Current status of developmental neurotoxicity: an industry perspective

The chemical industry, along with the rest of society, shares the fundamental goal to protect the health and safety of children. Most of the existing testing programs for environmental chemicals primarily address the adult organism. Developmental neurotoxicity testing (DNT) studies are especially designed to address the specific risks of the developing nervous system. At time, DNT studies are not a regulatory requirement (US EPA) for all pesticides, however, these studies are recommended for and are now being required as Tier II studies for compounds which have shown evidence of neurotoxicity, endocrine modulation or in some cases developmental or reproduction toxicity. Laboratories, which are going to conduct this type of study, should have broad experience in reproduction toxicology and neurotoxicology studies. The DNT study includes a so called 'behavioral testing battery' to examine the development of autonomic, motor, sensory, and cognitive functions, where tests are performed at different time-points to cover important developmental stages of the nervous system. The development of the structure of the nervous system is carefully examined by neuropathological and morphometric examinations at two time points to detect morphologic abnormalities and growth defects. Critical issues concerning the conduct and interpretability of DNT study data include experience in the handling and logistics of large number of animals, historical control data, lack of scientific data of certain developing processes and uncertainties concerning the choice of the best methodical approaches.