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Home > The ABC of air > Pollutants
Particulate Matter (PM10 et 2,5)

The sources of particles

The sources of particles or “aerosols” are numerous and varied, due to the many different processes by which they are formed. Methods of classification of these sources are based on origin (anthropic, marine, biogenic, volcanic) or on the processes of formation. A distinction can be made between two types of aerosols: 

  • primary aerosols: those emitted directly into the atmosphere in solid or liquid form. The majority of particles related to human activity stem from the combustion of fuel (for production and transformation of energy, heating for individual homes principally using biomass, etc.), automobile transport (exhaust, wear, friction, etc.) as well as agricultural activities (cultivation of the soil, etc.) and very diverse industrial activities (foundries, glass factories, grain silos, incineration, quarry operations, public works, etc.) Their size and composition are highly variable.  
  • secondary aerosols: directly formed in the atmosphere by processes of transformation of gases into particles, for example sulphates (transformation of sulphur dioxide) and nitrates. The majority of organic particles are secondary aerosols. 

PM10 is the category of particles whose diameter is less than 10 micrometres (inhalable fraction). PM2.5, or very fine particles having a diameter of less than 2.5 micrometres, travel more deeply into the respiratory system.

Health effects

Depending on their size distribution, the particles penetrate more or less deeply into the bronchial passages. The smallest particles may, at relatively low concentrations, irritate the lower respiratory tract and impair lung function as a whole. Some particles have mutagenic and carcinogenic properties. 

Effects on the environment

The soiling of buildings and monuments is the the most obvious environmental damage

The reference standards


Information and recommendation threshold for sensitive individuals Alert warning threshold for the general population
50 µg/m3 taken as a rolling 24 hours average 80 µg/m3 taken as a rolling 24 hours average

In Upper Normandy, these thresholds are governed by  the Prefectural by-law of 20th April 2018

Air quality objective
30 µg/m3 annual  average
Limit values for the protection of human health
daily average  annual average
50 µg/m3 daily average not to be exceeded more than 35 days per year 40 µg/m3


Target value
25 µg/m3
Limit values 2012 for the protection of human health
27 µg/m3 annual  average