Constraints and Priorities for Conducting Experimental Exposures of Marine Organisms to Microplastics

Marine plastic pollution is a major environmental issue. Given their ubiquitous nature and small dimensions, ingestion of microplastic (MP) and nanoplastic (NP) particles and their subsequent impact on marine life are a growing concern worldwide. Transfers along the trophic chain, including possible translocation, for which the hazards are less understood, are also a major preoccupation. Effects of MP ingestion have been studied on animals through laboratory exposure, showing impacts on feeding activity, reserve depletion and inflammatory responses, with consequences for fitness, notably reproduction. However, most experimental studies have used doses of manufactured virgin microspheres that may not be environmentally realistic. As for most ecotoxicological issues, the environmental relevance of laboratory exposure experiments has recently been debated. Here we review constraints and priorities for conducting experimental exposures of marine wildlife to microplastics based on the literature, feedback from peer reviewers and knowledge gained from our experience. Priorities are suggested taking into account the complexity of microplastics in terms of (i) aggregation status, surface properties and interactions with organic and inorganic materials, (ii) diversity of encountered particles types and concentrations, (iii) particle bioavailability and distribution in experimental tanks to achieve reproducibility and repeatability in estimating effects, and (iv) strict experimental procedures to verify the existence of genuine translocation. Relevant integrative approaches encompass a wide spectrum of methods from -omics to ecophysiological approaches, including modeling, are discussed to provide novel insights on the impacts of MP/NP on marine ecosystems from a long-term perspective. Knowledge obtained in this way would inform stakeholders in such a way as to help them mitigate impacts of the micro- and nano-plastic legacy.

Ika Paul-Pont, Kevin Tallec, Carmen Gonzalez-Fernandez and al., Front. Mar. Sci., 18 July 2018

The article


Marine microplastic: Preparation of relevant test materials for laboratory assessment of ecosystem impacts


Beached macroplastic litter was collected for impact assessment studies.

Cryogenic milling provided homogenous microplastic mixture.

Common inorganic additives used as colorants, fillers and stabilisers were detected.

GC-MS identified organic plasticisers, stabilisers, antioxidants and flame retardants.

Susanne Kühn, Albert van Oyen, Andy M. Booth and al., Chemosphere, Volume 213, December 2018, Pages 103-113

The article

Quality Criteria for the Analysis of Microplastic in Biota Samples: A Critical Review

Data on ingestion of microplastics by marine biota are quintessential for monitoring and risk assessment of microplastics in the environment. Current studies, however, portray a wide spread in results on the occurrence of microplastic ingestion, highlighting a lack of comparability of results, which might be attributed to a lack of standardization of methods. We critically review and evaluate recent microplastic ingestion studies in aquatic biota, propose a quality assessment method for such studies, and apply the assessment method to the reviewed studies. The quality assessment method uses ten criteria: sampling method and strategy, sample size, sample processing and storage, laboratory preparation, clean air conditions, negative controls, positive controls, target component, sample (pre)treatment, and polymer identification. The results of this quality assessment show a dire need for stricter quality assurance in microplastic ingestion studies. On average, studies score 8.0 out of 20 points for “completeness of information” and 0 for “reliability”. Alongside the assessment method, a standardized protocol for detecting microplastic in biota samples incorporating these criteria is provided.

Enya Hermsen, Svenja M. Mintenig, Ellen Besseling, and Albert A. Koelmans, Environ. Sci. Technol., Article ASAP, August 23, 2018

The article

Novel methodology to isolate microplastics from vegetal-rich samples

Microplastics are small plastic particles, globally distributed throughout the oceans. To properly study them, all the methodologies for their sampling, extraction, and measurement should be standardized. For heterogeneous samples containing sediments, animal tissues and zooplankton, several procedures have been described. However, definitive methodologies for samples, rich in algae and plant material, have not yet been developed. The aim of this study was to find the best extraction protocol for vegetal-rich samples by comparing the efficacies of five previously described digestion methods, and a novel density separation method. A protocol using 96% ethanol for density separation was better than the five digestion methods tested, even better than using H2O2 digestion. As it was the most efficient, simple, safe and inexpensive method for isolating microplastics from vegetal rich samples, we recommend it as a standard separation method.

