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Stressor Exposures Determine Risk: So, Why Do Fellow Scientists Continue To Focus on Superficial Microplastics Risk? G. Allen Burton, Jr. University of Michigan, Ann Arbor, Michigan 48109, United States each with their own strengths and limitations, but no one is sufficient. High numbers of false positive and false negatives have been identified, depending on the methods used, which makes it impossible to compare microplastic studies that may be overestimating or under-estimating exposures.2,11,12 Nevertheless, the great majority of studies are stating the highest concentrations typically found are in the range of less than 1 to 10s of particles per meter squared (i.e., 1000 L).2,3,7,8,13,14 These concentrations are several orders of magnitude lower than virtually all laboratory studies and organisms feeding on this sized range will find orders of magnitude more plankton available for ingesting. Also, many of the studies measure concentrations based on mass (e.g., mg/L) or surface area (number/km2), and these units add large uncertainty to actual organism exposures to these diverse particles.3 As Editor-in-Chief of one of the premier journals for environmental toxicology, I find the continuing publication of microplastics studies stating a severe environmental threat, in high quality journals disturbing. These studies are rapidly picked up by the news media, as we have seen and serve to misinform the public and policy makers, as noted by others.6,15 Are reviewers and Associate Editors for our highest quality journals simply unaware of what constitutes hazard and risk and how exposure is the most important part of the equation? Since scientists should be nonbiased, how can this be happening? Is the penchant for visibility, pressure to publish, inability to publish negative results, funding, and sensationalism overtaken this science? This seems unethical. In the Environmental Science & Technology Feature by Koelmans et al.,6 they present a comprehensive coverage of these issues and propose and simple and eloquent path forward. In my opinion, this trend of reporting has adversely influenced policy making (e.g., the banning of microbeads one of the lesser components of microplastics and clearly not an environmental threat). The dominant component of microplastics characterized to date are not microbeads, rather polyester fibers or fragments (depending on which study cited), which are also below concentrations causing adverse effects. Nevertheless, there is no call by environmental advocates to ban polyester clothing or to ban all plastics which eventually will disintegrate to fragments. Colleagues in the industries affected by this ban have said privately at international scientific conferences it is a battle their respective companies have chosen not to fight. Well, that is wonderful, fewer microbeads being dischargedbut if there was no adverse exposure to begin withwhy care?
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couple of years ago, I tried to publish an Op-Ed challenging the perceived environmental threat of microplastics in the New York Times, Washington Post, LA Times, Chicago Times, and Wall Street Journalbut these respected news outlets rejected my submission. Subsequently, I published a Letter to the Editor in the journal Integrated Environmental Assessment & Management.1 This did little to change the concern expressed here. The focus on my opinion article was the concern that the environmental risk from microplastics (more specifically, microbeads) was overstated. As an environmental toxicologist and risk assessor, I knew low microplastic exposure concentrations dictated there could be no risk. Thankfully, others are now beginning to join this chorus.2−9 Even when scientific knowledge was in its infancy, Paracelsus stated in ∼500 AD a currently held, toxicological truth: All things are poisons at the right dose. My concern that microplastics in marine and freshwater ecosystems aquatic environment are not a risk due to LOW concentrations (i.e., low exposures) is slowly being realized and certainly applies to other contaminants of emerging concern. Recently, an Environmental Science & Technology Viewpoint article by Wiltje and Sumpter10 challenged scientists to better define environmentally relevant concentrations as all too often this term is loosely used. Numerous authors and organizations have called for standardized methods for collecting, quantifying, and characterizing microplastics.3,11,12 A plethora of methods exist for each of these three critical components of environmental assessments, © XXXX American Chemical Society
Received: October 25, 2017 A
DOI: 10.1021/acs.est.7b05463 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Environmental Science & Technology
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used for identification and quantification. Environ. Sci. Technol. 2012, 46, 3060−3075. (12) Vandermeersch, G.; Van Cauwenberghe, L.; Janssen, C. R.; Marques, A.; Granby, K.; Fait, G.; Kotterman, M.; Diogene, J.; Bekaert, K.; Robbens, J.; Devriese, L. A critical view on microplastic quantification in aquatic organisms. Environ. Res. 2015, 143, 46−55. (13) Baldwin, A. K.; Corsi, S. R.; Mason, S. A. Plastic Debris in 29 Great Lakes Tributaries: Relations to Watershed Attributes and Hydrology. Environ. Sci. Technol. 2016, 50, 10377−10385. (14) Beer, S.; Garm, A.; Huwer, B.; Dierking, J.; Nielsen, T. G. No increase in marine microplastic concentration over the last three decadesA case study from the Baltic Sea. Sci. Total Environ. 2017, DOI: 10.1016/j.scitotenv.2017.10.101. (15) McDevitt, J. P.; Criddle, C. S.; Morse, M.; Hale, R. C.; Bott, C. B.; Rochman, C. M. Addressing the issue of microplastics int he Wake of the Microbead-Free Water Act − A new standard can facilitate improved policy. Environ. Sci. Technol. 2017, 51, 6611−6617. (16) Huffer, T.; Praetorius, A.; Wagner, S.; von der Kammer, F.; Hofmann, T. Microplastic exposure assessment in aquatic environmewnts: Learning from similarities and differences to engineered nanparticles. Environ. Sci. Technol. 2017, 51, 2499−2507. (17) Syberg, K.; Khan, F. R.; Selck, H.; Palmqvist, A.; Banta, G. T.; Daley, J.; Sano, L.; Duhaime, M. B. Microplastics: Addressing ecological risk through lessons learned. Environ. Toxicol. Chem. 2015, 34, 945−953. (18) Sedlak, D. Three lessons for the microplastics voyage. Environ. Sci. Technol. 2017, 51, 7747−7748.
