ABSTRACT
Toxicology is concerned with the harmful effects of chemicals upon living organisms. Chemicals that have harmful effects are described as poisons, a term that requires careful definition. This issue was first addressed by Paracelsus (1493), who famously said (in free translation): “All substances are poisons and there is none that is not a poison. It is the dose that makes the poison.” In other words, everything can be poisonous if the dose is high enough, but if the dose is sufficiently low, nothing is. This remains essentially true, even though it may be very difficult to administer a dose of some chemicals that is high enough to be harmful. It does, however, argue for caution when using the word poison. A substance can only be poisonous when it is given above a certain dose. At lower doses it is not poisonous. This simple principle is often not recognized in popular articles on pollution. Sometimes poisons are reported to exist in food or water at concentrations so low that there is no known risk to the living organisms that encounter them. Thus, the public can be alarmed through disinformation. A little sensation does help to sell newspapers.
