ISO stands for "International Organisation for Standardization". The ISO standards serve to establish industry standards. In addition to the international ISO standards, there are ASTM, NOISH, EU and China standards. The acronym ASTM stands for "American Society for Testing and Materials" and NOISH for "The National Institute for Occupational Safety and Health". Contrary to what the name suggests, the ASTM standards are international. So are the NOISH standards. All these standards are used to assess the safety of surgical face masks. In their scientific publication, Han's research group criticised the following mechanical properties of surgical face masks, which had been proven with an electron microscope: All these norms and standards do not assess the micro- and nanofibres loosely attached to the inner surface of surgical face masks, which can find their way into the human lungs, bloodstream and cell interior when inhaled.1 Yet the ISO norms are primarily mechanical in nature and should include such important findings in the assessment. We know from experimental animal models that nanoparticles can enter cells and also pass the blood-brain barrier.
In their review, Hirt's research group looked at the influence of micro- and nanoplastics on the organism of animals and humans. Currently, there is still a lack of scientific studies that exclusively deal with the influence of micro- and nanoplastics on the human organism. In animal studies, the exposure of laboratory animals to nano- and microplastics was associated with an impairment of the oxidative and inflammatory intestinal balance. The influence of these particles resulted in a breakdown of the intestinal barrier. Various research groups have observed dysbiosis and immune cell toxicity as a result of exposure to micro- and nanoplastic particles. Microplastics also contain additives and are capable of storing pollutants. The surface of these particles can also be colonised with pathogenic bacteria. This could be a basis for the development of chronic inflammatory diseases.2
It is the omnipresence of micro- and nanoplastics that sooner or later results in exposure to the human organism. The long-term consequences of this exposure have not yet been researched. However, they are already causing concern in the research world, as the development of chronic inflammatory diseases is conceivable.3 Humans can ingest microplastics in various ways. Food plays an important role here. For example, a portion of fish contains 66 x 103 particles, sugar 217 plastic fibres/kg, beer 2-79 plastic fibres/litre and milk 1-14 plastic fibres/litre. Even in drinking water - whether filled in plastic bottles or glass bottles - plastic particles can be found.4-11
In addition to plastic ingestion through food and drink, inhalation of micro- and nanoplastics also plays an important role for the human organism. Synthetic textiles and the abrasion of car tyres on the road have so far been the main sources of inhaled plastic particles.12,13 Micro- and nanoplastics can enter the human organism via a third route: This is where the cosmetics industry comes into play, offering microplastics in toothpaste and in facial scrubs for daily consumption. Microplastics and nanoplastics can also be absorbed through the skin.14 Besides such obvious microplastic hiding places, there are other products in which one would not suspect microplastics at first glance. Microplastics are used by the cosmetics industry to increase the viscosity of their products and stabilise emulsions. It is present in soaps, shampoos, deodorants, anti-wrinkle creams, moisturisers, shaving cream, sunscreens, facial care masks, lipsticks, make-up and even bath additives for infants.15
The human body is bombarded with plastic from all sides. What effect can this have on our organism in the long run? According to several studies, microplastics ingested by a living organism accumulate in the gastrointestinal tract of the respective species.16-19 Microplastics larger than 150 µm cannot be absorbed and remain in the intestinal mucosa. Here it leads to local inflammatory reactions and influences the immune system. If the plastic particles are smaller than 150 µm, they can pass the intestinal barrier. This leads to endocytosis by enterocytes, transcytosis by M-cells and then to paracellular uptake.20
The small size of ingested plastic particles allows them to reach other organ systems. They can reach the liver, spleen, heart, lungs, thymus, reproductive organs, kidneys and even the brain by this route.21,22 Inhaled microplastics can also have an effect on the gastrointestinal tract and the immune system, in addition to being absorbed through the respiratory epithelium.23-25 Once in the bloodstream, micro- and nanoplastic particles can lead to dysregulation of the immune system.
References:
1. Han J. et al. (2021). Need for assessing the inhalation of micro(nano)plastic debris shed from masks, respirators, and home-made face coverings during the COVID-19 pandemic. Environ Pollut. 2021;268(Pt B):115728.
2. Hirt N. et al. (2020). Immunotoxicity and intestinal effects of nano- and microplastics: a review of the literature. Part Fibre Toxicol 17, 57 (2020).
3. Prata JC, da Costa JP, Lopes I, Duarte AC, Rocha-Santos T. Environmental exposure to microplastics: An overview on possible human health effects. Sci Total Environ. 2020; 702:134455.
4. Hantoro I, Löhr AJ, Van Belleghem FGAJ, Widianarko B, Ragas AMJ. Microplastics in coastal areas and seafood: implications for food safety. Food Addit Contam Part Chem Anal Control Expo Risk Assess. 2019;36:674-711.
5. Liebezeit G, Liebezeit E. Non-pollen particulates in honey and sugar. Food Addit Contam Part A Taylor & Francis. 2013; 30:2136-40.
6. Yang D, Shi H, Li L, Li J, Jabeen K, Kolandhasamy P. Microplastic pollution in table salts from China. Environ Sci Technol. 2015; 49:13622-7.
7. Iñiguez ME, Conesa JA, Fullana A. Microplastics in Spanish table salt. Sci Rep. 2017; 7:8620.
8. Karami A, Golieskardi A, Ho YB, Larat V, Salamatinia B. Microplastics in eviscerated flesh and excised organs of dried fish. Sci Rep. 2017; 7:5473.
9. Gündoğdu S. Contamination of table salts from Turkey with microplastics. Food Addit Contam Part Chem Anal Control Expo Risk Assess. 2018; 35:1006-14.
10. Liebezeit G, Liebezeit E. Synthetic particles as contaminants in German beers. Food Addit Contam Part A. Taylor & Francis. 2014; 31:1574-8.
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14. Strand J. (2014). Contents of polyethylene microplastic in some selected personal care products in Denmark; 2014.
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16. Deng Y. et al. (2017). Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure. Sci Rep. 2017; 7:46687.
17. Qiao R. et al. (2019). Accumulation of different shapes of microplastics initiates intestinal injury and gut microbiota dysbiosis in the gut of zebrafish. Chemosphere. 2019; 236:124334.
18. Jin Y. et al. (2019). Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice. Sci Total Environ. 2019; 649:308-17.
19. Deng Y. et al. (2018). Evidence that microplastics aggravate the toxicity of organophosphorus flame retardants in mice (Mus musculus). J Hazard Mater. 2018; 357:348-54.
20. Powell J. J. et al. (2010). Origin and fate of dietary nanoparticles and microparticles in the gastrointestinal tract. J Autoimmun. 2010;34:J226-3.
21. EFSA. Presence of microplastics and nanoplastics in food, with particular focus on seafood. EFSA J. 2016;14:e04501.
22. Prüst M. et al. (2020). The plastic brain: neurotoxicity of micro- and nanoplastics. Part Fibre Toxicol BioMed Central. 2020; 17:1-16.
23. Smith J. R. H. et al. (2002). A study of aerosol deposition and clearance from the human nasal passage. Ann Occup Hyg Oxford University Press. 2002; 46:309-13.
24. Asgharian B. et al. (2001). Mucociliary clearance of insoluble particles from the tracheobronchial airways of the human lung. J Aerosol Sci Elsevier. 2001; 32:817-32.
25. Enaud R. et al. (2020). The gut-lung axis in health and respiratory diseases: a place for inter-organ and inter-kingdom crosstalks. Front cell infect Microbiol. frontiers. 2020; 10:9.