Slight haze on Monday as PSI inches towards unhealthy range with more hot spots in Sumatra

SINGAPORE - There was a slight haze in some parts of Singapore on Monday afternoon (Sept 9), likely due to an increase in hot spot activity in Sumatra, the National Environment Agency (NEA) said in a statement.

The 24-hour Pollutant Standards Index (PSI) ranged from 75 to 85, in the moderate range, at 6pm.

The unhealthy PSI range, for which NEA advises the public to cut down on time spent outdoors, is from 101 to 200.

Meanwhile, the PM2.5 level at 6pm on Monday was in the 41 to 59 range, which is in the normal to elevated bands.

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NEA said PM2.5 concentration readings are a good indicator of current air quality, and those concerned should use them to decide whether to go for immediate outdoor activities, such as a jog.

PM2.5 readings measure the concentration of tiny particles less than 2.5 micrometres in diameter - or about one-thirtieth the diameter of a human hair - 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 diseases like asthma or heart failure.

People with chronic heart and lung conditions should ensure that their medication is on hand and readily available, according to NEA's website.

Singapore and Malaysia have been plagued for decades by periodic haze caused by clouds of ash from the fires in neighbouring Indonesia.

The hazy conditions on Monday afternoon come amid an increase in the number of hot spots in central and southern Sumatra.

A total of 380 hot spots were detected in Sumatra, up from 333 on Sunday, said NEA.

This is also more than triple the 113 hot spots detected last Saturday.

"There were persistent hot spots with moderate to dense smoke haze in Riau and Jambi provinces, and some of the haze has spread across the Strait of Malacca to western parts of Peninsular Malaysia," NEA said in its statement. Hot spots with smoke haze were also detected in South Sumatra and Lampung.

Dry weather is expected to continue in Sumatra for the next few days, while the prevailing winds are forecast to keep blowing from the south-east or south.

For the next 24 hours, the one-hour PM2.5 concentration readings are expected to remain in the range between the normal and elevated bands.

The 24-hour PSI is forecast to be in the moderate range.

"Given the air quality forecast for the next 24 hours, everyone can continue with normal activities. Persons who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention," said NEA.

Regular updates on the haze situation can be found on NEA's website at

This article was first published in The Straits Times. Permission required for reproduction.