THE CONCERN FOR DEVELOPMENTAL NEUROTOXICOLOGY - IS IT JUSTIFIED AND WHAT IS BEING DONE ABOUT IT

In general, it is believed that the possibility of an adverse developm ental outcome following conception is relatively high. In most cases, the cause of the defect is not clear, although exposure to chemical ag ents at a critical period during development has been proposed to play a significant role. Consequently. regulatory agencies such as the U.S . Environmental Protection Agency (U.S. EPA) have promulgated testing guidelines for assessing developmental neurotoxicity of chemicals in a nimal testing protocols. Concerns have been expressed about the use of behavioral tests to evaluate chemicals for developmental neurotoxicit y, since some investigators believe that they lack predictive validity for human developmental neurotoxicity. Other investigators have indic ated that results from such studies are difficult to interpret because of a lack of standardization and sensitivity of the tests. Furthermor e, it has been argued that the developing organism is not especially s ensitive to chemicals or, if effects are observed, the developing orga nism is capable of compensating for the deficit. Recent research. howe ver. has adequately demonstrated that developing organisms are especia lly vulnerable to chemical agents if the exposure occurs at a critical period during development, while other studies have supported the ass umption that functional or behavioral effects observed in animal model s can be extrapolated to humans. These findings support the routine as sessment of chemicals for developmental neurotoxicity using functional end points and suggest that currently available methods could be used to determine more precisely the mechanism of chemical-induced develop mental defects.