This week, London is fighting filth with, well, filth. According to The Guardian, a British technology company called Plume Labs has strapped tiny backpacks onto pigeons—birds that many people consider to be “vermin of the sky”—and let them loose over the city. The backpacks are outfitted with GPS trackers and pollution sensors, which monitor the air’s nitrogen dioxide levels, volatile compounds, and ozone. The readings are then tweeted at social media users.

The “Pigeon Air Patrol” was released Monday, and will soar over London until Wednesday, the BBC reports. The purpose behind the three-day stunt? To show Londoners that the city’s air quality has gone to the birds. Pierre Duquesnoy, creative director of English marketing agency DigitasLBI, won last year’s London Design Festival award with the idea. Nearly 9500 people die each year thanks to long-term exposure to the city’s air pollution, and Duquesnoy hopes that the pigeons’ readings will raise public awareness of this sobering fact.

“It is a scandal," Duquesnoy told The Guardian. "It is a health and environmental scandal for humans—and pigeons. We’re making the invisible visible.”

Gary Fuller, an air quality expert at King’s College London, told The Guardian this was the first time he’d heard of urban animals used to monitor pollution. However, officials in Lima, Peru, recently pulled a similar move. They strapped GoPro cameras and GPS trackers onto vultures, and the birds' coordinates were tracked on a live map. This allowed citizens to keep tabs on the city’s growing trash problem.

Just like in Lima, Londoners can follow the Pigeon Air Patrol online via a map. They can also tweet their location to @PigeonAir to see how much pollution is registered in their area. To learn more about the project, watch the video above, courtesy of ODN News.

[h/t The Guardian]