A significant oversight in microplastics research may have been skewing pollution data for years, according to researchers at the University of Michigan who discovered that standard laboratory gloves introduce thousands of false positives into environmental samples.
Chemistry graduate student Madeline Clough made the discovery while examining microplastics in Michigan's atmosphere. When she analyzed air samples collected on metal substrates using light-based spectroscopy, the results showed contamination levels many thousands of times higher than expected.
"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," Clough stated in a university press release. After eliminating potential sources including plastic bottles and airborne laboratory particles, the team traced the contamination to an unexpected culprit: disposable gloves.
The discovery proved particularly troubling because wearing gloves is recommended by all current literature in the microplastics field. The contamination stems from stearates, salt-like or soap-like particles that manufacturers apply to disposable gloves to facilitate removal from production molds. These stearates are chemically similar to microplastics at a structural level and appear nearly identical under standard analysis methods.
To determine the scope of the problem, the research team designed experiments testing seven different types of gloves, including nitrile, latex, and cleanroom varieties. They simulated every point of contact that would occur in a typical research environment, from filters to microscope slides. The results revealed that standard gloves impart approximately 2,000 false positives per square millimeter of contact area.
"If you are contacting a sample with a gloved hand, you are likely imparting these stearates that could overestimate your results," Clough explained.
The researchers found that cleanroom gloves, manufactured without stearate coating and designed for ultra-pure environments such as electronics manufacturing and pharmaceutical facilities, produced the fewest false positives. However, these specialized gloves cost two to five times more than standard medical or industrial gloves, presenting a financial barrier for many research programs.
Further investigation using scanning electron microscopy and light-based microscopy revealed that stearates are visually indistinguishable from polyethylene, the plastic they most closely resemble. This similarity has likely contributed to inflated microplastics estimates across numerous studies.
The research team, working with graduate student Eduardo Ochoa Rivera and University of Michigan statistics professor Ambuj Tewari, developed alternative analytical methods capable of differentiating between glove-derived stearates and genuine environmental microplastics. These techniques offer researchers the possibility of revisiting and correcting potentially contaminated datasets.
"For microplastics researchers who have these impacted datasets, there is still hope to recover them and find a true quantity of microplastics," Clough noted.
Chemistry and engineering Professor Anne McNeil, the study's senior author, emphasized the complexity of microplastics research. "This field is very challenging to work in because there is plastic everywhere," McNeil stated. "That is why we need chemists and people who understand chemical structure to be working in this field."
The findings, published in the journal RSC Analytical Methods, conclude with a direct appeal to the research community. The team urged microplastics researchers to adopt cleanroom gloves and implement additional precautions to prevent data contamination that could inadvertently exaggerate the severity of environmental microplastics pollution.
The implications extend beyond laboratory protocols. If standard gloves have been introducing thousands of false positives per square millimeter across the field, previous estimates of microplastics pollution in air, water, and other environmental samples may require significant revision. The discovery underscores the importance of rigorous contamination controls in environmental research and suggests that public alarm over microplastics pollution, while not unfounded, may have been amplified by methodological oversights.