You may have heard by now that plastic pollution is a big problem in the environment, particularly our oceans. However, did you know that there could be small pieces of plastic in the food you ate recently? These are called microplastics. Plastics are widely and intensively used by people with wide-ranging applications in numerous industries due to their low production cost, adaptability, lightweight, and durability, among other properties – but all those benefits have some potentially dangerous negatives.
What are Microplastics and how are they formed
Microplastics are tiny pieces of plastic that have been broken up over time. For example, let’s take an item such as a chip packet, 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 breakup and change of these large plastic pieces through biological, photo-, and mechanical degradation in the environment form these tiny particles, but 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 entry into the cells of organisms and induce adverse effects. 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 in remote locations. Recently, a plastic bag was even discovered on the floor of the Marianas Trench.
A recent study of foraging shorebirds shows that the breakdown of biofilms (microorganisms such as bacteria or fungi which cover the microplastic pieces) on the plastic surface yields a distinct smell (dimethyl sulphide) commonly associated with organic matter. This literally means that those little pieces of plastic smell like delicious food for them.
Researchers suggest sea turtles ingest plastics for the same reason, with visual signals also playing an important role, eg. aplastic bag floating in the ocean can be mistaken for a tasty jellyfish. Plastics are able to trigger sensory responses in marine life from all levels of the foodchain. Laboratory studies have successfully verified the uptake of microplastic particles by zooplankton, invertebrates, echinoderms, mussels, oysters, crabs, fish and recently coral under controlled and replicated conditions.
Microplastics affecting human health
You may be asking yourself, well what does this have to do with me? It’s a ripple effect and here is just one example of many ways microplastics get into the food we eat.
Microplastic consumption has been observed in a range of animals of marketable interest that are consumed by humans as food, including fish who 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 shrimp).
Plastics in consumer products have become subject to increasing attention in regards to their potential effects on human health. Research has found the presence of microplastics and other artificial microparticles in human food and ingredients to prepare it, and human 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 does tap water from different countries around the world. Therefore, the occurrence of microplastics in other food items 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.
Salts provide important nutrition essentials to humans and are used in food preservation methods. They are used internationally to prepare human food and each of us ingests relatively small amounts of salt in numerous food items, such as freshly prepared food, preserved food items (e.g., fruit, cheese, and cereals) some of which contain large amounts of salt. Salts also have an assortment of other uses, for example in the cosmetic and personal care products industry, pharmaceutical industry. Microplastics were found in sea salt of 128 salt 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. The components of plastics, as well as the chemicals and metals they release, can travel into the bodies of marine organisms upon consumption where they may concentrate and climb the food chain and ultimately end up in the people who eat them. 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 human-made debris has 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 via seafood (e.g. in whole sardines, mussels, and oysters).
The additives to plastics and the organic pollutants that plastics can spread have the perspective to be bioaccumulated, impacting our food web and becoming a threat that has adverse effects on human health. In humans, eating microplastics has the potential to alter chromosomes which can lead to infertility, obesity, and cancer. Recently the first documented report of microplastics found in human faeces was made. The pilot study observed 8 participants from different areas of the world, monitoring their daily food intake before sampling (included seafood). In the participant’s stool samples polystyrene (the plastic trays which hold meat and vegetables at supermarkets), polyurethane (furniture and carpets), and polyethene glycol (antifreeze, skin creams) were found. The research found that not all the microplastic particles were excreted, meaning there is a potential for negative health impacts. Studies of health effects have been done on rats and mice to understand human exposure. These tests used small pieces of plastic soaked in salt water or alcohol and found that 70%of the plastics used released chemicals that acted like estrogen. In mammals, chemicals that have estrogen activity 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 cancers. These effects are expected to be produced in humans, the basic endocrine mechanisms have been consistent with all classes of vertebrates. Plastic, in general, has been known to have negative effects on human health, patients that have had knee replacement surgery with plastic implants have experienced disrupted cellular processes and degraded tissue.
The uptake of plastic particles by humans can occur through the consumption of terrestrial and aquatic food products, drinking water and inhalation. Despite seafood being a recognised source of contamination to 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 states research has found the humans eat up to 5 grams of plastic a week. That’s as much as eating your credit card every week.
A considerable part of the plastic produced globally ends up in the environment. In fact, plastics represent one of the fastest-growing portions of the urban waste contributing to environmental contamination and pollution – accounting for roughly 60 to 80% of all marine litter, reaching 90 to 95% in some areas. The worldwide annual plastic production has increased greatly 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 come from land-based sources, entering through main 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 to identify which species should be eaten in moderation or avoided compared with those that are considered safe to eat. The magnitude of microplastics in the environment is set to increase, and 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 see it in our food or feel the effects in the short term but in the long term, it may have lasting consequences.
I would like to thank the Two Oceans Aquarium for being able to collaborate with them and procuring the photographs needed for this blog post. I would like to particularly thank Devon Bowen (Online Content Executive) for all his help.
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Florida Sea Grant