SWRCB Adopts Microplastics Definition (June 16, 2020)

At today’s State Water Resources Control Board (SWRCB) meeting, the Board voted to adopt the proposed definition of microplastics in drinking water.


In 2018 California adopted a new law that required the SWRCB Division of Drinking Water (DDW) adopt a definition of microplastics in drinking water before July 1, 2020.

On March 24, 2020 the SWRCB DDW published for a 30-day public comment period a proposed definition of microplastics in drinking water.  A copy of DDW’s responses to the public comments is enclosed (Microplastics_DDW Response to Public Comments_draft).

Prior to today’s Board meeting, based on public comments, DDW staff made the following changes in the proposed definition: DDW staff changed the phrase “which have at least two dimensions that are greater than 1 and less than 5,000 micrometers” to “which have at least three dimensions that are greater than 1 nm and less than 5,000 micrometers.”

The enclosed document DDW Staff Report Microplastics_Revised (DDW Staff Report Microplastics_Revised) includes the proposed definition of microplastics as presented today to the SWRCB members.   During today’s meeting a minor change was made to footnote #3 (size-based nomenclature) of the proposed definition.

Next Steps

The 2018 law requires that by July 1, 2021 the SWRCB must adopt test methodology for microplastics in drinking water, adopt requirements for four years of testing and reporting on microplastics in drinking water, and develop accreditation requirements for laboratories to analyze microplastics.

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About Dan Askenaizer

Dr. Askenaizer leads WQTS’ work on regulatory compliance support for many of our water agencies clients. Dr. Askenaizer tracks water quality and treatment regulations at the Federal and State levels and provides regulatory updates to our clients. Dr. Askenaizer has strong expertise in the development of Regulatory Monitoring and Compliance Plans (RMCPs), which he has completed for a number of water agencies. He has also been working on a number of projects dealing with the development of distribution system monitoring plans and review of nitrification control strategies. Prior to joining WQTS, Dr. Askenaizer was the Water Quality Manager for the Glendale Water and Power. Under his leadership, the Water Quality Group conducted a demonstration-scale study of chlorite for nitrification control and a pilot-scale study of biological treatment for removal of nitrate. Dan has 30 years of experience working on projects dealing with regulatory, water quality and public health issues. Dan has given numerous presentations at workshops and round-tables across the country for water utilities. Dan was instrumental in developing and implementing a Mentoring Program for water staff and was involved in a Sustainable Development team.