Image credit: Bo Eide/Wildlife Exchange: The rocky, bouldery parts of a coastline are effectively a micro plastics factory, breaking down larger pieces of plastic litter into ever smaller fragments.

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Turtles and Humans Face Some Surprisingly Similar Threats from Plastic Pollution: potential damage from micro plastics should concern us all.

Micro plastics have been found in all of the world’s seven species of sea turtle[1].

In a recent study of turtles from the Atlantic, Mediterranean and Pacific basins, 100% of those examined had ingested synthetic particles of less than 1mm in diameter. The micro plastics identified included polyethylene, ethylene propylene and polyester[2]. Micro plastics are also present in many of the products most commonly consumed by humans, including sugar, honey, salt, alcohol, bottled water, tap water and, inevitably, sea food[3].

‍Where is it all coming from?

Europe alone is responsible for dumping as much as 130,000 tonnes of micro plastics – including micro beads found in cleaning and cosmetic products, and fibres shed from synthetic material like fleece or lycra – into the sea. The Mediterranean is a particular hotspot, holding just 1% of the world’s waters but being the source of 7% of all micro plastic pollution[5].

Often molluscs and crustaceans ingest micro plastics into their tissues and are then in turn consumed by predators, including turtles, higher up the food chain. Indirectly ingested micro plastics have the potential to pass through cell membranes and accumulate in body tissues and organs, possibly leading to chronic effects, although the process and consequences are not yet well understood.

What does all this mean for turtles and other marine life?And what are the implications for human health?

Although research on the impact of micro plastics is growing rapidly, it is still relatively limited. Nevertheless, the studies that do exist suggest that “the concentration of micro plastics, (and the) size, colour, shape and polymer types found in the GI tract and faeces from sea turtles… and humans are similar, showing that they might be exposed to the same micro plastics profile”[6]. Polyethylene, for example, is a plastic polymer extensively used in fishing gear and now ubiquitous from top to bottom of the water column. It’s also used in food packaging, plastic bags and bottles, and is among the most abundant polymers inhuman drinking water[7].

The impact of micro plastic pollution on sea turtles can probably tell us a lot about its impact on our own bodies. And none of it is good news.

At a biochemical level, early indications from cell culture experiments have revealed that micro plastics can affect immune response, exacerbate oxidative stress, damage the integrity of cell membranes and even alter gene expression[8].

What are micro plastics and where do they come from?

Micro plastics are defined as plastic particles or beads which are less than 5mm in diameter and too small to be filtered out by water treatment plants. They have been identified in seawater worldwide and can be found in Arctic sea ice and snow. Their abundance in the marine environment and their tendency to both release and attract toxic chemicals has meant that they have come to be considered a pollutant in their own right[9].

As a result of their hydrophobic properties and large surface area to volume ratio, micro plastics encourage the accumulation of contaminants like heavy metals and endocrine disrupters such as polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE)from the surrounding environment. Contamination levels of micro plastics can be up to a million times that of surrounding seawater[10].

Along with other chemicals used in plastic production (like plasticizers), these substances can leach into animal tissue following ingestion. Although the extent to which this is happening is not yet well researched, there is evidence that PCBs found in the tissues of Great Shearwaters originated from ingested plastic particles[11].

Primary and Secondary Micro plastics

Micro plastics can be divided into primary micro plastics and secondary micro plastics. Primary micro plastics are most often associated with the tiny micro beads used in exfoliating cosmetic products, toothpastes and washing powders, and with the preproduction small plastic pellets or ‘nurdles’ used in the vast majority of plastic manufacture. They also have biomedical uses, being added to over-the-counter medications to make them easier to swallow, for example. Estimates suggest that cosmetic micro bead use in Europe alone could be adding nearly 9000 tonnes of plastic a year to the marine environment. A number of governments around the globe have now taken action aimed at prohibiting the use of micro beads in cosmetic products[12].

Other sources of primary micro plastics include acrylic, melamine or polyester micro beads used in air-blasting technology, to remove rust and paint from boats, engines and other machinery. These in particular are likely to become contaminated with heavy metals like cadmium, chromium and lead[13]. Primary micro plastic particles are also a by-product of the natural wear of car tyres, and of the breakdown of elastomer plastics used in products made from neoprene, lycra and silicone.

Secondary micro plastics result from the break-up of larger macro plastic items, when the integrity of the plastic is reduced as a result of wave action, exposure to UV radiation and physical abrasion in the sea or along shorelines. These physical, chemical and biological processes eventually result in the fragmentation of the macroplastics into microscopic particles.

It is already known that crabs which ingest microfibres exhibit changes in food consumption and energy levels, and that marine worms which ingest particles of polyvinylchloride (PVC) have reduced growth and energy reserves. Even sponges have been shown to ingest micro plastics, which can also adhere electrostatically to the surface of seaweed, presenting another possible pathway for their movement up the food chain[14].

What next?

Reducing plastic use, and in particular doing as much as wecan to curb micro plastic pollution, has never been more important. The implications for all who share the planet, ourselves included, are too important to ignore. At WVI we will continue to do our best to help sea turtles, including making sure sick and injured turtles admitted to rescue centres can return to the wild as healthy as possible, giving them the best chance to play their role in the survival of their species.

[1] Meaza, I., et al., Microplastics in Sea Turtles, MarineMammals and Humans: A One Environmental Health Perspective, Frontiers in EnvironmentalScience, February 2021, p4

[2] Duncan, E, et al. (2019) Microplastic ingestion ubiquitousin marine turtles. Global Change Biology, Vol. 25, 744-752

(2019); p746

[3] Meaza, I., et al., Microplastics in Sea Turtles, MarineMammals and Humans: A One Environmental Health Perspective, Frontiers in EnvironmentalScience, February 2021, p1

[5] WWF, Out of the plastic trap. Saving the Mediterranean fromplastic pollution, p10

[6] Meaza, I., et al., Microplastics in Sea Turtles, MarineMammals and Humans: A One Environmental Health Perspective, Frontiers in EnvironmentalScience, February 2021, p1

[7] Meaza, I., et al., Microplastics in Sea Turtles, MarineMammals and Humans: A One Environmental Health Perspective, Frontiers in EnvironmentalScience, February 2021, p13

[8] Meaza, I., et al., Microplastics in Sea Turtles, MarineMammals and Humans: A One Environmental Health Perspective, Frontiers in EnvironmentalScience, February 2021, p1

[9] Duncan, E, et al. (2019) Microplastic ingestion ubiquitousin marine turtles. Global Change Biology, Vol. 25, 744-752

(2019); p745

[10] Greenpeace, FFI, MCS, EIA (2016) MicrobeadsBriefing; https://www.mcsuk.org/media/ngo-microbeadsbriefing.

pdf:

[11] Greenpeace, FFI, MCS, EIA (2016) Microbeads Briefing;https://www.mcsuk.org/media/ngo-microbeadsbriefing.

pdf

[12] Flora and Fauna International (2017) Removing or RestrictingMicroplastic Ingredients or “Microbeads” from

Consumer and Industrial Products, Microbeads GuidanceDocument, Version 1; p13

[13] Cole, M., P.K. Lindeque et al. (2011) Microplastics ascontaminants in the marine environment: a review. Marine

Pollution Bulletin, Vol. 62 (12), 2588-97; p2589

[14] Duncan, E, et al. (2019) Microplastic ingestion ubiquitousin marine turtles. Global Change Biology, Vol. 25, 744-752

(2019); p748

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