Living near an ocean polluted by microplastics may increase cardiometabolic disease risk

Living in a U.S. coastal county bordered by ocean waters with very high concentrations of microplastics may increase the risk of heart and metabolic diseases, such as type 2 diabetes, coronary artery disease and stroke.

This risk was higher compared to residents of coastal counties with low levels of microplastic pollution in nearby waters, according to research published in the Journal of the American Heart Association.

“This is one of the first large-scale studies to suggest that living near waters heavily polluted with microplastics may be linked to chronic health conditions. Plastic pollution is not just an environmental issue—it may also be a public health issue,” said Sarju Ganatra, M.D., senior author of the study, medical director of sustainability, vice chair of research in the department of medicine at Lahey Hospital & Medical Center in Burlington, Massachusetts, and president of Sustain Health Solutions.

Microplastics are tiny plastic particles less than 5 millimeters in size, the width of a new pencil eraser or smaller. Nanoplastics are even smaller, invisible to the naked eye, and measuring smaller than one-thousandth of a millimeter.

Both sizes of plastic particles come from the chemical breakdown (decomposition) of larger plastic waste, including food packaging (like single-use water bottles), synthetic fabrics and personal care products.

Micro and nanoplastics have been found in drinking water, seafood and the air. Seawater intrusion, which is a natural process where seawater mixes with groundwater resources, is reported extensively in coastal areas and results in a high concentration of various contaminants including microplastics in groundwater aquifers in coastal areas, according to the study.

In this study, researchers examined whether the concentration of plastic particles in ocean water near coastal communities was associated with a higher incidence of type 2 diabetes, coronary artery disease and stroke among residents in those counties.

Researchers examined concentrations of marine microplastic pollution (likely a combination of both micro- and nano-plastics) within 200 nautical miles of the counties, dividing the pollution levels into four categories based on mean marine microplastic levels (MML):

• low pollution (0–0.005 pieces/m³): described as almost nothing visible—maybe one tiny plastic speck in 200 bathtubs of ocean water;
• medium pollution (0.005–1 pieces/m³): up to 1 small plastic particle per 200 bathtubs of ocean water;
• high pollution (1–10 pieces/m³): likely to be a small handful of small plastic bits floating in each bathtub of ocean water; and
• very high pollution (10+ pieces/m³) every scoop of ocean water (about the size of a bathtub) could contain 10 or more plastic particles.

The analysis found that, compared to residents of U.S. coastal counties with low levels of microplastic pollution in nearby waters, those living in counties with very high levels of microplastic pollution had:

• 18% higher adjusted prevalence of type 2 diabetes, which is known to double the risk of heart disease;
• 7% higher for coronary artery disease, a buildup of plaque in the heart’s arteries that may lead to a heart attack or stroke; and
• 9% more strokes. A stroke happens when a blood vessel in the brain gets blocked or bursts. Strokes are the No. 5 cause of death and a leading cause of disability.

In addition, the analysis found that U.S. counties along the Gulf of Mexico (also known as the Gulf of America) and Atlantic coasts had a higher prevalence of type 2 diabetes, coronary artery disease and stroke compared to those on the Pacific coast.

The association between high microplastic pollution levels and more people with cardiometabolic diseases was consistent even after adjusting for age, gender, access to doctors, socioeconomic status (education, unemployment, household income, neighborhood status, etc.) and environmental considerations (air pollution, noise pollution, closeness to parks, walking space, etc.).

“While this study measured pollution in ocean water, pollution isn’t limited to the sea. Microplastics are everywhere: in drinking water, in the food we eat, especially seafood, and even in the air we breathe. So, while we examined data from microplastics collected from ocean water and the health status of people living in communities nearby, microplastic pollution affects all of us, regardless of where we live,” Ganatra said.

He said scientists are only beginning to understand the full impact of microplastics on health. “Ironically, even in health care—a field devoted to healing—we rely heavily on single-use plastics, from IV bags and syringes to gloves, tubing, medication blister packs and surgical drapes. Much of it ends up in landfills or the ocean, where it fragments into microplastics and enters the ecosystem,” Ganatra said.

“This study adds to a growing body of evidence that the garbage we discard into the environment often finds its way back to us. It’s time to shift from awareness to action,” he said. “We urge policymakers to view plastic pollution as an environmental crisis as well as a potential health crisis.”

Chair of the writing committee for the 2024 American Heart Association Scientific Statement: Environmental Exposures and Pediatric Cardiology, Justin Zachariah, M.D., M.P.H., FAHA, said “The authors conducted a very careful county-level analysis suggesting more data individual-level studies are needed to understand how plastic affects us and interventions to reduce those effects, or limits on micro- and nanoplastics in the environment.

“In the absence of such data or policies, transparency and labels about plastic content could empower consumers to make choices that are right for them. We must remember these plastics can indefinitely persist in our bodies, possibly subjecting persons at every age to accumulating risks throughout their lifespan.”

Zachariah, who was not affiliated with this study, is an associate professor of pediatric cardiology at Baylor College of Medicine and medical director of the cardiovascular clinical research core at Texas Children’s Hospital, both in Houston.

The study has several limitations. First, the association with microplastics compared county-level data rather than individuals. This type of study cannot prove a cause-and-effect relationship between nearby ocean microplastic levels (measured in water only, not in fish or plant life) and the development of cardiometabolic diseases.

“We also didn’t measure plastic levels in residents of these counties, and we don’t yet know the exact ways these particles may harm the body. So, while the findings are compelling, they should be a call for more in-depth research, not for making definitive conclusions,” Ganatra said.

Ganatra and colleagues say their findings point to several key areas for future research:

• How do microplastics get into the human body?
• At what levels do microplastics become harmful?
• Where do these particles accumulate in the body?
• How do microplastics affect long-term health?

The research team is currently designing follow-up studies to measure individual microplastic exposure through water, food and air, and to evaluate how exposure influences biological markers of inflammation and cardiovascular stress.

Study details, background and design

Using information from the National Centers for Environmental Information, marine microplastic concentrations were obtained and measured between 2015 and 2020 for the ocean waters within 200 nautical miles (the marine Exclusive Economic Zone) of 152 U.S. coastal counties along the Pacific Ocean, Atlantic Ocean and the Gulf of Mexico (also known as the Gulf of America).

The average age of the county residents was 43 years, and about half were female. About 75% were white adults, 13% Black adults, 1% American Indian and Alaska Native adults, 4% Asian American adults, 0.1% Native Hawaiian and other Pacific Islander adults, and the remaining 7% of adults did not self-identify their race or ethnicity.

County prevalence rates of type 2 diabetes, coronary artery disease and stroke were obtained from the 2022 Centers for Disease Control and Prevention’s Population-Level Analysis, which is based on the 2019–2020 Behavioral Risk Factor Surveillance System and the 2015–2019 American Community Survey.

Researchers compared the prevalence of diseases between counties with low vs. very high concentrations of microplastics, both with and without adjusting for several county-level risk factors, such as age, sex, race, ethnicity, access to physicians, and indicators of socioeconomic and environmental issues faced by people living in coastal communities.