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The California State Water Resources Control Board (“Board”) is proposing to adopt a definition for microplastics.

The definition would be applicable to the Board’s drinking water program.

The Board is one of six environmental entities operated under the authority of the California Environmental Protection Agency.

The Board proposal is stated to be driven by California legislation (Section 116376 to the California Health and Safety Code) which requires adoption of a definition for microplastics in drinking water on or before July 1, 2020. The same legislation also requires the Board adopt on or before July 1, 2021, a standard methodology to be used in the testing of drinking water for microplastics. Also required to be promulgated are requirements for four years of testing and reporting of microplastics in drinking water. Public disclosure of those results would be mandated.

The Board proposes to define “microplastics in drinking water” as:

Solid polymeric materials to which chemical additives or other substances may have been added, which are particles which have at least two dimensions that are greater than 1 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.

A link to the Board notice can be downloaded here.