Researchers have found that people exposed to air pollution levels well within UK guidelines have changes in the structure of the heart, similar to those seen in the early stages of heart failure. The research was part-funded by the British Heart Foundation (BHF) and is published in the journal Circulation. 
A team of scientists, led from Queen Mary University of London by Professor Steffen Petersen, studied data from around 4,000 participants in the UK Biobank study. Volunteers provided a range of personal information, including their lifestyles, health record and details on where they have lived, so the research team were able to remove patients with underlying heart problems, or those who had moved house during the study. Participants also had blood tests and health scans. Heart MRI (magnetic resonance imaging) was used to measure the size, weight and function of the participants' hearts at fixed times. 
Even though most participants lived outside major UK cities, there was a clear association between those who lived near loud, busy roads, and were exposed to nitrogen dioxide (NO2) or PM2.5 - small particles of air pollution - and the development of larger right and left ventricles in the heart. The ventricles are important pumping chambers in the heart and, although these participants were healthy and had no symptoms, similar heart remodelling is seen in the early stages of heart failure.
Higher exposures to the pollutants were linked to more significant changes in the structure of the heart. For every 1 extra μg per cubic metre of PM2.5 and for every 10 extra μg per cubic metre of NO2, the heart enlarges by approximately 1% .
Air pollution is now the largest environmental risk factor linked to deaths in England. Globally, coronary heart disease and stroke account for approximately six in ten (58%) deaths related to outdoor air pollution. This research could help explain exactly how and why air pollution affects the heart.
In the study, average annual exposures to PM2.5 (8-12μg per cubic metre) were well within UK guidelines (25μg per cubic metre), although they were approaching or past World Health Organisation (WHO) guidelines (10μg per cubic metre). The WHO has said that there are no safe limits of PM2.5. The participants' average exposure to NO2 (10-50μg per cubic metre) was approaching and above the equal WHO and UK annual average guidelines (40μg per cubic metre).
Ahead of the UK Government's consultation on their draft Clean Air Strategy closing on 14 August 2018, the British Heart Foundation want to ensure the public's heart and circulatory health is at the centre of discussions.
The Strategy commits to halving the number of people in the UK living in areas where PM2.5 levels exceed WHO guidelines (10 μg per cubic metre) by 2025, but ultimately the charity would like to see this action go further to reduce the health impacts of toxic air as quickly as possible.
Dr Nay Aung who led the data analysis from Queen Mary University of London said:
"Although our study was observational and hasn't yet shown a causal link, we saw significant changes in the heart, even at relatively low levels of air pollution exposure. Our future studies will include data from those living in inner cities like Central Manchester and London, using more in-depth measurements of heart function, and we would expect the findings to be even more pronounced and clinically important.
"Air pollution should be seen as a modifiable risk factor. Doctors and the general public all need to be aware of the their exposure when they think about their heart health, just like they think about their blood pressure, their cholesterol and their weight."
Professor Jeremy Pearson, Associate Medical Director at the British Heart Foundation, which part-funded the study said:
"We can't expect people to move home to avoid air pollution - Governments and public bodies must be acting right now to make all areas safe and protect the population from these harms.
"What is particularly worrying is that the levels of air pollution, particularly PM2.5, at which this study saw people with heart remodelling are not even deemed particularly high by the UK Government - this is why we are calling for the WHO guidelines to be adopted. 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.
"Having these targets in law will also help to improve the lives of those currently living with heart and circulatory diseases, as we know they are particularly affected by air pollution."
This research was a collaboration between Queen Mary University of London and the University of Oxford.
To request interviews or for more information please call the BHF press office on 020 7554 0164 (07764 290 381 - out of hours) or email firstname.lastname@example.org.
1. Association between ambient air pollution and cardiac morpho-functional phenotypes: Insights from the UK Biobank population imaging study, Aung et al. Published online in Circulation at 07.00 BST 03/08/2018. Please contact the press office for a copy of the manuscript.
2. Ejection fraction is used as a measure of heart function
3. BHF Advice on air pollution
How can I protect myself?
If you have a heart or circulatory condition, or a long-term lung condition, you should avoid spending long periods of time in places where there are high levels of air pollution. This includes roads with busy traffic, or places where air pollution is generated by industry, such as near factories.
If you do need to go to these places, try to avoid times of day when pollution might be higher. This includes going out during 'rush' hour, when people are travelling to and from work or taking children to and from school.
Is it safe to exercise outdoors?
Being physically active is very good for your heart, and for most people the benefits of doing exercise outweigh the risks of breathing in polluted air.
But if you have a heart or circulatory problem, or long-term lung disease, you should reduce the amount of exercise you do outdoors if the air pollution level is moderate, high or very high. This is because your body needs to take in more air when you are physically active and your heart is working harder, so you're likely to breathe in more polluted air. There is little evidence to say that using facemasks helps to keep out the harmful air pollution particles.
It is still a good idea to be as active as you can indoors on days when it's not possible to exercise outside.
How can I reduce my impact?
Walking or cycling short distances instead of driving can help to decrease air pollution. If you need to drive somewhere, think about sharing a lift with colleagues or a friend.
You can also avoid using diesel motor vehicles, because these cause especially high levels of pollution. If you need to buy or switch your vehicle, you could choose a petrol vehicle or ultra-low emission vehicle (ULEV).
If you own a diesel vehicle, do not remove the diesel particulate filter (DPF) on your exhaust, because it is illegal to modify a vehicle in this way. Make sure the DPF is maintained and regularly emptied, as it helps to protect you and others around you from potentially harmful emissions.
About the British Heart Foundation (BHF)
For over 50 years we've pioneered research that's transformed the lives of people living with heart and circulatory conditions. Our work has been central to the discoveries of vital treatments that are changing the fight against heart disease. But so many people still need our help. From babies born with life-threatening heart problems to the many Mums, Dads and Grandparents who survive a heart attack and endure the daily battles of heart failure. Every pound raised, minute of your time and donation to our shops will help make a difference to people's lives. For more information, visit bhf.org.uk