People exposed to air pollution levels even within Britain’s guidelines were found to have changes in the structure of the heart, similar to those seen in the early stages of heart failure, according to a new study released by the Queen Mary University of London.

Researchers analyzed data from about 4,000 participants in a previously conducted UK Biobank study. The volunteers provided a range of personal information, including their lifestyles, health record and details on where they have lived. They also had blood tests and health scans, and heart MRI (magnetic resonance imaging) was used to measure the size, weight and function of the participants’ hearts at fixed times.

The team found that 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.

According to this study, average annual exposures to PM2.5 were well within UK guidelines (25µg per cubic metre), although they were approaching or past World Health Organization (WHO) guidelines (10µg per cubic metre).

“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,” said Nay Aung from Queen Mary University of London who led the data analysis.

“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,” Nay Aung added.