What is Particulate Matter? PM2.5, PM10, Health Effects, Pollution Sources

When we speak of airborne contaminants, one of the first things that come to mind is pollution. We know that air pollution is one of the leading causes of death and illnesses worldwide. That is why we take measures to lessen our exposure by installing air purifiers and wearing masks and respirators.

What makes air pollution even more dangerous is that particulate matter is one of its major components. It is also referred to as PM or particle pollution. It is mostly invisible to the eye and is present indoors and outdoors. That is why avoiding exposure to it is impossible. Add the fact that it has plenty of sources and is present indoors and outdoors.

You should keep reading because we will discuss its different types, specifically PM2.5 and PM10. We’ll cover the different health effects and the sources of particle pollution.


The Environmental Protection Agency is known as one of the best sources of environmental concerns. It includes the topic we’ll cover in this article. Their website has covered the basics and other essential information explaining why it should be a cause for concern.

However, they did not detail the topic. Their presentation may also be too technical for some.

This guide is our answer to that problem, as we will delve deeper into the basics not covered by the EPA website. We’ll also look at other sources they link to, but in a way that is easier to understand.

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What is it?

Before anything else, we need first to understand what particulate matter is.

If you think that this involves dust, you are partly correct. However, dust is just one of the many components that comprise it.

The EPA defines it as combinations of airborne solid and liquid particles and may include the following:

  • dust
  • pollen
  • smoke
  • allergens
  • acids
  • metals
  • soot
  • soil particles
  • sulfates
  • organic chemicals
  • nitrates
  • and other organic and inorganic particles

It can come in different sizes and can be easily seen or require a microscope.

It may sound harmless to you, but what complicates it is that many of these particles are considered hazardous. Most of them are microscopic. It is easily ingestible through inhalation or swallowing. And when this happens, it can lead to various health effects. The most dangerous is death. Direct contact with particulates has also been proven to cause skin problems.

Note that it consists of different particles, determining their chemical composition and properties. This means it may contain safe compounds, while others may have extremely hazardous ones. This is one of the reasons why some types are more harmful than others.

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Due to the numerous substances that comprise it, it should be no surprise that numerous sources exist. But generally speaking, there are two sources in the air: primary and secondary.

A primary source directly produces or emits it on its own, most of them produced due to anthropogenic or human activity. These activities include:

  • Industrial and agricultural processes
  • Construction and demolition work
  • Fuel combustion uses wood, biofuel, and fossil fuel, including those coming from fireplaces and wood stoves.
  • Disturbance of roads and fields, particularly those that are unpaved.

Wildfires and organic matter resuspension are considered primary sources but naturally occurring or non-anthropogenic. This means they do not require human activity to produce the particulates.

Mineral dust is produced through human and natural activities, among the most common components. This dust is present in arid and semiarid areas. It can become airborne with the slightest breeze or when disturbed during construction or agricultural work.

On the other hand, a secondary source releases compounds or substances into the air to react to the gases present in the atmosphere. It creates particulate matter. A secondary source will produce the compound or chemical that will react to the atmosphere to create the PM. It will not create particulate matter itself. Most of it is produced via a secondary source.

VOCs are the most common compounds and natural gaseous precursors that produce PMs after oxidation. Ammonia, sulfur oxide, and nitrogen oxide are also on the list. These usually come from emissions of motor vehicles and wood smoke, and even gaseous vegetative emissions.

Note that the source in the air will greatly affect the composition, especially in terms of its volatility and size. It is one of the main reasons PMs have varying environmental and health impacts.

It may come in different sizes, depending on its components. They only have two size classifications, which are PM2.5 and PM10.

Particulate Matter 2.5

Also referred to as fine particulate matter, PM2.5 is named because it only measures 2.5 micrometers in diameter. It can even be less than that. To put it into perspective, its size is only 3% the diameter of a strand of human hair. It requires the use of an electron microscope to be detected.

It can be produced by either a primary or secondary source. Still, most of its particles come from a secondary source. Most of this material is produced from the chemical reaction between the atmosphere and fuel combustion. It’s especially in motor vehicles. Primary sources of PM2.5 include sea spray and wildfires, on the other hand.

