Haze in Singapore: PM2.5 readings return to normal but PSI still in unhealthy range in most regions
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Hazy conditions seen at the Merlion Park at 1.40pm on Oct 24.
ST PHOTO: BRIAN TEO
SINGAPORE – The hourly PM2.5 readings returned to normal across all five regions in Singapore on the morning of Oct 25, even as the 24-hour PSI levels remain in the “unhealthy” range for three regions.
At 1pm, the PM2.5 readings ranged between 30 and 52, within the “normal” band.
PM2.5 readings are gauged hourly and reflect the current air quality. Scores from zero to 55 represent normal values, and those between 56 and 150 indicate an elevated concentration of fine particles.
Hourly PM2.5 readings across the island had stayed in the elevated range since the evening of Oct 24 and into the early hours of Oct 25.
Meanwhile, the 24-hour Pollutant Standards Index (PSI) stood in the “unhealthy” range for the east (106), west (124) and the central region (104), while the north (99) and south (97) registered “good to moderate” air quality.
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 zero 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, conditions started to deteriorate 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 the drifting 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.