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Microplastics – Sources, Risk and Regulation

November 30th, 2016

The presence of microplastics and microbeads[1] in the aquatic (freshwater and marine) environment has been a focus of much public debate over recent years, at both European and world-wide levels.

Regulators have been considering what actions are necessary to reduce microplastics in the environment. Meanwhile, a number voluntary commitments to phasing out microplastics have been implemented by the cosmetics industry (mainly in wash-off products). However, the cosmetics industry represents a minor contributor to the primary flow of microplastics into the environment, with the vast majority thought to originate from weathering and fragmentation of larger pieces of plastic over time, i.e. secondary microplastics.   

The potential ecological and human health risks of microplastics are relatively new areas of research, and the risks are not yet clearly defined, although in recent years many papers have been presented in conferences.

Evidence of exposure to marine biota is well documented, and there is some evidence from laboratory studies (field data is lacking) that uptake and transition into tissues, cells and organelles can occur. Physical effects of microplastics on aquatic species have been reported in laboratory studies with exposue to relatively high concentrations.

Microplastics can be associated with chemicals considered as contaminants from an ecotoxicological risk perspective (including POPs/PBTs). Such chemicals can include additives, monomers and by-products contained in plastic particles, and hydrophobic compounds and metals sorbed from surrounding seawater. Microplastics (and plastics in general) present an additional sorbent organic matter in the environment, to which hydrophobic contaminants can sorb. The amount sorbed will be in part dependent on concentrations in seawater.  It is difficult to quantifty the adverse effects caused by chemicals associated with microplastics, partly because seawater, sediment particles and biota are already contaminated by many of the chemical substances also associated with plastics. Although transfer of such pollutants from microplastics into lower-trophic-level organisms has been demonstrated in laboratory studies, modelling and experimental studies suggest that such transfer would be minor (or not significant) relative to the natural path. Indeed, in some cases, the presence of microplastics in diet has been shown to reduce uptake of such pollutants.

Regarding exposure of humans to microplastics, consumption of filter feeding invertebrates, such as mussels or oysters, appears the most likely route of human exposure to microplastics. However, there is no evidence to confirm this is occurring, and the understanding of the fate and toxicity of microplastics in humans constitutes a major knowledge gap.

The potential risks of microplastics (primary or secondary sources) to the environment and human health, especially regarding observed physical effects and evidence of transition into tissues and cells, suggests that there is a clear need to develop methods to more fully characterise the risks. In the meantime, a precautionary approach toward regulation of primary microplastic release to the environment seems appropriate. However, the wider issue of plastic waste in the environment should not be forgotten as an area that needs addressing.

[1] Microbeads is a term generally used to refer to spherical-shaped microplastics of less than 5mm in size used in cosmetics or PCPs, e.g. for exfoliation, to impart colour, film formation, viscosity regulation and as sorbent phase for delivery of active ingredients.