PARTICULATE MATTER

Airborne particulate matter (PM) is the general term used to describe a mixture of microscopic solid particles and liquid droplets found in the air we breathe.  Particulate matter is categorized by its size – mainly because of the different health effects associated with the different sizes. 

The greatest health hazard from particles comes from the smallest ones – 2.5 microns (2.5 µm) in diameter or less – because we easily inhale these small particles into our lungs.  These are called Fine Particulate Matter 2.5 or PM_2.5. Particulate Matter 10 or PM10 refers to particles with a diameter less than 10 microns (10 µm).  To put things in perspective, a fine particle is approximately 30 times smaller that the average diameter of a human hair.

Sources

Particulate matter can come from aerosols, smoke, fumes, fly ash and pollen.  Fine particulate matter comes from fuel combustion – motor vehicles, smelters, power plants, industrial facilities, residential fireplaces, woodstoves, agricultural burning and forest fires.  It can also be formed indirectly through a series of complex chemical reactions in the atmosphere.   

Significant amounts of PM_2.5 are carried into Ontario from the U.S. During periods of widespread elevated levels of fine particulate matter, it is estimated that more than 50 per cent of Ontario's PM_2.5 comes from the U.S.

Effects on health and the environment

When we breathe in, the hairs in our nose and air passages remove particles larger than 10 µm in size. Particles smaller than 10 µm can penetrate into the lungs, where they cause problems and affect our health.

Some of the most common health effects include irritation of your eyes, throat and lungs. For people with existing respiratory conditions, such as asthma, bronchitis, cardiovascular or lung disease, breathing in particles can make the conditions worse.  Children and elderly people are also more sensitive to the effects of PM. 

Particles can also reduce your capacity to resist infection. Studies show that particles can increase the number of hospital admissions and emergency department visits, school absences, lost work days and restricted activity days.   

Fine particulate matter is also responsible for environmental impacts such as corrosion, soiling, damage to vegetation and reduced visibility.