SINGAPORE — While the Government announced yesterday that it will be publishing haze-related data more regularly, Environment and Water Resources Minister Vivian Balakrishnan argued against calls for spot readings.

This is because “individual data points” can fluctuate a lot, he said — citing how the Pollutant Standards Index (PSI) readings can vary by “a factor of almost a hundred” within an hour, as they did on Wednesday night and yesterday afternoon — and focusing on minute-to-minute readings would be akin to “chasing one’s tail”.

“It is important that we analyse and assess the data appropriately so that it becomes useful, actionable advice,” said Dr Balakrishnan at a press conference yesterday called by Prime Minister Lee Hsien Loong on the haze situation. “In planning an appropriate response, we cannot be reacting reflexively without thinking or considering or analysing the implications”. Instead, the Government will look at the situation on a “day-to-day basis” and, based on 24-hour data, give “appropriate advice” on how the public should cope with the haze crisis, he added.

As the haze worsens, some Singaporeans have questioned the accuracy of the PSI readings, arguing that it does not tally with the situation outside their windows. Those who were more cynical even wondered whether data was doctored.

Dispelling the doubts, Dr Balakrishnan said that data for all PSI readings will also be published on the Government’s data.gov.sg website “so there is no question about data abstraction or amputation”.

The Government is “committed to total transparency”, he reiterated, noting that Singapore is “probably the only country” publishing these readings which are updated every hourly.

Mr Lee added that there might seem to be discrepancies in the published readings when the haze outside one’s window “looks terrible”, but this was because the figure represented the average reading over three hours, and so could be better or worse than what is experienced on the ground.

Dr Balakrishnan also addressed queries on the delay in the publication of PSI readings on Wednesday night, saying heavy traffic “literally (crashed)” the National Environment Agency’s (NEA) website.

On whether Singapore would follow Malaysia’s decision to shut schools once PSI readings breach the 300 mark, Mr Lee said there would not be an “automatic” line where students would be kept at home. “But if the PSI keeps on going up we will ... look very carefully and ask ourselves what we can and cannot do,” he said.

Defence Minister Ng Eng Hen added that the professional view was that the haze would have varying impact on individuals’ health, depending on factors such as age, pre-existing conditions and levels of activity. Unlike infectious diseases, he added, the haze has “(much) more variability” and the Government would assess on an “ongoing basis” if there is a risk to the public before making any decisions.

Clear guidelines would be drawn up over the next few days, said Dr Ng, seeking the public’s patience.

Yesterday, it was also announced that the 24-hour PSI and PM2.5 concentration readings will be published hourly, instead of only at three time intervals daily currently. Three-hour PSI readings will also be posted online round-the-clock and not just from 6am to midnight.

At a media briefing yesterday, NEA Project Director (Environmental Monitoring Systems) and Chief Scientific Officer Indrani Rajaram also said the 24-hour PSI index system, which is derived from average values over the period, was in accordance with the United States Environmental Protection Agency guidelines.

She added that the index is based on the pollutant that has the highest concentration over a 24-hour period, which, in this haze, is PM10. On queries about the 3-hour and 24-hour PSI readings, Ms Indrani said the 24-hour readings are a “better reflection” of the total exposure of an individual.