SINGAPORE - The three-hour Pollutant Standards Index (PSI) has climbed back up into the "unhealthy" range after a brief respite from the worst of the haze yesterday afternoon.
Yesterday, the three-hour PSI reading came down to within the 51 to 100 "moderate" range after hitting a peak of 155 late Monday - the highest since Southeast Asia's prolonged haze crisis in 1997-1998.
Today, the PSI reading was 77 at 6am, but went up steeply to 152 by 1pm.
The 24-hour noon PSI reading ranged from 91 to 107, with the highest PSI readings in the North and West.
The PSI reading of PM2.5 concentration, or very fine particulate matter, was between 93 and 118 micrograms per cubic metre.
Around 30 times smaller than a human hair, PM2.5 particles have long been identified as a respiratory problem, as their size enables them to lodge deep in the lungs and penetrate the bloodstream.
As these very fine particles are more hazardous to the health, a range of 40 to 65 typically carries a health advisory from the National Environment Agency (NEA). Given the current hazy conditions, NEA has advised children, the elderly and those with heart or lung diseases to reduce prolonged or heavy outdoor activities.
The haze situation could worsen in the coming days, as the number of hot spots in Sumatra quadrupled from 46 to 187 within just a week.
According to the National Environmental Agency, June to September is the traditional dry season for the southern ASEAN region. The agency observed that weather conditions in the region have become drier.
In the coming months, occasional extended periods of drier weather can be expected in the region and transboundary smoke haze could affect the region during periods of persistent dry weather conditions, NEA said.
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