Health Impacts of Haze from Indonesia Pt. 1

The haze from the Indonesian fires continues its hazardous pass through Malaysia and Singapore, causing alarm and frustration from impacted residents. Walking around Singapore has been a crazy experience as the visible haze feels dystopian compared to Singapore's usual hyper cleanliness. I wanted to deep dive into the known health impacts and what exactly to expect from exposure in this series.

PSI/API Index and PM2.5

Both Singapore and Malaysia use a pollutant index to warn citizens on the risks of air pollution. Singapore's Pollutant Standards Index (PSI) and Malaysia's Air Pollutant Index (API) both calculate a number of air pollutants and translate the impacts to a 0 to 500+ scale. Both denote unhealthy levels starting at 101, very unhealthy above 200, and hazardous above 300. Malaysia declares a Haze Emergency Declaration at 500. Singapore peaked this year at 164 while some regions in Malaysia saw numbers as high as 476 to 520 such as Serian, Sarawak.

While the two systems have slightly different ways of calculating the index, both measure PM2.5 among others air pollutants. PM2.5 calculates the amount of fine atmospheric particulate matter at or below 2.5 micrometers in the air. This is the most relevant group of pollutants to track as it measures the chemicals related to the haze stemming from Indonesia's smouldering peatland fires. PM10 similarly measures particulate matter, but larger at or below 10 micrometers. PM2.5 is more toxic and harmful due to its smaller size, making them more likely to be absorbed in the bloodstream and more chemically active due to the greater surface area.

This 2017 study found the chemical makeup from haze is dominantly Organic Carbon (OC) with Polycyclic Aromatic Hydrocarbons (PAHs) and toxic heavy metals like Cadmium, Nickel, Lead, and Chromium. The latter two categories make up a much smaller portion of the haze and while repeated exposure is not good, it is less of a concern than OC which dominates the mix.

What may be more alarming is this haze is categorized as aged smoke vs raw smoke, chemically altered by UV exposure from the days the smoke took to travel to the impacted areas. As this paper examines this could lead the chemicals in the haze to cause more oxidative stress on the system, though not all studies align to this conclusion.

Known Health Impacts - Respiratory and Cardiovascular

I will deep dive into this a bit more in a subsequent post, but the tldr is there are limited long-term health studies that can give us good evidence on repeated exposure and cancers or cardiovascular disease.

What is clear are the short term impacts. Haze exposure even in the moderate zone can lead to respiratory infections and illnesses. In Malaysia, where the haze is more severe, higher unhealthy zones can lead to respiratory fatalities. This study in the Klang Valley found that haze days were associated with a 19% rise in natural-cause respiratory mortality overall, and higher among specific groups: roughly 30% for children under 14 and about 30% for men on the day of exposure. Effects persisted a day or two after.

Singapore is not safe from haze related fatalities though. While haze effects are less and of shorter duration, moderate to unhealthy levels can still lead to greater cardiovascular issues like heart attack and stroke. That's why Singapore warns citizens to avoid rigorous exercise during unhealthy haze periods, especially if you have underlying pre-existing issues.