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The ubiquitous pollution of the environment with microplastics, a diverse suite of contaminants, is of growing concern for science and currently receives considerable public, political, and academic attention. The potential impact of microplastics in the environment has prompted a great deal of research in recent years. Many diverse methods have been developed to answer different questions about microplastic pollution, from sources, transport, and fate in the environment, and about effects on humans and wildlife. These methods are often insufficiently described, making studies neither comparable nor reproducible. The proliferation of new microplastic investigations and cross-study syntheses to answer larger scale questions are hampered. This diverse group of 23 researchers think these issues can begin to be overcome through the adoption of a set of reporting guidelines. This collaboration was created using an open science framework that we detail for future use. Here, we suggest harmonized reporting guidelines for microplastic studies in environmental and laboratory settings through all steps of a typical study, including best practices for reporting materials, quality assurance/quality control, data, field sampling, sample preparation, microplastic identification, microplastic categorization, microplastic quantification, and considerations for toxicology studies. We developed three easy to use documents, a detailed document, a checklist, and a mind map, that can be used to reference the reporting guidelines quickly. We intend that these reporting guidelines support the annotation, dissemination, interpretation, reviewing, and synthesis of microplastic research. Through open access licensing (CC BY 4.0), these documents aim to increase the validity, reproducibility, and comparability of studies in this field for the benefit of the global community.
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Title: Reporting guidelines to increase the
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reproducibility and comparability of
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research on microplastics
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Authors:
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Win Cowger1, Andy M. Booth2, Bonnie M. Hamilton3, Clara Thaysen3, Sebastian
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Primpke4, Keenan Munno3, Amy L. Lusher5, Alexandre Dehaut6, Vitor P. Vaz7, Max
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Liboiron8, Lisa I. Devriese9, Ludovic Hermabessiere3, Chelsea Rochman3, Samantha N.
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Athey3, Jennifer M. Lynch10,11, Hannah De Frond3, Andrew Gray1, Oliver A.H. Jones12,
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Susanne Brander13, Clare Steele14, Shelly Moore15, Alterra Sanchez16, Holly Nel17.
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1. University of California, Riverside, 900 University Ave, Riverside, California, 92521, United
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States of America
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2. SINTEF Ocean, SINTEF Sealab, Brattørkaia 17 C, 7010 Trondheim
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3. University of Toronto, Department of Ecology and Evolutionary Biology, 25 Willcocks Street,
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Toronto, Ontario, Canada M5S 3B2
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4. Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Biologische Anstalt
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Helgoland, Kurpromenade 201, 27498 Helgoland, Germany.
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5. Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, Oslo, Norway, NO-0349
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6. ANSES - Laboratoire de Sécurité des Aliments, Boulevard du Bassin Napoléon, 62200 Boulogne-
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sur-Mer (France)
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7. Federal University of Santa Catarina, Eng. Agronômico Andrei Cristian Ferreira St., Florianópolis,
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Santa Catarina, 88040-900
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8. Memorial University, IIC-3003. Memorial University of Newfoundland St. John's, NL, Canada A1C
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5S7
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9. Flanders Marine Institute (VLIZ), InnovOcean site, Wandelaarkaai 7, 8400 Ostend, Belgium
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10. Chemical Sciences Division, National Institute of Standards and Technology, Waimanalo, HI
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96795
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11. Center for Marine Debris Research, Hawaii Pacific University, Center for Marine Debris
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Research, 41-202 Kalanianaole Hwy Ste 9, Waimanalo, HI 96795
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12. RMIT University, Australian Centre for Research on Separation Science (ACROSS), School of
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Science, RMIT University, Bundoora West Campus, PO Box 71, Bundoora, Victoria 3083,
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Australia
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13. Oregon State University, 1007 Agricultural and Life Sciences Building
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14. California State University, Channel Islands, 1 University Drive, California State University,
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Channel Islands, Camarillo CA 93012
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15. San Francisco Estuary Institute, 4911 Central Ave, Richmond, CA 94804
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16. University of Maryland College Park, Civil and Environmental Engineering, 1173 Glenn L. Martin
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Hall, 4298 Campus Dr. College Park, MD 20742
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17. University of Birmingham, School of Geography, Earth and Environmental Sciences, University of
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Birmingham, Birmingham, Edgbaston, B15 2TT, UK
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Visual Abstract:
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Abstract:
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The ubiquitous pollution of the environment with microplastics - a diverse suite of
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contaminants - is of growing concern for science and currently receives considerable
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public, political, and academic attention. The potential impact of microplastics in the
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environment has prompted a great deal of research in recent years. Many diverse
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methods have been developed to answer different questions about microplastic
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pollution, from sources, transport, and fate in the environment, and about effects on
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humans and wildlife. These methods are often insufficiently described, making studies
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neither comparable nor reproducible. The proliferation of new microplastic investigations
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and cross-study syntheses to answer larger scale questions are hampered. We - a
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diverse group of 23 researchers - think these issues can begin to be overcome through
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the adoption of a set of reporting guidelines. This collaboration was created using an
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open science framework that we detail for future use. Here, we suggest harmonized
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reporting guidelines for microplastic studies in environmental and laboratory settings
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through all steps of a typical study, including best practices for reporting materials,
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quality assurance/quality control, data, field sampling, sample preparation, microplastic
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identification, microplastic categorization, microplastic quantification, and considerations
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for toxicology studies. We developed three easy to use documents - a detailed
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document, a checklist, and a mind map - that can be used to reference the reporting
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guidelines quickly. We intend that these reporting guidelines support the annotation,
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dissemination, interpretation, reviewing, and synthesis of microplastic research.
