Virtually everyone in Europe lives in polluted towns, cities and rural areas where annual average levels of fine particulate matter are higher than the World Health Organization's  (WHO) recommended limit.

In practical terms, this means that almost everyone on the continent is breathing bad air   that has been shown to be fatal.

Air pollution increases the risk of respiratory and heart disease and lowers life expectancy.

"With the current levels of air pollution, many people [are getting] sick. We know that lowering air pollution levels reduces these numbers," said Mark Nieuwenhuijsen, director of the Barcelona Institute for Global Health (ISGlobal).

How bad is air pollution in Europe?

DW partnered with the European Data Journalism Network to analyze satellite data from the Copernicus Atmospheric Monitoring Service (CAMS).

We found that in 2022, almost everyone in Europe — 98% of people — lived in areas where the concentration of fine particulate matter, commonly abbreviated as PM 2.5, was over the limit set by the WHO.

The WHO recommends that the annual average concentration of fine particulate pollution should not exceed five micrograms per cubic meter of air. A microgram is a thousand times less than a milligram.

Pollution levels differ from region to region in Europe. It can be especially severe in   parts of Central Europe, the Po valley in Italy and in larger metropolitan areas, such as Athens, Barcelona and Paris.

Our analysis shows that the most polluted regions in Europe reach annual average PM 2.5 concentrations of about 25 micrograms per cubic meter.

High air pollution levels for individual European cities have been reported before, but this new data analysis offers a first Europe-wide comparison of pollution in different regions. We show where air quality has improved and where it's gotten worse.

We also used the data to identify two places with similar problems but a different outlook. In northern Italy, pollution levels are high and seem to remain so. In southern Poland, they are also high yet appear to be falling. We looked at how mitigation strategies are helping or not.

What is fine particulate matter?

Fine particulate matter is a combination of very small solid and liquid particles of different materials and pollutants.

The pollutants are invisible to the naked eye. They have a diameter of less than 2.5 micrometers, or around 30 times thinner than a single strand of hair.

Even though there are many other pollutants that affect human health, it's common to focus on these kinds of particles as there is consistent scientific evidence of their negative effect on public health.

How does Europe compare to other parts of the world?

European air quality is generally better than in other regions of the world.

In northern Indian cities, such as New Delhi, Varanasi and Agra, for example, average PM 2.5 values can get as high as 100 micrograms per cubic meter. In Europe, our data shows pollution levels of up to 25 micrograms per cubic meter.

But even at Europe's comparatively lower levels, pollution can have a significant impact on people's health.

What's the EU's proposed limit and what do experts say? 

Europe's new air quality rules would allow an annual average concentration of 10 micrograms of fine particulate matter per cubic meter of air.

The European Parliament's Environment Committee had suggested adopting the WHO recommendations, which are stricter at five micrograms of fine particulate matter per cubic meter of air.

But even at 10 micrograms, it would be stricter than the current standards, which allow annual PM 2.5 concentrations at 20 micrograms per cubic meter — four times higher than the current WHO recommendation.

Health researchers and environmentalists argue that the new European air quality rules should mirror the WHO's guidelines but acknowledge that that would be a challenge. 

"EU limits are not only [about] health, they're also about economic arguments, [whereas] the WHO limits are made by experts that only take health into account," said Nieuwenhuijsen. "I hope they'll go with the WHO, but probably some will argue that it would be too expensive."

Let's turn to our first case study: northern Italy.

Air quality consistently bad in northern Italy

In mid-February 2023, many cities in Italy's Po valley were covered with pollution. The regions of Lombardy and Veneto were especially affected.

The daily PM 2.5 average concentration in cities such as Milan, Padova and Verona surged above 75 micrograms per cubic meter, according to Copernicus researchers. 

Geography is partially to blame: the region is surrounded by mountains and pollution created by heavy traffic, industry, agricultural emissions and residential heating is trapped in the area. 

Environmental agencies report that many thousands of people die prematurely every year due to pollution-related illnesses.

 A study published in the science journal The Lancet used pollution data from 2015 to estimate that around 10% of deaths in cities like Milan could be prevented if average PM 2.5 concentrations dropped by around 10 micrograms per cubic meter.

If Europe's major cities were able to hit the five micrograms per cubic meter target, the researchers concluded there would be 100,000 fewer pollution-related deaths every year.

But that's not the direction that the Po valley is headed. 

"On top of having a negative geographical situation, we've been doing exactly the opposite of what we should do," said Anna Gerometta, a lawyer and president of Cittadini per l'Aria, an NGO that advocates for stricter air quality policies in Italy.

Gerometta said that measures to limit emissions from cars, residential heating and meat factories were too weak to face the scale of the problem.

In Poland, however, local strategies are showing improvements.

Poland gets rid of coal furnaces and improves air quality

In parts of Poland, pollution levels are among the highest in Europe. But they have decreased steadily since 2018 — the first year in the data we analyzed.

Take the city of Krakow, the second largest city in the country. Back in 2018, the region saw annual pollution levels of nearly 25 micrograms per cubic meter. By the end of 2022, it had dropped by more than 20%.

Neighboring cities Katowice, Gliwice and Tychy, and also Poznan and the capital Warsaw, saw a drop in pollution, too. 

The improvements came after Polish authorities launched a plan to modernize household heating systems, known commonly as "smokers." The process has been ongoing for ten years.

"We call them 'smokers' as they produce a lot of smoke, but they are old furnaces," said Piotr Siergiej at the environmental organization Polish Smog Alert. "Nearly 800,000 have been replaced, but there are still around 3 million left. It's a slow process."

In the Krakow area, where a ban on burning coal and wood for domestic heating came into effect in 2019, almost all the old heaters have been replaced.

How do public attitudes affect air quality policy?

"Ten years ago, if you talked about air pollution in Poland, people said it was not a big deal it felt like banging your head against the wall," Sierjiej said. "But after years of constant banging, the biggest success is the change in perception. The law is important, but politicians will only do what [voters want]."

In Italy, environmental campaigners have noticed a similar problem in bridging a gap between science and daily life: "People don't understand the issue with air pollution. As you often don't see it, you don't realize what the impact is," said Gerometta. 

But things are changing. 

According to a 2022 Eurobarometer survey, a majority of Europeans see respiratory diseases caused by air pollution as a serious problem now. While many respondents said they didn't feel well informed about the current standards, the large majority of those that are aware think that air quality rules should be strengthened.

For data, code and methodology behind this analysis, see this repository. You can find more data-driven stories by DW here.

Edited by: Gianna-Carina Grün & Zulfikar Abbany

This project is a collaboration among several media outlets in the European Data Journalism Network .