Cited by 78Microplastics and Plastic PollutionEnvironmental Toxicology and EcotoxicologyWater Treatment and Disinfection

Development and application of a health-based framework for informing regulatory action in relation to exposure of microplastic particles in California drinking water

Open access
Coffin, Scott, Bouwmeester, Hans, Brander, Susanne, Damdimopoulou, Pauliina, Gouin, Todd, Hermabessiere, Ludovic, Khan, Elaine, Koelmans, Albert A. +5 more·2022·Microplastics and Nanoplastics

Abstract

Microplastics have been documented in drinking water, but their effects on human health from ingestion, or the concentrations at which those effects begin to manifest, are not established. Here, we report on the outcome of a virtual expert workshop conducted between October 2020 and October 2021 in which a comprehensive review of mammalian hazard studies was conducted. A key objective of this assessment was to evaluate the feasibility and confidence in deriving a human health-based threshold value to inform development of the State of California’s monitoring and management strategy for microplastics in drinking water. A tiered approach was adopted to evaluate the quality and reliability of studies identified from a review of the peer-reviewed scientific literature. A total of 41 in vitro and 31 in vivo studies using mammals were identified and subjected to a Tier 1 screening and prioritization exercise, which was based on an evaluation of how each of the studies addressed various quality criteria. Prioritized studies were identified largely based on their application and reporting of dose–response relationships. Given that methods for extrapolating between in vitro and in vivo systems are currently lacking, only oral exposure in vivo studies were identified as fit-for-purpose within the context of this workshop. Twelve mammalian toxicity studies were prioritized and subjected to a Tier 2 qualitative evaluation by external experts. Of the 12 studies, 7 report adverse effects on male and female reproductive systems, while 5 reported effects on various other physiological endpoints. It is notable that the majority of studies (83%) subjected to Tier 2 evaluation report results from exposure to a single polymer type (polystyrene spheres), representing a size range of 0.040 to 20 µm. No single study met all desired quality criteria, but collectively toxicological effects with respect to biomarkers of inflammation and oxidative stress represented a consistent trend. While it was possible to derive a conservative screening level to inform monitoring activities, it was not possible to extrapolate a human–health-based threshold value for microplastics, which is largely due to concerns regarding the relative quality and reliability of current data, but also due to the inability to extrapolate data from studies using monodisperse plastic particles, such as polystyrene spheres to an environmentally relevant exposure of microplastics. Nevertheless, a conservative screening level value was used to estimate a volume of drinking water (1000 L) that could be used to support monitoring activities and improve our overall understanding of exposure in California’s drinking water. In order to increase confidence in our ability to derive a human–health-based threshold value in the future, several research recommendations are provided, with an emphasis towards strengthening how toxicity studies should be conducted in the future and an improved understanding of human exposure to microplastics, insights critically important to better inform future risk assessments. Graphical abstract

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Crossref · 10.1186/s43591-022-00030-6

Cites

101 of 102 references verified0 citation errors · 0 not checkable

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  • No risk assessment framework for human health currently exists for microplastics.

    “Given the many uncertainties, no risk assessment framework for human health currently exists.28”

    From Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes (2024) · cites this paper as [28]

    The Conclusion (page not available in our copy) says the authors present and test a framework for developing human-health guidance values for microplastics in drinking water. It distinguishes that framework and its non-regulatory screening level from regulatory threshold values, which uncertainties were too high to recommend. Thus the paper does not support the categorical claim that no human-health risk assessment framework exists. (LLM, conf=0.90)

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  • There is still much uncertainty regarding the mechanisms of toxicity across organisms, as well as how they vary by taxa, types of microplastics, end points, and the threshold at which effects occur.

    “There is still much uncertainty regarding the mechanisms of toxicity across organisms, as well as how they vary by taxa, types of microplastics, end points, and the threshold at which effects occur.28”

    From Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes (2024) · cites this paper as [28]

    The Implications and recommendations section identifies gaps in mechanistic understanding across endpoints and particle types. The Abstract says the evidence cannot support a human-health threshold for microplastics. The paper discusses mammalian and non-mammalian studies, but the cited passages do not establish uncertainty specifically about how toxicity mechanisms vary by taxon; its threshold finding is also specific to human health. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • A recent study suggests we do not yet know enough to assess total risk from environmental exposure, noting concerns about the quantity and quality of studies to date.

    “a recent study suggests we do not yet know enough to assess total risk from environmental exposure, noting concerns about the quantity and quality of the studies to date.28”

    From Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes (2024) · cites this paper as [28]

    The Results and discussion (Literature review and Tier 1 screening evaluation; no page supplied) identify study-quality problems and caution against predicting human-health implications from tests that poorly reflect environmental exposure. The Human-health guidance level recommendation says the data are insufficient for drinking-water advisory or regulatory levels, though adequate for a non-regulatory screening level. This supports uncertainty about risk, but the paper does not assess the broader ‘total risk from environmental exposure’ claimed here. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • Discrepancies in microplastic toxicity results are likely due to exposure experiments using different concentrations, and variations in results could be relevant to the polymer type, morphology, or size used in the study.

