Haze in Singapore: PSI dips amid light rain but PM2.5 concentration rises

People jogging in Bishan-Ang Mo Kio Park at about 5.30pm on Sept 15, 2019.
People jogging in Bishan-Ang Mo Kio Park at about 5.30pm on Sept 15, 2019.ST PHOTO: TIMOTHY DAVID
Haze is seen over Tiong Bahru at 2pm on Sept 15, 2019.
Haze is seen over Tiong Bahru at 2pm on Sept 15, 2019.ST PHOTO: NG SOR LUAN

SINGAPORE - The air quality improved slightly on Sunday afternoon (Sept 15) as Pollutant Standards Index (PSI) readings dipped amid light rain in several parts of the island.

At 5pm, the 24-hour PSI reading ranged between 100 in the central and 108 in the south of Singapore.

It dipped from the reading at 8am, which ranged between 107 in the east and 124 in the west.

The 24-hour PSI reading had crossed the unhealthy level at 1am in all parts of the island.

A PSI reading of 101 to 200 is in the unhealthy range, for which the National Environment Agency (NEA) advises the public to cut down on outdoor activities.

While the PSI reading improved, PM2.5 concentration readings, which the NEA says are a better indication of current air quality, has increased.

At 5pm, the one-hour PM2.5 reading ranged between 49 micrograms per cubic metre in the central part of the island and 63 in the western part of the island.

This is an increase from the range of 26 micrograms per cubic metre in the east and 37 in the central part of the island at 8am.

There are four bands on the PM2.5 concentration scale: 0 to 55 for normal, 56 to 150 for elevated, 151 to 250 for high, and very high for readings above 250.


The northern and southern parts of Singapore recorded one-hour PM2.5 readings that were in the elevated range at 4pm, at 56 and 67 respectively.

The NEA said the deteriorating air quality is due to winds blowing more smoke haze from Sumatra, which is south of Singapore.

More than 300,000ha of land in Indonesia have been ravaged by fire from January to last month.

For the next few days, dry weather can be expected in Singapore and over central and southern Sumatra, and the NEA warned that the PSI may enter the mid-section of the unhealthy range if denser haze is blown in.

The NEA will issue another haze advisory this evening.

As the PSI lifted, some people resumed their activities outdoors.

When The Straits Times visited Bishan-Ang Mo Kio Park at about 3.30pm, dog-walkers went on their way as per usual, and there were about seven dogs at the dog run area.

ST spotted several joggers, and a group of three domestic helpers who were having their fortnightly picnic, tucking into ice cream and longans.

A group of about 25 bird owners had gathered for a meet-up as well.

Ms Ng Hui Min, 24, a university student, attended the session with her sister and her yellow-naped Amazon parrot.

"The event went ahead because everything was already prepared, and the haze situation feels better today," said Ms Ng.