A Science review article published on September 19, 2024, by a group of microplastic researchers under the lead of Richard C. Thompson from the University of Plymouth, UK, provides an overview of the microplastic research since the term was first introduced 20 years ago.
Besides sections focusing on microplastics in the environment, methods, and (potential) regulation, the review also includes a section on human exposure and health implications. Here, the authors summarize that there is widespread evidence for microplastic contamination of some foods, such as table salts (FPF reported), honey, seafood (FPF reported), mineral water (FPF reported), and beer (FPF reported), while data on other foods is limited, such as grains, fruits, vegetables, and baby foods. Microplastic contamination of foods can have its origin in the environment and increase by food processing, packaging, and handling (FPF reported and here).
Microplastics are taken up and have been detected in various human tissues, organs, and body fluids, including the human placenta (FPF reported), the inner lining of the uterus (FPF reported), breast milk (FPF reported), and blood (FPF reported). But, the particles are also eliminated via urine (FPF reported) and feces (FPF reported and here). “There is evidence for potential effects on human health,” the review summarizes. For instance, studies associated microplastic exposure with liver and ovarian cancer development (FPF reported) and connected the presence of particles with colorectal cancer (FPF reported) and with exacerbated breast cancer metastasis (FPF reported).
However, most data come from rodent or in vitro studies. In order to translate laboratory findings to human health implications, the authors propose the use of Quantitative In Vitro to In Vivo Extrapolation (QIVIVE) and pharmacokinetics (PBK) (FPF reported). The authors point out that translating laboratory studies to human health impacts is currently hindered by the fact that most laboratory experiments use concentrations and particle types that do not reflect human exposure scenarios.
Generally, research has shown that size and shape influence particle bioavailability and -accessibility while volume and surface area influence interaction with biological systems. The authors foresee research to bring insights into the effects of various microplastic types on human health within the next five to ten years. For instance, Five Horizon 2020 projects are working to better understand the impacts of microplastic exposure to humans including the AURORA project which investigates the effects on early life health (FPF reported). The projects’ final results are expected in 2026.
The Science review further finds that current natural science data indicate potential human health effects, but social science provides clear evidence that the public is already concerned. For instance, ocean microplastics were ranked of greater concern than climate change in the US and Australia, and microplastics in food ranked of greatest concern to German consumers. Given the public’s desire for action, the persistence of microplastics, and the difficulty of their removal, the authors call for immediate action considering the precautionary principle.
The scientists’ proposed solutions encompass a wide set of measures that they believe are needed. These should start upstream by reducing production (e.g., considering the essentiality of products), aim for better product design (e.g., yarns that reduce microfiber release), span the whole life cycle (FPF reported), and include behavioral change measures. They also propose regulatory options to tackle microplastics. They outline that purposefully produced microplastics are easier to regulate and have already been addressed by some regulations. For instance, microbeads added to cosmetics have been banned in many countries (FPF reported) and, in 2023, the EU REACH regulation banned intentionally added microplastics in all products (FPF reported on the draft proposal). Secondary microplastics – generated by the breakdown of macroplastics – are more difficult to address and “most regulations have targeted mitigation post-generation.” The authors put great hope on the “UN Plastic Pollution Treaty [which] now brings tangible opportunity for international actions” (FPF reported and here).
Reference
Thompson, R- C. et al. (2023). “Twenty years of microplastics pollution research—what have we learned?.” Science. DOI: 10.1126/science.adl27
