are small plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
particles in the environment
The biophysical environment is the combined modeling of the physical environment and the biological life forms within the environment, and includes all variables, parameters as well as conditions and modes inside the Earth's biosphere. The biophysical environment can be divided into two categories:...
and have become a paramount issue especially in the marine environment. Not unequivocally defined, some marine researchers define microplastics as all plastic particles smaller than 1 mm pertaining to their microscopic size range while others in turn define them as smaller than 5 mm recognizing the common use of 333 μm mesh neuston nets for field sampling. However, their integral impact on wildlife is scientifically not well established yet.
There are two main sources of microplastics:
- Microplastics which are produced either for direct use, such as for industrial abrasives, exfoliants, cosmetics or rotomilling or for indirect use as precursors (so called resin pellets or nurdles) for the production of manifold consumer products ("primary microplastics").
- Microplastics formed in the environment as a consequence of the breakdown of larger plastic material, especially marine debris, into smaller and smaller fragments (so called "secondary microplastics"). The breakdown is caused by mechanical forces (e.g. waves) and/or photochemical processes triggered by sunlight (especially UVB)
The abundance and global distribution of microplastics in the oceans has steadily increased over the last few decades with rising plastic consumption worldwide.
Potential impacts on the marine environment
The scientists that participated in the first International Research Workshop on the Occurrence, Effects and Fate of Microplastic Marine Debris, held September 9–11, 2008 on the University of Washington
University of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
Tacoma campus in Tacoma
Tacoma is a mid-sized urban port city and the county seat of Pierce County, Washington, United States. The city is on Washington's Puget Sound, southwest of Seattle, northeast of the state capital, Olympia, and northwest of Mount Rainier National Park. The population was 198,397, according to...
, Washington, USA, agreed that microplastics may pose problems in the marine environment based on the following:
- the documented occurrence of microplastics in the marine environment,
- the long residence times of these particles (and, therefore, their likely buildup in the future), and
- their demonstrated ingestion by marine organisms.
So far, research has mainly focused on larger plastic items. Widely recognized problems are associated with entanglement, ingestion, suffocation and general debilitation often leading to death and/or strandings. This raises serious public concern.
In contrast, microplastics are not as conspicuous, being less than 5 mm. Particles of this size are available to a much broader range of species and have been shown to be ingested by deposit-feeding lugworms (Arenicola marina) and filter-feeding mussels (Mytilus edulis) to name just two examples. Ingestion of microplastics by species at the base of the food web causes concern as little is known about its effects. It remains unknown if microplastics may be transferred across trophic levels.
Possible effects of microplastics on marine organisms after ingestion are threefold:
- physical blockage or damage of feeding appendages or digestive tract,
- leaching of plastic component chemicals into organisms after digestion, and
- ingestion and accumulation of sorbed chemicals by the organism."
Small animals are at risk of reduced food intake due to false satiation and resulting starvation or other physical harm. However, long term impacts on marine organisms are currently unknown.
Plastic debris has also been shown to serve as carrier for the dispersal of biota, thus greatly increasing dispersal opportunities in the oceans, endangering marine biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
worldwide. The dispersal of aggressive alien and invasive species is as much a topic as the dispersal of cosmopolitan species.
Approximately half of the plastic material introduced to the marine environment is buoyant, but fouling by organisms can induce the sinking of additional plastic debris to the sea floor, where it may interfere with sediment-dwelling species and sedimental gas exchange processes. However, this is of more importance for larger plastic debris.
Microplastics and persistent organic pollutants (POPs)
Furthermore, plastic particles may highly concentrate and transport synthetic organic compounds (e.g. persistent organic pollutants, POPs
-People:* Louis Armstrong, has the nickname "Pops"* Pops Fernandez , Maria Cielito Lukban Fernandez, a Filipina singer* Pops Foster , a jazz musician* Father Emmett Johns, * Pops Staples , a Gospel and R&B musician...
) commonly present in the environment and ambient sea water on their surface through adsorption. It still remains unknown, if microplastics can act as agents for the transfer of POPs from the environment to organisms in this way but evidence suggest this to be a potential portal for entering food webs. Not only do POPs raise concern. Additives added to plastics during manufacture may leach out upon ingestion, potentially causing serious harm to the organism. Endocrine disruption by plastic additives may affect the reproductive health of humans and wildlife alike.
At current levels, microplastics are unlikely to be an important global geochemical reservoir for POPs such as PCB
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...
Dioxins and dioxin-like compounds are by-products of various industrial processes, and are commonly regarded as highly toxic compounds that are environmental pollutants and persistent organic pollutants . They include:...
, and DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
in open oceans. It is not clear, however, if microplastics play a larger role as chemical reservoirs on smaller scales. A reservoir function is conceivable in densely populated and polluted areas, such as bights of mega-cities, areas of intensive agriculture and effluents flumes.
Oil based polymers ('plastics')are virtually non-biodegradable. However, renewable natural polymers are now in development which can be used for the production of biodegradable materials similar to that of oil-based polymers. Their properties in the environment, however, require detailed scrutiny before their wide use is propagated.
- Plastic particle water pollution
- Great Pacific Garbage Patch
The Great Pacific Garbage Patch, also described as the Pacific Trash Vortex, is a gyre of marine litter in the central North Pacific Ocean located roughly between 135°W to 155°W and 35°N to 42°N...
- Endocrine disruption
- Biodegradable plastic
Biodegradable plastics are plastics that will decompose in natural aerobic and anaerobic environments. Biodegradation of plastics can be achieved by enabling microorganisms in the environment to metabolize the molecular structure of plastic films to produce an inert humus-like material that is...
Plastic particles are an increasing cause of water pollution. The particles include nurdles, microbeads from cosmetics products and the breakdown products of plastic litter. Nurdles are pre-production plastic resin pellet typically under in diameter found outside of the typical plastics...
- Science Daily, Nov. 2, 2007. "'Microplastics' May Pose Previously Unrecognized Pollution Threat" (http://www.sciencedaily.com/releases/2007/10/071029092034.htm)