Immense concentrations of plastic debris have been observed in the oceans, especially in the subtropical gyres, but one can also find it in lakes and rivers. The topic even raised media-sensationalized images of plastic islands or plastic patches in the oceans. A non-existing myth!
What Are Microplastics?
Within the last years, the focus of plastic pollution has been shifted from macro- to microplastics. The term microplastic is used for small plastic particles of different origins, sizes and chemical composition. An exact definition of microplastics has not been uniformly defined, but the most commonly used (taking into account the relevant literature) is that microplastic particles have a diameter between 1-5 millimeters.
There are two types of microplastics distinguished, primary and secondary. Primary microplastic is produced industrially in the form of plastic-based granulates or pellets, which can be found as microbeads in cosmetics. Secondary microplastic occurs through chemical and physical aging and degradation processes of macroplastic (e.g., plastic bags, plastic bottles, fishing nets or styrofoam products). As far as can be ascertained today, secondary microplastic is the main source of entry into the environment.
What Is Macroplastic?
Macroplastic is clearly visible plastic that can be caught, to say it in an easy way, and will not (with a few exceptions) have a direct impact on the food chain.
On the other side, we have microplastic, meaning small pieces of 1-5 mm in size floating in our oceans like a soup and finding their way directly or “spontaneously” into the food chain due to their size.
However, as mentioned above, macroplastic degrades into microplastic due to different processes such as hydrolysis, photodegradation or mechanical/physical degradation.
And How Do They Become Nanoplastic?
The breakdown process is not likely to stop at the micro level but will instead continue until the microplastic becomes small, nano-sized plastic particles!
All the microplastic derived from washing clothes or microbeads found in cosmetics might be further degraded to nanoplastics!
So what about the nanoplastic? So far the knowledge is quite scarce, since there are just a handful of publications dealing with the topic of nanoplastic. However, what is known is that despite their small size they have an enormous surface area, bearing the potential to bind an even bigger amount of toxic compounds than microplastic.
For an enhanced understanding of the problem of nanoplastic, one should have a deeper look on the highly developing field of nanomedicine. Several studies in this field dealing with the development of nanosized (10-100 nm) drug delivery systems showed that, due to their small size, they have the potential to spontaneously overcome natural biological barriers such as cell membranes by a process called endocytosis.
Microplastic needs to be consumed actively, whereas nanoplastic might be absorbed spontaneously!
Experiments regarding nanoplastic need different considerations than macro- or microplastic because of the unique physicochemical nanoscale properties, and definitely need also a different approach than nanoparticles used in the field of nanomedicine.
What has already been investigated so far? Up to now, a few organisms such as algae, zooplankton, daphnia, sea urchin, fish and shrimp have been used to study the effects of nanoplastics. But what will be the impact of nanoplastic to plankton?
These questions, too, remain: How do we detect it in the environment? How can we measure it? What is the potential toxicity?
New approaches and methods are urgently needed to answer those questions and to generate more data for a better understanding of the topic and the potential impact on human health.
Could the least known area of marine litter potentially be the most hazardous?