Millions of patients are having to breathe toxic air in order to see their GP, a study has found.
A third of English people are registered at NHS surgeries in areas that breach global air pollution limits.
London has the highest number of people patients in polluted areas, but some of the worst affected areas were much further out.
It raises concerns for vulnerable people who are en route to see a doctor, especially those with asthmatic problems.
The Government is already under pressure to immediately tackle alarming pollution levels, which are estimated to cause 40,000 premature deaths a year in the UK.
Millions of patients are having to breathe toxic air in order to see their GP, a study has found
Nearly 18million patients are registered at surgeries in areas that exceed the World Health Organization (WHO) annual limit for PM2.5 air pollution, the report from UK100, a network of council leaders that campaigns on environmental issues, found.
PM2.5 refers to particles 30 times smaller than the average human hair, small enough to easily and quickly penetrate deep into the lungs, and enter the bloodstream.
Exposure has been linked to heart disease, stroke, lung cancer, cardiovascular disease, with emerging evidence showing impacts on low birth weight, diabetes and neurodegenerative diseases such as Alzheimer's and Parkinson's.
London has by far the biggest numbers out of all regions – with 7.5million patients attending a surgery that breaches WHO air pollution limits, representing three quarters of the GP population.
This is followed by East Midlands and East of England, with the North East in last position, with 0 per cent of patients.
Birmingham has the most numbers of patients at toxic GP surgeries in one authority, with nearly half a million patients registered in areas that exceed WHO air pollution limits.
This is followed by a number of London boroughs including Lambeth, Newham and Wandsworth.
Other regions with significant issues are the East Midlands with over 2million patients, the East of England with 2.5 million patients and the South East with 2.3million patients.
Polly Billington, UK100 director, said: 'GP surgeries in Barrow in Furness, Lowestoft, Penzance, Ipswich and Portsmouth have the worst levels in the country of pollution.
'Some of the most vulnerable groups of people including young children and older people will walk to their GP, often to get help with respiratory conditions like asthma and bronchitis.
'We need urgent action from the Government with a new Clean Air Act passed by parliament to tackle toxic fumes.'
The UK’s air pollution was labelled a 'national embarrassment' in September.
Figures for 2017 showed 37 out of 43 air quality zones across the UK had illegal levels of nitrogen dioxide pollution, the same number as the previous year.