 - Gender: Females or Males. If the subject is female and of childbearing potential first menses has occurred, she must have a documented negative pregnancy test at screening and prior to each mucociliary clearance study. Those of childbearing potential must be abstinent or using an acceptable method of birth control i.e. an Intrauterine Contraceptive Device with a failure rate of 1, hormonal contraceptives or a barrier method. 