Pigeons fitted with ultralight air-monitoring vests have been flying across London this week in an attempt to highlight the capital’s pollution problem.

The ten pigeons, which were flying around London until Wednesday, were monitoring levels of nitrogen dioxide and ozone. People can tweet their location at the company, and get an update on the air pollution levels in their area, as found by the group’s pigeons. Researchers back at Imperial will be analysing the data.

Pigeons fly about 30m off the ground, which means the data they collect on compounds in the air are relevant for humans. Their backpacks weigh about 25g.

The ‘Pigeon Air Patrol’ is the combined effort of Plume Labs, a marketing and technology agency, Twitter and researchers from Imperial’s Centre for Environmental Policy.

The idea won organisers the London Design Festival’s #PoweredbyTweets competition last year, which saw them awarded free Twitter ads to get the project started.

Later this year, the project will expand, abandon pigeons, and use humans carrying sensors to monitor pollution levels. The company plans to get members of the public to carry light sensors that talk to an app on their phones and a wider network of “air patrollers”. This part of the project is still at the crowdfunding stage.

Last year, the nitrogen dioxide levels on Oxford Street broke the legal limit by a thousand times. The high concentration of diesel fuelled buses are suspected to be a contributory factor Last year, a study from King’s College London estimated that long term exposure to nitrogen dioxide and particulates in London’s air were killing nearly 10,000 people a year.