[Chronobiology and industrial medicine: approach to the evaluation of the toxicological risk in occupational exposure to xenobiotics].

The recent interest of occupational medicine for chronobiology has been mainly devoted to the fields of energy expense and nutrition, work performance, social and work organization. However, experimental studies of chronotoxicology have showed that the effects of noxious agents vary according to biological time of exposure, nature of toxic agents, and target organ. This fact indicates that the different responses to xenobiotics depend on the temporal variation of susceptibility, which represents a characteristic of each living species. In some instances, the biological differences of susceptibility have been regarded as a consequence of the different capability of the organs to biotransform the xenobiotics itself. Another aspect of chronotoxicology seems to be of great interest for the occupational toxicology. In fact, the evaluation of the toxicological risk in work environment is based, in addition to the environmental monitoring, on the measure of indices both of exposure and effect. Recently, it has pointed out the importance of the knowledge of the temporal behaviour of these indices to avoid misinterpretations of the results. These considerations may lead to a new and wider approach to the evaluation of environmental risk.