Five studies published in April 2023 evaluated the potential impacts of micro- and nanoplastics on human health as well as sources of exposure.
In an article published on April 17, 2023, in the journal Scientific Reports, Jun Hyung Park from Chung-Ang University, Seoul, Korea, and co-authors, explored the effect of microplastics on breast cancer metastasis. While most effect studies are using spherical microplastics, Park et al. applied irregularly shaped particles that reflect the microplastic shapes most commonly detected in the environment. They ground polypropylene pellets, filtered them to collect particles <100 µm, and exposed different human breast cancer cell lines (MCF-7, MDA-MB-231) to them for 24 hours using concentrations that were not cytotoxic (1.6 mg microplastics/ml).
The scientists reported that the plastic fragments did not change the morphology nor “the migration ability of the breast cells.” However, RNA sequencing showed that the level of cell-cycle-related transcripts was significantly changed in microplastic-exposed MDA-MB-231 cells, demonstrating that the particles promoted metastatic features. Gene expression analysis confirmed that the expression of cell cycle-related genes was increased. Overall, the authors concluded that polypropylene plastic fragments “enhance metastasis-related gene expression and cytokines in breast cancer cells, exacerbating breast cancer metastasis.” Park and co-authors further pointed out that applied concentrations were rather high and called for more studies on chronic microplastic exposure and cancer progression.
In a review article published on April 20, 2023, in the journal Environmental Pollution, Yoojin Lee and co-authors from Yonsei University, Korea, provided an overview of the uptake of nanoplastics (< 1 µm) in human cells and the associated risks.
The authors stressed the differences between micro- and nanoplastics (e.g., in their size) leading to different effects needing separate assessments. They summarized that the uptake mechanism of nanoplastics would depend not only on their size but also their shape, surface functionalization, and concentration as well as on the cell type. Generally, risks would increase with smaller size, particle sharpness, and roughness as well as with higher concentrations. However, the authors outlined that cellular uptake studies are generally lacking, and existing ones have limitations. For instance, most are using high concentrations, spherical particles, and short exposure times which is only of limited environmental relevance. This leads them to call for more studies reflecting the wide diversity of nanoplastics that humans and the environment can be exposed to.
Researchers of the AURORA project have recently reviewed techniques to study nanoplastics, their benefits, and their limitations. AURORA is one of five Horizon 2020 research projects that are working to better understand micro- and nanoplastic impacts on human health (FPF reported). The project’s focus is on the assessment of microplastics’ effects on the placenta and the developing fetus.
How much humans are exposed to microplastics depends on their lifestyle and daily activities including their occupation. One group that may be exposed in particular is people working in plastic manufacturing plants. Maryam Shahsavaripour from Kerman University of Medical Sciences, Iran studied the occupational exposure levels to microplastics of 19 individuals working in a plastic bag factory in Kerman Province, Iran. Their article was published on April 20, 2023, in the journal Science of the Total Environment.
To compare different exposure routes, the scientists collected samples over six days from head hair, saliva, hand, and facial skin as well as from facial masks that the workers wore during their shift. Shahsavaripour et al. found that over the course of a day in the factory, the number of plastic particles on a participant increased from a mean of 92 particles before work to 161 particles per participant afterward. The highest number was identified in hair and the lowest in saliva samples. Since microplastic levels in the face masks increased from 102 articles in clean masks to 1080 particles after work, the authors concluded that “facemasks act as a useful barrier to reduce exposure to these particles through face, mouth and nose.” However, they further pointed out that face masks themselves can be an exposure source to particle fibers.
Besides occupational exposure, humans are exposed to microplastics contained in food e.g., since released from packaging (FPF reported and here). In an article published on April 14, 2023, in the Journal of Hazardous Materials, Yunlong Luo from the University of Newcastle, Callaghan, Australia, and co-authors assessed the release of micro- and nanoplastics from a plastic kitchen blender. To mimic the blending process, the scientists blended ice blocks mixed with Milli-Q water for 30 seconds using the pause function (1-second working, 1-second pausing). Subsequently, they analyzed the released plastic particles using Raman imaging.
Based on their particle count, the authors reported that 30 seconds of blending can release approximately 36–78 × 107 micro- and nano-sized plastic particles. They clarified that the amount may change with the material of the blender, the blending settings, times and temperature, and the characteristics of the food. Overall, they emphasized that “the significant releasing amount sends us a strong warning that we should be careful to use blenders to make juice or to smash food.”
The authors’ aim was not only to analyze particle release but also to advance Raman imaging as a tool for micro- and nanoplastics characterization. Previously, Luo and co-authors demonstrated that other food contact articles such as Teflon are a source of microplastics: broken coatings could result in a release of approximately 2,300,000 plastic particles (FPF reported).
Psychologists from the University of Vienna, Austria, evaluated the perception of experts on microplastic sources, associated risks, and potential solutions, their feasibility, and effectiveness in an article published on April 11, 2023, in the journal Microplastics and Nanoplastics. Maja Grünzner and colleagues collected survey responses from 73 scientists with an average of 5 years of experience in plastics research. The experts perceived particles from tire abrasion and fibers from textiles as major exposure sources to both humans and the environment. Based on the currently available scientific data, “they were more worried about impacts on the natural environment than on human health.” Solutions the participants rated as most effective and feasible included education and awareness programs as well as the bans on plastic items. Currently, only individual single-use plastics are regulated in different parts of the world (FPF reported, here and here).
References
Grünzner, M. et al. (2023). “Exploring expert perceptions about microplastics: from sources to potential solutions.” Microplastics and Nanoplastics. DOI: 10.1186/s43591-023-00055-5
Lee, Y. et al. (2023). “Potential lifetime effects caused by cellular uptake of nanoplastics: A review.” Environmental Pollution. DOI: 10.1016/j.envpol.2023.121668
Luo, Y. et al. (2023). “Detection of microplastics and nanoplastics released from a kitchen blender using Raman imaging.” Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2023.131403
Park, J. H. et al. (2023). “Polypropylene microplastics promote metastatic features in human breast cancer” Scientific Reports. DOI: 10.1038/s41598-023-33393-8
Shahsavaripour, M. et al. (2023). “Human occupational exposure to microplastics: A cross-sectional study in a plastic products manufacturing plant.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2023.163576
