Unhealthy air quality recorded in three regions of Singapore — Channel NewsAsia
In Singapore, on the morning of September 5, the 24-hour Pollutant Standards Index (PSI) was in the unhealthy range in the central, western and eastern regions. At 6:00 a.m., the reading was 120 in the central region, 103 in the west and 102 in the east, Channel NewsAsia reports, citing Singapore's National Environment Agency (NEA).
Readings in the city’s regions
In the northern and southern regions, readings remained in the moderate range, at 86 and 88 respectively. A 24-hour PSI level from 101 to 200 is considered unhealthy. For the first time since October 8, 2023, the index crossed this threshold at 7:00 a.m. on September 4.
After that, the NEA began publishing daily haze advisories, including a 24-hour PSI forecast, so that residents could plan activities and measures for the following day. In its first advisory on the evening of September 4, the agency said Singapore could continue to be affected by transboundary haze. The forecast projected readings from the upper end of the moderate range to the middle of the unhealthy range.
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How air quality is measured
The 24-hour PSI is Singapore’s indicator of daily air quality, on which the NEA’s health advisories are based. It is calculated using six pollutants: PM2.5, PM10, ozone, sulfur dioxide, nitrogen dioxide and carbon monoxide.
The one-hour PM2.5 reading is tracked separately and reflects the average concentration of fine particles over one hour. PM2.5 particles have a diameter of 2.5 micrometres or less and are the dominant pollutant during haze, which is harmful to health. A PSI level from 201 to 300 is classified as very unhealthy, while a reading above 300 is classified as hazardous.
The NEA also said that members of the Haze Task Force had introduced their own action plans and recommendations to protect public health and well-being.
