Joint toxicity of mixtures of groups of organic aquatic pollutants to the guppy (Poecilia reticulata).

In this study acute lethal concentrations (LC50) to the guppy (Poecilia reticulata) were determined for mixtures of 4 groups of aquatic pollutants. The groups were composed of 11 nonreactive, nonionized organic chemicals, 11 chloroanilines, 11 chlorophenols, and 9 reactive organic halides. Earlier studies indicated that the joint toxicity within each of these groups was concentration additive, probably because of a similar mode of action. The joint toxicity of combinations of one representative from each group showed a high variance, but generally tended to be partially additive to concentration additive. This high variance is probably caused by the low number of compounds in these mixtures. Experiments with mixtures of whole groups gave more accurate results. The toxicity of a mixture of the first three groups, containing 33 well-known aquatic pollutants, was almost completely concentration additive. Concentrations of 0.04 of the individual LC50 values contributed to the toxicity of this mixture.