Size of Microplastics

Size definition of

Microplastics

current Status Overview

Currently, microplastics are predominantly defined as plastic particles smaller than 5 mm (Arthur et al., 2009). This definition includes most pellets, which are macroscopic and easily distinguished from fragments resulting from plastic breakdown. Pellets often have a different chemical composition, as they typically lack the chemical additives introduced during the compounding phase of plastic manufacturing.

LabPlas proposes defining microplastics as plastic particles below 1mm.

What the project proposes?

The current 5 mm upper limit for microplastics is based on pragmatism rather than actual evidence (Hartmann et al., 2019). The LabPlas Project consortium supports the idea that a size category must have an upper AND a lower boundary.

Furthermore, LabPlas proposes defining SMNPs (Small, Micro and Nano Plastics) as plastic particles below 10 µm.

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THE LABPLAS PROJECT PROPOSAL OF SETTING AN UPPER BOUNDARY FOR MICROPLASTICS (MP) <1 MM OFFERS SEVERAL ADVANTAGES......

It excludes industrial pellets, which do not contain the chemical additives added to manufactured plastics.

It is compatible with most common standard ISO mesh sizes.

It is in line with the international system (SI) of units.

It corresponds better with the limit of size that is no longer identifiable by the naked eye

SMNP

Additionally, the LabPlas project consortium is among the group of scientists that suggested the now generally accepted term, “small micro and nano-plastics (SMNP)”, needed to differentiate between plastic particles with different routes of exposure.

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the graph

“Because we cannot remove microplastics from the ocean, proactive action regarding research on plastic alternatives and strategies to prevent plastic from entering the environment should be taken promptly.”

- S. Oberbeckmann & M. Labrenz Ann. Rev. Mar. Sci. Vol. 12, January 2020

CONCLUSIONS

Microplastics are currently defined as plastic particles smaller than 5 mm. This includes macroscopic pellets, which are easily distinguishable from fragments resulting from plastic fragmentation.

Small Micro and Nano Plastics (SMNP): This term is used to designate plastic particles capable of getting across biological membranes.

The LabPlas project consortium supports defining large microplastics as plastic particles in the size range 10 micron to 1 mm, and small microplastics 1 micron to 10 micron” aligning with the International System of Units (SI).

The LabPlas Project proposes to define SMNP as plastic particles smaller than 10 µm.

curious about the LabPlas project?

The LabPlas project is focused on understanding the sources, transport, distribution and impacts of plastic pollution in all environmental compartments (freshwater, marine, terrestrial, atmosphere and aquatic biota).

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OUR TEAM IN ACTION!

Sampling sediment cores and the water column at the North Sea.

the LABPLAS team in action | Field and lab work

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“Excessive consumption of plastics, and the waste this generates, has a massive impact on the natural world and the marine environment in particular. […] if we are to avoid plastics ending up in the oceans, the solutions lie on land.”

- A. Abreu & M.L. Pedrotti Field Action Science Reports 19, 2019

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There is no consensus regarding the upper and lower size limits for microplastics, nor is there a clear scientific justification for the size being applied currently. When reported in 2004, the term microplastics was used to describe fragments of plastic around 20 μm in diameter (Thompson et al. 2015). The LabPlas consortium endorses R. Thompson’s perspective on the upper limit “perhaps a more intuitive boundary following the International System of Units classification of <1 mm” (Thompson et al. 2015).

Particles larger than 10 µm are unlikely to get across biological membranes. Also, from a practical standpoint, recent advances in microplastics sampling moved the lower threshold of catchable particles from the 100 µm of mesh techniques (manta trawl, plankton nets) to the 10 µm of filtering techniques and micro-FTIR characterization. This aligns with the 10 to 20 µm upper threshold of particle size ingested by most zooplanktonic organisms and efficiently retained by bivalve filter feeders. Furthermore, 10 µm is also a benchmark in atmospheric particle monitoring (PM10 and PM2.5), and below 10 µm, electrostatic surface charges become significant, causing aggregation with organic matter in cohesive sediment flocs, which represents a potential pathway of exposure via ingestion to aquatic organisms.

Based on these considerations, the LabPlas Project consortium proposes the size boundaries described in the graph.

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