Summary Statement The covalent binding of genotoxins to DNA to form DNA adducts is considered to be a first step in chemically induced carcinogenesis. Measurement of DNA adducts in cells and tissues provides direct evidence of genetic damage and a means for assessing human health risk from exposure. However, the low levels at which adducts occur in affected organs and the limited amounts of DNA frequently available make their accurate measurement a highly challenging task. Methodology based on microcapillary liquid chromatography in combination with nano-electrospray mass spectrometry developed in this program has enabled us to achieve detection and quantification capabilities of adducts at levels similar to those frequently encountered in human exposure using low microgram quantities of DNA. Aromatic amines, compounds found in cigarette smoke, hair dyes and other environmental sources have been implicated in a variety of cancers including bladder cancer. 4-Aminobiphenyl (4-ABP), is a major carcinogen in this class of compounds and recent evidence has identified a potential relationship between mutational hot spots of the p53 gene in human bladder cancer and adduction sites of 4-ABP. A highly sensitive analytical protocol will be developed to quantify the DNA adducts of 4-ABP in urothelial cells from human volunteers involved in a smoke / cessation clinical study in order to assess the link between cigarette smoking and the risk for carcinogenesis. Use of urine as the physiological medium provides a non-invasive procedure which is more amenable for incorporation into human studies to assess the risk for bladder cancer from environmental chemicals. Agents which inhibit the formation of aromatic amine-DNA adducts will be tested in a human bladder cell line, thereby providing a broader perspective of their biological significance in their induction of bladder cancer. Development of methodology to characterize oligonucleotide adducts will expand the breadth of these clinical studies and will allow us to gain a better understanding of adduct formation in the context of base sequence and potentially identify the adduction in terms of specific domains of DNA and selected gene sequences. Additional novel technologies proposed here based on differential ion mobility spectrometry - mass spectrometry (DMS - MS) and the coupling of HPLC with MS and microNMR, will introduce new powerful tools to facilitate and improve the state of the art in the analysis of DNA adducts. We expect that the results of this work will help establish more definitively the degree of involvement of DNA adducts in the etiology of human cancer and define the relationship between bladder cancer and cigarette smoke.