Transboundary ozone responsible for 88% of ozone-related deaths in Europe

A new study has examined the impact of transboundary ozone in Europe, revealing which countries suffer most from it and which are most responsible for exporting it.

Ground-level ozone is formed by the interaction of sunlight with volatile organic compounds (VOCs) and nitrogen oxides (NOx) emitted by sources such as cars, power plants, refineries and chemical plants.

As such, ozone is more likely to reach unhealthy levels on sunny days in urban environments, but as it can last for weeks it can be transported long distances by wind. It is the impact of this that the study addresses.

The study was led by the Barcelona Institute for Global Health (ISGlobal), in collaboration with the French National Institute of Health and Medical Research (Inserm), and the Barcelona Supercomputing Center (BSC-CNS)

The team examined ozone-related deaths across 35 European countries (around 530 million people) between 2015 and 2017. During this period, it was estimated that 114,447 deaths were attributable to ozone.

They found that imported ozone was responsible for 88.3% of those deaths. 

Most of this transboundary ozone came from hemispheric or intercontinental sources outside Europe but ozone imported from other  European countries was still responsible for 20.9% of deaths attributable to ozone.

Hicham Achebak, a researcher at Inserm (France) and ISGlobal said: ‘The health effects of ozone, and of any air pollutant in general, are far from being a local issue. In this study, we found that 11.7% of deaths attributable to ozone were caused by national sources. This fact underlines the need for coordinated actions at local, continental and global scales by all countries to reduce ozone concentrations and their impact on health.’

Prevailing westerly winds mean that heavily industrialised countries are a particular burden on their neighbours to the east. As such, ozone originating in France had a significant impact on Luxembourg, Switzerland and Belgium, while Germany has a similar effect on Luxembourg, the Czech Republic and the Netherlands.

For this reason, countries to the east of the continent see much higher than average rates of deaths due to domestic ozone: Spain 53.7%, France 47.1% and Portugal 46.2%.

The team point to their findings as an indication that there is need for a systematic quantification of national, EU and non-EU contributions to air pollution, especially for air pollutants such as ozone that are easily transported across political borders.

Joan Ballester Claramunt, ISGlobal researcher and co-senior author of the study said: ‘Thus far, mitigation efforts have focused primarily on national and regional scales, lacking a comprehensive, transboundary assessment of the associated health effects. Our study is a first step towards this in-depth analysis, which would help achieve WHO air quality standards to prevent premature deaths and other health impacts such as hospitalisations and chronic diseases.’

Aware that these results might suggest that local action is relatively futile, the team are quick to point out its importance: ‘During the highest ozone episodes the local/national contributions can increase substantially, and local mitigation actions can contribute to considerably reduce daily exceedances of the regulated thresholds. Additionally, local mitigation strategies are key towards reducing the export of ozone to other regions and countries’ says Carlos Pérez García-Pando, ICREA and AXA Research Professor at the Earth Sciences Department of BSC-CNS and co-senior author of the study.