Haze in Singapore: PSI reading in central region in ‘very unhealthy’ range

SINGAPORE – The hazy conditions persisted overnight with the central part of Singapore worst hit as the PSI reading there entered the “very unhealthy” range at midnight, while the hourly PM2.5 readings fluctuated between the “elevated” and “high” bands islandwide.

At 6am on Oct 16, the 24-hour Pollutant Standards Index (PSI) in the central region stood at 221, hitting a new high for this haze season. The rest of the island recorded PSI readings in the unhealthy band at that time: west (193), east (192), south (178) and north (145).

Air quality is considered unhealthy when the PSI – a 24-hour rolling average of six key air pollutants – is in the range of 101 to 200 and very unhealthy when it is in the range of 201 to 300.

The hourly PM2.5 readings – measured in micrograms per cubic metre and used as a gauge for current air quality – were hovering between the “elevated” and “high” bands across the island at 6am: east (160), central (150), west (148), south 113) and north (99).

PM2.5 scores from 0 to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles, while readings between 151 and 250 are considered high and scores above 251 are classified as very high.

The highest PM2.5 reading this haze season was recorded at 3pm on Oct 14 in the western part of the island at 288.

In its daily haze advisory on the evening of Oct 15, the National Environment Agency (NEA) said dense smoke haze from fires in Kalimantan continued to drift towards Singapore under prevailing southeasterly winds. Smoke haze was also observed over Sumatra.

NEA said some showers are expected over Singapore and the surrounding region on Oct 16, but southern Sumatra and parts of Kalimantan are likely to remain dry. With the winds forecast to be east-south-easterly or south-easterly, smoke haze is likely to continue to be carried from Kalimantan towards Singapore, it added.

Over the weekend, more showers are forecast over Singapore and parts of Kalimantan. Winds are expected to shift to blow from the south-east or south, which could reduce the transport of smoke haze from Kalimantan to Singapore. Some smoke haze from Sumatra may however still drift towards Singapore, NEA said.