SINGAPORE: Air quality in Singapore worsened on Tuesday (Sep 17), hitting unhealthy levels after a day of improved readings.
At 8pm, the 24-hour PSI stood at 103 in the west, 100 in the south, 92 in the east, 90 in the north and 90 in the central region.
According to the National Environment Agency (NEA), PSI readings of 50 and below denote “good” air quality, “moderate” for 51-100 and “unhealthy” for 101-200.
The one-hour PM2.5 concentration reading ranged from 51-73 µg/m3 at 8pm, within the normal to elevated range.
PM2.5 is a measure of tiny particles less than 2.5 micrometres in diameter in the air. When the PM2.5 reading is in the elevated range, haze particles can affect the heart and lungs, especially in people who have chronic heart or lung conditions.
PSI readings could go up in the next 24 hours, NEA said in a media advisory on Tuesday afternoon.
The agency added that the 24-hour PSI readings may enter the mid-section of the unhealthy range if denser haze from Sumatra is blown in.
"Given the air quality forecast for the next 24 hours, healthy persons should reduce prolonged or strenuous outdoor physical exertion," said NEA.
"The elderly, pregnant women and children should minimise prolonged or strenuous outdoor physical exertion, while those with chronic lung or heart disease should avoid prolonged or strenuous outdoor physical exertion."
Last Saturday, the PSI reading reached the unhealthy level for the first time since August 2016 as it surpassed the 100 mark.
"INCREASED HAZINESS" OVER SOUTHERN SUMATRA
The deterioration in air quality since late Tuesday morning was due to "increased haziness" over southern Sumatra which has been blown in by the prevailing winds, said NEA.
A total of 109 hotspots were detected in Sumatra, down from 233 on Monday, but this was due to a "partial satellite pass". This is when a satellite's field of view covers only part of a region of interest as the satellite orbits the earth.
There is still moderate to dense smoke haze in Indonesia's central and southern provinces of Riau, Jambi, South Sumatra and Lampung, said NEA.
Earlier on Tuesday, the environment agency said authorities have put in place "robust action plans" to minimise and manage the impact of haze on the public.
These include making sure that there are enough N95 masks, and for hospitals to be ready for any increase in haze-related cases.