Invited contribution: acute toxicity testing, public responsibility and scientific challenges.

Knowledge of the acute toxic effects of chemicals is important for the protection of exposed humans. Since sufficient information in humans is often lacking, experiments on laboratory animals must be performed. The LD50 test, which requires large numbers of animals, has become the preferred procedure. It is now widely criticized on scientific and ethical grounds. This paper reviews the possibilities of using fewer animals to obtain relevant information on the acute hazards of chemical substances, but it also identifies the reasons why the traditional testing approaches cannot be changed immediately. An important problem is the practice of basing legal decisions on classification of chemicals in official lists of hazardous substances and for labeling purposes on LD50 values. Proposals are presented on how pain and suffering of the animals included in acute toxicity tests can be reduced. The use of in vitro systems for the evaluation of the hazardous properties of chemicals is discussed.