Singapore's air quality hits unhealthy levels as regional haze persists

On the evening of September 4th, the air over eastern Singapore turned unhealthy. The Pollutant Standards Index—the measure by which Singapore tracks air quality—climbed to 102 at 9pm, then edged higher to 104 by 11pm. Two hours earlier, the central region had already crossed into dangerous territory, posting a reading of 101 at 7am before worsening dramatically to 123 by nightfall. The north, south, and west of the island remained in the moderate range, with readings of 88, 87, and 99 respectively, but the eastern and central zones had entered the band where health authorities recommend people curtail time outdoors.

This was the first time since October 2023 that Singapore's air quality had deteriorated to unhealthy levels. The culprit was familiar: haze drifting across the region from forest and land fires burning in Sumatra and Kalimantan, in Indonesia. Since around August 21st, dense smoke had been visible over southern and central Sumatra and various parts of Kalimantan on most days. The fires themselves had been fueled by a super El Niño weather pattern, which had dried out the landscape and created ideal conditions for flames to spread and persist.

The Meteorological Service Singapore had warned on September 1st that hazy conditions would likely continue for the next two weeks. Dry weather was expected to dominate the surrounding region through the first half of September, with only sporadic showers forecast in the second week. That dry pattern meant the fires would keep burning, and the smoke would keep drifting. How much Singapore would suffer depended largely on wind direction—a variable beyond anyone's control.

By noon on September 4th, as readings climbed, the Haze Task Force activated contingency planning. Officials announced they would open air-conditioned rooms in community centres and selected residents' committee centres if the PSI crossed into the "very unhealthy" range, defined as readings above 200. These spaces would serve as refuges for people seeking relief from the degraded air. The National Environment Agency issued an evening update forecasting that haze would persist through September 5th, with air quality expected to fluctuate between the higher end of moderate and the middle of the unhealthy range.

The advisory was clear: reduce outdoor activities. For vulnerable populations—the elderly, children, people with respiratory or heart conditions—the guidance was more urgent. The air quality index that had climbed to 104 in the east and 123 in the centre represented a threshold beyond which prolonged exposure carried measurable health risk. Singapore, a densely populated island nation with limited geographic buffer from its neighbours' environmental challenges, was once again experiencing the consequences of transboundary pollution, dependent on weather systems and fire management thousands of kilometres away to determine whether its citizens could safely breathe.