The goals of the research are designed to accomplish genetic association studies of candidate genes in healthy normal individuals exposed to 0.2 ppm for 2.25 hours with intermittent exercise in order to search for associations between defined genotypes/haplotypes and 3 specific in vivo respiratory endpoints: a) change in FEV1 immediately after ozone exposure; b) change nonspecific bronchial reactivity as reflected in the change in methacholine PC20 FEV1 24 hours after ozone exposure ; and c) change in lung epithelial integrity as reflected in the Clearance Halftime of technetium 24 hours after ozone exposure. These studies have been carried forward to take place in 4 phases:

i) healthy individuals have been exposed to O3 using our standard exposure protocol; and we will increase the numbers of individuals available for study.

ii) perform genetic association studies for the endpoints of spirometry (FEV1, FVC, FEV1/FVC), PC20 FEV1 for methacholine, and epithelial integrity (Clearance Halftime) for 3 candidate O3 response genes taken from literature searches and/or previously characterized to demonstrate associations. These physiologic endpoints have been examined in terms of both a continuum of response, and discrete "responder" and "non-responder" endpoints.

Inclusion Criteria:

• Subjects with normal lung function values, and of normal body habitus (i.e., < BMI of 30);
• Do not have a history of lung disease, and not taking any medications for lung disease or other clinical disorders, and no prior or current smoking history.

Exclusion Criteria:

• Non-willingness to sign a consent form for participation.

Healthy adults, 18-35 y of age, both genders.