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Following the particularly severe haze episode in 2015, when skies over much of Southeast Asia were blanketed in smoke for many days between Jun and Oct, researchers at Harvard attempted to estimate the impact of the extraordinarily polluted air on health and mortality.
After all, haze is treated mostly as an inconvenience, and few people believe it could kill them — but there is a real damage that it causes to millions exposed to it.
According to past observational data, the impact is very real, as all-cause mortality rises by 1% for every additional 1 µg/m³ of annual-average PM2.5 concentration in the air.
On this basis, Harvard researchers estimated that the 2015 haze season may have caused around 100,000 premature deaths in Southeast Asia — over 90% of them in Indonesia. In Singapore, the toll was estimated at around 2,200 people, although with a quite broad uncertainty interval of between 600 to 3,800 deaths.
It is important to note that this does not mean that that many people had actually died in Singapore (or elsewhere), as the study did not (because it could not) take into account various measures taken by each country to protect the public or the specific conditions in which people live.
Singapore, after all, is a densely populated city, where much of life takes place indoors. Pollution exposure of urbanites wearing masks and travelling on the MRT is obviously different from that of villagers in rural Sumatra. This is also why the Singapore government promptly rejected the findings published in the paper at the time and questioned its methodology.
Nevertheless, the study does provide us with some idea of how dangerous haze can be, if not treated seriously.
After all, the estimated 2,200 fatalities would have raised the total number of deaths in Singapore per year by 10% and would have been a whopping 15 times higher than the 151 people killed on the roads in 2015. It’s not a trivial matter.
This year’s episode was quite severe, but its peaks fell below those reached 11 years ago. The highest hourly PM2.5 reading was 288 µg/m³ last week, compared to 471 µg/m³ in 2015. That’s 39% lower. The highest daily PSI was 230 this year, compared to 322 in 2015, a drop of 29%.
That said, for the period between Sep and Oct, the average concentration of particulate matter across 2 months was almost identical at around 56 µg/m³ for both events. This means that prolonged exposure to pollution may have been quite comparable.
So, how does that affect the potential risks?
Well, with population growth of 12.2% from 2015’s 5.54 million, the mortality estimate would rise to about 2,500.
However, if we consider the 33% increase in annual mortality figures from 19,862 in 2015 to 26,499 in 2025 (which reflects the rise in more vulnerable elderly), this year’s haze episode could have killed up to 3,000 Singaporeans.
This is where analysis gets tricky, as it is impossible to assign responsibility for any number of deaths to a particular haze episode. There are too many potential factors at play.
For instance, the crude death rate for Singapore residents keeps increasing annually, due to a gradually ageing society. The fact that it slightly went up after 2015 can’t serve as evidence. Especially as the age-standardised rate has actually gone down in the past decade, meaning that the elderly live a bit longer than they used to.
Looking at the absolute numbers can be misleading as well. For instance, right after the 2015 haze, the number of additional deaths actually dropped in 2016, before shooting up in 2017.
Comparative data reveals an additional 174 deaths in May and 340 in Jun 2017 relative to 2016 figures.
While it might look like a slightly delayed jump, potentially attributable to haze pollution, the more likely explanation is the influenza epidemic between May and Jun 2017, where nearly 60% of the additional deaths for the year were concentrated.
We can’t rule out that some haze-related deaths do hide in the figures, but its real impact on mortality in Singapore appears to be much lower than Harvard findings would suggest.
This is consistent with a common-sense observation that Singaporeans are, in practice, far less exposed than people in neighbouring countries.
Public awareness, precautions advised by the authorities, and our indoor lifestyle, in mostly insulated, air-conditioned buildings and vehicles, have likely saved thousands of lives in the city.
Nevertheless, the danger still lurks outside, and if you do not take it seriously, it could take your life eventually.
Also Read: Jobs in Singapore: Top hiring industries revealed in latest manpower survey for Q4 2026
Featured Image Credit: Singapore haze crisis in 2015 / gdolgikh (depositphotos)
