Introduction

Interactions of a poison with an organism can be considered in three phases: exposure, toxicokinetics, and toxicodynamics. During the

exposure phase

, contact is established between the poison and the body via one or more routes, e.g., a volatile air pollutant inhaled into the body. Then, during the

toxicokinetic phase

, the poison undergoes movement (Greek:

kinesis

) through the body. This movement includes absorption into the circulatory system, distribution among tissues (including those that will serve as sites of action), and then elimination from the body. The

toxicodynamic phase

is the exertion of power (Greek:

dynamos

) of the poison through its actions on affected target molecules and tissues. These phases can be overlapping so that once exposure occurs, all phases of action can be in effect simultaneously in the body.