Growing number of studies reveal the fact that the aquatic environment is threatened by increasing rate of chemical contamination. As a result, aquatic fauna is impacted by ubiquitous presence of these chemicals in waterbodies. Our research suggests that developmentally established epigenetic changes can survive in the body throughout the lifetime of the exposed individual and are associated with adverse health effects later in life. We aim to develop an adverse outcome pathway (AOP) incorporating epigenetic effects and associated phenotypic traits using medaka fish as an animal model. In the near future, regulatory agencies will need scientific information to classify chemicals that are transgenerationally harmful to humans and ecosystem.