SINGAPORE - The National Environment Agency (NEA) has written to Indonesia with its concerns over the haze as air quality in Singapore is forecast to remain in the unhealthy range.
The 24-hour Pollutant Standards Index (PSI) reading crossed into the unhealthy range at 4pm on Friday (Aug 26), and is expected to remain unhealthy for the next 24 hours.
"The prevailing winds are forecast to blow mainly from the west... There could be a further deterioration in the air quality in the night should the westerly winds blow in denser haze from Sumatra," said NEA.
The CEO of the NEA wrote to his Indonesian counterpart on Friday to register Singapore's concerns over the haze, the agency said.
NEA said it "urged Indonesia to continue taking the necessary actions to prevent and mitigate the fires during this dry season". It has also asked for an update on the situation in Sumatra and Kalimantan.
As at 2am, the 24-hour Pollutant Standards Index (PSI) was 91-139, according to the NEA website. Readings in the west and north are in the unhealthy range at 139 and 134 respectively. It was 104 in the south, 108 in the central regions and 91 in the east.
The 3-hour PSI - an indicative reading not tied to a health advisory - was 59.
The 1-hour PM2.5 reading has fallen to 9 in the central region in Singapore at 4am, followed by 4 in the east, 29 in the north, 4 in the south and 51 in the west.
The 1-hr PM2.5 concentration over the next 24 hours is expected to fluctuate between Band II (Elevated, 56 - 150) and Band III (High, 151 - 250), said NEA.
In July, NEA introduced new bandings and descriptors for the one-hour concentration readings of fine particles called PM2.5 - a major pollutant in smoke haze.
They are a good indicator of the current air quality and members of the public can "use this for immediate activities like going for a jog", said NEA.
The Straits Times understands that they were introduced after members of the public suggested having a guide to PM2.5 readings after last year's haze episode.
However, the bands do not state what levels are healthy or not, unlike the 24-hour PSI, which is used by the authorities here as the reference for health advisories.
The hazy conditions in Singapore have persisted, as haze from central Sumatra continued to be blown in by the prevailing westerly winds, the agency added.
"The main cause of the haze and smell that Singapore is experiencing today is likely from the forest and peatland fires from land clearing practices in Sumatra," said Assistant Professor Janice Lee from the Asian School of the Environment at Nanyang Technological University (NTU).
Ms Lee said the chances of the haze continuing into September are high, as it is the peak dry season where there is frequent land clearing activities using fires. Dry weather conditions in Sumatra also means that Singapore can expect smoke from fires due to the South-Westerly winds in the region.
"The wetter conditions from La Niña are expected to help douse the fires but international climate models do not indicate that these conditions have kicked in yet. Presently, dry weather conditions prevail in Sumatra and Kalimantan and we can expect smoke from fires due to the South-Westerly winds in the region," she added.
Given the air quality forecast, NEA advises the public to reduce prolonged or strenuous outdoor physical exertion. Those who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention.
Schools are taking precautions during this examination period. Some have moved students taking exams to an air-conditioned venue, while others have brought out the air purifiers.
Singapore experienced one of the worst haze outbreaks last September when PSI almost hit hazardous levels, forcing schools to close.
The 24-hour PSI reading then was between 219 and 270, in the very unhealthy range. A PSI reading above the 300-point mark is considered hazardous.