26 X-Ray Safety J. Personnel Exposure Occupational Dose Limits Current limits for occupational radiation exposure have been established at levels to: • prevent deterministic/acute radiation effects (erythema, epilation), and • limit late/stochastic effects such as cancer or genetic damage to very low levels. These limits are based on the combination of external and internal exposures. To better understand the annual occupational exposure limits set by these regulatory agencies, the definitions of these limits are discussed below: External Dose • Shallow-Dose Equivalent (SDE) is the dose to the skin from an external source of ionizing radiation. • Eye (Lens) Dose Equivalent (LDE) is the dose equivalent to the lens of the eye from an external source of ionizing radiation. • Deep-Dose Equivalent (DDE) is the whole-body dose from an external source of ionizing radiation. Table 1 provides a summary of the current annual occupational dose limits for external and internal exposures. TABLE 1. Annual Occupational Dose Limits for Adult Workers Limit rem* Sievert (sv) Shallow Dose Equivalent, Whole-body 50 0.5 Shallow Dose Equivalent, Max. Extremity 50 0.5 Eye Dose Equivalent to the Lens of the Eye 15 0.15 Total Organ Dose Equivalent 50 0.5 Total Effective Dose Equivalent 5 0.05 *rem = the special unit of dose equivalent. Sievert is the S.I. dose equivalent unit. (1rem = 0.01 sievert).