In the US, it is produced mostly by the following sources:

  • Fires
  • Road dust
  • Generation of electricity
  • Industrial activities and processes
  • Combustion of wood in residential homes
  • Use of non-road equipment
  • Waste disposal
  • Miscellaneous
  • Combustion of fossil fuel
  • On-road vehicles
  • Use of solvent
  • Fertilizer and livestock

Fine particulate matter is found both indoors and outdoors. The concentration levels tend to be higher outdoors, especially near roads. Its size also makes it easier for PM2.5 to be transported to different places. It can easily be blown away by the wind and remain airborne for several days to even several weeks.

Aside from various health effects, it also has environmental impacts. It can cause plant damage and poor visibility, among other things. The fog or mist you see is a good indicator of high particle pollution levels.

Particulate Matter 10

In contrast, PM10 has a larger diameter than PM2.5. It is also called inhalable coarse particles. They have a diameter not exceeding 10 micrometers but are bigger than 2.5 micrometers. Because of its larger size, some of it may be seen even without a microscope.

This coarse particulate matter is also known as respirable particulate matter, which it gets from its size. It is produced through primary and secondary sources and is abundant on roadsides. This particle pollution is prevalent in combustion conditions and natural sources like pollen and resuspension. It’s also present in the biological matter and sea salt.

It is known to pose harm not just to your health and the environment but to a lesser degree than PM2.5. Its larger size allows it to be transported in shorter distances and remain airborne for shorter periods. It may be as quick as several minutes to a few hours.

Is it More Harmful than PM2.5?

Now that you are aware of their differences, you may be wondering if PM10 is more harmful than PM2.5 because of their size difference. Before answering that question, you need to understand what makes them hazardous.

We mentioned that air pollution is a global problem. We mentioned that particulate matter abundant in polluted air is seen as the major culprit for these health risks. This is because it is too small to be blocked by our body’s natural defenses, and they often contain hazardous material. This applies to both PM10 and PM2.5, as their size allows them to be easily ingested by anyone.

However, size plays a role in this case. The smaller one is more harmful.

They can enter your body without you noticing. The larger type tends to be trapped in the upper respiratory tract area. It’s specifically in the nose and throat. This is because the cilia found along the respiratory tract can block PM10, preventing it from penetrating deeper into your body. The trapped particulate matter may even be expelled through sneezing and coughing. It can get trapped inside mucus that is then digested harmlessly or ejected through the mouth.

On the other hand, the smaller PM2.5 can go deeper than that and reach the lungs. There, it can cause more severe health effects. Certain PM2.5 can even go into the areas of the respiratory system where the lungs and the bloodstream meet and the exchange of gases occurs. It allows the soluble component to enter the bloodstream and wreak havoc on other organs. The insoluble component remains in the lungs’ alveoli and can trigger inflammation when it accumulates.

Its composition will also play a crucial role in its health effects. But ultimately, the size will be the biggest factor in determining how harmful it can be. The smaller the size, the more dangerous it is.

Health Effects

Did you know that the health effects are not limited to respiratory issues? The health risks go beyond that, especially if it contains metals. It is often the case for PM2.5.

The respiratory system is known to be one of the most at risk when you are exposed, especially the lungs. Still, it can also affect your cardiovascular and reproductive systems and cause other health issues.

Respiratory System

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The particulates are most often ingested through inhalation. It is not surprising that the respiratory system is the most commonly affected. These effects are experienced by both young and old alike, and older adults are considered the most at risk for it.

The health effects involving the respiratory system due to particulate matter exposure include the following:

  • Greater risk of acquiring respiratory illnesses, including lung cancer and pneumonia. It can also cause chronic lung disease and bronchitis.
  • Increased vulnerability to pathogens, both bacterial and viral. These can cause various diseases.
  • There are aggravated symptoms or reactions for those with pre-existing respiratory conditions. They are things such as asthma and COPD.
  • It can cause breathing difficulties due to airway blockage, causing death.
  • Recurrent coughs
  • Irritation of the throat and lungs can increase their permeability and lead to lung injury.
  • More frequent asthma attacks
  • Inflamed lung tissue
  • Decreased lung function
  • It can cause a reduction in lung growth and development for children and even teenagers. It compromises lung function for the rest of their lives.
  • It includes a higher risk of hospitalization or death due to lung disease in older adults.
  • Breathing difficulties
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Cardiovascular System

Exposure to particulate matter will also affect your cardiovascular system, particularly your heart and blood vessels. However, this may also be an effect of respiratory issues due to exposure. This means that it can cause respiratory problems, which can then cause cardiovascular issues.

