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During EVAs astronauts can receive significant additional radiation exposure to the skin and eyes due to the minimal shielding provided by the EMU. Occupational health and safety standards for astronaut radiation exposure exist, but there are no unique EVA rules nor requirements for the shielding provided by the EMU. The ALARA concept requires “reasonable” actions be taken to minimize additional exposure. This is most effectively accomplished by avoiding EVAs in orbital regions where additional exposure occurs. Measurements during the Shuttle program do not properly reflect actual EVA exposures because of the poor location of the dosimeter inside the EMU. A measurement program is underway to determine the shielding provided by the EMU, as well as the optimal location for accurate dosimetric measurements.

Space radiation exposure limits for astronauts are based on recommendations of the National Council on Radiation Protection and Measurements. These limits now include the age at exposure and sex of the astronaut. A recently-developed computerized anatomical female (CAF) model is discussed in detail. Computer-generated, cross-sectional data are presented to illustrate the completeness of the CAF model. By applying ray-tracing techniques, shield distribution functions have been computed to calculate absorbed dose and dose equivalent values for a variety of critical body organs (e.g., breasts, lungs, thyroid gland, etc) and mission scenarios. Specific risk assessments, i.e., cancer induction and mortality, are reviewed.