The tools meant to detect microplastics—lab gloves—might be quietly skewing the results.

A new University of Michigan study suggests that nitrile and latex gloves, commonly used in labs, could be causing scientists to overestimate levels of microplastics.

Researchers found that these gloves can unintentionally contaminate the equipment used to analyze air, water, and other samples. The contamination comes from particles called stearates, which are not plastics but can closely resemble them during testing. Madeline Clough and Anne McNeil of U-M recommend switching to cleanroom gloves, which release far fewer particles.

Stearates are salt-based, soap-like substances. They are added to disposable gloves during manufacturing to help them separate easily from molds. However, because stearates share chemical similarities with certain microplastics, they can be misidentified during analysis, leading to false positives.

The researchers emphasize that microplastics pollution is still a real and serious issue.

“We may be overestimating microplastics, but there should be none,” said McNeil, senior author of the study and U-M professor of chemistry, macromolecular science and engineering, and the Program in the Environment. “There’s still a lot out there, and that’s the problem.”

Clough added, “As microplastic researchers looking for microplastics in the environment, we’re searching for the needle in the haystack, but there really shouldn’t be a needle to begin with.”

Led by Clough, a recent doctoral graduate, the study appears in the journal RSC Analytical Methods. Funding was provided by the U-M College of Literature, Science, and the Arts’ Meet the Moment Research Initiative.

Unexpected Source Behind Inflated Results

The investigation began as part of a collaborative effort to study airborne microplastics in Michigan. The project involved faculty and students from multiple U-M departments, including Chemistry, Statistics, and Climate and Space Sciences Engineering. Clough and McNeil worked with collaborators such as chemistry professor Andy Ault and graduate students Rebecca Parham and Abbygail Ayala to collect air samples.

To gather data, the team used air samplers equipped with metal surfaces that capture particles from the air. These collected particles were then analyzed using light-based spectroscopy to identify their composition.

Clough prepared the sampling surfaces while wearing nitrile gloves, following standard practices in the field. However, when she analyzed the results, the number of detected microplastics was 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 said. “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.”

Testing the Impact of Different Gloves

To understand how widespread the issue might be, the researchers tested seven types of gloves, including nitrile, latex, and cleanroom versions. They also evaluated commonly used methods for identifying microplastics.

Their experiments recreated typical lab interactions, such as a gloved hand touching filters, microscope slides, or other tools used during analysis. These routine contacts were enough to transfer particles from the gloves onto testing surfaces.

On average, the gloves generated about 2,000 false-positive signals per square millimeter.

“The type of contact we tried to mimic touches upon all varieties of microplastics research,” Clough said. “If you are contacting a sample with a gloved hand, you’re likely imparting these stearates that could overestimate your results.”

Cleanroom gloves performed much better, releasing far fewer particles. This is likely because they are made without stearate coatings and are designed for use in extremely clean environments.

Distinguishing Real Microplastics From Contaminants

The team also explored whether it is possible to tell true microplastics apart from stearate particles. Using scanning electron microscopy and light-based microscopy, they found that stearates are visually indistinguishable from polyethylene, a common plastic.

Despite this challenge, Clough and McNeil, working with graduate student Eduardo Ochoa Rivera and statistics professor Ambuj Tewari, developed analytical methods to separate real microplastics from glove-related contamination. These approaches may allow researchers to reanalyze previously affected datasets and obtain more accurate results.

“For microplastics researchers who have these impacted datasets, there’s still hope to recover them and find a true quantity of microplastics,” Clough said.

The findings also highlight the importance of involving chemists in microplastics research, as identifying subtle chemical differences is key to avoiding errors.

“This field is very challenging to work in because there’s plastic everywhere,” McNeil said. “But that’s why we need chemists and people who understand chemical structure to be working in this field.”