Nitrile and latex gloves, standard tools in scientific research, might be skewing microplastics data, according to a University of Michigan study. This discovery highlights how these gloves could inadvertently inflate microplastics levels in environmental samples.
Research conducted by the University of Michigan has revealed that particles from nitrile and latex gloves can contaminate lab tools used for analyzing air, water, and other samples. The contamination stems from stearates, substances that, while not plastics, resemble them in tests. This similarity may lead to misidentifying these particles as microplastics. To mitigate this issue, researchers Madeline Clough and Anne McNeil suggest using cleanroom gloves, which emit fewer particles.
Stearates are soap-like substances added to disposable gloves to aid in easy removal from molds during production. Their chemical likeness to certain plastics complicates lab analyses, raising the chances of false positives in microplastic pollution studies.
The researchers stress that this does not negate the reality of microplastic pollution.
“We may be overestimating microplastics, but there should be none,” said McNeil, a senior author of the study and a professor at U-M. “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.”
The research, spearheaded by Clough, a recent doctoral graduate, was published in RSC Analytical Methods with support from the U-M College of Literature, Science, and the Arts’ Meet the Moment Research Initiative.
Unexpected Source Behind Inflated Results
The investigation began during a collaborative project on airborne microplastics in Michigan, involving various U-M departments. Clough and McNeil, along with other researchers, collected air samples using metal-surfaced air samplers and analyzed them through light-based spectroscopy to identify the particles.
While adhering to standard practices, Clough wore nitrile gloves during the preparation of sampling surfaces. The analysis revealed microplastic levels thousands of times higher than anticipated.
“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 How Gloves Affect Microplastics Data
The team tested seven glove types, including nitrile, latex, and cleanroom varieties, under typical lab conditions, such as gloved hands handling filters and microscope slides. These routine interactions led to the transfer of particles from gloves to testing surfaces.
On average, gloves contributed around 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 better, emitting significantly fewer particles, likely due to their lack of stearate coatings, making them suitable for controlled environments.
Distinguishing Real Microplastics From False Positives
The researchers also investigated the possibility of visually differentiating real microplastics from stearate particles. Using electron and light-based microscopy, they found striking resemblances between stearates and polyethylene, a common plastic.
Despite this challenge, Clough and McNeil, alongside graduate student Eduardo Ochoa Rivera and statistics professor Ambuj Tewari, developed methods to separate real microplastics from glove-related contamination, potentially allowing more accurate analysis of existing datasets.
“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 underscores the crucial role of chemistry in microplastics research, particularly in identifying subtle differences between materials.
“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.”
Original Story at www.sciencedaily.com