New research links even low levels of air pollution with serious changes in the heart

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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 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%.

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).

Nay Aung who led the data analysis from Queen Mary University of London, UK, says: “Although our study was observational and has not 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 their exposure when they think about their heart health, just like they think about their blood pressure, their cholesterol and their weight.”

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 (10µg 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.

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