SINGAPORE; Hazy conditions persisted into the afternoon of Oct 17, even as the 24-hour Pollutant Standards Index (PSI) in central Singapore dipped back into the “unhealthy” band after remaining in the “very unhealthy” range the previous day.
At 2pm, the 24-hour PSI was in the “unhealthy” range in all regions: central (184), north (135), south (154), east (173) and west (185).
Meanwhile, hourly PM2.5 readings entered the “high” range in the west at 158 at 11am, followed by the central and southern regions at noon and the east at 2pm.
At 2pm, hourly PM2.5 readings stood at 243 in the west, 179 in the central region, 162 in the south and 159 in the east. The figure remained in the “elevated” range in the north at 91.
Air quality is considered “unhealthy” when the PSI – a 24-hour rolling average of six key air pollutants – is between 101 and 200, and “very unhealthy” when it is between 201 and 300.
Hourly PM2.5 readings are measured in micrograms per cubic metre and used as an indicator of current air quality.
PM2.5 scores from 0 to 55 represent normal values, while readings between 56 and 150 indicate an elevated concentration of fine particles. Readings between 151 and 250 are considered high, while scores above 251 are classified as very high.
The central region was worst hit on Oct 16, when the 24-hour PSI remained in the “very unhealthy” range throughout the day, peaking at a seasonal high of 229 between 3pm and 4pm and remaining at that level until the early hours of Oct 17.
The highest PM2.5 reading of the haze season was recorded in the western part of the island at 3pm on Oct 14, at 288.
Singapore is experiencing its 13th consecutive day of unhealthy air quality since Oct 5 – the longest continuous stretch of poor air quality the country has endured since the 2015 haze crisis. That year, poor air quality 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 range from 150 to 230, putting air quality in the “unhealthy” to “very unhealthy” categories.
Showers are expected over Singapore and the surrounding region, including 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.
Showers are also forecast over Singapore and parts of Kalimantan on Oct 18 and 19, it added.
The agency said winds were expected to gradually weaken and blow from the south-east or south, which could further reduce the movement of smoke haze from Kalimantan to Singapore.
