The role of the quantities used in radiological protection for the assessment of the exposure to cosmic radiation

Calculations of atmospheric showers initiated by cosmic rays were carried out using the FLUKA Monte Carlo code. The fluences of various secondary particles, scored at different heights in the atmosphere and at different geomagnetic latitudes, have been converted to effective dose and ambient dose equivalent by means of appropriate sets of conversion coefficients. The relationship between these two quantities has been analysed and discussed as a function of altitude and latitude. The conclusion is that, with some exceptions of little protection significance, the operational quantity does not represent a prudent evaluation of the limiting quantity. The ambient dose equivalent could give a conservative estimate of the effective dose, at least at civil aviation altitudes, provided the radiation weighting factor assigned to protons is revised consistently with the relationship Q-L.