The book has been prepared by keeping in view of syllabi prepared by different International universities on the basis of latest curriculum. The present book has evolved out of my experience in classroom teaching at undergraduate level. Some salient features of the book are: The book has been written in simple and comprehensible language. A large number of illustrations, simple chemical reactions, pictures and interesting problems have been provided to make the reading interesting and understandable. The important basic laws of fundamental concepts in environmental chemistry and toxicology have been given to help the students to focus on them. The questions that have been provided are in the tune with the latest pattern of examination. I believe that, the book contains all it is needed to understand the subject in a simple manner. I am confident that, the present edition will be warmly received by the students and the learned colleagues. However, now work is perfect. I would welcome suggestions from the teaching fraternity and students for further improvement of the book.