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PSI index reaches 'unhealthy' level

(Yahoo! photo)

Haze reaches "unhealthy" level in Singapore as PSI reading passes 100-mark

Singapore's haze situation worsened on Monday as the three-hour Pollutant Standards Index (PSI) reading hit 111 as of 4pm.

According to the National Environment Agency's (NEA's) website, PSI values between 101 and 200 denote "unhealthy" air quality.