The hearts of people living in highly polluted urban areas could be up to ten times more polluted than those living in places with cleaner air, putting them at increased risk of heart disease, according to new research.

Scientists, led by Professors Barbara Maher of Lancaster University and Lilian Calderón-Garcidueñas of The University of Montana, examined the hearts of 72 people aged between three and 32. Sixty three of the hearts were taken from the victims of fatal road traffic accidents in heavily polluted Mexico City and the nine remaining hearts were ‘control’ hearts from people who had lived elsewhere.

All those hearts belonging to people who had lived in Mexico City contained much higher numbers of tiny particles (‘nanoparticles’) of pollution, from traffic (exhausts and brake systems) and industry.

The researchers also measured indicators of oxidative stress, to identify how much inflammation the heart tissues had been subjected to.

The heart nanoparticles were associated with damage to heart cells. The researchers also found evidence that many of these nanoparticles were strongly magnetic, posing particular potential risk of heart problems including:

· Generation of oxidative stress and chronic inflammation

· Potential for disruption of the heart’s electrical impulse pathways

· Hyperthermia; the damaging overheating of tissues as particles try to rotate in response to magnetic fields

· Potential disruption of cell membranes by magnetic particle rotation

The researchers say their findings provide a new way of understanding heart disease risks and underline the importance of urgent action on ‘particulate’ air pollution controls to protect human health.

Professor Barbara Maher said: “Exposure to this type of metal-rich nanoparticle appears to be directly associated with early and significant inflammation and cardiac damage. Identification of billions of strongly magnetic nanoparticles in the hearts of children and young adults provides an important new layer of information for understanding the development of cardiovascular disease.”

Iron-rich, strongly magnetic nanoparticles are abundant in particulate air pollution, created as a result of combustion and friction.

Exposure to air pollution is known to be associated with increased risk of cardiovascular and Alzheimer’s disease. But until now, little was known about the abundance of these metal-rich and magnetic nanoparticles in human heart tissue or what specific damage they could be causing, even in children and young adults.

Publishing in the journal Environmental Research, the international team showed how, using magnetic analysis and transmission electron microscopy (TEM), they found evidence of much greater numbers of this type of particle accumulating in the ‘urban’ hearts – between two and ten times as many.

The paper ‘Combustion- and Friction-Derived Magnetic Air Pollution Nanoparticles in Human Hearts’ described how most of the heart nanoparticles had a distinctive rounded shape, reflecting their high-temperature formation as ‘molten droplets’ from combustion and/or frictional processes, prior to their release as airborne pollution particles.

These damaging nanoparticles were present in many different cell structures in the left ventricle of the heart, even in the mitochondria – organelles crucial for supplying the energy needed for the heart to pump effectively. Co-occurring with the nanoparticles in the heart were abnormal mitochondria, damaged cell membranes and lipofuscin (a lipid-containing pigment, associated with ‘wear and tear’ or aging of cells).

Professor Lilian Calderon Garciduenas said: ”Exposure to iron-rich, combustion- and friction-derived nanoparticles is a modifiable risk factor for the development of cardiovascular diseases and this new evidence highlights the need for urgent progress in global efforts to reduce exposure to particulate matter air pollution and, specifically, to reduce and regulate the nanoparticles in air pollution.”

The international science team included the Universities of Montana (USA), Universidad del Valle de México (Mexico), Lancaster (UK), Oxford (UK), Virginia (USA), Universidad Nacional Autónoma de México (Mexico), the Instituto Nacional de Pediatría (Mexico) and the Indian Statistical Institute, Kolkata (India).

https://www.sciencedirect.com/science/article/pii/S0013935119303640

https://doi.org/10.1016/j.envres.2019.108567