ObjectiveTo study the effects of estradiol-17 beta (E₂), nonylphenol (NP), polychlorinated biphenyls (PCBs), Cd²⁺, Zn²⁺ and their mixture on the SOD activity in Tanichthys albonubes. MethodsT. albonubes were exposed to the substances mentioned above at different concentrations for 14 days. The activities of SOD at 7 days and 14 days were detected. ResultsThe activity of SOD was significantly raised after the treatment at lower E₂ levels for 7 days. It did not change obviously when the concentration of E₂ was more increased or the exposure time was protracted. At the low concentration of NP, the activity of SOD almost had no changes, but it was raised observably at high concentration. The activity of SOD was decreased after exposure to middle and high PCB concentrations for 7 or 14 days, and so did it in low PCB concentrations for 14 days. Furthermore, the higher the concentration of PCB or the longer the exposure time, the more the SOD activity was decreased. All the Cd²⁺ and Zn²⁺ concentration groups designed in the study were found to restrain the SOD activity, and the SOD activity decreased more significantly with the extension of exposure time. ConclusionsThese substances obviously impact the SOD activity in T. albonubes. A good concentration-response relationship is found between SOD activity and E₂, NP, PCBs, Cd²⁺, Zn²⁺exposure concentrations. Compared with individual effects, the joint effects of these compounds are related to exposure time and (or) the mixture concentrations. Most of the combinations show an enhanced toxicity.