SINGAPORE - The haze worsened on Monday (Sept 7) as the three-hour Pollutant Standards Index (PSI) hit 123 points at 6pm.

The air quality measure was in the moderate range since morning, and breached 100 points at around 4pm.

The 24-hour PSI reading at 6pm was 76 to 87, and has ranged between 74 to 96 since 6am on Monday.

A 24-hour reading above 100 is considered unhealthy, while one between 50 to 100 is moderate. There is no health advisory attached to the three-hour reading.

When the 24-hour PSI inches above 100, authorities advise healthy people to reduce prolonged or strenuous outdoor activity.

The elderly, pregnant women and children should do as little of such activity as as possible, while those suffering from chronic lung or heart disease should not engage in these activities.