SINGAPORE - The air quality in Singapore remained unhealthy on Monday (Sept 23) but the showers expected in the day and the coming week could bring some relief from the haze.

The National Environment Agency (NEA) said in its daily advisory on Sunday that with winds forecast to blow from the east-northeast or east-southeast on Monday, “the shift in winds is expected to bring some showers over the region”.

“For the next few days, an increase in rain showers can be expected over the region, including Sumatra and Kalimantan,” said the NEA. “The showers may help to improve the hot spot and haze situation in Sumatra and Kalimantan.”

At 8pm on Monday, the 24-hour Pollutant Standards Index (PSI) reading across Singapore was 92-107, between the moderate and unhealthy bands.

The 1-hour PM2.5 concentration, which the NEA said is a better indicator of current air quality, was 39-57 micrograms per cubic m, in the normal and elevated bands.

The 24-hour PSI is forecast to be between the high end of the moderate range and the low end of the unhealthy range on Monday.

A PSI reading of zero to 50 indicates good air quality while a reading of 51 to 100 is in the moderate range. A reading of 101 to 200 is considered unhealthy. Air quality is considered “very unhealthy” when the PSI ranges from 201 to 300, and “hazardous” when the reading is more than 300.

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 any higher readings.

On Sunday, 246 hot spots were detected in Sumatra in Indonesia, and 474 hot spots in Kalimantan, which also affected parts of Peninsular Malaysia.

The NEA said the “slight deterioration” in the air quality on Sunday was due to smoke haze being blown in from Kalimantan by the prevailing winds.

It advised healthy people to reduce prolonged strenuous exertion outdoors on Monday, and elderly people, pregnant women and children to minimise it, while people with chronic heart or lung disease should avoid it altogether.

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Stay-at-home mother Michelle d’Cruz, 48, said on Sunday that she and her two children, aged 10 and 13, were more concerned about the haze than her husband, a 47-year-old engineer.

She said: “The kids and I stayed in because the haze is a put-off and we didn’t want to risk getting sick with exams around the corner. My husband, on the other hand, went to the F1 (Formula One Singapore Grand Prix), regardless.”

With additional reporting by Goh Yan Han