Haze in Singapore: Air quality may worsen, with PSI forecast to be entirely in unhealthy range

SINGAPORE – The haze situation here may worsen on Oct 8, with the National Environment Agency (NEA) forecasting the 24-hour Pollutant Standards Index (PSI) readings for the day to be in the unhealthy range.

It is the first time since the agency started issuing daily haze advisories on Sept 4 that the forecast has fallen completely within the unhealthy band of 101 and 200. Previous forecasts in the same period were in the moderate, or moderate to unhealthy ranges.

In its daily advisory, sent at about 6.20pm on Oct 7, NEA said that dry weather is expected to continue over central and southern parts of Sumatra in Indonesia, as well as many parts of Kalimantan.

“Under the prevailing southeasterly to southerly winds, smoke haze from these areas may continue to drift towards Singapore,” the agency said.

When the 24-hour PSI readings are in the unhealthy band, those who are healthy should reduce prolonged or strenuous outdoor physical activities, according to the haze advisory.

Vulnerable people – including the elderly, pregnant women, children and those with chronic lung or heart disease – should minimise or avoid such activities entirely.

As at 7pm on Oct 7, all five regions here registered PSI readings in the unhealthy range, with measurements of 106 in the north, 113 in the south, 130 in the east, 143 in the west and 136 in the central region.

The readings all across Singapore have remained in the unhealthy range since noon on Oct 7, matching NEA’s daily forecast on Oct 6 that readings for Oct 7 would range from high-moderate to mid-unhealthy.

The PSI is a 24-hour rolling average of six key air pollutants and guides people when planning outdoor activities for the following day.

Meanwhile, the 1-hr PM2.5 reading – which points to the current air quality and is used as a gauge for immediate activities – was in the elevated band for most of Oct 7.

It briefly crossed into the high band at 4pm in the western part of Singapore with a 152 reading, before falling back into the elevated band at 5pm.

An hourly PM2.5 reading between 151 and 250 indicates a high concentration of fine particles, while a reading between 56 and 150 signals an elevated level.

A September study led by local researchers showed that even small spikes in PM2.5 levels are linked to an increase in emergency department visits for asthma and chronic respiratory disease.

These developments over the past month marked 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.