Genotoxic effects of two industrial effluents and ethyl methane sulphonate in Clarias lazera

Clarias lazera (cat fish) kept in laboratory aquaria for 3 weeks and then exposed to 0.5, 1.0, 2.0, 4.0 or 8.0 mg ethyl methane sulphonate (EMS) per litre or 10, 20, 40 or 60 per cent brewery or textile-mill effluent for 14 d. Analysis of the frequency of numbers of micronucleated erythrocytes by linear regression and variance analysis showed a significant increase in micronucleus frequency following exposure to EMS or effluents with a positive dose-response over the whole range. The textile-mill effluent dose-response curve was significantly higher than that of the brewery effluent. The possibility of using the micronucleus test in fish for the screening of aquatic genotoxicants is discussed.