Some of the known effects on the cardiovascular system are:

  • Blood chemistry changes
  • Arrhythmia or irregular heartbeat, especially for those with heart disease
  • Congestive heart failure
  • Arterial plaque buildup can cause hardening and inflammation, triggering a stroke or heart attack.
  • It includes a higher risk of experiencing heart attacks or an increased frequency for those who already have a history.
  • Greater possibility of cardiovascular mortality
  • It causes weakening of the heart.
  • Development of vascular diseases, including coronary heart disease, with long-term exposure
  • Abnormal blood clotting
  • It may cause irregular heart muscle activity caused by an irritated autonomic nervous system.
  • High blood pressure
  • Worsened symptoms of heart disease

Reproductive System

To some extent, your reproductive system may also be affected by exposure. The risk is even higher for pregnant women. It can affect both them and their unborn child, especially when exposed to it during the first month.

Health risks include:

  • Infertility
  • Menarche delays
  • Menstrual problems
  • Miscarriage
  • Stillbirth
  • Low birth weight of infants
  • Birth defects
  • Complications to the pregnancy, such as GDM or gestational diabetes mellitus and preeclampsia

Other Health Issues

You may also develop other health issues, such as:

  • Eye irritation, including conjunctivitis
  • Stuffy or running nose, post-nasal drip, or constant sneezing due to nasal irritation
  • Irritation of the throat can cause sore or dry throat and coughing.
  • Chest pains
  • Headache
  • Increased risk of acquiring diabetes and hyperglycemia, or insulin resistance for those who are already diabetic
  • Genotoxicity or damage to DNA that can lead to cancer
  • Dizziness
  • Increased possibility of getting cancer, as particulates may contain known carcinogens.
  • Lethargy
  • Fibrosis or scarring of the liver that can lead to cirrhosis, as well as liver damage and dysfunction
  • Faster aging of the brain, including neurodegeneration
  • Poor attention span or hyperactivity
  • Learning difficulties. It can lead to an IQ decrease in children.
  • Symptoms of mental and behavioral disorders, including those of anxiety and depression

The size and length of exposure will determine the kind and severity of health effects you may acquire. While PM2.5 is more harmful, this does not mean that PM10 is completely safe. You must still limit your exposure to both. Long-term exposures will be the most harmful to anyone, and exposure that contains toxic components.

Death is the most severe health effect, even with short-term exposure. Long-term exposure may not immediately show symptoms. It can affect your quality of life and even significantly reduce your lifespan.

Will a HEPA Filter Remove it?

The microscopic size of PM2.5 may make it seem like protection is impossible. Still, you can remove certain types using a suitable HEPA filter. This kind of filter, also referred to as a High-Efficiency Particulate Arrestor, typically screens particles up to 0.3 microns small. Certain HEPA filters can remove particles measuring 0.1 microns, successfully filtering out PM2.5.

A respirator with an N95 rating and HEPA filter is also effective in filtering it out. Both reusable and disposable types can be used for this. What matters more is a respirator’s capability of creating a tight seal. Proper sealing ensures that no particles can pass through gaps between your face and the respirator. This means surgical and single-strap paper masks should not be used even if they have an N95 rating. Respirators with HEPA filters are even more effective in doing so.


You may be familiar with air quality monitoring devices that measure indoor and outdoor quality. These devices can determine the pollution level present in that area. They are generally not capable of detecting the presence and the levels present.

If you want to determine concentration levels indoors or outdoors, you must get a sensor.

A sensor and a typical air quality monitor generally have the same function. It is to detect the concentration levels of airborne contaminants. Air quality monitors focus on general pollutants, with only specialized ones capable of identifying the type of pollutants present. On the other hand, these sensors focus on determining the levels present. Most quality monitors are not capable of doing this.

These sensors typically use optical means to determine the concentration levels present. It will pass through a light source, often a laser. The detection chamber allows light to be absorbed or scattered. When this happens, the sensor can determine the number and concentration levels of the particulates present.

Sensors can either be standalone or connected to air quality monitors and HVAC systems to increase their functionality.

How to Reduce It

With the abundance of sources, it is a given that its presence may exceed acceptable levels now and then. With the numerous environmental and health risks involving fine and coarse sources, you know it should be addressed when it happens.

