With the terms atmospheric particulate matter or particle material we refer to those suspended particles present in the air that we breathe every day and which are usually called fine powders or dust. The abbreviation PM derives from the initials of the two English words Particulate Matter (translated into Italian with the word material particulate matter), while the number 10 indicates the size of the particle diameter which can vary up to 10 microns or micrometers (1 micron = 1 millionth of a meter). PM10 is also called thoracic fraction as, passing through the nose, it is able to reach the throat and trachea (located in the first tract of the respiratory system). The smallest particles (less than 2.5 microns in diameter) called PM2.5 or respirable fractionInstead, they can go even deeper into the lungs. There are also particles with very small diameters, called ultrafine particulate matter (PUF), which can penetrate to the pulmonary alveoli.
PM10, considered a good indicator of air quality, is made up of a set of solid particles of different nature, chemical composition and size (between 10 and 2.5 microns); it can be completely different from city to city based on the development of the urban center and the presence of industries, the fuels used and the climate.Numerous chemicals, such as polycyclic aromatic hydrocarbons (PAHs) and metals (such as lead, nickel, cadmium, arsenic, vanadium, chromium), can adhere to the surface of fine powders determining health effects of the exposed population.
PM10 is present in the air as a result of:
- natural events, such as erosion, caused by wind, of rocks and other surfaces, the formation of marine aerosols, dust storms, fires or the release of gas from volcanoes
- human activities that use fossil fuels or biomass, as in artisanal and industrial processes (for example in thermoelectric power plants, refineries, in the chemical, cement and steel industries), but also in daily activities such as cooking, heating, transporting goods or using motor vehicles. PM10 is in fact one of the main components of the exhaust gases of motor vehicles, industrial plants and port emissions
The atmospheric particulate remains in the air for quite a long time and can, therefore, be transported over large distances. Atmospheric phenomena such as wind and rain help to dilute and lower the PM10 levels in the air, causing it to fall back and deposit in the air. soil.
The atmospheric particulate has a different toxicity depending on its origin. For example, that derived from human activities is generally more toxic than that caused by natural phenomena.
PM10 causes various health effects including many disorders related to the respiratory system. The International Agency for Research on Cancer (IARC) has classified air pollution (of which atmospheric particulate matter is an indicator) in Group 1, that is, among the carcinogenic substances for humans.
Sources of exposure
The exposure of the population to PM10 occurs mainly through the inhalation of:
- air present indoors (often referred to with the English word indoor) after:
- domestic combustion (for example, tobacco smoke, electronic cigarettes, fireplaces and stoves for heating and for preparing food, incense sticks, candles)
- infiltration of external air through doors and windows
- release by building materials and furnishing elements
- lifting of dust linked to various domestic activities
- poor state of maintenance of the air conditioning systems
- deodorants and perfume diffusers
- air present in outdoor environments (often referred to with the English word outdoor) after:
- exhaust gases produced by means of transport with petrol and diesel engines (cars, buses, trucks, mopeds, etc.)
- raising dust from road surfaces due to tire wear and use of brakes
- industrial emissions (from thermoelectric plants, refineries, cement factories, steel mills, chemical industries, quarries, transfer and storage of raw materials), activities carried out in ports and shipyards
- combustion deriving from domestic heating systems and chimneys for the use of biomass and diesel
Effects on health
The effects on human health of the dust present in the air, called PM10 in relation to the size of the particles of which it is composed, they mainly depend on its quantity (or concentration) as well as on the nature of its components. In fact, depending on their diameter, they will be deposited more or less deep in the respiratory system. The type and severity of the effects determined on health is also influenced by the chemical substances, organic and inorganic, present on the surface of the particles. Soluble substances, for example, can be absorbed by the organism at the point where they are deposited, causing local disturbances.
