A survey of air quality in a Devon town has found that its pollution levels are higher than Plymouth, Exeter and even Bristol.
The council now has to draw up an action plan to improve air quality
There are now calls from residents of Crediton for action to be taken to improve the local environment.
Local people have long been campaigning for a bypass or a traffic relief scheme to stop through traffic clogging up the High Street.
The town mayor Charlie Hayden said local people are bound to be concerned.
He said: "The people in Exeter Road can't even open their windows, not just because of the noise of the traffic but also because of the dust and the air quality.
"We've been told that Crediton suffers an above average level of asthma and chest problems and this could be part of the reason."
The town's Exeter Road and High Street were both found to have unacceptably high levels of two pollutants and national air quality objectives are unlikely to be met.
The report's findings mean that the District Council will have to designate a formal Air Quality Management Area.
The council will now produce an action plan detailing measures to improve air quality and there are plans to set up an air quality steering group.
Councillor Jane Campbell, chairwoman of the community services committee, said: "This report and its recommendations are part of the council's ongoing commitment to improve air quality and the environment in mid Devon for all residents, but particularly those in the Exeter Road and High Street areas of Crediton."