Kim, Shin Woong

Kim, Tae-Young

Rillig, Matthias C.

Waldman, Walter R.

English

Institutional Repository of the Freie Universität Berlin

The Global Plastic Toxicity DebtMatthias C. Rillig,* Shin Woong Kim, Tae-Young Kim, and Walter R. WaldmanCite This: Environ. Sci. Technol. 2021, 55, 2717−2719 Read OnlineACCESS Metrics & More Article RecommendationsPlastics are solids with an interior and a surface.Fragmentation of plastics in the environment, coupledwith the release of chemical additives from these plastics, leadto a potential future peak release of toxic compounds(including chemical additives and nanoplastics).Humanity has produced a staggering volume and diversity ofplastic materials. A significant proportion of this is accumulat-ing as waste in a range of environmental compartments. Thebehavior and fate of plastics in the environment is a complexissue, strongly influenced by the unique properties of a giventype of plastic, including shape and size, polymer type, theadditives and impurities present in the plastic and the extent ofprior environmental decay. The parameter space is so largethat we may never know how all plastic types interactchemically and physically in every environmental situation orimpact each unique ecosystem. Nevertheless, research in thisarea continues to make rapid and impressive progress,shedding light on many of these factors using short-termexperiments.One key aspect of plastic pollution has been mostlyoverlooked, relating to longer-term consequences of plasticdegradation and pollution release, and we call this the “toxicitydebt” (Figure 1). In conservation biology, the number ofspecies that are doomed to extinction because of habitat lossand fragmentation, but that have not yet gone extinct becauseof time lags to reach equilibrium conditions, are calledextinction debt.1 In analogy to this, we propose that there isa toxicity debt that we incur by having large amounts of plasticcurrently in the environment, exposed to degradation, but thathas many more years of decay and release of toxic compoundsto follow. This does not refer, therefore, to future pollutionwith plastic but to the current state of plastic pollution alreadypresent in the environment; but effects are of coursecompounded with any future pollution.What are the underlying causes of this toxicity debt? Thisdebt arises from a combination of three factors. First, plasticsare fundamentally solids, with a surface area and polymericmolecular structure. Second, all plastics contain additionalchemicals (additives), the purpose of which is to give certainproperties to plastics during their useful life; plastics may alsocontain additional unintentional chemicals (impurities), suchas catalyst residues, unreacted monomers or breakdownproducts.2 Selected additives and impurities possess toxicproperties, with implications for ecosystem and human health.Third, over time under environmental conditions, plasticsfragment into smaller pieces, increasing the surface area of thesolid plastic, further releasing trapped additives and impurities.The first two points, that plastics are solid bodies withadditives and impurities “stored” within the structural volumeof the plastic is a key property of this contaminant suite. Thesecompounds are not immediately released into the environ-ment, because this process is limited by slow rates of diffusionof the additive or impurity to the surface of the plastic item.Time scales over which additives and impurities are releasedfrom a plastic item vary extremely widely, from an estimatedbillions of years for brominated flame retardants to years forcertain plasticizers, such as phthalates, adipates, andtrimellitates.The third key point is that plastic items tend to fragment inthe environment. Termed microplastics when fragments arebelow 5 mm in size, such fragments can degrade further toreach nanoparticle size.3 Several crucial properties changealong this pathway to smaller particle sizes: the interior volumebecomes smaller, the surface area of the plastic fragmentReceived: November 17, 2020Published: February 17, 2021Viewpointpubs.acs.org/est© 2021 The Authors. Published byAmerican Chemical Society2717https://dx.doi.org/10.1021/acs.est.0c07781Environ. Sci. Technol. 2021, 55, 2717−2719Downloaded via FREIE UNIV BERLIN on May 3, 2021 at 09:13:14 (UTC).See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.increases, with the increasing release of additives andimpurities as the diffusion pathway to reach the fragmentsurface shortens. This means that we must expect largeramounts of potentially toxic compound cocktails to be releasedinto the environment that exponentially increase withincreasing time of environmental exposure of plastics. Thistime-delayed release of plastic additives and impurities forms alate pulse of potentially toxic compounds that contributes tothe toxicity debt.In addition, multiple smaller nanoplastic fragments arecreated, which can themselves give rise to toxic effects. Thetoxicity of nanoplastic fragments in the environment is an areaof active research, with detrimental impacts including oxidativestress, downregulated gene expression, and behavioraldisorders in aquatic organisms.4 This is a serious issue, sincethere are likely to be several orders of magnitude morenanoplastic particles in the environment than microplasticparticles. This time-delayed appearance of nanoplastics andtheir toxic effects may be much more severe than effects relatedto