NOx from diesel vehicles is by far the most significant source of ground-level ozone in most European cities. https://en.wikipedia.org/wiki/Tropospheric_ozone#

NOx from diesel vehicles is by far the most significant source of ground-level ozone in most European cities. https://en.wikipedia.org/wiki/Tropospheric_ozone#Formation https://en.wikipedia.org/wiki/Tropospheric_ozone#Formation