4. Radiation Exposure Policy

4.1. ALARA (As Low As Reasonably Achievable) Policy

UC Berkeley has a policy of preventing unnecessary radiation exposures to persons and the environment, and to keep any exposures as low as reasonably achievable (ALARA). ALARA attempts to maintain exposures to radiation at below the dose limits, consistent with the purpose for which the exposure is generated, but also taking into consideration the state of technology, the cost of the improvements needed to reduce the radiation exposure, and the benefits to public health and safety.

4.2. Occupational Doses

While the goal for radiation exposure is ALARA, in no case are occupational doses for radiation users permitted to exceed the CDPH limits specified in Table 1, below.

Table 1. Occupational Dose Limits (external and internal sources added together) in millirems per year

Category of Dose Equivalent Regulatory NRC/CDPH Limit UC Berkeley Administrative Guideline1
Whole body 5,000 mrem/yr 500 mrem/yr
(Eye) Lens 15,000 mrem/yr 1,500 mrem/yr
Skin or extremities (hands and forearms, feet and ankles) 50,000 mrem/yr 5,000 mrem/yr
Organs 50,000 mrem/yr 5,000 mrem/yr
Minors (<18 years of age) 500 mrem/yr 50 mrem/yr

1Administrative guidelines are dose equivalent recommendations adopted by the Radiation Safety Committee (RSC) for all UC Berkeley personnel. If these guidelines are exceeded, a review by the Radiation Safety staff is required to determine if additional safety measures are required. +The administrative guidelines are not intended to be absolute limits, but to provide guidelines for keeping exposures ALARA.

4.3. Public (Non-Occupational) Doses

Radiation exposure to members of the general public is considered “non-occupational” exposure. All activities must be done in a manner that limits the exposure of non-radiation users to the regulatory limits for members of the public specified in Table 2, below.


Category of Dose Equivalent Regulatory NRC/CDPH Limit
Annual limit/guideline for dose to any individual member of the public 100 mrem
Limit/guideline for dose to any individual member of the public in a single hour 2 mrem

4.4. Prenatal Radiation Exposure Policy

The NRC and the State of California regulate permissible radiation-exposure doses to an embryo or fetus over the course of the pregnancy of a worker receiving occupational radiation doses.

4.4.1. Declared Pregnant Worker

Special dose limits, risk options, and monitoring requirements exist for workers who declare their pregnancies. If the pregnant worker chooses to declare her pregnancy, she must provide EH&S with a written statement. A form which may be used for this purpose (or as a guideline for the information that should be provided) is available at the EH&S radiation safety website.

The decision to declare pregnancy is completely voluntary on the part of the worker. However, a woman who chooses not to declare her pregnancy is neither subject to, nor protected by the regulatory provisions for women who have declared their pregnancies. The dose limit to the embryo or fetus during the entire pregnancy of a declared pregnant worker is not to exceed 500 mrem. A woman who has declared her pregnancy may decide what level of risk to accept; she may choose a level of risk lower than the regulatory limit.

The RSO’s review of the declared pregnant woman’s potential exposures may result in work modifications and/or the assignment of special dosimetry.

4.4.2. Resources for Pregnant Workers

The NRC’s Regulatory Guide 8.13, “Instruction Concerning Prenatal Radiation Exposure,” as well as forms that may be used to declare pregnancy or to withdraw a previous declaration of pregnancy may be found on the EH&S website. Additionally, the campus RSO is available to answer any questions users may have. Upon request, all inquiries and information are kept strictly confidential.

4.5. External Radiation Dose

Personnel exposure monitoring must be provided if a person is likely to receive a radiation dose in excess of 10 percent of CDPH limits. Dosimetry is also required for individuals entering an area of “high” radiation (>100 mrem/hour).

4.5.1. Requirements

To determine if dosimetry is required or recommended, the RSO reviews the specific use(s) described on the RUA before work begins. Based on the RSO’s review, dosimetry requirements are determined and are indicated on the RUA. There are generally two types of external dosimetry:

  • Whole-body monitoring of external radiation exposure (usually by thermoluminescent dosimeter [TLD] or an equivalent badge)
  • Extremity monitoring (usually by ring dosimeter)

Dosimetry will be provided and processed only by vendors accredited by the National Voluntary Laboratory Accreditation Program (NVLAP).

4.5.2. Supplementary Dosimeters

In special cases specified in the RUA, supplementary dosimetry may be required and will be provided by the RST Dosimetry Coordinator.

