Hazard Types

Radioactive bodies present two types of hazard: external exposure and radioactive contamination. The risks depend on the type and activity of radiation, whether the body will be opened, the number of days since administration of the radioactive material, and the time that persons spend in the vicinity of the body. External exposure is the primary concern if the body will not be opened. Individuals will rarely encounter high exposures around bodies of patients who were released from a hospital. However, exposure rates from bodies directly from a medical center may be appreciable; the appropriate tag will provide this information. Table 13-1 shows unshielded dose rates at two distances for some radioisotopes that may be encountered. The radioactivity level chosen for the first entry (99mTc) is typical administered activity and the level for the last four entries is activity below which a patient can be released from the hospital (3). Beta-emitting radioisotopes (32P, 89Sr, 90Y) are not considered external exposure hazards when the body cavity will not be opened so they are not addressed in Table 13-1. The listed dose rates will decrease significantly as time after administration of radioactive materials with short half-lives (6 h and 2.7 d for 99mTc and 198Au, respectively) increases. The same holds true for radioactive materials that are rapidly metabolized (99mTc and 131I). Activity in implants will decrease only by half-life.

Radiation exposure limits for members of the general public have been determined by federal regulatory agencies and radiation protection consensus groups (4,5). Individuals who are infrequently exposed to sources of radiation, for example, funeral home directors, are allowed to receive 100 mrem whole body annually. Individuals who are frequently exposed may receive 500 mrem whole body annually. Hands are relatively insensitive to radiation and therefore have a recommended annual limit of 5,000 mrem.

radioactivity

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