What are fine particles?

The term “fine particle” refers to an aggregate of polluting chemical compounds created during combustion, friction or chemical reactions. Forest fires, volcanic eruptions, and desert dust: fine particles can occur naturally. But most fine particles are generated by human activity. How? Mainly from road traffic (exhaust gases and abrasion caused by brakes on tyres and the road), home heating, and industrial and agricultural emissions.

Variable compositions

What makes up a fine particle? There is no specific formula. Soot, sulphur particles (SOx), nitrogen oxides (NOx), hydrocarbons (HC), and heavy metals such as copper, iron, barium, and zinc can all form fine particles. Their content, shape and size differs depending on what type of pollution has generated them.

PM1, PM2.5 and PM10

What is the difference between PM1, PM2.5 and PM10 fine particles? Fine particles are ranked by size. Ultrafine particles are called PM1 and have a diameter of less than 1 micron. The diameters of PM2.5 and PM10 are less then 2.5 and 10 microns respectively. To give an idea of scale, PM2.5 is the size of a red blood cell while PM10 is the size of a bacterium. The smaller a fine particle, the more dangerous it is, because it can penetrate deep inside the body. Its shape is also to be considered: the rounder it is, the more easily it forms clusters with other pollutants. And that creates a very toxic mix.

A sly threat

The answer to the question “What is a fine particle?” could also be that it is a dangerous pollutant that is everywhere, and invisible to the naked eye. Whether liquid or solid, fine particles create air pollution in heavily populated areas. When carried on the wind, they can also travel long distances and remain suspended in the atmosphere. As a result, according to the World Health Organization (WHO), nine out of ten citizens are exposed to air laden with fine particles. The larger particles that are not airborne are drained in runoff water and end up in rivers and oceans. 

A threat to health

What impact do fine particles have? They pose a major issue for public health. Because breathing in particles means exposing your body to oxidative stress* and a host of respiratory (asthma, bronchitis), cardiovascular (arrhythmia, heart attack, thrombosis) and neurodegenerative (Alzheimer’s and Parkinson’s) diseases. They exacerbate existing illnesses, weaken vulnerable populations (children, the elderly, pregnant women) and put lives at risk. 17% of deathsfollowing lung cancer can be attributed to air pollution and fine particles. The WHO believes that this pollution is responsible for 4.2 million premature deaths per year globally. This impact is the same as that of tobacco consumption, but causes three times as many deaths as those that happen as a result of consuming alcohol and unsanitary water. Shocking.


Oxidative stress occurs when a cell can no longer manage the excessive presence of toxic molecules, mainly from cellular respiration and free radicals. They can damage cells and DNA.

Discover more questions

Electric vehicles help fight against global warming and reduce the air pollution that causes 307,000 premature deaths in Europe every year. But electric vehicles are not a miracle solution. They require a lot of energy to produce, charging them may need large amounts of fossil fuels (depending on the source of the electricity used) and – like petrol or diesel cars – they emit fine friction particles.
Fine particles are harmful to human health. They can cause or exacerbate breathing and lung difficulties, cardiovascular diseases and even neurodegenerative diseases. This health risk can be limited if car owners would fit particle filters to their vehicles. Installed on exhaust or braking systems, particle filters are anti-pollution devices which capture fine particles emitted by vehicles. There are two types of particle filters: installations designed to capture particles from exhaust fumes generated by diesel and petrol vehicles, and those designed to recover fine particles from brake wear.
Stinging eyes, breathlessness, a cough that won’t budge: air pollution – especially when it’s cause by fine particles – is irritating, but can also be the cause of serious diseases. It even puts lives in danger: in France, air pollution cuts life expectancy by two years. And in New Delhi, this figure leaps to 10 years. In terms of deaths on a global scale, air pollution is just as dangerous as smoking, and even more serious than alcohol and unclean water (there are three times as many air pollution-related deaths) and HIV (six times more). Who is most at risk? People suffering from respiratory and cardiac disorders, diabetes, infants, seniors and pregnant women.