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Representative graphic generated using the Species Sensitivity Distribution tool. Data have been filtered to include “Particle Only” type data which passed “Red Criteria” during study screens. Data have also been aligned to the ecologically effect metric (ERM) of volume
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Throughout the past decade, many studies have reported adverse effects in biota following microplastic exposure. Yet, the field is still emerging as the current understanding of microplastic toxicity is limited. At the same time, recent legislative mandates have required environmental regulators to devise strategies to mitigate microplastic polluti...
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... Open access to satellite imagery (https://www.sentinel-hub.com/), analytical tools for plastic identification (Primpke et al., 2020;Cowger et al., 2021), and toxicity assessments (Thornton Hampton et al., 2022) all contribute to making research more accessible, thus further enabling the participation of a wider array of ocean plastic stakeholders. ...
This paper aims to guide the stakeholder engagement process related to plastic pollution research in marine environments. We draw on advice identified during an online workshop (Ocean Plastic Workshop 2022) organized by Early Career Ocean Professionals (ECOPs) from 11 countries, held in April 2022. International experts and workshop participants discussed their experiences in the collaborative development and implementation of ocean plastic pollution projects held worldwide, guided by three main questions: (i) What is the role of scientists in a multi-stakeholder project? (ii) How should scientists communicate with other stakeholders? (iii) Which stakeholders are missing in collaborative projects, and why are they missing? This multidisciplinary, co-learning approach highlights the value of stakeholder engagement for ocean plastic projects with an end goal to identify and implement ocean plastic solutions via innovative technologies, informing policy, community engagement, or a combination of all three approaches. The target outcomes of the workshop described in this paper include the identification of transdisciplinary (academic-stakeholder) engagement frameworks and specific suggestions that can serve as guidelines for the development of future plastic pollution projects.
... Over 220 toxicity studies were mined for more than 70 unique variables relating to experimental design, test organisms, biological effects, and particle characteristics of MPs used. 31 Each study was then screened by two independent reviewers based on quality criteria developed by de Ruijter et al. ...
... All reported exposure metrics were obtained from studies, and when unreported, were estimated using reported characteristics and geometric calculations. 31 Exploratory data analysis and modelling using binomial logistic regressions revealed insights into particle traits inuential for various pathways of toxicity for MPsdemonstrating that while surface area and volume are signicant predictors of toxicity (p values = 0.0012 and 0.038, respectively), studies should report (at minimum) particle count and mass (even though neither exposure metrics were statistically signicant predictors of toxicity). 32 The toxicity databases, tools to estimate particle characteristics, align toxicity studies, screen studies for quality criteria, and more were made freely available in an open-source and open-data repository utilizing an Rshiny web application called the Toxicity of Microplastics Explorer ("ToMEx") (https:// github.com/SCCWRP/aq_mp_tox_shiny). ...
... 32 The toxicity databases, tools to estimate particle characteristics, align toxicity studies, screen studies for quality criteria, and more were made freely available in an open-source and open-data repository utilizing an Rshiny web application called the Toxicity of Microplastics Explorer ("ToMEx") (https:// github.com/SCCWRP/aq_mp_tox_shiny). 31 Additionally, ToMEx allows users to upload additional published toxicity datatherefore enabling rapid and real-time meta-analyses and assessments of risk and reducing burdens of future assessments. 31 To inform California's management of MPs in aquatic ecosystems, the health effects workshop devised a framework that includes four risk-based threshold tiers each with increasing levels of critical actions recommended to be undertaken by the appropriate regulatory bodies, ranging from low Table 1 Overview of strengths and weaknesses of analytical methods used for monitoring MPs from an inter-laboratory validation study (n = 22 laboratories) reported in ref. 21. ...
Despite decades of research detailing widespread contamination and potential risks of microplastics (synthetic particles <5 mm) to humans and ecosystems by the scientific community, government agencies have made little progress to address the emerging contaminant class. Research on microplastics has increased exponentially in recent years, however translation of studies and data into knowledge that's useful for management requires clear communication between the scientific and management communities. Legislative mandates to address microplastics in drinking water and aquatic ecosystems in California prompted rapid development of fundamental tools and methods for identifying and assessing risks, including a legal definition, analytical monitoring methods, and risk assessment frameworks. While this scientific progress provides a baseline foundation for developing regulations for microplastics in California and other jurisdictions, additional research is needed to reduce uncertainties and overcome logistical barriers that are preventing the full emergence of microplastics as a regulated contaminant suite. This paper provides critical insights from both scientific and regulatory perspectives regarding recent advances in the field and recommends a path forward to overcome barriers.
