SINGAPORE; Air quality in Singapore improved on the morning of Oct 22, with hourly PM2.5 readings in the “normal” range across all regions and 24-hour Pollutant Standards Index (PSI) levels in the “good to moderate” range in most areas.
At 9am on Oct 22, the one-hour PM2.5 readings were 36 in the north, 22 in the south, 43 in the east, 47 in the west and 40 in the central region.
The readings had been in the “normal” range across all five regions since 1am.
The hourly PM2.5 readings, measured in micrograms per cubic metre, indicate current air quality.
Scores from zero to 55 represent normal values, while readings between 56 and 150 indicate elevated concentrations of fine particles. Readings between 151 and 250 are considered high, while scores above 251 are classified as very high.
For healthy people, short-term exposure to high levels of haze particles may cause irritation of the eyes, nose and throat.
Haze particles can also affect the heart and lungs, especially in people who already have chronic heart or lung diseases, such as asthma, chronic obstructive pulmonary disease or heart failure.
The highest PM2.5 reading this haze season was recorded at 3pm on Oct 14 in the western part of the island, at 288.
Meanwhile, the 24-hour PSI stood in the “good to moderate” range in the north (74), south (84), east (82) and central region (93), with only the west (107) recording figures in the unhealthy range.
Air quality is considered “good to moderate” when the PSI, a 24-hour rolling average of six key air pollutants, is between zero and 100, and “unhealthy” when it is between 101 and 200. Readings above 200 fall within the “very unhealthy” range.
The highest 24-hour PSI reading this haze season was recorded at 10am on Oct 18, when it reached 230 in the western region, placing it in the “very unhealthy” range.
Unhealthy air quality forecast for Oct 22
In an advisory issued on the evening of Oct 21, the National Environment Agency (NEA) said unhealthy air quality was expected on Oct 22, with PSI levels potentially ranging from 101 to 160.
Showers fell mainly over western Singapore on the afternoon of Oct 21, while smoke haze from Kalimantan was observed near Singapore, the agency said.
Smoke haze was also observed over Sumatra.
Although showers were forecast over Singapore and the surrounding region on Oct 22, dry conditions were expected over the southern parts of Kalimantan, NEA said.
Under prevailing east-south-easterly or south-easterly winds, smoke haze from fires in Kalimantan could be transported towards Singapore, it added.
Smoke haze from fires in the region could continue to drift towards Singapore on Oct 23 due to south-easterly or south-south-easterly winds.
On Oct 24, winds were expected to shift and blow towards the south-west. Given the dry conditions forecast over southern and central Sumatra, smoke haze from Sumatra could drift towards Singapore, NEA added.
Singapore is currently experiencing its 18th day of unhealthy air, surpassing the 14-day stretch during the 2015 haze crisis, when poor air quality persisted from Sept 23 to Oct 7.
