What you should know about particulate matter (PM10 and PM2.5):

Particle pollution (also referred to as particulate matter or PM) is the term for a mixture of solid particles and liquid droplets suspended in the air. Particulate matter may originate from the sea (sea salt), from risen dust, from fires or from fuel combustion. Some particles, such as dust, dirt, soot or smoke, are large or dark enough to be seen with the naked eye; most of them are too small and remain invisible, however. Particle pollution includes "inhalable coarse particles," with diameters smaller than 10 micrometers and "fine particles," with diameters smaller than 2.5 micrometers.

Health impact of particulate matter:

Particle pollution – especially fine particles – contains microscopic solids or liquid droplets that are so small that they can penetrate deep into the lungs and cause serious health problems. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including:

• Increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing, for example
• Decreased lung function
• Aggravated asthma
• Development of chronic bronchitis
• Irregular heartbeat
• Nonfatal heart attacks
• Premature death in people with heart or lung disease.

People with heart or lung diseases, children and older adults are the most likely to be affected by particle pollution exposure. However, even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particle pollution.

How you should adjust your behavior during a pollution episode:

It is important to limit your exposure to (fine) particles -- especially if you may be susceptible. Try to stay indoors if possible.

Background information:

Particles (PM10 and PM2.5) come in many sizes and shapes and can be made up of hundreds of different chemicals. Some particles, known as primary particles, are emitted directly from a source, such as construction sites, unpaved roads, fields or fires. Others form in complicated reactions in the atmosphere from chemicals such as sulphur dioxides and nitrogen oxides that are emitted from power plants, industries and automobiles. These particles, known as secondary particles, make up most of the fine particle pollution in the country.