It is well-known that pollution from plastic, especially smaller microplastics, have reached the oceans and even some of the most remote corners of the Arctic. Even so, there is uncertainty about the magnitude of plastic pollution in marine environments and it cannot be exactly said how much pollution does plastic, especially microplastics cause.
Now, a new study published in Nature Communications has estimated the amount of microplastic pollution in the Atlantic Ocean and put it at 11.6-21.1 million tonnes, indicating that the inputs and stocks of ocean plastics are much higher than determined previously.
That microplastic pollution in oceans is underestimated is also not a novel finding, but the new study is one of the few that have tried to put a number to the amount of microplastic pollution that is present in the oceans.
What are microplastics?
Microplastics are plastic debris smaller than 5mm in length, or about the size of a sesame seed. While they come from a variety of sources, one of them is when larger pieces of plastic degrade into smaller pieces, which are difficult to detect.
How does plastic reach the oceans?
There are multiple pathways. For instance, riverine and atmospheric transport from coastal and inland areas, illegal dumping activities and direct-at-sea littering from shipping, fishing and aquaculture activities, scientists have said.
According to the International Union for Conservation of Nature (IUCN), at least 8 million tonnes of plastic end up in the oceans every year and makes up about 80 per cent of all marine debris from surface waters to deep-sea sediments.
Why is plastic pollution especially harmful?
The durability of plastic, which, on the one hand, makes the material suitable for widespread use from packaging to storing food is also a bane because it implies that plastic can take hundreds to thousands of years to decompose depending on the type of plastic and where it has been dumped.
In the oceans, plastic pollution impacts marine life, ocean health, coastal tourism and even human health. Over the past few years, various news reports have shown that marine animals such as whales, seabirds and turtles unknowingly ingest plastic and often suffocate.
One of the most popular images in the last few months was that of a dead sperm whale that washed up on a Scottish beach in December 2019 with an estimated 220 pounds of tangled debris, including netting, rope and plastic, inside it. Even so, it was not clear if the debris was responsible for the whale’s death. While all sorts of marine species are prone to get impacted by plastic pollution, typically, bigger marine species tend to get more attention because of the amounts of debris they can hold up.
For humans, too, marine plastic pollution is harmful if it reaches the food chain. For instance, microplastics have been found in tap water, beer and even salt. One of the first studies to estimate plastic pollution in human ingestion that
was published in June 2019 said that an average person eats at least 50,000 particles of microplastic each year. Consumption of plastic by humans is harmful since several chemicals that are used to produce plastics can be carcinogenic.
Even so, since microplastics is an emerging field of study, its exact risks on the environment and human health are not clearly known.
So what does this mean?
In the study, scientists studied pollution of the Atlantic Ocean caused by three types of plastics: polyethylene, polypropylene, and polystyrene, which were suspended in the top 200 metres of the ocean. These three types of plastic are most commonly used for packaging.
Smaller plastic particles are a hazard, the scientists note, as it is easier for them to sink to greater ocean depths and some marine species such as zooplanktons show preferential ingestion of smaller particles, making them easier to enter the food chain and their conversion to fast-sinking faecal pellets.
Scientists say that pollution caused by microplastics has been “severely” underestimated in previous assessments and that a considerable amount of small microplastics are lost from the surface and are stored in ocean interiors.
They also estimate that based on plastic waste generation trends from 1950-2015 and considering that the Atlantic Ocean has received 0.3-0.8 per cent of the global plastic waste for 65 years, the Atlantic waters could hold 17-47 million tonnes of plastic waste.
“To date, a key uncertainty has been the magnitude of contamination of the ocean and our findings demonstrate that this is much higher in terms of mass than has been estimated previously,” they note.
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