Reproductive Impairment in the Zebrafish, Danio rerio, upon Chronic Exposure to 1,2,3-Trichlorobenzene

Most organic pollutants are supposed to act via the mechanism of nonpolar narcosis upon acute exposure. Because the chronic effects of these compounds are still relatively unknown, in this study a chronic toxicity experiment was performed with zebrafish, Danio rerio, exposed to 1,2,3-trichlorobenzene (123TCB), a nonpolar narcotic. Fish were exposed in a flow-through system for 68 and 147 days. Parameters measured are survival, growth, reproduction, and glycogen and protein content. The only parameter which was influenced was the number of eggs produced per female, resulting in an EC50 of 40 μg/L. Using this value and acute toxicity data for 123TCB, an acute to chronic ratio (ACR) of 80 was calculated, which is larger than ACRs for other species exposed to nonpolar narcotics. This finding might indicate that compounds acting by nonpolar narcosis in acute tests can have completely different effects upon chronic exposure.