Proceed with caution: The need to raise the publication bar for microplastics research

This is an Accepted Manuscript. Embargo until December 12 2022.Plastic is a ubiquitous contaminant of the Anthropocene. The highly diverse nature of microplastic pollution means it is not a single contaminant, but a suite of chemicals that include a range of polymers, particle sizes, colors, morphologies, and associated contaminants. Microplastics research has rapidly expanded in recent years and has led to an overwhelming consideration in the peer-reviewed literature. While there have been multiple calls for standardization and harmonization of the research methods used to study microplastics in the environment, the complexities of this emerging field have led to an exploration of many methods and tools. While different research questions require different methods, making standardization often impractical, it remains import to harmonize the outputs of these various methodologies. We argue here that in addition to harmonized methods and quality assurance practices, journals, editors and reviewers must also be more proactive in ensuring that scientific papers have clear, repeatable methods, and contribute to a constructive and factual discourse on plastic pollution. This includes carefully considering the quality of the manuscript submissions and how they fit into the larger field of research. While comparability and reproducibility is critical in all fields, we argue that this is of utmost importance in microplastics research as policy around plastic pollution is being developed in real time alongside this evolving scientific field, necessitating the need for rigorous examination of the science being published.acceptedVersio

Human Consumption of Microplastics

Microplastics are ubiquitous across ecosystems, yet the exposure risk to humans is unresolved. Focusing on the American diet, we evaluated the number of microplastic particles in commonly consumed foods in relation to their recommended daily intake. The potential for microplastic inhalation and how the source of drinking water may affect microplastic consumption were also explored. Our analysis used 402 data points from 26 studies, which represents over 3600 processed samples. Evaluating approximately 15% of Americans’ caloric intake, we estimate that annual microplastics consumption ranges from 39000 to 52000 particles depending on age and sex. These estimates increase to 74000 and 121000 when inhalation is considered. Additionally, individuals who meet their recommended water intake through only bottled sources may be ingesting an additional 90000 microplastics annually, compared to 4000 microplastics for those who consume only tap water. These estimates are subject to large amounts of variation; however, given methodological and data limitations, these values are likely underestimates

Commentary on: Abundance and distribution of microplastics within surface sediments of a key shellfish growing region of Canada.

This formal comment is in response to "Abundance and distribution of microplastics within surface sediments of a key shellfish growing region of Canada" written by Kazmiruk and colleagues in 2018. This article presents microplastics concentrations in sediment, primarily microbeads, within Baynes Sound, British Columbia, which are some of the highest that have been reported anywhere in the world. The authors cite the local shellfish industry as the likely source of this high degree of contamination and present the industry as a substantial risk to the environment. However, the authors do not sufficiently justify the efficacy of their methodology, and there are several flaws which call into question the legitimacy of their findings. In this commentary, we address the microplastic abundances reported by the authors, and methodological concerns. Furthermore, we provide additional data to elucidate some of this study's more contentious findings. Specifically, we seek to clarify the visual identification of microbeads and microfibres, and the microplastic concentration within shellfish populations, water, and sediment, within the Baynes Sound shellfish growing region

Proceed with Caution: the Need to Raise the Publication Bar for Microplastics Research.

Plastic is a ubiquitous contaminant of the Anthropocene. The highly diverse nature of microplastic pollution means it is not a single contaminant, but a suite of chemicals that include a range of polymers, particle sizes, colors, morphologies, and associated contaminants. Microplastics research has rapidly expanded in recent years and has led to an overwhelming consideration in the peer-reviewed literature. While there have been multiple calls for standardization and harmonization of the research methods used to study microplastics in the environment, the complexities of this emerging field have led to an exploration of many methods and tools. While different research questions require different methods, making standardization often impractical, it remains import to harmonize the outputs of these various methodologies. We argue here that in addition to harmonized methods and quality assurance practices, journals, editors and reviewers must also be more proactive in ensuring that scientific papers have clear, repeatable methods, and contribute to a constructive and factual discourse on plastic pollution. This includes carefully considering the quality of the manuscript submissions and how they fit into the larger field of research. While comparability and reproducibility is critical in all fields, we argue that this is of utmost importance in microplastics research as policy around plastic pollution is being developed in real time alongside this evolving scientific field, necessitating the need for rigorous examination of the science being published

Same data, different analysts: variation in effect sizes due to analytical decisions in ecology and evolutionary biology

Gould E, Fraser H, Parker T, et al. Same data, different analysts: variation in effect sizes due to analytical decisions in ecology and evolutionary biology. 2023.Although variation in effect sizes and predicted values among studies of similar phenomena is inevitable, such variation far exceeds what might be produced by sampling error alone. One possible explanation for variation among results is differences among researchers in the decisions they make regarding statistical analyses. A growing array of studies has explored this analytical variability in different (mostly social science) fields, and has found substantial variability among results, despite analysts having the same data and research question. We implemented an analogous study in ecology and evolutionary biology, fields in which there have been no empirical exploration of the variation in effect sizes or model predictions generated by the analytical decisions of different researchers. We used two unpublished datasets, one from evolutionary ecology (blue tit, Cyanistes caeruleus, to compare sibling number and nestling growth) and one from conservation ecology (Eucalyptus, to compare grass cover and tree seedling recruitment), and the project leaders recruited 174 analyst teams, comprising 246 analysts, to investigate the answers to prespecified research questions. Analyses conducted by these teams yielded 141 usable effects for the blue tit dataset, and 85 usable effects for the Eucalyptus dataset. We found substantial heterogeneity among results for both datasets, although the patterns of variation differed between them. For the blue tit analyses, the average effect was convincingly negative, with less growth for nestlings living with more siblings, but there was near continuous variation in effect size from large negative effects to effects near zero, and even effects crossing the traditional threshold of statistical significance in the opposite direction. In contrast, the average relationship between grass cover and Eucalyptus seedling number was only slightly negative and not convincingly different from zero, and most effects ranged from weakly negative to weakly positive, with about a third of effects crossing the traditional threshold of significance in one direction or the other. However, there were also several striking outliers in the Eucalyptus dataset, with effects far from zero. For both datasets, we found substantial variation in the variable selection and random effects structures among analyses, as well as in the ratings of the analytical methods by peer reviewers, but we found no strong relationship between any of these and deviation from the meta-analytic mean. In other words, analyses with results that were far from the mean were no more or less likely to have dissimilar variable sets, use random effects in their models, or receive poor peer reviews than those analyses that found results that were close to the mean. The existence of substantial variability among analysis outcomes raises important questions about how ecologists and evolutionary biologists should interpret published results, and how they should conduct analyses in the future