Haze in Singapore: PM2.5 readings return to normal but PSI still in unhealthy range in most regions

SINGAPORE – The air quality in Singapore improved in the morning of Oct 25, with the hourly PM2.5 readings returning to “normal” for three regions, even as the 24-hour PSI levels remained in the “unhealthy” band across the island.

At 7am, the PM2.5 readings were in the “normal” range in the north (55), south (44) and central (54), while the eastern and western regions remained in the “elevated” band at 61 and 62, respectively.

PM2.5 readings are gauged hourly and reflect the current air quality. Scores from zero to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles.

Meanwhile, the 24-hour Pollutant Standards Index (PSI) stood in the unhealthy range across the island: 111 in the west, 104 in the south, 112 in the east, 140 in the west and 115 in the central.

Air quality is considered good to moderate when the PSI – a 24-hour rolling average of six key air pollutants – is in the range of 0 to 100, and unhealthy when it is in the range of 101 to 200.

When air quality breaches the “unhealthy” threshold, people, especially the elderly, children and those with health issues, should start scaling down outdoor activities.

Air quality in Singapore saw a brief respite early on Oct 23, when PSI readings were in the good to moderate range and PM2.5 levels were in the normal range. However, it started to deteriorate early on Oct 24.

Forecast for Oct 25

In its daily advisory on the evening of Oct 24, the National Environment Agency (NEA) said moderate to unhealthy air quality is expected on Oct 25, with the PSI forecast to be in the range of 80 to 130.

Smoke haze from Sumatra was seen drifting towards Singapore and was also observed over Kalimantan on Oct 24, NEA said.

On Oct 25, winds are expected to blow from the south-west or west, which could limit transport of smoke haze to Singapore. Showers are expected over Singapore and the surrounding region which may help with the haze conditions, added NEA.

Winds are expected to continue blowing from the south-west or west on Oct 26 and 27, and with showers expected over Singapore and the vicinity, the haze situation is “likely to improve”, added the agency.