Overview

• Airparif’s first post-change assessment reports average NO2 concentrations along the périphérique fell by 6% (about −2 µg/m³) based on June 2025 data.
• Measured traffic volumes on the 35 km ring declined by roughly 4%, a change Airparif says exceeds long‑term trends and reflects recent measures.
• Improvements vary by location, with NO2 reductions reaching up to 8% on some stretches and a few increases observed in the west.
• Within 500 meters of the roadway, overall pollutant levels remained broadly stable, suggesting no degradation on adjacent corridors.
• Fine particle impacts (PM10 and PM2.5) were not discernible at this stage, while separate Apur monitoring found a 2.7 dB noise drop and a 14% fall in accidents for Oct 2024–Jun 2025.