Most of the surface ozone that leads to premature deaths in Europe comes from beyond the continent’s borders, according to a new study.
Researchers from the Barcelona Institute for Global Health (ISGlobal), with the French National Institute of Health and Medical Research (Inserm) and the Barcelona Supercomputer Center, calculated the impact of imported ozone across 813 regions in 35 European countries.
They found that roughly 60 per cent of all deaths attributable to ground-level ozone (O3) came from outside Europe’s borders.
Just under 12 per cent of deaths attributable to the air pollutant were caused by national sources of pollution, the researchers added.
Ground-level ozone comes from the chemical reaction between pollutants from cars or power plants reacting to sunlight. It’s different from the ozone layer higher up in the atmosphere, which protects us from the Sun’s ultraviolet radiation.
The researchers analysed data from May to October over a two-year period, when surface ozone is at its highest level.
They used numerical models to “track and trace the precursor emissions, mainly nitrogen oxides and volatile organic compounds,” and calculate how they are dispersed in the atmosphere, according to study co-author Dr Oriol Jorba from the Barcelona Supercomputing Center.
He added they can use the model to quantify “the contribution from a specific country, neighbouring countries or even the atmospheric contribution from outside the domain of study [Europe]”.
The researchers estimated that the number of deaths over the study period from 2015 to 2017 was around 114,000, which is higher than estimates from the European Environment Agency (EEA).
This is in part because they assumed there was no safe threshold for ozone’s impact on health and is based on how they calculated mortality.
“Ozone has harmful effects on human health (respiratory diseases) and ecosystems (including crop yields) which have significant costs in terms of mortality and morbidity and ecosystems value,” Dr Laurence Rouil, Director of the Copernicus Atmosphere Monitoring Service (CAMS), which forecasts ozone concentrations and air quality at the European and global scales, said in an emailed statement to Euronews Health.
“One of the main concerns with ozone compared to other pollutants is the fact that, despite stringent emission reduction policies that target its precursors, no decreasing trends of background ozone levels are monitored at regional or global scales,” she added.
Industrialised countries contribute to ozone-attributable deaths in other countries
The ISGlobal and Inserm study found that Europe’s most industrialised countries contributed to ozone-related deaths outside their borders. O3 from France impacted neighbouring countries such as Luxembourg, Switzerland, Belgium, and Spain.
Surface ozone from Germany contributed to deaths in Luxembourg, the Czech Republic, and the Netherlands.
Some countries “are importing more from their neighbours than what they produce, at the national level,” Jorba said.
Wind patterns also influenced the source of ozone, with southwestern European countries the least impacted by imported surface ozone.
Spain, France, and Portugal thus had the highest amount of national surface-level ozone contributing to mortality compared to other European countries.
In Mediterranean countries like Malta and Cyprus, shipping emissions also had an impact.
There were several limitations to the study, including that the researchers did not consider chronic effects and assumed a fixed link between ozone and mortality even though the risk may vary between populations.
The study “highlights that air pollution does not recognise boundaries and that people across Europe, and around the world, are connected through the atmosphere and air quality,” according to Rouil.
“However it does not highlight enough that due to the transboundary behaviour of ozone…if Europe is impacted by transboundary ozone then other parts of the world can, in turn, be impacted by European sources,” she added.
Researchers say the findings show a need for coordinated local and global action to reduce O3 concentrations instead of just national and regional mitigation efforts.
