Emissions of tropospheric ozone precursors

The "Emissions of tropospheric ozone precursors" fact sheet shows the emissions of nitrogen oxides and non-methane volatile organic compounds, molecules that are at the origin of tropospheric ozone formation.

The potential for tropospheric ozone formation, calculated by adding the total emissions of non-methane volatile organic compounds (NMVOCs) and emissions of nitrogen oxides (NOx) equivalent (multiplied by a conversion factor), enables monitoring of the development of aggregate emissions of tropospheric ozone precursors by activity sector and analysing their contribution.

Tropospheric ozone is a secondary pollutant formed by the reaction of precursor substances in the presence of strong solar radiation. It is a pollutant with a strong oxidising power that accelerates the degradation of materials, promotes the loss of vegetation productivity and increases the morbidity and mortality of the exposed population. As one of the greenhouse gases, it also contributes to the warming of the troposphere.

This fact sheet concerns mainland Portugal and shall be updated on an annual basis.

Objectives and targets: 
  • The Gothenburg Protocol to the Convention on Long-range Transboundary Air Pollution (CLRTAP) of the United Nations Economic Commission for Europe set as targets for air emissions in 2010 NOx = 260 kt and NMVOC = 202 kt (Decree No. 20/2004). The amendments to the Gothenburg Protocol approved by the CLRTAP Decision 2012/2 set emission reduction targets based on the reference year 2005, to be met from 2020 onwards, of 36% to NOx and of 18% to NMVOCs;
  • The Decree-Law No. 84/2018, which transposes the new Ceilings Directive, (Diretive (EU) 2016/2284) establishes new commitments for the reduction of atmospheric emissions by 2020 in line with the CLRTAP Decision 2012/2 and new commitments to be met from 2030 onwards, of 63% and 38% for NOx and NMVOCs respectively, compared to the reference year 2005.
  • The emission ceilings established for 2010 by the previous Directive 2001/81/EC, were in force until 31 December 2019.
  • The national objectives for this area are:
    • To comply with international and European agreements on air emissions;
    • Ensure that the sectoral measures necessary to achieve the objectives of reducing air emissions are implemented;
    • Assess the impact of measures to reduce air emissions, particularly with regard to potential for tropospheric ozone formation.
Progress analysis:
Last update: 
Wednesday, 1 September, 2021