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

Abstract

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.

Toward an Improved Understanding of the Ingestion and Trophic Transfer of Microplastic Particles: Critical Review and Implications for Future Research

“…A key challenge, however, relates to limitations in analytical capability. Several reviews summarizing the advantages and disadvantages of the various analytical methods have been published (Hidalgo‐Ruz et al 2012; Rocha‐Santos and Duarte 2015; Lusher et al 2017; Hermsen et al 2018). There is clearly a need for standardized quantitative methods.…”

“…The literature data on ingestion of microplastic particles to include in the present review was initially based on the reference lists reported in several robust reviews recently published for organisms at all levels of biological organization (Schuyler et al 2014; Deudero and Alomar 2015; Lusher et al 2017; Poeta et al 2017; Burns and Boxall 2018; Foley et al 2018; Fossi et al 2018; Hermsen et al 2018; Battisti et al 2019; Botterell et al 2019; Triebskorn et al 2019; Wang et al 2019). The initial list was further complemented by identification of other studies, using a range of methods.…”

“…Various approaches toward analysis of the assembled dataset were used. These included an assessment of the quality of each of the field‐based studies as reported for individual species based on the quality criteria and assessment scoring system developed and applied by Hermsen et al (2018). It should be noted that data on the number of microplastic particles/individual are generally perceived as being the most relevant for understanding the ingestion and subsequent potential for ingestion and also for enabling a comparison between organisms of different genders, ages, and species.…”

“…The quality assessment method developed was based on 10 separate criteria: sampling method and strategy; sample size, processing, and storage; laboratory preparation; clean air conditions; adoption of negative and positive controls; target component; sample treatment both before and after a procedure; and polymer identification. Each criterion was assigned a score of either 0, 1, or 2, with 0 indicating that the criterion was not adequately addressed, 1 suggesting the criterion was met but with caveats, and 2 implying the criterion was adequately addressed (Hermsen et al 2018). A total assessment score (TAS) was then derived by summing the score for each of the individual criteria.…”

“…A total assessment score (TAS) was then derived by summing the score for each of the individual criteria. Although Hermsen et al (2018) provide guidance on how to score a study for each criterion, there is the potential for subjectivity in some instances, whereby assigning a 1 or a 2 may be open to interpretation. In recognition of this potential challenge, the results of the study assessments were binned to reflect more general trends in the TAS, with a TAS ≤10 implying that a study largely failed to meet the quality of the defined criteria, a TAS between 10 and 15 indicating that study results were of average quality, and a score ≥15 implying that the study had satisfactorily addressed each of the specific criteria defined.…”