Microplastics exposure may be linked to higher rates of stroke, diabetes and high blood pressure in coastal communities, a new analysis suggests.
Microplastics are tiny synthetic plastic particles measuring less than 5mm. They have been found in oceans, drinking water, food supplies and human tissues.
The analysis found that areas with higher marine microplastic levels had higher rates of several chronic conditions than areas with lower exposure.
Researchers conducted a cross-sectional analysis of 709 coastal census tracts within 200 metres of the shoreline.
A cross-sectional study looks at information from a group of people at one point in time, meaning it can show links between factors but cannot prove cause and effect.
The team linked marine microplastic measurements from the National Oceanic and Atmospheric Administration with chronic disease estimates from the CDC PLACES database.
The researchers examined links between microplastic exposure and cardiometabolic health, which refers to conditions affecting the heart, blood vessels and how the body processes energy.
To minimise confounding, where other factors may affect the results, investigators adjusted their analysis for 154 demographic, socioeconomic and environmental variables.
These included age, sex, race, median household income, insurance coverage, Social Vulnerability Index scores and exposure to fine particulate air pollution, known as PM2.5.
After adjustment, areas with the highest microplastic exposure had significantly higher rates of several chronic conditions than areas with low exposure.
The strongest association was seen for stroke, with a prevalence ratio of 1.21 and a 95 per cent confidence interval of 1.13 to 1.29.
This means stroke was more common in those areas, although the study cannot show that microplastics were the direct cause.
Higher exposure was also associated with diabetes, with a prevalence ratio of 1.17 and a 95 per cent confidence interval of 1.10 to 1.24.
It was also associated with hypertension, or high blood pressure, with a prevalence ratio of 1.10 and a 95 per cent confidence interval of 1.06 to 1.14.
The researchers also used machine learning methods, including XGBoost and SHAP, to examine which factors were most strongly linked with stroke prevalence.
Machine learning is a form of computer analysis that can find patterns in large datasets, while SHAP is a method used to explain which factors influenced a model’s findings.
Microplastic concentration emerged as one of the most important environmental predictors of stroke prevalence in the analysis.
The finding suggests microplastics may contribute to chronic disease patterns independently of many established risk factors, although the study was not designed to prove causation.
The authors emphasised that the findings are observational, meaning they cannot determine whether microplastics directly cause stroke, diabetes or hypertension.
However, they said the results add to growing concern about the possible health impact of environmental microplastic contamination.
Further long-term and mechanistic studies, which examine how a process may work, will be needed to understand how microplastics may influence cardiovascular and metabolic health.
The authors also said more research is needed to explore whether reducing exposure could lower disease risk in vulnerable populations.