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Through open access licensing (CC BY 4.0), these documents aim to increase the
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validity, reproducibility, and comparability of studies in this field for the benefit of the
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global community.
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Keywords
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Harmonization; Standardization; Plastic; Microplastic; Metadata; Reproducibility; Open
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Science; Methods; Reporting guidelines; Comparability
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Introduction:
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The state of method reporting for investigations on microplastic pollution is currently at a
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turning point.1 As this new research field evolves, it is striving to establish a harmonized
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community approach to developing, applying, and reporting methodologies. Two of the
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main purposes for reporting scientific methods are to allow for their replication and
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enable data to be directly comparable among studies. For example, in the
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environmental sciences, data from studies might be compared during risk assessments,
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synthesized for meta-analyses, or used to inform policy creation and monitoring
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guidelines. Issues with reproducibility and comparability of both data and methods are
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common across all scientific fields,24 including microplastic research.1,5,6 Here, we - a
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diverse group of 23 microplastic researchers from around the world - present a
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proposed step towards addressing this issue for microplastics, first by capturing what is
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already in published literature, and then by prioritizing which types of information should
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be included in research to reach this goal. Our four aims are to 1) review key
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reproducibility and comparability problems and solutions for microplastic research; 2)
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discuss the open science framework used to identify and prioritize key methodological
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parameters suggested here; 3) develop reporting guidelines for researchers to use
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when reporting, comparing, and developing methods; and 4) present our vision for
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future microplastic research.
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The reproducibility and comparability
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turning point in microplastics research
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It is well-known that microplastics have a ubiquitous presence in the environment,710
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and the potential harm microplastics can cause to species across trophic levels has
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been recently reviewed.11,12 While there is mixed evidence for effects, a range of
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suborganismal, organismal and population-level responses have been reported.6,11,13
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These results have spurred substantial research activity, as evidenced by the continued
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exponential growth in the published literature on the topic of microplastics (Figure 1).
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Figure 1: Data acquired from Scopus on April 8th, 2020 using the search term "microplastic*"
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and querying the field of Environmental Sciences. Publications are annual sums. The figure was
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created using Python 3.6.9.
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The rapid expansion of research activities and the resulting data generated in the field
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of microplastics has resulted in a diverse suite of methods and non-standardized
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approaches to reporting sample collection, extraction, and analysis.1,1421 Each method
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has its strengths and weaknesses, and there are continued efforts to optimize existing
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methods and develop new ones that may improve throughput, detection limit, and
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reproducibility. The development of new methods continues because currently there is
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no 'catch-all' combination of methods for sampling, extracting, analyzing, and reporting
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microplastics that is capable of accurately characterizing and quantifying all
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microplastics present in a sample.22,23 This is because microplastics are a diverse suite
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of contaminants that vary greatly in morphology, chemical properties, texture, color,
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density, and size.24 Moreover, environments and research goals are diverse and a
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universal solution is unable to capture this diversity, especially as research matures in
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this rapidly expanding field. With this in mind, methods should be chosen based on the
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scientific question and reported with enough detail to be comparable and reproducible.
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Comparability between studies facilitates meta-analysis,25,26 which has been difficult for
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microplastics due to the diversity of methods employed and study details reported.1721
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Incomparability is caused by studies published without documenting the elements
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essential for translating units and metrics to others that are commonly used in the field.
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For example, studies that employ Raman spectroscopy might not be comparable to
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those that employ Fourier-transformed infrared (FTIR) spectroscopy if neither describes
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their analysis and data transformation steps.18,27 Additionally, aquatic studies that use
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water volume grab sampling are not comparable to studies that use net sampling if the
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studies do not describe the mesh size used, depth of sample collection, or the sample
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volume.28 In another example, ingestion studies on the same species of animal are not
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comparable if they fail to mention which part of the gastrointestinal tract was analyzed
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(e.g., just the gizzard or the gizzard and proventriculus of birds).15,17 Moreover, a study
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using different chemical digestion methods to measure ingestion may be incomparable
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because some digestion procedures destroy certain plastics.29 Regardless of diverse
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methods and wherever possible, reporting raw - or less processed - data would allow
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reverse engineering and harmonization of some techniques. Still, raw data are seldom
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reported.16,30
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Factors that cause incomparability can also hinder the reproducibility of research.
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Irreproducible research occurs, in part, when the elements that are critical for
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reproducing similar results are not elucidated. Reproducibility allows responsible
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decision-making and expansion of protocols. For example, software names should be
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reported when used because software often has proprietary algorithms and may not be
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reproducible unless the same software is used. In another example, if a study that
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employs organic matter digestion does not describe the chemical solution used, its
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manufacturer, and concentration used to digest the sample, the study cannot be
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reproduced.
