Study to probe quality-assurance issues with Ceriodaphnia toxicity test

SCCWRP has launched a two-year statewide effort to ensure that laboratories conducting a toxicity test commonly used to monitor the water quality of wastewater and stormwater discharges are producing consistently high-quality, comparable results.

The study, which will be recruiting State-accredited laboratories as study participants through the end of March, will focus on the Whole Effluent Toxicity Ceriodaphnia dubia chronic reproduction test, a foundational toxicity test that uses a species of water flea to evaluate discharge water quality.

Environmental managers have used the C. dubia test for decades as part of a suite of toxicity tests to protect California’s enclosed bays, estuaries and inland water bodies from contaminated discharges. But in recent years, end users of the C. dubia test have expressed growing concerns about accuracy, repeatability and consistency associated with interpreting test results.

These concerns came into sharp focus over the last year, as the State Water Board was preparing to adopt numeric water-quality objectives for a full suite of aquatic toxicity tests – a policy change known as the Toxicity Provisions.

In response to end-user concerns about the C. dubia test, the State Water Board postponed implementing numeric objectives for the C. dubia test until 2024. The numeric objectives for other toxicity test species were adopted last December.

Both the regulated and regulatory communities have asked SCCWRP to lead the study to investigate the quality and comparability of C. dubia test results. In particular, researchers will examine flexibility in the existing standard test methods that allows end users to choose from among multiple options when implementing the test.

All stakeholders want to ensure C. dubia test methods are optimized to reliably detect toxic or non-toxic discharges statewide.

The study, which kicked off in December, will be overseen by two groups:

» An expert science review panel comprised of internationally renowned aquatic toxicologists

» A stakeholder advisory committee comprised of regulatory agencies, regulated parties and non-governmental organizations

SCCWRP is inviting all State-accredited laboratories to participate in the study, which is expected to be completed by the end of 2022.

For more information, or to join this study as a participating laboratory, contact Ken Schiff and Dr. Alvina Mehinto.