AUG 06, 2018 4:30 PM PDT

Changes in Heart Structure Linked to Air Pollution

WRITTEN BY: Caitlin Williams

According to the World Health Organization, 4.2 million deaths occur every year as a result of exposure to ambient (outdoor) air pollution. Of the world’s population, 91% live in places where air quality is above the WHO guideline limits. Ambient air pollution effects developed and developing countries, but low- and middle-income nations experience the highest burden. The highest toll of ambient air pollution occurs in the Western Pacific and South-East Asia regions. Air pollution is linked to stroke, heart disease, and chronic and acute respiratory disease such as asthma as well as lung cancer. A recent study published in Circulation shows that heart structure can change due to air pollution exposure, even within the guideline limits.

Ambient air pollution can affect urban and rural areas; contributing factors include transport, agricultural practices, industry and energy supply, household energy, and waste management. Pollutants can consist of sulfur dioxide, carbon monoxide, nitrogen dioxide, ground-level ozone, black carbon, and particulate matter composed of ammonia, nitrates, sulfates, and other compounds that can be inhaled. While most pollution is from local or regional sources, certain atmospheric conditions allow pollution to travel long distances and cross-national borders over the span of 4-6 days, requiring global cooperation to address flows and causes of air pollutants.

Of the many adverse health effects of ambient air, there is a strong association with increased cardiovascular morbidity and mortality. However, little is currently known on the influence of air pollutants on cardiac structure and function. The recent study led by Dr. Steffen Petersen, from the Queen Mary University of London, analyzed the effects of air pollution on heart structure and function in the United Kingdom. Data from 4,000 participants in the UK Biobank Study provided personal information such as lifestyle, health records, and past residences. Individuals with underlying heart problems, or who relocated during the study were removed. To measure heart size, weight, and function magnetic resonance imaging (MRI) was done, blood tests and health scans were also conducted at fixed times.

The results showed that individuals with higher exposure to pollutants showed more significant changes in the structure of the heart. The study found that 1 extra µg/cubic meter of particulate matter or 10 extra µg/cubic meter of nitrogen dioxide enlarged the heart by approximately 1%. There was also a clear association between individuals who lived near loud, busy roads and were exposed to nitrogen dioxide or particulate matter, with the development of larger right and left ventricles in the heart. While these individuals were healthy and showed no symptoms, this heart remodeling is similar to that seen in heart failure.

The average annual exposure of participants was 8-12 µg/cubic meter particulate matter, well within the 25µg/cubic meter guideline in the United Kingdom but at the threshold for WHO guidelines of 10 µg/cubic meter. Nitrogen dioxide average exposure was approaching or above both WHO and United Kingdom guidelines of 40 µg/cubic meter, with a 10-50 µg/cubic meter average. Dr. Nay Aung who led the data analysis 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.”

The study emphasizes the importance of considering air pollution when thinking about heart health, just as you would consider blood pressure or cholesterol. Governments and public groups must act to protect the population from air pollution harms, starting with adopting of WHO guidelines on acceptable air pollutant levels. Improvement will help promote heart health and improve the lives of those already living with heart and circulatory diseases that are particularly affected by air pollution.

To learn more about air pollution watch the video below!

World Health Organization

About the Author
  • Caitlin holds a doctorate degree in Microbiology from the University of Georgia where she studied Mycoplasma pneumoniae and its glycan receptors. She received her Bachelor's in Biology from Virginia Tech (GO HOKIES!). She has a passion for science communication and STEM education with a goal to improve science literacy. She enjoys topics related to human health, with a particular soft spot for pathogens.
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