SINGAPORE – The air quality in Singapore improved overnight as the hourly PM2.5 readings returned to “normal” for all regions and the 24-hour PSI levels stood in the “good to moderate” range for most regions.
At 6am on Oct 22, the one-hour PM2.5 were 38 in the north, 40 in the south, 37 in the east, 36 in the west and 32 in the central region.
The readings have been in the “normal” range for all five regions since 1am.
The hourly PM2.5 readings are measured in micrograms per cubic metre and are a gauge of the current air quality.
Scores from zero to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles, readings between 151 and 250 are considered high, and 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 disease, 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 Pollutant Standards Index (PSI) stood in the “good to moderate” range in the north (75), south (85), east (85) and central (98), with only the west (112) 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 in the range of 0 to 100, and “unhealthy” when it is in the range of 101 to 200. Beyond 200, it enters the “very unhealthy” band.
The highest 24-hour PSI reading this haze season was recorded at 10am on Oct 18, when it hit 230 in the western region, in the very unhealthy range.
Unhealthy air quality forecast for Oct 22
In an advisory on the evening of Oct 21, the National Environment Agency (NEA) said that unhealthy air quality is expected on Oct 22. PSI levels may range from 101 to 160.
Showers fell mainly over western Singapore in the afternoon of Oct 21 and smoke haze from Kalimantan was observed near Singapore, the agency said.
Smoke haze was also observed over Sumatra.
While showers are forecast over Singapore and the surrounding region on Oct 22, dry conditions are expected over the southern parts of Kalimantan, NEA said.
Under prevailing east-southeasterly or south-easterly winds, smoke haze from fires in Kalimantan may be transported towards Singapore, it added.
Smoke haze from fires in the region may continue to drift towards Singapore on Oct 23 due to south-easterly or south-southeasterly winds.
On Oct 24, winds are expected to shift to blow towards the south-west. Given the dry conditions forecast over southern and central Sumatra, smoke haze from Sumatra may 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, during which bad air persisted from Sept 23 to Oct 7.