The pervasive problem of microplastic pollution may be even more widespread than previously thought, but not necessarily because of increased contamination. A new study from the University of Michigan suggests that common laboratory practices – specifically, the gloves scientists wear while collecting and analyzing samples – could be leading to a significant overestimation of microplastic levels in the environment.
Researchers found that disposable nitrile and latex gloves, routinely used to prevent contamination, actually introduce contaminants in the form of stearates – salts that resemble microplastics. These stearates, used to help peel gloves from their molds, can mimic the signature of plastic particles when analyzed with common detection methods, leading to inaccurate, and potentially inflated, counts. The findings, published in RSC Analytical Methods, don’t negate the serious threat of microplastic pollution, but highlight a critical need for methodological refinement in the field.
“We may be overestimating microplastics, but there should be none. There’s still a lot out there, and that’s the problem,” explained Anne McNeil, senior author of the study and a professor of chemistry, macromolecular science, and engineering at the University of Michigan. The team’s work underscores the challenges inherent in studying a pollutant that is, by its nature, incredibly tricky to isolate and quantify.
The Unexpected Source of Contamination
The discovery stemmed from a collaborative project examining microplastics in the atmosphere of Michigan. Madeline Clough, a recent doctoral graduate and lead author of the study, noticed unexpectedly high readings when analyzing air samples collected using standard protocols. “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. Initial suspicions fell on everything from plastic lab equipment to atmospheric sources, but the source remained elusive.
The team systematically investigated potential sources, eventually tracing the contamination back to the gloves themselves. They designed an experiment testing seven different types of gloves – including nitrile, latex, and specialized “cleanroom” gloves – and their impact on sample contamination. The results were striking: on average, the gloves imparted approximately 2,000 false positives per millimeter squared area. Which means that for every square millimeter of a sample touched by a gloved hand, researchers were potentially recording 2,000 particles that weren’t actually microplastics.
The problem arises because stearates are chemically similar to polyethylene, a common type of plastic. Using techniques like light-based spectroscopy and scanning electron microscopy, researchers found it was visually impossible to distinguish between the two. This creates a significant challenge for accurately assessing the true extent of microplastic pollution.
Cleanroom Gloves Offer a Solution, But Challenges Remain
The study identified cleanroom gloves as a viable alternative. Manufactured without the stearate coating, these gloves release significantly fewer particles, minimizing the risk of contamination. However, cleanroom gloves are typically more expensive and may not be readily available in all research settings.
Beyond switching glove types, the researchers likewise developed methods to differentiate between the false positives from stearates and genuine microplastics. This involved collaboration with statisticians and chemists to refine analytical techniques. “For microplastics researchers who have these impacted datasets, there’s still hope to recover them and find a true quantity of microplastics,” Clough noted. These methods allow researchers to revisit existing data and potentially correct for the glove-induced contamination.
The Importance of Chemical Expertise in Microplastics Research
The findings emphasize the crucial role of chemists in the burgeoning field of microplastics research. Understanding the chemical structure of plastics and potential contaminants is essential for accurate identification and quantification. “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.”
The study was supported by a grant from the University of Michigan’s College of Literature, Science, and the Arts’ Meet the Moment Research Initiative, highlighting the growing recognition of microplastic pollution as a critical environmental issue. The research team is continuing to refine their methods and collaborate with other researchers to address the challenges of accurately measuring microplastic contamination.
Looking ahead, the researchers plan to share their findings and analytical methods with the broader microplastics research community to promote more accurate and reliable data collection. The team also intends to investigate the potential for stearate contamination in other environmental samples, such as soil and sediment. The ongoing work will be crucial for developing effective strategies to mitigate microplastic pollution and protect human and environmental health.
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