (PSI) went beyond the 100 mark at 4pm. This is the first time since August 2016 that the 24-hour PSI reading has reached the unhealthy level.

As of 4pm, the 24-hour PSI reading in the western part of Singapore was 103. It was 97 in the south, 89 in the north, 88 in the central region and 86 in the east. 

At 5pm, the figures inched up to 106 for the western region, 98 for the south, 90 in the north, 89 in the central region and 87 in the east.

According to the National Environment Agency (NEA), PSI readings of 50 and below denote “good” air quality, “moderate” is 51-100 and “unhealthy” is 101-200.

When air quality is at the unhealthy range, people — especially children, the elderly, pregnant women and those with heart or lung conditions — should reduce prolonged or strenuous outdoor activities. Those who are not feeling well should seek medical attention, NEA said.

The one-hour PM2.5 concentration readings ranged from 90-158µg/m3 at 4pm, with the west seeing the highest levels of 158µg/m3 in Band III (High). This eased slightly an hour later, with the 5pm readings ranging from 77-133µg/m3. The highest levels of 133µg/m3 in Band II (Elevated) was recorded in the west.

PM2.5 is a measure of tiny particles less than 2.5 micrometres in diameter in the air. When the PM2.5 reading is in the elevated range, haze particles can affect the heart and lungs, especially in people who have chronic heart or lung conditions. Those with such conditions should ensure that they have their medication on hand, NEA said.

According to NEA, one-hour PM2.5 readings are a "good indicator of current air quality", and can be used for those deciding whether to go for immediate outdoor activities, such as a jog.

NEA said on Friday that 156 hotspots were detected in Sumatra, mostly in the central and southern parts of the island. 

"Moderate to dense smoke haze continued to emanate from persistent hotspots there, and hazy conditions persisted in Singapore and some parts of Peninsular Malaysia," it said.

In Kalimantan, 1,043 hotspots were detected on Friday, with "widespread smoke haze" seen in many areas, and some haze blown by prevailing winds to western Sarawak and surrounding sea areas.

The environment agency said there may be brief showers in Singapore over the next few days but the weather in Sumatra and Kalimantan is expected to remain generally dry.

"With the prevailing winds blowing from the south or southwest, this may bring increased haziness to Singapore," it said. 

Forest fires have raged through parts of Sumatra and Kalimantan in recent weeks, prompting the Indonesian government to send in military and police to douse the flames.

In Malaysia, air quality dropped to "unhealthy" levels in and around Kuala Lumpur, according to the government's air pollutant index, and the skyline has been shrouded in thick smog.

The last time the PSI breached the 100 mark in Singapore was on Aug 29, 2016, when the 24-hour reading hit 109 in the north. 

The worst haze episode in Singapore in recent years was in 2015, when rampant forest fires in Indonesia choked the region in haze for weeks. PSI readings in Singapore climbed above the hazardous level of 300, forcing schools to close. CNA

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