Braden Wilkinson is a conservation blogger, wildlife photographer and avid birder - and a friend of the Two Oceans Aquarium. As it is Plastic Free July, Braden is helping us share the facts about microplastics - an often overlooked component of plastic pollution, that affects not just the ocean, but even your body.

By now, you may have heard that plastic pollution is an immense problem in the environment, particularly our oceans. However, did you know that your last meal could have contained small pieces of hidden plastic? These are called microplastics.

Due to, amongst other things, their low production cost, adaptability, light weight, and durability, plastics are intensively used in wide-ranging applications across numerous industries. All those benefits, however, come with some potentially dangerous negatives.

What are microplastics and how are they formed

Microplastics are tiny pieces of plastic that have broken off from larger pieces of plastic.  For example, let's take items such as a chip packet, or a plastic grocery bag or a plastic water bottle - once it's in the environment it won’t stay in its production form forever. It will break up into microplastics. The successive breaking up and changing of these large plastic pieces through biological, photo-, and mechanical degradation in the environment, form these tiny particles. The plastic itself is never actually destroyed. 

Particles smaller than 5mm are of particular concern mainly due to their long environmental persistence, small size, high surface/volume ratio, and their capability of entering the cells of organisms and inducing adverse effects within these cells. The first awareness concerning the occurrence of plastic debris in the marine environment was in the 1970s. Since then, plastics have been found everywhere in marine, freshwater and terrestrial ecosystems, including remote and uninhabited locations. Recently, a plastic bag was even discovered on the floor of the Mariana Trench, the deepest part of the ocean.

A recent study of foraging shorebirds has shown that the break down of biofilms (microorganisms such as bacteria or fungi which cover the microplastic pieces) produce a smell (dimethyl sulphide) very similar to that which is commonly associated with organic matter. This literally means that those little pieces of plastic smell like delicious food to the birds.

Researchers suggest that sea turtles ingest plastics for the same reason, with visual signals also playing an important role, e.g. a plastic bag floating in the ocean can be mistaken for a tasty jellyfish. Plastics are able to trigger sensory responses in marine life at all levels of the food chain. Laboratory studies have successfully verified the uptake of microplastic particles by zooplankton, invertebrates, echinoderms, mussels, oysters, crabs, fish, and recently, under controlled and replicated conditions, even corals.

Photo by Florida Sea Grant / CC BY-NC-ND 2.0

Microplastics affecting human health

You may be asking yourself, well what does this have to do with me? Well, the uptake of microplastics into the food chain is just one example of the many ways in which microplastics end up in the food we eat.

Microplastic ingestion has been observed in a range of animals of marketable interest that are consumed by humans as food. These include fish that mistake microplastics for food (e.g. Atlantic cod, Atlantic horse mackerel, European pilchard, red mullet, European sea bass), bivalves (e.g. mussels, oysters), and crustaceans (e.g. brown shrimps).

Plastics in consumer products have increasingly drawn attention with regards to their potential effects on human health. Research has found the presence of microplastics and other artificial microparticles in human food and drinking water. For example, microplastics were found in canned sardines and sprats, salt, beer, honey, and sugar. Along with this, drinking water distributed in plastic bottles, glass bottles and beverage containers obtained from grocery stores in Germany were also found to contain microplastics as did tap water from different countries around the world. The occurrence of microplastics in other food items, therefore, increases concern about the risks associated with ingestion and long-term exposure to numerous microplastic sources.

Less than a few millimetres long, bundles of tiny fibres are just part of the microplastic load found in filter-feeding animals on the coast of the Western Cape - including mussels, a regular part of the human diet. Credit: Deen Hill

In addition to being used in food preservation methods, salts also provide important nutritional essentials to humans. They are used internationally to prepare our food and each of us ingests relatively small amounts of salt in numerous food items, such as freshly prepared meals, preserved food items (e.g., fruit, cheese, and cereals), with some of these containing surprisingly large amounts of salt. Salts also have an assortment of other uses, for example in the cosmetic and personal care products industry and pharmaceutical industry. Microplastics have been found in the sea salt of 128 international brands, from 38 different origins. 90% of the commercial salts samples analysed globally contained microplastics.

Bisphenol, a component of polycarbonate plastics (baby bottles, microwavable containers), is suspected of being an endocrine disruptor.  This is one of the most widely known “chemicals of interest” found in plastics. When consumed, components of plastics, as well as the chemicals and metals they release, can travel into the bodies of marine organisms where they may concentrate and climb the food chain and ultimately end up on our plates. The likely presence of human-made marine debris in seafood raises several questions regarding human health. For example, human-made debris can elicit a biological response through both physical and chemical mechanisms of toxicity. Small pieces of human-made debris have been shown to cause physical damage leading to cellular necrosis, inflammation and lacerations of tissues in the gastrointestinal tract. As such, human-made marine debris may cause physical harm to people when the debris is ingested through the consumption of seafood (e.g. in whole sardines, mussels, and oysters).