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Reporting guidelines provide a structured framework where method information critical
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to comparing and reproducing research can be referenced. There is a critical need for
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reporting guidelines in microplastic research as already initiated with the Minimum
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Information for Microplastic Studies "MIMS" concept for the study of microplastics in
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seafood,1 the minimum information for publication of infrared-related data,27 and other
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works assessing data quality in microplastic studies.3133 The reporting guidelines we
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developed attempt to build on previous work and expand the scope to more
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methodological components in microplastic research. This study leverages the expertise
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of a diverse group of researchers from around the world to cover the breadth of the
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field. To be as transparent as possible, we elaborate on the reasons why each reporting
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guideline is necessary, and provide examples for each. Other fields, like molecular
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biology,34 proteomics,35 and transcriptomics,36 already have highly successful examples
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of reporting guidelines that have been widely adopted by their field, and we hope this
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work serves a similar purpose in our field.
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Methods:
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As a scientific community, we recognize that the need for reporting guidelines for
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microplastic methods is best addressed through a collaborative open science
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framework. With this goal in mind, the lead author sent out the following request on
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Twitter, and tagged several scientists in the microplastic community with a link to a
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collaborative document:
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"Frustrated with the reproducibility crisis in #microplastics research from poor method
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descriptions? Now is your chance to change that. I will publish this collaborative
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document OA [Open Access]. Add method considerations to this document and cite
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yourself in the Ack [Acknowledgements]." (Win Cowger, @Win_OpenData, June 13th,
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2019).
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The collaborative document was hosted open access on Google Drive and researchers
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were invited to provide input on the reporting guidelines for microplastic research
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methods. Over the subsequent week, 15 contributors edited the shared document
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directly. After one week, all initial contributors were invited to be coauthors, and
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additional coauthors were invited by word of mouth throughout the process using an
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open door policy. Overall, there were 23 authors on this project and 26 other people
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acknowledged for their assistance. In a meeting of coauthors, the threshold for co-
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authorship was set at one full day of effort (self defined and self reported), while the
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threshold for acknowledgement was to review the document at least once. Authors
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contributed to this publication and the reporting guideline documents. The first author
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(Cowger) led the collaboration and the author order after the first author was
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randomized by agreement of all coauthors.
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The reporting guidelines were identified by referencing standard operating procedures
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used by various authors and other peer-reviewed publications. All authors agreed not to
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use language that would imply an intent to standardize methodology or recommend
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specific methods over others; this was beyond the scope of the work. The task of the
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authors in developing the reporting guidelines was to outline what should be reported
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about a method when the method was used to make the method reproducible and
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comparable. To determine which guidelines were essential to add to the documents,
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each author was asked to fill out a Google Form survey where they designated each
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reporting category as required or not. The final reporting guidelines were formed by
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keeping only the guidelines that 51% or more of the authors agreed upon. During the
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review process, we received requests by reviewers to add additional reporting
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requirements. Where they were not already accounted for, we added them to the
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reporting guidelines and indicated those additions using an asterisk throughout the
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produced documents. The final reporting guidelines were packaged into three
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documents which have the same information summarized with specific user groups in
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mind: 1) thorough - a Detailed Document, 2) quick and simple - a Checklist (Table 1),
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and 3) interactive -an online Mind Map (Figure 2).
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The reporting guidelines were sent out to other colleagues in the field for an
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endorsement and critique designated as signatories in the acknowledgments. After the
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first week, we received 19 endorsements. The manuscript and supporting information
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were also subject to internal review at the National Institute of Standards and
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Technology and single blind peer review from Applied Spectroscopy. In these ways, we
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attempted to receive as much feedback as we could to develop reporting guidelines that
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reflect the diverse group of experts and the broad scope of methods in microplastic
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research. This framework represents an example of a way that scientists in any field
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can develop robust collaborations by sharing ideas and learning from one another while
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developing useful reference documents, even if they have not met before.
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Reporting Guideline Document
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Descriptions:
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The three documents we created of the reporting guidelines include a 1) Detailed
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Document, 2) Checklist (Table 1), and 3) online Mind Map (Figure 2). Each document
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has the same information summarized with different users in mind. These documents
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are expected to be useful for scientists researching microplastics, peer reviewers asked
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to evaluate research, and users of the data. These documents outline what needs to be
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reported for common methods in microplastic research to be reproducible and
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comparable. The documents can also be used when developing methods internally to
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quickly identify the essential components of a method to calibrate and control in a lab.
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The Detailed Document can be used when every detail listed in the reporting guidelines
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are important to know. The Checklist can be used to quickly reference the reporting
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guidelines and check off the guidelines relevant to a specific study. The Mind Map is
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useful for those who prefer interactive information workflows and want to be able to
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quickly summarize and expand the reporting guidelines at any level of detail.
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Any of these documents can be used to reference the report guidelines. All of the
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documents contain the same information reformatted and summarized. In the
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documents, the general method groups we define are: Materials, Quality Assurance /
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Quality Control (QA/QC), Data Reporting, Field Sampling, Sample Preparation,
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Identification, Categorization, and Toxicology Considerations. Subgroups describe
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specific method techniques within each group. Some of the groups may be used more
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than once in a study while some may not be used at all. It is important to note that these
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documents are templates and one need only consider the guidelines from the groups of
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methods relevant to a given study. When using the documents, first, assess which
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groups of methods apply to the study. Subgroups of methods are tab separated to
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indicate more detailed levels of grouping. Next, assess which of the subgroups apply.
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These can be highlighted or opened for easy reference. Where the most detailed
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subgroups apply, all italicized reporting guidelines must be defined, described, or
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discussed for that method to be reproducible and comparable. All reporting guidelines
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always apply to groups that do not have subgroups. Importantly, these reporting
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guidelines are not meant to completely define what should be reported but are a
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proposal for the minimum guidelines. Below we detail each document individually and
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outline a path forward for the documents to be updated.