... Microplastic particles (MP, <5 mm) are the most numerically abundant form of solid waste on Earth (Eriksen et al., 2014). Over the past fifteen years, the scientific community has studied this global concern by evaluating environmental concentrations in different marine compartments (Eriksen et al., 2014;Cózar et al., 2014;Woodall et al., 2014;van Sebille et al., 2015), as well as the adverse effects on aquatic organisms in laboratory conditions (reviewed in Thornton Hampton et al., 2022). Historically, the vast majority of laboratory experiments used a single polymer type, in pieces of spherical shape (i.e. ...
The impact of microplastics (MP) has attracted much attention from the scientific community and many laboratory assessments have been made of their effects on aquatic organisms. To produce MP from real environmental plastic waste, which would enable more realistic experiments, we used plastic pearl farming equipment from French Polynesian lagoons. Here, the pearl oyster Pinctada margaritifera could encounter MP coming from their breakdown in its surrounding environment. We tested an established method based on mechanical cryogenic grinding and liquid sieving. Our desired size range was 20–60 μm, corresponding to the optimal particle size ingested by P. margaritifera. The protocol was effective, generating MP particles of 20–60 μm (∼17,000–28,000 MP μg⁻¹), but also produced too many smaller particles. The peak in the desired size range was thus flattened by the many small particles <3 μm (∼82,000–333,000 MP μg⁻¹; 53–70% of total analysed particles), visible at the limit of Coulter counter analysis (cut-off point: 2 μm). Laser diffraction analysis (cut-off point: 0.4 μm) provided greater detail, showing that ∼80–90% of the total analysed particles were <1 μm. Diverging particle size distributions between those expected based on sieving range and those really observed, highlight the need to perform fine-scaled particle size distribution analyses to avoid underestimating the number of small micro- and nanoplastics (MNP) and to obtain an exact estimation of the fractions produced. Size and microstructure characterization by scanning electron microscopy suggested spontaneous particle self-assembly into crystal superstructures, which is the supposed cause of the divergence we observed. Overall, our results emphasize that particle self-assembly is a technical hurdle requiring further work and highlight the specific need to finely characterize the size distribution of MNP used in ecotoxicological experiments to avoid overestimating effects.
... The Toxicity of Microplastics Explorer: Aquatic Animals (ToMEx Database) is a free, international database that enables users to search and visualise microplastics toxicity data to aquatic organisms (Thornton Hampton et al., 2022). A version of ToMEx also exists to catalogue the effects of microplastics to human health, but this lies outside the scope of this project (see section 2.1.2). ...
This report communicates the results of social research conducted with water quality stakeholders and end users to identify water pollution priorities and research needs. This study was funded by the National Environmental Science Program (NESP) Marine & Coastal Hub.
... The database is also accompanied by a web-based application which allows users to intuitively search the database, create custom graphics, and analyze data. For more details see [23]. Our analyses used data as it is, without quality screening. ...
There is definitive evidence that microplastics, defined as plastic particles less than 5 mm in size, are ubiquitous in the environment and can cause harm to aquatic organisms. These findings have prompted legislators and environmental regulators to seek out strategies for managing risk. However, microplastics are also an incredibly diverse contaminant suite, comprising a complex mixture of physical and chemical characteristics (e.g., sizes, morphologies, polymer types, chemical additives, sorbed chemicals, and impurities), making it challenging to identify which particle characteristics might influence the associated hazards to aquatic life. In addition, there is a lack of consensus on how microplastic concentrations should be reported. This not only makes it difficult to compare concentrations across studies, but it also begs the question as to which concentration metric may be most informative for hazard characterization. Thus, an international panel of experts was convened to identify 1) which concentration metrics (e.g., mass or count per unit of volume or mass) are most informative for the development of health-based thresholds and risk assessment and 2) which microplastic characteristics best inform toxicological concerns. Based on existing knowledge, it is recommended that microplastic concentrations in toxicity tests are calculated from both mass and count at minimum, though ideally researchers should report additional metrics, such as volume and surface area, which may be more informative for specific toxicity mechanisms. Regarding particle characteristics, there is sufficient evidence to conclude that particle size is a critical determinant of toxicological outcomes, particularly for the mechanisms of food dilution and tissue translocation .
