Microplastics are plastic particles whose size is between 5 millimeters and a few hundred nanometers, or 70 times smaller than the thickness of a hair. They can be produced intentionally or come from the fragmentation of larger particles (macroplastics). It is important to emphasize that microplastics are present in different forms (fragments, fibers, beads, films, etc.). They can be composed with more than twenty different polymers (polyethylene, polypropylene, polystyrene, etc.) including additives (plasticizers, antioxidants, flame retardants, coloring). They are ubiquitous, i.e. they are found in all compartments of the environment (water, land, air) but also in our daily environment (food, objects, containers, etc.). These particles accumulate in ecosystems, even in the most remote habitats, such as the seabed, or Antarctica, and are transferred in the food chains, which inevitably leads to their unintentional ingestion by humans. In addition, certain packaging (cups, water bottles, food boxes, etc.) and food cooking processes add additional microplastic contamination to our food.
Methods for characterizing microplastics under development
By habit, many single-use plastic materials are used in laboratories. Therefore, to carry out the research work on the subject of microplastics, it was necessary change work habits, adapt equipment and rethink work environments.
Several methods can be used to characterize plastics. The simplest uses a dye, the Nile red, to know if the observed particles are indeed plastic or not. Other more complex methods, using infrared, Raman or gas chromatography equipment, allow to identify the type of polymer or even the additives contained in the particle. The analytical processes must be adapted to the fields of study: marine sediments, water, air or food.
Microplastics found in many foods
Thus, microplastics have been detected in number of foods, including drinking water, milk, commonly consumed beverages (sodas, energy drinks, tea, beer, etc.), table salts, honey, seafood and fruits and vegetables, but also in bottles, tea bags and disposable cups. Work by ANSES has confirmed the presence of microplastics in molds and shells.
The compelling evidence for human ingestion of microplastics comes from two studies (published in Annals of internal medicine et Science of The Total Environment) who looked for their presence in human stool: microplastics were systematically detected in all the samples tested. Furthermore, another study highlighted the presence of microplastics in the human body at the level of the placenta.
Intestinal dysfunctions observed in animals
Many data show that the ingestion of certain microplastics leads to dysbiosisi.e. an imbalance of the microbiota, and a intestinal dysfunction in several animals, mainly fish and shellfish. Recent data suggest that these toxic effects on the microbiota and the intestinal epithelium might also affect mammals, following the ingestion of certain types of microplastics. It should be noted that this research only exposed these animals to only one type of polymer. No study has so far focused on the cocktail of microplastics that contaminate our food. In addition, there are no studies determining the effects of microplastic ingestion on humans, either on human intestinal tissues or their microbiota.
