Radiation and You

Radiation and You


Radioactive materials (also referred to as radioisotopes) and radiation producing machines (x-ray machines) are used in many laboratories at UC Davis. This work is authorized by a license granted to the University by the State of California, Department of Public Health. Various faculty members have been approved for work involving radiation by the Radiation Safety Committee.  The Office of Environmental Health and Safety (EH&S) assists the investigators in ensuring safe working conditions for students, staff, and faculty using these materials. Each approved faculty user is granted a "Radiation Use Authorization" (RUA) that specifies what materials or machines can be used and where, how, and who may use the sources of radiation.

The RUA holder, called a principal investigator (PI), is responsible for providing necessary specific training to those who work within the area and for maintaining a safe working environment. The P.I. is also responsible for ensuring that all individuals attend the required EH&S/Health Physics training courses. EH&S supports the PI's in this task by offering periodic training classes for new radiation users and retraining classes and internet exams for the radiation users in order to "brush up" on their knowledge of radioactive materials and handling techniques specific to the type of materials used.

This information is intended to provide basic information for University staff who do not work directly with radioactive materials, but who may need to enter areas where radioactive materials or radiation producing machines are used. Further information is available from the RUA holder, the Radiation Safety Manual, or by discussing your questions with a Health Physics staff member at EH&S (530-752-1493).

What is Radiation?

Radiation has become a household word. Radiation that is very low in energy is called non-ionizing radiation and includes heat, radio and television signals, light and microwaves. Radiation that is high enough in energy to cause ionization is called ionizing radiation and includes x-rays, gamma-rays, beta particles, alpha particles, and neutrons.

In this document the term radiation will refer only to ionizing radiation. Ionizing radiation comes from natural and human-made sources; it is not new, nor is it completely avoidable. Radiation comes from the sun, atmosphere, soil and water. Even our bodies contain radioactivity! Potassium-40, a naturally occurring radioisotope, becomes part of the body from the food we eat. We receive additional radiation from various human-made sources such as residual fall-out from previous above-ground nuclear weapons testing, from occupational sources, and, of course, from medical radiation.

The amount of radiation a person encounters is called "exposure." Some of this radiation exposure is absorbed by the body and is referred to as "radiation dose." Common units for measuring a person's exposure and dose to ionizing radiation are the "rem" and the "rad" respectively.

The fact that we have received and will continue to receive radiation from natural sources does not mean that radiation exposure cannot be minimized. Research tells us that any exposure to radiation has its risks. Currently, radiation protection professionals are debating radiation risks and limits of exposure.

Exposure to high levels of radiation is associated with an increased risk of cancer in later life. However, within the University setting, the amount of radioactive material generally used is small, and proper precautions reduce the risk of health effects to a negligible level. Although low radiation levels do not have zero risk, the risk is so low that no physical effects have ever been detected or demonstrated in humans. Nevertheless, all persons in an area that radioactive materials or x-ray producing machines are used should make a conscious effort to reduce radiation exposure as much as possible.

The Decaying Radioactive Atom

Matter is made up of millions of atoms. An atom is made up of a nucleus containing protons and neutrons orbited by electrons. In the atoms of a radioactive substance, the nucleus is unstable because it carries too many or too few neutrons. In order to become stable, bursts of energy are sent out from the nucleus as either alpha particles, beta particles, neutrons, or gamma rays. The time that it takes to lose one-half of the energy present is called the characteristic half-life of the radioisotope and can vary from seconds to millions of years. The radioisotope will continue to decay until it loses all of its excess energy and becomes "stable." X-rays (non-nuclear in origin) are produced when a target material is bombarded by high energy electrons in a machine or when electrons change orbits.

Radiation Protection

The first step you can take to protect yourself from radiation is to be able to identify an area where radiation is used or stored. The image on the right is the internationally recognized symbol for radiation. It is magenta or purple, on a yellow background. Signs with this symbol should be posted in all rooms that radioactive materials or radiation producing machines are used or stored. These rooms are considered "restricted" in the sense that only individuals who have a need to be there should enter. A sign the reads "Caution - High Radiation Area" indicates that a real radiation hazard may exist and physical barriers are present to prevent your unauthorized entrance.

Each specific location within the laboratory where radioactive materials are used or stored, such as a fume hood, refrigerator, glassware, laboratory apparatus, or waste container, will be properly identified by the radiation symbol. This identification system is intended to eliminate the possibility of your accidentally coming into contact with radioactive materials. Necessary shielding is also used to further reduce the possibility of any unnecessary exposure hazard. Radioactive waste is limited to specially marked containers and should never be present in the normal trash.

Personal Protection

There are three major ways you can protect yourself from the effects of external radiation exposure.

  1. Time - the less time you spend around radiation, the lower your radiation exposure.
  2. Distance - stay as far from the radioactive source as possible. Radiation intensity decreases rapidly with distance and is a very effective way of reducing exposure.
  3. Shielding - shielding can protect you against radiation. The appropriate shielding is used to reduce the radiation exposure rate.

People who work directly with the radioactive material (radiation workers) may also be evaluated for radiation exposure by the use of badges or finger rings, called dosimeters. These devices are used to measure radiation exposure. Radiation exposure limits to radiation workers and the general public have been established by the State of California and are adhered to by the University.

Radiation protection also requires that precautions be taken against accidentally getting radioactive material inside the body (internal radiation exposure). Both the laboratory staff and the Office of Environmental Health and Safety, Health Physics, routinely test all work areas where radioactive materials are used for radioactive contamination. In addition, there are some common sense rules that everyone in a sign-posted room must obey. These rules include no eating and drinking in the laboratories where radioactive materials are used or stored.  There is no smoking allowed in any laboratory at any time.  No edible material may be placed in a refrigerator or freezer used for storage of any hazardous materials including radioactive materials. If you handle glassware or other laboratory items that has been used with radioactive materials, disposable gloves are required. Observing these rules will safeguard against the possibility of unnecessary radiation exposure.


In the unlikely event that a spill of radioactive material should occur while you are in the laboratory, follow the directions given to you by the radiation workers that are present. If no one is present, close the area and immediately inform the PI (faculty) and/or nearby radiation worker. If no one is available to assist you, call 911 and inform the Police/Fire dispatch operator. They will know how to reach someone from the Office of Environmental Health and Safety at all hours.

Your Rights

Remember that you have the right to ask questions of the PI or EH&S. You are entitled by law to be informed of any radiation aspect in your work area, so do not be reluctant to ask.

Finally, should you become pregnant, it is recommended that you notify the PI and EH&S without delay. A developing child is more sensitive to radiation than an adult. Therefore, the exposure limit for the fetus is lower than the limit for occupational workers. You should obtain all the facts before continuing work with radiation.

April 2011