Breathing particulate matter particularly bad for health

Ihave written about particulate matter in air on several occasions. To put it simply, it is not something we should be breathing. But where does particulate matter come from in the first place? The simple answer is it is all around us every day. From small micro-particles of dirt kicked up off of streets by passing cars to industrial smoke stacks to forest fires, there are any number of sources of particulate material in our air and environment.

Many of these sources could also be considered natural. For example, winds over the sands of the Sahara desert pick up large granules of sand along with the much smaller materials generated by the sand particles as they grind together.

The dust in a dust storm. While the sand drops out fairly quickly, the dust can be blown incredible distances – all the way across the Atlantic from Africa to America.

Traces of these particulates from the Sahara have been found on the islands in the Caribbean.

For that matter, household dust which consists mostly of discarded skin cells and such is a natural source of particulate matter in our environment as is pollen and many other organic substances.

For the most part these sorts of material do not constitute much of a health hazard. We are exposed to them on a daily basis from birth and develop a certain level of tolerance. In addition, the concentration in the atmosphere is generally not high enough to be a major concern. Generally, we can deal with low levels of particulates unless they trigger an allergic response.

On the other hand, when there are over 500 forest fires burning across the province, particulate material can reach hazardous levels.

Our smoky skies are a result of the combustion of organic material. Fire is a chemical reaction which should ideally release only carbon dioxide and water vapour.

That is, if you burn methane in pure oxygen then each methane molecule will react with exactly two oxygen molecules to give one carbon dioxide and two water molecules. Nothing else.

This is the simplest balanced equation for combustion but pretty much any combustion reaction of an organic substance is of the same form, provided it is carried out under controlled and ideal circumstances.

For example, the combustion of glucose consumes six molecules of oxygen and releases six molecules of carbon dioxide and six molecules of water.

If all fires occurred under ideal circumstances, they would generally not produce any particulates. We also wouldn’t smell them and the resulting smoke would be invisible. We generally can’t see the gases in the atmosphere.

However, real-world fires – particularly large forest fires – do not occur under ideal conditions.

Far from it. There are many factors at play. For example, trees and bushes are made up of much more than just organic material. Elements such as calcium, iron and magnesium are present and they do not respond to the intense heat inside a fire in the same way. Generally, ash is made of the non-combustible compounds within vegetation.

In addition, large forest fires effectively make their own weather.

They draw in air from the surroundings as the hot air at the center of the fire rises. This process is sporadic and may mean parts of the fire are burning at low oxygen levels. In this case, there is only partial combustion of the fuel.

Small particulate material is released with the superheated air and pushed out of the top of the air column.

The intense heat of forest fires can also volatilize small inorganic particulates such as silicates and aluminates found in the soil. The particles behave like any other particulate material and circulate with the air currents.

The resulting material gives the smoke from a fire its opacity as we have been observing for the past several weeks.

In particular, the levels of PM 2.5, which are particles 2.5 microns in size, have soared with this summer’s fire season. There are a number of monitoring devices downtown, at the university, and throughout the community.

All show readings which are consistently 10 to 20 times above normal and on a day like last Friday, particulate levels went through the roof.

Why are these particles so bad? They are small enough to penetrate into the tiniest passages in our lungs and the hair-like cilia which usually expels particles from our lungs have trouble moving these particles out. Indeed, they are small enough to penetrate the cells lining our lungs and enter the circulatory system. This can lead to serious medical conditions ranging from asthma to heart attacks.

Further, various studies have shown increases in the concentration of PM 2.5s correlate directly with increased levels of lung cancer and coronary diseases.

Simply put, breathing in particulate materials is not healthy and at the levels found throughout the city, it should be avoided as much as possible.