Emissions and air quality

Human activities result in the release into the atmosphere of various substances, both in the gaseous state or in the form of aerosol (dispersion of solid or liquid particles in the air). Many of these substances are also originate from natural sources.

The definition of pollutant refers to any substance present in the atmosphere for a sufficient time and at a concentration such as to negatively affect the human health or the ecosystem.

Some pollutants (such as carbon monoxide and benzene) tend to persist in the form in which they were emitted into the atmosphere, even if in time the will undergo chemical transformations (primary pollutants). Other pollutants can be involved, in the short time, in chemical reactions which can lead, under certain conditions, to the formation of new pollutants in the atmosphere (secondary pollutants). This applies, for example, to nitrogen dioxide and volatile organic compounds that contribute to the production of the tropospheric ozone.

In urban areas the density of emissions (amount of pollutants emitted per unit area) is very high and related to the population density and the traffic flows. In several cases urban areas include high density emission districts such as industrial and port areas. Therefore generally the concentration of pollutants is higher in urban areas than in adjacent suburban and rural areas, except for the tropospheric ozone, due to its particular dynamics.

The differences between the urban areas of the same country are related to differences in the emission load, weather conditions and topography, that can encourage or discourage the accumulation of air pollutants.

In order to establish proper environmental policies on air quality and monitor their effectiveness, it is necessary to identify and understand the nature of air pollutants and collect emission data. ISPRA, as the National Reference Centre of the European Environment Agency (EEA), is in charge of the compilation of the national air emission inventory, that is currently used to verify the compliance with the environmental commitments that Italy has taken at international level. The compilation of the emission inventory is a complex process that requires the participation of many actors, which provide the basic data related to the different emission sources (traffic, agriculture, livestock, heating, etc.); these data are used as input data of estimation modelsto produce atmospheric emission estimates.

ISPRA carries out every five years the provincial breakdown of the national inventory data, in order to provide a uniform representation of the main emission sources in the Italian provinces, with results comparable to each other as generated using the same methodology. As far as more specific local areas, such us municipalities, local inventories can undoubtedly provide more detailed data, which will be however difficult to compare as often obtained with different methods.

Estimates at municipal level are made through the disaggregation of the provincial data, with the aim to provide a uniform representation of the main emission sources in the Italian cities and to have comparable data generated using the same methodology. This makes it possible to evaluate the main emission sources of each pollutant relating to the Italian urban areas.

Alongside the emission estimates, ISPRA populates each year indicators of air quality in urban areas, with the data on the atmospheric concentration of specific pollutants obtained by the monitoring stations of the regional networks distributed throughout the country. The pollutants considered are the following: atmospheric particulate matter (PM10 and PM2.5), nitrogen dioxide, benzene, tropospheric ozone, benzo(a)pyrene and some metals. The indicators are compared with the limit values and the target values provided by law for the human health protection. The joint analysis of the emission estimates, of the air quality data and of their trend allows to monitor the progress in combating air pollution and the distance from the objectives set by the regulations.

If the limit values of SO2, NO2, CO, benzene, Pb, PM10 and PM2.5 are exceeded, regions and autonomous provinces are obliged to adopt a Plan for the improvement of the air quality, providing the necessary measures to act on the emission sources. Such plans and measures should be adopted in the areas affected by the excess and must act, in accordance with criteria of efficiency and effectiveness, where the emission sources affecting the area are located. It’s worth noting that the affected area and the area where the emission sources are located may not coincide.

Air quality plans should contain such information as, localisation of excess pollution, general information (e.g. type of zone, useful climatic data, relevant data on topography), nature and assessment of pollution (concentrations observed before and after the implementation of the measures), origin of pollution (list of the main emission sources responsible for pollution, total quantity of emissions from these sources), analysis of the situation (details of those factors responsible for the exceedance (e.g. transport)), details of the adopted measures (Directive 2008/50/EC, annex XV).


The air we breathe daily in our cities can affect our health. Indeed there are many epidemiological studies that have correlated outdoor air pollution with the increase of respiratory, cardio-circulatory and allergic diseases, especially for the most vulnerable groups such as children and elder. The analysis of the population exposed to air pollutants is important for epidemiological evaluations and monitoring the effectiveness of policies adopted for air quality and human health protection.

Since many years, using methods acknowledged at European level, ISPRA builds indicators that quantify the population exposed to air pollutants such as PM10 and Ozone. With the same methodology were also lately developed the indicator on urban population exposure to PM2.5, NO2 and Benzo(a)Pyrene  (BaP). Exposure to PM, NO2 and BaP are assessed using the mean annual concentrations at urban background stations weighted on the city's population. Ozone exposure is assessed using the indicator called SOMO35, a measure of accumulated annual ozone concentrations used as an indicator of health hazards[1] as safe for human health or with the indicator of days exceeding the limit value for the protection of human health.

Regional monitoring networks, coordinated in a national network (POLLnet), are the main source of information on pollen in the air, which also contribute to the air quality assessment. The data reported for the first time in the ninth edition of the report, in lack of a specific legislation establishing attention levels, must be interpreted as first description of the phenomenon.

The effects of air pollution are then investigated not only in relation to the population, but also in relation to the condition of the historical and artistic heritage. The interaction between the airborne substances and the materials that constitute the cultural heritage usually damages the works of art both visually and from a structural standpoint. Within the agreement drawn up by ISPRA and IsCR (Higher Institute for Conservation and Restoration), and with the collaboration of ARPA Lazio, a monitoring campaign was realized aimed at studying the blackening and erosion / corrosion phenomena of some of the materials (marble, glass, copper) typical of the cultural heritage of the city of Rome.


[1] WHO-Europe, 2008. Health risks of ozone from long-range transboundary air pollution ( a report by the Joint  WHO/Convention Task  Force  on the Health Aspects of Air Pollution)