Haze in Singapore: PSI in central region back in the unhealthy range
Sign up now: Get ST's newsletters delivered to your inbox
Hazy conditions seen from the Orchard Road area on Sept 18 at 5.10pm.
ST PHOTO: KELVIN CHNG
SINGAPORE – The air quality in Singapore deteriorated on Sept 19, with the 24-hour Pollutant Standards Index (PSI) in the central region crossing into the unhealthy region again.
The 24-hour PSI reading in the area was 109 at 7pm, with the western (95) and eastern (94) regions inching towards the unhealthy range.
Air quality is considered unhealthy when the 24-hour PSI is in the range of 101 to 200, during which the National Environment Agency (NEA) advises the public to reduce outdoor activities. PSI readings of 51 to 100 are considered moderate, while values of zero to 50 are in the “good” range.
The readings in other areas of Singapore have been increasing steadily but remain in the moderate range.
In its daily haze advisory on Sept 19, the NEA said the 24-hour PSI forecast is set to be within the “high moderate to mid unhealthy” range, even following afternoon showers over the central and western parts of Singapore.
The hourly PM2.5 readings, which indicate the current concentrations of fine particulate matter, fell in the evening from a daily high of 149 at noon to 81 in the central region at 7pm.
PM2.5 readings are considered elevated if they fall between 56 and 150, and high if they are between 151 and 250.
The NEA has advised the public to refer to the hourly PM2.5 reading if they are considering immediate activities and the 24-hour PSI readings to plan for the day ahead.
The central region includes the Thomson, Marymount, Sin Ming, Ang Mo Kio, Bishan, Serangoon Garden, MacRitchie and Toa Payoh areas, according to the NEA website.
In its Sept 19 advisory, the NEA said smoke plumes from forest fires in Kalimantan and southern Sumatra were observed to be drifting towards Singapore.
Dry conditions are forecast to continue over parts of southern Sumatra and Kalimantan and smoke haze might affect Singapore as the prevailing winds are expected to blow from the east-south-east or south-east.
The PSI crossed into the unhealthy range two weeks ago, hitting 101 in central Singapore on the morning of Sept 4. In the days that followed, readings in the central, eastern and western parts of Singapore occasionally crossed into the unhealthy range.
September’s developments mark 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.