Final intercalibration exercise completed for Ceriodaphnia dubia toxicity testing study

A SCCWRP-led study probing the sources of inconsistent results produced by California-accredited laboratories that use a toxicity test commonly used to evaluate discharge water quality has completed its second and final intercalibration exercise.

The intercalibration exercise, completed in June, invited participating laboratories to perform the Ceriodaphnia dubia chronic reproduction test during three rounds of split-sample testing. The exercise followed a training workshop for all participating laboratories that was intended to help reduce variability in test results.

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

Findings from the laboratory intercalibration exercises will be used by the project’s expert science panel to develop test recommendations for improving test results. The draft recommendations are expected to be released in early September 2023.