Europe’s air quality suffers from pollutants born beyond its borders, study says

(CN) — Geopolitical boundaries in Europe, not unlike elsewhere on the planet, provide each country in the continent with some degree of security from foreign threats. But natural forces such as water and air recognize no such boundaries. 

A study published Monday by the journal Nature Medicine highlights that point: The majority of toxic ground-level ozone in Europe originates elsewhere, yet the chemical is responsible for up to 88.3% of all European deaths attributable to air pollutants.

Ground-level ozone, or O3, is formed when sunlight mixes with precursor gasses — typically nitrogen oxides and volatile organic chemicals — in the troposphere, the lowest region of the atmosphere.

Thanks to an effect that typically is amplified during the summer months, ground-level ozone can cause or exacerbate respiratory ailments like asthma and chronic obstructive pulmonary disease.

Air quality is of particular concern in Europe, where the European Environment Agency estimates as much as 95% of the population is exposed to quantities of ground-level ozone exceeding daily guidelines. 

Leading the study published Monday was Hicham Achebak, a researcher at Inserm in France and a postdoctoral fellow at the European Commission. He and his colleagues used air-quality and epidemiological modeling to quantify the mortality burden in Europe associated with ozone pollution from various geographical sources. In part, the study involved gathering data about six million deaths in 35 European countries between 2015 and 2017, and finding that as many as 114,447 were attributable to ground-level ozone. 

Ozone air pollution from beyond national borders was associated with 88% of ozone-attributable deaths, according to the researchers, meaning only 12% stemmed from Europe.

Researchers found higher O3 levels were more common in southern Europe, where generally higher temperatures make the atmosphere more conducive to the formation of ozone.

As expected, when it comes to associated deaths, mortality burdens were highest in countries with bigger populations, but death rates were higher in the southeastern European countries of Bulgaria, Serbia, Croatia, Hungary, Greece and Romania.

Similarly, more densely populated countries and those in southern Europe produce more of their own ground-level ozone than those to the north. The top five countries for daily concentrations of O3 were Malta, Cyprus, Italy, Greece and Albania. The bottom five were Finland, Iceland, Ireland, Sweden and Norway. 

Ireland, Iceland, Norway, Luxembourg and Liechtenstein posted the lowest ozone-linked mortality rates.

In their study of 813 contiguous regions in Europe, the researchers categorized the sources as national (originating within a given country); from within the 35-country study area; from countries outside the 35 countries; from the ocean; or from the atmosphere but outside of the study area.

The majority of ground-level ozone (57.6%) originates from the latter category. This underscores a need for counties to coordinate their actions to reduce ozone and its effects on health, the researchers write in the study, "given that no effective strategy may be developed without international agreement on air pollution reduction.”

Comparatively, 21% of ozone originated within Europe, while 7% originated from maritime sources, such as cargo vessels and offshore drilling. 

Researchers also accounted for the role of climate change in the analysis. They predicted additional warming will reinforce conditions favorable for O3 development and said fighting climate change is key to improving air quality.

The study was the first continent-wide assessment of ground-level ozone contributors and related mortality burden. 

“Achieving the air-quality guidelines set out by the [World Health Organization] and avoiding premature deaths and other types of health impacts of O3 require not only the implementation of national or coordinated pan-European actions, but also global strategies,” the researchers concluded.

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