Revising ambient air quality standards – the implications for compliance in Europe towards 2050

The WHO AQG provide key advice on the impacts of air pollution and the 2005 version of the guidelines has served as a reference for the present day AAQS set in 2008, which are in force since 2010. In 2021 however, WHO revised downwards its AQG which now serve as the reference to the revised proposal of the AAQD that was published by the EC in October 2022.

This study commissioned by Concawe uses a forecasting method to assess future concentrations of the key pollutants O3, NO2, PM10 and PM2.5 which are most associated with health impacts. The metrics that are considered are the frequency of exceedance of a daily threshold value (days/year) and exceedance of an annual average concentration (μg/m3).

The study uses the same methodology as the supporting studies carried out for the Second Clean Air Outlook (CAO2)2 of the European Commission. Three common scenarios for future emissions are considered under the CAO2:

• The baseline scenario which describes the future emissions expected to take place if no new emission control legislation is enacted. This study uses the term Current Legislation (CLE) and adopts the assumptions of the Second Clean Air Outlook. This takes into account the forecast economic activity and the consequential emissions together with the impact of legislated emission reductions, including national measures.
• Maximum Technically Feasible Reductions (MTFR). This applies the most stringent available emissions reduction to controlled sources without requiring closure of installations.
• Maximum Technically Feasible Reductions plus 1.5 LIFE (MTFR + 1.5 LIFE). This scenario includes economic activity changes consistent with a Climate Plan to limit global temperature rise to 1.5 oC by 2050, primarily through change in energy use and efficiencies associated with a circular economy. It adopts revised transport demand, food/supply demand reforms, agricultural changes consistent with lower meat production, enhanced crop production, carbon sequestration etc. resulting in fewer NH3 and CH4 emissions. To this scenario, MTFR is applied to governed emission sources.

These represent the upper (CLE) and lower (MTFR) bounds to expected emissions in the years to 2050 without structural changes to the European economy, and a second lower bound (MTFR + 1.5 LIFE) with structural changes.

The Concawe study also includes some additional sector-specific emission reduction scenarios. The purpose of these is to identify which emission reduction components of the common scenarios are most influencing ambient air quality. Each scenario reduces emissions from a key emitting sector to zero.

All of the emission reduction scenarios start with reductions in 2025. The base year for the start of the modelling is 2015.

The Concawe study results are evaluated by comparing the predicted results at each monitoring station in Europe with the 2021 issued WHO Global AQG Interim Target and Guideline metrics [4]. The number of stations where the monitoring station concentration record meets the metric is counted. This also gives the number of stations that do not meet the metric. The number of stations where the metric is exceeded is expressed as a proportion (%) of the total number of stations to allow comparisons between countries, and of individual countries with the EU-27.

The geographic scope of the study is the EU-27 countries. Results for four countries (France, Poland, Italy and Spain) are also presented as indicative examples. However, the emission reductions associated with all scenarios are assumed to also take place in the UK.