Occupational Exposure Limits

  1. The annual limit for occupational workers is the more limiting of:
    a. The total effective dose equivalent = 5,000 millirem (0.05 Sv); or 
    b. The sum of the deep dose equivalent and the committed dose equivalent to any individual organ or tissue (other than the lens of the eye) = 50,000 millirem (0.5 Sv).
  2. The annual limits to the lens of the eye, to the skin, and to the extremities are:
    a. Eye dose equivalent = 15,000 millirem (0.15 Sv)
    b. A shallow dose equivalent = 50,000 millirem (0.5 Sv)

Non-Occupational Exposure Limits (Members of the Public)

Each user of radioactive material shall conduct operations so that:

  1. The dose in any unrestricted area from external sources does not exceed 2 millirem (0.02 mSv) in any one hour.
  2. The total effective dose equivalent to individual members of the public from a licensed operation, exclusive of the dose contribution from a licensee’s disposal of radioactive material into sanitary sewerage, does not exceed 100 millirem (1 mSv) in any year.

Declared Pregnant Workers Exposure Limits

The dose limit to an embryo/fetus during the entire pregnancy due to occupational exposure of a declared pregnant woman is 500 millirem (5 mSv). Care shall be taken so that no more than 50 millirem (0.5 mSv) be received during any one month during a declared pregnancy. Furthermore, efforts shall be made to avoid substantial variation above uniform monthly exposure rate to a declared pregnant woman (see Appendix B of the Radiation Safety Manual for additional information). 

If the pregnant woman has not notified the Division of Research Safety (DRS) of her estimated date of conception, the dose to the fetus shall not exceed 50 millirem (0.5 mSv) per month during the remainder of the pregnancy.

If, by the time the woman informs DRS of the estimated date of conception, the dose to the embryo/fetus has exceeded 450 millirem (4.5 mSv), the limit for the remainder of the pregnancy shall be 50 millirem (0.5 mSv).

Exposure Limits for Minors

The annual occupational dose limits for minors are 10 percent of the annual occupational limits specified for adult workers in Section 7.1 of the Radiation Safety Manual

When Dosimetry Is Required

The Illinois Emergency Management Agency (IEMA) requires dosimetry for the following:

  1. Adults likely to receive in one year from sources external to the body a dose in excess of 10 percent of the occupational exposure limits (Section 7.1 of the Radiation Safety Manual).
  2. Minors and declared pregnant women likely to receive in one year from sources external to the body a dose in excess of 10 percent of the applicable limits (Section 7.3 or Section 7.4 of the Radiation Safety Manual).
  3. Individuals entering a high or very high radiation area.

DRS assigns dosimetry when certain quantities and nuclides are used. Specifically, the use of >10 mCi of P-32 requires the user to wear both an extremity (commonly referred to as a “ring”) and a whole-body dosimeter. At usage levels ≤10 mCi of P-32, dose assessments will be performed to evaluate the need for dosimetry.

DRS evaluates the use of dosimetry with other radionuclides and quantities on a case-by-case basis.  

Personnel Dosimetry

The use and type of personnel dosimetry is determined by the activities and functions the individual performs. By regulation, any person who receives or is likely to receive more than 10 percent of the maximum permissible dose or who enters a high radiation area must be provided with and must wear personnel monitoring devices.

To obtain dosimetry, complete a Dosimetry Request Form (see Appendix E of the Radiation Safety Manual) and return it to DRS.  Upon receipt, DRS personnel initiate the request process with the dosimetry vendor. The turnaround time is typically one week for a rush order. Therefore, ensure dosimetry requests are made in advance of the need to work with radioactive materials. Note that dosimetry is not issued for individuals working with weak beta-emitting radionuclides such as H-3, C-14, S-35. 

Whole body dosimeters, or badges, monitor exposure to the whole body and should be worn between the neck and the waist, usually on the front of the body.  

Finger ring dosimeters monitor radiation exposure to the hands and fingers. These dosimeters may be worn on any finger and should normally face the palm side of the hand.  Finger rings must be worn under gloves to prevent them from becoming contaminated.

Every person with assigned dosimetry must wear the dosimetry when working with sources of ionizing radiation.  

The dosimeter reading is the legal record of an individual’s occupational radiation exposure. Therefore, dosimetry shall be worn only by the individual to whom it is assigned, shall not be tampered with or experimentally irradiated, and shall not be used to measure radiation exposure received as a medical patient.  

When not being worn, dosimeters must be stored in a location where they will not be exposed to radiation.

Dosimeters are collected monthly or quarterly by DRS personnel and sent to a vendor for processing.  Dosimeters must be made available for this exchange to occur.

If a dosimeter is lost, discontinue radiation-related activities and contact DRS. Individuals who have lost their dosimetry must provide information to DRS personnel so that an assessment of their radiation exposure can be performed. DRS will order a replacement dosimeter.

Declaration of Pregnancy

The increased sensitivity of rapidly dividing cells makes the human embryo and fetus particularly susceptible to injury from exposure to ionizing radiation. For this reason, regulations require that exposure to the fetus during the gestation period not exceed 500 millirem. Recommended reading for pregnant female radiation workers is provided in Appendix E of the Radiation Safety Manual.

Any radiation worker who is pregnant or believes that she may be pregnant should contact DRS and review the recommended reading in Appendix E of the Radiation Safety Manual. All inquiries will be confidential. The individual must complete a Declaration of Pregnancy Form. If a written declaration of pregnancy is not submitted, then the worker’s dose continues to be controlled under the normal dose limits for radiation workers.

