PSI to include PM2.5 levels from May

Smog blanketed Singapore in June last year, with much of the skyline, including The Singapore Flyer shown here, barely visible.

SINGAPORE - From May, Singapore will have a new Pollutant Standards Index (PSI) that includes tiny, hazardous particles referred to as PM2.5.

The move is timely as it gives a better picture of the toxicity of the air as the PM2.5 can enter people's lungs and blood to cause harm, said experts interviewed.

Minister for the Environment and Water Resources Vivian Balakrishnan said as much when he announced the change in Parliament yesterday.

"This revised single index will reflect whichever of six pollutant parameters is the worst.

"In reality, we expect the PSI will be determined almost all the time by the levels of PM2.5. As a doctor, I think this is reasonable as PM2.5 is the one we are most concerned with," he said.

Many people had called for more data on PM2.5 last year, during Singapore's worst haze episode, owing to its health impact.

Nanyang Technological University's Professor Ang Peng Hwa, who created the Haze Elimination Action Team Facebook campaign in 2007, said the new PSI "reports more accurately the situation, that PM2.5 is bad for health".

The National Environment Agency (NEA) said yesterday that based on the present PSI, each of the past five years had between 91 and 96 per cent of "good" air quality days, and just 4 to 9 per cent of "moderate" days.

But with the revised PSI, the figures would be 1 to 4 per cent of "good" days each year and 92 to 98 per cent of "moderate" days.

NEA said: "There will be no change to normal routines on the ground as people can carry on normal activity if air quality is in the 'good' or 'moderate' range."

The current PSI is calculated from the worst of five other pollutants: sulphur dioxide, ozone, nitrogen dioxide, carbon monoxide and particles called PM10.

Another change taking place in May is that the Government will give hourly updates that are more current on PM2.5 levels in the air.

Now, the updates are given hourly too but are averaged from readings in the previous 24 hours.

With the new hourly and more current PM2.5 updates, NEA will publish a lot more raw data that is useful for academics and scientists, Dr Balakrishnan said.

Last night, the three-hour PSI also crept up to 84 at 8pm, close to the unhealthy range. NEA said it was because of hot spots in southern Johor. The number of hot spots detected in Peninsular Malaysia rose to 149 yesterday from 86 on Monday, while those in Sumatra numbered 259, up from 228, the agency said.


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