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Participants Call for Next Round of Microplastics Proficiency Testing

Published on
October 27, 2025

On 7 May 2025, NIVA, VU and WEPAL-QUASIMEME hosted a webinar to present and discuss the results of the WEPAL-QUASIMEME/NORMAN Interlaboratory Study (ILS) on the Analysis of Microplastics in Environmental Matrices – ROUND 2024-DE 17. As part of the session, participants shared their views on future ILS rounds through six Mentimeter questions. In total, 38 attendees contributed their input.

Key outcomes

  • Proficiency testing remains essential: 35 of 36 respondents agreed that ILS rounds for microplastic (MP) analysis are still needed. One participant suggested monitoring would be a more efficient approach.
  • Preferred matrices: Most respondents supported including water (n=31), followed by sediment (n=24) and sand (n=12). A smaller group (n=9) also expressed interest in including biota.
  • Separate tests for different methods: 27 of 37 participants recommended separate proficiency tests for particle counting and mass determination methods, due to the differing sample requirements.
  • Particle size preferences: Most participants supported focusing on 20–500 µm, though many also called for smaller sizes (<20 µm, n=14) and larger particles (>1000 µm, n=18) to be included.
  • Additional suggestions: Requests included testing smaller particles, more polymer types and shapes, better statistical insights per method, and workshops to work towards unified, validated approaches.

    Conclusion

    Participants clearly supported organizing a next ILS round on MP analyses. The recommendations point to:

    • Separate rounds for counting and mass determination methods.
    • Inclusion of at least water, and preferably also sediment.
    • A focus on particles between 20–1000 µm, while also considering smaller fractions.