objective: To assess the cytogenetic toxicological safety of fish raised in water containing effluent. Methods: Three experimental groups of fish were raised in water that contained effluent. Both fish samples and water samples were collected and analyzed. One group of fish raised in YuQiao reservoir (The source of drinking-water for Tianjin) and a reservoir water sample were collected at the same time as the clean control group. The mutagenicity of organic extracts of the fish was detected using the mice bone marrow micronucleus test and the mutagenicity of the water samples was detected using the micronucleus test of vicia faba root tip cells. Results: The results of the mice bone marrow micronucleus test on organic extracts of the fish showed that the micronucleus rates of the three experimental groups were significantly higher than that of the negative control group (peanut oil) and the clean control group (P