This book is broadly based on an exhaustive research work conducted to see the presence of xenobiotics and insecticide residues in several abiotic and biotic substrates around a riverine estuary under the Indian Sundarban delta, and how these environmental pollutants are getting entry in the human food chain of the locality. It is a nice document showing spatio-temporal variations of a number of heavy metals and how estuarine ecosystem has been contaminated with these heavy metals like lead, cadmium, mercury etc. which were disseminating from river bound sewage and industrial effluents; and also the contamination pattern of the heavy metals and insecticides in substrates suggestive to anthropogenic inputs of pollutants in nature and bioaccumulation of those toxicants in higher trophic of the estuary, which urges immediate attention to take appropriate mitigation measures. Contents: 1. Introduction. 2. Xenobiotic pollution in India and abroad: a retrospect. 3. The research and its methodology. 4. Result of the experiment. 5. Overview of the research. 6. Annexure. 7. References.