... In addition, there is also a need for studies in which organisms are exposed to combinations of microplastics as close as possible to what they would be exposed to in the ambient environment. For instance, fibers and spheres respectively make up 52-73% and 1-3% of anthropogenic particles detected in the environmental water samples [7,17,142], but roughly only 7% of studies published through 2020 use fibers whereas 62% use spheres [50]. Similarly, 82% of studies are conducted with polystyrene or polyethylene polymers, which make up only 5-28% of what is reported in the aquatic environment [17]. ...
... Similarly, 82% of studies are conducted with polystyrene or polyethylene polymers, which make up only 5-28% of what is reported in the aquatic environment [17]. Only 12% of aquatic organism tests used weathered particles [50], which are likely to present greater risks to biota due to increased ingestion probability, leachates, biofilm formation, particle roughness, increased surface area, and potentially other mechanisms [51,66,83]. ...
... For studies focused on the potential human health impacts of microplastics, similar biases regarding particle selection were observed as 77% of the rodent in vivo studies used polystyrene spheres [50]. In addition, microplastic particles were often limited to a single size (69% of studies), and no studies used weathered particles. ...
To assess the potential risk of microplastic exposure to humans and aquatic ecosystems, reliable toxicity data is needed. This includes a more complete foundational understanding of microplastic toxicity and better characterization of the hazards they may present. To expand this understanding, an international group of experts was convened in 2020–2021 to identify critical thresholds at which microplastics found in drinking and ambient waters present a health risk to humans and aquatic organisms. However, their findings were limited by notable data gaps in the literature. Here, we identify those shortcomings and describe four categories of research recommendations needed to address them: 1) adequate particle characterization and selection for toxicity testing; 2) appropriate experimental study designs that allow for the derivation of dose-response curves; 3) establishment of adverse outcome pathways for microplastics; and 4) a clearer understanding of microplastic exposure, particularly for human health. By addressing these four data gaps, researchers will gain a better understanding of the key drivers of microplastic toxicity and the concentrations at which adverse effects may occur, allowing a better understanding of the potential risk that microplastics exposure might pose to human and aquatic ecosystems.
... Effect-concentration data were collected using the Toxicity of Microplastics Explorer (ToMEx) database, built to gather peer-reviewed literature on the biological effects of different shapes and polymer types of MPs ranging between 0.001-5000 μm (Hampton et al. A, [23]). Due to uncertainties in environmental distributions for MPs smaller than 1 μm, only toxicity data between 1 and 5000 μm were included in our analysis. ...
Microplastic particles (MPs) are ubiquitous across a wide range of aquatic habitats but determining an appropriate level of risk management is hindered by a poor understanding of environmental risk. Here, we introduce a risk management framework for aquatic ecosystems that identifies four critical management thresholds, ranging from low regulatory concern to the highest level of concern where pollution control measures could be introduced to mitigate environmental emissions. The four thresholds were derived using a species sensitivity distribution (SSD) approach and the best available data from the peer-reviewed literature. This included a total of 290 data points extracted from 21 peer-reviewed microplastic toxicity studies meeting a minimal set of pre-defined quality criteria. The meta-analysis resulted in the development of critical thresholds for two effects mechanisms: food dilution with thresholds ranging from ~ 0.5 to 35 particles/L, and tissue translocation with thresholds ranging from ~ 60 to 4100 particles/L. This project was completed within an expert working group, which assigned high confidence to the management framework and associated analytical approach for developing thresholds, and very low to high confidence in the numerical thresholds. Consequently, several research recommendations are presented, which would strengthen confidence in quantifying threshold values for use in risk assessment and management. These recommendations include a need for high quality toxicity tests, and for an improved understanding of the mechanisms of action to better establish links to ecologically relevant adverse effects.
... Ideally, threshold values would be applied across a management framework whereby certain risk values would trigger specific management actions -e.g., monitoring, source-control, recreational fishing guidelines, etc. (see [8]). These thresholds could be guided by metaanalyses of the existing literature [22], or future toxicity tests designed to better answer these questions relevant to how the multidimensionality informs risk. An example of how this may look is in Fig. 2, but should be adapted by managers based on the best available science. ...