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Detailed Document:
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The Detailed Document (SI1; OSF) is the plain-text thorough version of the reporting
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guidelines containing the identical information, groups, and order to the Checklist and
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Mind Map described below. While this document is the primary result of this project, its
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length precludes including it in the main manuscript. The Detailed Document is meant
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for those who are new to the methods or want a detailed description and reference
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examples of the reporting guideline. This document may also be useful to those who
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find the Mind Map format to be challenging to navigate. The Detailed Document is easily
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printed for reference, which can be especially useful during the design stage of a study.
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The format of this document follows that the highest level of method grouping is in the
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largest text font and bolded. Subgroups of methods are in bold and identical font size
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but further indented if they are a subgroup of a subgroup. The essential elements to
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report are italicized and all the same font size. The explanation, reason, and examples
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for each essential element immediately follow the element and are light gray in color.
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The Checklist:
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The Checklist (SI2; OSF; Table 1) is meant for those already familiar with the methods
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and reasons for reporting outlined in the other documents. The format follows the
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Detailed Document but the explanation, reason, and examples for each reporting
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guideline are removed for quick reference and reading so that the elements can be
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checked off when reviewing or writing documents. Citations used in the Detailed
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document are added at the end of each guideline. The reporting guidelines are italicized
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and all the same font size as in the Detailed Document.
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Table 1: This is the Checklist of the reporting guidelines. Asterisk (*) indicates that the guideline
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was added as part of peer review; all other guidelines were voted on by a majority of the
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coauthors. The guidelines are grouped using bolded and indented labels. The guidelines are
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italicized and are the furthest indented for each group. Citations correspond to additional
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information related to the guideline and good examples of reporting.
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Reporting Guidelines Checklist
Components to Report in All Procedures
materials
all manufacturers of materials and instruments and their calibration37
all software used and their calibration38
quality assurance/quality control
error propagation
how instrumental, methodological, and/or statistical error was propagated3941
replicates
number of replicates42
how replicates were nested within samples43
limit of detection
quantitative detection threshold44
plastic morphology, size, color, and polymer limitations of method1,29,53,4552
method of accounting for nondetects19,54
blank controls
number of controls1,31
characteristics of plastics found in blanks with the same rigor as samples45
potential sources of contamination55
point of entry and exit to method55
positive controls
morphology, size, color, and polymer type of positive controls1,31,56
positive control correction procedure31,56
point of entry and exit to method56
contamination mitigation
clothing policies1,57
purification technique for reagents50,58
glassware cleaning techniques59
containment used (e.g. laminar flow cabinet/hoods, glove bags)1,50,6062
data reporting
share raw data and analysis code as often as possible18,22,38,63,64
Field Sampling
where (e.g., region) and when (e.g., date, time) the sample was collected19,6570
size (e.g., m3, kg) and composition (e.g., sediment, water, biota) of the sample1,71
location at the site that sample was collected (e.g., 3 cm depth of surface sediment)72
sample device dimensions and deployment procedures14,31,7375
environmental or infrastructure factors that may affect the interpretation of results7581
how samples are stored and transported1,82,83
Sample Preparation
homogenization
homogenization technique84
splitting/subsetting
sample splitting/subsetting technique75
drying
sample drying temperature and time85
synthesized plastic
synthesized plastic polymer, molecular characteristics, size, color, texture, and shape86,87
synthesized plastic synthesis technique86,88
fluorescent dye
dye type, concentration, and solvent used8991
dye application technique89
sieving strategy
sieve mesh size84
if the sample was wet or dry sieved84
density separation
concentration, density, and composition (e.g. CaCl2, ZnCl) of solution82,92,93
time of separation94
device used61,9498
digestion
duration and temperature of digestion21,99,100
digestion solution composition21,56,100
ratio of digestion fluid to sample21,56,100,101
filtration
filter composition, porosity, diameter50,102,103
Microplastic Identification
visual identification
imaging settings
image settings (e.g., contrast, gain, saturation, light intensity)18
magnification (e.g., scale bar, 50X objective)104
light microscopy
magnification used during identification90
shapes, colors, textures, and reflectance, used to differentiate plastic104106
fluorescence microscopy
magnification used during identification90
fluorescence light wavelength, intensity, and exposure time to light source90,91,107
threshold intensity used to identify plastic107
scanning electron microscopy (SEM)
the coating used (e.g., metal type, water vapor)108
magnification used during identification108
textures used to differentiate plastic108
chemical identification
pyrolysis gas chromatography mass spectrometry (py-GC/MS)
pyrolysis reacting gases, temperature, duration49,109
GC oven program, temperature, carrier gas, and column characteristics49,109
MS ionization voltage, mass range, scanning frequency, temperature18,49
py-GC/MS matching criteria (i.e., match threshold, linear retention indices (LRI), and Kovats
index)49,110
py-GC/MS quantification techniques109
Raman spectroscopy
acquisition parameters (i.e., laser wavelength, hole diameter, spectral resolution, laser
intensity, number of accumulations, time of spectral acquisition)37,63,111115
pre-processing parameters (i.e., spike filter, smoothing, baseline correction, data
transformation)56,112,115,116
spectral matching parameters (i.e., spectral library source, range of spectral wavelengths
used to match, match threshold, matching procedure)37,50,63,70,111115,117
Fourier-transform infrared spectroscopy (FTIR)
acquisition parameters (i.e., mode of spectra collection, accessories, crystal type, background
recording, spectral range, spectral resolution, number of scans)63,64,103
pre-processing parameters (i.e. fourier-transformation (ft) parameters, smoothing, baseline
correction, data transformation)18
matching parameters (i.e., FTIR spectral library source, match threshold, matching procedure,
range of spectra used to match)38,50,64,112
differential scanning calorimetry (DSC)
acquisition parameters (i.e., temperature, time, number of cycles)20
matching parameters (i.e., parameters assessed, reference library source, comparison
technique)20
Microplastic Categorization
shape, size, texture, color, and polymer category definitions24,118,119
Microplastic Quantification
