Contents: 1. Heavy metals in freshwater ecosystem. 2. Toxicity of heavy metals and pesticides in the environment. 3. Heavy metals in the environment. 4. Iron. 5. Heavy metal toxicity mechanism and their harmful effects on living organisms. 6. Phyto-remediation by mustard crop of heavy metals (CR, PB & NI) in tannery waste and sewage sludge-amended soil. 7. Effect of arsenic on certain biochemical parameters in liver tissue of an air breathing fish channa gachua. 8. Fluoride contamination and its effects. 9. Screening and identification of healthy population of helicoverpaarmigera (hubner) (lepidoptera: noctuidae) for the pilot scale production of its bio-pesticide. 10. Minimizing pesticide risk to bees in crops. 11. Impact of malathion on oxygen consumption in an air breathing fish channa gachua. The present book updates the subject matter related to the role of metals in biological system, impact on organisms and analytical techniques of various heavy metals, metalloid and pesticides in different environmental components. The book will be helpful for the researchers, academia working in the field of analytical science, toxicology, chemical analysis of various environmental components, agro-chemicals, geo-chemicals, ecological system and pesticide residues.