Common Lab Gloves May Inflate Microplastic Pollution Measurements, U-M Study Finds
A University of Michigan study indicates that nitrile and latex gloves commonly used by scientists may lead to an overestimation of microplastic pollution measurements. The research, led by Madeline Clough and Anne McNeil, suggests that these gloves can unintentionally contaminate lab equipment with nonplastic particles called stearates.
These particles are chemically similar to some microplastics, which can result in false positives during microplastic detection.
Stearates are salts used to help manufacturers peel disposable gloves from their molds. Researchers acknowledge that significant microplastic pollution exists but note the potential for inflated measurements.
Uncovering the Contamination Source
The study originated when Clough observed unexpectedly high microplastic counts during an atmospheric microplastics project. Initial investigations into various contamination sources eventually traced the issue to the gloves used for sample preparation.
An experiment was designed to assess the extent of the problem, testing seven types of gloves, including nitrile, latex, and cleanroom gloves, across common microplastic identification techniques. The experiment simulated typical contact between a gloved hand and research equipment like filters or microscope slides.
Key Findings:
- Gloves imparted an average of approximately 2,000 false positives per square millimeter.
- This contamination could affect all varieties of microplastics research involving direct contact with samples.
- Cleanroom gloves, manufactured without stearate coatings, resulted in the fewest imparted particles.
Differentiating True Microplastics from Contaminants
Researchers found that stearate particles were visually indistinguishable from polyethylene, a common plastic, when examined using scanning electron microscopy and light-based microscopy.
However, in collaboration with Eduardo Ochoa Rivera and Ambuj Tewari, methods were developed to chemically differentiate between glove-derived stearates and environmental microplastics. This development offers a way for researchers to potentially correct affected datasets.
The study highlights the importance of chemical expertise in microplastics research to distinguish between true microplastics and other contaminants, given the pervasive presence of plastics in the environment.