HomeBlogClean Air Day: Airly reveals where the most polluted air is in Europe  

Clean Air Day: Airly reveals where the most polluted air is in Europe  

On Clean Air Day 2021, Airly has revealed it’s monthly insights into air pollution across Europe. This ranks cities* based on their air pollution levels as measured by levels of PM10 (Particulate Matter) and NO2 (Nitrogen Dioxide).  

Airly provides accurate, ultra-local, predictive data from their sensors for governments, media and businesses to tackle the issue of air pollution head-on. Airly’s platform acts as a warning system for pollution at street level and in real time with greater accuracy and at lower cost for cities & enterprises. 

PM10 analysis

PM10 is particulate matter (also called particle pollution), the term for a mixture of solid particles and liquid droplets found in the air. Drops in concentrations are clearly visible when compared to April 2021, when some cities recorded much higher results, e.g. Milan (42.8), Łódź (29.1). Although the concentrations of PM10 decreased relatively, an Italian city (Naples) was in the lead again (23,91 mean CAQI), and a very high concentration of Spanish cities (Gijon, Sevilla, Oviedo) can also be noticed. PM10 concentrations in Polish cities dropped significantly – the highest was Tychy with a recorded average CAQI of (16,82).

NO2 analysis

NO2 is a pollutant that damages immune system cells in the lungs and causes increased susceptibility to respiratory infections. It can make asthmatics more sensitive to allergens leading to a detrimental effect on their respiratory system. NO2 is produced from the fuel combustion and the leader in NO2 concentration is the Romanian city Cluj-Napoca (17.53). The British city Newcastle Upon Tyne was slightly worse (17.05), while the podium was closed by the leader of the PM10, Naples, ranking together with the nearby city of Giugliano in Campania.

Are the presented standards dangerous to health?

The dangerous yearly level of average CAQI for PM 10 and NO2 is 20. In the case of PM10, this norm was exceeded by the four cities at the top of the ranking. In the case of NO2, however, none of the cities exceeded the standard considered dangerous to health, but some have come close to it.

Airly CEO and co-founder Wiktor Warchałowski commented: “With 62% of the world’s governments sharing no real-time air quality, we wanted to take this initiative and show everyone what’s happening in the air around us on Clean Air Day. The data isn’t great for large parts of Europe but there is certainly an opportunity to tackle the problem. People need to change their habits especially with the use of cars and local authorities need to start by monitoring the problem then put in place appropriate policies to manage problem hotspots”

Air pollution – the largest environmental risk to health in the EU

According to the Europe Environment Agency (EEA) – air pollution is the largest environmental risk to health in the European Union, with around 379,000 premature deaths from exposure to Particulate Matter (PM10) in 2018 and 54,000 to Nitrogen Dioxide (NO2) in 2018. Power plants, heavy industry and – especially in the case of NO2 – increased car traffic are the main causes of pollution. 

Call to action – local authorities and people 

Local councils and municipalities can start by monitoring air quality in real-time on an ongoing basis, locating sources of pollution and bringing forward policy that targets local pollution by reducing road traffic in the busiest, polluted places.

Similarly, people need to make lifestyle choices that will benefit their air quality and environment. By choosing carsharing, cycling or electric scooters instead of cars will make a significant impact. Especially for short distance trips which are the most problematic. According to the data from Global Action Plan – in urban areas such as inner London, a third of car trips are less than two miles, and more than a half of car trips nationally are less than five miles.

The ranking of the most polluted large cities in Europe (PM10) for May 2021 is below:

Rank City  Country  European CAQI air quality index
20 Huelva Spain 15.86
19 Częstochowa Poland 16.13
18 Katowice region Poland 16.24
17 Kielce  Poland 16.32
16 Rotterdam The Netherlands  16.35
15 Łódź Poland 16.57
14 Toruń Poland  16.71
13 Palma de Mallorca Spain 16.74
12 Tychy  Poland 16.82
11 Ghent  Belgium  16.89
10 Antwerp Belgium 17.02
9 Malaga Spain 17.49
8 Sofia Bulgaria 17.81
7 Skopje North Macedonia  17.99
6 Santander Spain 18.21
5 Bilbao  Spain 19.24
4 Oviedo Spain 20.19
3 Sevilla Spain 20.94
2 Gijon Spain 23.73
1 Naples Italy  23.91


The ranking of the most polluted large cities in Europe (NO2) for May 2021 is below:

Rank City  Country  European CAQI air quality index
20 Wrocław Poland 11.01
19 Rouen France 11.10
18 Slough, Windsor United Kingdom 11.13
17 Budapest Hungary 11.16
16 London United Kingdom 11.92
15 Dundee United Kingdom 12.04
14 Genoa Italy 12.20
13 Brest France  12.29
12 Kraków Poland  12.43
11 Edinburgh United Kingdom 12.54
10 Granada Spain 13.24
9 Leeds  United Kingdom 13.27
8 Bucharest Romania 13.33
7 Ploiesti  Romania 13.38
6 Marseille France 14.18
5 Athens, Piraeus Greece 14.57
4 Timisoara Romania 14.84
3 Naples Italy 15.88
2 Newcastle-upon-Tyne United Kingdom 17.05
1 Cluj-Napoca Romania 17.53

Airly provides actionable insights about air quality with its AI-driven algorithms that predict air pollution for the next 24 hours with a verifiability of up to 95%. Airly gives customers across the globe an environmental intelligence platform by installing networks of sensors that track all the key pollution markers – particulate matter (PM1, PM2.5, PM10) and gases (NO2, O3, SO2 and CO). 


 Measurement method
*Airly used data developed by a team of scientists from the European Commission. From the dataset, only cities with a population of more than 100,000 people were considered (which is approximately 400 locations). From this, cities with at least 4 different measurement points (including Airly sensors, PurpleAir and state stations) were considered. The final data is presented using the European CAQI air quality index.

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