Fine particles (PM_2,5) are solid entities with a diameter less than 2,5 µm. Like any particle, they are made up of a mixture of different chemical compounds. In Île-de-France, they mainly come from wood heating, road traffic and construction site activities or are formed by chemical reactions from precursor gases present in the atmosphere. Fine particles are harmful to respiratory and cardiovascular health.

What effects on health and the environment?

Fine particles are harmful to human health. Reducing the concentrations of fine particles below the thresholds recommended by the WHO would make it possible to avoid around 6 premature deaths each year in Île-de-France. (in 2019, compared to around 10 premature deaths in 000). Chronic exposure to these particles increases the risk of contracting respiratory and cardiovascular diseases, including lung cancer and stroke. The effects on health depend in particular on the size of the particles: coarse particles, with a diameter between 2010 and 2,5 µm, have effects on respiratory health, while fine particles, with a diameter less than 10 µm , also impact cardiovascular health, increase the risk of neurodegenerative diseases and low birth weight.

For more information, see: Effects of air pollution on health.

Concerning environmental impacts, particles cause blackening and crusting on building facades.

For more information, see: Effects of air pollution on buildings.

Particles also have a variable impact on climate change depending on their chemical composition: some aggravate climate change, while others mitigate it, in particular via their interactions with cloud formation.

For more information, see: Air pollution and climate change.

What are the sources?

The sources of fine particles are multiple and influence their chemical composition and size.

In Ile-de-France, wood heating emits more than half of fine particles, followed by road transport, particularly diesel and gasoline vehicles, as well as construction site activities.

The distribution of particle emissions according to their size varies according to the sectors of activity:

• Road traffic and heating with wood, oil and gas generate more fine and ultrafine particles (PM_2.5 and PM_0,1), linked respectively to combustion in engines, abrasion of brakes and tires and the combustion of wood, fuel oil and gas for heating;
• The construction site and quarry sectors generate more large particles (PM₁₀), by the nature of their activities (construction, deconstruction, use of special equipment, etc.);
• The manufacturing industry sector often mixes combustion and various processes, and produces PM₁₀ and PM_2.5.

If the emissions from certain activities vary little from one month to the next (construction sites, industry, rail and river transport, airport platforms, waste processing, etc.), others have a more marked temporality, such as heating and the production of heat and electricity which is much greater in winter, and that from agriculture in spring and autumn.

The fine particles present in the ambient air may have been emitted directly into the air, but some of them can also be formed by chemical combination of polluting gases (we then speak of primary particles in the first case, and of secondary particles in the second). They can also come from transport over long distances, or from the resuspension of dust deposited on the ground. Thus, the contribution of emitting activities to pollutant emissions does not reflect that which will be present in the ambient air (around a third of the particles can be secondary).

For more information see the inventory of air pollutant emissions in Île-de-France.
 

What levels are breathed in Île-de-France?

Concerning chronic pollution, the regulatory thresholds for fine particles are respected throughout Île-de-France. Despite an improving trend, all Ile-de-France residents are exposed to concentrations of fine particles higher than WHO recommendations for air quality..

The highest concentrations of fine particles are found near the main regional roads and Parisian roads. The levels there can be up to twice higher than those recorded moving away from these axes.

The average levels of particles observed far from the main roads within the Paris metropolitan area remain generally homogeneous. A slight decrease between the dense heart of the agglomeration and the outskirts of Île-de-France is observed.

There is no regulatory threshold triggering the transition to a pollution episode for fine particles.

For more information, see the latest assessment of air quality in Île-de-France et Air quality regulations in France.