The additives to plastics and the organic pollutants that plastics can spread can potentially bioaccumulate, impacting our food web and becoming a threat that could have adverse effects on human health. In humans, eating microplastics has the potential of altering chromosomes which can lead to infertility, obesity, and cancer. Recently, the first documented case of microplastics found in human faeces was reported. The pilot study observed eight participants from different regions of the world, monitoring their daily food (including seafood) intake before sampling. Polystyrene (the plastic trays which hold meat and vegetables at supermarkets), polyurethane (furniture and carpets), and polyethene glycol (antifreeze, skin creams) were found in the participants’ stool samples. The research found that not all the microplastic particles were excreted, meaning there is a potential for negative health impacts. To understand human exposure, studies of health effects have been done on rats and mice. These tests used small plastic pieces soaked in salt water or alcohol. The study found that 70% of the plastics used released chemicals that acted similarly to estrogen. In mammals, chemicals that actively contain estrogen can create health problems such as early puberty within females, reduced sperm count, altered reproductive organs, obesity, altered sexual behaviours, and increased rates of breast, ovarian, testicular, and prostate cancer. These effects are expected to also be produced in humans, as the basic endocrine mechanisms have been consistent in all classes of vertebrates. Plastic, in general, has been known to have negative effects on human health. Patients that have had knee replacement surgery using plastic implants, have experienced disrupted cellular processes and degraded tissue.

The uptake of plastic particles by humans can occur through the drinking of water, consumption of terrestrial and aquatic food products, and inhalation. Despite seafood being a recognised source of contaminants in the human diet, the occurrence of microplastics in seafood is neither quantified nor regulated. Seafood may be contaminated with microplastics through ingestion of natural prey, adherence to the organism's surface or during the processing and packaging phase. A recent article by the World Economic Forum stated research that has found that humans eat up to 5 grams of plastic a week. That’s the equivalent of eating your credit card every week.

What next?

A considerable portion of the plastics produced globally ends up in the environment. In fact, plastics represent one of the fastest-growing portions of urban waste that contributes to environmental contamination and pollution. It accounts for roughly 60 -  80% of all marine litter, while even more alarmingly, reaching a staggering 90 - 95% in some areas. The worldwide annual plastic production has increased immensely in recent decades - from 1.5 million tonnes in the 1950s to approximately 335 million in 2016. Most of the plastics found in the marine environment originate from land-based sources, entering through rivers and other paths.

Research into the factors prompting microplastic ingestion by marine organisms, bioaccumulation factors for popular seafood species and their trophic connections are urgently needed. This will assist in identifying which species should be eaten in moderation or avoided altogether, compared with those that are considered safe to eat. The magnitude of microplastics in the environment is set to increase. 

Microplastic Analysis by Proyecto LIBERA / CC BY-SA 2.0

Consequently, this area of research requires urgent and thorough attention to discern the real impacts on human health. It can be seen that microplastics are not only affecting wildlife but we as humans are also at risk. We may not physically see it in our food or feel the effects in the short term but in the long term, it may have lasting consequences.

Thank you for sharing this information! Be sure to check out Braden's blog, Conservation Captured, for related content.

If you would like to be part of preventing the buildup of plastic pollution, please get involved in Plastic Free July.

References

Alamy, A. Pollution, M.P. & Safety, S. New Link in the Food Chain? Marine Plastic Pollution and Seafood Safety. 2015. Focus 123(2): 34–42.

Arreola, L. & Fulton, J. 2018. Microplastic Pollution in the Ocean Affecting Marine Life and its Potential Risk to Human Health.Dissertation: California State University, Sacramento, 1–41.

Carbery, M., Connor, W.O. & Thavamani, P. 2018. Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health. Environment International (115): 400-409.

Gabriel, L., Barboza, A., Vethaak, A.D., Lavorante, B.R.B.O., Lundebye, A. & Guilhermino, L. 2018. Marine microplastic debris : An emerging issue for food security, food safety and human health. Marine Pollution Bulletin, (133): 336–348.

Peixoto, D., Pinheiro, C., Amorim, J., Oliva-teles, L. & Natividade, M. 2019. Microplastic pollution in commercial salt for human consumption : A review. Estuarine, Coastal and Shelf Science, (219) 161–168.

 New Link in the Food Chain? .2015.Marine Plastic Pollution and Seafood Safety, 123(2): 34–42.

Rochman, C.M., Tahir, A., Williams, S.L., Baxa, D. V, Lam, R., Miller, J.T., Teh, F., Werorilangi, S. & Teh, S.J. 2015. Anthropogenic debris in seafood : Plastic debris and fibers from textiles in fish and bivalves sold for human consumption. Nature Publishing Group, 1–10.

Wright, S.L. & Kelly, F.J. 2017. Plastic and Human Health: A Micro Issue? Environmental Science & Technology, (51)12.

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