From the sea to the laboratory: Characterization of microplastic as prerequisite for the assessment of ecotoxicological impact.

The presence of microplastic (MP) in the aquatic environment is recognized as a global-scale pollution issue. Secondary MP particles result from an ongoing fragmentation process governed by various biotic and abiotic factors. For a reliable risk assessment of these MP particles, knowledge about interactions with biota is needed. However, extensive testing with standard organisms under reproducible laboratory conditions with well-characterized MP suspensions is not available yet. As MP in the environment represents a mixture of particles differing in properties (e.g., size, color, polymer type, surface characteristics), it is likely that only specific particle fractions pose a threat towards organisms. In order to assign hazardous effects to specific particle properties, these characteristics need to be analyzed. As shown by the testing of particles (e.g. nanoparticles), characteristics other than chemical properties are important for the emergence of toxicity in organisms, and parameters such as surface area or size distribution need consideration. Therefore, the use of "well-defined" particles for ecotoxicological testing (i.e., standard particles) facilitates the establishment of causal links between physical-chemical properties of MP particles and toxic effects in organisms. However, the benefits of well-defined particles under laboratory conditions are offset by the disadvantage of the unknown comparability with MP in the environment. Therefore, weathering effects caused by biological, chemical, physical or mechanical processes have to be considered. To date, the characterization of the progression of MP weathering based on powder and suspension characterization methods is in its infancy. The aim of this commentary is to illustrate the prerequisites for testing MP in the laboratory from 3 perspectives: (i) knowledge of particle properties; (ii) behavior of MP in test setups involving ecotoxicological test organisms; and (iii) accordingly, test conditions that may need adjustment. Only under those prerequisites will reliable hazard assessment of MP be feasible. Integr Environ Assess Manag 2017;13:500-504. © 2017 SETAC.

No measurable "cleaning" of polychlorinated biphenyls from Rainbow Trout in a 9 week depuration study with dietary exposure to 40% polyethylene microspheres.

Persistent hydrophobic chemicals sorbed to plastic can be transferred to fish and other aquatic organisms upon ingestion. However, ingestion of plastic could also lead to enhanced elimination of these chemicals if the plastic is less contaminated than the fish. Here, we attempted to measure the influence of ingestion of uncontaminated polyethylene microspheres on the depuration rates of polychlorinated biphenyls (PCBs) in an in vivo fish feeding experiment. Rainbow trout were given feed contaminated with PCBs for two consecutive days, then clean feed for three days to allow for egestion of the contaminated food. A control group of fish were then fed ordinary food pellets and a treatment group were fed pellets that additionally contained 40% by weight polyethylene microspheres. Condition factors and growth rates in both groups were similar, indicating no negative effect of the plastic microspheres on the nutritional status of the fish. Fish were sampled after zero, three, six and nine weeks, homogenized, solvent-extracted and analyzed by GC/MS. PCB concentrations declined in both groups at a rate consistent with growth dilution. There was no significant difference in the elimination rate constants between the control and treatment group, indicating that ingestion of uncontaminated plastic did not cause a measurable enhancement of depuration of PCBs by the fish in this study.