Section 3:  Personnel Monitoring

A. Occupational Dose Limits

The State of Tennessee requires monitoring of individuals' radiation exposure if it is expected that a person will receive a dose in excess of 10%. The annual occupational dose limits for an adult radiation worker are given in Table 1:

Table 1: Occupational Dose Limits for Adults
Description Dose Limit
Whole Body 5,000 mrem/yr (50 mSv/yr)
Skin 50,000 mrem/yr (500 mSv/yr)
Extremity 50,000 mrem/yr (500 mSv/yr)
Any organ other than the lens of the eye 50,000 mrem/yr (500 mSv/yr)
Lens of the eye 15,000 mrem/yr (150 mSv/yr)

The annual occupational dose limits for minors are 10% of the limits for adult radiation workers. Therefore, minors have a whole body occupational dose limit of 500 mrem/yr (5 mSv/yr). Radiation badges are required if an individual is expected to receive 10% of the applicable limit, for minors this corresponds to 50 mrem/yr (0.5 mSv/yr). All minors who work with sources of ionizing radiation or in a laboratory using radioactive material are require to wear a dosimeter.

The dose limit for an embryo/fetus of a declared pregnant woman is 500 mrem (5 mSv) for the entire gestation period and the dose should not exceed 50 mrem/month (0.5 mSv/month). These limits can only be enforced if the pregnancy is declared. A declared pregnant woman is defined as a woman who has voluntarily informed her employer in writing of her pregnancy and the estimated date of conception. Declaration forms and counseling are available from VEHS, the VEHS web site, or Occupational Health Services. The pregnancy declaration form must be submitted to Occupational Health Services.

Permanent copies of personnel dosimetry records are maintained by VEHS. Copies are also distributed monthly to the various departmental badge representatives.

B. Personnel Dosimeters

VEHS will issue radiation badges commensurate with the type of ionizing radiation being used. Radiation badges are issued to workers who are likely to exceed 10% of the occupational dose limits. Workers may work with radioactive material and not be issued a radiation badge. Radiation badges will be issue based on the following: 1) VEHS analysis of potential radiation exposure, 2) the type of radiation emitted from the radioactive material, 3) the quantity of radioactive material handled, and 4) the handling time. Badge applications may be obtained from VEHS, the VEHS web site, or the badge representative. Permanent records of personnel exposures are maintained by VEHS. Employees can review and discuss their radiation exposure records with VEHS staff.

C. Responsibilities for Personnel Dosimeter Users

  1. The badge reading is a legal record and must reflect occupational exposure only. Therefore, the badge shall be worn only by the person to whom it was assigned, and shall not be tampered with or experimentally irradiated, and shall not be used to measure any radiation exposure you may receive as a medical patient.
  2. Badges are distributed and collected by departmental badge representatives at the exchange frequency determined by the Radiation Safety Officer. It is your responsibility to exchange your badge on time with your badge representative.
  3. Radiation workers assigned a badge must have complete records of their occupational exposure for the current year, i.e. no "gaps" are allowed in their personnel dosimetry records. If a badge is lost, a replacement badge must be obtained from VEHS and a Missing Badge Report completed so that an estimated exposure may be assigned.
  4. Badges should be worn on chest, collar, or belt so as to indicate "whole body" exposure. If a lead apron is worn the badge should be worn at collar level outside the apron so that exposure to the head is monitored.
  5. Ring badges should be worn on the palm side of the hand to best monitor the exposure received from handling radionuclides. If wearing gloves to prevent contamination to the hands, the ring badge should be worn under the gloves.
  6. Badges should not be left near a source of heat. At the end of the work day badges should be left in a location where they will not be exposed to radiation or heat.
  7. Persons issued a dosimeter must wear it at all times when working with sources of ionizing radiation.

D. Bioassays

  1. Thyroid Monitoring Requirements for Unsealed Sources of Radioiodine

    Before handling quantities of radioiodine exceeding 10% of the values given in Table 2 an individual must have a baseline thyroid bioassay. A thyroid bioassay is required when an individual handles unsealed quantities of radioiodine that exceed those shown in Table 2. The thyroid bioassay must be performed within ten days after handling the indicated activity of 125I or 131I, or within 72 hours of handling the indicated activity of 123I.

    Table 2: Thyroid Bioassay Requirements
    Type of Operations Volatile Form Bound to Nonvolatile Agent
    Processes on open bench, with possible escape of iodine from process vessels 1 mCi (37 MBq) 10 mCi (370 MBq)
    Processes carried out in adequate fume hood 10 mCi (370 MBq) 100 mCi (3.7 GBq)

    Note: Quantities are considered to be the cumulative amount in processes handled by a worker during a 3 month period.

    Bioassay Requirements for Nuclear Medicine Personnel:

    Nuclear Medicine personnel directly involved in unsealed therapeutic radioiodine administration are required to have a thyroid bioassay within ten days after handling the radioiodine.


    Failure to comply will result in a termination of ordering privileges for the PI.

    Time and Location of Measurements:

    Call VEHS (2-2057) to schedule a thyroid bioassay appointment.

    Thyroid Action Levels:

    Thyroid activities in excess of 0.036 mCi (1330 kBq) of 123I, 0.0004 mCi (15 kBq) of 125I or 0.0003 mCi (11 kBq) of 131I requires an investigation of the operations involved and the implementation of corrective action. Repeat thyroid bioassays will be required.

  2. Tritium Bioassay Requirements

    Individuals involved in operations that utilize, at any one time, more than 100 mCi (3.7 GBq) of 3H in a non-contained form, other than metallic foil, shall have urine bioassays performed within one week following a single operation and at weekly intervals for continuing operations. The assay frequency for continuing operations may be reduced to monthly after the first calendar quarter, dependent upon initial results.

  3. Accidents

    Bioassays may be required if a person has been involved in a spill or other incident in which there may have been a significant intake of radioactive material. Bioassays may include urinalysis, analysis of other excreta such as fecal samples and nose wipes, whole body or thyroid counts.