A recent study from the University of Michigan (U-M) reveals that nitrile and latex gloves could be compromising the accuracy of microplastic research. The findings suggest that these gloves may unintentionally contaminate equipment with non-plastic particles called stearates, leading to a significant overestimation of pollutants in air and water samples.
The source of the contamination
Stearates are salts or soap-like particles used by manufacturers to coat disposable gloves, making them easier to peel from production molds. While these particles are not plastic, they are chemically and visually similar to microplastics at the structural level.
The issue came to light when U-M researcher Madeline Clough was examining atmospheric microplastics in Michigan. While following standard field guidance to wear nitrile gloves, Clough found results 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. After investigating various sources, including plastic squirt bottles and ambient lab air, the team traced the contamination back to the gloves.
Quantifying the impact of stearates
To understand the breadth of the problem, researchers tested seven types of gloves and simulated standard contact between a researcher’s hand and lab equipment, such as filters or microscope slides. The results, published in RSC Analytical Methods, showed that gloves resulted in an average of 2,000 false positives per millimeter squared area.
Using scanning electron microscopy and light-based microscopy, the team determined that these stearate salts are visually indistinguishable from polyethylene. This similarity means that any contact between a gloved hand and a sample or substrate could likely impart stearates that inflate data.
Optimizing lab procurement and SOPs to prevent contamination
The University of Michigan study provides a clear roadmap for lab managers to refine their quality control protocols. Beyond the immediate impact on environmental data, these findings necessitate a shift in how labs handle high-sensitivity samples to ensure data integrity.
To maintain the accuracy of microplastic analysis, lab managers should consider the following operational adjustments:
- Audit glove inventory: Standard nitrile and latex gloves used during sample preparation can impart an average of 2,000 false positives per millimeter squared due to stearate coatings
- Transition to cleanroom-grade PPE: Utilizing cleanroom gloves in ultrapure applications significantly reduces particulate release because they are manufactured without stearate lubricants
- Update contamination controls: Since stearates are visually and chemically similar to polyethylene, SOPs should be updated to include spectroscopic verification to distinguish between glove residue and true environmental pollutants
- Data recovery protocols: Lab managers overseeing impacted datasets can implement new statistical and chemical identification methods to differentiate false positives, potentially saving years of research from being discarded
By eliminating contamination at the source, labs can ensure that their findings reflect true environmental conditions rather than artifacts of their own protective equipment. Anne McNeil emphasizes that while current figures may be inflated, the fundamental goal remains to eliminate these pollutants entirely.
This article was created with the assistance of Generative AI and has undergone editorial review before publishing.
