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 deaths and illnesses worldwide, that is why we take measures to lessen our exposure to it, such as by installing air purifiers and wearing masks and respirators.

What makes air pollution even more dangerous is the fact that one of its major components is particulate matter, 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 both indoors and outdoors.

Whether you have heard of it or not, you should keep reading because we will discuss its different types, specifically PM2.5 and PM10, the different health effects, and the sources of particle pollution.


The Environmental Protection Agency, or EPA, is known as one of the best sources for environmental concerns, including the topic we’ll cover in this article. On their website, they have covered the basics and other essential information explaining why, in high amounts, it should be a cause for concern.

However, they did not go into much detail about the topic, and their presentation may be too technical for some.

This guide is our answer to that problem, as we will go delve deeper into the basics not covered by the EPA website and other sources they link to, but in a way that is easier to understand by all.

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What is it?

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

If you are thinking that this is 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 solid and liquid particles that are airborne and may include dust, pollen, smoke, allergens, acids, metals, soot, soil particles, sulphates, organic chemicals, nitrates, and other organic and inorganic particles. It can come in different sizes and can either be easily seen or will require the use of a microscope to do so.

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

Take note that it consists of different particles, not just one, and these particles present will determine its 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 come as no surprise that there are numerous sources for it. But generally speaking, there two sources in the air, which are primary and secondary sources.

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

  • Industrial and Agricultural Processes
  • Construction and Demolition Work
  • Fuel Combustion using Wood, Biofuel, and Fossil Fuel, Including Those Coming from Fireplaces and Wood Stoves
  • Disturbance of Roads and Fields, Particularly Those That are Unpaved

Sea sprays, wildfires, and organic matter resuspension are also considered primary sources, but they are naturally-occurring or non-anthropogenic. This means they do not require human activity for the particulates to be produced.

Mineral dust, which is among the most common components in it, is produced through both human and natural activities. This dust is present in areas that are arid and semiarid, and can become airborne with the slightest breeze or when disturbed while doing construction or agricultural work.

On the other hand, a secondary source releases compounds or substances into the air that will react to the gases present in the atmosphere, which will then create the particulate matter. Simply put, 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 actually produced via a secondary source.

Among the most common compounds and natural gaseous precursors that produce PMs after oxidation are VOCs or volatile organic compounds, ammonia, sulfur oxide, and nitrogen oxide. These usually come from emissions of motor vehicles and wood-smoke, and even gaseous vegetative emissions.

Take note that the source in the air will greatly affect the composition, especially in terms of their volatility and size, and this is one of the main reasons why PMs have varying environmental and health impacts.

It may come in different sizes, depending on its components, but 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 as such because it only measures 2.5 micrometers in diameter, or even less than that. To put it into perspective, the size of it is only 3% the diameter of a strand of human hair and requires the use of an electron microscope to be detected.

It can be produced by either a primary or secondary source, but 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, especially that of motor vehicles. Primary sources of PM2.5, on the other hand, include sea spray and wildfires.

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, but 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, as it can easily be blown away by the wind and remain airborne for several days to even several weeks.

Aside from various health effects, which we will discuss in the succeeding section, it also has environmental impacts. It can cause plant damage, soiling, corrosion, and poor visibility, among others. In fact, the fog or mist you see is a good indicator of high levels of this particle pollution.

Particulate Matter 10

In contrast, PM10 has a larger diameter than PM2.5. Also called inhalable coarse particles, they have a diameter not exceeding 10 micrometers, but is bigger than 2.5 micrometers. And because of its larger size, some of it may be seen even without the aid of a microscope, especially in large amounts.

This coarse particulate matter, also known as respirable particulate matter, is likewise produced through both primary and secondary sources, and are abundant in roadsides. This particle pollution is also prevalent in conditions where combustion occurs, as well as in natural sources like pollen, resuspension of biological matter, and sea salt.

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

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. But before we answer that question, you need to understand what exactly makes them hazardous.

Earlier, we mentioned that air pollution is a worldwide problem, and that particulate matter that is 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 really plays a role in this case, as the smaller one is seen as more harmful.

While they can both enter your body without you noticing, the larger type tends to be trapped on the upper respiratory tract area, 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, coughing, or end up 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 where 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, allowing the soluble component to enter the bloodstream and wreak havoc to 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? In fact, the health risks it poses goes beyond that, especially if it contains metals, which is often the case for PM2.5.

