Comparisons of acute toxicity of selected chemicals to rainbow trout and rats.

Median lethal concentration (LC50) and dose (LD50) for 217 chemicals were compared over several exposure routes in rainbow trout and rats. Data were compiled primarily from on-line databases and included octanol-water partition coefficient (Kow), trout LC50, and trout and rat LD50 for oral, dermal, and intraperitoneal (i.p.) routes. Kow and molar lethality data were log-transformed for correlation and regression analyses. Median ratios (rat oral LD50/trout LC50 = 156, rat/trout oral LD50 = 0.80, rat/trout dermal LD50 = 0.43, rat/trout i.p. LD50 = 0.55) demonstrated the effect of similar versus dissimilar exposure routes on lethality, reflecting toxicokinetic differences. Simple linear regressions revealed significant correlations (Bonferroni P < 0.05) for trout LC50 versus rat oral LD50 and for trout LD50 versus rat LD50 when matched on exposure route. When Kow was included with multiple regression to consider the effect of hydrophilic/lipophilic partitioning on uptake and toxicity, correlations improved only for trout LC50 versus rat oral LD50 and for trout i.p. LD50 versus rat i.p. LD50. Stratification of data into pesticides and nonpesticides failed to refine prediction of trout LC50 from rat oral LD50. Simple regressions reported here and in the literature relating fish LC50 and rat oral LD50 exhibited varying degrees of correlation (r = 0.26-0.99), reflecting differences in interspecies sensitivity, chemical group evaluated, and experimental methodologies.