Particulate Matter (PM<10)

PM consists of microscopic material in the air. It is made of fine dust produced by friction and grinding processes of soil, rocks, or metals, smoke from burning and other combustion processes, and is the product of chemical reactions between reactive gases in the atmosphere. Once formed, particles can increase in size through additional reactions.

Particles capable of being inhaled by humans are divided into two size ranges. They are also produced by human activities, such as construction, demolition, mining, road dust and tire wear. "Coarse" particles cover the range from 2.5 to 10 micrometers in diameter, and tend to be generated naturally by sea salt spray, wind and wave erosion, volcanic dust, windblown soil and pollen.

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. 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.

In contrast, "fine" particles less than 2.5 micrometers in size, (1/20th the width of a human hair), can be inhaled deep into the lungs reaching areas where the cells replenish the blood with oxygen. PM_2.5

Health Effects of PM<10

Numerous studies have linked PM<10 to aggravated cardiac and respiratory (heart and lung) diseases such as asthma, bronchitis and emphysema and to various forms of heart disease.

There is also evidence that hospitalization and deaths from these diseases increase along with increasing outdoor levels of PM. A correlation has been established between high levels of airborne PM<10 and increases in emergency room visits, hospital admissions and deaths.

Although concentrations of PM<10 have long been associated with adverse health effects, recent studies show that these particles are responsible for premature deaths from lung and heart disease related causes, and that Canadians are being affected at current concentrations across the country. Scientists now believe that there is no "threshold," or safe level, for exposure to PM<10.

Children and the elderly, and people with respiratory disorders such as asthma, are particularly susceptible to health effects caused by PM<10.

The effect is even more acute with smaller PM_2.5 particles. Health effects include breathing and respiratory symptoms, irritation, inflammation and damage to the lungs, and premature death.

Particulate matter is not limited to urban areas. Exposure to PM<10 in Canada is widespread, and it remains a problem in every region of Canada all year round.

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 in a limited way for metals, wood, stone, painted surfaces, electronics and fabrics. The deposition of PM on these materials may cause soiling and discolourization, thus reducing their aesthetic appeal. Exposure to PM also causes physical and chemical degradation of materials, through the action of acidic particles for example.

Most people, when questioned, would readily associate reduced visibility with poor air quality. What may not be known is that it is primarily the fine particles in the air that are responsible for the reduced visibility. 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 also be relevant, causing both direct chemical effects on the plant and indirect effects through impacts on the soil environment. Particle accumulation on the leaf surface may also increase the plant's susceptibility to disease.

Canada's Action

Based on scientific recommendations, the Ministers of Environment and Health announced Particulate Matter less than or equal to 10 microns (PM<10) as toxic under the new Canadian Environmental Protection Act (CEPA 1999) on May 27, 2000. Under the new CEPA, a concrete timeframe to bring a toxic substance under effective control is required. Key industrial sectors will be required to set emission reduction targets and timetables to meet those targets. The Government of Canada's action on PM<10 is one of a number of immediate and long term actions on clean air. Official notification was published in the Canada Gazette for a 60 day public comment period.

Additionally, the Government of Canada, provincial and territorial governments agreed to ratify the Canada-wide Standard for PM_2.5