Knowledge gaps on micro and nanoplastics and human health: A critical review

Recent research has made it clear that humans are ubiquitously exposed to microplastics and nanoplastics (MPs/NPs) via inhalation, dermal exposure and ingestion. Global plastic production has increased considerably with 400 million tonnes of plastic produced annually while plastic waste predominantly ends up in landfill. The accumulation of plastic in our water-bodies has detrimental long-term impacts, with persistent plastics degrading into smaller microplastics and nanoplastics (MPs/NPs). The presence of MPs/NPs in many food and beverages is a stark reminder of their pervasion into every aspect of the food chain. We have yet to determine if this long-term, chronic exposure to MPs/NPs has adverse effects on human health. This review examines the evidence in the literature highlighting the challenges of performing human studies including the lack of quantitative evidence, which is needed to make realistic estimates on the level of exposure and therefore risk. While occupational exposure to synthetic fibers in textile workers has been associated with respiratory disease, lung cancer, and bowel cancer, there are no other human studies. However, there are some rodent studies highlighting adverse effects on gut homeostasis, male reproduction, F1 offspring, and inflammation. Given these findings, further studies in human populations and model systems is a priority.