Comparative Toxicity of DDT and Four Analogues to Goldfish, Gambusia, and Culex Larvae

Abstract

A study of the comparative tolerance of goldfish, Gambusia affinis, and Culex apicalis to DDT and its p-halogen analogues is presented. One fish and 4-10 Culex larvae were placed in individual bowls. One ml. of an acetone soln. of DDT and its analogues, ranging from 0.0005 to 10 ppm., was added to each liter of water. Controls with 1 ml. of pure acetone in 1 1. of water had no effect on the animals. Gambusia was much less resistant than goldfish. The medium lethal dose of DDT was about 0.1 ppm. for goldfish, 0.01 ppm. lor Gambusia, and 0.001 ppm. for larvae. Mosquito pupae survived relatively high concs, of DDT and l-trichloro-2,2-bis (p-fluorophenyl)-ethene (DFDT) for 3 days, and many became normal adults. The presence of aquatic plants reduced the toxicity for fish. Some bowls with high concs, of DDT developed thriving colonies of Scendesmus. l-Trichloro-2,2-bis (phenyl)-ethane (DPT) was relatively non-toxic, DFDT was fairly toxic to fish while DDT and l-trichloro-2,2-bis (p-bromphenyl)-ethane (DBrDT) were 10 times more toxic to fish. 1-Tri-chloro-2,2-bis (p-iodophenyl)-ethane (DIDT) was somewhat less toxic than DDT. The toxicity of the series tended to increase with mol. wt. The avg. time to kill gambusia was as follows: DFDT, 4.5 hrs.; DDT, 7hrs.; DBrDT, 16 hrs.; DIDT, 54 hrs. DBrDT was relatively more toxic to fish than to mosquito larvae as compared with DDT. DFDT was relatively more toxic to larvae than to fish.