More serious effects, on the other hand, with disturbances (symptoms) and changes in respiratory function (bronchitis, asthma which may also require hospitalization) have been observed after exposure (albeit limited to one or two days) to high levels of PM10 and PM2.5 (particles with a diameter of less than 2.5 microns). The World Health Organization (WHO) has linked the spread of these effects to an increase (of 10 micrograms per cubic meter) in the average concentration of PM10 and PM2.5 calculated over the 24 hour period.
When PM10 contains high concentrations of metals, acute inflammations of the respiratory tract, asthma attacks, and alterations in the functioning of the cardiovascular system are frequent.
Prolonged exposure over time even to low levels of PM10 and PM2.5 is associated with an increase in respiratory disorders such as cough and phlegm, asthma, decreased lung capacity, decreased respiratory function and chronic bronchitis together with effects on the cardiovascular system. Exposure to the smallest dust (PM2.5) has been associated with an increase in mortality from respiratory diseases and a greater risk of respiratory tract cancer. Tumors have also been linked to the presence of carcinogenic substances attached to the surface of the particles (such as polycyclic aromatic hydrocarbons-PAH in the case of soot) which, through PM2.5 can reach the deepest part of the lungs, where they are absorbed by the "body.
In sensitive people such as asthmatics, individuals with lung disease, heart disease and in the elderly it is reasonable to expect a worsening of their conditions and disorders. Children up to 12 years of age, having a double breathing frequency, introduce larger volumes of air into the lungs than adults and may be at greater risk for some respiratory effects such as bronchial asthma attacks.
According to the World Health Organization, for particulates it is not possible to define a limit value below which no health effects occur in the population: for this reason the concentration of PM10 and PM2.5 in the air should be kept at However, the new WHO guidelines on air quality report that reducing PM10 to 20 micrograms per cubic meter could lead to a 15% reduction in mortality by reducing the incidence of diseases due to respiratory infections, heart disease and lung cancer. For PM2.5, the WHO proposes, to protect health, guide values for the exposure of the population equal to 10 micrograms per cubic meter on an annual basis.
Prevention, control and useful advice
Limiting the exposure of the entire population to PM10 as much as possible can be considered the main preventive action, especially for those children and the elderly who live in cities where the highest concentrations of atmospheric particulate matter are recorded.
To decrease the PM10 levels present in indoor environments (indoor) it might be useful:
- ventilate the houses preferably opening the windows further away from the busiest roads or, in any case, during the hours when traffic is limited. In the event that the environment is equipped with ventilation systems or air conditioners, it is advisable to avoid placing air vents or vents in correspondence with the busiest roads and it is important to have expert personnel carry out a correct maintenance and cleaning of filters
- avoid staying too long and to sleep in environments where fireplaces, stoves, products such as incense sticks, deodorants, perfume diffusers have been lit or used, or where tobacco smoke and electronic cigarettes have been used
- carry out regular maintenance, always by expert personnel, of the heating systems that must be equipped with external ventilation channels
- use a hood with outside drain when cooking
- do not smoke indoors
- maintain a "relative humidity in homes of 35-40%
Since the traffic of motor vehicles outdoors (cars, buses, trucks) is one of the most important causes of the presence of PM10 in the air, to reduce PM10 levels, every citizen can actively contribute through correct and healthy alternatives such as:
- go by foot, or, for short journeys and on less busy roads, use a bicycle
- make more use of public transport
House heating systems are another important source of PM10 emissions during the winter period. In this case, the quantity of atmospheric particulate that diffuses into the air depends on the characteristics of the fuel (solid, liquid, gaseous) and on the state of maintenance of the chimney, stove or boiler. The increasing use of biomass for domestic heating it has unfortunately made an important contribution to PM10 concentrations.
In Italy, the concentration levels of particulate in outdoor environments are regularly controlled by fixed control units that allow the measurement of air quality. Legislative decree no. 155 of 2010 establishes that the daily limit value corresponds to 50 micrograms per cubic meter ( value that in a year must not be exceeded for more than 35 days) while the annual average must not be greater than 40 micrograms per cubic meter.
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