Singapore’s air quality deteriorated on Sept. 17, pushing the 24-hour Pollutant Standards Index (PSI) in the central region to 102 and entering the unhealthy range, according to the National Environment Agency. The reading crossed the threshold at 9 p.m. before climbing to 103 at 10 p.m., following a brief reprieve the previous day when regional readings improved to moderate levels.
Regional PSI and PM2.5 Breakdown Across Singapore
While the central region crossed into the unhealthy bracket, air quality readings in other parts of the island remained moderate. According to the National Environment Agency, 9 p.m. readings registered at 72 in the north, 70 in the south, 81 in the east, and 93 in the west. By 10 p.m., the north edged up to 73 and the west reached 95, while southern and eastern measurements remained unchanged.
Hourly PM2.5 readings—which measure the current concentration of fine particulate matter—showed elevated levels in specific zones. According to the National Environment Agency, hourly PM2.5 concentrations at 9 p.m. sat in the normal band for the north at 55, the south at 40, and the east at 51, but entered the elevated band in the west at 64 and the central region at 93. By 10 p.m., the north’s hourly PM2.5 reading rose to 58, crossing into the elevated band as well.
Health Advisories and Official Guidance
The National Environment Agency defines air quality as unhealthy when the 24-hour PSI ranges between 101 and 200. An hourly PM2.5 reading between 56 and 150 indicates an elevated concentration of fine particles.
To manage daily exposure, the National Environment Agency advises the public to consult hourly PM2.5 readings for immediate outdoor activities and rely on 24-hour PSI figures for long-term daily planning. During periods of elevated pollution, healthy individuals should reduce prolonged or strenuous outdoor exertion. Meanwhile, vulnerable populations—including the elderly, children, pregnant women, and individuals with chronic heart or lung disease—should minimize or completely avoid outdoor activities.
Haze Risks and Meteorological Outlook
The recent spike marks a continuation of haze pressures that first returned to unhealthy levels on Sept. 4, marking the first time the index crossed that threshold since October 2023. Central region readings previously peaked at 154 on Sept. 15.
According to a haze advisory issued by the National Environment Agency on Sept. 16, persistent dry conditions over Indonesian hotspots in Sumatra and Kalimantan, combined with prevailing winds blowing from the south or south-east, keep Singapore at a continued risk for haze. However, relief may arrive soon. The Meteorological Service Singapore forecasted on Sept. 16 that increased showers are expected for the remainder of September compared to the first half of the month, which could improve overall air quality.
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