4.5.3. Obtaining Initial Dosimeters or Temporary Replacement Dosimeters

You may contact the RST Dosimetry Coordinator to arrange a time when you can pick up the needed dosimeter(s). The Dosimetry Coordinator will provide a form to be submitted at the time of pick-up. The Dosimetry Coordinator will request an estimate of the dose received during the current year from prior work with radioactive materials or radiation and will attempt to obtain records of your cumulative occupational radiation dose.

4.5.4. Proper Use of Dosimeters

All users of external dosimeters should follow these requirements:

  • Wear the assigned dosimeter(s) whenever working with radiation or radioactive material at the locations specified on the RUA.
  • Wear monitors correctly: Whole-body badges are normally worn on the belt or at chest level. It is important that the badge be worn with the identification label facing out (rather than facing the body). The badge should not be covered while it is being worn (e.g., it should be worn on the outside of user lab coats). Extremity monitors (rings) are usually worn on a finger of the hand most used, with the detector facing the radiation source.
  • Store dosimeters away from sources of radiation and environmental extremes (e.g., extreme moisture or extreme heat).
  • Exchange and return dosimeters as soon as possible after the replacements arrive. If a replacement dosimeter fails to reach you on schedule, inform EH&S, but keep using the original dosimeter until you have obtained a replacement.
  • Contact EH&S promptly if you lose a dosimeter. EH&S will provide a replacement dosimeter and work with you to assess and document the radiation dose for the period covered by the lost dosimeter.
  • Use only the dosimetry that was provided to you. Never borrow a dosimeter assigned to anyone else and never loan anyone a dosimeter.
  • Never intentionally expose your dosimeter to radiation sources.
  • Promptly notify EH&S if you accidentally expose your dosimeter.

Please notify EH&S about any medical procedure (e.g. diagnostic or therapeutic administration of radionuclides) that could cause a dose to your dosimeter(s).

4.6. Internal Radiation Dose

Internal radiation dose occurs if radioactive material is inhaled, ingested, injected, absorbed through wounds, or absorbed through the skin. Use of radioactive materials creates risks of a material being spilled on the skin or taken into the body. Protective clothing and other measures must be used to prevent or reduce internal radiation dose.

The RSO reviews each RUA before work begins. One aspect of the RSO’s review is to determine the potential for internal exposure. The RSO determines what, if any, controls (such as use of a fume hood) may be required. The RSO determines the need for bioassays and notes the requirement on the RUA.

In some cases, individuals receive special monitoring (“bioassay”) to determine if there has been any internal dose. Bioassay is the analysis of radioactive materials in the body. Measurements are taken by a variety of methods, including directly counting the body or body parts (in vivo) or analyzing excreta (in vitro). Both methods measure the amount of radioactive materials in the body. In general, two types of routine bioassays are performed at UC Berkeley: (1) thyroid counts, for some users of significant quantities of radioiodine, and (2) urine assays, for other radionuclides. Other methods may be used when appropriate.

If an individual’s bioassay detects the presence of radioactive material (above what is naturally occurring), the RSO will assess the dose and suggest methods to reduce future uptakes.

4.7. Review of Doses

All internal/external exposure monitoring results are reviewed by the RSO to ensure that regulatory and campus limits are not exceeded and that exposures are consistent with ALARA. Any occupational exposures greater than the administrative guidelines of 10% of the legal limits requires investigation for accuracy and cause. These values are:

  • Whole-body doses ≥167 mrem in a dosimetry reporting period (typically a period of 4 months), and
  • Extremity doses ≥1667 mrem in a reporting period. If the reading is determined to be accurate, the review helps determine the cause and address the means to reduce future exposures.

4.7.1. Routine ALARA Exposure Reviews

The RST periodically review exposure results and RUA use conditions, and may suggest actions to keep exposures ALARA. Exposures measuring above applicable UC Berkeley administrative guidelines are investigated further.

4.7.2. Summary of Dose and Special ALARA Exposure Investigations

An individual’s internal and external doses are added together and recorded as the total effective dose equivalent. If any individual’s combined external and internal dose reaches or exceeds applicable UC Berkeley administrative guidelines, the RSO conducts a special ALARA exposure investigation.

4.7.3. CDPH Limits

In the case of known or suspected overexposures (exposures exceeding CDPH limits), the RSO notifies the CDPH. The RSO/RSC may recommend personnel undergo medical evaluation and/or treatment by a qualified physician.

4.8. Review and Distribution of Monitoring Results

At any time, personnel may request a summary report of doses received while working at UC Berkeley. To protect confidentiality, the request must be written and signed by the person asking for the report, and submitted to the RST for action. The EH&S RST provides annual reports to all individuals who received a measurable occupational dose and who are either on campus or who have left forwarding addresses.