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In recent years, microplastics have been reported in drinking water and drinking water sources, including bottled, tap, and surface water (Koelmans et al. 2019). Despite numerous studies that have reported on the presence of microplastics, little is known about the potential human health risks and long-term environmental effects that microplastics exposure may pose.

Recently, the World Health Organization (WHO) reviewed available information on microplastics in drinking water and concluded that “routine monitoring of microplastics in drinking-water is not recommended at this time, as there is no evidence to indicate a human health concern” (WHO, 2019). While the study generally found “low health concern” in the preliminary assessment of hazards several knowledge gaps and research needs were identified.

The WHO highlighted the need for researchers to develop standard methods for sampling and analysis of microplastics in drinking water and other media, for which none currently exist. Similarly, in their 2017 workshop, the US EPA recommended that “the development of reliable, reproducible and high-quality methods for microplastics quantification and characterization is fundamental and of paramount importance for understanding microplastics risks” (EPA, 2017: p. 7).

Within the U.S., California is the only State that has established legislation related to microplastics in drinking water. Senate Bill (SB) 1422 under the California Safe Drinking Water Act, requires that the California State Water Board adopt a formal definition of microplastics by July 1, 2020 (California Legislation 2018). Additionally, the Board must adopt standard testing methodology to measure microplastics in drinking water, and adopt requirements to test and report microplastics in drinking water during a four year period .While this initiative is expected to address several of the gaps in method standardization and development identified by the WHO and EPA, it will likely not directly address gaps in understanding of potential toxicity in humans.


Cardno ChemRisk scientists have extensive professional experience conducting applied research studies to address the microplastics knowledge gaps identified in the WHO report. Our team has a number of specialists who have the ability to accurately assess the potential health risks associated with microplastic exposure, and recently published a comprehensive methodology for modeling microplastic fate at a watershed scale (Unice et al. 2019a, 2019b).  If you would like to learn more about our capabilities or have any questions about this topic, please contact Ken Unice.