SINGAPORE: All areas of Singapore had unhealthy levels of pollutants in the air early on Tuesday (Sept 15) in a first for the country since September 2019.
At 6am, the 24-hour Pollutant Standards Index (PSI) readings for the north (104), south (111), east (128), west (128) and central (154) regions were all in the unhealthy range.
The readings dipped slightly but remained within the unhealthy range at 9am, at 103 in the north, 106 in the south, 122 in the east, 124 in the west and 148 in the central region.
Air quality is considered unhealthy when the 24-hour PSI is in the range of 101 to 200, during which the National Environment Agency (NEA) advises the public to reduce outdoor activities.
The air quality in Singapore had worsened on Sept 14 with the PSI across the island, except for the north, hitting unhealthy levels, following several days in the moderate range.
The PSI reading for the north crossed the 101 threshold – when air quality is deemed unhealthy – at about 1am on Sept 15, rising to 102 from 99 at midnight.
PSI readings of 51 to 100 are considered moderate, while values of 0 to 50 are in the “good” range.
The one-hour PM2.5 readings across the island on Sept 15 largely fell to normal levels, ranging from 32 to 44 micrograms (mcg) per cubic m, as at 6am.
The exceptions were the central (66) and west (59) regions, where the PM2.5 readings remained in the elevated range.
As at 9am, all PM2.5 readings across the island were back to normal levels, ranging from 28 to 36 mcg per cubic m.
Readings of 56mcg per cubic m to 150mcg per cubic m are considered elevated, while levels of 151mcg to 250mcg per cubic m are in the “high” range. Anything 55 and below is considered normal.
In an advisory at about 6.30pm on Sept 14, NEA said air quality in Singapore for the next 24 hours is forecast to be in the high moderate to mid-unhealthy range.
The PSI crossed into the unhealthy range two weeks ago, hitting 101 in central Singapore on the morning of Sept 4. In the days that followed, readings in the central, eastern and western parts of Singapore occasionally crossed into the unhealthy range.
September’s developments mark the first time since October 2023 that the PSI in Singapore hit unhealthy levels because of haze, with the authorities earlier warning of the risk of haze between June and October as a result of warmer and drier conditions brought on by both El Nino and the Indian Ocean Dipole.
In its Sept 14 advisory, NEA added that moderate to dense smoke plumes, some of which were noticed to be drifting towards Singapore, continue to be observed from forest fires in Kalimantan.
Smoke plumes were also observed in southern Sumatra.
Dry conditions are forecast over Singapore and the surrounding region in the coming days, NEA added.
“With the prevailing winds forecast to continue blowing from the south-east to east-southeast, Singapore will likely be affected by smoke haze,” the agency said. - The Straits Times/ANN