In addition, there are likely much higher exposures from “nanoplastics/nanoparticles” (less than the lowest size of 100 μm often measured for microplastics), but few have attempted to study this small size because of methodological challenges. Perhaps these ultrasmall particles are an environmental risk− but we do not know. Recent papers, suggest they share many traits of nanosize carbon and metal compounds and quickly aggregate in the environment. Much is to be learned from previous nanomaterial research.16,17 The process of determining microplastics risk should be an analysis of true risk (realistic exposure relationships to adverse effects). It should be documented in the field.3,6,18 Much greater and pervasive ecosystem risks often occur where microplastics are at their highest concentrations18 and are well-documented and rampant globally; including excess nutrients, low dissolved oxygen, solids from erosion, pathogens, altered flows, degraded habitats, temperature, and loss of shading. These common and major stressors should first be dealt with by regulators and environmental advocacy groups before focusing on the minor and questionable threats.
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AUTHOR INFORMATION
ORCID
G. Allen Burton Jr.: 0000-0002-8660-6294 Notes
Disclaimer: The author received no funding from the plastics or any microparticles organization. The author declares no competing financial interest.
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REFERENCES
(1) Burton, G. A., Jr. Losing sight of science in the regulatory push to ban microbeads from consumer products and industrial use. Integr. Environ. Assess. Manage. 2015, 11 (3), 346−347. (2) Cable, R. N.; Beletsky, D.; Beletsky, R.; Wigginton, K.; Locke, B. W.; Duhaime, M. B. Distribution and modeled transport of plastic pollution in the Great Lakes, the world’s largest freshwater resource. Front Environ. Sci. 2017, DOI: 10.3389/fenvs.2017.00045. (3) Connors, K. A.; Dyer, S. D.; Belanger, S. E. Advancing the quality of environmental microplastic research. Environ. Toxicol. Chem. 2017, 36, 1697−1703. (4) Galloway, T.; Cole, M.; Lewis, C. Interactions of microplastic debris throughout the marine ecosystem. Nat. Ecol. Evol. 2017, 1, 0116. (5) Koelmans, A. A.; Bakir, A.; Burton, G. A.; Janssen, C. R. Microplastic as a vector for chemicals in the aquatic environt: Critical review and model-supported reinterpretation of empirical studies. Environ. Sci. Technol. 2016, 50, 3315−3326. (6) Koelmans, A. A.; Besseling, E.; Foekema, E.; Kooi, M.; Mintenig, S.; Ossendorp, B. C.; Redondo-Hasselerharm, P. E.; Verschoor, A.; van Wezel, A. P.; Scheffer, M. Risks of plastic debris: Unravelling fact, opinion, perception, and belief. Environ. Sci. Technol. 2017, 51, 11513− 11519. (7) Lenz, R.; Enders, K.; Nielsen, T. G. Microplastic exposure studies should be environmentally realistic. Proc. Natl. Acad. Sci. U. S. A. 2016, 113, E4121−E4122. (8) Tang, B. L. Commentary: Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure. Front. Environ. Sci. 2017, DOI: 10.3389/fenvs.2017.00063. (9) Van Cauwenberghe, L.; Devriese, L.; Galgani, F.; Robbens, J.; Janssen, C. R. Microplastics in sediments: A review of techniques, occurrence and effects. Mar. Environ. Res. 2015, 111, 5−17. (10) Weltje, L.; Sumpter, J. P. What makes a concentration environmentally relevant? Critique and a Proposal. Environ. Sci. Technol. 2017, 51, 11520−11521. (11) Hidalgo-Ruz, V.; Gutow, L.; Thompson, R. C.; Thiel, M. Microplastics in the marine environment: A review of the metehods B
DOI: 10.1021/acs.est.7b05463 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
