RECAST

Air quality management in Luxembourg is undergoing a structural transition driven by the revised Ambient Air Quality Directive (EU) 2024/2881 and the update of the National Air Pollution Control Programme. Stricter limit values for PM2.5, PM10, NO2 and O3 require a shift from retrospective assessment towards predictive, evidence-based decision making. At the same time, persistent challenges remain, including elevated O3 levels, transboundary pollution, and the increasing relevance of natural contributions such as Saharan dust. Operational stakeholders, in particular the Administration de l’Environnement (AEV), require methodologies that go beyond conventional monitoring. These include spatially explicit compliance indicators, traceable attribution of exceedances, and integrated assessments linking environmental exposure to human health. The increasing interaction between climate change, air pollution, and aeroallergens further reinforces the need for coupled analytical frameworks. RECAST is motivated by this convergence of regulatory pressure, scientific gaps, and operational demand. It builds on the existing Decision Support System developed in the CAMS-NCP Scaler project and extends it towards a fully operational platform that transforms Copernicus data into actionable policy-relevant information.

RECAST introduces three interconnected innovations that extend the current state of air quality assessment in Luxembourg from descriptive analysis to operational intelligence.

• First, a spatial distance-to-target framework will be implemented, quantifying the gap between current pollutant levels and the 2030 limit values. This approach moves beyond station-based compliance assessment by providing continuous spatial coverage and enabling identification of priority intervention zones. The methodology integrates CAMS ensemble reanalysis data with national observations, producing harmonised and reproducible compliance metrics.
• Second, RECAST develops a validated methodology for detecting and quantifying Saharan dust events as natural contributions to particulate matter exceedances. This includes the integration of CAMS aerosol products from several vertical layers, and chemical validation using in-situ X-ray fluorescence measurements with the mobile air quality laboratory of LIST. The resulting workflow will enable, for the first time in Luxembourg, a traceable and operational deduction of natural events in line with European regulatory requirements.
• Third, the project establishes a coupled pollen–O3 exposure forecasting system. By combining CAMS forecast products for O3 and allergenic pollen types with population and demographic data, RECAST generates spatially resolved exposure indicators. This represents a methodological shift towards integrated environmental–health analytics, addressing combined risks rather than isolated pollutants.

All three components are embedded in a modular Decision Support System architecture, enabling automated data ingestion, processing, visualization, and user interaction. The co-development approach with the AEV ensures that these innovations are not conceptual but directly operational.

RECAST delivers impact across multiple levels of the air quality management system. At the institutional level, it strengthens the operational capacity of Luxembourg to implement Directive (EU) 2024/2881 by embedding validated CAMS-based workflows into national decision-making processes. The Decision Support System evolves from a data access tool into a compliance-oriented analytical platform. At the policy level, the project provides traceable and reproducible metrics for regulatory reporting, including the quantification of distance-to-target gaps and the formal attribution of natural pollution events. This enables more transparent and defensible compliance assessments and supports the design of targeted mitigation strategies. At the scientific level, RECAST advances methodologies for integrating atmospheric modelling, in-situ observations, and exposure assessment into unified workflows. It establishes reproducible protocols that can be transferred to other Member States. At the societal level, the project improves communication of air quality risks by providing combined exposure indicators for O3 and pollen. This enables targeted information for sensitive population groups and strengthens the link between environmental monitoring and public health. At the environmental and economic level, the separation of anthropogenic and natural contributions allows more efficient allocation of mitigation efforts, avoiding unnecessary measures while maintaining compliance with regulatory thresholds.