Dose Units
         Before looking at occupational exposure, a discussion of the appropriate units for quantifying values is necessary.  The rad is the unit of absorbed dose.  It is a measure of radiation energy absorbed in any type of material: steel, wood, human tissue, etc.  The rad is a large unit therefore, the more common unit is the mrad (10^-3 rad). The rad has a corresponding SI unit, the gray (Gy).  The conversion factor is: 1 Gy = 100 rads.
         The rem is probably a unit that you are more familiar with.  The rem is the unit of dose equivalence.  Dose equivalence accounts for the effect on tissue of the various types of radiation.  A dose of x-rays, gamma rays or electrons produces a smaller amount of injury than an equal dose of alpha radiation, therefore, the use of a quality factor (QF) accounts for the difference in dose. The table at the left shows various radiation and their corresponding quality factors.  To calculate dose equivalence from absorbed dose, equation 3 is used.

For example, compare the dose equivalence of an absorbed dose of 30 mrad of gamma radiation to an absorbed dose of 30 mrad of alpha radiation.   The calculations show that the alpha dose equivalence would be 600 mrem while the gamma dose equivalence would be only 30 mrem. Since most of the radiation used at Emory is in the form of betas and gammas, 1 rad will be equal to 1 rem.  The corresponding SI unit of dose equivalence is the seivert (Sv).  The conversion factor is 1 Sv = 100 rem.
         From a radiation protection standpoint, the most important concern is the potential damage from radiation exposure and not necessarily the amount of energy absorbed.  For this reason, all personnel monitoring is determined in units of dose equivalence.  Therefore, all dosimetry reports will be reported in mrem.

Personnel Monitoring
         In order to measure occupational exposure, Emory utilizes different forms of personnel monitoring.  The following persons will be monitored:
    Adults who, in one year, are likely to receive a dose exceeding 10% of the annual occupational dose limit
of 5000 mrem
     Minors or pregnant women who, in one year, are likely to receive a dose exceeding 10% of their applicable
occupational dose limit of 500 mrem
     Any individual entering a high or very high radiation area.
        The monitoring devices will vary with the type of work that is being performed.  If an individual meets one of the above conditions, they will be issued a film or TLD whole body monitoring device which will be processed by a NAVLAP approved company on a monthly or quarterly basis.  Figure 10 shows a typical film badge used at Emory. The film badge will monitor exposure to gammas,x-rays and high energy betas but will not detect low energy betas of ³⁵S, ³H and ¹⁴C.  Individuals working routinely with >1mCi high energy beta, gamma or x-ray emitting radionuclides will be issued a ring badge.  In order to obtain a monitoring device, one should contact the Radiation Safety Office or your health physicist to fill out the necessary paperwork and obtain the required training.  The monitoring device should be worn while in the lab and should not be removed from the laboratory area since the purpose of the monitoring device is to measure occupational exposure.  The device should be stored with the control so as to correctly account for background.  Also, great care should be taken with the film badge to ensure that it is not accidentally washed in the washing machine or left on the dashboard of a car.  These practices could lead to false readings.  The badge should be worn where it will receive the greatest exposure.  If work is performed in the hood, the badge should be worn on the chest but if the work is done on a low bench, the badge should be worn at the waist.  Ring badges should be worn with the label facing in and on the inside of the glove so as to guard against contaminating the ring.  The TLD which is used to measure the exposure is behind the label and therefore should face where the greatest exposure occurs, i.e. the inside of your hand.
        The second form of personnel monitoring is through bioassay.  The following individuals will be monitored using bioassay techniques:
     Individuals performing iodinations.  Thyroid scans are required within 72 hours of the procedure or the next
working day following 72 hours.  Prior to the iodination procedure the individual should contact the Radiation Safety Office to schedule a pre-scan and reserve an air sampler for use during the procedure.
     Individuals using more than 8 mCi of ³H in one year.
     Individuals involved in accidents with either iodine or ³H.
        The thyroid bioassay is performed using an uptake probe which is a NaI detector placed near the thyroid to measure uptake.  The procedure takes approximately 10 minutes and is quite painless.  The ³H bioassay requires a urine sample which will be counted in the liquid scintillation counter.  Urine cups are available through Radiation Safety, just contact your health physicist.
        Personnel monitoring reports are reviewed monthly and quarterly by Radiation Safety.   They are then mailed to each lab for personnel to review exposures for the month and quarter, as shown on this typical Landauer report.  The following notes explain each item of interest in the report.
1. Type of record, specifies the portion of participant's body for which dose is given, e.g. whole body,  chest, etc.
2. Landauer dosimeter, if used; otherwise, method of determining the dose.
3. Radiation type and, in some cases, energy.
4. Exposure from your most recently exposed badges.
5. Quarter to date dose accumulation.
6. Year to date dose accumulation.
7. Refers to the beginning of continuous Landauer service for a given dosimeter.
8. Month and year in which an amendment to the dose was last made
9. Number of times a current year report was generated for a participant
10. Indicates that the dose for a particular badge was from a calculation given by customer, rather than  from a Landauer badge analysis.
11. Whole body exposures are carried for the person, rather than for individual  whole body badges.    Standard calculation protocol for multiply-badged personnel assigns the highest whole body badge  exposure to the person.  Lens of eye exposure is calculated from badge closest to the eye.
12. Comments on individual dosimeters are shown in the NOTES column or detailed below body of report.

