Total O3 exceedance counts per scenario. The number of extra exceedances predicted as a result of O3 enhancement from shale gas scenario emissions, over JJA, applying the EU and WHO thresholds for O3 (120 and 100 μg m–3 respectively), summed over all AirBase stations within our domain that have at least 75% temporal data coverage. DOI: https://doi.org/10.1525/elementa.387.f10