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  • Writer's pictureKyle Tianshi

The California Water Board’s Legislative Response to Microplastic Contamination

Updated: Apr 17, 2023

Microplastics are commonly defined as any plastic fragment less than 5 mm in length. They originate from numerous sources: they’re created from the degradation of larger plastics into smaller pieces, from the dispersal of synthetic fibers from certain types of fabrics, and from the manufacturing of microbeads in beauty products. [1] In recent years, microplastics have become an increasingly pervasive problem. They have been found in over 90% of tap and bottled water samples, [2] and humans are estimated to consume up to 50,000 microplastics every year. [3]


Despite such a widespread presence of microplastics in the environment, the health impacts of these particles have yet to be determined, although current research indicates that they are likely to be deleterious. Microplastics have been found to absorb hazardous substances like heavy metals, persistent organic pollutants (POPs), polybrominated diphenyl ethers (PBDEs), and more. They also may accumulate in narrow passages in the human body, resulting in blockages, inflammation, and other adverse health effects.


With the risks that microplastics pose to the environment and to human health, California lawmakers have taken several preliminary steps toward solving the problem. After banning the production of microbeads, California passed Senate Bill 1422 in 2018, requiring the State Water Resources Control Board to adopt a definition of microplastics by July 2020 and develop a standard methodology for the detection of microplastics in drinking water by July 2021. [3]


In November 2021, the State Water Board published The Microplastics in Drinking Water Policy Handbook, which details the progress that has been made after the passing of Senate Bill 1422. The document defines “nanoplastics” as any particle between 1 nm and 100 µm and “large microplastics” as any particle between 100 µm and 2.5 cm. The Board establishes two primary methods for the detection of microplastics: Raman spectroscopy and infrared spectroscopy. Both these techniques use similar approaches to identify plastics. In Raman spectroscopy, high-intensity light is used to excite the molecules within individual particles. The Raman scattered light that is returned can be used to analyze the particle’s chemical composition. In infrared spectroscopy, a machine measures the vibration of molecules through infrared light.


While both these methods are effective at accurately identifying microplastics, spectroscopy still has some distinct disadvantages. The procedure uses highly complex and expensive devices that require trained personnel to operate, making it inapplicable to many scenarios where microplastic detection is needed. Additionally, it is often infeasible to count nanoplastics individually through this approach. As a result, the California Water Board is considering “surrogate methods” such as flow cytometry, turbidity, and total suspended solids to more cheaply and efficiently detect microplastics while maintaining a high degree of accuracy.


Notably, Senate Bill 1422 does not discuss the filtration of microplastics from drinking water. Such topics need to be addressed in future pieces of legislation. Furthermore, efforts to prevent the continued production and spread of microplastics into the environment also need to be prioritized. Though California has taken important some initial steps, more change must happen if the state wants to target the spread of microplastics before it becomes a more prominent issue.



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