Air quality in parts of Singapore in unhealthy range

SINGAPORE: Air quality in central, eastern and western Singapore remained in the unhealthy range on Wednesday (Oct 7), with hourly PM2.5 readings in the elevated band.

At 7am, the 24-hour Pollutant Standards Index (PSI) reading was 130 in central Singapore, 118 in the east and 117 in the west. The same regions also registered elevated 1-hour PM2.5 readings: 68, 61 and 85, respectively.

Meanwhile, northern and southern Singapore recorded PSI readings of 99 and 97, remaining in the moderate band.

In its Tuesday evening advisory, the National Environment Agency (NEA) said that scattered hotspots were detected in Kalimantan and Sumatra, while a few hotspots were detected elsewhere in southern Southeast Asia.

Moderate to dense smoke plumes from southern Sumatra and West Kalimantan were observed drifting towards Singapore, NEA said.

With dry weather forecast to persist over Kalimantan and southern and central Sumatra, as well as prevailing east-southeasterly to southeasterly winds, smoke haze is likely to continue drifting to Singapore.

The 24-hour PSI in Singapore is forecast to be in the high moderate to mid unhealthy range, NEA said.

When planning outdoor activities for the next 24 hours, the public is advised to use the 24-hour PSI forecast and health advisories.

When 1-hour PM2.5 levels are elevated, healthy people are advised to reduce strenuous outdoor activity for the next hour, while the elderly, pregnant women, children and people with chronic heart or lung conditions should avoid such activity.

The 24-hour PSI is Singapore's indicator of daily air quality and forms the basis of NEA's daily health advisories. It is calculated using six air pollutants - PM2.5, PM10, ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide - and reflects the average air quality of the past 24 hours.

The 1-hour PM2.5 reading, on the other hand, is the hourly average of the PM2.5 pollutant levels. PM2.5 is fine particulate matter with a diameter of 2.5 micrometres or shorter, and is the dominant pollutant during haze that causes harm to health.

A 24-hour PSI reading is considered "unhealthy" when it is in the 101 to 200 range, "very unhealthy" when it is within the 201-300 range and "hazardous" when it goes over 300.

The hourly PM2.5 reading is classified in four bands: normal, elevated, high and very high. It is considered elevated when it ranges from 56 to 150. The "high" band ranges from 151 to 250, and readings above that are classified as "very high".