All about particulate matter (PM)

Notorious for its abilities to cause harm to our health, particulate matter (also known as PM) has been making headlines as more and more studies are released showing its dangers. What is particulate matter, what dangers does it pose, and how can we protect ourselves? Read on to learn more.

A bird perched on a bridge barely visible due to polluted air

What is particulate matter?

Particulate matter, also called particulate pollution or PM, is a complex mixture of liquid and solid particles found in our breathing air. It comes from various sources and can be found in different sizes. Today, we recognise three sizes, or categories, of PM which include:

  • PM10 – Coarse particles
  • PM2.5 – Fine particles
  • PM0.1 – Ultrafine particles

Note: ‘PM’ refers to ‘particulate matter’ and the number following refers to the particle’s aerodynamic diameter1.


PM10 is the largest size of particulate matter and refers to all particles of 10 μm in diameter or smaller (including PM2.5 and PM0.1); however, when we refer to PM10, we usually refer to particles with a diameter of between 10 μm and 2.5 μm. Some examples of PM10 particles may include mould spores, dust, some smoke, some bacteria, and some airborne viral particles2.

These particles, although considered to be ‘coarse’, are still incredibly small: 10 of them side-by-side could fit in the width of one human hair!1 PM10 can come from a multitude of sources both anthropogenic and natural. The map below provides some of the main sources of PM10 by region of the world:

A map showing the main sources of PM10 pollution around the world

3 Urban Air Quality: European Environment Agency.

As seen above, the main sources of PM10 throughout the world as a whole tend to be road transport, industrial sources, burning of residential fuel (typically wood and natural gas), and natural sources. Some more specific examples of man-made sources of PM10 may include slash-and-burn agriculture, dust from construction sites and open lands, and power plants that burn fossil fuels. Some natural sources may include pollen, dust storms (a significant contributor to PM10 in regions like the Middle East as seen above), and wildfires3.

Although finer particles tend to get more attention from a health perspective, PM10 still poses dangers to our health and air quality. PM10 particles are still small enough to be able to enter our respiratory systems which can have a severe impact on both our respiratory and cardiovascular health, and they also may trigger asthma attacks and allergies in sensitive individuals.


PM2.5 is perhaps the most infamous type of particle matter due to its association with negative effects on human health. These particles measure 2.5 μm or smaller in diameter, and emissions come mostly from the burning of fuels (petrol, oil, diesel, and wood are some of the biggest offenders) but can also pollute our breathing air through natural sources like wildfires.

A diagram showing the difference in sizes between PM10, human hair, and PM2.5

4 California Air Resources Board. Inhalable Particulate Matter and Health (PM2.5 and PM10).

PM2.5 particles are particularly dangerous because, due to their small size, they can quickly and easily gain access to the body through the respiratory system and make their way to other parts of the body and organs like the heart, the brain, and the bloodstream. PM2.5 can have a range of health effects in both the short-term and long-term:

  • Short-term (exposure of up to 24 hours): premature mortality, increased admissions to hospital for heart and lung conditions, bronchitis (acute and chronic), asthma attacks, difficulties breathing, and worsening of existing respiratory conditions like asthma and COPD.
  • Long-term (exposure of several months to years): premature death for people with lung or heart conditions, stunted lung function and growth in children, and increased risk of lung cancer4,5.

PM2.5 can cause negative health effects for anyone and everyone; nevertheless, people who are the most at risk are those with existing lung or heart diseases, elderly individuals, children, and pregnant women. Specifically, one Children’s Health Study initiated by the California Air Resources Board found that children who live in areas with higher levels of PM2.5 had slower lung growth and smaller lungs at age 18 compared to children living in areas with lower levels of PM2.54. It can also lead to premature death. In the UK, Ella Debrah was a 9-year-old girl who was the first person to die with air pollution as the official cause of death. Read more about her story here.

All types of PM, including PM2.5, have a negative impact on the environment and contribute to climate change. PM2.5 especially reduces visibility by having an impact on the way that atmospheric light is absorbed and redistributed4.

PM2.5 is currently known as the most harmful type of particulate matter in regards to human and environmental health.


PM0.1 is the smallest known type of particulate matter and consists of particles with an aerodynamic diameter of 0.1 μm or smaller. These particles are categorised as ‘ultrafine’, and its sources are similar to those of PM2.5.

Because less is known about it than both PM10 and PM2.5, PM0.1 is a rising area of research, but early studies show that it may be more dangerous than PM2.5 causing both enhanced cardiovascular toxicity and having higher potential for oxidative stress2. These particles also make up about 83% of indoor air pollutants according to a recent German study6.

Should I be worried about PM in my indoor spaces?

Despite the fact that PM has mostly outdoor sources, this does not mean that it cannot pose problems indoors. In fact, indoor spaces are usually 5-7 times more polluted than outdoor spaces due to the fact that pollutants, whether their source is indoors or whether they make their way in from outdoors, become trapped. Ventilation is crucial in preventing indoor air from becoming stale and circulating out polluted air that has found its way in, but this also means that outdoor air pollution can make its way in through doors, windows, and other ‘leaks’.

There are also numerous indoor activities that can lead to the production of PM. Biological pollutants like allergens (pollen, dust and dust mites, mould spores) and activities like smoking, cooking, cleaning, using air fresheners, and burning wood, candles, or incense can all produce PM in an indoor space and cause problems for your health4. Combustion in general is a significant source of PM (gas cooking, wood stoves, fireplaces, etc).

A candle burning

How can we protect ourselves from the dangers of PM?

The recommended actions to take involve avoiding physical activity during periods of peak air pollution or near sources of pollution like busy roads where emissions are higher. We can also avoid performing strenuous physical activity near sources of pollution like busy roads where emissions are higher.

But what do we do to protect ourselves from particulate matter that has entered our homes or workplaces? Some of the best ways are to ventilate your spaces regularly to keep air circulating (it is recommended to avoid this step during periods of peak pollution), keep your space clean using natural products, and avoid burning wood, gas, candles, or incense. If some of these steps seem difficult to maintain, an excellent solution is to invest in an air purifier.

Keep your health in check with Eoleaf

Eoleaf’s high-quality air purifiers take fear of PM out of the equation. Our air purifiers use 8 different filtration technologies to remove all types of PM from your indoor air from PM10 down all the way down to PM0.1 and even PM0.01. Our air purifiers also remove chemical contaminants like VOCs and airborne germs including viruses and bacteria, helping you breathe fresher, pollutant-free air.



1 Smith, D. (2020, January 3). PM10: How do coarse particles (particulate matter) affect air quality? Kaiterra. Retrieved April 25, 2023, from

2 Smith, D. (2020, October 9). The three types of particulate matter: All about PM10, PM2.5, and PM0.1. Kaiterra. Retrieved April 25, 2023, from

3 Urban Air Quality. European Environment Agency. (2022, June 16). Retrieved April 25, 2023, from 

4 California Air Resources Board. Inhalable Particulate Matter and Health (PM2.5 and PM10) | California Air Resources Board. (2023). Retrieved April 25, 2023, from

5 International Agency for Research on Cancer, World Health Organization. (2016). Outdoor Air Pollution. (Vol. 109). Retrieved April 25, 2023.

6 Zhao, J., Birmili, W., Wehner, B., Daniels, A., Weinhold, K., Wang, L., Merkel, M., Kecorius, S., Tuch, T., Franck, U., Hussein, T., & Wiedensohler, A. (2020). Particle mass concentrations and number size distributions in 40 homes in Germany: Indoor-to-outdoor relationships, diurnal and seasonal variation. Aerosol and Air Quality Research, 20(3).

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