Air quality in central Singapore deteriorated Sunday evening, with the 24-hour Pollutant Standards Index (PSI) crossing into the unhealthy range at 9pm. The reading indicates a potential health risk for residents, particularly those with respiratory conditions. This decline reverses recent improvements in air quality observed across the country. Authorities have not yet issued specific advisories, but individuals are generally advised to reduce prolonged outdoor exertion when the PSI is in the unhealthy range. The central region of Singapore is currently experiencing the poorest air quality. Further updates will be provided as the situation develops, monitoring conditions in central Singapore closely.