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Copernicus finds 34% of the world breathed extremely poor ozone air through mid-September
Copernicus, the EU's atmosphere monitor, says 34% of the world's population breathed "extremely poor" ozone air from January 1 to September 15. Its report partly blames heat and wildfires and finds ozone flat even where emission rules have cut other pollutants.
The Scientist · Science desk
What happened
- The report rates air "extremely poor" when ozone sits well above the WHO guideline of 100 micrograms per cubic metre, averaged over eight hours.
- Two-thirds of North Americans and 45% of Europeans breathed ozone air rated poor or very poor.
- Oceania came out best, with 66% of its population in good ozone air and the remaining 34% in fair.
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Why it matters
- constraint Ozone forms when heat and sunlight act on emissions, so cutting emissions works on only one of its inputs while a warming climate keeps supplying the other.
- cost An EEA official linked ozone to 60,000 premature deaths a year in Europe; with EU rules failing to lower ozone so far, current policy has no demonstrated way to shrink that toll.
- exposure This year's fire smoke crossed borders, so part of any country's ozone exposure comes from fires its own emission rules cannot reach.
The 34% is a count of people, built from satellite data and computer models [4]. Its window runs from January 1 to September 15 [1]. That covers the whole northern summer. The same summary puts 17% of the world in "very poor" air and 5%, one person in twenty, in "good" [3]. The remaining 44% falls in the two middle bands, "poor" and "fair" [1].
Ozone is hard to regulate because it is not emitted directly. It forms when heat and sunlight react with emissions from wildfires, vehicles and industry [5]. The report says ozone has resisted the cuts that worked on other pollutants in recent decades because climate change feeds the conditions it forms in [19]. EU regulation has reduced emissions of air pollutants except ozone, the report said [7]. In North America, ozone levels stayed "relatively unchanged" despite what the report called ambitious emissions reduction policies [8].
According to CAMS, this year's ozone was driven "in part" by record-breaking heat waves and wildfires in Europe and North America, which sent smoke well beyond their borders [6]. A hot, smoky year with high ozone is what the chemistry predicts [5]. The evidence shows ozone holding level while rules cut other pollutants. It leaves open whether warming is now pushing exposure back up, and how much of this year's 34% the weather added. Answering either takes a multi-year series or model runs that separate weather from emissions. The published account of the report includes neither, and it has no 2025 figure to set beside this one.
Asia's emissions are driven by industrialization, economic development and transport, plus wildfires and the burning of crop residue, the report says [10]. New Delhi, Dhaka, Chongqing and Lahore were among the cities rated "extremely poor" [11]. Smoke from forest fires, crop burning and cooking is a significant contributor to Africa's air pollution. There, 8% of people had extremely poor ozone air and 19% poor or very poor [14]. South America stayed mostly in good or fair air, 81% of its population, even with very high ozone in Sao Paulo and extremely elevated levels in Rio de Janeiro [15].
"Air pollution does not stop at borders. It can travel thousands of kilometers, crossing continents and oceans and affecting air quality far from its source," CAMS director Laurence Rouil said in the Atmosphere Watch report [17].
What to watch
- The El Nino that began in June and is due to peak later this year, which CAMS says could drive more fires in Southeast Asia after Indonesia's major wildfires.
- A full-year CAMS tally extending past September 15, and whether it moves the 34% figure.
- Any EU move to tighten controls on ozone-forming emissions from vehicles and industry, since ozone is the pollutant its rules have not reduced.