For the type of radiation work performed at the U of I, it is rarely necessary to recommend reassignment or changes to job duties to reduce exposure.

Declaration of Pregnancy Form

Found in Appendix E of the Radiation Safety Manual

Recommended Reading for Pregnant Female Radiation Workers

Found in Appendix E of the Radiation Safety Manual


Bioassays, analyses, or evaluations of materials excreted or removed from the body are required to determine types, concentrations, quantities, or locations of personal uptake. A baseline (before first use) bioassay and another within 24-72 hours following each use of the quantities specified is required. Thyroid bioassays are performed using a hand-held scintillation probe and survey meter. Tritium bioassays are performed by condensing water from exhaled air. DRS personnel perform bioassays at the following location if other arrangements are not made:

Environmental Health and Safety Building
101 South Gregory Street, Urbana

Users of unbound radioactive iodine (typically I-125 or I-131) in quantities of ≥1 mCi on a bench top or in quantities ≥10 mCi in a fume hood require thyroid bioassays. These bioassays are performed on a walk-in basis during business hours unless previous arrangements are made. Tritium bioassays are required when a person uses >100 mCi of H-3 without using a fume hood. DRS must be notified at least 24 hours in advance for this and the baseline tritium bioassay.

Additional bioassays may be required for personnel on a case-by-case basis as determined by DRS.

Personnel Exposure Records

DRS maintains exposure records for all monitored personnel. Annual reports of exposure are sent to personnel required to wear dosimetry in accordance with Section 7.5 of the Radiation Safety Manual

At the request of a worker, DRS shall furnish his or her exposure report. The report is furnished within 30 days from the time the request is made, within 30 days of termination of employment, or within 30 days after the individual’s dose has been determined, whichever is later.

ALARA (As Low As Reasonably Achievable)

The university is committed to maintaining radiation exposures to faculty, staff, students, and the public resulting from the use of radiation sources in teaching and research As Low As Reasonably Achievable (ALARA). The Radiation and Laser Safety Committee and DRS advise and assist faculty, staff, and students in all matters regarding radiation safety. The committee recommends to the campus administration, through DRS, policies and procedures for maintaining ALARA radiation exposures through the safe handling, storage, use, transport and disposal of radiation sources. It will assist in the interpretation of the rules and regulations of the U.S. Nuclear Regulatory Commission, the IEMA, the U.S. Environmental Protection Agency, the U.S. Center for Devices and Radiological Health, and others that pertain to protection against radiation.

Sources of radiation include materials or equipment that are capable of emitting either ionizing or non-ionizing radiation. Ionizing radiation sources include radioactive materials, nuclear reactors, particle accelerators, X-ray machines, and electron microscopes. Non-ionizing radiation sources include lasers, high-intensity sources of ultraviolet light, microwave transmitters and other devices that produce high intensity radio-frequency radiation. Both types of radiation are of concern and are under the purview of the Radiation and Laser Safety Committee and DRS.

Exposure Reduction Practices

Use the concepts of time, distance, and shielding to minimize personnel exposure.

To prevent accidental entry of radioactive materials into the body, high standards of cleanliness and good housekeeping must be maintained in all laboratories where radioactive material is present. Wash hands and arms thoroughly before handling any object that goes into the mouth, nose or eyes (e.g., cosmetics, foods, contact lenses). Keep fingernails short and clean. Never pipette by mouth; instead use rubber bulbs, syringes or mechanical devices.

Clean up minor spills immediately. For major spills, follow emergency procedures.

Visitors are not allowed into the lab without approval of the principal investigators . 

Smoking, eating, drinking, and applying cosmetics in radioisotope laboratories are not allowed. Refrigerators shall not be used jointly for foods and radioactive materials.

For new procedures and new personnel, one or more trial runs beforehand with non-radioactive materials are recommended to test the effectiveness of procedures, training, and equipment.

Use appropriate shielding. Do not use lead shielding for beta-emitting nuclides.

Always use gloves when handling unsealed radioactive materials. Wear protective clothing (lab coats, eye protection, shoe covers) as needed. Do not work with unsealed radioactive materials if there is a break in the skin below the wrist.

Tritium users: Change gloves every hour when working with 50 mCi or more.

Whenever possible, operations with radioactive materials should be conducted in a hood, dry box, or some other type of closed system. Operations with materials susceptible to atmospheric distribution, such as boiling, evaporating, distilling, or ashing, must be done in a fume hood with airflow of approximately 100 linear feet per minute. Fume hoods in radioactive material laboratories are checked periodically for airflow and the proper sash height is indicated on the fume hood. Work with nuclides with half-lives of more than a few hours should be done over a containment to prevent the spread of contamination in the event of a spill. Work with radioactive materials in powder form should be done in an enclosed system.

Table and bench tops should be of a non-porous, chemical-resistant material. Working surfaces should be covered with absorbent paper regardless of the type of surface. 

When work is completed each user should clean up his/her own work area and arrange for disposition of all radioactive materials and equipment.

Vacuum pumps used in systems containing radioisotopes should be used in fume hoods with proper flow rates. 

External exhaust stacks must not be vented towards windows or building air intake vents. 

Laboratories shall provide non-leaking radioactive waste containers bearing the words "Caution Radioactive Materials." 

University cleaning crews are permitted to clean floors and windows only. Laboratory personnel are responsible for the remainder of the housekeeping. 

Repairs on potentially radioactive systems such as sink drains and fume hoods should not be undertaken unless DRS personnel have released the area or item from radiological

Last Update: 7/18/2018
Updated By: tmcgill