This is according to new research by Britain's new car buying platform, What Car?
The survey of 839 motorists also found that nearly 40% of respondents' vehicles were not compliant with the rules of their city's clean air zones, with 18.2% saying they could not afford to pay the tariff required to drive in the zone, let alone to replace their vehicle.
Despite this, half of respondents living in cities with a clean air policy feel positively towards such schemes, with 38.6% feeling negative and the rest undecided. When the views of respondents who don't live in clean air zones are also taken into account, 31.9% feel positive about their introduction and 38.1% are negative.
London's ULEZ has now been expanded across Greater London, while while 11 other clean air zones are already in operation in cities around England and Scotland, including Bath, Birmingham, Bradford, Bristol, Gateshead, Glasgow, Newcastle and Sheffield.
What Car? editor Steven Huntingford said: "The fact that our survey suggests more than 18% of motorists living in clean air zones are being forced off the roads by these extra charges is deeply concerning, and shows that more financial help is needed to help people replace their vehicles. However, it's also clear that a large number of other people are supportive of the schemes, so this is a nuanced issue."