Would humans exposed to multiple periods of exposure to an ambient and inspired ppO2 of 0.4ATA and higher, have a tendency to present with a higher incidence of lung cancer than the general population? Commercial divers are regularly saturated at a ppO2 of 0.4ATA for period of 720 hours (30 days). While locked out on a dive, the inspired ppO2 is typically increased to 0.5ATA for periods of 8 hours in every 24. Also, during the later stages of decompression, the ppO2 might be raised to 0.6ATA. There is a significant population of humans that has been exposed to a pp02 of 0.4ATA for over 35,000 hours in their lifetime. Would they be expected to present with a higher incidence of lung cancer? Or is the exposure time too small to be of consequence? A significant quantity of the population are smokers.

If the exposure time is significant, is it possible that Oxygen does not play a role in carcinogenesis, but that it might play a role in accelerating mutation frequency ?