People who survived a serious heart attack were found to have higher levels of tiny plastic particles in their blood, providing early evidence that plastic pollution could be an overlooked cardiovascular threat.
Researchers at the University of Campania in Italy also found that people who smoke and those exposed to higher levels of air pollution had greater levels of micro- and nanoplastics in their blood.
The findings of the small new study add to growing evidence suggesting that tiny plastic particles affect heart health.
Scientists detected micro- and nanoplastics – tiny plastic fragments that shed from packaging, clothing and other everyday products – in the blood supplying the heart in 84 per cent of heart attack patients studied.
In comparison, only 40 per cent of patients with chronic ischemic heart disease and 32 per cent of patients with normal coronary arteries were found to have micro and nanoplastics, according to the study published in the European Heart Journal.
The team studied a small sample of 61 patients in Italy, recording whether each person smoked and how much air pollution they had been exposed to over the previous two years.
They took samples of the patients’ blood from the blood vessels supplying the heart and from other parts of the body.
Dr Pasquale Paolisso of Sant'Andrea Hospital, Sapienza University of Rome, the study's first author, said microplastics were now found "virtually everywhere in the environment, including the air we breathe, the water we drink, and many foods we consume".
“In recent years, scientists have begun to detect these particles in human tissues and organs, raising concerns about their potential health effects,” said Dr Paolisso.
However, “very little” is known about whether these tiny plastic particles are present in the blood flowing through the arteries that supply the heart, researchers say.
Smokers were six times more likely to have plastics in their blood, and those exposed to higher long-term levels of air pollution were more likely to have microplastics in their blood, according to the study.
Every patient who smoked and lived with higher air pollution had plastics in their blood, compared with one in eight of those who neither smoked nor faced dirty air. The researchers said the pattern suggested smoking and pollution may make it easier for the particles to pass from the lungs into the bloodstream.
Heart attack patients also seemed to have a greater variety of plastic types in their blood, with the most common type being polyethene – widely used in packaging.
However, the study stops short of establishing a causal connection between micro- and nanoplastics and heart attack.
“These findings do not prove that microplastics cause heart attacks, but they reveal a strong association between environmental exposures, microplastics in the blood and cardiovascular disease,” said Emanuele Barbato, an author of the study from Sapienza University of Rome.
“In our study, smoking history was strongly linked to microplastics in the blood. Our findings suggest that smoking might make it easier for micro and nanoplastics to enter the bloodstream via the lungs. Air pollution may act in a similar way,” Dr Barbato said.
Other researchers urged caution over how the plastics were measured.
Kevin Thomas, professor and director of the Queensland Alliance for Environmental Health Sciences at the University of Queensland, said the technique used could not reliably distinguish some plastics from natural fats in the blood.
"It is just as plausible that endogenous lipids [fats] in the blood are being misidentified as plastics," Professor Thomas said, telling the Australian Science Media Centre the headline "could just as well read 'Patients who suffer heart attacks have more lipids in their blood'".
Ian Shaw, emeritus professor of toxicology at the University of Canterbury, called it a well-conducted study but described it as a pilot given the small number of patients.
He said higher plastic levels in heart attack patients did not prove the particles caused the disease, since an unmeasured factor linked to the plastics could be responsible.
“Microplastics are likely to initiate an inflammatory response, as evidenced by raised biochemical inflammation markers in the study. This presents a credible mechanism for a link between microplastics and heart disease,” he said.
The finding that plastics also appeared in patients with healthy arteries pointed to how widespread exposure had become, Professor Shaw said.
Microplastics shed from packaging, car tyres, clothing, household products and personal-care items, and have become so widespread they now turn up in food, drinking water and air. People take them in by eating, breathing and through the skin.
Jeroen Douwes, professor of public health at Massey University, said the study focused on plastics breathed in, while diet was another major route into the body that might matter just as much for heart risk.
Professor Barbato said the results strengthened the case for treating plastic pollution as a health issue rather than only an environmental one.
"Policies that reduce air pollution, tobacco exposure and environmental plastic contamination could have benefits that extend beyond environmental protection and potentially improve cardiovascular health," he said.
Scientists unrelated to the study welcomed the findings showing a strong link between plastic exposure and heart conditions.
“While the findings do not prove that plastics directly cause heart attacks, they strengthen the growing scientific evidence that plastic pollution is an emerging public health issue deserving serious attention,” said Thava Palanisami, a plastic researcher at the University of Newcastle in Australia.
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