What is Particulate Matter?

Particulate matter pollution (PM), also known as particle pollution or soot, is the term for a mixture of solid particles and liquid droplets found in the air. Particulate matter is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small, they can only be detected using an electron microscope.

Where Does it Come From?

Particulate matter can 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, smokestacks or fires. Others form in complicated reactions in the atmosphere between chemicals such as sulfur 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 particulate matter in the country. Because particulate matter can form in so many different ways, it can be elevated at any time during the year. However, in West Michigan, levels are typically highest during the summer and winter. 


The size of particles is directly linked to their potential for causing health problems. The EPA is concerned about particles that are 10 micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. EPA groups particulate matter into two categories:

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  • "Inhalable coarse particles," such as those found near roadways and dusty industries, are larger than 2.5 micrometers and smaller than 10 micrometers in diameter.

  • "Fine particles," such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries and automobiles react in the air. A single hair from your head is about 70 micrometers in diameter—which means a hair is 30 times larger than the largest fine particle.

The EPA regulates inhalable particles (PM2.5 and PM10). Particles larger than 10 micrometers (sand and large dust) are not regulated by the EPA, and this is why the forecasts provided by the WMCAC (through the Michigan Department of Environment, Great Lakes, and Energy) only include fine particulate matter (PM2.5) at this time. 

What Negative Effects are Associated with Particulate Matter Pollution?

Health Effects
Particulate matter contains microscopic solids or liquid droplets that are so small that they can get deep into the lungs and cause serious health problems. Small particles less than 10 micrometers in diameter pose the greatest problems because they can get deep into your lungs, and some may even get into your bloodstream.

Numerous scientific studies have linked particulate matter exposure to a variety of problems, including:

  • increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing

  • 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 particulate matter exposure. However, even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particulate matter.

Environmental Effects

Visibility reduction
Fine particles (PM2.5) are the major cause of reduced visibility (haze) in parts of the United States, including many of our treasured national parks and wilderness areas. 

Environmental damage
Particles can be carried over long distances by wind and then settle on ground or water.  The effects of this settling include: making lakes and streams acidic, changing the nutrient balance in coastal waters and large river basins, depleting the nutrients in soil, damaging sensitive forests and farm crops, and affecting the diversity of ecosystems.

Aesthetic damage
Particulate matter can stain and damage stone and other materials, including culturally important objects such as statues and monuments.

Interested in learning more:

US EPA: https://www.epa.gov/pm-pollution