SINGAPORE - The haze in Singapore has been thinning since early Friday morning.

As at 7pm on Friday, the 24-hour Pollutant Standards Index (PSI) was 129-148, putting the air quality in the mid section of the unhealthy range, which is from 101 to 200, the National Environment Agency (NEA) said.

The 24-hour PSI, a measure of air pollution, has been falling after peaking at between 158 and 182 at 5am on Friday.

That was the highest level that the 24-hour PSI has hit since being tweaked in April last year. Previously, the highest 24-hour PSI was between 107 and 125 on Oct 7 last year.

The number of hotspots detected in Sumatra has also dipped, from 328 on Thursday to 304 on Friday.

The improvement is due to a shift in the direction of the prevailing winds to the southeast, which is forecast to continue on Saturday, the NEA said.

The 24-hour PSI is expected to continue being in the low to mid part of the unhealthy range, and may even fall into the high end of the moderate range, which is between 51 and 100, it added.

For now, healthy people are advised to reduce prolonged or strenuous outdoor physical exertion. The elderly, pregnant women and children should minimise this, while those with chronic lung or heart disease should avoid this.

People who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention.

Updates on the haze situation are available on the haze microsite (www.haze.gov.sg), the NEA website (www.nea.gov.sg), the NEA Facebook page (www.facebook.com/NEASingapore) or the myENV app.