Air quality in western and central Singapore has deteriorated, with the Pollutant Standards Index (PSI) reaching unhealthy levels of 102. This follows earlier unhealthy readings in the eastern part of the island on September 4th. The PSI in the east has since improved slightly, currently registering at 99 as of September 5th. These elevated PSI levels indicate a decline in air quality and potential health implications for residents. Authorities are monitoring the situation closely, though the source of the pollution is not specified in this report. Individuals sensitive to air pollution are advised to take necessary precautions. Further updates are expected as the situation evolves.