units (e.g., kg, count, mm)1,120
size dimensions (e.g., feret minimum or maximum)18
quantification techniques18
Toxicology Considerations
dosed plastic age, polymer, size, color, and shapes121130
animal husbandry131,132
exposure concentration, media, and time132138
effects evaluation metrics (e.g., what markers were evaluated?)*
biota metrics (e.g., which tissues were analyzed?)*
Mind Map:
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The Mind Map (SI3; LINK; OSF; Figure 2) was developed because we recognized a
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need to have many intermediate levels of detail between the detail provided by the
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Detailed Document and the Checklist. Interactive mind map documents allow the user
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to query to the level of detail they need quickly. This is meant for users who prefer
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spatially structured interactive information queries. The Mind Map was formatted using
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www.mindmeister.com, a free collaborative mind map creator that can reformat mind
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maps into tiered documents. The Mind Map is structured the same as the Detailed
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Document, where general method groups flow from the primary term 'Microplastics
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Reporting Guidelines.' These general groups are further refined by subgroups of
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method types and instrument groups, where the terminal node of every branch leads to
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essential methodology elements (italicized) that should be reported. Each reporting
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guideline is described by an explanation, reasons to report, and/or examples from
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published microplastic literature.
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Figure 2: A screenshot of the Mind Map (LINK) showing the components and flow of reporting
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guidelines for microplastic studies. The first nodes branching off of "Microplastic Reporting
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Guidelines" are the general groups of the guidelines, subgroups follow in bold until the second
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to last nodes are the reporting guidelines (in italic) and the terminal node is the description of
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the guideline.
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Strategy for Updating the Reporting Guidelines:
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The field of microplastic research is rapidly evolving, and we expect that our documents,
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like most things in science, will need to be adapted, expanded, and revised. We
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recognize that as the field of microplastic pollution develops and grows, there will be
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new techniques and methods developed that will have reporting guidelines. We also
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acknowledge other methods are already useful to report that are not yet covered here.
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These documents are expected to be updated over time as new techniques are
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developed. That is why all documents are completely free and hold open access
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licenses (CC BY 4.0). The license allows for redistribution and adaptation with
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attribution to the original document. Additionally, we created an Open Science
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Framework project (OSF) for each document where researchers can reach out with
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suggestions and comments to update future editions of these documents. The authors
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will monitor the comments on the project and respond as necessary. Future versions
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will be updated periodically on the OSF project site using version control. Additionally,
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we submitted this reporting guideline and others reported in the literature1,27 to the
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reporting guideline portal at https://fairsharing.org/. We hope that these documents and
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online forums are widely used for the benefit of the global community.
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Our vision of the future of research on
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microplastics:
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We envision a future where research on microplastics is comparable, reproducible, and
314
transparent. We aim for researchers in the field to be able to read a paper and use the
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methods for their work and/or use the data in a synthesis paper or meta-analysis. We
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aim for policy-makers and managers to be able to review the literature and have the
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ability to compare data across sources, pathways, and geographies to inform the
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decision-making process. We envision a field where communication is clear amongst
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different stakeholders in the world of microplastics and where collaboration and
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research translation are made simpler. With our collaborative and open access
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framework, we aim to improve future work on microplastics and provide a framework for
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other emerging contaminants.
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Disclaimer:
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Certain commercial equipment, instruments, or materials are identified in this paper to
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specify adequately the experimental procedure. Such identification does not imply
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recommendation or endorsement by the National Institute of Standards and
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Technology, nor does it imply that the materials or equipment identified are necessarily
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the best available for the purpose.
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Acknowledgments:
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The authors would like to thank Justine Ammendolia, Sarah Nelms, Kristian Parton, Jessica
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Melvin, Matthew Cole, Shannon Tarby, and Alexander Turra for their helpful input throughout
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the writing and envisioning process. Additionally, we would like to thank those who endorsed the
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document that we developed: Greg Sambrook Smith, Claire Gwinnett, Dorthy Horn, Katie Allen,
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Jesse Vermaire, Garth Covernton, Francois Galgani, Pernilla Carlsson, Zacharias Steinmetz,
335
Tanja Kögel, Louise Feld, Jakob Strand, Meredith Seeley, Bethanie Carney Almroth, Timothy
336
Hoellein, Jessica Melvin, Katrin Wendt-Potthoff, Scott Coffin, and Susannah Bleakley.
337
338
We also thank our funders. W. Cowger was funded by the National Science Foundation
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Graduate Research Fellowship Program. A. Booth received funding from the Research Council
340
of Norway through the Joint Programming Initiatives (JPI) Oceans project 'PLASTOX: Direct and
341
indirect ecotoxicological impacts of microplastics on marine organisms' (grant agreement No.
