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

SINGAPORE – Singapore continues to be shrouded in haze on Oct 17 with air quality in unhealthy levels for all regions for much of the day.

However, the 24-hour PSI crossed into the “very unhealthy” range in the west with a reading of 212 at 11pm.

The PSI readings in the rest of Singapore were 185 in the central region, 129 in the north, 166 in the south and 182 in the east.

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.

While most regions also saw “high” hourly PM2.5 readings for most of the afternoon, there was some respite in the evening.

The hourly PM2.5 readings had entered the “high” range in the west at 158 at 11am, and was later joined by the central and southern regions at noon.

The east entered the “high” range at 2pm, but air quality has since improved with the region returning to the “elevated” band at 7pm.

The PM2.5 level in the north improved briefly at 10pm, dropping to the “normal” range, before rising back to the “elevated” band an hour later.

At 11pm, all regions except the west (at 185) were in the elevated band: central (113), south (133), east (121) and north (65).

Hourly PM2.5 readings are measured in micrograms per cubic metre and used as a gauge for current air quality.

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 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.

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 17, the National Environment Agency (NEA) said the PSI forecast for Oct 18 could be between 150 and 220, putting it in the range of “unhealthy” to “very unhealthy”.

Some showers are expected over Singapore and the surrounding region on Oct 18.

“Winds are forecast to shift to blow from the south-south-east or south, which may reduce the transport of smoke haze from Kalimantan to Singapore. However, some smoke haze from Sumatra may drift towards Singapore,” the agency said.

More showers are also forecast over Singapore and parts of Kalimantan on Oct 19 and 20, 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.