Acute and Chronic Effects of Kepone and Mirex on the Fathead Minnow

Publisher Website
Google Scholar
Abstract
Acute and chronic toxicity studies were conducted with fathead minnows (Pimephales promelas) and the organochlorine insecticides Kepone and mirex. Kepone was highly toxic to fathead minnows under acute conditions; 96‐hour LC50ˈs (median lethal concentrations; 95% confidence limits in parentheses) were as low as 340 (289–400) μg/liter and 96‐hour EC50ˈs (median effective concentrations; 95% confidence limits in parentheses) were as low as 18 (15–22) μg/liter. The observed effect, upon which the EC50 calculations were based, was an extensive hemorrhage associated with an apparent fracture or dislocation of the vertebral column in the region of the dorsal fin. Mirex was not acutely toxic to fathead minnows, even at concentrations that exceeded its maximum water solubility. Chronic toxicity testing indicated that the maximum acceptable toxicant concentration for fathead minnows exposed to Kepone was between 1.2 and 3.1 μg/liter. Adverse chronic effects of mirex were limited to a possible impairment of reproductive success at 34 μg/liter, near the compoundˈs maximum water solubility. Fathead minnows accumulated both Kepone and mirex. Accumulation factors (toxicant concentration in fish tissue divided by toxicant concentration in exposure water) were 1,100–2,200 for Kepone and 12,000–28,000 for mirex, although tissue residues of mirex continued to increase through 120 days of exposure. Tissue residues of Kepone were below detection limits after 7 days of elimination, while 46% of the mirex residues remained in fish after they were held 56 days in mirex‐free water.