342
257479) and the project 'MICROFIBRE: Evaluating the fate, effects and mitigation measures for
343
microplastic fibre pollution in aquatic environments' (grant agreement No. 268404). C. Thaysen
344
was funded by the Herbert W. Hoover Foundation. S. Primpke was funded by the German
345
Federal Ministry of Education and Research (Project BASEMAN (JPI-Oceans) - Defining the
346
baselines and standards for microplastics analyses in European waters; Federal Ministry of
347
Education and Research (BMBF) grant 03F0734A). A. Dehaut is thankful to the French National
348
Research Agency (ANR-15-CE34-0006-02), as part of the Nanoplastics project. He is also
349
grateful to different bodies, as his contribution has been carried out thanks to the financial
350
support of the European Union (ERDF), the French State, the French Region Hauts-de-France
351
and Ifremer, in the framework of the project CPER MARCO 2015-2020. V. Vaz was funded by
352
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). M. Liboiron was
353
funded by the Office of the Vice President Research, Memorial University; Social Sciences and
354
Humanities Research Council; Northern Contaminants Program (NCP), and Memorial's
355
Undergraduate Career Experience Program (MUCEP) program. A. Gray was funded in part by
356
the United States Department of Agriculture's (USDA) National Institute of Food and Agriculture,
357
Hatch and Multistate W4170 programs [project numbers CA-R-ENS-5120-H and CA-R-ENS-
358
5189-RR]. S. Brander was funded by National Oceanic and Atmospheric Association grant
359
#NA17NOS9990025, Oregon Agricultural Research Foundation, and NSF Growing
360
Convergence Research grant #1935028. A. Sanchez was funded by the National Science
361
Foundation Graduate Research Fellowships Program (No. DGE 1322106) and DC Water Blue
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Plains Advanced Wastewater Treatment Plant. H. Nel received funding from The Leverhulme
363
Trust.
364
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... Raman microspectroscopy is another vibrational technique that provides information about the change of polarizability of the molecules via a sample spectrum which can be used to identify materials (Araujo et al., 2018;Ivleva et al., 2017). The use of spectroscopy in microplastics research allows researchers to confirm the material type of particles (i.e., plastic or natural), increasing the reliability of particle count estimates from environmental samples Cowger et al., 2020a;Kooi et al., 2021;Primpke et al., 2017). Using polymer confirmation, researchers can also adjust their visual microscopy counts to better reflect their true representative number (De Frond et al., 2022a). ...
... For novice labs that were using the instruments situated at SC-CWRP, specific instructions were provided on how to operate each instrument to run manual particle by particle analyses. 2.2 Data submis-sionData submission variables for this study were chosen based on the 'Microplastic Reporting Guidelines' within Cowger et al. 2020a, and further refined through discussion among the participating laboratories. Data were submitted for each suspected plastic particle counted during microscopy, and analyzed by FTIR and/or Raman, which included: sample ID, particle ID, size fraction, particle color, morphology, chemical identification result and the instrument used to carry out chemical identification. ...
... Chemosphere xxx (xxxx) 137300 sults. This is a promising outcome for using lower resolution mapping techniques which are becoming more widespread in the field (Primpke et al., 2020c;Cowger et al., 2020a). In general, laboratories that obtained high accuracy using FTIR microspectroscopy did not spend longer than 10 min per particle (Fig. S7). ...
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Fourier transform infrared (FTIR) and Raman microspectroscopy are methods applied in microplastics research to determine the chemical identity of microplastics. These techniques enable quantification of microplastic particles across various matrices. Previous work has highlighted the benefits and limitations of each method and found these to be complimentary. Within this work, metadata collected within a method validation study was used to determine which variables most influenced successful chemical identification of un-weathered microplastics in simulated drinking water samples using FTIR and Raman microspectroscopy. No variables tested had a strong correlation with the accuracy of chemical identification. The variables most correlated with accuracy differed between the two methods, and include both physical characteristics of particles (color, morphology, size, polymer type), and instrumental parameters (spectral collection mode, spectral range). Based on these results, we provide technical recommendations to improve capabilities of both methods for measuring microplastics in drinking water and highlight priorities for further research. For FTIR microspectroscopy, recommendations include considering the type of particle in question to inform sample presentation and spectral collection mode for sample analysis. Instrumental parameters should be adjusted for certain particle types when using Raman microspectroscopy. For both instruments, the study highlighted the need for harmonization of spectral reference libraries among research groups, including the use of libraries containing reference materials of both weathered plastic and natural materials that are commonly found in environmental samples.
... (2019) describe a severe lack of data, meaning that risk cannot be quantified with the current J o u r n a l P r e -p r o o f state of knowledge (Gouin et al. 2019;VKM 2019). Metadata or other quality data is often lacking in MNP research, the reasons having been described above, namely: (i) lack of harmonisation in sampling, sample processing and analysis, and (ii) inconsistent reporting of data and units (Cowger et al. 2020;Gouin et al. 2019;Koelmans et al. 2020;Provencher et al. 2020). It is unsurprising that these issues are problematic given the complexity (Koelmans et al. 2020). ...
... MNP concentration data that are not adequately supported by metadata has much lower value from an LCIA and RA perspective. MP reporting guidelines are described as important in order to help ensure no critical information is omitted (Michida et al. 2019;Cowger et al., 2020). ...
