Ground-level Ozone

Primary sources: Secondary pollutant formed by sunlight reacting with NOx and VOCs from traffic, industry, solvents.

Health impact: Reduces lung function, triggers asthma, increases respiratory hospitalizations. Highest in summer.

Measurement method: Reference: UV photometry, EN 14625

Air pollutant concentrations in the European Union are reported under two distinct regulatory regimes that European citizens regularly encounter without realising it. The European Union legal limits, codified in the Ambient Air Quality Directive adopted in 2008 and revised in October 2024, set binding annual and daily ceilings that trigger national action plans and Court of Justice infringement procedures. Separately, the World Health Organization 2021 global air quality guidelines reflect the current epidemiological evidence on cardiovascular, respiratory, and cancer outcomes and operate as a non-binding health benchmark. The gap between the two is the policy lever — the revised 2024 directive halves several legal limits and aligns most thresholds closer to the WHO recommendation by January 2030.

The EU regulatory limit for Ground-level Ozone is 1.2× the WHO 2021 health-evidence guideline (120 vs 100ug/m3, both annual means). The revised EU Ambient Air Quality Directive adopted in October 2024 will tighten this gap by 2030.