Matter  Particulate Matter (PM_<10) Airborne particulate matter, known as PM, is one of the major components of smog. PM include microscopic particles in the air. These particles, capable of being inhaled by humans, are divided into two size ranges: PM_2.5 and PM_<10. Between the two, "fine" particles less than 2.5 micrometers in size (PM_2.5) are responsible for causing the greatest harm to human health. 1/20th the width of a human hair, these fine particles can be inhaled deep into the lungs reaching areas where the cells replenish the blood with oxygen. They can cause breathing and respiratory symptoms, irritation, inflammation and damage to the lungs and premature deaths.  Some PM_2.5 are released directly to the atmosphere from industrial smokestacks and automobile tailpipes, but a large percentage is actually formed in the atmosphere from other pollutants such as sulphur dioxide (SO₂), nitrogen oxides (NO_x) and volatile organic compounds (VOC). Fossil fuel combustion in motor vehicles, power plants and large industries, as well as industrial process and solvent use are major sources of these other pollutants. Although not as serious a threat to human health as PM_2.5, "coarse" particles covering the range from 2.5 to 10 micrometers in diameter (PM_<10), are also known to cause adverse health effects. When inhaled, they tend to be deposited in the upper parts of the respiratory system from which they can be eventually expelled back into the throat. Coarse particles generally remain in the form in which they are released into the atmosphere without chemical transformation, eventually settling out under the influence of gravity. While some of these coarse particles are generated naturally by sea salt spray, wind and wave erosion, volcanic dust, windblown soil and pollen, they are also produced by human activities, such as construction, demolition, mining, road dust, tire wear and grinding processes of soil, rocks, or metals.  Health Effects of PM Numerous studies have linked PM to aggravated cardiac and respiratory (heart and lung) diseases such as asthma, bronchitis and emphysema and to various forms of heart disease. Children and the elderly, as well as people with respiratory disorders such as asthma, are particularly susceptible to health effects caused by PM. Scientists now believe that there is no "threshold," or safe level, for exposure to PM. Particulate matter is not limited to urban areas. Exposure to PM in Canada is widespread, and it remains a problem in every region of Canada all year round. A correlation has been established between high levels of airborne PM and increases in emergency room visits, hospital admissions and deaths.  PM is also an effective delivery mechanism for other toxic air pollutants, which attach themselves to particulate matter that floats in the air. These toxics are then delivered into the lungs, where they can be absorbed into the blood and tissue. Environmental Impacts of PM<10 The effects of PM on materials have been investigated for metals, wood, stone, painted surfaces, electronics and fabrics. The deposition of PM on these materials may cause soiling and discoloration, thus reducing their aesthetic appeal. Exposure to PM may also cause physical and chemical degradation of materials through the action of acidic particles. Particulate matter is also associated with reduced visibility with poor air quality. The presence of particles in the air reduces the distance at which we can see the colour, clarity, and contrast of far away objects because the particles in the atmosphere scatter and absorb light. The most obvious effect of particulate deposition on vegetation is the physical smothering of the leaf surface. This will reduce light transmission to the plant in turn causing a decrease in photosynthesis. Particle composition may cause both direct chemical effects on the plant and indirect effects through impacts on the soil environment. Particle accumulation on the leaf surface may increase the plant's susceptibility to disease.  Canada's Action On May 27, 2000, based on scientific recommendations, Canada's Minister of Environment and Minister of Health announced their intention to declare particulate matter less than or equal to 10 microns (PM_<10) toxic under the Canadian Environmental Protection Act (CEPA 1999). Under CEPA, key industrial sectors are required to set emission reduction targets and timetables to meet those targets.  The Government of Canada, provincial and territorial governments agreed in June 2000 to ratify the Canada-wide Standard for PM_2.5. All jurisdictions have committed to meet this new Standard by year 2010 or sooner. A wide range of actions to reduce emissions from vehicles, products and industry will have to be implemented to meet the Standard. Some of these, like vehicles and fuels will be carried out by the Government of Canada. Others, such as emission reductions from certain existing industrial sources, will be undertaken by provinces and territories. Emission reductions from a limited number of major industrial sectors that are of interest nationally will be achieved through joint efforts by the provinces/territories and the Government of Canada.

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Last updated: 2002-11-25 Last reviewed: 2002-08-26

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