Evaluation of the clastogenicity of water treated with sodium hypochiorite or monochioramine using a micronucleus test in newt larvae (Pleurodeles waltl)

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Abstract
We have previously described a micronucleus test using erythrocytes from larvae of the urodele amphibian Pleurodeles waltl (pleurodele). The test is based on a comparison of the levels of micronucleated erythrocytes in blood smears from larvae reared in water containing a clastogen, with the levels from larvae reared in purified water. We have employed this test to evaluate mutagenic activity of chlorinated or monochloraminated water devoid of all organic matter. (i) The level of micronuclei in erythrocytes was compared between a group of larvae reared for 12 days in chlorinated reconstituted ultrapure water treated with sodium hypochlorite, and a control group reared in just the reconstituted water. Sodium hypochlorite was added when both the food and medium were changed each day. Chlorine levels of 0.125 and 0.25 p.p.m. led to significant elevations of micronuclei. (ii) The possibility of indirect effects of chlorine through chemical interactions with the food were also investigated, using the following scheme: larvae were left for 3 h in chlorinated reconstituted ultrapure water and then placed in non-chlorinated water. Food was only introduced when they were transferred to the non-chlorinated water. This procedure was repeated for 12 consecutive days. Control larvae were reared in non-chlorinated water throughout this period. In this case results were also positive when the larvae were exposed for only 3 h to the chlorine (0.2 p.p.m. for 12 days) in the absence of food. (iii) This was the same as experiment 1 except that the water was chlorinated with monochloramine instead of sodium hypochlorite. The level of micronuclei increased with increasing concentration of monochloramine (0.05, 0.1 and 0.15 p.p.m.) although only the 0.15 p.p.m. concentration gave a statistically significant response. The results indicate that free chlorine and monochloramine are responsible for the clastogen effect in newt larvae.