Recent findings that describe endocrine disruption caused by exposure to low levels of certain chemicals in the environment have led to a paradigm shift in the way toxicology studies are designed. Toluene at high levels damages the human central nervous system; however, the effects of toluene at low levels have not been studied. The authors used serum-free mouse embryo cells-a precursor of astrocytes-to predict the effect of chemicals on developing brain cells. When serum-free mouse embryo cells were exposed to low levels of toluene, induction of glial fibrillary acidic protein was inhibited. This study demonstrated that environmentally relevant low levels of toluene could disrupt normal prenatal brain development.