A new study has linked microplastics to heart attacks and strokes. Here’s what we know 

Tiny flecks of plastic inside in the arteries may ramp up the risks of cardiovascular disease.

An analysis of artery-clogging plaques in 257 patients found that the presence of these microplastics was associated with a roughly quadrupled risk of heart attack, stroke or death, researchers report March 7 in the New England Journal of Medicine. 

The extent of that enhanced risk is “stunning,” says Aruni Bhatnagar, a cardiovascular researcher at the University of Louisville in Kentucky who was not involved with the work. When it comes to factors that drive cardiovascular disease, “very, very, very few things have that much of a risk.”

The study has gained attention worldwide and renewed concerns about the effects of plastics on human health. It’s also one of a growing number of reports that have found microscopic particles of plastic inside our bodies’ tissues, including the lungs, liver and blood (SN: 3/24/23).

But the question of whether these particles, called micro- and nanoplastics, actually harm people remains unanswered. The plaque study places the particles at the scene of the crime, Bhatnagar says, but there’s not enough evidence for an indictment just yet. Though the new results are “certainly cause for concern,” he cautions, “we have to be careful not to create mass hysteria.”

Science News spoke with toxicologists and cardiovascular disease researchers about the implications of the new study, the potential health effects of plastics — and how cautious we should be about making conclusions. Here are a few takeaways. 

Plastic is everywhere and enters our body through multiple routes 

When plastic toys, pipes, food containers and other objects inevitably break down over time, they can shed infinitesimal particles into our environment. Scientists have already documented how broadly these plastic smithereens have scattered.

Particles speckle even extreme locations, from the depths of the ocean to nearly the peak of Mount Everest (SN: 11/20/20). Microplastics, which are smaller than 5 millimeters (about the size of a peppercorn) and nanoplastics, which are roughly one five-thousandth that size, can get into our water, accumulate in soil and waft along whispers of wind.

These specks of plastic pollution can travel into our bodies via food and drink, the air we breathe and even directly through the skin. And our exposure to microplastics will only go up, says environmental toxicologist Matthew Campen, as old plastics deteriorate and enter the ecosystem and new plastic production continues to surge. In February, Campen’s team at the University of New Mexico in Albuquerque reported that all 62 human placenta samples tested contained microplastics. Unpublished work from his lab has also uncovered plastic in human brain and testicular tissue.

The plaque study adds to a rapidly emerging picture of how plastics may affect our health, Campen says. Scientists examined plaque samples from patients who had undergone surgery to clean out their carotid arteries, blood vessels in the neck that carry blood to the brain. “We found that more than half of patients had evidence of at least one type of plastic,” says study coauthor Francesco Prattichizzo, a cardiovascular researcher at IRCCS MultiMedica in Milan. 

These patients’ plaques all contained polyethylene, a ubiquitous material used in everything from cling wrap to cutting boards. And in 12 percent of the patients, scientists also found polyvinyl chloride, or PVC. 

Of 150 people with evidence of these plastics, 30 died or experienced a nonfatal stroke or heart attack within roughly the next three years. That’s compared to eight out of 107 people whose plaques appeared to be plastic-free, the team reports.

“Are we supposed to be finding plastics in plaque? Heck no, it’s very bizarre,” says study coauthor Sanjay Rajagopalan, a cardiologist at Case Western Reserve University School of Medicine in Cleveland. The findings do raise all sorts of interesting questions, though, he says, namely — what’s the plastic doing there? 

It’s too early to say whether microplastics in the arteries can cause heart attacks

It’s possible that plastics inside the arteries drive inflammation, further kindling cardiovascular disease. Plaques embedded with plastic, for instance, tended to contain more inflammatory molecules than plastic-free plaques, Prattichizzo’s team found. But he’s cautious about making conclusions. The researchers did not prove that microplastics are harmful, Prattichizzo says. They simply exposed a link between plastics in plaques and poor outcomes in patients.

Studying plastics is notoriously tricky, says Juliette Legler, a toxicologist at Utrecht University in the Netherlands. Floating motes in the environment can sneak past scientists, potentially hitchhiking into experiments on a current of air — or a researcher’s glove. “Plastics are everywhere in our labs. They’re everywhere in the surgical unit, they’re everywhere in the hospital,” she says. “It’s so easy to contaminate our samples.”

Prattichizzo agrees. His team used cotton gloves and glassware for their experiments but “we cannot exclude fully that there was possible contamination.” That’s why it’s so important to replicate his team’s results, he says, and in even larger groups of people followed over longer periods of time. Prattichizzo also wants to figure out how to best assess people’s plastic exposure, perhaps using a questionnaire that digs into people’s lives and lifestyles. 

Though the new study’s link between plaque plastics and health outcomes seems clear, Legler says, confirming the team’s findings is essential — and could have great implications. A confirmation, she says, could mean that “reducing the amount of plastic in our environment would significantly reduce our chances of having a stroke [or heart attack].”

The plaque study offers yet another reason why it’s probably a good idea to reduce plastic use 

For Legler, Prattichizzo’s team’s results are a wakeup call. “We use too much plastic,” she says. People shouldn’t be unnecessarily alarmed, she says — but alarmed enough to demand action on curbing plastic use.  

And the responsibility for action shouldn’t fall squarely on individuals, Campen says. “We need action from governments all over the planet.” He wants to see research bodies like the National Institutes of Health figuring out how to get rid of the plastic waste we already have. 

Prattichizzo says he hopes his team’s new work captures the attention of funding agencies and inspires them to invest money in micro- and nanoplastics research. “Not all plastic is the same,” he says. It would be helpful to know, for example, whether some materials are more likely than others to cause harm. 

But harm to humans or not, plenty of environmental reasons to reduce our use of plastics already exist, Prattichizzo says. There’s no need to wait to find out whether they drive heart attacks, too.