Variability in the performance of the seven-day fathead minnow (pimephales promelas) larval survival and growth test: An intra- and interlaboratory study

Abstract

The U.S. Environmental Protection Agency (EPA) has developed a “Seven-Day Fathead Minnow Larval Survival and Growth Test” for measuring the toxicity of effluents. This study evaluated the ease and performance and the intra- and interlaboratory variability of this 7-d test using two reference toxicants (sodium pentachlorophenate and potassium dichromate), two refinery effluents, and one low-volume internal waste stream from an electric power plant. Ten different laboratories representing academia, private industry, contractors, the state EPA, and the U.S. EPA participated in this study. The reference toxicants were tested twice during two separate test periods, and each effluent and waste stream was tested once. Using EPA's criteria for a successful test, 90% of the 140 planned tests were completed as valid tests. The intralaboratory variability of the survival (LC50) and growth (IC50) results for tests conducted concurrently (spatial variability), expressed as the coefficient of variation (C.V.), ranged between 5.9 and 15.6% and between 9.1 and 26.1%, respectively. The intralaboratory variability of the survival (LC50) and growth (IC50) results for tests conducted at two different times (temporal variability), expressed as C.V., ranged between 14.5 and 25.3% and between 17.6 and 22.7%, respectively. The interlaboratory variability of the survival (LC50) and growth (IC50) results, expressed as C.V., ranged between 24.1 and 43.7% and between 22.4 and 88.0%, respectively. Overall, the variability of the 7-d fathead minnow test was similar to the variability observed with other toxicity tests and with analytical chemistry measurements of environmental samples.