Interested in this kind of news? Receive them directly in your inbox. Delivered once a week. Sign Up With Milan struggling to reduce its air pollution to the levels required by EU law, campaigners have advocated a ban on diesels in the city, but the mayor, Giuseppe Sala, has been reluctant to stop people using their cars. So Cittadini per l’Aria (Citizens for Clean Air) began a programme aimed at getting private citizens to collect information on nitrogen oxides (NO2) levels under the slogan ‘NO2 – No thanks!’. A call went out for volunteers to be part of a citizens’ science campaign. The volunteers were asked to place passive sampler tubes that measure NO2 in front of homes, schools and workplaces around the city for 30 days at a time. They then returned them to Cittadini per l’Aria, which sent them for analysis. The results – calibrated with the local monitoring station – were then placed into an interactive map where citizens could verify the concentration of NO2 measured at each sampler location on a monthly basis, and work out the yearly concentrations. At each sampler location on the map, the additional impact on health from NO2 limits being exceeded was made clear. The 2017 results were then given to the Milan media, and they gained a lot of publicity. That led to a political campaign, and the governing coalition led by the mayor is now supporting a ban on diesels in Milan by the start of 2025. Anna Gerometta of Cittadini per l’Aria said: ‘We are still not sure exactly how diesels will be banned, and we are keeping an eye on the mayor’s office for this detail, but there’s no question that using volunteers to collect data which made a very strong scientific argument was a powerful combination in changing the political climate. It is a form of people power, with the people collecting robust evidence that shows the damage NO2 causes.’ More than 200 citizens participated in the 2017 campaign in Milan, while more than 1,000 are participating in the 2018 campaign in four Italian cities (Rome, Brescia, Bologna and Milan) using the same campaigning model, with data to be released in late May.