Recently, scientists found these teeny tiny pieces of plastic, called microplastics, in people’s arteries. Yep, like the same stuff you find in plastic bottles and bags.

They did this study in Italy, and it’s kind of a big deal because it’s the first time anyone has connected these microplastics to health problems in humans.

Microplastics, ubiquitous from Antarctica to human hearts, had not been definitively linked to measurable impacts on the human body despite their widespread presence. A groundbreaking study published in The New England Journal of Medicine by Italian researchers establishes the first-ever connection between microplastics in the human body and their impact on health, marking a significant milestone in understanding the risks posed by these particles.

“This is a landmark trial,” Robert Brook, a physician-scientist at Wayne State University who studies the relationship between cardiovascular disease and the environment, told Nature. (Brook was not involved in the study.) “This will be the launching pad for further studies across the world to corroborate, extend, and delve into the degree of the risk that micro and nanoplastics pose.”

The researchers looked at 257 participants who had surgery to clear out gunk from their neck arteries.

Polyethylene, the most widely-used plastic in the world, was detected in the “carotid artery plaque of 150 patients,” according to the study. “Electron microscopy revealed visible, jagged-edged foreign particles among plaque macrophages,” it continues, “and scattered in the external debris.”

People with these plastic bits were nearly five times more likely to have heart problems like heart attacks and strokes.

“It’s extraordinary,” cardiologist Eric Topol, who was not involved in the study, told USA Today of the findings. “I’m a cardiologist for three decades plus and I never envisioned we’d have microplastic in our arteries and its presence would accelerate arteriosclerosis.”

This study is just the beginning too. They haven’t totally figured out if the plastic bits are definitely causing the heart problems. It’s like they found a clue in a mystery book but haven’t solved the case yet.

“Although we do not know what other exposures may have contributed to the adverse outcomes among patients in this study,” Philip Landrigan, a Boston College pediatrician and epidemiologist, wrote in an editorial that accompanied the study’s release, “the finding of microplastics and nanoplastics in plaque tissue is itself a breakthrough discovery that raises a series of urgent questions.”

So, while it’s pretty eye-opening to find plastic in our arteries, there’s still a lot more detective work to do.

Scientists are scratching their heads and diving deeper to understand what this all means for our health.

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