Air quality improves to good to moderate range across Singapore after 18 days of unhealthy air

SINGAPORE – The air quality in Singapore is back in the “good to moderate” range, after 18 days of bad air.

At 3pm on Oct 22, the 24-hour Pollutant Standards Index (PSI) had improved in all regions across the island, with readings ranging from 71 to 99.

Readings in this band denote good to moderate air quality, and normal activities can be carried out.

The west was the last region to exit the unhealthy zone, dropping from 101 to 99 at 3pm.

Singapore had since Oct 5 been experiencing unhealthy air quality, denoted by 24-hour PSI readings above 101.

When air quality breaches this threshold, people should start scaling down their outdoor activities.
The 24-hour PSI reflects air quality in Singapore over the past day.

The PSI tracks the levels of six pollutants, although the dominant toxin during periods of transboundary haze is small particulate matter known as PM2.5.

Meanwhile, the one-hour PM2.5 readings, which are measured in micrograms per cubic m and are a gauge of the current air quality, have remained in the “normal” range islandwide since 1am.

At 3pm, their values were between 16 and 39. 

Scores from zero to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles, readings between 151 and 250 are considered high, and scores above 251 are classified as very high.

However, satellite maps on the National Environment Agency’s (NEA) website showed the persistence of hotspots in Indonesia – indicating that the haze crisis is not yet over.

Prevailing winds have kept the smoke plumes away for Singapore for now, with denser clouds of pollution observed in areas such as Peninsular Malaysia, Kalimantan, Sumatra, and the western parts of Sarawak.

Dilenjit Singh is a correspondent at The Straits Times’ breaking news desk.