Heart Remodeling Happens Even at Low Levels of Air Pollution

Residents of United Kingdom (UK) can undergo changes in the heart structure, similar to what is seen in the early stages of heart failure, even when exposed to low levels of air pollution that are well within the UK guidelines. However, the measured air pollution levels are fast approaching the limits placed by the World Health Organization (WHO). Numbers of WHO are much less than those set by the UK.

The research was conducted by a team of scientists, led from Queen Mary University of London by Professor Steffen Petersen, and was part-funded by the British Heart Foundation (BHF). It is published in the journal Circulation.

In England, air pollution is currently the largest environmental risk factor linked to deaths. Globally, air pollution is a contributor to coronary heart disease and stroke and accounts for approximately six in ten (58%) deaths. This research could give an insight as to how and why air pollution affects the heart.

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Study Findings

The team studied data from around 4,000 participants in the UK Biobank study.

They gathered a range of personal information (lifestyles, health record and where they have lived) from the volunteers.

This helped the team eliminate patients with underlying heart problems and those who had relocated house during the study.

Other tests done were blood tests and health scans like the heart MRI (magnetic resonance imaging) to measure the size, weight, and function of the participants' hearts at fixed times.

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Did Air pollution affect the Heart Structure?

Yes, there was a clear association between exposures to nitrogen dioxide (NO₂) or PM2.5 (small particles of air pollution) and the development of larger right and left chambers in the heart.

The degree of enlargement was similar to that seen in the early stages of heart failure.

The surprising things to note are that all the participants were healthy and had no prior symptoms; they all lived outside UK cities, and the association was seen only in the people living near the loud, busy roads in those suburbs.

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Did an Increase in Air Pollution Worsen the Condition?

Yes, more exposures to the pollutants caused more significant changes in the structure of the heart.

An increase by 1 extra microgram (μg) per cubic meter of PM2.5 and 10 extra μg per cubic meter of NO2 enlarged the heart by approximately 1%.

The average annual exposures to PM2.5 were 8-12μg per cubic meter in the study. Although this was well within the UK guidelines that have an exposure limit of 25μg per cubic meter, the study results are fast approaching or past WHO guidelines which are at 10μg per cubic meter, a much lower number than the UK limit. In fact, the WHO has said that there are no safe limits of PM2.5.

A similar situation was seen with NO₂ that was recorded at 10-50μg per cubic meter. This number was also approaching and above the WHO and UK annual average guidelines that are both at 40μg per cubic meter.

Significance of the study

The British Heart Foundation conducted the research ahead of the UK Government's consultation on their draft Clean Air Strategy closing on 14 August 2018 to make sure that the public's heart and circulatory health is at the center of discussions.

The Strategy would like to execute its mission of halving the number of people in the UK living in areas where PM2.5 levels exceed WHO guidelines by 2025, but the ultimate goal of the Strategy is 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 similar to blood pressure, cholesterol and weight by doctors and the general public when it comes to heart health.

The change should come from governments and public bodies who must act immediately to make all areas safe and protect the population from these harms.

Professor Jeremy Pearson, Associate Medical Director at the BHF said: "What is particularly worrying is that the levels of air pollution, particularly PM2.5, at which this study saw people with heart remodeling 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."

This step will also improve the lives of those currently living with heart and circulatory diseases that are proven to get affected by air pollution.

Reference:

1. Air pollution linked to heart remodelling - (https://www.bhf.org.uk/what-we-do/news-from-the-bhf/news-archive/2018/august/air-pollution-linked-to-heart-remodelling)

Source-Medindia