A comparison of the acute toxicity of chemicals to fish, rats and mice

The acute toxicity of chemicals to rainbow trout, as shown by intraperitoneal injections (IP LD 50 ), oral dosing (oral LD 50 ) and aqueous exposure (LC 50 ) was compared with published values for IP LD 50 s and oral LD 50 s of mice and rats. The method of comparison was by simple linear regression analyses of log‐transformed data, modified to recognize that X (fish toxicity) was neither fixed nor measured without error. Within‐species comparisons demonstrated very strong linear correlations ( r =0.866–0.998) between IP and oral LD 50 s. Variability was least for the fish data since it was all generated in one laboratory. Comparisons between species of IP and oral LD 50 S gave correlation coefficients ranging from 0.59 to 0.95 with the majority over 0.80. Correlations were best ( r =0.83–0.94) between fish LD 50 s and rat and mice IP LD 50 s. Correlations were poorest between fish and mammalian oral LD 50 s ( r =0.59–0.66) because the sample sizes and the ranges of values were very small. In all cases, the slopes were close to, or equalled, 1.0. Comparisons of fish LC 50 s to fish or mammalian LD 50 s were not as successful. Correlation coefficients ranged from 0.19 to 0.83. Presumably the cause was the aqueous exposure. Interactions of the chemicals with water (e.g. dissociation) and with lipid membranes (partitioning) should cause considerable variations in uptake efficiency. However, adjustments of LC 50 s for dissociation constants and partition coefficients did not improve these correlations, probably because there were few chemicals for which all data were available. These comparisons demonstrate a potential for a wider use of surrogate species in toxicity testing and for adapting existing data from mammalian toxicology to aquatic hazard assessments.