Biological parameters and the acute LD50 test.

The acute LD50 is an inadequate index of toxicity because the catastrophe of death obscures the mechanisms and sites of action. Thus, nonlethal toxicity is not evaluated, and the LD50 is not extrapolated to the possible effects of low level exposures for long periods of time. Collaborative studies should be undertaken which would develop methods to reasonably permit such evaluation and extrapolation.