Toxicology is a discipline involved adverse effects of chemical susbstances on living organisms, dose of chemical substances and its effect on exposed organisms. With rapid growth in industrialization, urbanization, pesticides usage in irrigation resulted in environmental pollution (air , water, soil pollution). Due to this, mainly water bodies get contaminated as they receives the effluents from industries, domestic waste, agricultural runoff which directly effects the aquatic organisms. The material in this book brings together all the information on comparative, seasonal estimation of heavy metals and its effects on the aquatic organisms, toxicological studies of detergents on cat fish, ammonia toxicity, effect of medicinal plants against dengue fever vector, natural insecticides influences of organic waste on metabolic activity of aquatic organisms and bioremedial studies. We are thankful to all the authors and other contributors for giving their valuable time and data. They are responsible for the work presented in the paper and if any plagiarism question arises they are answerable. The 1st author or corresponded author has to take responsibility. The editiors are not responsible for above issues. We are thankful to ISCA, Kolkata, ISCA President, General Secretaries , ISCA Executive Committee Members, and office bearers of the Indian Science Congress held at Manipur University, Imphal, Manipur from March 16 to 20, 2018 for encouraging us to hold symposium with focal themes, �REACHING THE UNRECAHED�. We extend our sincere thanks to all contributors who have contributed their articles for publications in these proceedings. This book will be very useful for researchers, scientists, students and all such entrepreneurs who are working in the field of public health.