Subjects will be healthy adults, non-smokers, recruited from the University campus and local community. Fifty% will be female. Recruitment of minority ethnic groups will be consistent with census population for central NC. Subjects will have a clinical history and lung function screening at protocol entry. Female subjects of childbearing age will have pregnancy testing. Equal numbers of NQO1 sufficient and deficient subjects, based upon genoytypic pre-screening and stratified by racial background will be studied. Subjects will also be genotyped for GSTM1 wild type or null genotype. As individuals with an increased BMI may respond strongly to O3 we will only recruit subjects with body habitus within normal range for gender, age, and racial group.