Singapore records unhealthy air quality in central, eastern and western regions

Air quality in the Republic deteriorated further on Monday (Sept 14) afternoon, with the eastern and western regions joining central Singapore in recording unhealthy 24-hour Pollutant Standard Index (PSI) readings.At 4pm, 24-hour PSI reading was between 87 and 115, in the moderate to unhealthy range, with unhealthy readings in the central (115), eastern (101) and western (101) regions.Meanwhile, 1-hour PM2.5 hit a recent high of 132 in central Singapore at 2pm, before easing to 128 at 4pm.In other parts of Singapore, the one-hour PM2.5 reading at 4pm was between 64 and 89, in the elevated range.PM2.5 indicates the level of fine micro-pollutants in the air and is the current air quality that matters — when planning to conduct or participate in outdoor activities immediately.Readings of between 51 to 100 are in the moderate-band, while readings of between 151 and 250 denote the high-band. The highest one-hour PM2.5 concentration ever recorded in Singapore was 471 µg/m³ in western Singapore at 11pm on October 19, 2015.