Investigating the impact of microplastics

Researchers from AMI’s BioNanomaterials group have developed a new intestinal model to simulate the impact of microplastics absorbed by humans. Initial results show that these particles do not seem to provoke an immune response in the short term, but further studies are required to evaluate the effects of long-term exposures or of exposures to even smaller particle sizes.

The plausibility of human exposure to microplastics has increased over the past few years. Microplastics have been found in different types of food including seafood, salt, and beverages. In a sense, this is far from surprising. These plastic fragments have been found at the bottom of the ocean as well as on mountaintops—In other words, pretty much everywhere. Yet, less is known about their impact on human health.

“So far, the possible risks of microplastic ingestion by humans are not known and still need to be evaluated,” explains Dr. Roman Lehner, a postdoctoral researcher in the BioNanomaterials group. “It has been shown in studies using aquatic organisms, though, that due to their size, microplastic particles can directly harm the organism through intestinal blockage or internal tissue abrasion, depending on the shape and size of the particles.” Further concerns include possible intoxication of the organism via the leakage of chemicals such as phthalates that are found in polyvinylchloride (PVC), or brominated flame retardants used in different plastic applications. It has also been shown that microplastics can be translocated to the lymph system of blue mussels, causing strong inflammatory responses.

To evaluate possible human immune responses upon exposure to microplastics, the AMI researchers were asked by collaborators from German chemical company BASF SE to establish a novel 3D intestinal tissue model, as they are interested in increasing their knowledge on the potential effects of polymers on humans. “Ingestion of microplastic particles is likely to represent the main route of exposure in humans, since microplastic particles can be ingested by eating contaminated seafood or drinking water,” adds Lehner. “This makes the gastro-intestinal tract the most likely primary exposure site.”

The 3D intestinal tissue model, consisting of human intestinal epithelial cells, as well as human blood monocyte-derived macrophages and dendritic cells, involves aerosolizing microplastic particles directly on the cells’ surface. Cytotoxicity and immune response was investigated after six, 24, and 48 hours of exposure. “We used environmentally relevant microplastic particles provided by the collaboration partners at BASF SE, including polymers representing tire wear and polyolefins, for example particles of polypropylene used for packaging material, which represent major sources of micro-plastic in the EU,” explains Lehner. “We also compared these with other polymer classes, such as polyamide used for fishing nets, and harder cross-linked or softer thermoplastic versions of polyurethanes found in shoe soles or used to reinforce shorelines to prevent coastal erosion.”

This initial study showed no induction of cytotoxicity and did not generate any kind of inflammatory response, according to Lehner. This conclusion holds for the composition and size of the microparticles studied, ranging from 50 to 500 micrometers. But the absence of a biological response should not be generalized to all microplastics, since it cannot be ruled out that smaller sized particles or different polymers could still induce effects. 

“Given that this is the first study trying to assess the possible effects of microplastics on human health, extrapolation of these results to humans is critical,” emphasizes Lehner. Further research will be required to determine the effects of smaller plastic fragments, he reckons, while chronic exposure of the particles to the intestine barrier should also be considered. Possible scenarios under consideration may mimic daily food intake, including three to four exposures of the polymer particles per day.

Reference: Lehner, R.; Wohlleben, W.; Septiadi, D.; Landsiedel, R.; Petri-Fink, A.; Rothen-Rutishauser, B. A Novel 3D Intestine Barrier Model to Study the Immune Response upon Exposure to Microplastics. Arch Toxicol 2020.