Fine atmospheric particulate matter, which is the major pollutant in cities, is made up of a mixture of solid and liquid particles of organic and inorganic substances suspended in the air.
They have a diameter between 0.1 and approximately 100μm (1 μm is one thousandth of a millimetre), as explained on the websites of the various regional environmental protection agencies which report to ISPRA.
These particles are called "fine dust" and identify in particular: - Pm10 or particles with an aerodynamic diameter of less than 10 μm capable of penetrating the upper part of the respiratory system;
the daily limit value is 50μg (micrograms per cubic meter, not to be exceeded more than 35 times in a year); - Pm2.5 refers to particles with a diameter of less than 2.5 μm capable of reaching the lungs and secondary bronchi.
The World Health Organization recommends an average annual value of 20 µg/cubic meter for PM10 and 10 µg/cubic meter for PM2.5 as a threshold for the protection of human health.
These fine dusts are made up of a mixture of carbon, fibres, metals (iron, copper, lead, nickel, cadmium), nitrates, sulphates, organic compounds (hydrocarbons, organic acids), inert material (soil fragments, spores, pollen) and particles. liquid.
Among the causes of emissions attributable to human activity there are some industrial activities (foundries, cement factories, construction sites, mines), combustion processes relating to thermoelectric power plants, incinerators, heating and vehicle traffic (in particular diesel engines) .
In urban areas, particulate matter can also originate from the wear of asphalt, tyres, brakes and clutches.
Various epidemiological studies on the effects of atmospheric particle pollution have highlighted associations between the mass concentrations of PM10 and an increase in both mortality and hospital admissions for cardiac and respiratory diseases in the general population.
The subjects considered most exposed to these effects are in particular the elderly, children, people with chronic cardiopulmonary diseases and those suffering from influenza or asthma.
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