Haze in Singapore: Air quality improves with ‘normal’ PM2.5 readings across the island

SINGAPORE – The air quality in Singapore improved on Oct 22, with hourly PM2.5 readings in the “normal” range for all regions while 24-hour PSI levels stood in the “good to moderate” range for most areas.

At noon on Oct 22, one-hour PM2.5 levels ranged from 19 to 45 across Singapore, with the highest reading clocked in the west – a marked drop from the season-high 288 in western Singapore on Oct 14.

The PM2.5 readings, which are measured in micrograms per cubic m and are a gauge of the current air quality, have remained in the “normal” range islandwide since 1am.

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.

Meanwhile, the 24-hour Pollutant Standards Index (PSI) stood in the “good to moderate” band islandwide at noon, except in the west, where the reading remained in the unhealthy range at 103.

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 zero 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 on 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.