There is not much ozone in the atmosphere, all molecules at eye level would build a layer of a few millimeters. There is also not much usable atmosphere around our planet, oxygen is down to half at 5km and beyond 30km you’ll see stars on pure black above a blue planet.
Technically the atmosphere ends with exosphere phasing out at 100km. SpaceShipOne pilot Brian Binnie returned in good shape from 112km, but consult your doc before planning an altitude of 6,000m without life support.
Most triatomic oxygen exists in the stratosphere between 15 and 25 kilometers and filters out DNA damaging solar UV-B radiation. It is estimated that 1% less ozone increases some forms of non-melanoma skin cancer by 3%.-> continue reading