Ten pigeons wearing lightweight sensors have been released in London to monitor pollution. The birds have been fitted with tiny backpacks which monitor nitrogen dioxide, ozone and volatile compounds.
The Pigeon Air Patrol means people can then can find out how much pollution is registered in their area.
It is also possible to view the pigeons' flight movements on a live map.
Racing pigeons are being used for the project. A vet is on hand to check the pigeons do not suffer any distress.
Approximately 10,000 people die from air pollution each year in London alone.
The campaign hopes to "show Londoners how air pollution affects them, especially during rush hour" using the Pigeon Air Patrol service.
It also aims to encourage Londoners to become beta testers for a wearable version of the air pollution measuring device.