European neighbours suffer high ozone deaths due to cross-border pollution

According to researchers from the Barcelona Institute for Global Health, over 60% of all deaths related to ground-level ozone (O3) in 35 European countries are caused by ozone originating from other states. Ozone is formed in the troposphere by the interaction of sunlight with several precursor gases.

It was found that ground-level ozone, which forms when sunlight reacts with nitrogen oxides and volatile organic compounds, has a harmful impact on the respiratory system. It can lead to asthma, chronic obstructive pulmonary disease, and infections. Researchers thoroughly examined data from the warm months, from May to October, when O₃ concentrations reach their highest levels.

The analyses used the CALIOPE air quality system, which monitors ozone concentrations and its precursors across Europe. Additionally, scientists analysed models of long-distance air pollution spread, which helped identify pollution sources.

The average O₃ concentration in the surveyed countries was 101.9 µg/m³, ranging from 76.7 µg/m³ in Finland to 130.1 µg/m³ in Malta. It is estimated that the number of ozone-related deaths reached 114,447, yielding a mortality rate of 72 deaths per million people annually. The highest death rates were recorded in Germany, Italy, France, the United Kingdom, Spain, and Poland, as well as in southeastern countries such as Bulgaria, Serbia, and Romania.

France turned out to be the largest supplier of ozone to neighbouring countries, followed closely by Germany. Ozone from France most significantly impacted Luxembourg (32.3% of ground-level ozone-related deaths), Switzerland (29.3%), Belgium (24.4%), and Spain (16.8%). Meanwhile, ozone from Germany had a significant impact on Luxembourg (24.2% of deaths), the Czech Republic (23.3%), and the Netherlands (21.5%).

Scientists highlighted the crucial role of westerly winds in the spread of ozone, which is causing a higher number of deaths in Eastern Europe due to an influx of ozone from the west. The research results indicate the necessity of systematically monitoring the contribution of individual EU and non-EU countries to air pollution. This is the first step towards meeting the air quality standards set by the WHO, which can prevent premature deaths and chronic diseases.

In their final conclusions, the researchers noted that climate warming favours the formation of tropospheric ozone. Therefore, actions aimed at preventing climate change are key to improving air quality and should form the basis of long-term global policy — summarise the experts.