They’ve been driven from Trafalgar square for being a nuisance, derided as rats with wings and maligned as a risk to public health.

But now pigeons could play a small part in helping Londoners overcome one of the capital’s biggest health problems – its illegal levels of air pollution blamed for thousands of deaths a year.

On Monday, a flock of half a dozen racing pigeons were set loose from a rooftop in Brick Lane by pigeon fancier, Brian Woodhouse, with one strapped with a pollution sensor to its back and one with a GPS tracker.

But while the 25g sensor records the nitrogen dioxide produced by the city’s diesel cars, buses, and trucks and tweets it at anyone who asks for a reading, its real purpose – and the use of the pigeons – is to raise awareness.

“It is a scandal. It is a health and environmental scandal for humans – and pigeons. We’re making the invisible visible,” said Pierre Duquesnoy, who won a London Design Festival award for the idea last year.

“Most of the time when we talk about pollution people think about Beijing or other places, but there are some days in the year when pollution was higher and more toxic in London than Beijing, that’s the reality.”

He said he was inspired by the use of pigeons in the first and second world wars to deliver information and save lives, but they were also a practical way of taking mobile air quality readings and beating London’s congested roads. They fly relatively low, at 100-150ft, and fast, at speeds up to 80mph.

“There’s something about taking what is seen as a flying rat and reversing that into something quite positive,” said Duquesnoy, who is creative director at marketing agency DigitasLBI.

Gary Fuller, an air quality expert at King’s College London, said it was the first time he had heard of urban animals being put to such use.

“It’s great that unemployed pigeons from Trafalgar Square are being put to work. Around 15 years ago tests were done on around 150 stray dogs in Mexico City, showing the ways in which air pollution was affecting lungs and heart health. But this is the first time that I’ve heard of urban wild animals being used to carry sensors to give us a picture of the air pollution over our heads.”

The release of the pigeons for three days this week, dubbed the Pigeon Air Patrol, came as moderate to high pollution affected much of the city, with Battersea recording ‘very high’, the top of the scale.

Elsewhere in the UK, Stockton-on-tees and Middlesbrough recorded high pollution readings and the forecast is for moderate and possibly high pollution in urban areas in northern England and Scotland on Tuesday. Other areas will have low pollution levels.