An evaluation of the fathead minnow seven‐day subchronic test for estimating chronic toxicity

Abstract

AbstractRenewal and flow‐through subchronic tests were conducted on fathead minnows (Pime‐phales promelas) with nine chemicals and the results compared to early life stage (ELS) or life cycle toxicity values for one water type. In addition, ELS tests were conducted simultaneously with four chemicals to compare 7‐d and 32‐d test values.Reproducibility of the 7‐d test was high. The no observable effect concentrations (NOECs) and lowest observed effect concentrations (LOECs) of the 7‐d tests agreed with those of the life cycle test for 60% of the chemicals tested, similar to the agreement of the ELS tests to the life cycle tests for the same chemicals. ELS and 7‐d NOECs and LOECs for seven of the nine chemicals agreed within a factor of two.For four chemicals, embryos exposed before the 7‐d renewal test did not show greater sensitivity than unexposed embryos; with carbaryl, exposed embryos were less sensitive than the unexposed fish. Renewal and flow‐through tests agreed well. Growth was the most sensitive parameter for 59% of the tests and survival was the most sensitive for only 11%.