4. Distribution in organizations

The exposure phase involves the distribution of the substance in the environment according to its physico-chemical properties; the substance will be in soluble or micelle form, adsorbed on particles, native or associated with other elements, free or stored as a reserve in the sediment. This phase determines the substance's bioavailability to penetrate the target organism, leading to the toxicokinetic phase. This last stage is divided into four phases: substance absorption, distribution in the body, metabolism and elimination.

Through its constant interactions with its environment, an organism brings in both useful molecules (such as food, trace elements and oxygen) and unnecessary molecules (such as xenobiotics – pollutants – or pathogens). In turn, an organism metabolizes endogenous molecules called endobiotics (e.g., compounds resulting from the synthesis and...