Lab Gloves May Be Inflating Microplastics Pollution Estimates

The Contamination Crisis

A shocking discovery from University of Michigan researchers reveals that the very tools scientists use to detect microplastics may be sabotaging their results. Scientists may have been unknowingly inflating microplastics pollution estimates, and the surprising source could be their own lab gloves. A University of Michigan study found that common nitrile and latex gloves release tiny particles called stearates, which closely resemble microplastics and can contaminate samples during testing.

The problem emerged when graduate student Madeline Clough was studying atmospheric microplastics in Michigan. When she examined the substrates to estimate how many microplastics she captured, the results were many thousands of times greater than what she expected to find. "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.

On average, the gloves generated about 2,000 false-positive signals per square millimeter. This contamination stems from routine lab practices—simply touching equipment with gloved hands transfers particles that mimic real microplastics during analysis.

The Science Behind the Mix-Up

The particles, which researchers identified as stearate salts, are used to help the gloves cleanly release from their mold during the manufacturing process. When gloves are used to handle laboratory equipment, the particles are transferred to anything they touch. These stearate salts create a perfect storm of confusion for researchers.

While not microplastics themselves, stearate salts are structurally similar to polyethylene, the type of plastic most often found in the environment. This structural similarity makes it difficult to distinguish them using the most common tools scientists use to determine whether a particle is plastic. The standard detection method—vibrational spectroscopy—struggles to differentiate between genuine plastic particles and these imposters.

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.

Health and Environmental Implications

The contamination issue becomes particularly concerning when considering particle size. Even more concerning, researchers found that the particles were largely less than 5 um in size. Microplastics in this size range have larger impacts on human and ecosystem health because they can more easily enter cells. By inflating microplastic counts in this size range, using laboratory gloves may jeopardize the studies that inform future policies and regulations.

Stearate salts are similar to soap molecules – if you eat a lot of them, they're probably not good for you, but they're not harmful in the environment in the same way that microplastics are. However, the false readings could lead to misguided environmental policies and public health responses based on inflated threat assessments.

Solutions and Future Research

The research team isn't just highlighting problems—they're providing solutions. To avoid contamination, researchers suggest scientists avoid glove use while conducting microplastic research. If that is not possible – for example, with biological samples where the researchers must wear gloves to protect themselves – they recommend a glove made without stearates, such as those designed for electronics manufacturing.

Despite this challenge, Clough and McNeil, working with graduate student Eduardo Ochoa Rivera and statistics professor Ambuj Tewari, developed methods to separate true microplastics from glove-related contamination. These techniques could allow scientists to revisit earlier datasets and produce more accurate estimates. "For microplastics researchers who have these impacted datasets, there's still hope to recover them and find a true quantity of microplastics," Clough said.

This discovery highlights broader challenges in microplastics research, where scientists lack standardized techniques for identifying and quantifying microplastics. While the findings may reduce some estimated pollution levels, it's important to note that even if the microplastic abundance in the environment is lower than researchers originally thought, any amount of microplastics can be troublesome, given their negative effects on human health and ecosystems. The research underscores the critical need for rigorous quality control in environmental science, especially when studying pollutants that could be lurking everywhere—including in the very tools meant to detect them.