Dr. Gupta has always worked at the cutting edge technology pioneering sensitive methods to sequence tRNAs, followed by ultrasensitive 32P-postlabeling to measure DNA damage by environmental carcinogens. This assay has been used worldwide and still remains the most sensitive technology. His laboratory has applied this technology in cell culture and rodents exposed to a variety of carcinogens, and complex mixture such as cigarette smoke, and to tissues from cigarette smokers. These works have received several thousand citations.