People with microplastics or nanoplastics in their carotid artery tissues were twice as likely to have a heart attack, stroke or die from any cause over the next three years than people who had none, a new study found.

Carotid arteries, which lie on each side of the neck and carry blood to the brain, can become clogged with fatty cholesterol plaques in a similar fashion as the arteries leading into the heart, a process known as atherosclerosis.

To date, our study is the first that associated the plastic contamination with human diseases,” said Raffaele Marfella, lead author of the study published Wednesday in the New England Journal of Medicine.

Our data must be confirmed by other studies and on larger populations,” said Marfella, professor of internal medicine and director of the department of medical and surgical sciences at the University of Campania Luigi Vanvitelli in Naples, Italy, in an email. “However, our study convincingly emphasize the presence of plastics and their relation with cardiovascular events in a representative population affected by atherosclerosis.”

Pediatrician Dr. Philip Landrigan, professor of biology at Boston College and director of the Program for Global Public Health and the Common Good and the Global Observatory on Planetary Health, said the study provided evidence that tiny plastics may be associated with cardiovascular disease cases in humans.

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

“Should exposure to microplastics and nanoplastics be considered a cardiovascular risk factor? What organs in addition to the heart may be at risk? How can we reduce exposure?” asked Landrigan, who was not involved in the new study.