Microplastics are turning up not just in oceans and rivers but across the Northern Plains, from South Dakota’s prairie lakes to Montana’s mountain streams.
Regional studies confirm the presence of plastic fragments in water and soil throughout the interior U.S., though statewide counts remain scarce, and nanoplastics—particles less than one micron—are unmeasured.
Why it matters
A new JAMA review by Harvard researchers links rising exposure to plastic to potential human health effects, including cardiovascular and inflammatory diseases. Scientists say the Northern Plains could serve as an inland laboratory for measuring how airborne and waterborne plastics spread far from coastal sources, offering early evidence that microplastics are now part of the region’s environmental baseline.
The study, published Oct. 15, finds that microplastics—plastic fragments smaller than five millimeters—enter the body mainly through inhalation and ingestion. Researchers have found these particles in lungs, blood, and other organs, and their concentrations appear to be increasing.
Global problem, local implications
Plastics production has nearly doubled in two decades, rising from 234 million tons in 2000 to 435 million tons in 2020, and is expected to grow by another 70 percent by 2040. The JAMA report identifies 10 major chemical groups of concern—ranging from PFAS and bisphenols to phthalates and flame retardants—linked to toxicity and environmental persistence.
Microplastics have already been detected in South Dakota’s Lake Herman, Lake Madison, Lake Thompson, and Lake Henry, according to a Dakota State University project. South Dakota State University researchers are also tracking airborne plastic particles. Nebraska sediment samples from the Platte River and Montana watershed studies show similar contamination, mostly from microfibers shed by clothing and packaging.
Health signals emerging
The Harvard team notes growing evidence that microplastics and nanoplastics may contribute to cardiovascular disease and systemic inflammation. A 2025 Cureus review identified these materials as possible cardiovascular risk factors. Microplastics can also act as carriers for microbes and toxic metals, potentially amplifying harm, according to a 2024 study in Environmental Science and Pollution Research.
Policy and prevention
While some global agreements address plastic waste—such as the 2019 Basel Convention Plastic Waste Amendments and MARPOL Annex V—the United Nations’ proposed Global Plastics Treaty, under negotiation since 2022, aims to regulate plastics across their whole life cycle.
“International cooperation to limit plastic pollution and to find environmentally safe plastic alternatives is needed,” said study co-author Dr. David Christiani of the Harvard T.H. Chan School of Public Health.
