Health Canada Study Finds Gallbladder Inflammation in Mice Fed Plastic Particles

Health Canada researchers dosed male and female mice with polystyrene nano- and microplastic particles for 28 days and found inflammation in the gallbladders of nine of 23 exposed males and two of 24 exposed females. The study was published Sept. 3 in the open-access journal Microplastics and Nanoplastics.

The particles were given by oral gavage, a dose delivered directly into the stomach. Led by Kristen A. Marcellus of Health Canada's Food Safety Regulatory Research Division, the team tested two forms on C57BL/6 mice: manufactured spheres and milled, irregularly shaped fragments. The gallbladder counts cover both forms.

The paper reports no significant changes in food consumption, body weight or organ weight coefficients in the exposed animals, and no changes in hematological or clinical biochemistry measures. Adaptive and innate immune markers showed no major changes either.

The differences the authors record are between the sexes rather than between the two particle shapes, which produced similar results. Pro-inflammatory cytokines, the signaling molecules that drive inflammation, were decreased in all exposed males. Exposed females instead showed mild pathological changes in the small intestine, affecting the goblet cells that produce the gut's mucus lining and the amount of mucus made.

Polystyrene was detected in the liver and intestines of both sexes. The team concluded that "further research is warranted to explore the potential sex-specific response to microplastic exposure."

The work was funded by the Government of Canada's Advancing a Circular Plastics Economy for Canada Initiative. The journal received the paper on April 16 and accepted it on Aug. 29; Springer is publishing the accepted version ahead of the final version of record.