34 Radioactive Materials Safety Manual Environmental Health and Safety Bioassays Assessing internal radiation exposures is far more difficult than the determination of external exposure. Procedures for this purpose are collectively termed “bioassays”. For many water-soluble compounds labeled with low energy beta emitters, such as ³H and 14C, urinalysis bioassay is conducted utilizing liquid scintillation counting. For radionuclides of iodine, internal exposure may be assessed by using a NaI scintillation probe to externally measure the amount of ionizing radiation emitted from the thyroid. In general, urinalyses are performed by EH&S only for unusual situations such as accidents involving potential radionuclide uptake or for certain experimental procedures where ingestion or inhalation of radionuclides is possible. Thyroid bioassays, on the other hand, are conducted whenever individuals perform radio iodinations or may have come into contact with volatile iodine compounds. ALARA and Personnel Exposure Records/Reports At ISU, all authorized personnel will have a radiation dose history record, regardless of their monitoring requirement. All personnel monitoring records are maintained by EH&S. Personnel monitoring results are reviewed quarterly by EH&S radiation safety staff to assure that radiation doses are kept ALARA. An annual occupational dose report will be sent to any individual whose dose exceeds 100 mRem. Dose reports will be supplied to any participant at their request. EH&S will only release dose reports when a signed request is submitted by the participant. An email that can be verified by EH&S as being from the participant is acceptable. An individual will be notified by EH&S whenever current monitoring results exceed established ALARA limits. EH&S will meet with the individual to determine the cause of elevated dose, and will review work practices to identify methods to reduce exposure.
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