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What’s in the Air: Understanding Particulate Matter & Why It Should Be on Your Radar

Updated: Sep 14, 2022

Here at the Group Against Smog and Pollution (GASP), we get it: Science isn’t in everybody’s wheelhouse. We understand that when it comes to air quality issues, there’s a LOT of terminology and acronyms to digest.

But we also realize that in order to protect yourself, your family- and yes, even your pets – having a basic understanding of what’s in the air, how it got there, and how it could affect your well-being is crucial.

We want to arm you with all the need-to-know information on the most prevalent types of air pollution: carbon monoxide, lead, ground-level ozone, nitrogen dioxide, particulate matter, and sulfur dioxide. Together, they are known as Criteria Pollutants and because they are known to cause harm to the environment and human health, the EPA has set science-based guidelines for how much of each one is permitted in the air. 

These limits are known as National Ambient Air Quality Standards (NAAQS), and they were designed to prohibit pollution concentrations that could adversely affect people’s health.  Locally, these pollutants are monitored by the Allegheny County Health Department Air Quality Program.  

One of the most prevalent and dangerous of those six pollutants is particulate matter, a type of air pollution that’s prevalent in our region. Have you seen recent headlines about the Mon Valley making the list of places with the worst air quality in the country?

The area made those lists because of spiked levels of particulate matter.

What is Particulate Matter?

Particulate matter pollution is referred to as PM. It is a complex mix of air-borne particles and droplets of liquid  made up of:

  1. Acids like nitrates and sulfates

  2. Ammonium

  3. Water

  4. Black carbon

  5. Organic chemicals

  6. Metals

  7. And soil matter 

The EPA breaks down particle pollution into two main groups: Coarse particles and fine particles.

Coarse particle pollution is more commonly referred to with an acronym – PM10. Why? Because it refers to all particle pollution that is less than 10 microns in size. How big is a micron? To give some perspective, a single strand of human hair is the thickness of about 50 microns. This type of particle matter pollution, because of its larger size, can get stuck in nose hairs, cilia, and secretions in the throat. PM10 is irritating to the nose, throat, lungs, and eyes. 

Common types of coarse particle pollution include dust, pollen, smoke, and dirt.

Fine particulate matter is more commonly referred to as PM2.5. You can probably guess why: It refers to all particulate matter pollution that is less than 2.5 microns. Fine particulate matter pollution is more harmful to human health because it’s smaller and more able to infiltrate the body through the nose, mouth, and skin. This means they can travel deep into the lungs and even into the bloodstream.

PM2.5 is referred to as primary if it is directly emitted into the air and as secondary if it’s created as a result of chemical reactions from gases mixing in the atmosphere.

There are myriad sources of PM2.5, but the most common include:

  1. Exhaust from cars and trucks

  2. Exhaust from diesel engines (including construction and other machinery)

  3. Open burning (i.e. wildfires, fireplaces, woodstoves)

  4. Cooking

  5. Dust from roads and construction on them

  6. Agricultural operations

  7. Combustion of coal and oil

  8. Emissions from industrial processes such as oil refining, steel making, as well as the production of paper and the refinery of oil

Why You Need To Be Concerned About PM2.5 Exposure

Studies have long shown that exposure to particulate matter pollution has significant health consequences and the size of the particle matters. Larger particles are linked to inflammation of the respiratory system, bronchitis, asthma, allergies, coughing, reduced lung capacity.  

PM2.5 is linked to heart attacks, strokes, arrhythmias, and lung cancers, while ultrafine particles are associated with brain damage and organ cancers.

It should be noted: Some particle pollution might be more harmful than others – it largely depends on composition and oxidative potential, but it’s important to remember that there is really no safe level of PM2.5 pollution.

Many people are familiar with particulate matter’s harmful effects on the lungs and heart, but did you know particulate matter pollution has been shown to increase the risk of miscarriage.

Exposure to PM2.5 is also linked to everything from baldness to dementia to mental illness. 

According to the EPA, exposure to particulate matter hits children, the elderly and those with pre-existing conditions harder than most. For these folks, PM2.5 has been shown to cause:

  1. Increased hospital admissions

  2. Increased emergency room visits

  3. Absences from work and/or school

  4. A restriction in participation in outdoor activities

Standards for Particulate Matter Pollution

By this point, you might be saying to yourself something like, “Sounds like pretty scary stuff. What’s considered safe exposure?”

So glad you asked. 

National air-quality standards for particulate matter were first created in 1971 but were not significantly revised until 1987. That’s when the EPA placed the regulatory spotlight on so-called inhalable particles smaller than or equal to 10 microns. Then in 1997, the EPA established standards for fine particulate matter.

Here’s where things get technical: The annual standard for PM2.5 was set at 15 micrograms per cubic meter, which is based on a three-year average of annual mean of PM2.5 concentrations. The 24-hour standard was set at 65 micrograms per cubic meter, which is based on the three-year average of the annual 98th percentile concentrations.

It should be noted: These primary standards are set to protect public health. Secondary standards are set to protect public welfare (think protection against decreased visibility due to particulate matter pollution, as well as damage to crops, vegetation, structures, and even animals).

But back to the rules: Those 1997 regulations also revised standards for PM10, limiting them to 50 micrograms per cubic meter based on the annual average, and 150 micrograms per cubic meter based on a 24-hour average.

However, in 2006, the regulations were again revisited and rewritten in the wake of numerous studies shedding light on ill health effects of PM. The standards for PM2.5 were lowered to 35 micrograms per cubic meter for the 24-hour standard. As for PM10 standards? While the EPA retained the 24-hour standard, it tossed out the annual standards, citing a lack of evidence linking long-term pollution of course particles to health issues.

The regulations were updated again in 2013, when the EPA again revised the annual standard for PM2.5, reducing the annual standard from 15 to 12 micrograms per cubic meter. 

Protecting Yourself from Particulate Matter Pollution

Fortunately, there are some steps you can take to reduce your exposure to high levels of PM2.5. The first step is being aware of when PM2.5 levels are elevated. 

If you live in Allegheny County, you can track air quality data, including levels of particulate matter, by visiting its website and clicking on the Air Quality Program icon. You can also sign up for Allegheny Alerts, which delivers important messages about air quality and other health issues via text, call, or email.

Live outside of Allegheny County? Bookmark the EPA’s Air Data webpage to monitor criteria pollutants like PM2.5. You might also consider getting yourself a PurpleAir monitor.

That way, the next time you are aware of high PM2.5 levels you can limit exposure by:

  1. Limiting time outdoors if possible – PM levels are generally lower indoors

  2. Going easy on yourself if you cannot limit your time outdoors. If you were slated to take a run, go for a walk instead. Need to take the dog out? Try a shorter route.

  3. Avoid traffic-choked streets and congested roadways, where levels of emissions from cars and trucks are greater.

Please know that you don’t have to wait for a poor air quality day to reduce your exposure to particulate matter and other kinds of pollution. An easy way to improve your indoor air quality is to purchase an air filtration system designed to trap particle pollution. 

The kind of air filtration system you use does matter, so make your selection carefully. To help with that endeavor the EPA created a “Guide to Clean Air and Filters in the Home,” which is available on the agency’s website.

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