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Micro- and nano-plastic particle research needs urgent improvement for effective biomonitoring and risk assessment purposes 

St. Andrews, New Brunswick, Canada – February 4, 2025

Micro- and nano-plastic particles (MNPs) in the ocean environment and our aquatic food supply is quickly becoming one of the most pressing environmental and public health issues of our time. This level of importance is also reflected in the increasing attention given by the research community and resulting large body of scientific literature over the last decade. Unfortunately, there is a general lack of adherence to accepted guidelines for how to conduct and report this research, especially to increase its value for effective biomonitoring and risk assessment purposes – using living organisms to assess the quality of the environment.

Huntsman Marine researchers, along with a colleague from ExxonMobil Biomedical Sciences Inc., completed an initial literature survey within various scientific databases for the period of 2017 - 2022, resulting in 409 applicable biomonitoring papers identified for further systematic review. Each of these were then scored using a previously published 10-category quality criteria rubric that assessed whether the publication included sufficient detail for: sampling method and strategy, sample size, sample processing and storage, laboratory preparation, clean air conditions, negative controls, positive controls, target component, sample treatment, and polymer identification.

“On the plus side, the general quality of MNP study design appears to be improving with time,” notes Dr. Benjamin de Jourdan, Huntsman Marine Research Scientist and lead author on the published results in the peer-reviewed journal Science of the Total Environment. “However, deficiencies still occur in reporting study results that affect relevance and reliability for biomonitoring purposes with more effort needed to improve the scientific body of knowledge.” 

Biomonitoring studies are essential to quantify chemical and particle exposures while also allowing comparisons across all ocean regions and track changes over time. Biomonitoring also provides a means to assess the effectiveness or limitations of various technological, regulatory or policy interventions aimed at reducing the presence of a contaminant in the environment. Researchers therefore have a responsibility to carefully design biomonitoring studies and ensure their methods are fully described within publications to ensure results are best able to aid in the decision-making process. 

There is certainly a deluge of MNP research published each year but only about 100 are published annually meeting the relevant and reliable inclusion criteria used in this critical review. Essentially all ocean regions were included but with the greatest focus nearly equal from the North Pacific Ocean, Mediterranean Sea and North Atlantic Ocean. An impressive number of 1,243 unique species were included in the 409 reviewed papers with the overwhelming majority being fish followed by crustaceans and bivalves.

The authors aimed to be completely transparent in their scoring process as part of their review. “Reviewing over 400 papers was no easy task and we made the scores for each paper available to view online,” explained de Jourdan. 

“This transparency ensures that others can see how we derived the scores and use them as a training set for future evaluations.”   Some key observations from the critical review include: 

 

  • 23% of the research units had the lowest score possible for its description of sampling methods, such as gear type, sampling location and mesh size.
     

  • 22% did not describe appropriate sample processing and storage methods following field collection.
     

  • 20% were published without any acknowledgement that measures were taken to protect against sample contamination, such as clothing protection or use of PPE, while processing within the laboratory setting.
     

  • 48% of reviewed studies did not note processing samples in clean air conditions in the laboratory (e.g., laminar flow cabinet or in a ‘clean room’ setting) to assure the high likelihood of contamination did not occur, which is an improvement from the 90% of studies failing this criteria previously.
     

  • 86% of research units did not include a positive control or perform a recovery study. Only 24 of 409 papers included this crucial step, which is unfortunately consistent with an earlier 2018 assessment of biomonitoring studies.

Scores from the initial 10 assessment criteria were applied to a two-step gateway review to determine overall reliability of each publication for biomonitoring purposes. First, each publication was assessed by giving more weight to whether specific polymers were identified “…as the core objective [of a biomonitoring study] is to develop quantitative relationships between biota and their environment.” In doing so, 108 of the 409 reviewed publications were excluded from further analysis given their limited quantitative utility for biomonitoring and risk assessments.

The remaining 301 papers were assessed against a second gate on whether a quantitative relationship between the biota and external environment (matrix) could be achieved from the data reported in the publication. Here, studies that did not include a paired environmental sample (sediment and/or water) were excluded, further reducing the number of papers to 73. Only 32 of those papers had greater than a 50% score for reliability. Just 8% of the 409 publications reviewed met the criteria for reliability, utility for biomonitoring, and informing ecological risk assessment.

These results clearly highlight the urgent need for more robust, methodologically sound studies for biomonitoring as a valuable tool but one that requires strict adherence to standardized methods and reporting. The publication finishes with a series of recommendations targeted towards journals, reviewers, funders and researchers.

de Jourdan concludes, “We are encouraged to see that the research community is consistently improving with the methods used and described within their publications related to micro-and nano-plastic biomonitoring studies. There is still considerable work to be done but we hope that our recommendations will ensure the greatest utility of research results for effective decision-making and adoption of mitigation measures.”

The biomonitoring publication review effort was funded by ExxonMobil Biomedical Sciences Inc.

Research Publication: 

de Jourdan, B., D. Philibert, D. Asnicar and C.W. Davis. 2024. Microplastic biomonitoring studies in aquatic species: A review & quality assessment framework. Science of the Total Environment 957:177541. 
https://doi.org/10.1016/j.scitotenv.2024.177541

Image 1: Graphical abstract of the critical results beginning with 409 papers and ending with just 32 studies meeting the final reliability threshold based on details presented within the published manuscripts.

Image 2: Results from the critical review for each of the 10-categories in the quality criteria rubric. 

 

Story by Bud Adams, The Huntsman Marine Science Centre.  

For additional information or images relating to this article, please email huntsman@huntsmanmarine.ca

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