While plastic pollution's grip on the natural world is undeniable, a growing chorus of scientists is raising serious doubts about the evidence for its health impacts inside the human body. High-profile studies that claimed to find micro and nanoplastics (MNPs) in organs like the brain, testes, and arteries are now being challenged, with critics pointing to potential contamination and flawed analysis.
A Field Under Scrutiny: Questioned Studies and Methodological Concerns
The Guardian has identified at least seven significant studies that have faced formal criticism in scientific journals, with a recent analysis listing 18 papers that may have confused human tissue signals with those of common plastics. The core issue lies in the extreme technical difficulty of detecting these minuscule particles at the very limits of current analytical technology.
Researchers express concern that the race to publish groundbreaking findings, sometimes by teams with limited analytical chemistry expertise, has led to rushed work where standard scientific checks were overlooked. There is no suggestion of malpractice, but the consequence could be misguided public health policies and regulations, experts warn.
One particularly contentious study, published in a top-tier journal in February 2024, reported a rising trend of MNPs in human brain tissue from postmortems spanning 1997 to 2024. By November, it was formally challenged. Dr Dušan Materić from the Helmholtz Centre for Environmental Research in Germany was blunt, calling the paper "a joke," noting that the brain's high fat content can produce false positives for plastics like polyethylene.
The 'Bombshell' of Unreliable Evidence
The doubts extend far beyond a single study. Research linking MNPs in carotid arteries to higher risks of heart attacks and strokes was criticised for not using proper 'blank' samples to measure background contamination. Another on plastics in human testes was said to lack a robust analytical approach. A study claiming 10,000 nanoplastic particles per litre of bottled water was labelled "fundamentally unreliable" by peers.
"This is really forcing us to re-evaluate everything we think we know about microplastics in the body. Which, it turns out, is really not very much," said Roger Kuhlman, a former chemist at Dow Chemical Company, who described the situation as a "bombshell."
A key technique, Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS), has come under fire. Dr Cassandra Rauert from the University of Queensland led a January 2025 study concluding the method is currently unsuitable for identifying plastics like polyethylene or PVC in human samples due to persistent interference from tissue fats. "I think a lot of the concentrations that are being reported are completely unrealistic," Rauert stated, questioning the biological plausibility of large microplastics crossing into the bloodstream and reaching organs.
Implications for Policy and Public Concern
The stakes are high. With global plastic production set to triple by 2060, understanding true human exposure is critical. Poor quality evidence risks both public scaremongering and providing ammunition for industry lobbyists to dismiss legitimate concerns. Dr Rauert warned of irresponsible claims, citing unproven and expensive 'detox' treatments advertised to clean plastics from blood.
Despite the controversies, some foundational work stands. Prof Marja Lamoree of Vrije Universiteit Amsterdam, senior author of a landmark 2022 study that first reported MNPs in human blood, defends her team's work against contamination claims, citing the use of fresh samples. However, she acknowledges the field's immaturity and the difficulty of analysing tissues from plastic-filled operating theatres.
The consensus among critics is not that MNPs are absent from our bodies, but that the true scale and location remain uncertain. Analytical techniques are improving rapidly, narrowing the uncertainty. "I think there is less and less doubt about the fact that MNPs are there in tissues. The challenge is still knowing exactly how many or how much," said Dr Frederic Béen, also of Vrije Universiteit Amsterdam.
For the public, experts advise a precautionary approach without panic. Simple steps like using a charcoal water filter, avoiding heating food in plastic, and ventilating homes can reduce exposure. The scientific community, meanwhile, is urged to collaborate and improve methodologies rather than engage in divisive disputes, to finally deliver clear, reliable answers on what plastic pollution is doing to us all.
