Too Small to See, Too Big to Ignore: The World Wrestles With a Plastic Problem

The science of micro- and nanoplastics (MNPs) crossed a threshold in 2025 that is difficult to walk back and sets the stage for some interesting and potentially uncomfortable discussions in 2026.

A landmark study published in Nature Medicine in February 2025 confirmed the presence of plastic particles - primarily polyethylene, in nanoscale, shard-like fragments - in human brain, liver, and kidney tissue. More troubling still, concentrations in 2024 cadaver samples were measurably higher than in comparable samples from 2016, suggesting that the body burden is not static, but accumulating.

Combined with research linking microplastic concentrations to dementia-affected brain tissue, as well as animal studies documenting neurological damage, blood-brain barrier penetration, and markers associated with Parkinson’s disease, we shifted in 2025 from asking whether plastics enter the human body to asking what they are doing once inside - as the assumption is that we are all exposed to MNPs at ever-increasing rates.

Bottled water - long marketed as a cleaner alternative - has emerged as a meaningful exposure vector, with a 2025 Ohio State University study finding that some bottled water brands contain roughly three times the nanoplastic load of treated tap water, largely attributable to the bottle and cap itself. Inhalation, ingestion, and dermal absorption are all documented pathways, and the smallest particles - those under one micron - are capable of crossing into the bloodstream and being transported by immune cells to distant tissues.

Research published in Science Advances in 2025 further demonstrated that ordinary contact between water and plastic surfaces generates additional particles through microbubble erosion, with no external force required.

A Milestone Mired in Regulatory Slow Motion

The publication of these recent scientific studies likely played a role in prompting the United States federal government to act. On April 2, 2026, U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin and U.S. Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. announced coordinated federal action on microplastics - the most comprehensive U.S. federal response to microplastics to date, combining regulatory prioritization with biomedical research. The announcement signals that what was until recently a largely scientific and advocacy conversation has entered a new phase: one with potential regulatory infrastructure, federal funding, and eventually, compliance implications for the chemical industry.

For the first time in the program’s history, the EPA is including microplastics as a priority contaminant group in its draft Sixth Contaminant Candidate List (CCL 6), now open for public comment. CCL 6 also includes pharmaceuticals as a group - another first - along with per- and polyfluoroalkyl substances (PFAS), disinfection byproducts, 75 individual chemicals, and nine microbes that may be present in public drinking water systems. The EPA is simultaneously releasing human health benchmarks for 374 pharmaceuticals, giving states, Tribes, and local water systems a critical new tool to assess risk when drug residues are found at concerning levels.

“For too long, Americans have vocalized concerns about plastics and pharmaceuticals in their drinking water. That ends today,” said EPA Administrator Lee Zeldin. “By placing microplastics and pharmaceuticals on the Contaminant Candidate List for the first time ever, EPA is sending a clear message: we will follow the science, we will pursue answers, and we will hold ourselves to the highest standards to protect the health of every American family.”

Inclusion on the CCL does not constitute regulation, but signals that the EPA acknowledges a substance warrants serious scientific attention and may be considered for future regulatory action. A 60-day public comment period opened upon publication of the draft CCL 6 in the Federal Register on April 6, 2026. However, some EPA detractors are not impressed with the additions to the CCL 6 list.

“Just dumping a load of new pollutants into the purgatory of EPA's long list of dangerous chemicals in drinking water without issuing new standards will do nothing to remove toxic chemicals from the tap water in millions of Americans' kitchen sinks,” said Erik D. Olson, senior strategic director of health for the Natural Resources Defense Council.

Indeed, the process to regulate a substance that has been added to the CCL takes an average of 9–12 years, with some substances having been on the CCL for nearly 30 years with no action. Manganese, 1,2,4-trimethylbenzene, cyanotoxins, legionella, and disinfection byproducts (DBPs) have been on the CCL since its inception in 1998, with no regulatory action, while PFAS, for example, were on the CCL for decades before the EPA finalized a regulation for six PFAS found in drinking water in 2024. Meanwhile, 2-aminotoluene, cylindrospermopsin, ethoprop, microcystins, molybdenum, permethrin, profenofos, tebuconazole, and tribufos were all on the CCL 5 list and on March 19, 2026, the agency published a determination not to regulate them. So, even when chemicals are added to the CCL, there is no guarantee that there ultimately will be a regulation.

One of the few things that might contribute to a faster timeline for U.S. federal regulation for MNPs is scientific research that provides documented evidence not only of MNPs accumulating in the human body but also provides proof that they cause or exacerbate disabling or fatal diseases and illnesses.

Causation: The Research Race to Prove Microplastics Harm

Microplastics generally form when plastics break into tiny particles, some so small they cannot be seen. But it's not just these particles that pose a hazard, it's also the chemicals they contain. They can become contaminated during production or after the plastic begins to break down. Chemicals such as bisphenol A (BPA), phthalates, and PFAS can leach out and be absorbed into the body.

The study that shifted the conversation from environmental to clinical, “Bioaccumulation of microplastics in decedent human brains,” was published in Nature Medicine in February 2025. Using pyrolysis gas chromatography–mass spectrometry, researchers confirmed the presence of MNPs in human kidney, liver, and brain tissue from cadavers collected in both 2016 and 2024. Brain tissues contained higher proportions of polyethylene compared to the liver or kidney, and electron microscopy revealed the brain MNPs as largely nanoscale shard-like fragments.

