Singapore Haze Caused by Local Sources

The haze that hung over Singapore from Thursday night till Friday morning was probably caused by local pollution instead of forest fires in the region, experts say.

“Based on the latest satellite images, there were no significant hotspots or smoke haze detected in the nearby region,” said a spokesman for the National Environment Agency. “The haziness was due to the accumulation of particulate matter under light wind conditions,” he added.

The 24-hour Pollutant Standards Index, a measure of air quality here, reached a high of 95 in southern Singapore at 8am yesterday.

A PSI reading above 100 indicates unhealthy air quality, while a reading of between 51 and 100 is considered moderate.

The 24-hour PSI across Singapore stayed in this range for the rest of the day, although readings in southern Singapore leaned towards the higher end.

Experts told The Straits Times there were a negligible number of hotspots in Riau, Sumatra and Kalimantan—provinces in Indonesia whose fires are usually caused by smoke haze.

“This makes Indonesia unlikely to be the source of the bad air,” noted Zhang Wen, executive director of volunteer group People’s Movement to Stop Haze, which monitors haze conditions here. “Another significant source of our poor air is exhaust from traffic.”

The hourly concentration readings for PM2.5—tiny pollutant particles associated with haze—also started inching up from Thursday evening, although their levels across Singapore returned to normal by 9 a.m. Friday.

Air quality scientist Erik Velasco noted that hourly concentrations of nitrogen dioxide, a pollutant associated with the combustion of fossil fuels, also started going up around the same time as PM2.5 concentration levels.

Assistant Professor Winston Chow, from the National University of Singapore’s geography department, said Friday’s rain was common for this time of the year, as Singapore goes through the inter-monsoon season.

Singapore experiences most of its thunderstorms during this period.

NEA said thundery showers can be expected over the next few days.