... These guidelines are recommended as a reference source when carrying out both field and laboratory MNP studies. The checklist provided by therein can guide experimental design and J o u r n a l P r e -p r o o f data recording to ensure that all related procedures are thoroughly documented (Cowger et al., 2020). The need for reporting requirements and size specifications of MNPs in seawater samples is also described in Michida et al. (2019) which form part of the G20 recommendations which were prepared with the view of enabling researchers of ocean surface layer microplastic monitoring to adopt similar monitoring protocols and therefore interpret their results with a level of comparability. ...
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Ongoing efforts focus on quantifying plastic pollution and describing and estimating the related magnitude of exposure and impacts on human and environmental health. Data gathered during such work usually follows a receptor perspective. However, Life Cycle Assessment (LCA) represents an emitter perspective. This study examines existing data gathering and reporting approaches for field and laboratory studies on micro- and nanoplastics (MNPs) exposure and effects relevant to LCA data inputs. The outcomes indicate that receptor perspective approaches do not typically provide suitable or sufficiently harmonised data. Improved design is needed in the sampling, testing and recording of results using harmonised, validated and comparable methods, with more comprehensive reporting of relevant data. We propose a three-level set of requirements for data recording and reporting to increase the potential for LCA studies and models to utilise data gathered in receptor-oriented studies. We show for which purpose such data can be used as inputs to LCA, particularly in life cycle impact assessment (LCIA) methods. Implementing these requirements will facilitate proper integration of the potential environmental impacts of plastic losses from human activity (e.g. litter) into LCA. Then, the impacts of plastic emissions can eventually be connected and compared with other environmental issues related to anthropogenic activities.
... There are no universally accepted methods for characterizing MPs or how they are monitored in the atmosphere [1]. There is an emerging guideline on how best to report MP datasets [31]. Studies to date use varied methodological approaches from passive to active sampling and reporting in different units that cannot be cross compared [9,[21][22][23][24][25][26][27] and do not relate to breathable volume units used in statutory air quality monitoring. ...
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Atmospheric microplastics (MPs) are a ubiquitous environmental contaminant of emerging concern. Sampling methods provide information relating to surface area concentration and MP characteristics, without direct comparison with routinely measured standard air quality parameters. This study analysed 6 active air samples generated by a local authority as part of their routine air quality monitoring activities. Continuous sampling totalled 10 months, within the city centre of Kingston-upon-Hull. By using μFTIR analysis, levels of total particles detected using the NOx inlet filters ranged from 5139 ± 2843 particles m−2 day−1, comprising 1029 ± 594 MPs m−2 day−1. The controls displayed a mean level of 2.00 ± 3.49 MPs. The polymers nylon (32%) and polypropylene, PP (22%) were the most abundant. Small fragments of 47.42 ± 48.57 μm (length) and 21.75 ± 13.62 μm (width) were most common. An increase in MP levels during April 2020 coincided with an increase in PM10 levels. This study used robust procedures to measure MPs in the air by exploiting existing air quality monitoring equipment. Knowing the levels, types, and characteristics of MPs can inform toxicity studies to provide more environmentally relevant exposures, which is urgent now that MPs have been reported in human lung tissue.
... However, towards a holistic understanding of microplastics pollution and environmental monitoring, microplastics data with reliable comparability is important. Thus, the need for the harmonization of methods is widely recommended in microplastics research Cowger et al., 2020;. ...
... However, comparison between studies is challenging due to differences in sampling methods, size fraction being considered, extraction methods, analysis and quality assurance/ quality control (QA/QC) protocols. In an effort to improve the comparability and reproducibility of MP studies, Cowger et al. (2020) developed a set of reporting guidelines that will be followed here. ...
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Microplastics (MPs) were characterized in surficial marine sediment (n = 36) and mussel (n = 29) samples collected along the British Columbia (BC) coast, Canada, using visual identification and Fourier Transform Infrared Spectrometry. MPs counts averaged 32.6 ± 5.3 particles per kg in sediment and 0.38 ± 0.04 particles per individual mussel (0.24 ± 0.04 /g of tissue). Victoria Harbour and the North Coast (Prince Rupert area) were MP hotspots, likely resulting from a combination of local sources and oceanographic conditions. Microfibers <1000 μm dominated the pattern in both matrices (61.1 % in sediment; 65.4 % mussels) highlighting the suspected role of textiles in the widespread distribution of MPs in the marine environment. Overall, polyester was dominant in sediment and mussels (54.1 % and 63.5 %, respectively), followed by polyethylene (16.2 % and 11.5 %, respectively). This is the first report of MPs in sediment and mussels along the coast of BC using standardized methods.
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The lack of one standardized method to evaluate microplastic pollution in different aquatic environments worldwide represent a gap to fill for the scientist's community. To help overcome this challenge, we adapted an aquatic drone, named Jellyfishbot®, to sample microplastics. The aquatic drone has been compared with the actual most used method for sampling MPs in surface waters: the Manta net. In order to test the reliability of the aquatic drone in different environments, samples were collected in a river and coastal waters sites. The results obtained with the two methods were similar in term of MPs abundances, shapes and colors. It provides also a better reproducibility and more accurate sampling of MPs located in the surface waters mainly the lighter and smaller ones. This sampling method has the advantage of combining the benefits of Manta net sampling (i.e. a representative surface water sampling method that covers a large sampling area and volume (several tens m³) with those of pump filtration and grab sampling (easy access to confined and hard-to-reach areas). This new sampling method could be applied in different aquatic environments making it possible to compare the data and hence become a new standardized approach to evaluate microplastic pollution levels.
