[Effects of chemical mixtures on embryonic development: examples of experimental models and problems in risk...

Toxicological risk deriving from the exposure to mixtures of toxic substances, the study of possible interactions among them and their mechanisms of action are of special interest in prenatal toxicology. In fact, embryo is a dynamic complex system whose gradual development substantially modulates the extent and type of damages to which it may be sensitive, through specific, critical periods of sensitivity. In this paper, a number of types of interactions among toxic substances which show the same mechanisms of action and/or the same target site, are analysed. Besides, pharmacokinetic interactions among teratogenic agents and substances modulating their metabolism, need specific evaluations because of the wide variability of possible events. In conclusion, risk assessment in prenatal toxicology has to put greater attention to the various types of effect and pharmacokinetic interaction since they might result in an increasing risk at low doses.