USE OF THE VIBRIO-HARVEYI TOXICITY TEST FOR EVALUATING MIXTURE INTERACTIONS OF NITROBENZENE AND DINITROBENZENE

A mixture toxicity investigation was conducted using the bioluminescen t marine bacterium Vibrio harveyi as the test organism for dual combin ations of nitrobenzene and dinitrobenzene. Change in bioluminescence w as used for determination of toxicity, combination toxicity was evalua ted using statistical comparisons, isopleths (isobologram and isobole plot), an additive index, and a mixture toxicity index. Both isopleths and mixture toxicity indices suggest that various combinations are ad ditive, while the additive index value suggests antagonism. All evalua tions were conducted as equitoxic mixtures. Statistical determination was performed using the z test. Numerous comparisons were different at the 1% level. Slope of line associated with isobole plot was suggeste d to be an important factor, resulting in statistical differences amon g comparisons. Distribution, using the Shapiro-Wilk test, was determin ed for both individual combination groups and solution composition in isopleths. All distributions evaluated were normal. These results sugg est that the V. harveyi toxicity test is useful for mixture toxicity s tudies. (C) 1997 Academic Press.