Project Summary/AbstractNaphthalene (NA) a simple polycyclic aromatic hydrocarbon is persistently present in the environment as abyproduct of combustion of fossil fuels and burning of tobacco and other products. Its ubiquitous presenceresults in widespread exposure to the general population. Certain occupational groups such as firefightershave elevated levels of exposure. Firefighters also have increased incidences of certain types of cancer. NA iscurrently classified by the International Agency for Research on Cancer (IARC) as a Class 2B Carcinogen.There is direct evidence of tumor formation in mice and rats but no direct evidence of carcinogenecity of NA inhumans at this time. The pathogenesis of tumor formation in mice and rats after exposure to NA is unclear;cytotoxic and genotoxic mechanisms are both proposed in the current literature. NA metabolism results in thegeneration of reactive intermediates such as 12-epoxide and reactive metabolites such as 14- and 12-naphthoquinone (NAQ). Reactive quinone and epoxide metabolites of similar compounds such asbenzo[a]pyrene have been shown to enact their carcinogenecity through DNA adduct formation. Published exvivo and in vitro data have demonstrated that NA metabolites can form adducts with DNA. The objective of thisstudy is to identify and quantify NA-DNA adducts in mouse lung as well as mouse and human blood to enableassessment of potential genotoxicity in firefighters. Several hypotheses will be tested: 1) Circulating reactiveNA metabolites particularly NAQs will form stable as well as depurinating adducts with DNA in both lungtissue and blood leukocytes in vivo; 2) the types and abundances of NA-DNA adducts in circulating leukocyteswill at least partly reflect adduct formation in the lung; 3) the types of NA-DNA adducts detected in circulatingleukocytes from exposed mice and firefighters will be similar; and 4) exposure to fire smoke will increase NA-DNA adduct levels in firefighters. These hypotheses will be tested through the application of 3 Specific Aims. InAim 1 I will Identify and quantitate NA-DNA adducts formed in wild-type (WT) mice following NA inhalationexposure with use of mass spectrometry methods. In Aim 2 I will dissect metabolic pathways responsible forNA-DNA adduct formation in the lung and circulating leukocytes of NA-exposed mice with use of uniquetransgenic mouse models (liver-Cpr-null liver-Ephx1-null and Cyp2abfgs-null). In Aim 3 I will characterizeNA-DNA adducts in blood specimens from firefighters and control donors. This project will provide directevidence for the formation of NA-DNA adducts in vivo lay the foundation for future studies of the genotoxicityof NA obtain evidence to support more extensive assessments of the carcinogenic risks of NA to firefightersand could have direct implications for the general population. Through the execution of this project and thehelp of this fellowship I will be fully trained in scientific and professional skills necessary for my careeradvancement as an independent researcher in academia.