On June 16, 2020, the California State Water Resources Control Board (CA SWRCB or Board) became the first regulatory agency in the world to specify and adopt a definition of ‘Microplastics in Drinking Water’. The CA SWRCB unanimously adopted the microplastic definition, which includes plastic particles with three dimensions that are greater than 1 nanometer and less than 5 millimeters in length. The definition excludes polymers that are derived in nature that have not been chemically modified (other than by hydrolysis).

Joaquin Esquivel, Chair of the CA SWRCB is quoted as saying, “This first, but critical step, in establishing a definition of microplastics in drinking water will provide the basis for further investigation and work at the Water Board. We must find ways to comprehensively address the problem, and the Water Board looks forward to guiding the discussion on how best to do so”. The Board’s action comes in response to 2018 state legislation that required the adoption of a microplastics definition by July 1, 2020.

Before July 1, 2021, the Board must also:

  • Adopt a standard testing methodology for measuring microplastics in drinking water
  • Adopt requirements for four years of testing, reporting, and public disclosure of the monitoring results, including issuing quantitative guidelines (e.g., notification level) to aid consumer interpretations of the results
  • Accredit California laboratories to analyze microplastics in drinking water

The above actions need not be incorporated in a formal rulemaking, but instead might be implemented through adoption of policy. Those wanting to know more about the new microplastics definition and forthcoming state regulations can contact Melissa Hall,  Senior Water Resource Control Engineer at the CA SWRCB at Melissa.Hall@waterboards.ca.gov or (916) 323-0373.