The ongoing haze that has covered Singapore over a week reached the 'unhealthy' range on Wednesday, Sept 18, affecting mostly the morning workers and students, after hovering in the moderate and unhealthy range a day before.
The one-hour PM2.5 reading was 76 micrograms per cubic metre in the central part of Singapore and 102 in the southern part, as of 2pm on Wednesday. The Pollutant Standards Index (PSI) for 24 hours remained at 112 in the northern and central regions, and higher at 128 in the south.
According to the estimates of National Environment Agency (NEA), a PSI reading of 101 to 200 is in the unhealthy range that requires an advisory for the public to cut down on outdoor activities. The forecast for the next 24 hours are expected to fluctuate between Band I (Normal) and Band II (Elevated).
"PSI for the next 24 hours is forecast to range between the high end of Moderate range and the low end of Unhealthy range, and depending on wind conditions, may enter the mid-section of the Unhealthy range if denser haze from Sumatra is blown in," noted the advisory on NEA website as of Wednesday afternoon.
On moving out, the advisory cautioned people that "Given the air quality forecast for the next 24 hours, healthy persons should reduce prolonged or strenuous outdoor physical exertion." For the elderly, pregnant women and children, the advisory clearly stated that they should minimise "prolonged or strenuous outdoor physical exertion."
For those suffering from chronic lung or heart diseases, it said outdoor physical exertion should be avoided. Persons who are sick, especially the elderly and children, are advised to seek medical attention by the NEA.
The Index has four bands on the PM2.5 concentration scale:
0 to 55 for normal,
56 to 150 for elevated,
151 to 250 for high, and
Above 250 - very high.
The five bands on the PSI scale are:
0 to 50 for good,
51 to 100 for moderate,
101 to 200 for unhealthy,
201 to 300 for very unhealthy, and
Above 300 - hazardous.
Elsewhere, 109 hot spots were spotted in Sumatra with haze, which the NEA said may probably persist due to the dry conditionsin Indonesia. Governments in the region have urged offices and schools to initiate anti-haze measures such as having air purifiers and reducing outdoor activities.
If the PM2.5 concentration readings cross into the high band of 151-250, then resident welfare associations will be made active to take up more steps, said government sources. Local public relations officer Ng Xinyu said the PSI hit the unhealthy level for the first time since 2016.