Air quality in all Singapore regions in unhealthy range
The 24-hour PSI was last in the unhealthy range across all regions on Sep 15.
A view of the haze from Bishan Towers on the morning of Sep 29, 2026. (Photo: CNA/Marcus Mark Ramos)
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SINGAPORE: Air quality in the central, southern, western and eastern parts of Singapore remained in the unhealthy range on Tuesday (Sep 29) morning, with the northern region crossing the threshold at 7am.
The 24-hour Pollutant Standards Index (PSI) in the northern region hit 101 at 7am, while the central region's reading was the highest at 155.
The hourly PM2.5 reading, which reflects air quality at a single point in time, was in the elevated band across all regions as of 9am, ranging from 61 to 112.
The 24-hour PSI readings for the central and southern regions first hit 104 and 103, respectively, at 8pm on Monday.
The air quality in the western region entered the unhealthy range at 9pm, with a PSI reading of 101.
Air quality in the eastern region subsequently dipped into the unhealthy band at midnight on Tuesday.
PSI readings have dipped in and out of the band over the past weeks. The last time the air quality in all five regions was in the unhealthy range was on Sep 15.
In its media advisory on Monday evening, the National Environment Agency (NEA) said that the 24-hour PSI was forecast to be in the high moderate to mid-unhealthy range for the next 24 hours.
On Tuesday morning, NEA said that dry weather prevailed over most parts of the southern ASEAN region overnight, except over the northern parts of Sumatra where showers were observed.
It said that scattered hotspots were detected in Kalimantan and Sumatra. A few hotspots were also detected elsewhere in the southern ASEAN region.
"Moderate transboundary smoke haze was observed to cover parts of Peninsular Malaysia, Singapore and the northwestern parts of Borneo," said NEA, adding that moderate to dense smoke plumes were also observed to emanate from hotspots clusters detected in large parts of Kalimantan, as well as the central and southern parts of Sumatra.
"Many air quality stations in Borneo, Sumatra, Singapore and some parts of Peninsular Malaysia are reporting unhealthy to hazardous levels," it said.
"The full extent of the hotspot and smoke haze situation in the region could not be determined due to cloud cover," NEA added.
Still, it noted that showers prevailed over the northern ASEAN region overnight, except over the central and eastern parts of the Mekong sub-region where it was relatively drier.
The hotspot and smoke haze situation in the region remained subdued, it said.
The agency said that dry conditions are expected over most parts of the southern ASEAN region in the coming days, with the exception of Peninsular Malaysia, the northern and central parts of Sumatra, as well as parts of Borneo where showers are forecast.
"The hotspot and smoke haze situation may improve in areas experiencing showers but also continue to stay elevated in areas experiencing prolonged periods of dry weather, with a risk of transboundary haze occurrence," it said.
Wet weather is also expected to persist over the northern ASEAN region, which helps to keep the hotspot and smoke haze situation subdued, it noted.
"The northern ASEAN region is expected to remain wet, which should keep the hotspot activity low," said NEA.
The 24-hour PSI is Singapore's indicator of daily air quality and forms the basis of NEA's daily health advisories. It is calculated using six air pollutants - PM2.5, PM10, ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide - and reflects the average air quality of the past 24 hours.
The 1-hour PM2.5 reading, on the other hand, is the hourly average of the PM2.5 pollutant levels. PM2.5 is fine particulate matter with a diameter of 2.5 micrometres or shorter, and is the dominant pollutant during haze that causes harm to health.
A 24-hour PSI reading is considered "unhealthy" when it is in the 101 to 200 range, "very unhealthy" when it is within the 201-300 range, and "hazardous" when it goes over 300.
The hourly PM2.5 reading is classified in four bands: normal, elevated, high and very high. It is considered elevated when it ranges from 56 to 150. The "high" band ranges from 151 to 250, and readings above that are classified as "very high".
