What is a “Microplastic”?
The Merriam-Webster Dictionary defines the term “microplastic” to be a “very small piece of plastic especially when occurring as an environmental pollutant; a piece of plastic that is five millimeters or smaller in size”. Despite first appearing as a used word in 1990, the term has only been gaining much recognition and relevancy in more recent years as microplastics are revealed to be harmful pollutants. Microplastics can be microbeads or come from degraded larger pieces of plastic, and their tiny sizing allows them to be carried throughout the world through transport mediums such as wind and waterways. They have been found at the bottom of the ocean, in Arctic ice, in soil, in whale fat, and inside of human blood.
Microplastics are becoming a increasingly pressing issue for human health as well as the health of other organisms. Some materials of microplastics have affinities for toxic chemicals, acting as magnets for toxins such polychlorinated biphenyl (PCB). PCB is a synthetic pollutant that was banned 1979, yet persistently remains in the environment and is an endocrine-disruptor for animals which causes health issues.
Microplastics in the Ocean
In marine environments, tracking how microplastics disperse and where they go is difficult due to variable ocean currents and the many ways that they can enter into the ocean. While knowing exactly where they go is difficult, predicting where they go is possible, and water sampling has informed scientists more about where they can be. Generally, a portion of microplastics sit on the ocean surface while some are brought down throughout ocean columns in significant abundance, creating exposure to a wide variety of marine organisms.
Filter-feeders such as bivalves and, krill, and baleen whales intake microplastics through direct ingestion, but other organisms such as types of plankton can absorb microplastics into their tissues. If an organism accumulates too much microplastic, their biological functions can be disturbed which can be lethal.
Since microplastic absorption can occur at the lowest trophic level, organisms at higher trophic levels are at greater risk for toxic bioaccumulation since they must consume greater amounts of food to receive enough energy to function. Also, since species are variable, some are affected more by microplastic presence than others, which can affect their fitness.
Pollution is a Human Issue Too
The National Oceanographic Centre in the United Kingdom predicts that 10 million tons of plastic pollution enter the ocean every year. Not nearly as much is cleaned back out of the ocean annually. As more plastic builds up in the ocean and degrades, creating microplastics, microplastics pose a significant threat to marine organisms. If species are unable to populate at normal rates due to lower fitness, this could drive them to extinction, shifting ecological activity and potentially even causing trophic cascades. At the same time, humans will be consuming increasing amounts of microplastics that permanently remain in the body, meanwhile fisheries can collapse due to depleted fish stocks, damaging economies.
Environmental issues such as climate change, habitat destruction, and pollution are typically pivoted to be something that just affects the environment, which tracts attention away from just how devastating an unhealthy environment is for human society. But environmental issues can also be economic, health, and social issues.
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