Alicia Herrera, Paloma Garrido-Amador, Ico Martínez and al., Marine Pollution Bulletin, Volume 129, Issue 1, April 2018, Pages 61–69

The article

NORMAN interlaboratory study (ILS) on passive sampling of emerging pollutants

A chemical monitoring on site (CM Onsite) organised by NORMAN Association and JRC in support of the Water Framework Directive

Passive samplers can play a valuable role in monitoring water quality within a legislative framework such as the European Union’s Water Framework Directive (WFD). The time-integrated data from these devices can be used to complement chemical monitoring of priority and emerging contaminants which are difficult to analyse by spot or bottle sampling methods, and to improve risk assessment of chemical pollution. In order to increase the acceptance of passive sampling technology amongst end users and to gain further information about the robustness of the calibration and analytical steps, several inter-laboratory field studies have recently been performed in Europe. Such trials are essential to further validate this sampling method and to increase the confidence of the technological approach for end users. An inter-laboratory study on the use of passive samplers for the monitoring of emerging pollutants was organised in 2011 by the NORMAN association (Network of reference laboratories for monitoring emerging environmental pollutants; together with the European DG Joint Research Centre to support the Common Implementation Strategy of the WFD. Thirty academic, commercial and regulatory laboratories participated in the passive sampler comparison exercise and each was allowed to select their own sampler design. All the different devices were exposed at a single sampling site to treated waste water from a large municipal treatment plant. In addition, the organisers deployed in parallel for each target analyte class multiple samplers of a single type which were subsequently distributed to the participants for analysis. This allowed an evaluation of the contribution of the different analytical laboratory procedures to the data variability. The results obtained allow an evaluation of the potential of different passive sampling methods for monitoring selected emerging organic contaminants (pharmaceuticals, polar pesticides, steroid hormones, fluorinated surfactants, triclosan, bisphenol A and brominated flame retardants). In most cases, between laboratory variation of results from passive samplers was roughly a factor 5 larger than within laboratory variability. Similar results obtained for different passive samplers analysed by individual laboratories and also low within laboratory variability of sampler analysis indicate that the passive sampling process is causing less variability than the analysis. This points at difficulties that laboratories experienced with analysis in complex environmental matrices. Where a direct comparison was possible (not in case of brominated flame retardants) analysis of composite water samples provided results that were within the concentration range obtained by passive samplers. However, in the future a significant improvement of the overall precision of passive sampling is needed. The results will be used to inform EU Member States about the potential application of passive sampling methods for monitoring organic chemicals within the framework of the WFD. (2016)

The report

Fast identification of microplastics in complex environmental samples by a thermal degradation method

In order to determine the relevance of microplastic particles in various environmental media, comprehensive investigations are needed. However, no analytical method exists for fast identification and quantification. At present, optical spectroscopy methods like IR and RAMAN imaging are used. Due to their time consuming procedures and uncertain extrapolation, reliable monitoring is difficult. For analyzing polymers Py-GC-MS is a standard method. However, due to a limited sample amount of about 0.5 mg it is not suited for analysis of complex sample mixtures like environmental samples. Therefore, we developed a new thermoanalytical method as a first step for identifying microplastics in environmental samples. A sample amount of about 20 mg, which assures the homogeneity of the sample, is subjected to complete thermal decomposition. The specific degradation products of the respective polymer are adsorbed on a solid-phase adsorber and subsequently analyzed by thermal desorption gas chromatography mass spectrometry. For certain identification, the specific degradation products for the respective polymer were selected first. Afterwards real environmental samples from the aquatic (three different rivers) and the terrestrial (bio gas plant) systems were screened for microplastics. Mainly polypropylene (PP), polyethylene (PE) and polystyrene (PS) were identified for the samples from the bio gas plant and PE and PS from the rivers. However, this was only the first step and quantification measurements will follow.

Erik Dümichen, , Paul Eisentraut, Claus Gerhard Bannick and al., Chemosphere, Volume 174, May 2017, Pages 572–584

The article

Detection of phthalate esters in seawater by stir bar sorptive extraction and gas chromatography–mass spectrometry

We developed the stir bar sorptive extraction (SBSE)–gas chromatography–mass spectrometry (GC–MS) method to detect 15 kinds of PAEs in seawater. The stir bars (20 mm in length and 1 mm in film thickness) coated with 150 μL of polydimethylsiloxane (PDMS) were found to demonstrate the optimal extraction of PAEs. The optimal conditions were as follows: extraction time of 2 h, extraction temperature of 25 °C, sodium chloride of 5%, methanol of 10%, analytical time of 50 min, and methanol–acetonitrile (4:1) as the solvent. SBSE–GC–MS revealed that under the set temperature, the chromatographic peaks of all 15 PAEs can appear with complete separation. The detection limit ranged from 0.07 μg/L to 5.71 μg/L, whereas the limit of quantification ranged from 0.023 μg/L to 193 μg/L, and the correlation coefficients between the chromatographic peak area and concentration of the PAEs were greater than 0.92.

Qingqing Si, Fengmin Li, Chenchen Gao, Cong Wang, Zhenyu Wang, Jian Zhao, Marine Pollution Bulletin, Volume 108, Issues 1–2, 15 July 2016, Pages 163–170

The article