The 24-hour Pollutant Standards Index (PSI) in Singapore’s central region oscillated near the unhealthy threshold, recording a reading of 103 at 3am on October 4 before dropping to 95 by noon. This followed a period of instability where the index hit 100 at 11pm on October 3, temporarily dipping from a peak of 102 earlier that morning. According to the National Environment Agency (NEA), the unhealthy band is officially defined as a 24-hour PSI between 101 and 200. While the central region fluctuated, PSI readings across other parts of Singapore remained within the moderate range, spanning between 73 and 86 at midday on October 4.
Understanding these fluctuations is essential for planning daily routines, as the 24-hour PSI serves as a primary guide for scheduling outdoor physical exertion. When the air quality reaches the unhealthy category, the NEA advises the public to reduce strenuous outdoor activities. Specific precautions are recommended for elderly residents, pregnant women, and children, who are urged to minimize such activity, while those with chronic heart or lung conditions are advised to avoid it entirely.
The recent haze is attributed to smoke plumes from southern Sumatra and Kalimantan, as dry weather persists across the region. While the 24-hour readings showed volatility, the one-hour PM2.5 concentrations, which track immediate fine particulate matter, remained in the normal range of 14 to 28 across all regions as of noon on October 4. The NEA warned that there remains a risk of smoke haze affecting Singapore, with the 24-hour PSI expected to hover in the high-moderate to low-unhealthy range as winds strengthen.