Even low levels of air pollution may cause heart abnormalities similar to those seen during the early stages of heart failure, a study has warned.

UK research, published as the government consults on proposals for its Clean Air Strategy, tested 4,000 people and found those who lived near busy roads had larger hearts on average than those living in less polluted areas.

This comes despite the fact that the participants came from areas where pollution levels were below the UK guidelines.

Blood tests showed a clear association between people living on busier roads and increased levels or harmful nitrogen dioxide (NO 2 ) and small air particle pollution (PM 2.5 ) in their bodies.

Heart MRI scans were then used to test the organ’s function and structure and found higher pollutant exposure was associated with an increase in the size of the left and right ventricles.

While these people were not experiencing symptoms, the ventricles are the heart’s major pumping chambers and similar changes are seen in patients with the early stages of heart failure. Experts said the government had to do more rather than expecting people to move home to stay healthy.

“We saw significant changes in the heart, even at relatively low levels of air pollution exposure,” said Dr Nay Aung of Queen Mary’s University in London, who led the analysis.

This study was observational and cannot definitively determine which parts of pollution or other factors might be causing the heart changes. But Dr Aung says the public should be aware of their exposure when considering their general health, especially as air pollution is a major risk factor for cardiovascular disease.

Pollution is particularly important for those already living with some kind of heart or respiratory condition. This includes Mya Steer, 19, from Bristol who has an inherited heart condition, arrhythmogenic right ventricular cardiomyopathy, which was diagnosed just before she turned 18.

“My heart condition means that I often struggle to breathe anyway and air pollution makes me feel much worse – it’s pretty instant.

“This research just goes to show that pollution is affecting us all, whether we live in busy cities or more rural areas where we might feel ‘protected’ from pollution.”

The government’s consultation on its Clean Air Strategy closes this month, and commits to halving the number of people living in areas where PM 2.5 exceeds World Health Organisation guidelines by 2025.

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But critics have said the plan is "inadequate" and "underwhelming" while the WHO says PM 2.5 , microscopic airborne particles which can enter the lungs and worsen heart complaints should be cut entirely.

“There is no safe limit for air pollution for me, or for anyone who is concerned about their heart health – we all need the Government to do more,” Mya added.

The study, published in the journal Circulation, on Friday found that average PM2.5 exposures (around 8 -12µg per cubic metre) were within UK limits for what can be considered safe, under 25µg per cubic metre.

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Experts said it was therefore “particularly worrying” that the study found evidence of heart remodelling at UK acceptable levels.

“This is why we are calling for the WHO guidelines to be adopted,” said Professor Jeremy Pearson, associate medical director at the British Heart Foundation.

“They are less than half of UK legal limits and while we know there are no safe limits for some forms of air pollution, we believe this is a crucial step in protecting the nation’s heart health.