    “Discrepancies are likely due to exposure experiments using different concentrations, but also these variations in results could be relevant to the polymer type, morphology, or size used in the study.28”

    From Microplastics and Anthropogenic Particles in Recreationally Caught Freshwater Fish from an Urbanized Region of the North American Great Lakes (2024) · cites this paper as [28]

    The Tier 2 expert evaluation (page unavailable) says particle size and polymer composition can influence uptake and the interpretation of physiological effects; its comparison of polystyrene spheres with polyethylene fragments also bears on morphology. The paper discusses exposure concentrations and dose–response relationships, but does not establish that different concentrations are the likely cause of discrepancies between studies. It also cautions that the proposed size-based explanation for one contrasting result could not be confirmed. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • There are critical gaps in knowledge surrounding the toxicokinetics and mechanisms of toxicity for environmental mixtures of microplastics, as well as the amount of microplastics that are likely to cause an adverse effect in humans.

    “Currently, there are critical gaps in knowledge surrounding the toxicokinetics and mechanisms of toxicity for environmental mixtures of microplastics, as well as the amount of microplastics that are likely to cause an adverse effect in humans.28”

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Research works printed but not linked: 4

  1. [78]OECD. Test No. 422: Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test. OECD; 1996 [cited 2021 Nov 3]. Available from: https://www.oecd-ilibrary.org/environment/test-no-422-combined-repeated-dose-toxicity-study-with-the-reproduction-developmental-toxicity-screening-test_9789264070981-en.
  2. [79]OECD. Test No. 421: reproduction/developmental toxicity screening test. OECD Guidelines for the Testing of Chemicals, Section. 2016;4. https://www.oecd-ilibrary.org/environment/test-no-421-reproduction-developmental-toxicity-screening-test_9789264264380-en.
  3. [80]OECD. Test No. 443: Extended One-Generation Reproductive Toxicity Study. OECD; 2018 [cited 2021 Oct 1]. (OECD Guidelines for the Testing of Chemicals, Section 4). Available from: https://www.oecd-ilibrary.org/environment/test-no-443-extended-one-generation-reproductive-toxicity-study_9789264185371-en.
  4. [121]Wright SL Gouin T Koelmans AA Scheuermann L Development of screening criteria for microplastic particles in air and atmospheric deposition: critical review and applicability towards assessing human exposure Micropl&Nanopl 2021 1 1 6

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Authors
Coffin, S., Bouwmeester, H., Brander, S., Damdimopoulou, P., Gouin, T., Hermabessiere, L., Khan, E., Koelmans, A. A., Lemieux, C. L., Teerds, K., Wagner, M., Weisberg, S. B., & Wright, S.
Affiliations
  • State of California (US)
  • Wageningen University & Research (NL)
  • Oregon State University (US)
  • Karolinska University Hospital (SE)
  • Health Canada (CA)
  • Norwegian University of Science and Technology (NO)
  • Southern California Coastal Water Research Project (US)
  • Imperial College London (GB)
Corresponding author
Coffin, Scott
Venue
Microplastics and Nanoplastics
Published
2022-05-25
Volume
2
Issue
1
Pages
12-12
ISSN
2662-4966 (ISSN-L)
OpenAlex
W4281479331
Cited by
78
References
101
Citations by year
2026: 11 · 2025: 17 · 2024: 23 · 2023: 15 · 2022: 12
FWCI
3.98
Type
journal article
Language
en
Open access
Locations
  • Microplastics and Nanoplastics (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Socio-Environmental Systems Modeling (acceptedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by)
  • Data Archiving and Networked Services (DANS) (submittedVersion, cc-by)
Funders
  • California State Water Resources Control Board
  • ZonMw
  • European Commission (965196)
  • National Science Foundation
  • Environment and Climate Change Canada
  • World Health Organization
  • European Centre for Ecotoxicology and Toxicology of Chemicals
  • European Food Safety Authority
  • American Chemistry Council
  • Horizon 2020 Framework Programme
  • European Chemical Industry Council
  • Nederlandse Organisatie voor Wetenschappelijk Onderzoek
  • Norges Forskningsråd
  • Rijkswaterstaat
  • United Nations Foundation
Topics
  • Physical Sciences › Environmental Science › Pollution › Microplastics and Plastic Pollution
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Environmental Toxicology and Ecotoxicology
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Water Treatment and Disinfection
Keywords
microplastics, drinking water, regulatory action, mammalian toxicity, dose-response relationship, polystyrene microspheres, reproductive toxicity, oxidative stress, inflammatory markers, screening levels, expert workshop, exposure assessment, data quality criteria, in vitro-in vivo extrapolation, microplastic ingestion, research recommendations

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