Higher ocean microplastics linked to more diabetes, stroke, and heart disease

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Jun 19 2025

Could the plastic in our oceans be quietly harming our hearts? A nationwide study reveals a concerning correlation between marine microplastic pollution and cardiometabolic diseases in US coastal communities.

Study: Marine Microplastic Levels and the Prevalence of Cardiometabolic Diseases in US Coastline Counties. Image Credit: Tint Media / Shutterstock

In a recent article published in the Journal of the American Heart Association, researchers analyzed whether higher levels of marine microplastics in ocean water near US coastlines are linked to greater county-level prevalence of stroke, coronary artery disease, or type 2 diabetes.

After adjusting for local vulnerabilities and demographic factors, coastal counties with very high levels of microplastics had significantly higher prevalences of all three conditions than those with low levels.

Background

Plastics have become deeply embedded in modern life due to their affordability and versatility; however, their widespread use has also led to severe environmental pollution. Disposed plastic waste often breaks down into tiny particles called microplastics and nanoplastics through the process of weathering and degradation.

While the environmental impacts of plastic pollution are well-documented, its direct effects on human health are still being explored. Concerns have grown over the health risks associated with chemicals in plastics, such as phthalates and bisphenol A, which are known to disrupt hormone function and cause other health issues.

More recently, micro- and nanoplastics have been shown to cause cell damage by inducing inflammation, oxidative stress, and even cell death. Early studies suggest that high levels of these tiny plastic particles may lead to changes in blood vessels and the heart, including damage to blood vessel linings, reduced heart function, and abnormal blood flow, which can contribute to heart disease and related conditions.

Additionally, microplastics have been found in artery plaques, raising the possibility that they increase the risk of cardiovascular problems. However, it remains unclear how these findings affect entire populations.

About the study

This study was designed to fill an important research gap by assessing the relationship between ocean microplastic pollution near US coastlines and local rates of major cardiometabolic diseases.

To investigate this link, the researchers utilized ocean microplastic concentration data spanning the years 2015 to 2020. They mapped microplastic levels within 200 nautical miles of the US coastline, aligning with the United Nations’ definition of exclusive economic zones where coastal nations manage ocean resources.

They identified 152 US counties bordering these coastal waters and calculated the average microplastic levels for each of these areas. Counties were then grouped into four categories: low, medium, high, or very high microplastic levels and linked to county-level estimates for stroke, coronary artery disease, and type 2 diabetes from 2019 to 2020.

To account for other factors influencing health, they included demographic details such as sex and age, physician availability, and broader social, environmental, and infrastructure vulnerabilities, using tools like the Climate Vulnerability Index (CVI).

Statistical analysis involved quasi-Poisson regression, which is suited for data with overdispersion and non-normal distributions. Population weights were applied to ensure that counties with larger populations had appropriate influence.

Key findings

Counties bordering ocean waters with very high microplastic concentrations had significantly greater average rates of stroke, coronary heart disease, and type 2 diabetes compared to counties with low microplastic levels.

Specifically, the mean prevalence of diabetes was about 13% in areas with very high microplastic levels, compared to 11.2% in areas with low levels. Likewise, stroke and coronary heart disease were also more common where microplastic pollution was greatest.

Statistical models confirmed this trend even after adjusting for key factors like sex, age, ethnic and racial composition, healthcare access, and environmental and socioeconomic vulnerabilities. In the fully adjusted models, very high microplastic levels were associated with a 5% to 6% higher prevalence of diabetes and artery disease, and about a 4% increase for stroke compared to low-level areas (with the finding for stroke being on the margin of statistical significance).

Regional patterns also emerged. The prevalence of all three diseases was highest in counties along the Gulf of Mexico, while the highest microplastic concentrations were measured off the Atlantic coast, both in contrast to the Pacific coast, which had lower disease rates and microplastic levels.

Conclusions

This ecological study provides population-level evidence that higher marine microplastic pollution may be associated with a greater burden of cardiometabolic diseases in US coastal regions.

Proposed pathways include contamination of seafood and groundwater, which supplies about 35% of U.S. drinking water, as well as possible inhalation or skin contact near polluted shores. Experimental studies and animal models back the plausibility of microplastics causing vascular damage, inflammation, and metabolic disruption.

However, limitations exist: the analysis is ecological and cross-sectional, so individual cause-and-effect relationships cannot be confirmed. There was also no direct measurement of human microplastic exposure or detailed analysis of different plastic types. Population movement, other confounding factors, and variations in local pollution controls could have influenced results.

Despite these gaps, the study highlights a concerning environmental health risk and underscores the need for further research to establish clear exposure thresholds and elucidate the underlying biological mechanisms. Policymakers should consider stronger regulations to curb plastic pollution and protect communities that rely on seafood and coastal waters.