Coastal US counties with the highest concentrations of marine microplastics had increased rates of stroke, diabetes and heart disease compared to counties with lower levels, researchers have found.
The study examined 152 coastal counties and found a 9 per cent stroke rate among adults with an average age of 43 in areas with the greatest number of microplastic particles in nearby waters.
Microplastics are plastic fragments smaller than 5 millimetres – about the size of a pencil eraser – formed when larger items such as bags, bottles, and synthetic fibres break down.
They accumulate in oceans and are ingested by marine life, potentially exposing humans to harmful chemicals through seafood consumption.
The research, led by Lahey Hospital & Medical Center, used microplastic concentration data recorded from 2015 to 2020 across counties within 200 nautical miles of the US coastline. Counties were classified into four exposure levels: low, medium, high, and very high.
Public health data from the US Centers for Disease Control and Prevention and the American Community Survey were then used to analyse cardiometabolic disease rates.
Counties in the very high exposure group recorded diabetes rates of 18 per cent, heart disease rates of 7 per cent, and stroke rates of 9 per cent.
These patterns remained after adjusting for race, socioeconomic status, access to medical care and environmental factors.
Dr Sarju Ganatra, issenior author and medical director of sustainability at Lahey Hospital & Medical Center.
The researcher said: “Pathways such as contaminated seafood, drinking water, and even air inhalation could allow marine microplastics to enter the human body, making this a population-wide exposure risk with measurable health consequences.”
While studies linking microplastic exposure and chronic diseases are still emerging, researchers say there is growing evidence of potential biological harm.
These particles may trigger inflammation, oxidative stress and vascular injury – processes associated with diabetes and cardiovascular disease.
Ganatra wrote: “One study found individuals with microplastics in carotid plaques had a higher risk of myocardial infarction and stroke.
“Animal models demonstrate that microplastics induce insulin resistance, vascular inflammation, oxidative stress, myocardial injury – all of which are implicated in cardiometabolic diseases.”
The study assessed only marine microplastic levels.
Other sources such as drinking water and air pollution were not included.
Further research is needed to compare cardiometabolic disease rates in coastal and inland areas with varying levels of exposure.
Ganatra added: “The findings should ring alarm bells for all regions, given the pervasive presence of microplastics in our water, food, air, and packaging materials.
“These findings support a unified public health and environmental response – integrating climate action, pollution mitigation, and chronic disease prevention under a ‘One Health’ framework.”
