Genotoxic effects in erythrocytes of Oreochromis niloticus exposed to nanograms-per-liter concentration of 17[beta]-estradiol : an assessment using micronucleus test and comet assay

Pharmacologically active substances used in the treatment of human and animal illnesses may usually enter the aquatic environment via effluents from sewage treatment plants, as they are not completely biodegraded or removed during waste water treatment. 17[beta]-Estradiol genotoxicity was evaluated in Oreochromis niloticus (family Cichlidae) using micronucleus test, other nuclear abnormalities assessment, and the comet assay with erythrocytes. Fish were exposed to aqueous systems contaminated with 6 ng/L 17[beta]-estradiol for three periods: 24 h, 48 h, and 10 days. The results showed that 17[beta]-estradiol has genotoxic potential in differentperiods, since significant differences (P=0.036) were observed in the micronucleus frequencies of the 10-day exposure groups in relation to the control group. Also, the same was observed when comparing the nuclear abnormality frequencies (P=0.018) of the 24-h exposure group with the negative control group, and when using comet assay (P