The environmental impact of plastics is an actual concern and a reoccurring topic in the media. In this context, the term microplastics is often referred to (Figure 1).
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| Google trend search on "Microplastics" |
Figure 1: Google trend search “Microplastics” (2018-2019).
In this blog post, we approach microplastics in a general way:
-What is it?
-How can we define it?
-Where does it come from?
In addition, we look at some specific topics such as microplastics in humans, cosmetics, oceans and associated health concerns.
Microplastics definition
Mircoplastics are solid particles which are insoluble in water and were synthetically generated. We can distinguish between primary and secondary microplastic particles:
- Primary microplastics are all primary manufactured particles, i.e. (liquid) prepolymers, plastic pellets and powders;
- Secondary microplastics are fragments of larger plastic parts. For example, fragments of plastic bottles, bags and so on.
What are the sizes of microplastics?
In general, microplastics have a size smaller than 5mm. However, the term “microplastics” covers different sizes [1]:
- Milli range from 1-5 mm
- Micro range from 1-999 µm
- Nano range from 1-999 nm
Where do microplastics found in our environment come from?
There are seven major release sources of microplastics which contribute to environmental pollution, especially in our oceans.
According to Figure 2, the major release source is the washing of synthetic clothes (35%). Microfibers of polyester and polyamide end up into the wastewater stream and then into the ocean. Main regions affected by this are India and South Asia. Following, are microplastics generated through wheel erosion during driving (28%). We have currently over 1 billion cars and the wheel debris is made up out of elastomeric particles. The third major generator of microplastics is city dust (24%).
Smaller release sources are road markers (7%), marine coatings (4%), personal care products (2%) and plastic pellets (0.3%). The latter is mainly generated by resin manufacturers and/or resin processers.
Figure 2: Overview of major microplastic release sources [7].
Microplastics in humans
As shown before, we are all exposed to many sources of microplastics and interesting is now to understand their impact on our body.
Investigations have shown that we take up 2.000 microplastic particles when eating table salt. Altogether, it should be 32.000 particles which every one of us takes up per year [6]. The studied published by South Korean researches sampled salt from 21 countries all over the world, including Europe, North and South America, Africa, and Asia. The study found that the amount of microplastics varies strong among the different brands and regions. Asian brands contain much higher amounts of microplastics. Salt from Indonesia has the highest amount of microplastics and this region is known to have the second-worst level of plastic pollution in the world.
Comparing the different geographical sources of salt, microplastics levels were highest in sea salt, followed by lake salt and rock salt.
In 2018, the Medical University of Vienna, Austria found microplastic particles in the human feces of eight out of eight tested people. They tested five women and three men form different countries, the Netherlands, United Kingdom, Italy, Poland, Russia, Japan, and Austria. For one week, all people wrote down what they consumed daily and delivered a stool sample at the end of the week. Researchers found 20 microplastic particles per 10 grams stool. Nine different plastics could be identified in the size of 50 to 500 microns. Most materials found were PP (polypropylene) and PET (Polyethylenterephthalate) [3].
The World Health Organization (WHO) is looking intensely into the impact of microplastic in humans and started several investigations [5]. The concern of WHO is that microplastics can enter the human body over drinking water and harm body functions. However, this concern has so far no scientific back up. The report from WHO states that there is insufficient information to draw firm conclusions on the toxicity of microplastics. The investigations are still ongoing. Mr. Gordon, who is the WHO coordinator of water, sanitation and hygiene, stated that as a consumer who is drinking bottled or taped water you should not be necessarily concerned to be exposed to health risks.
My wrap-up on microplastics
In various areas in our life we are exposed to microplastics and studies have shown that PE and PP are the most found type of microplastics. In general, large Mw polymers such as polyolefins are harmless materials when eaten due to their macromolecule size. On the other hand, plastics usually contain additives (small molecules), which can be easily released out of the compound into the environment. For instances, due to human safety regulations, food and beverage packaging plastics comply with strict standards concerning allowed additives and respective amounts.
However, with city dust this is not the case. As described above, microplastic from rubber car wheels is a major cause of air pollution, together with car brake dust. In major cities, millions of cars impact in this way our air quality. People all around the world already realized that and work on concepts to change and improve it. Smart city concepts are on the raise. For instances, these enable transportation of multiple people by e.g. autonomous electric people movers, which have the potential to reduce allover amount of wheels in a city by reducing the allover amount of cars. Furthermore, braking in electric cars does not release brake dust due to regenerative braking (converting the kinetic energy for immediately use or storage in battery).
At the moment, it is difficult to avoid intake of microplastics and we will have them around since cars and clothes will not disappear. However, public awareness increased in the past years and organizations like the WHO and research organizations initiated several studies on their impact on our health. It is important to understand the cause-effect relationships in this context and find solutions which consider environmental, as well as economic-social aspects.
Thank you for reading and till next time!
Best regards,
Herwig Juster
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Literature:
[1] H.A. Leslie: Review of Microplastics in Cosmetics, 2014
[2] https://www.addendum.org/plastik/besser-als-sein-ruf/
[3] https://www.meduniwien.ac.at/web/ueber-uns/news/detailseite/2018/news-im-oktober-2018/erstmals-mikroplastik-im-menschen-nachgewiesen/
[4] https://www.sciencehistory.org/case-study-plastics-and-the-human-body
[5] Susan Freinkel, Plastic: A Toxic Love Story (New York: Henry Holt, 2011), p. 89
[6] https://www.nationalgeographic.com/environment/2018/10/microplastics-found-90-percent-table-salt-sea-salt/
[7] https://phantomplastics.com/plastics-the-environment/
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