Haze creeps into unhealthy range as Sumatra hot spots spike

SINGAPORE — Haze readings, which edged into the unhealthy range yesterday afternoon and continued climbing into the night, are expected to be in the high end of the moderate range or low end of the unhealthy range today.

At 3pm yesterday, the three-hour Pollutant Standards Index breached the unhealthy mark and readings edged up steadily to hit 127 by 9pm, before receding slightly to 126 at 10pm. Any reading over 100 up to 200 is considered unhealthy.

The PM2.5 — tiny particles smaller than 2.5 microns in diameter — levels were also elevated in most regions, with one-hour concentrations ranging from 59 to 82 micrograms per cubic metre at 5pm, said the National Environment Agency (NEA). A 24-hour PM2.5 reading of between 56 and 150 is considered unhealthy.

In an update posted on its website at 5pm yesterday, the NEA said the haziness was smoke blown in by prevailing southerly winds from Sumatra, whose southern part has experienced drier weather, leading to a “sharp increase” in the number of hot spots there. A total of 205 hot spots were detected in Sumatra yesterday, it added.

Last Tuesday, the NEA had said the threat of serious haze appeared to have been averted for the rest of the year, with the onset of the Inter-Monsoon season over the past week signalling the end of the traditional dry period in the region. The Inter-Monsoon period normally lasts from October to November, and is characterised by more rainfall and light winds that are variable in direction.