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Microplatics

Plastic debris in the ocean is increasingly viewed as a signifcant threat to the health of the world's oceans and recent arguments have been drawn to classify it as hazardous. Plastic production has grown exponentially since first appearing on the market place in the early 20th century, with more than 280 million tonnes being produced annually today. This production has consequently led to a troubling conservation concern for many ocean species, with 60 to 80% of marine litter consisting of plastic debris. A report released by the Ellen MacArthur Foundation, which shows that by 2050.  Ninety per cent of the trash in the ocean is plastic and 54 per cent of that floats beneath the surface. For every six pounds of plastic in the ocean, there is only one pound of plankton (Crystal Schultz of the Bermuda Underwater Exploration Institute’s).

While larger, visible plastic debris has been implicated in the deaths of countless sea turtles, seabirds and marine mammals, there are more recent questions about the potential impacts from microplastics ( <5 mm) (Hanvey et al., 2017).

Microplastics are divided according to their size into “large microplastics” (1 - >5 mm) and “small microplastics” (1 μm - >1 mm) (Hanvey et al., 2017).


Nomenclature based on size (European MSFD technical subgroup on Marine Litter - MSFD GES Technical Subgroup on Marine Litter, 2013). The overall term “microplastic” is composed of small microplastics (SMPs, smaller than 1 mm) and large microplastics (LMPs, 1 to 5 mm), to differentiate between two commonly used definitions of microplastics. (Hanvey et al., 2017)


 

There are a wide variety of polymers detected in the environment, with the main types being polyethylene (PE), polypropylene (PP) and polystyrene (PS).

 

List of common types of plastics (abbreviation) and their common usage (Hanvey et al., 2017)
Type of plastic Abbreviation Application of virgin resin Density (g/cm3)
Polyethylene terephthalate PET/PETE Disposable beverage bottles, textiles (synthetic fibers), tape, Mylar food packaging and thermal insulation 1.37–1.38
High density polyethylene HDPE Plastic bags, plastic lumber, fuel tanks, bottle caps, milk crates 0.93–0.97
Polyvinyl chloride PVC Plumbing pipes, door and window frames, garden hoses, electrical cable insulation, inflatable products 1.10–1.47
Low density polyethylene LDPE Plastic bags and films six-pack rings, flexible snap-on lids 0.91–0.92
Polypropylene (expanded or non- expanded) PP Bottle caps, rope, carpet 0.89–0.92
Polystyrene (expanded or non- expanded) PS Disposable cutlery, dinnerware, and take-away food packaging, building insulation, refrigerated bins (e.g., fish boxes) 0.28–1.04
Other resins, such as polycarbonate, nylon, and acrylic Other Used for engineering purposes because of their thermal, electrical and chemical properties. e.g., electrical wire insulation 1.15–1.22

 

Microplastic are present in the environment as ‘microplastics by design’ (primary microplastics)or arise from the degradation of larger plastic litter (secondary microplastics). While the former are typically resin pellets and microbeads associated with industrial spillages and the use of cosmetics, the latter are formed through the action of degrading forces such as UV radiation and physical abrasion. Another important source comes from synthetic clothing: a single synthetic garment can release up to 1900 fibres per washing cycle. (Hanvey et al., 2017).

 

Researchers worldwide report on the uptake of microplastics by various marine organisms. Ingestion of microplastics may lead to potentially fatal injuries such as blockages throughout the digestive system or abrasions from sharp objects, which, in contrast to macroplastics, mainly affect microorganisms, smaller invertebrates or larvae. In addition to these physical effects on single organisms, the ecological implications can be even more severe as microplastics can release toxic additives upon degradation and accumulate persistent organic pollutants (POPs). Because of their minute size, microplastics harbor the risk of entering marine food webs at low trophic levels and propagating toxic substances up the food web. Microplastics harbor the risk of transporting POPs to human food. Because of their long residence time at sea plastics can travel long distances and thus function as vectors for dispersal of toxins and/or pathogenic microorganisms. However, although the potential risks associated with marine microplastics have recently been acknowledged the manifold impacts of microplastics on the ecosystems of the oceans have not been investigated in detail and are thus only poorly understood (Crichton et al., 2017).

 

Cites:

Crichton, E. M., Noël M., Gies E.A. & Ross, Peter S., 2017. A novel, density-independent and FTIR-compatible approach for the rapid extraction of microplastics from aquatic sediments. Anal. Methods, 9: 1419 - 1428.

Hanvey, J. S., Lewis P. J., Lavers J. L., Crosbie N. D., Pozo de K. & Clarke, B. O., 2017. A review of analytical techniques for quantifying microplastics in sediments. Anal. Methods, 9: 1369 - 1383.

 

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