Variability in the performance of the 7-dCeriodaphnia dubiasurvival and reproduction test: An intra- and interlaboratory study

Abstract

The U.S. Environmental Protection Agency (EPA) has developed a 7-day Ceriodaphnia dubia survival and reproduction test for measuring the toxicity of effluents. This study evaluated the ease of performance and the intra- and interlaboratory variability of this 7-d test, using two reference toxicants (sodium chloride and potassium dichromate), two pulp and paper effluents, and two utility effluents Eleven different laboratories, representing academia, private industry, contractors, and the state EPA and federal EPA, participated in the study. The reference toxicants were tested twice during two separate test periods, and each industrial effluent was tested once. Using the EPA's criteria for a successful test (®80% survival and ® 15 young per female in controls), 56% of the 116 planned tests were completed as valid tests. Most tests were invalid because the laboratories were unable to initiate the tests successfully or because control survival was <80%. Seventy-eight percent of the tests that were initiated were successfully completed. Reproduction no-observed-effect-concentration (NOEC) values were generally somewhat lower than those for survival but had greater variability than survival NOEC values. The interlaboratory variability of the survival (LC50) and reproduction (IC50) results, expressed as the C V., ranged between 29.8 and 30.8% and between 28.9 and 39.0%, respectively. The study demonstrated that about half (56%) of the laboratories participating in the study were able to routinely complete the test successfully. Some of the laboratories experienced with other effluent toxicity tests were less prepared to complete this test successfully. Overall, the variability of the 7-d Ceriodaphnia tests that were completed was similar to the variability observed with other toxicity tests and with analytical chemistry measurements of environmental samples.