Evaluation of Scenarios for the Application of the Future PM_2.5 and PM₁₀ Standards: A Case Study of Three Urban Areas in Romania and Implications for Public Policies

Directive (EU) 2024/2881 introduces stricter daily standards and alert thresholds for particulate matter, which will be applicable starting in 2030. Member States must transpose these standards by 2027. This study retrospectively applies the new framework to daily data from three urban areas in Romania from 2019 to 2024. The objective is to evaluate the risks of noncompliance and test additional, more sensitive indicators of pollution severity and source characteristics. The results show that the new standards would cause the daily and annual limits for PM2.5 and PM10 to be exceeded in at least two of the three analyzed cities. Three indicators are proposed and applied: (i) Excess Concentration (EC), which quantifies the total amount of daily exceedances of the limit value; (ii) Toxic Load Index (TLI), which integrates the PM2.5/PM10 ratio as a proxy for toxicological potential; and (iii) Episode Index (EI), which captures the magnitude and duration of episodes that would trigger alert thresholds. The study includes a summary review of the air quality legislative framework and contributes to public policy literature by emphasizing risk-proportionate interventions. The proposed indicators support a smoother transition to forthcoming Euro-pean requirements.