Haze in S’pore: Air quality in central region slips back to unhealthy range

SINGAPORE – The air quality in the central region of the island slipped back into the unhealthy range overnight, after dipping temporarily to the moderate range at 11pm on Oct 3.

The 24-hour Pollutant Standards Index (PSI) reading, which stood at 100 at 11pm on Oct 3, began inching upwards two hours later and reaching 103 at 3am on Oct 4.

At 7am on Oct 4, the PSI reading in the central region was 102.

The PSI readings for the other parts of Singapore remained in the moderate range, ranging between 78 and 90 at 7am.

The PSI reading is a 24-hour rolling average of six key air pollutants and is used in planning for outdoor activities the next day.

Air quality is considered unhealthy when the 24-hour PSI is in the range of 101 to 200, during which the National Environment Agency (NEA) advises the public to at least reduce outdoor activities. PSI readings of 51 to 100 are considered moderate, while values of zero to 50 are in the “good” range.

Air quality started worsening at 11am on Oct 3 when the 24-hour PSI hit 102, the first time the reading in any region here reached unhealthy levels since 10pm on Sept 30.

Meanwhile, the one-hour PM 2.5 readings, which are used as a gauge for immediate activities, stood in the normal range between 29 and 43, across all regions at 7am.