Microplastics

As stated in Health and Safety Code section 116350 et seq., California Safe Drinking Water Act (Act) requires the State Water Resources Control Board (State Water Board) to administer provisions related to drinking water to protect public health. The Act allows the State Water Board to conduct research, studies, and demonstration programs to ensure provision of a dependable, safe supply of drinking water, which may include improving methods to identify and measure the existence of contaminants in drinking water and to identify the source of the contaminants. The Act also grants the State Water Board the authority to implement regulations that may include monitoring of contaminants, and requirements for notifying the public of the quality of the water delivered to customers.

On September 28, 2018, Senate Bill No. 1422 was filed with the Secretary of State , adding section 116376 to the Health and Safety Code, and requiring the State Water Board to adopt a definition of microplastics in drinking water on or before July 1, 2020, and on or before July 1, 2021, to adopt a standard methodology to be used in the testing of drinking water for microplastics and requirements for four years of testing and reporting of microplastics in drinking water, including public disclosure of those results.

Press Release: State Water Board addresses microplastics in drinking water to encourage public water system awareness (06/16/2020)

Proposed Action

  • Adopted definition of microplastics : June 16, 2020
  • Board workshop on standardized methodology, sampling & analysis plan, health effects, and accreditation: anticipated Fall, 2021
  • Board adoption on standardized methodology, sampling & analysis plan, health effects, and accreditation: anticipated Winter, 2021 - 2022

Consistent with Health and Safety Code section 116376 and within its authority, the State Water Board is reviewing existing research and studies to accomplish the following tasks:

  • On or before July 1, 2020: Adopt a definition of microplastics in drinking water;
  • On or before July 1, 2021:
    • Adopt a standard methodology for testing of microplastics in drinking water;
    • Adopt requirements for four years of testing and reporting of microplastics in drinking water, including public disclosure of those results;
    • Consider issuing quantitative guidelines (e.g., notification level) to aid consumer interpretations of the testing results, if appropriate;
    • Accredit qualified laboratories in California to analyze microplastics in drinking water.

Health and Safety Code section 116376 allows the State Water Board to implement these tasks through the adoption of a Policy Handbook that is not subject to the Administrative Regulations and Rulemaking requirements of Government Code section 11340 et seq.

An update on the implementation on Health and Safety Code section 116376 was presented to the California State Assembly Committee on Environmental Safety & Toxic Materials on March 2, 2021. A recording of the presentation is also available.

Definition of Microplastics in Drinking Water

On March 19, 2020, a proposed definition of 'microplastics in drinking water' to be considered for adoption by the State Water Board was made available, along with a draft Staff Report.

A proposed definition of 'microplastics in drinking water' prepared on February 1, 2020 was reviewed by an external panel of experts. The draft definition reviewed by the expert panel and their comments comments are available.

A public workshop detailing the proposed definition of 'microplastics in drinking water' was held at the State Water Board on April 8, 2020. The presentation was recorded and is available.

The proposed definition of 'microplastics in drinking water' was made available for public comment from March 24 - April 24, 2020. Details regarding the public comment period, notice of staff workshop, and hearing for Board adoption were made available on March 24, 2020.

State Water Board responses to comments on the March 19 proposed definition of 'microplastics in drinking water' were prepared and made publicly available on June 3, 2020 in document and table format. In response to public comments, a revised draft staff report was made available on June 3, 2020.

The State Water Board considered a resolution to adopt a proposed definition of 'microplastics in drinking water' at the June 16, 2020 Board Meeting (Notice). The final adopted resolution and definition was made available on July 27, 2020.

Health Effects of Microplastics

To inform the State Water Resources Control Board's consideration of issuing a health-based guidance level for microplastics in drinking water to aid consumer interpretation in accordance with Health and Safety Code section 116376, a Microplastics Health Effects Workshop was convened. The workshop brought together an international group of experts to review available toxicity studies on microplastics and identify the primary pathways by which microplastics affect biota, as well as prioritize microplastics characteristics (e.g., size, shape, polymer type) that are of greatest health concern, and, if appropriate, identify critical thresholds for each at which those biological effects become pronounced. The Health Effects Workshop is a joint project between the State Water Resources Control Board, the Ocean Protection Council, the Southern California Coastal Water Research Project, the San Francisco Estuary Institute, and the University of Toronto.

As part of the Health Effects Workshop, a series of five webinars was held from October 19 to November 16, 2020. The webinar series was free and open to the public, with the intent of informing the community (e.g., scientists, environmental managers, stakeholders) about the latest scientific developments regarding the potential health effects of microplastics. Webinar recordings are available at the Southern California Coastal Water Research Project's webpage.

Following the webinar series, microplastics experts deliberated about how to develop thresholds for when biological effects are likely to be triggered as a result of microplastics exposure. The experts investigated the feasibility of developing these thresholds for both drinking water and for organisms exposed in the ambient environment. The experts summarized their findings during a two-hour, public webinar meeting on September 8, 2021. Webinar recordings are available on the Southern California Coastal Water Research Project's webpage

Contact Information

Melissa Hall, P.E.
Senior Water Resource Control Engineer
(916) 323-0373
Melissa.Hall@waterboards.ca.gov

Scott Coffin, Ph.D.
Research Scientist III
(916) 323-0375
Scott.Coffin@waterboards.ca.gov