SINGAPORE - Air quality in Singapore improved on Tuesday morning following a hazy day on Monday when air quality deteriorated to its worst levels this year.

The three-hour Pollutant Standards Index (PSI) was 93 at 7am on Tuesday. It hit an unhealthy 153 at 7pm on Monday, its worst levels this year.

At the unhealthy range of 101-200, healthy people should reduce prolonged or strenuous outdoor physical exertion. Older folk, pregnant women and children should minimise such activity, while those who do not feel well or have chronic lung or heart conditions should avoid it.

At moderate levels of between 50 and 100, normal activities can still be carried out.

The National Environment Agency (NEA) said that the pollution on Monday was due to smoke haze blown in from central Sumatra by prevailing south-westerly winds. There were 97 hot spots detected in Sumatra and 74 in Kalimantan.

The highest three-hour PSI reading this year had previously been 129, recorded in September. Last year, the PSI reached an unprecedented 401 in June, a level considered hazardous.

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