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High levels of microplastics in ocean water have been linked to a higher prevalence of cognitive and other types of neurologic dysfunction in individuals living in US coastal communities.

“Our study builds upon the emerging body of evidence linking microplastic exposure to neurotoxic effects by demonstrating a population-level association between marine microplastic pollution and increased prevalence of neurologic disabilities in coastal US counties,” Sarju Ganatra, MD, with Lahey Hospital & Medical Center, Burlington, Massachusetts, told Medscape Medical News.

The findings will be presented at the American Academy of Neurology (AAN) 2025 Annual Meeting in April.

Novel Data

Previous research conducted primarily in animal models and in vitro studies have shown that microplastics can cross the blood-brain barrier, induce neuroinflammation, and disrupt neurotransmitter balance. However, human epidemiological data on microplastics and neurologic function have been limited.

“Our findings contribute novel insights by establishing a statistically significant relationship between high microplastic exposure and increased rates of cognitive, mobility, self-care, and independent living disabilities, after adjusting for key confounders such as socioeconomic status, comorbidities, and air pollution levels,” Ganatra said.

The researchers examined marine microplastic levels across 218 coastal counties in the United States, dividing them into four groups based on marine microplastic levels in the nearby ocean surface.

Counties in the low group had 0-0.005 microplastic pieces/m³ of ocean water, the medium group had 0.005-1 pieces/m³, the high group had between 1 and 10 pieces/m³, and the very high group had ≥ 10 pieces/m³.

On average, counties with very high levels had more than 1000 microplastic pieces/m³ of ocean water, whereas those with low levels had fewer than 10.

The investigators then compared the prevalence of cognitive disability, mobility disability, self-care disability, and independent living disability in counties between very high and low marine microplastic levels.

The mean prevalence of cognitive, mobility, self-care, and independent living disability was significantly higher in counties with very high marine microplastics levels (15.2%, 14.1%, 4.2%, and 8.5%, respectively) than in those with low levels (13.9%, 12.3%, 3.6%, and 7.7%, respectively; P < .001).

After adjusting for demographic factors, socioeconomic vulnerabilities, access to healthcare and major comorbid conditions, the prevalence of all neurologic disabilities was significantly higher in counties with very high than in those with low marine microplastic exposure:

• Cognitive disability: 9% higher (adjusted prevalence ratio [aPR], 1.09; P < .001)
• Mobility disability: 6% higher (aPR, 1.06; P < .001)
• Self-care disability: 16% higher (aPR, 1.16; P < .001)
• Independent living disability: 8% higher (aPR, 1.08; P < .001) 

An Independent Risk Factor?

“The strength of these associations suggests that microplastic exposure could be an independent environmental determinant of neurologic disability at a population level,” Ganatra told Medscape Medical News.

“While causation remains to be established, these findings reinforce the urgent need for environmental policies aimed at reducing plastic pollution and further exploration of the neurologic consequences of microplastic exposure. Addressing this issue is not just about protecting ecosystems, but also about safeguarding public health and cognitive function for future generations,” Ganatra added.

Commenting on this research for Medscape Medical News, Matthew J. Campen, PhD, regents’ professor, Department of Pharmaceutical Sciences, The University of New Mexico, Albuquerque, New Mexico, noted that “While there are still far too many unknowns connecting environmental exposures, human uptake, and ultimate health effects, this study offers glimpse of where we need to go as a field in the coming years.”

Campen also emphasized that although many uncertainties remain regarding the links between environmental exposures, human absorption, and health outcomes, this study provides valuable insight into the direction future research should take.

“Linking exposures to health outcomes in larger population studies will be critical to understanding the broader public health issues caused by lax waste management policies,” Campen said.

In a study published last month in Nature Medicine, Campen and colleagues found that accumulations of microplastics and nanoplastics in the brain increased from 2016 to 2024 and were found in higher levels in the brain than in other organs.

However, Campen cautioned that clinicians “should not be encouraging people to undergo any dramatic change of lifestyle to avoid plastics because you want to preserve health and the best guidance for whatever issue is at hand. We really need to reinvest time and effort to understanding the pathway of these nanoplastics getting into our bodies.”

The study did not receive any commercial funding. Ganatra and Campen had no relevant disclosures.