Singapore haze: PSI ‘very unhealthy’ in west, PM2.5 in ‘elevated’ band in most regions

SINGAPORE - The hazy conditions continued in the morning of Oct 17 even as the 24-hour PSI in central Singapore dipped back to the “unhealthy” band after staying in the “very unhealthy” range the day before.

At 7am, the 24-hour PSI was in the “unhealthy” range in all regions: central (191), north (144), south (161), east (175), west (181).

The central region was worst hit on Oct 16 when the 24-hour PSI there registered “very unhealthy” readings throughout the day, peaking at a season high of 229 from 3pm to 4pm, till the early hours of Oct 17.

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.

Meanwhile, the hourly PM2.5 readings – measured in micrograms per cubic metre and used as a gauge for current air quality – remained in the “elevated” range across all regions at 7am: central (108), north (83), south (75), east (119), west (97).

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.

Singapore is in its 13th consecutive day of unhealthy air since Oct 5 – the longest continuous stretch of poor air quality the country has endured since the 2015 haze crisis. That year, bad air lasted 14 days from Sept 23 to Oct 7.

In its daily haze advisory on the evening of Oct 16, the National Environment Agency (NEA) said the PSI forecast for Oct 17 could be between 150 and 230, putting it in the range of “unhealthy” to “very unhealthy”.

Some showers are expected over Singapore and the surrounding region, including over parts of Kalimantan, on Oct 17.

“With the winds forecast to shift to blow from the south-east or south-south-east, the transport of smoke haze from Kalimantan to Singapore may be reduced. However, some smoke haze from Sumatra may drift towards Singapore,” the agency said.

Similarly, showers are also forecast over Singapore and parts of Kalimantan on Oct 18 and 19, it added.

It said that the winds are expected to gradually weaken and blow from the south-east or south, which could further decrease the movement of smoke haze from Kalimantan to Singapore.