A quick guide to the world of microplastics
The history of microplastics
At the end of the 20th century, scientists began to think critically about the impact our litter was having on the environment. Plastic litter posed an important question to scientists who knew very little about its fate in the natural world. Mass production of plastic across the globe since the end of the Second World War had made the question about the fate of this growing plastic problem increasingly relevant. In the early 1990s, this question was finally answered: Dr. Richard Thomson was walking along the Plymouth coast participating in a beach cleanup when he picked up a handful of sand in which he saw small fragments of plastic litter. He brought it back to the university to be analyzed in a lab. He was able to determine that the sand was made up of a mixture of sand particles and microscopic pieces of plastic, concluding that the larger plastics littered into the environment were breaking down in nature, not disappearing. Thus, he coined the term “microplastic”, and the study of this ubiquitous contaminant began.
What are microplastics?
Microplastics are defined as any piece of plastic less than five millimetres in its longest dimension. Microplastic particles can come in a variety of shapes that are used to categorize the abundance of plastic across the world. They are often categorized based on shape (ex. fragments, spheres/beads, fibers, pellets, foams, and films), size, polymer, and colour. These particles are further classified as either primary or secondary microplastics.
Primary microplastics are microscopic pieces of plastic that are produced by industries and then released into the environment; these primary microplastics are usually microspheres (also called microbeads) or plastic pellets. Microbeads are found in cosmetic products like face wash or even toothpaste, while plastic pellets are produced by industry to be later melted down to form larger plastic products. Primary microplastics are most often released into the environment through our homes (through cosmetic products) or by spills into the environment (often during transport). Secondary microplastics are microscopic pieces of plastic that have been broken down from larger plastic debris in the environment. These secondary microplastics come in diverse shapes and sizes. For example, plastic microfibers are released from synthetic clothing during a wash cycle. As large plastics such as plastic bags, coffee cup lids, or old toys accidentally make their way into our environment, abiotic factors (i.e. wind, water, sunlight) break down these larger items into smaller and smaller sizes. These plastics never disappear; instead they become much harder for us to see, to clean up, and to understand.
Why do we care?
What is the impact of these microplastics on the world, why are people talking about them so much, and why are people so concerned about something so small?
Studies have shown microplastics to be ubiquitous in our environment; found in in marine, freshwater, and terrestrial environments across the world. The field is relatively new compared to the study of some other pollutants, and thus far research has primarily focused on the largest global sink of plastic debris: the ocean. Recent research into freshwater environments show that microplastics are found in the Great Lakes at concentrations higher than they are found in the ocean’s garbage patches.
Despite the increasing interest in the field, we still don’t know a lot about the ecological consequences of microplastics. While we do know that microplastics are readily ingested by many organisms, we do not yet have evidence that microplastics bio-magnify up the food chain unlike other contaminants such as DDT or certain heavy metals. However, lab experiments have shown that high concentrations of microplastics can have an effect across many levels of biological organization in both marine and freshwater environments. Some studies have demonstrated that the impact of microplastics on the lowest level of the food chain, such as zooplankton/waterflea, is lethal.
A major concern for ingestion of microplastic particles is from both their chemical additives and sorbed contaminants. Chemical additives are manufactured into the plastics by industries (ex. flame retardants) and these may cause added effects to organisms who ingest them. Additionally, a major concern for aquatic ecosystems is the ability of microplastics to sorb dangerous pollutants from the water. Microplastic particles have been shown to function as vectors of toxic chemical pollutants in aquatic environments; as organisms ingest the microplastics, the sorbed contaminants enter the organism’s body as well. This can be dangerous to aquatic ecosystems as these chemical pollutants are entering the food chain at high concentrations and have become more readily available by the extensive pollution of microplastics.
What does it mean?
As far as research has shown, microplastics have not demonstrated a direct impact on humans, but they are affecting the world and biological processes around us. Scientists are only now discovering the ecological consequences of plastic pollution, often to the lowest level of aquatic food chains. If significantly affected, these organisms have the potential to cause devastating effects across natural food web systems and threaten the biodiversity of many ecosystems. Magnified by the discovery of microplastics is the understanding of the true extent of human plastic pollution. Samples of water, sand, and sediment around the world show that we have littered our environment with plastic without thinking about the ramifications that our litter could cause on the existing biological systems and processes.
Addressing the issue
The plastic pollution problem is complex and thus requires many actors working in tandem to find solutions. There are two main strategies for the mitigation of plastic pollution: reduction and cleanup. To reduce the amount of microplastics in the environment, we can target the primary microplastics through bans such as the microbead bans that have swept across the globe since 2013. To prevent the release of secondary microplastics into our watersheds, scientists have done a lot of research to better understand the sources of plastic pollution. These sources can either be as direct as household washing machines; mitigated by attaching filters onto the washing machines to prevent the release of microfibers from our clothing into the environment; or the sources can be harder to mitigate such as storm water effluent, wastewater treatment plant effluent, and agricultural runoff. However, solutions such as filters on storm drains, rain gardens, and specialized systems in our Wastewater Treatment Plants already exist. The other side of plastic mitigation involves cleanup efforts. As plastic pieces get smaller, cleanup becomes much more complex. Tackling the cleanup of larger items is more feasible. Thus, reducing the amount of microplastics that enter our environment every day is often the focus of microplastic mitigation.
What can we do?
Refuse, Reduce, Reuse, Recycle. By refusing to use single use plastic we can begin to reduce the amount of plastic that is produced in the first place. Individual actions surrounding plastic pollution matter.
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