Plastic concentrations were not influenced by age, sex, race/ethnicity, or cause of death - but the time of death was a significant factor, with higher concentrations found in 2024 samples than in those from 2016. In other words, accumulation is measurably increasing over time and is effectively universal. The research also found that microplastic concentrations were higher in the brains of deceased patients who had been diagnosed with dementia compared to those without dementia.

“These results highlight a critical need to better understand the routes of exposure, uptake and clearance pathways and potential health consequences of plastics in human tissues, particularly in the brain,” wrote the study authors.

In an article published in the University of New Mexico Health Sciences News, lead study author Matthew J. Campen, Ph.D., MSPH, director, New Mexico Center for Metals in Biology and Medicine, made note of findings that not only were MNPs more prevalent in the brain than other organs, but they are also accumulating over time. “I never would have imagined it was this high,” said Campen, of the concentration of plastics in the brain. “I certainly don't feel comfortable with this much plastic in my brain, and I don't need to wait around 30 more years to find out what happens if the concentrations quadruple.”

But do the accumulating plastics cause or directly contribute to dementia or other human health conditions? Researchers continue to search for causation at the human population level. Despite compelling animal-model and in-vitro evidence linking MNP exposure to inflammation, oxidative stress, endocrine disruption, cardiovascular disease, and carcinogenesis, direct epidemiological proof of harm in humans remains elusive. This causation gap has slowed legislative and regulatory action.

“We've had compelling scientific evidence showing these chemicals are harmful for decades, so where is the legislation? It's created when laboratories can test for it reliably and affordably, or when enough states pass their own standards and force EPA to establish a federal baseline, or frankly, when litigation creates pressure,” said Cassidy Spencer, the materials and sustainability regulatory manager for 3E.

“For microplastics and pharmaceuticals, the barrier isn't scientific uncertainty about harm,” she added. “It's that we haven't standardized how to measure them, we're not sure [municipal] utilities can remove them cost-effectively, and regulators are hesitant to tackle pollutants that don't come from a single, identifiable source.”

Closing the Microplastics Science Gap

At the same time that Zeldin and Kennedy made their announcement, the Advanced Research Projects Agency for Health (ARPA-H) announced the launch of STOMP (Systematic Targeting of Microplastics), a nationwide initiative to build a comprehensive toolbox for measuring, researching, and removing MNPs from the human body. 

Campen was present when Zeldin and Kennedy announced the joint EPA and HHS initiative. In a post on LinkedIn, Campen voiced his support for STOMP, calling it “a highly strategic and transformational initiative” and stated that ARPA-H Director Alicia Jackson and her team deserve tremendous credit for synthesizing input from scientists around the country. 

“The state of the science is not yet strong enough to build policies around, so the targeted investment to improve the confidence in micro- and nanoplastics measurement and advance our understanding of health effects will have a rapid impact that facilitates federal decision-making,” said Campen.

The American Chemistry Council (ACC) has consistently worked to advance the science on microplastics, said Kimberly Wise White, Ph.D., vice president of regulatory and scientific affairs at the ACC. “Along with our counterparts around the globe, the plastic and chemical industries have supported more than 100 microplastic researchers worldwide, convened scientists to strengthen the body of research, and are contributing to research on standardized materials and methods, environmental behavior and human health,” she noted.

Additionally, she said, the ACC continues to call on Congress to pass the Plastic Health Research Act (PHRA), which would establish a coordinated federal-agency approach to microplastics research and support “sound, science-based policymaking.” People want clear answers on microplastics, she added, “and any drinking water monitoring program must address several existing hurdles, including developing clear definitions, ensuring adequate lab capacity, and standardizing sampling and testing methods to be used consistently across the country.”

Introduced in August 2025 by U.S. Representatives Haley Stevens (D-MI) and Frank Lucas (R-OK), the PHRA is a bipartisan bill to jumpstart national research into the potential health effects of plastic exposure.

“For too long, we've seen report after report detail how the number of microplastics in humans is on the rise, but we haven't seen studies reporting how this could be impacting human health,” said Stevens when the act was announced.

“Combating plastics pollution depends on sound scientific research that creates a strong foundation for developing innovative, sustainable solutions,” said Catherine Trinkle, vice president and deputy general counsel, Regulatory, Environmental, & Government Affairs, BASF Corporation, when the PHRA was introduced.

The act “helps to position the U.S. federal government as a leader in microplastics and nanoplastics research,” she added. “Through interagency coordination and collaboration with external stakeholders, this bipartisan bill will provide a greater understanding of these important issues.”

Look for the next article in our Microplastics 2026 series:

The Global Microplastics Regulatory Landscape in 2026: Active but Fragmented

Microplastics have been found in human blood, lungs, and brain tissue - and now, for the first time, the U.S. federal government is treating them as a priority threat. From the EU’s sweeping REACH restrictions already reshaping global supply chains, to landmark new U.S. federal initiatives and a wave of state-level regulations, to every part of the globe in between, the compliance landscape for chemical manufacturers is fragmenting fast. For industry, the window to get ahead of this patchwork framework is narrowing - and the stakes have never been higher.