Research Product

Liver neoplasms were induced in two species of viviparous fishes Poeciliopsis lucida and P. monacha by repeated short-term exposures to an aqueous suspension of 5 ppm 7, 12-dimethylbenz(a)anthracene (DMBA). Predominantly hepatocellular neoplasms deceloped in 47 out of 106 fish surviving the period allowed for tumor development, 6-9 months after initial exposure to DMBA. The use of short-term exposure periods of 6 hours in young fish and up to 29 hours in adults reduced stress and mortalities caused by the toxicity of DMBA at 5 ppm. A lower concentration of DMBA, 0.25 ppm , failed to induce tumors in any of the surviving 230 of 295 young fish administered repeated 20-hour exposures. This study shows for the first time that DMBA is carcinogenic to fish.