The relative toxicity of 24 selected amines was evaluated in the 48 h Tetrahymena pyriformis static population growth impairment assay and compared with literature data for the 96 h Pimephales promelas flow-through mortality assay. Chemicals selected included normal and branched aliphatic primary amines, 4-position alkyl-substituted primary aromatic amines, as well as secondary and tertiary amines. Three amines were not toxic at saturation in the Tetrahymena system, whereas one amine was not toxic at saturation in the Pimephales system. Due to the aberrantly high toxicity of aniline observed in the Tetrahymena system, this chemical was not included in the analyses. For QSAR development, toxicity measured as log IGC50(-1) and log LC50(-1), respectively, was regressed against the log of the 1-octanol/water partition coefficient (log KOW). Both toxicity and hydrophobicity varied over five orders of magnitude. The model, log IGC50(-1) = 0.72(log KOW) - 1.64 (n = 20, r2 = 0.92) (1), was found to be a good predictor of toxicity in the Tetrahymena system. Similarly, the model, log LC50(-1) = 0.80(log KOW) - 1.80 (n = 23, r2 = 0.96) (2), was found to be a good predictor of toxicity in the Pimephales system. A comparison of Eqns (1) and (2) showed the models to be very similar. Therefore, as seen by the model, log LC50(-1) = 1.11(log IGC50(-1] - 0.01 (n = 20, r2 = 0.93) (3), a regression of the log toxicities gave a slope of one, an intercept of zero and a high correlation.
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