SINGAPORE – More showers are expected here and in the region over the next few days, with the likelihood of the haze affecting the Republic remaining low, the National Environment Agency (NEA) said on Wednesday (Oct 2).

This is even as the number of hot spots detected in Sumatra fell sharply.

For the next 24 hours, NEA said the 24-hour Pollutant Standards Index (PSI) readings are forecast to be in the moderate range, while the one-hour PM2.5 concentration readings, which the agency has said is a better measure of current air quality, should stay in the normal band.

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, very unhealthy from 201 to 300, and hazardous when the reading is more than 300.

The PM2.5 concentration scale has four bands: 0 to 55 for normal, 56 to 150 for elevated, 151 to 250 for high, and very high for any higher readings.

At 6pm on Wednesday, 24-hour PSI readings were 58-64, in the moderate range. The PM2.5 concentration readings were 6-18 micrograms per cubic m, in the normal band.

NEA said that there was a sharp drop in the number of hot spots detected in Sumatra on Wednesday as there were showers over the area, falling from 563 on Tuesday to 74 on Wednesday. Most of these were in the southern provinces of Jambi, South Sumatra and Lampung.

The environment agency has said that the health impact of the haze is dependent on one’s health status, the PSI level and the length and intensity of outdoor activity.

Doctors The Straits Times has spoken to have warned that vulnerable groups, such as patients with pre-existing medical conditions, could experience increased discomfort on poor air quality days.