In a study published in the journal "Environmental Science: Nano", researchers from the French National Institute for Agricultural, Food and Environmental Research (INRAE) closely examined the impact of polystyrene nanoplastic particles on the intestines and livers of mice, using laboratory-produced model particles created through a precise process.
Plastic is not an inert material; it gradually breaks down into smaller pieces over time, forming microplastic particles, then nanoplastic particles (i.e., particles smaller than 1 micrometer).
Nanoplastic particles are found in drinking water and foods wrapped in plastic. This reality suggests that humans may ingest large amounts of nanoplastic particles that significantly expose the gastrointestinal tract.
However, our understanding of how nanoplastic particles affect gastrointestinal health is still limited. Additionally, previous studies on this topic used commercial particles, which often contain additives.
To this end, the team's chemists used an additive-free process, which they developed themselves, to manufacture 100% plastic polystyrene nanoplastic particles. Thus, they could focus on the specific effects of the polymer in its molecular form.
The particles were tagged with gold to facilitate monitoring their presence in the bodies of the mice and measuring their quantity. The toxicologists in the team exposed the mice to 3 doses of plastic nanoplastic particles—0.1, 1, or 10 mg of plastic nanoplastic particles per kilogram of body weight daily—added to drinking water for 90 days.
The mice received two diets: a standard mouse diet, and a "Western-style" diet (rich in fats and sugars), and the effects of the plastic nanoplastic particles on the mice's intestines and livers were studied.
Effects associated with diet
It was found that exposure to low doses of plastic polystyrene nanoplastic particles over 90 days has strong effects associated with the diet.
The integrity of the gut barrier was affected, an effect that was more pronounced in mice on the Western-style diet. The composition of the gut microbiota was also affected, an effect that was more pronounced in mice on the standard diet.
In the liver, exposure to low doses of plastic nanoplastic particles disrupted fat metabolism regardless of the diet, but glucose intolerance was more pronounced in mice on the Western-style diet. This effect was observed although the plastic nanoplastic particles did not penetrate the gut barrier. The changes mentioned above were associated with a noticeable increase in the weight of the mice.
The results of the study show that low doses of additive-free plastic nanoplastic particles can alter intestinal and liver functions in a diet-dependent manner.
