The provisions of this chapter do not apply to:
1° Exposures resulting from exposure to a natural level of radiation due to :
a) Radionuclides contained in the human body;
b) Cosmic radiation at ground level;
c) Radionuclides present in the earth’s undisturbed crust;
2° Exposures suffered by workers as a result of medical examinations to which they are subjected;
3° Exposure of workers other than air or space crews to cosmic radiation during an air or space flight.