DL50 is equivalent to the dose of a substance capable of killing half of the subjects undergoing the experiment. The lower its value, the more “toxic” is the tested substance. The classical methods, that are still widely used all over the world, are based on the exposure to certain quantities of a substance or mixture in one or more animal models, and on the study of the reaction of these models. In the calculation of the LD50 a statistically significant number of animals is treated with a minimal amount of substance / mixture and the effects are recorded. In this way the oral, dermal, cervical, inhalation, venous, spinal, etc. LD50 is calculated. The operation is performed on different animal models: mouse, rat, gerbil, rabbit, pig, monkey, etc.
Remarkably, even today, the methods used for the evaluation of the hazard of substances are the same ones that were used 50-60 years ago by the first classic toxicologists, that is to say the calculation of the LD50 through the use of animal models. There is no other scientific discipline where technological progress has been stopped for so long! Beyond the ethical issue, increasingly felt by companies and consumers, this resounding technological obsolescence is generating delays due to the very long lead time and the high costs involved.