Development and application of a health-based framework for informing regulatory action in relation to exposure of microplastic particles in California drinking water.
Development and application of a health-based framework for informing regulatory action in relation to exposure of microplastic particles in California drinking water.
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DOI：
10.1186/s43591-022-00030-6
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发表时间：
2022
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微塑料已经在饮用水中被记录在案，但它们通过摄取对人类健康的影响，或者这些影响开始显现的浓度，还没有确定。在这里，我们报告了在2020年10月至2021年10月期间举行的一个虚拟专家研讨会的结果，在该研讨会中，对哺乳动物危险研究进行了全面审查。这项评估的一个关键目标是评估得出以人类健康为基础的阈值的可行性和可信度，以便为加利福尼亚州饮用水中微塑料监测和管理战略的制定提供信息。采用了分级方法来评估从同行评审的科学文献审查中确定的研究的质量和可靠性。总共确定了41项体外研究和31项使用哺乳动物的体内研究，并进行了一级筛选和优先排序，这是基于对每项研究如何满足各种质量标准的评估。确定优先研究的主要依据是它们的应用和剂量-反应关系的报告。鉴于目前缺乏在体外和体内系统之间进行外推的方法，在本研讨会的背景下，只有体内口服暴露研究被确定为适合目的。12项哺乳动物毒性研究被优先排序，并由外部专家进行二级定性评估。在12项研究中，7项报告了对男性和女性生殖系统的不利影响，5项报告了对其他各种生理终点的影响。值得注意的是，大多数(83%)接受二级评估报告的研究是由于接触单一聚合物类型(聚苯乙烯球)而产生的，其大小范围为0.040至20微米。没有一项研究满足所有预期的质量标准，但就炎症和氧化应激生物标志物的毒理学影响总体而言，这是一个一致的趋势。虽然有可能得出一个保守的筛查水平，以便为监测活动提供信息，但无法外推微塑料以人体健康为基础的阈值，这主要是因为对当前数据的相对质量和可靠性的担忧，但也是因为无法外推使用单分散塑料颗粒的研究数据，例如聚苯乙烯微球接触与环境有关的微塑料。然而，保守的筛查水平值被用来估计可用于支持监测活动和提高我们对加州饮用水暴露的整体了解的饮用水的量(1000 L)。为了增加人们对我们今后得出以人类健康为基础的阈值的能力的信心，提出了几项研究建议，重点是加强今后应如何进行毒性研究，并增进对人类接触微塑料的了解，这些见解对于更好地为未来的风险评估提供信息至关重要。网上版载有补充材料，可在10.1186/s43591-022-00030-6查阅。
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. The online version contains supplementary material available at 10.1186/s43591-022-00030-6.