The global ubiquity and demonstrated toxicity of microplastics has led governments around the world to express the need for a risk assessment on microplastics. To conduct a risk assessment, scientists often draw upon frameworks from other contaminants, however we argue that microplastics are a unique pollutant and thus require a unique framework. Microplastics are a multidimensional contaminant, differing in size, shape, polymer type, and chemical cocktail. Each of these dimensions may influence the toxicity of the particle. Furthermore, microplastic pollution exists as a complex and dynamic mixture of particles, that varies over temporal and spatial scales. Thus, we propose a multidimensional risk framework for microplastics that incorporates, rather than simplifies, the multidimensionality of the contaminant as well as the contaminant mixture. With this framework, we can calculate a particle-specific hazard value that describes the potential for a single particle to cause harm based on its chemical and physical properties. The particle-specific hazard values can then be combined based on the number and type of particles in an environmental sample to inform the overall hazard value of the sample. The risk of the sample can then be calculated, which is dependent on the overall hazard value and the concentration of particles in the sample. Risk values among samples in the environment can be compared to illustrate differences among locations or seasons, or can be placed in a management framework with thresholds to guide regulatory decisions. To demonstrate the utility of our proposed framework, we perform a case study using data from San Francisco Bay. Our proposed framework is just that, and requires new research for application. To strengthen the ability of this framework to accurately predict risk, we propose a testing scheme that prioritizes strategic experimental designs that will increase our understanding of how each dimension of microplastics affect the toxicity (or hazard value) of a particle.
In recent years, the number of publications on nano-and microplastic particles (NMPs) effects on freshwater organisms has increased rapidly. Freshwater crustaceans of the genus Daphnia are widely used in ecotoxicological research as model organisms for assessing the impact of NMPs. However, the diversity of experimental designs in these studies makes conclusions about the general impact of NMPs on Daphnia challenging. To approach this, we systematically reviewed the literature on NMP effects on Daphnia and summarized the diversity of test organisms, experimental conditions, NMP properties and measured endpoints to identify gaps in our knowledge of NMP effects on Daphnia. We use a meta-analysis on mortality and immobilization rates extracted from the compiled literature to illustrate how NMP properties and study parameters can impact outcomes in toxicity bioassays. In addition, we investigate the extent to which the available data can be used to predict the toxicity of untested NMPs based on the extracted parameters. Based on our results, we argue that focusing on a more diverse set of NMP properties combined with a more detailed characterization of the particles in future studies will help to fill current research gaps, improve predictive models and allow the identification of NMP properties linked to toxicity.
Highlights
Systematic review of NMP effects on the model system Daphnia
Organismic, experimental and NMP properties influence observed effects
In silico identification of traits likely linked to NMP toxicity (immobilization)
More detailed standardized characterization of NMP needed to improve predictions
Microplastics (MPs) are one of the most widespread contaminants worldwide, yet their risks for freshwater ecosystems have seldom been investigated. In this study, we performed a large monitoring campaign to assess the presence and risks of MPs in Amazonian freshwater ecosystems. We investigated MP pollution in 40 samples collected along 1500 km in the Brazilian Amazon, including the Amazon River, three major tributaries, and several streams next to the most important urban areas. MPs in the 55-5000 µm size range were characterized (size, shape, color) by microscopy and identified (polymer composition) by infrared spectroscopy. Ecotoxicological risks were assessed using chronic Species Sensitivity Distributions for effects triggered by food dilution and tissue translocation using data alignment methods that correct for polydispersity of environmental MPs and bioaccessibility. This study shows that MPs are ubiquitous contaminants in Amazonian freshwater ecosystems, with measured concentrations (55-5000 µm) ranging between 5 and 152 MPs/m3 in the Amazon River and its main tributaries, and between 23 and 74,550 MPs/m3 in urban streams. The calculated Hazardous Concentration for the 5% of species (HC5) derived from the SSDs for the entire MP range (1-5000 µm) were 1.6 × 107 MPs/m3 (95% CI: 1.2 × 106 - 4.0 × 108) for food dilution, and 1.8 × 107 MPs/m3 (95% CI: 1.5 × 106 - 4.3 × 108) for translocation. Rescaled exposure concentrations (1-5000 µm) in the Amazon River and tributaries ranged between 6.0 × 103 and 1.8 × 105 MPs/m3, and were significantly lower than the calculated HC5 values. Rescaled concentrations in urban streams ranged between 1.7 × 105 and 5.7 × 108 MPs/m3, and exceeded both calculated HC5 values in 20% of the locations. This study shows that ecological impacts by MP contamination are not likely to happen in the Amazon River and its major tributaries. However, risks for freshwater organisms may be expected in near densely populated areas, such as the cities of Manaus or Belem, which have limited wastewater treatment facilities.
