Following Postdoctoral training at the University of Michigan, Ann Arbor, USA during 1987-1989, he joined as a Scientist at the CSIR-Central Drug Research Institute, Lucknow in 1989 and then moved to the CSIR- Indian Institute of Chemical Biology, Kolkata in 1996. He also worked as a Visiting Scientist at the University of Texas Medical Branch at Galveston, Texas, USA during the year 1992 to 1994 on deputation. Dr. Giri started his career as a Genetic Toxicologist and then extended his research on Molecular Biology, Human Genetics and Human population monitoring. 

On superannuation from IICB he worked as an Emeritus Scientist of CSIR for 5 years and now working as an INSA-Senior Scientist at CSIR-IICB. Last 20 years he has been working on arsenic-induced health effects in the population exposed to arsenic in West Bengal. He has 116 International peer-reviewed publications to his credit. He was the past President of the Asian Association for Environmental Mutagen Societies (AAEMS). He is a Fellow of the National Academy of Sciences, India, Allahabad and also a Fellow of the Indian National Science Academy, New Delhi. He has served in the editorial boards of many international journals. His major expertise is in human population monitoring, Cytogenetic Damage, and Genetic susceptibility studies.