Study finds common lab gloves may inflate microplastics counts

A new study from the University of Michigan suggests that nitrile and latex gloves commonly used by scientists could be causing microplastic levels in environmental studies to appear higher than they actually are.

Researchers found that particles from these gloves can unintentionally transfer onto lab tools used to analyze air, water, and other samples.

The contamination originates from stearates, soap-like, salt-based substances added to disposable gloves to help them separate during manufacturing. While not plastics themselves, stearates can resemble certain microplastics in testing, potentially leading to false-positive results.

To address this, U-M researchers Madeline Clough and Anne McNeil recommend the use of cleanroom gloves, which release far fewer particles.

McNeil emphasized that the study does not undermine the real threat of microplastics.

"We may be overestimating microplastics, but there should be none," she said. Clough added, "We're searching for the needle in the haystack, but there really shouldn't be a needle to begin with."

The research, led by Clough, a recent doctoral graduate, was published in RSC Analytical Methods and supported by the U-M College of Literature, Science, and the Arts' Meet the Moment Research Initiative.

Tracing the source of inflated results

The discovery arose during a collaborative project on airborne microplastics in Michigan, involving U-M departments of Chemistry, Statistics, and Climate and Space Sciences Engineering.

Clough and McNeil, working with faculty and students including chemistry professor Andy Ault and graduate students Rebecca Parham and Abbygail Ayala, collected air samples using metal-surfaced air samplers.

Light-based spectroscopy was then used to analyze particle types.

During preparation, Clough wore nitrile gloves as standard practice. However, initial results showed microplastics counts thousands of times higher than expected. "It led to a wild goose chase trying to figure out where this contamination could have come from," Clough said, eventually tracing it to the gloves.

Glove testing reveals widespread contamination

The team tested seven types of gloves, including nitrile, latex, and cleanroom varieties, under typical lab conditions such as handling filters, microscope slides, and other equipment.

The experiments showed that routine contact transferred particles from gloves to surfaces, introducing an average of around 2,000 false-positive signals per square millimeter.

Cleanroom gloves performed significantly better, releasing far fewer particles due to the absence of stearate coatings and their design for controlled environments.

Distinguishing real microplastics from false positives

Using scanning electron and light-based microscopy, the researchers found that stearates are visually almost identical to polyethylene, a common plastic. Clough and McNeil, along with graduate student Eduardo Ochoa Rivera and statistics professor Ambuj Tewari, developed methods to separate true microplastics from glove-related contamination, enabling scientists to revisit previous datasets for more accurate assessments.

"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 study highlights the critical role of chemistry expertise in microplastics research, especially in identifying subtle material differences. "This field is very challenging 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."