Govt debunks PSI rumours

A worker wearing a mask holds a stop sign as he directs traffic along the East Coast Park in Singapore as haze engulfs the island state, June 21, 2013.

DON'T spread false information on the haze.

That was Acting Manpower Minister Tan Chuan-Jin's call even as the country is getting a temporary respite from the haze.

He noted in a Facebook post yesterday that some people have fabricated falsehoods on the haze situation.

These include claims that the National Environment Agency (NEA) changed a three-hourly Pollutant Standards Index (PSI) reading for 10pm last Wednesday from 393 to the actual value of 321 on its website. A photo of a screenshot with the 393 figure was also shared online.

"It was a lie. The photo was doctored... It is unfortunate that this is happening amid this present situation," he said.

Mr Tan said that if people want to be critical about the situation, "it's fair game".

"But don't fabricate lies. Please. Not in the midst of dealing with issues of public concern and safety," he said.

The Government has been debunking rumours related to the haze on

For instance, it noted there were claims that the PSI readings on NEA's website do not take into account fine particles called PM2.5, but are based solely on PM10 particles. The site said these claims were false.

PM10 refers to particulate matter smaller than 10 microns, while PM2.5 is for particulate matter smaller than 2.5 microns. So, PM2.5 is a subset of PM10.

PM10 measures "would also capture what is captured in the PM2.5 readings", so "a rise in PM2.5 levels would reflect a change in the PSI", the site said. PM2.5 is more dangerous than larger particles.

The PSI measures five pollutants: sulphur dioxide, nitrogen dioxide, carbon monoxide, ozone and PM10.

The NEA said afternoon showers are expected today and in the next two days.

The 24-hour PSI is likely to be in the moderate range today. But due to elevated PM2.5 levels, the health advisory for the public is in the unhealthy range.

The NEA said rain can "significantly reduce" PM10, but it is less effective when it comes to PM2.5, as those are much smaller. It would therefore take longer for the rain to "wash down" the particles.