SEPT 26 — Last weekend most areas in the country got a brief respite from the haze, with readings falling below 100 nationwide as at Sunday morning. But then it came back again.
And a couple of days later I saw people asking on social media why the haze outside in Kuching seems much worse than the official reading on the Department of Environment (DOE)’s website.
The general gist of concern seemed to be whether the Air Pollution Index (API) was rigged or something. In all likelihood, the answer is very likely no: this brief mismatch is probably due to how the index works.
Here are five things to keep in mind when we talk about air pollution in general.
The API is correct... based on its method
The API system tracks five types of air pollutants — ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2) and particulate matter with a diameter of less than 10 micron (PM10). (That’s smaller than the diameter of your hair.)
To put it briefly, the index takes into account running averages for each type of pollutant. However, the averaging time period is not uniform.
According to the DOE website, CO are calculated on eight-hour running averages; NO2 and O3 on one-hour running averages; and PM10 and SO2 are on 24-hour running averages.
When we talk about haze, which in our immediate case came from brush fires and open burning elsewhere in the region, they fall in the PM10 category.
So in all likelihood, the brief mismatch in API reading and how things looked outside earlier this week was probably caused by the way we measure PM10: it takes an average of the past 24 hours which, since the haze cleared up briefly for a good portion of that 24 hours, would cause the average figure for PM10 to be lower than the latest situation.
API can mean different things
When we look at the API, usually we want to know how bad the haze situation is. But contrary to what some may think at a glance, the figure isn’t an average of all five pollutants.
According to the DOE website, the API value that we see represents the highest API value among all the sub-APIs in that particular time period. In other words, the most dominant air pollutant, with the highest concentration, would set the API value reported.
This means that if the PM10 value is the highest, that’s what we’ll see. If, say, another type is more dominant, that type sets the value.
That said, the DOE says that PM10 is normally the highest value among the five.
PM10 is too general
So the air pollutants that we think of as “the haze” come under the PM10 category. But this is inaccurate and is solely due to size considerations.
PM10 are considered coarse particles. These are smoke, dust and dirt from our factories, industrial areas, even roads. Mold, spores and pollen belong to this category.
In contrast, the particles from burning vegetation and trees — of which our haze is mostly made up of — are much finer. So much so they are normally categorised as PM2.5, meaning finer than 2.5 micron.
The distinction matters. PM2.5 stays airborne much longer and can travel much farther. We’re talking up to weeks in the air going as far as hundreds of kilometres compared to PM10, which stays in the air for up to a few hours and may travel up to several dozen kilometres roughly.
And PM2.5 has much more severe health effects than PM10, which is why a lot of people have been urging the DOE to track PM2.5 levels separately. According to the department, it is still working on this.
It’s not just your lungs
That said, PM10 is still very small in the general sense. So much so that your nose hair probably won’t trap much of it because PM10 usually makes it into your lungs and gives you problems.
However, PM2.5 may go further. Not just in instances where you breathe through your mouth or exert yourself in polluted air, but because they are so much smaller than PM10.
PM10 can go right into your alveoli, which are air sacs in your lung and essentially the end of the road for the air you breathe. The walls of these air sacs, lined with blood capillaries, are where the gas exchange we learned about in school happens.
But while PM10 stops in the air sacs, PM2.5 can penetrate its walls if they are finer than 100 nanometres. This mean these very fine particles can travel to your other organs and give you other health problems.
Make no mistake, they can: the American Heart Association journal in 2008, for instance, published a study which found that these nano-size pollutants can lead to a build-up of plaque in your arteries, in turn putting you at risk of heart problems.
Particulate matter contributes to lung cancer
If you don’t feel like the haze is worth the trouble of taking precautions either for yourself or for your family, think again.
The International Agency for Research on Cancer (IARC) classifies particulate matter in outdoor air pollution as a Group 1 carcinogen. A carcinogen is defined as an agent that is directly involved in making people develop cancer.
In other words, having particulate matter in your body may cause cancer. It also implies that the so-called “healthy level of air pollution” may be mythical — the pollutants are still there, albeit in very little quantities, and we are still breathing them in.
That’s not all. The worse air pollution is, the higher the risk, obviously, as a study, published by The Lancet Oncology in August 2013, in Europe found.
After studying more than 300,000 people across nine European countries, the study concluded that there is a statistically significant association between PM10 levels and risk of developing lung cancer.
For every increase of 10 μg/m3 in PM10, the lung cancer rate among the people tracked rose 22 per cent. Worse, for every 10 μg/m3 increase of PM2.5, the rate rose by 36 per cent.
In other words, take precautions and follow the guidelines to stay as safe as possible in the current weather.
*This is the personal opinion of the columnist.
