LOOKING FOR CAUSES OF NEURAL-TUBE DEFECTS - WHERE DOES THE ENVIRONMENT FIT IN

The neural tube defects anencephaly and spina bifida are important cau ses of infant mortality and morbidity. Recent studies suggest that man y of these defects can be prevented by the periconceptional use of fol ic acid. At the same time, we do not know what causes most cases of ne ural tube defects and there is evidence to suggest that they are etiol ogically heterogeneous. Additional research needs to be directed towar d the role of occupational and environmental exposures in the etiology of these defects. Importantly, studies need to examine embryologicall y and anatomically specific types of defects and develop accurate info rmation on biologically relevant exposures. Exposures toward which att ention needs to be directed include organic solvents; agricultural che micals, including pesticides; water nitrates; heavy metals such as mer cury; ionizing radiation; and water disinfection by products. We also recommend that additional attention be paid to mechanisms of neural tu be closure and to the potential role of genetic heterogeneity in the a bsorption and metabolism of xenobiotics and in their effects on the ne ural tube.