Real World Environmental Exposure Study With Healthy and Cystic Fibrosis Subjects

"* During 5 days the patient will walk 4 hours in urban green space (open-space areas reserved for parks and other green spaces, including plant life, water features -also referred to as blue spaces and other kinds of natural environment). The 3 hours walk tour includes a lunch break of one hour in the green space.~* During 5 days the patient will walk 4 hours in urban space (including 3 hours walk around the city and one-hour lunch break."