California Water Board Adopts Definition of Microplastics, Focuses on Drinking Water


Last month, California’s State Water Resources Control Board unanimously adopted a definition of microplastics, which includes plastic particles with three dimensions that are less than 5 millimeters in length.

California will use this definition to evaluate the extent of microplastics pollution in waterways in the state.

The complete definition is as follows:

‘Microplastics in Drinking Water’ are defined as solid polymeric materials to which chemical additives or other substances may have been added, which are particles which have at least three dimensions that are greater than 1nm and less than 5,000 micrometers (µm). Polymers that are derived in nature that have not been chemically modified (other than by hydrolysis) are excluded.

The definition includes footnotes further defining, “solid,” “polymeric materials,” “particles” and specifications for dimensions.

The Board took this step, as required by a 2018 law (S.B. 1422), which added Section 116376 to the Health and Safety Code. The law mandates a standard methodology to be used in the testing of drinking water for microplastics and creates requirements for four years of testing and reporting of microplastics in drinking water, including public disclosure of those results.

Over the next year, the Board will establish a standard to test drinking water for microplastics.

In a  press release announcing the definition, the Water Board says that “while other state, national and international agencies have defined microplastics, California’s definition is the first to focus specifically on microplastics in drinking water.”

More information is available on the Microplastics Resources Page of the State Water Board.

Contact ACA’s Riaz Zaman for more information.

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