3. What is toxicology?

For centuries, "toxicology" has been "the science of poisons", but this is a relative notion, because according to Paracelsus (1493): everything is poison, nothing is poison, only the dose makes the poison.

This sentence needs to be qualified with regard to endocrine disruptors and genotoxic substances, for which the dose alone does not make the poison.

Endocrine disruptors act like hormones; a low dose is enough to trigger effects on various organs. As for high-potential genotoxic substances, it is accepted that a single DNA alteration can trigger deleterious effects in cells.

Paracelsus introduced the notion of threshold of effect and the dose/effect relationship.

For each substance there are :

• a level with no effect ;

• ...