A new bus operated by one of the United Kingdom's largest public transportation companies has hit the streets in Southampton with the goal of driving down air pollution. The Go-Ahead Group says its Bluestar7 bus is the first in the UK to be fitted with a roof-mounted air filtration system that will suck up dirty air as it moves around the city before cleaning it and sending it back out. If the bus unveiled on Thursday is a success in Southampton, the company will roll the idea out nationwide.

David Brown, Go-Ahead Group's chief executive, told the Guardian newspaper the company wants to extend the technology to its entire fleet of more than 5,000 buses.

"We are going a step further in the potential for our buses to actively clean the environment," he said. "It's a huge development in our environmental leadership and we are also proud to be pioneering the prototype in the UK."

Brown said the company picked Southampton for its pilot because the World Health Organization said the city was on the borderline between safe and dangerous levels of air pollution. The British government has called on the city and four others with similar levels of air pollution to develop action plans to tackle the problem.

The Southern Daily Echo, a tabloid serving Southampton and the wider English county of Hampshire, noted that the company believes the filter will remove 99.5 percent of harmful particles.

With the WHO blaming air pollution for 4.2 million premature deaths a year worldwide, Andrew Wickham, managing director of Bluestar, said: "Cleaning the air in this way could lead to a number of lives being saved."

Brown said the company wants to demonstrate that buses can be a solution to both urban congestion and poor air quality. He said on the Today Program on BBC Radio 4 that a single bus-mounted air filter can scrub the equivalent of 25 Olympic-sized swimming pools of air in a year.

Britain's Department for Environment Food and Rural Affairs says bad air is shortening residents' lives by six months.

The filter is manufactured by Pall Aerospace, the world's largest aerospace and defense filtration company. Steve Simpson, the company's senior director of marketing, said it used aerospace technology on the project.

"Our team is proud of the results on the filtering bus project, and we are excited to see it in action," he said.