ALARA Program
 The personnel monitoring is all a part of the ALARA program at Emory University.  ALARA stands for As Low As Reasonably Achievable and the program is as follows.  The ALARA program at Emory has been established based on the dose limits recommended by the National Council on Radiation Protection (NCRP) and adopted by the Nuclear Regulatory Commission and Agreement States.
Each level of management at Emory has a commitment to the ALARA program.  Pay special attention to the commitment of the radiation worker.  Also note the investigational limits keeping in mind the background levels of radiation for a reference point.
 

         MANAGEMENT through program review.

        RADIATION CONTROL COUNCIL and COMMITTEES I, II AND III through review of uses of x-ray
        and radioactive material studies prior to approval and review of quarterly exposure levels

        RADIATION SAFETY OFFICE through monthly, quarterly and annual review of all exposures,  presentation
        of ALARA Program in all orientation and refresher training and contact with radiation  workers.

        AUTHORIZED USERS through commitment to evaluate their procedures, properly train their  workers and
        express their commitment to maintaining exposures ALARA in their labs.

        RADIATION WORKERS through commitment to properly use personnel monitoring dosimeters,  protective
        clothing and shielding when necessary and to  perform instrument and wipe surveys in  a timely manner to
        detect unexpected sources of exposure or contamination.

OCCUPATION DOSE LIMITS

         SITE                LIMIT (mrem/yr)
         Whole Body            5000
         Lens of Eye        1    5000
         Extremities/Skin       50000
         Pregnant, Fetal        500 mrem/term

MONTHLY ALARA INVESTIGATIONAL LIMITS

         BADGE              LEVEL I
         Trunk of Body      400 mrem
         Exposure < Level I - No action
            Exposure > Level I - RSO notifies employee by mail to discuss preventive measures

QUARTERLY ALARA INVESTIGATIONAL LIMITS

         BADGE          LEVEL I (mrem)          LEVEL II (mrem)
         Trunk of Body   125                            375
         Extremities         1250                          3750
         Collar                400                            1200
             Exposure < Level I - No Action
             Exposure between Level I and Level II - Reported to RCC
             Exposure > Level II - Reported to RCC and employee and investigated by RSO

ANNUAL REPORT
 RSO will distribute cumulative exposure histories to all badge recipients yearly.

Pregnancy and Minors
         Since the law of Bergonie and Tribondeau was published in 1906, it has been known that the sensitivity of cells to radiation damage is related to their reproductive activity and inversely related to their degree of differentiation.  It follows that children could be expected to be more radiosensitive than adults, fetuses more radiosensitive than children and embryos even more radiosensitive.  For this reason, State of Georgia regulations place different limits on minors than on adult workers.  Specifically, it limits anyone under the age of 18 to exposure not exceeding 10% of the limit for adult workers.
        Since studies indicate that the embryo or fetus is more radiosensitive than an adult, particularly during the first three months after conception when a woman may not be aware that she is pregnant, the NCRP recommends that special precautions be taken to limit exposure when an occupationally exposed woman could be pregnant.  The NCRP has recommended that during the entire gestation period, the maximum permissible dose equivalent to the fetus from occupational exposure of the expectant mother should not exceed 500 mrem.  The level of exposure of laboratory workers rarely approach this limit and in most occupational exposures, the dose to the fetus is less than the dose to the mother.
        Included in this packet are the Emory Policy on Radiation and Pregnancy and the State of Georgia documentation entitled "Guide for Instruction Concerning Prenatal Radiation Exposure."  If you become pregnant, contact your health physicist or the Radiation Safety Office for information regarding declarations of pregnancy and fetal monitors.