But how can you reduce the levels present? Here are some ways to ensure that they will fall within safe levels:

  • Avoid smoking, especially indoors where there is poor air circulation. This also includes lighting candles and incense.
  • Lessen the use of heating devices that involve combustion or burning of wood. Ensure proper ventilation and use well-seasoned wood when doing so.
  • Stop open burning practices, even if it involves biodegradable household trash like leaves and wood.
  • Decrease black carbon production by limiting the use of vehicles equipped with older engines, especially diesel-powered ones.
  • Immediately address wildfires and prevent new ones from starting.
  • Install appropriate air purifiers with HEPA filters and sensors to quickly address high levels before it reaches dangerous levels.
  • Drive less and use mass transport or carpool instead. If possible, travel by foot or any other means with zero-emission.
  • Reduce your usage of household products that may produce it upon use.
  • Observe regular car maintenance, as this will also help reduce PM production.
  • Go green using energy-efficient appliances and install environment-friendly energy sources, like solar panels.
  • Open windows and ventilation systems if the indoor levels are higher than normal.
  • Remove sources of asbestos and other toxic airborne sources that are known to be present in old homes. Use safe practices when doing so to prevent them from spreading around.
  • If you live near roads or industrial facilities, make home improvements to prevent it from getting inside your home. They are among the major sources.
  • Keep your home clean and use a HEPA vacuum to ensure that dangerous substances are removed. Use the right shop vac when doing projects that release it into the air.
  • When idling your car for longer periods, do it outside your attached garage and away from doors and windows.
  • Limit your use of gas-powered gardening equipment.

Contrary to what you might think, reducing its presence does not require doing anything fancy or using sophisticated equipment. These simple methods can already greatly decrease the levels in a short time. It can prevent them from reaching levels that can immediately harm anyone.

Various government agencies started keeping track of air quality trends over the years. They particularly started paying close attention to concentrations levels of various substances. This is a good indicator of the severity of air pollution. PM10 used to be the only particulate matter monitoring. After discovering the more harmful effects of PM2.5, they started monitoring it alongside PM10.

Because of their effects, those who crafted the Clean Air Act of 1970 included provisions that involve particulate matter. This Act has been instrumental in dramatically improving air quality in the country. It includes appendices and related policies resulting from it. It has been proven by the steadily declining number of illnesses and premature deaths due to exposure.

Monitoring its presence in the air has made it possible for agencies to predict high particle pollution days. They do so based on historical data, which is surprisingly accurate. Some of the trends they discovered include:

  • Higher PM2.5 concentrations in the eastern half of the US from July to September. At that point, fine particulate matter is higher in the western half from October to November.
  • PM10 concentrations are now nearly 50% lower compared to the levels in the 1980s. PM2.5 concentrations are now lower by 40% on average compared to the levels in the 1990s when they started keeping track.
  • Concentrations of coarse and fine particulate matter have generally declined over the years, with some small increases for short periods. They are observed to be steadily increasing since 2015, with climate change seen as one of the major factors.
  • The majority of countries have also shown a remarkable decline in concentration levels over the years, especially with PM2.5.

Monitoring air quality trends is necessary to decrease acquiring health issues. It’s because they’re due to prolonged or high-level exposure. You know that this is easier said than done, but not completely impossible.

You can check the air quality index or AQI via EPA’s AirNow. However, the agency combines PM and ozone levels to develop the index. There is no way of knowing the actual levels.

By this time, you are now aware of the essentials of the topic. You are also more conscious of its impact on you and the environment. You know how you can take measures to keep it within acceptable levels.

Because of all these, you avoid being part of the statistics of injuries or fatalities caused by exposure.


What level of PM2.5 is unhealthy?

PM 2.5 is considered very unhealthy for all groups of people when it is at 55.5- 150.4 μg/m3.

At this point, the AQI above 151 is considered very dangerous. Prolonged exposure to this particle can cause an increased risk of cardiovascular disease and heart attacks.

What are small dust particles called?

These are called particulate matter. PM2.5 is considered the worst because it is too tiny to trace and can enter the body. Prolonged exposure to them can lead to an increased risk of disease.

What are dust particles made out of?

Dust particles are everything from skin cells, volcanic eruptions, soil particles, pollen, and sea aerosols. Traffic and industrial emissions also cause particle dust to emerge.

Why are dust particles harmful?

Since these are so tiny that they can easily be inhaled, they can cause multiple diseases and infections. These include fibrosis and lung scarring. It can also be pulmonary disease and heart attacks, to mention a few.

Why can’t we see dust particles?

Dust particles are too tiny to be seen unless they are grouped. For example, aerosols are about 0.3 µm. About 40 million of them are present in the outdoor air you breathe. Some dust like smoke from vehicles and fires is visible due to its high concentration. After integrating into the air, they become less visible and prone to inhalation.

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