We should not underestimate the prevalence of microplastics. They are everywhere—in our rivers, our lungs, and even in our blood. But researchers tracking this global pollution crisis may have inadvertently contaminated their research samples. The protective lab gloves they wear are shedding microplastic-like particles that tamper with their numbers.
The culprit, according to a University of Michigan study, is a soap-like residue used to pop disposable gloves out of factory molds. Even a light, dry touch sheds thousands of these false-positive particles onto lab equipment. Because this residue can produce a very similar vibrational signature to common plastics under a lab laser, scientists have been accidentally counting microplastics from their own lab gear as environmental pollution.
This hidden cross-contamination suggests that years of data on microplastics may now need a massive recount.
The Wild Goose Chase
Madeline Clough, a recent doctoral graduate in chemistry at the University of Michigan, set out to measure the atmospheric plastics Michiganders inhale daily. She worked with a collaborative team of chemists, statisticians, and engineers to capture airborne fragments. Clough followed every strict protocol. She wore nonplastic clothing, eschewed plastic lab tools, and prepped her collection plates inside a specialized, filtered chamber.
Yet, her results defied logic. Her instruments detected plastic counts in the air that eclipsed previous reports by a factor of over 1,000.
“It led to a wild goose chase of trying to figure out where this contamination could possibly have come from, because we just knew this number was far too high to be correct,” said Clough.
Clough and her team scrutinized every variable.
“Throughout the process of figuring it out—was it a plastic squirt bottle, was it particles in the atmosphere of the lab where I was preparing the substrates—we finally traced it down to gloves,” Clough added.
The protective laboratory gloves, universally recommended as a best practice in the scientific community, were the secret culprits.
An Accidental Impostor
Manufacturers coat disposable latex and nitrile gloves with stearate salts. These substances act as release agents, helping the gloves separate cleanly from their molds in the factory. When a researcher handles equipment, these salts transfer seamlessly to whatever they touch. The University of Michigan researchers mimicked typical lab handling across seven glove types. Across common nitrile and latex gloves, they found an average of roughly 2,000 false positives per square millimeter, with some glove types exceeding 7,000.
These transferred stearates pose no environmental threat. However, they share a striking structural resemblance to polyethylene, the most abundant plastic found in the wild. This similarity can mislead common automated identification workflows researchers rely on to identify synthetic polymers.
Scientists typically use vibrational spectroscopy to analyze samples. They bounce light off a microscopic fragment and measure how it interacts, creating a chemical fingerprint. Because stearates and polyethylene share nearly identical structures, their light signatures overlap, confusing automated detection systems.
The size of these rogue particles compounds the problem. The study found that most of the shed stearate particles measure less than five micrometers. Environmental scientists focus intensely on plastics in this size bracket because they easily breach cellular barriers and wreak havoc on human and ecosystem health.
Salvaging the Science
The startling discovery forces the field to adapt and overcome this issue. Clough and her senior author, chemistry professor Anne McNeil, now advise researchers to avoid standard stearate-coated gloves during sample handling when possible, and to switch to cleanroom gloves when gloves are necessary. When harsh chemicals or biological materials make bare hands too dangerous, the team recommends adopting specialized cleanroom gloves. These alternatives lack stearate coatings and leave behind roughly 100 false positives per square millimeter, a dramatic improvement.
Fortunately, scientists do not need to discard all their previous work. Working alongside statistics experts, Clough and McNeil engineered new analytical methods that differentiate the nuanced chemical fingerprints of true microplastics from glove residue.
“For microplastics researchers who have these impacted datasets, there’s still hope to recover them and find a true quantity of microplastics,” said Clough.
The University of Michigan team ultimately discarded their initial atmospheric data, but they view the setback as a step forward for environmental chemistry. The revelation ensures future pollution metrics remain as accurate and untainted as possible.
“It’s important to note that even if the microplastic abundance in the environment is lower than researchers originally thought,” McNeil said in The Conversation. “We plan to continue our research on Michigan’s atmospheric microplastic contamination—but this time without gloves.”
The study was published in the journal Analytical Methods.