Francielly Bruna, Neto Francisco and Ricardo Henrique Krüger, from the University of Brasília (UNB), warn that we urgently need technologies that will effectively eliminate partially or nonbiodegradable polymers from the marine environment.
Plastic contamination has reached a new climax in recent decades, becoming a great problem for a variety of ecosystems and threatening human and animal health to an irreversible point. We urgently need to address this issue not only by managing contaminated environments, but also by preventing the introduction of new contaminants.
Plastic products are essential goods in a diverse set of industry sectors due to their low cost, ease of manufacturing and physical-chemical characteristics. Different types of plastic polymers are used in the manufacturing of common day-to-day use products, mainly packaging, bottles and disposable materials.
However, those polymers are also part of complex products, including textile fibers, electronic devices, clothing, medical, and automotive objects. Consequently, a large amount of end-of-use waste is produced annually worldwide, with 31.9 million tons disposed of in terrestrial environments. It is estimated that approximately 4.8 to 12.7 million tons end up in the ocean.
Degradation process
Biotic and abiotic factors play an important role in the degradation process of plastic, as it is the environmental exposure conditions of the material that will influence its natural decomposition time. Microorganisms are essential in the biodegradation of waste in general. As for plastic waste, some bacteria, fungi and algae species can adapt to environments with great aggregation of high-density polymers and use this type of material as a carbon source. They release enzymes capable of attacking specific chemical bonds and fragmenting the pieces into smaller fractions. Nevertheless, it was later observed that this process leads to the formation of microscopic particles commonly known as microplastics, as microorganisms are unable to fully mineralize plastic.
READ MORE: Under the microscope: microplastics
Microplastics are classified as plastic particles smaller than 5 mm in size and usually occur after long term fragmentation of plastic pieces, but there are some products, such as cosmetics, that are already manufactured with a large quantity of microscopic plastic. The presence of microplastics in the environment has become an increasingly prominent concern in recent years.
Microplastics have been observed on various marine environments, encompassing the shore, sea surface, seabed from coastal areas to the open ocean, including Antarctic and Arctic oceans. About 80% of all the plastic debris present in the ocean originated from some terrestrial environment - however, ocean-based sources also represent a major contributor to ocean contamination, including shipping and fishing activities.
Plastic contamination
Recently, organizations all around the world are working on policies to tackle plastic contamination in the oceans. The OECD (Organization for Economic Co-operation and Development) has introduced a series of measures to mitigate microplastic contamination.
Furthermore, scientists are intensively researching new technologies based on the understanding of microbial communities present in contaminated areas and the mechanisms they use to survive.
Their ubiquitous presence makes them an important tool to address the problem in a sustainable way, by accessing their biotechnological potential for the production of enzymes capable of plastic depolymerization and the generation of novel biodegradable polymers.
Question of bioplastics
Bioplastics have been studied extensively in the past few years, generating a variety of polymers that may be a good replacement for petroleum-based ones. Overall, they are classified as bio-based and/or biodegradable - however, despite their better performance in terms of biodegradability, various ecotoxicological studies show that some types of bioplastics are also likely to cause harmful effects to the aquatic environment.
Other strategies, including catalytic-chemical degradation and recycling, are also widely implemented to manage plastic waste - however, those strategies demand high implementation costs and face limitations imposed by the materials and the process itself. It adds further complexity when it comes to marine environments, where waste is repeatedly disposed irregularly.
Irreversible contamination
Currently, microplastic contamination is practically irreversible due to the magnitude of contaminated areas, especially in the oceans, making it impossible to eliminate them entirely. Solutions currently presented are important to mitigate the problem, yet they are far from solving it. This inherent difficulty calls for technologies that will effectively eliminate the presence of partially or nonbiodegradable polymers from the marine environment.
The time to act is now - hence the primary focus should be on bioplastics that are not only completely biodegradable, but also bio-compatible, leaving no ecotoxic byproducts to be released in the environment.
From this point of view, although highly challenging, research efforts should aim at innovative routes for the discovery and production of novel biopolymers that are prone to complete degradation in natural conditions and safe for living beings.
Every passing moment, plastic contamination will remain an ongoing problem with unprecedented consequences. Convenient solutions have been proven to be insufficient. It’s time to face plastic contamination considering its challenging characteristics and pursue actual sustainable solutions to eliminate microplastics from the environment.
Francielly Bruna, Neto Francisco and Ricardo Henrique Krüger, Laboratory of Enzymology, Department of Cellular Biology, University of Brasília (UNB), Brasília, Brazil.
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