Fishing for clues to how air pollution affects the heart

Research into the effects of air pollution on heart health is growing as more people call for action on climate change around the world. One Manchester researcher has used her expertise in animal physiology to show how pollutants can have the same negative impact on human health as they do on marine life.

If you were asked to think about the impact of air pollution on human health, you might think about the lungs and respiratory system first. Yet it is becoming more apparent that poor quality air can affect many other parts of the body – particularly the heart.

Professor Holly Shiels, an animal physiologist at Manchester specialising in marine life, is one of the increasing numbers of researchers examining the effects of air pollution on the human cardiovascular system.

She is approaching the topic by looking at the similarities between the ways in which the hearts of vertebrate animals – including humans – become poisoned by the environment, otherwise known as cardiotoxicity.

Professor Holly Shiels

Holly is a Professor in the Division of Cardiovascular Sciences at the Faculty of Biology, Medicine and Health.

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From oil spills to air pollution

"My research has focused for a long time on the cardiovascular system in fishes and how the environment affects their heart function," she explains.

As part of this work, she conducted research at the site of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico to understand how the presence of oil affects the hearts of marine life such as tunas. She has also studied the effects of offshore oil rig leaks on the cod and halibut hearts in Norway (watch video).

These studies showed that the oil caused arrhythmias and cardiotoxicity in these fish. This led Professor Shiels and one of her colleagues at Bristol, Professor Jules Hancox, to wonder whether the cardiotoxic mechanisms are the same across vertebrates, and whether oil and petrol-based pollution could have similar effects on the cardiovascular systems of these organisms.

Funded by the British Heart Foundation (BHF), Professor Shiels and her team started to look at the evidence for interactions between heart disease and polycyclic aromatic hydrocarbons (PAHs), chemicals that naturally occur in fuels like oil, but that are also produced when these fuels and other substances like tobacco are burned.

They were particularly interested in PAHs like phenanthrene, because it is found at high levels in both the gases and particles (particulate matter - PM) found in air pollution. PM 2.5, which is a relatively small size, is associated with poor human health, including worsened lung and heart conditions.

So far, Professor Shiels and her team have conducted several reviews of the current epidemiological, clinical and experimental evidence linking pollution with cardiovascular dysfunction. These reviews have shown, among other findings, that because of similarities in cardiac function among animals at a molecular level, fish exposed to PAHs from oil spills could offer significant insights into the human health impacts of air pollution involving PAHs and PM.

"The PM itself is coated in the same PAHs that were loose in the water in the Gulf oil spill," Professor Shiels says. "Working out why fish were dying in oil spills has really given us clues to the pathways that are cardiotoxic for humans in air pollution."

Joining the dots

An emerging strand of Professor Shiels' research, led by two BHF PhD students, focuses on the effects of long-term exposure to low levels of air pollution on mammalian hearts and human-derived induced pluripotent stem cells.

While air quality has improved over the years, the number of hospitalisations and other health issues resulting from air pollution has continued to increase. Globally, air pollution prematurely kills seven million people every year, according to the World Health Organization.

Our expanding knowledge of cardiotoxicity mechanisms means we are now better able to attribute specific ailments to air pollution, Professor Shiels explains, referencing research by Dr Mark Miller of the University of Edinburgh, an expert on the cardiovascular effects of air pollution.

"Scientists and healthcare professionals can now better join the dots between the two things, which makes air pollution seem like such a huge health issue now," she says. "It's probably always been a huge issue, but we just haven't connected it as well in the past."

The flipside of this is that we may have been measuring the wrong things since air quality began to be monitored in the 1970s. While levels of some known air pollutants have fallen over time, scientists only began recording the smallest pollutants – ultrafine particles – relatively recently.

"Our current measurements may show that some air pollution categories are improving, but as we work to reduce those further, we could be allowing other pollutants to increase," Professor Shiels explains. "People are working to try to identify how true that is, but certainly that does seem quite probable."

Working together at Manchester

The good news is that researchers here at Manchester are among the first in the world to successfully measure levels of ultrafine particles. Experts at the Manchester Institute of Biotechnology (MIB) are looking at this type of measurement from a nanoplastics perspective – another important health issue for both humans and wildlife

"We have had a very successful collaboration with Holly using infrared microscopy to study fish and turtle hearts," explains Professor Peter Gardner of the MIB.

"With our new high-resolution system, we can now look at nanoparticle plastic contamination in a way that was simply not possible before."

This research is one of the first studies to show microplastics embedded in the heart tissue of a loggerhead sea turtle. The turtle may have drowned in fishing wire, showing the impact of microplastics - and therefore the compounds they carry, including PAHs - on our environment. 

Manchester's expertise in areas like this makes it an attractive place to conduct research into the health impacts of pollution and climate change, Professor Shiels says. The city is home to research hubs like the Manchester Environmental Research Institute, the Sustainable Consumption Institute and the Manchester site of the Tyndall Centre for Climate Change Research. 

In addition to this, researchers from all three Faculties at the University are coming together to hold events like the New and Emerging Organic Pollutant Analytics Symposium, showcasing research strengths in new and emerging organic pollutants across the institution.

"You can really get a sense of how Manchester can make a big difference through our collective expertise across social sciences, biomedicine, environment, atmosphere and imaging technology," Professor Shiels says. "It is one of the great advantages of working at The University of Manchester."