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Study region The Santa Ana River middle reach, a small coastal urban catchment in Southern California, USA experiences a Mediterranean climate and lowflows dominated by wastewater effluent. Study focus River macroplastic flux can inform watershed management of plastic pollution. However, continuous macroplastic monitoring is not possible, so concentrations must be predicted during unobserved periods. We monitored macroplastic concentration and aimed to improve macroplastic flux estimation using strategies commonly employed in estimating mineral sediment flux. New hydrological insights for the region Floating macroplastic size distributions were statistically equivalent between lowflow and stormflow samples – evidence that channel processes controlled macroplastic size distribution or macroplastic size distributions outside the channel were the same as inside. Concentrations fell during the falling limb of one hydrograph and rose during the rising limb of another hydrograph. A generalized additive model (GAM) revealed that macroplastic concentration increased in response to small discharge increases but decreased for the largest discharges. Macroplasitc depletion (relative to discharge) occurs at high flow magnitudes or during the falling limb. The annual mass flux of floating macroplastic was 27.4 (2.8–84.8) tonnes¹yr⁻¹ or 18.2 (2.9–222.2) tonnes¹yr⁻¹ as predicted using mean concentration or the GAM, respectively. With little data, the mean concentration approach may be appropriate but likely underestimates uncertainty – which will require extensive monitoring to reduce.
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Microplastic pollution is a widespread environmental concern. Like other anthropogenic pollutants, microplastics can reach aquatic ecosystems through rivers and interact with the aquatic biota. For instance, Lake Titicaca (between Bolivia and Peru), one of the great ancient lakes in South America (3,809 m a.s.l.), shows a pollution problem, particularly in the southern shallow basin (Lago Menor) in Bolivia. Nevertheless, our knowledge of the presence of microplastics and their interaction with the biota of Lake Titicaca is limited. Therefore, this study evaluated the presence of microplastics in the stomach content of the four fish species targeted by local fisheries in Lago Menor of Lake Titicaca ( Orestias luteus, Orestias agassizii, Trichomycterus dispar, and Odonthestes bonariensis ; N = 1,283), and looked for relationships with trophic guilds or fishing areas. Additionally, surface water was analyzed to evaluate the presence of microplastics in the water. The evaluation of microplastics was carried out by visual observations. We observed that the frequency of microplastic ingestion was low in all species (<5%). Conversely, microplastic was present in the water, with the highest quantity at the southern part of Lago Menor (103 ± 20 particles per L), without differences in the microplastic number between sites. Most microplastics counted in stomach contents were fibers, whereas water samples mainly contained fragments. Our results point to microplastic pollution in Lago Menor of Lake Titicaca. However, we could not determine the pollution rate due to considerable methodological limitations. Further research will be needed to robustly detect microplastics in Lake Titicaca and their impact on the fish species in the lake.
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In the environment, synthetic polymers, commonly known as "plastics", are well-known to undergo various chemical weathering processes, which modify their surface chemistry by introducing new functional groups. Such changes are important to monitor, as they can severely influence the toxicity caused by plastic debris. Therefore, in this study, two chemometric models are proposed to accelerate the chemical classification of macro- and meso-plastics found in the environment. For this purpose, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied on preprocessed infrared spectra of 83 plastic fragments found on public lake and river beaches. HCA associated all beach samples with a known plastic, whereas PCA enabled the association of only 39.8% (33 out of 83) of the beach samples with a known plastic. However, both techniques agreed on 93.9% of the samples identified. According to PCA and HCA results, polypropylene and polyethylene were the most frequently identified polymers in the samples. PCA turned out to be a very promising tool for fast screening of weathered plastics, since the distance of samples from the polypropylene cluster in the PCA plot was correlated with weathering. This was later confirmed by employing other characterization techniques such as micro-Raman, X-ray photoelectron spectroscopy and scanning electron microscopy. Finally, future experiments should focus on the applicability of the proposed combined chemometric approach for very small microplastics (<100 μm), as they have more important effects than larger plastics on aquatic ecosystems.
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Microplastics (MP) are perceived as a threat to aquatic ecosystems but bear many similarities to suspended sediments which are often considered less harmful. It is, therefore pertinent to determine if and to what extent MPs are different from other particles occurring in aquatic ecosystems in terms of their adverse effects. We applied meta-regressions to hazard data extracted from the literature and harmonized the data to construct Species Sensitivity Distributions (SSDs) for both types of particles. The results demonstrate that the average toxicity of MPs is approximately one order of magnitude higher than that of suspended solids. However, the estimates were associated with large uncertainties and did not provide very strong evidence. In part, this is due to the general lack of comparable experimental studies and dose-dependent point estimates. We, therefore, argue that a precautionary approach should be used and MP in the 1–1000 µm size range should be considered moderately more hazardous to aquatic organisms capable of ingesting such particles. Organisms inhabiting oligotrophic habitats like coral reefs and alpine lakes, with naturally low levels of non-food particles are likely more vulnerable, and it is reasonable to assume that MP pose a relatively higher risk to aquatic life in such habitats. Synopsis A meta-analysis indicates that microplastics are one order of magnitude more toxic than suspended sediments/solids, an estimate surrounded by considerable uncertainty. Graphical abstract
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