Background and overview of microplastics
How the story started
In the past six decades we have produced 8.352 billion tons of plastics. Most of it has now ended up in landfills or directly in our natural environment. In fact, only 9% of the plastic used today is recycled.
Up to 12 million tons of plastic enter our oceans every year. This corresponds to one garbage truck per minute. Plastic waste on the streets can also get into the ocean via drainage networks or rivers: According to estimates, the world's major rivers carry up to 2.41 million tons of plastic into the sea each year, which corresponds to 100,000 garbage trucks.
Synthetic materials (polymers, microplastics or plastics) are one of the causes of our global environmental pollution. Floating plastic continents in several oceans, plastic bag-eating turtles, dead whales with plastic garbage stomachs are discoveries of the last few years that have received great media coverage and attention.
Microplastics were first detected in large numbers in the world's oceans in 2004. That made one thing very clear: plastic in the environment does not just go away. And not "only" with plastic, but also with microplastics, we are dealing with an environmental problem of enormous and global proportions. (Thompson et al., 2004 )
Where do we stand when it comes to microplastics?
Microplastics is a young research area with many unknowns. Science, industry, and politics are facing enormous challenges in order to grasp the phenomenon in all its complexity and to find effective solutions against the further spread of microplastics. If we want to understand what is hidden behind the term and research field of microplastics, we must direct our attention to the way we deal with plastics: from production and use to disposal or reuse. Here we have put together a few facts about the current situation.
There are different definitions of microplastics and differentiations from, for example, nano plastics. In the meantime, however, there is broad consensus that plastic fragments smaller than 5 mm should be referred to as microplastics.
The current definition of the term microplastics is as follows
Microplastics describes the entirety of all synthetic plastics and their products, which are smaller than 5 mm in size and which are either released directly into the environment or formed indirectly in the environment.
types of microplasticsare there and what are examples of them?
This category includes the types that are added directly to products (e.g. personal care products, cleaning agents, paints, etc.). This proportion is already often replaced by water-soluble polymers ("liquid microplastics"). Products are then often "advertised" with the addition "free of microplastics" or "without microplastics".
The category Primary Microplastics Type B includes plastic particles that are created through the use of plastic products and that are directly (without detours) released into the environment as microplastics.
Secondary microplastics include all microplastic particles that are formed in the environment as a result of the slow decay of large plastic parts. This can happen through all kinds of external influences, e.g. through the influence of UV rays, bacteria or friction.
primary and secondary microplastics?
In general, a distinction is made between indirect and direct entry routes. Indirect entry paths are found when plastic objects break down into smaller and smaller components due to UV radiation, oxidation and / or mechanical effects. Ultimately, millions of microplastic particles are created in our ecosystems (Law et al., 2014). Depending on their individual composition, they distribute quickly or slowly in water, soil, and the air.
Microplastics can also get into the environment directly: through tire abrasion, synthetic textile fibers that are released when clothes are washed, care products such as peelings that contain microplastic particles. Industrial wastewater is also one of the major sources of input. (Boucher et al., 2017)
In general, limnic ecosystems are more heavily contaminated with microplastics than marine ecosystems, since microplastics can be distributed more widely in the enormous volume of marine ecosystems. Plastic and microplastics collect in so-called "garbage patches" because of converging ocean currents.
There is heated discussion and research about how dangerous microplastics are for humans, animals, and the environment. Mainly due to their small size (≤ 5 mm), microplastics pose a threat to animals and the environment, as they are accessible to many organisms and are kept and eaten for food, for example. In addition, each microplastic particle has an individual composition due to previous production, use and disintegration processes. Extremely harmful micropollutants such as residues of plasticizers, heavy metals, PFOS or pharmaceuticals can adhere to microplastics. This increases the risk of physical and toxicological damage to organisms and ecosystems caused by microplastics (Law et al., 2014).
Microplastics are also transported or accumulated within the food chain. They also get into the human body (FAO, 2016). The nature of the consequences for human health and how harmful this will ultimately be cannot currently be foreseen.
Methods for the detection of microplastics are also discussed and researched. So far, there is no simple, standardized, and fast analytical method that can also be used outside of laboratories in real water and that can detect microplastics in different environmental matrices as reliably and reproducibly as possible. Due to the use of very different procedures, the data collected so far are difficult to compare and are often not very meaningful. This is one of the main reasons why there are still no limit values or political guidelines for dealing with microplastics.
An efficient identification and quantification of microplastic pollution is a great scientific challenge, because as the size of the particles (nano plastics) decreases, it becomes more and more difficult to recognize and detect them. Micro- and nano plastics that have not been detected can easily lead to the fallacy that they do not exist. In the environment especially:
Just because something can no longer be seen or detected does not mean that it is no longer there!