the current levels of toxic chemicals released from micro-and nanoplastics. We, therefore, explicitly include thisincreased production of nanoplastics in the environment inour concept of toxicity debt.Plastics have been produced at an industrial scale since the1950s. Given the production patterns, which have been steeplyincreasing, and the time scales of degradation with estimatedhalf-lives ranging from less than a year to several thousandyears depending on the plastic and its chemistry,5 we verylikely have not reached the peak of toxic release from the sumtotal of all environmentally available plastic on Earth. This is asobering thought.There are some immediate research needs that arise fromrecognition of this impending plastic toxicity debt, as well asimportant consequences for policy. First, we need tounderstand how different plastics fragment in the environmentand the time scales of fragmentation. This calls for innovativeapproaches that go beyond short-term laboratory incubationsand involve longer-term approaches. Second, we need to studythe release of additives, impurities, and other compounds fromdifferent plastic chemistries and piece sizes under environ-mentally relevant conditions, including in water, soil, or wheningested by organisms. We know comparatively little about themigration behavior of the various types of additives out ofplastic pieces in the environment. This is because studies onmigration behavior have typically addressed plastic materialsduring their useful life, for example when packing material is incontact with food.6On the policy side, this realization of a toxicity debt shouldbecome an additional, central argument in the discussion tocurb single-used plastic use and to encourage the developmentof more intelligent polymers, designed for performance duringtheir entire life cycle, including after end of life. Additionally,we need to include additives in policy considerations: behaviorof additives should not only be appraised during the useful lifeof plastic but also in terms of their future release to theenvironment.■ AUTHOR INFORMATIONCorresponding AuthorMatthias C. Rillig − Freie Universität Berlin, Institute ofBiology, 14195 Berlin, Germany; Berlin-BrandenburgInstitute of Advanced Biodiversity Research (BBIB), 14195Berlin, Germany; orcid.org/0000-0003-3541-7853;Email: rillig@zedat.fu-berlin.deAuthorsShin Woong Kim − Freie Universität Berlin, Institute ofBiology, 14195 Berlin, Germany; Berlin-BrandenburgInstitute of Advanced Biodiversity Research (BBIB), 14195Berlin, Germany; Department of Environmental HealthScience, Konkuk University, Seoul 05029, Republic of Korea;orcid.org/0000-0002-1434-9444Tae-Young Kim − School of Earth Sciences andEnvironmental Engineering, Gwangju Institute of Science andTechnology, Gwangju 61005, Republic of Korea;orcid.org/0000-0002-8846-3338Walter R. Waldman − Science and Technology Center forSustainability, Federal University of São Carlos, Sorocaba,São Paulo 18052-780, Brazil; orcid.org/0000-0002-7280-2243Complete contact information is available at:https://pubs.acs.org/10.1021/acs.est.0c07781NotesThe authors declare no competing financial interest.■ ACKNOWLEDGMENTSM.C.R. acknowledges funding from an ERC Advanced Grant(694368), from the Federal Ministry of Education andResearch (BMBF; projects BIBS and μPlastic), and theDeutsche Forschungsgemeinschaft. S.W.K. acknowledges apostdoctoral grant from the National Research Foundation ofKorea funded by the Ministry of Science, ICT, and FuturePlanning (2019R1A6A3A03031386). T.Y.K. acknowledgesFigure 1. Development of an environmental plastic toxicity debt.Environmental Science & Technology pubs.acs.org/est Viewpointhttps://dx.doi.org/10.1021/acs.est.0c07781Environ. Sci. Technol. 2021, 55, 2717−27192718support from the National Research Foundation of Korea(2019R1A2C1007170). W.R.W. acknowledges a Capes-Humboldt Research Fe l lowsh ip (1203128-BRA-HFSTCAPES-E-Finance code 001).■ REFERENCES(1) Tilman, D.; May, R. M.; Lehman, C. L.; Nowak, M. A. HabitatDestruction and the Extinction Debt. Nature 1994, 371 (6492), 65−66.(2) Zimmermann, L.; Dierkes, G.; Ternes, T. A.; Völker, C.; Wagner,M. Benchmarking the in Vitro Toxicity and Chemical Composition ofPlastic Consumer Products. Environ. Sci. Technol. 2019, 53 (19),11467−11477.(3) Kwak, J. I.; An, Y.-J. Microplastic Digestion GeneratesFragmented Nanoplastics in Soils and Damages EarthwormSpermatogenesis and Coelomocyte Viability. J. Hazard. Mater.2021, 402, 124034.(4) Lehner, R.; Weder, C.; Petri-Fink, A.; Rothen-Rutishauser, B.Emergence of Nanoplastic in the Environment and Possible Impacton Human Health. Environ. Sci. Technol. 2019, 53 (4), 1748−1765.(5) Chamas, A.; Moon, H.; Zheng, J.; Qiu, Y.; Tabassum, T.; Jang, J.H.; Abu-Omar, M.; Scott, S. L.; Suh, S. Degradation Rates of Plasticsin the Environment. ACS Sustainable Chem. Eng. 2020, 8 (9), 3494−3511.(6) Hahladakis, J. N.; Velis, C. A.; Weber, R.; Iacovidou, E.; Purnell,P. An Overview of Chemical Additives Present in Plastics: Migration,Release, Fate and Environmental Impact during Their Use, Disposaland Recycling. J. Hazard. Mater. 2018, 344, 179−199.Environmental Science & Technology pubs.acs.org/est Viewpointhttps://dx.doi.org/10.1021/acs.est.0c07781Environ. Sci. Technol. 2021, 55, 2717−27192719

The Global Plastic Toxicity Debt

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The Global Plastic Toxicity Debt

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