Ten pigeons are flying over London for the next two days monitoring the city's pollution levels. The birds are wearing tiny backpacks which live-tweet pollution data from their account @PigeonAir

We're seeing lots of areas showing high levels of air pollution right now. Stay safe, London! #PigeonAir pic.twitter.com/gT1K7FKB5P

— Pigeon Air Patrol (@PigeonAir) March 15, 2016

London broke its annual air pollution limit within the firist week of January.  The backpacks can detect nitrogen dioxide and ozone gases. The backpacks detect nitrogen dioxide and ozone gases, then tweet out the readings. So far, the readings have shown moderate and high pollution levels. The air has only been deemed "fresh" a handful of times so far. 

The pigeons will tweet until Wednesday. After that, 100 people will be recruited to beta test a new human version of the pollution monitor. 

And we're off! The first #PigeonAir patrol flies from Brick Lane, monitoring air pollution as we go! pic.twitter.com/W8KnyrxnCe

— Pigeon Air Patrol (@PigeonAir) March 14, 2016