Concerns that alarming reports of microplastic contamination in our environment, food, and even our bodies may be significantly overstated have been raised by a new scientific study, which points the finger at an unexpected source: the gloves worn by the researchers themselves.
A team from the University of Michigan has published evidence in the journal RSC Analytical Methods suggesting that common laboratory gloves are leaving behind microscopic residues that can be easily mistaken for plastic particles, potentially inflating counts by orders of magnitude.
The discovery originated from a separate project examining airborne microplastics in Michigan, where researcher Madeline Clough noticed inexplicably high particle counts during sample preparation. This prompted a forensic investigation into the lab’s own practices, ultimately leading to disposable nitrile and latex gloves.
Manufacturers coat these gloves with soap-like particles called stearate salts to make them easier to remove from their molds. According to the Michigan team, led by Professor Anne McNeil and Madeline Clough, these tiny salts are the hidden culprits.
How a soapy residue mimics a plastic pollutant
The core of the problem lies in the tools scientists use to identify microplastics. Techniques like Fourier-transform infrared (FTIR) and Raman spectroscopy work by shining light on a particle and reading its unique vibrational signature—a kind of chemical fingerprint.
Stearate salts, the study explains, share a strikingly similar chemical structure to polyethylene, one of the world’s most common plastics. Because their structures are alike, they interact with light in an almost identical way, producing near-matching fingerprints that standard analysis struggles to tell apart.
“Our team found that, even when following established protocols, using certain methods to measure environmental microplastics can potentially contaminate the results,” Professor McNeil and Clough wrote. The consequence, they state, is that “much of this research may be overestimating the number of microplastics.”
The scale of potential overestimation is significant. One experiment cited in the research found that mere contact with a gloved hand could produce false positives at a rate of 2,000 particles per square millimetre. A separate finding indicated that plastic counts in air samples could be inflated by over 1,000 times due to this contamination. Madeline Clough described the fundamental challenge as “searching for the needle in the haystack, but there really shouldn’t be a needle to begin with.”
The researchers are clear that their findings do not negate the pervasive reality of plastic pollution. “We may be overestimating microplastics, but there should be none. There’s still a lot out there, and that’s the problem,” Professor McNeil stated. Microplastics have been confirmed in rivers, soil, Antarctic ice, and human blood, placenta, breast milk, and brain tissue, raising legitimate health concerns.
However, the study underscores a critical methodological flaw that has largely escaped suspicion until now. It highlights the broader difficulties in microplastic science: a lack of standardised methods, the complexity of environmental samples, and the limitations of even advanced analytical techniques.
As a direct recommendation, the Michigan team advocates for laboratories to switch to cleanroom gloves, which are manufactured without stearate coatings and shed far fewer particles. They also note that the field is becoming more aware of contamination risks, with labs increasingly using multiple analytical techniques on the same sample to cross-check results.
The study, supported by the University of Michigan’s Meet the Moment Research Initiative, concludes that the scientific community must now develop robust, contamination-free standard operating procedures, particularly for analysing microplastics in sensitive human tissues, to ensure the accuracy of future findings.