Particulate matter explained icon

What is particulate matter?

June 22, 2016

Whether we see it or not, there’s plenty of not-air in our air. A big portion of those respirable substances are known as particulate pollution or particulate matter, and many of those particles come from sources we encounter — or create — every day.

Here’s all you need to know about the microscopic particles, where they come from, and how to manage them.

What is particulate matter?

At the most basic level, particulate matter is an umbrella term that describes a mixture of liquids and solids, from both human and natural origins, suspended in the atmosphere.

Are there different types of particulate matter?

Scientists classify particulate matter by size. They call particulate matter “coarse” or “PM10” if the particle has a diameter between 2.5 micrometers and 10 micrometers. (For reference, a human hair is between 50 and 70 micrometers thick.) Dust and smoke are visible examples of PM10, but more than 90 percent of particulate matter isn’t visible to the naked eye.

We call these substances “fine particulate matter” or “PM2.5.” The particles have a diameter of less than 2.5 micrometers, which means they can only be seen underneath a microscope. Particles from smokeless heating fuels and road dust are two examples.

 

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Where do PM2.5 and PM10 come from?

The U.S. Environmental Protection Agency (EPA) divides particulate matter sources into two categories: primary and secondary. Primary particles come directly from a source, such as agriculture and construction sites. Secondary particles form when gases from burning fuels react with sunlight and water vapor. Primary particles tend to be coarse while secondary particles are fine.

What can particulate matter do to my health?

Quite a lot, unfortunately. Specifically, PM2.5 substances can travel deep into our lungs and reach the bloodstream. Numerous studies have linked particulate matter exposure to decreased lung function, respiratory symptoms like coughing and labored breathing, and even reduced life expectancy.

How much particulate matter is too much?

Though researchers haven’t been able to identify a threshold at which particulate matter begins to affect health, the EPA still has limits for public health. For PM10 and PM2.5, the 24-hour average cannot exceed 150 and 12 micrograms per cubic meter of air, respectively. If it does, local and state officials issue warnings to stay indoors, filter air, and drink water to dislodge harmful particles from our airways.

Is particulate matter also bad for the environment?

Cities, clogged with cars and peppered with construction sites and factories, typically have higher particulate matter concentrations than rural areas do. When these particles react with sunlight, they form haze, which can remain suspended in the air and travel for hundreds of miles. For instance, particle pollution in Los Angeles can migrate from Los Angeles all the way to The Grand Canyon.

Particulate matter also alters the nutrient and chemical balances of soil and water when it settles. Rivers, for instance, can become acidic when exposed to particle pollution. In soil, particle pollution depletes nutrient supplies, which damages sensitive crops and forests.

How can I reduce particulate matter in my home?

Particle pollution occurs year-round, so keep an eye on daily measurements and avoid spending a lot of time outside when the Air Quality Index tells us that levels are “unhealthy.” Hunkering down indoors isn’t an absolute solution, though: Domestic activities like cooking, smoking, and lighting candles all produce PM2.5. No, you’re probably not going to stop cooking, so investing in a little extra ventilation and filtration can help manage the particles floating around your home.

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