1. Toxicokinetics (absorption, distribution and excretion of xenobiotics)

The toxicity of a xenobiotic (pollutant, toxin, drug, narcotic, etc.) depends in part on the dose to which the organism is exposed (dose-response concept), and more precisely on its concentration at the site of action (organ or tissue).

The bioavailability of a xenobiotic can be described in terms of absorption, distribution, biotransformation and excretion, all of which may occur simultaneously. Each stage may have a consequence in terms of toxicity.