PSI in unhealthy range again after remaining in moderate range most evening

Air quality in Singapore hit unhealthy levels again on Saturday night. This file photo was taken on Oct 8, 2014. -- ST FILE PHOTO: MARK CHEONG
Air quality in Singapore hit unhealthy levels again on Saturday night. This file photo was taken on Oct 8, 2014. -- ST FILE PHOTO: MARK CHEONG

SINGAPORE - Air quality in Singapore hit unhealthy levels again on Saturday night, with the three-hour Pollutant Standards Index (PSI) inching up to 102 at 11pm from 99 at 10pm. It was in the moderate range for most of the evening.

In the afternoon, the three-hour PSI, a measure of air quality here, reached 101 at 1pm, and had gone up to 106 by 2pm. At 6pm, however, the reading dipped to a moderate level of 89.

Air quality is considered unhealthy when PSI readings range from 101 to 200, and prolonged strenuous outdoor physical exertion should be reduced or avoided.

The National Environment Agency (NEA) said in an update on Saturday that it has been "slightly hazy" in Singapore since morning, with elevated levels of air pollutant PM2.5 (fine particulate matter less than 2.5 microns in size) in most parts of the island during the late afternoon.

It attributed the conditions to smoke haze in the surrounding region blown in by prevailing southerly to southeasterly winds. In its daily haze advisory on Friday, the agency said that eight and 48 hotspots were detected in Sumatra and Kalimantan respectively, where widespread smoke haze was visible.

Hazy conditions are forecasted to continue for the rest of the day, with overall air quality hovering in the high end of the moderate range. Thundery showers and "occasional slight haze" are expected over Singapore tomorrow, added the NEA.

yeosamjo@sph.com.sg