Nearly 60% of ozone-related deaths in Europe are caused by international pollution

Ozone pollution was responsible for over 110,000 premature deaths in Europe in the warm seasons from 2015 to 2017. A new study suggests that nearly 60% of these deaths can be attributed to ozone transported from locations outside the continent (Nat. Med. 2024, DOI: 10.1038/s41591-024-02976-x).

Ozone is an air pollutant created when nitrogen oxides and volatile organic compounds react photochemically with each other. Both precursors are emitted by anthropogenic and natural sources.

Once formed, “these ozone molecules, which can affect health, can be transported across long, long distances,” says Oriol Jorba, a researcher at the Barcelona Supercomputing Center and one of the study’s authors.

According to Jorba, a large share of Europe’s ozone pollution during the study period came from other continents, such as North America and Asia. In contrast, around 20% of ozone-related deaths, on average, in Europe were caused by pollution produced by a neighboring country.

Some countries were more responsible than others for the premature deaths. For example, ozone produced in France was responsible for the largest share of ozone-related deaths in Luxembourg and Switzerland—32% and 29%, respectively. Meanwhile, in Liechtenstein, nearly all such deaths were caused by ozone that was transported into the country.

The idea that one region’s air pollution can affect another’s is not new. A number of studies have shown that the air quality in one region can be affected by pollution blown in from elsewhere (Nature 2017, DOI: 10.1038/nature21712).

But this new research improves upon those studies by linking the imported pollution with its effects on human health, says Steve Davis, a professor of earth system science at Stanford University who wasn’t involved in the study.

Including this health perspective, Jorba says, highlights the need for pollution mitigation efforts that take transboundary pollution into account. But he emphasizes that the findings shouldn’t imply that local mitigation efforts are useless or irrelevant. Rather, reducing ozone pollution and its health impacts must be “a collective effort,” he says.

Jorba adds that future work will aim to determine how much of this transported pollution is coming from specific anthropogenic activities, such as transportation and agriculture, versus natural sources.

That analysis “would be a big deal for policymakers interested in prioritizing investments and regulations,” Davis says.