Objective of this report
Ground-level and tropospheric ozone is one of the most harmful air pollutants in Europe today. Elevated levels cause health problems, premature deaths, reduced agricultural crop yields, changes in ecosystem species composition and damage to physical infrastructure and cultural heritage.
Ozone (O3) is not directly emitted to the atmosphere but formed in complex photochemical reactions from ozone precursor gases. O3 formation depends strongly on meteorological conditions (e.g. solar intensity and temperature). The nitrogen oxide (NOx) regime is the main factor determining whether O3 is produced or removed in the troposphere. The major precursors emitted due to human activities — mainly transport — are NOx, non-methane volatile organic compounds (NMVOC) and carbon monoxide (CO).
European countries have significantly reduced anthropogenic emissions of ozone precursor gases since 1990. In general, however, ambient air measurements in urban and rural areas of Europe do not show any downward trends in ground-level ozone. The main purpose of this report is to shed light on possible reasons.