PSI

Tourists look at the Singapore Flyer on a hazy day in Singapore June 17, 2013. The haze worsened on Monday with the Pollutant Standards Index (PSI) hitting 111 at 4 pm, according to local media.

Edgar Su/Reuters

Tourists look at the Singapore Flyer on a hazy day in Singapore on Monday. The haze worsened on Monday with the Pollutant Standards Index hitting 111 at 4 pm, according to local media.