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

Respiratory System

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Because the particulates are most often ingested through inhalation, it is not surprising that the respiratory system is the most commonly affected. These effects are experience by both young and old alike, with children, those who already have lung or heart disease, and older adults considered as 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, pneumonia, chronic lung disease, bronchitis, and asthma (with long-term exposure)
  • Increased vulnerability to pathogens, both bacterial and viral, that can cause various diseases
  • Aggravated symptoms or reactions for those who already have pre-existing respiratory conditions, such as asthma and COPD (with short-term exposure)
  • May cause breathing difficulties due to airway blockage, causing death
  • Recurrent coughs
  • Irritation of the throat and lungs, which can increase its permeability and lead to lung injury
  • More frequent asthma attacks
  • Inflamed lung tissue
  • Decreased lung function
  • Reduction in lung growth and development for children and even teenagers, compromising lung function for the rest of their lives
  • 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 is 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 to the cardiovascular system are:

  • Blood chemistry changes
  • Arrhythmia or irregular heartbeat, especially for those with heart disease
  • Congestive heart failure
  • Buildup of arterial plaque that can cause hardening and inflammation, which can trigger stroke or heart attack
  • Higher risk of experiencing heart attacks, or an increase frequency for those who already have history
  • Greater possibility of cardiovascular mortality
  • Weakening of the heart
  • Development of vascular diseases, including coronary heart disease (with long-term exposure)
  • Abnormal blood clotting
  • Irregular activity of the heart muscle 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, as it can affect both them and their unborn child, especially when they get 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 that 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, which can lead to IQ decrease in children
  • Symptoms of mental and behavioral disorders, including those of anxiety and depression

The size, length of exposure, and the component will determine the kind and severity of health effects that you may acquire. While PM2.5 is known to be 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, as well as exposure that contain toxic components.

Death is the most severe health effect it can have, even with short-term exposure. Long-term exposure may not immediately show symptoms, but 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, but you can remove certain types with the use of a suitable HEPA filter. This kind of filter, also referred to as a High Efficiency Particulate Arrestor, is known to typically screen particles that are up to 0.3 microns small. Certain HEPA filters are capable of removing particles measuring 0.1 microns, and this can successfully filter 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, as what matters more is a respirator’s capability of creating a tight seal. A proper sealing ensures that no oartuckes can pass through any gaps present 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.

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You may be familiar with air quality monitoring devices that measure the quality indoors and outdoors. While these devices can determine the level of pollution 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, outdoors, or both, you must get a sensor.

A sensor and a typical air quality monitor have generally the same function, which is to detect the concentration levels of airborne contaminants. Air quality monitors focus on general levels of 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, which most quality monitors are not capable of.

These sensors typically make use of optical means to determine the number of and concentration levels present. It will pass through a light source, often a laser, in the detection chamber, and they will allow light to be either 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, purifiers, and HVAC systems to increase its functionality.

How to Reduce It

With the abundance of sources, both natural and manmade, it is a given that its presence may exceed acceptable levels every now and then. And with the numerous environmental and health risks involving both fine and coarse sources, you know that it should be immediately 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, bike, or any other means that have 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 by 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, lead, and other toxic airborne sources that are known to be present in old homes, and observing safe practices when doing so to prevent them from spreading around
  • If you live near roads, fields, or industrial facilities, which are among the major sources, make home improvements to prevent it from getting inside your home
  • Keep your home clean and use 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 any 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 and prevent it from reaching levels that can immediately pose harm to anyone.

Air Quality Trends

Various government agencies started keeping track of air quality trends over the years, particularly paying close attention to concentrations levels of various substances, as this is a good indicator of the severity of air pollution. PM10 used to be the only particulate matter monitored but with the discovery of 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, including addendums and related policies resulting from it, has been instrumental in dramatically improving air quality in the country, which has been proven with 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 accurately predict high particle pollution days based on historical data. Some of the trends they discovered include:

  • Higher PM2.5 concentrations in the eastern half of the US from July to September, while 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, while PM2.5 concentrations are now lower by 40% on average compared to the levels in the 1990s when they started keeping track
  • Concentrations of both coarse and fine particulate matter have generally been declining over the years, with some small increases for short periods. However, they are observed to be steadily increasing since 2015, with climate change seen as one of the major factors
  • Worldwide, majority of countries have also shown remarkable decline in concentration levels over the years, especially with PM2.5

Monitoring air quality trends is necessary to decrease the chances of acquiring health issues due to prolonged or high-level exposure. By now, you know that this is easier said than done, but not completely impossible.

You can check the air quality index, or AQI, in real-time via EPA’s AirNow to know how polluted the air is in various parts of the country, as well as be aware of AQI forecasts. However, the agency combines PM and ozone levels to come up with the index, so 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 to you and the environment and know how you can take measures to keep it within acceptable levels.

And because of all these, you avoid being part of the statistics of injuries or fatalities caused by exposure to it.

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