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 LD50for oral, dermal, and intraperitoneal (IP) routes.Kowand 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 IP LD50=0.55) demonstrated the effect of similar versus dissimilar exposure routes on lethality, reflecting toxicokinetic differences. Simple linear regressions revealed significant correlations (BonferroniP<0.05) for trout LC50versus rat oral LD50and for trout LD50versus rat LD50when matched on exposure route. WhenKowwas included with multiple regression to consider the effect of hydrophilic/lipophilic partitioning on uptake and toxicity, correlations improved only for trout LC50versus rat oral LD50and for trout IP LD50versus rat IP LD50. Stratification of data into pesticides and nonpesticides failed to refine prediction of trout LC50from rat oral LD50. Simple regressions reported here and in the literature relating fish LC50and rat oral LD50exhibited varying degrees of correlation (r=0.26–0.99), reflecting differences in interspecies sensitivity, chemical group evaluated, and experimental methodologies.