Europe’s air pollution hotspots:

The fine particles in Europe’s urban air have gradually been decreasing over the past decade. This is good news: pollutants in the air, such as fine particulate matter, reduce people’s life expectancy and can aggravate many chronic respiratory or cardiovascular diseases.

The annual mean concentration of fine particles (PM2.5) in urban areas of the EU was 19.4 μg/m3 in 2011. This has gradually decreased to 12.6 μg/m3 in 2019, according to the latest statistics released by the EU statistics agency, Eurostat.

But even though these pollutants sit within air quality thresholds, there are still a number of hotspots in Europe where pollution is higher.  And despite the improvement, 2019 levels are still above those recommended by the World Health Organization (10 μg/m3 annual mean).

The WHO estimates that air pollution kills 7 million people worldwide each year.

Fine particles with a diameter of less than 10 micrometres (PM10) can be carried deep into the lungs, causing inflammation and exacerbating heart and lung problems.

Even smaller particles – those with a diameter of less than 2.5 micrometres (PM2.5) – can travel even further into the lungs, leading to more severe health consequences.

Within Europe, annual mean PM2.5 concentrations are highest in urban areas of Bulgaria (19.6 μg/m3) and Poland (19.3 μg/m3), followed by Romania (16.4 μg/m3) and Croatia (16.0 μg/m3).

Better air quality is found in urban areas of Estonia (4.8 μg/m3), Finland (5.1 μg/m3) and Sweden (5.8 μg/m3), which have the lowest concentration of these fine particles.

With a succession of lockdowns around the world over the past 18 months, air in some of the world’s biggest cities has been visibly clearer at times.

Factory closures and fewer flights and cars on the roads had a huge impact. Measurements taken by the European Space Agency’s Sentinel-5P satellite show that during late January and early February 2020, levels of nitrogen dioxide over cities and industrial areas in Europe were significantly down on 2019 levels.

But a year on, as lockdowns started to ease, the same satellite is showing that air pollution is rebounding to pre-COVID levels.

At the June 2021 G7 Summit, leaders committed to step up their actions to combat climate change. They reaffirmed their pledge to raise $100 billion a year to help poorer nations cut emissions. Agreement was also reached to put biodiversity and the environment at the heart of COVID-19 recovery plans.

This article originally appeared on the World Economic Forum.