Panel 1
Daniela Romano
The indicator illustrates the national emission trends of tropospheric ozone precursors—namely nitrogen oxides (NOx) and non-methane volatile organic compounds (NMVOCs)—disaggregated by emission source sector. A significant overall decline is observed between 1990 and 2022, amounting to -71% for NOx and -58% for NMVOCs, primarily driven by substantial reductions in emissions from the transport sector.
Emission estimates are conducted in accordance with the methodology outlined in the European Environment Agency’s EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019. The issue of tropospheric ozone is of significant concern both in urban areas—where acute pollution episodes often occur—and in rural environments, where impacts on crops are observed. Emissions of nitrogen oxides (NOx) and non-methane volatile organic compounds (NMVOCs), which are precursors to tropospheric ozone, also have transboundary relevance due to long-range atmospheric transport phenomena.
Ozone formation results from photochemical reactions that typically occur under meteorological conditions associated with the summer season. Ozone is a powerful oxidant and exerts harmful effects on human health, ecosystems, and cultural heritage assets. The main sources of these pollutants are road transport and other combustion processes, while solvent use is also a major contributor to NMVOC emissions.
Assessing the pressures exerted by tropospheric ozone precursors and their trends over time is essential for monitoring compliance with national and international emission reduction targets, as established under Legislative Decree No. 171/2004, the Gothenburg Protocol, and the NEC Directive (Directive (EU) 2016/2284).
Pollution (CLRTAP) and amended in 2012, targets the reduction of acidification, eutrophication, and ground-level ozone formation. The European Community acceded to the Protocol via Council Decision 2003/507/EC.
Directive (EU) 2015/2193, transposed into Italian legislation by Legislative Decree No. 183/2017, applies to medium combustion plants and sets emission limit values (ELVs) for sulphur dioxide (SO₂), nitrogen oxides (NOx), and particulate matter (PM), with the aim of mitigating their environmental and health impacts.
Directive (EU) 2016/2284 on the reduction of national emissions of certain atmospheric pollutants—transposed into Italian law through Legislative Decree No. 81/2018—sets binding national reduction commitments compared to 2005 levels. These apply for two periods: 2020–2029 and from 2030 onward. Specifically, for nitrogen oxides (NOx), reduction targets are 40% and 65%, respectively; for non-methane volatile organic compounds (NMVOCs), the corresponding reduction targets are 35% and 46%.
Panel 2
ISPRA, 2024. Italian Emission Inventory 1990-2022. Informative Inventory Report 2024 (https://www.isprambiente.gov.it/it/pubblicazioni/rapporti/)
Data quality assessment
ISPRA (Italian National Institute for Environmental Protection and Research)
Utilizzati i dati ISPRA dell’Inventario nazionale delle emissioni in atmosfera (https://emissioni.sina.isprambiente.it/inventario-nazionale/).
National
1990 - 2022
Indicator assessment
Estimates are developed as part of the compilation of the National Air Emissions Inventory. Data can be aggregated using the Tropospheric Ozone-Forming Potential (TOFP), a metric that applies specific weighting factors to precursor substances based on their relative contribution to ground-level ozone formation. These conversion factors are adopted by the European Environment Agency (EEA) in environmental reporting and are particularly valuable for ensuring comparability and validation at the EU level.
For atmospheric pollutants, the estimation methodology follows the guidelines of the EMEP/EEA Air Pollutant Emission Inventory Guidebook – 2019. A detailed description of the methodological framework is provided in the Informative Inventory Report (IIR), available at:
In 2022, emissions of nitrogen oxides (NOx) amounted to 620 kt, while non-methane volatile organic compounds (NMVOCs) totaled 823 kt. Nitrogen oxides (NOx) achieved the reduction target imposed by Directive 2016/2284 starting in 2020 (-40%) already in 2014; by 2022, this reduction reached -52% compared to the 2005 levels. Similarly, NMVOCs achieved their reduction target (-35%) starting from 2020, with a decrease of 38% compared to 2005, which was maintained through 2022 (Table 1).
From 1990 to 2022, emissions of tropospheric ozone precursors have shown a significant decrease (-71% for NOx and -58% for NMVOCs), primarily driven by the substantial reduction in emissions from two key sectors: transportation (road transport and other mobile sources) and solvent use (especially for NMVOCs) (Tables 1, 2, and Figure 3).
Data
Table 1: National Emissions of Ozone Precursors by Sector
ISPRA
A: Energy Combustion and Transformation Industry;
B: Non-Industrial Combustion;
C: Industrial Combustion;
D: Production Processes;
E: Extraction and Distribution of Fossil Fuels/Geothermal;
F: Use of Solvents;
G: Road Transport;
H: Other Mobile Sources;
I: Waste Treatment and Disposal;
L: Agriculture.
The emission values have been updated in accordance with the annual update of the national emission inventory.
Tabella 2: Emissioni nazionali di precursori dell’ozono in equivalente di formazione dell’ozono troposferico
ISPRA
Fattore di conversione in TOFP: NOx =1,22; COVNM=1
I valori di emissione sono stati aggiornati coerentemente con l'aggiornamento annuale dell'inventario nazionale delle emissioni.
Figure 1: National emissions of NMVOCs by sector.
ISPRA
The emission values have been updated in accordance with the annual update of the national emission inventory.
Figure 2: National emissions of NOx by sector.
ISPRA
The emission values have been updated in accordance with the annual update of the national emission inventory.
Figure 3: National emissions of ozone precursors in tropospheric ozone formation equivalent.
ISPRA
Conversion factor to TOFP:
NOx = 1.22
COVNM = 1
The emission values have been updated in accordance with the annual update of the national emission inventory.
To ensure consistency and comparability of the inventory, the annual emission update involves the continuous revision of the entire historical series based on the latest information and the most recent methodological developments. Natural sources (other emission sources and sinks) are not included in the totals, in line with the classification adopted in the emission inventory estimation.
Regarding nitrogen oxides (NOx), the contribution of road transport emissions has remained fairly stable over the years and is the primary source of NOx emissions at the national level (41% in 2022). Starting in 1993, mainly due to the introduction of catalytic converters, the upward trend in road emissions was reversed. These emissions were reduced by 74.8% in 2022 compared to 1990 levels. NOx emissions from modes of transport other than road transport decreased by 45.2% from 1990, and they represent the second-largest source of emissions at the national level, contributing 23.1% of the total emissions in 2022.
From non-industrial combustion, the only sector to show an increase (+21% since 1990), 12.5% of the total emissions originate, while industrial combustion and combustion in the energy production and transformation industry sectors contribute 8.4% and 6.3% of the total emissions at the national level in 2023, respectively (Table 1, Figure 2).
Non-methane volatile organic compound (NMVOC) emissions primarily originate from: solvent use (40.2% of total emissions in 2022), which has decreased by 44.5% since 1990; non-industrial combustion (20.4% of emissions in 2022), which has increased by 63.5% since 1990; transport (road transport and other mobile sources represent 11% and 2.2% of total emissions in 2022, respectively); and agriculture, where a decrease of 20.6% has been recorded, representing 14.6% of total emissions in 2022. The greatest reduction has been in transport, mainly due to the introduction of emission abatement systems in vehicles, such as catalytic converters and canisters (reducing emissions by -88.2% for road transport and -86.3% for other mobile sources) (Table 1, Figure 1).