Almost every year, Singapore experiences some deterioration of air quality due to trans-boundary haze, largely due to its geographical proximity to Indonesia where wildfires are being used to clear land. Like many haze episodes encountered in the past, severe haze engulfed the city state of Singapore in June 2013. The 24-hour Pollutant Standard Index (PSI) on 22 June 2013 hit the highest reading recorded ever in Singapore, in the ‘very unhealthy’ range of 246 and the 24-hour PM2.5 concentration was highest at 314μg/m3 on 20 June 2013.
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