A growing body of scientific literature reporting potential human health risks caused by microplastics and the presence of microplastics in drinking water sources has gained the attention of the public and policy makers alike. In California, the State Water Resources Control Board (State Water Board), water resources managers, and researchers are engaged in the early phase of a long-term collaborative effort to establish uniform water quality criteria for microplastics in the state. The State of California defines microplastics 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.”1

As drinking water utilities across California prepare for regulatory oversight of microplastics in drinking water, industry leaders have articulated an acute need to engage with stakeholders, including utilities, regulators, academic institutions, non-governmental organizations, policymakers, and the public about the state of science and knowledge gaps surrounding microplastics to inform potential policy and regulatory development. This document summarizes the findings and recommendations that emerged from two workshops held in California that brought diverse stakeholder groups together to discuss the state of the industry, identify knowledge gaps, and contextualize how to prioritize research needs from a utility perspective.