GAO Examines Microplastics Sources, Health Concerns, and Policy Challenges
A new publication from the U.S. Government Accountability Office (GAO) examined the growing presence of microplastics in the environment and the human body, highlighting ongoing scientific uncertainty about their health effects while outlining recent federal efforts to better understand and reduce exposure.
According to the report, more than 24 million metric tons of plastic enter the environment globally each year. Larger plastic items gradually degrade into microplastics, defined as plastic particles smaller than 5 millimeters (mm). The smallest particles, known as nanoplastics, measure less than 1 micrometer (μm) and can cross the body's natural barriers after being inhaled, ingested, or absorbed through the skin, thereby entering organs, blood, and cells.
Studies have shown that microplastics can be taken up from soil and water into food crops, raising questions about the food safety and public health implications of dietary exposure to plastics.
How Microplastics Enter the Environment, Food
GAO identified vehicle tires, synthetic fabrics, plastic bottles, and paint as major sources of microplastics. For example, a 2024 study demonstrated the presence of plastic particles from tires in leafy greens. While plastic microbeads once used in products such as toothpaste and exfoliants were prohibited under the Microbead-Free Waters Act of 2015, the report noted that most environmental microplastics originate from the breakdown of larger plastic materials.
Microplastics have been detected in air, water, soil, and living organisms. They can carry contaminants including phthalates, per- and polyfluoroalkyl substances (PFAS), and heavy metals. Additionally, a growing body of evidence suggests microplastics can enhance the virulence, antimicrobial resistance, and biofilm formation of foodborne pathogens.
Although some studies have associated microplastics with adverse health outcomes, including increased cardiovascular risk in patients with arterial plaque containing microplastics, the GAO emphasized that scientists have not determined the extent to which microplastics directly cause health problems. Laboratory studies in mice have linked high levels of microplastic exposure to cognitive impairment, reduced testosterone levels, and other consequences.
The report also highlighted significant knowledge gaps, including the lack of standardized methods for measuring microplastics and challenges in scaling technologies capable of removing the smallest particles from public drinking water supplies.
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Federal Efforts to Minimize Microplastics Pollution, Exposure
Federal agencies have recently announced several initiatives to address these gaps. In 2026, the U.S. Environmental Protection Agency (EPA) added microplastics to its Sixth Contaminant Candidate List (CCL6) for potential future regulation under the Safe Drinking Water Act, and the U.S. Department of Health and Human Services (HHS) launched the Systematic Targeting of MicroPlastics (STOMP) program to measure and remove microplastics from the human body. Additionally, the U.S. Department of Agriculture (USDA) announced an initiative to strengthen domestic cotton production to reduce reliance on synthetic fabrics that contribute to microplastic exposure.
Future Opportunities and Challenges
GAO said opportunities to reduce exposure include developing portable technologies for real-time environmental monitoring, improving scalable water treatment technologies, and reducing the use of plastic products such as disposable water bottles. However, the report noted that widespread reliance on plastics, their global distribution through air and ocean currents, and the lack of standardized scientific methodologies remain significant challenges for policymakers.
