Researchers have found a possible link between high levels of microplastics in ocean waters near U.S. coastlines and an increased prevalence of stroke, coronary artery disease, and type 2 diabetes in nearby counties. The findings were published in a recent article in the Journal of the American Heart Association.
The study compared microplastic concentrations in coastal waters with county-level health data. After adjusting for factors like age, sex, access to healthcare, and local environmental and social vulnerabilities, the results showed that counties exposed to very high levels of marine microplastics had significantly higher rates of the three diseases than counties exposed to lower levels.
Plastics are widely used because they are cheap and versatile, but they also create long-lasting pollution. Over time, plastic waste breaks down into smaller particles known as microplastics and nanoplastics. While the environmental impact of plastic waste is well known, the effects on human health are still being studied. Some plastic chemicals, including phthalates and bisphenol A, are already known to interfere with hormone function and cause health problems. More recent research suggests that micro- and nanoplastics can damage cells by triggering inflammation, oxidative stress, and cell death. These particles may harm blood vessels, weaken heart function, and disrupt blood flow, all of which could contribute to heart disease.
Scientists have even detected microplastics in arterial plaque, raising new concerns about their role in cardiovascular disease. However, it is not yet clear how these findings apply to the population as a whole.
To explore this further, researchers analyzed data on ocean microplastic concentrations collected from 2015 to 2020. They focused on waters within 200 nautical miles of the U.S. coastline. Using this information, they estimated microplastic exposure for 152 U.S. coastal counties and grouped them by low, medium, high, or very high microplastic levels. Then, they compared these groupings with local rates of stroke, coronary artery disease, and type 2 diabetes from 2019 to 2020.
The researchers used statistical methods that adjusted for key factors including population size, age distribution, physician availability, and local climate vulnerability. They applied quasi-Poisson regression, a method suitable for this type of data, and used population weights to give more influence to counties with larger populations.
The findings were consistent. In counties exposed to very high microplastic levels, the average prevalence of diabetes was about 13%, compared to 11.2% in counties with low levels. Stroke and coronary artery disease also appeared more frequently in the high-exposure areas. After adjusting for all demographic and environmental factors, the study found that these counties still had a 5% to 6% higher prevalence of diabetes and artery disease, and around a 4% higher rate of stroke. The stroke results were close to the margin of statistical significance.
Regional trends added another layer to the findings. The Gulf of Mexico had the highest disease prevalence, while the Atlantic coast had the highest microplastic concentrations. Both patterns stood in contrast to the Pacific coast, which showed lower rates of both pollution and disease.
The study offers early evidence that higher marine microplastic pollution could be linked to increased rates of cardiometabolic disease in nearby populations. Potential exposure routes include seafood consumption, contamination of groundwater—which provides more than one-third of U.S. drinking water—as well as inhalation and skin contact along polluted coasts. Animal studies have shown that microplastics can cause vascular and metabolic damage, supporting the biological plausibility of these findings.
Still, the study has limitations. It is ecological and cross-sectional, meaning it cannot prove that microplastics cause these health problems in individuals. It also lacks direct measurements of human microplastic exposure and does not account for all types of plastic. Other unknown local factors and population movement could have influenced the results.
Despite these uncertainties, the study draws attention to a potential public health threat and calls for more research. Future studies should define clear exposure levels and examine how microplastics affect the body. In the meantime, policymakers are encouraged to strengthen efforts to reduce plastic pollution and protect coastal communities that depend on seafood and clean water.
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