Please note that this web page was written for users of analytical X-ray instrument in the University of Oklahoma Small Molecule Crystallography Laboratory. This page and its author offer no comments on issues related to medical X rays.
X-Ray Laboratory Safety
Table of Contents
- Possible Health Effects
- Reducing Exposure, ALARA
- Monitoring Radiation Exposure
- Electrical Hazard
- Safety Procedures
- Emergency Procedures
- Selected X-ray Safety Web Sites
X-Ray radiation is a form of ionization radiation that is potentially very hazardous. The most intense and therefore dangerous part of the instrument is the path of the incident X-ray beam. Thus care should always be exercised to know the expected path of the incident beam. Scattered radiation poses a much smaller health risk to the researcher because of its reduced intensity.
There are several properties of X rays that make this type of radiation particularly dangerous to use in the laboratory. X-Ray radiation cannot be sensed by a human! Some people feel a tingling sensation on their skin when they are around X rays. They are not feeling the X-ray beams, but rather they are feeling charged air particles produced by the interaction of the ionizing X rays with air. If you ever feel a tingling sensation when working around any analytical X ray instrument, immediately turn off the instrument and contact the Radiation Safety Office and Crystallography Lab manager. Since only some people feel this tingling sensation, do not assume that if the sensation is not present, that the instrument cannot hurt you. Please note that the safety shutter on the instrument is interlocked to the cabinet doors so that if the door is opened, the shutters will close.
Care should be taken when using any analytical X-ray instrument. Never put any part of your body in the expected path of the main beam. Avoid being around the X ray tube housing and main beam path as much as possible. Keep the enclosure doors closed whenever possible.
Although X-ray instruments have the potential to be dangerous, when used properly, modern diffraction X-ray instruments pose few risks to careful users. The manufacture and use of analytical X-ray instruments is regulated by both federal and state governments. Current regulations require that a variety of safety devices be built into X-ray instruments that make it very difficult for anyone to even accidentally expose herself or himself to the dangerous incident X-ray beam. The design of the instruments limits even accidental exposures to the hands, arms, and facial areas. Generally, the types of radiation used in diffraction instruments (primarily Mo and Cu Kα radiation) are considered soft or low energy radiation. Unlike medical X rays, these types of soft radiation generally will not penetrate more than 2-4 cm into the body.
Possible Health Effects
Health effects of exposure to X-ray radiation come in two general types, direct or indirect. X Rays are thought to create radicals in exposed cells of your body that may break or modify chemical bonds within critical biological molecules. As a result (1) cells may be injured or damaged, although many cells repair themselves, resulting in no residual damage, (2) cells may die, which millions of body cells do every day and are replaced in a normal biological process, (3) or cells may incorrectly repair themselves resulting in a biophysical change. Finally, X rays may pass through the body with no interaction.
Factors that determine biological effects:
- Dose rate
- Total dose received
- Energy of the radiation
- Area of the body exposed
- Individual sensitivity
- Cell sensitivity
- Most sensitive tissues: Blood-forming organs, reproductive organs, digestive organs
- Least sensitive tissues: Nervous system, muscle and connective tissues
To date there have been few, significant accidental exposures in X-ray diffraction labs, and the physical ailments from these accidents have been relatively minor. However in X-ray fluorescence labs, a number of rather serious injuries have occurred. Because of the soft nature of radiation used in a diffraction lab, accidental exposure to X-ray radiation will usually cause damage only to the skin and possibly bones near the surface of the body. Depending on the nature and extent of exposure some or all of the following medical problems may ensue.
Often at the time of exposure, little or no pain is felt. However, 1-3 hours later, a first degree burn forms on the skin and a dull pain settles in all exposed tissues. Sometimes this is followed by swelling that turns into blisters that finally open and do not seem to heal over. In extreme cases, skin grafts and/or amputation may be required. Exposure of soft X rays to the eyes may cause permanent cataracts to form. Because of the possibility of cataracts forming, it is recommended that glasses be worn in an X-ray diffraction lab whenever instruments are modified or aligned.
As with all types of ionizing radiation, X rays cause the most damage to rapidly growing, undifferentiated cells. Thus, women that are pregnant or suspect that they may be pregnant, should take special care to protect their fetus, especially during the first trimester. Women that are pregnant or suspect that they may be pregnant and wish to avoid all lab exposure should contact the Crystallography Lab manager in order to make arrangements to get data collected by someone else during the term of their pregnancy.
In Oklahoma, radiation workers are allowed to receive the following occupational exposures without limiting the activities of the workers.
- Total effictive dose equivalent from a single event. 5,000 mrem
- Cummulative dose equivalent limits:
- Lense of eye 15,000 mrem, NRC & State DEQ
- Lense of eye 5,000 mrem, State Dept. of Health
- All others 50,000 mrem
Reducing Exposure, ALARA
The University of Oklahoma is committed to the goal of keeping occupational doses and public doses As Low As Reasonably Achievable, ALARA. This goal serves as the overall controlling aim of radiation safety, and commits all users of radiation sources to the principle that all unnecessary exposure is to be avoided. Also, where potential or real exposures are unavoidable, every reasonable effort should be made to reduce those exposures.
There are three general rules to reduce a person's exposure to any type of ionizing radiation.
Reduce the time you are exposed to the radiation source.
Increase the distance between yourself and the radiation source.
Increase shielding between yourself and the radiation source.
The ALARA rules are achieved in a diffraction lab primarily by the design of the instrument itself. For example, the protective enclosure is designed to stop all of the incident and scattered radiation from leaving the cabinet. When the enclosure is opened, the X-ray shutter must close. If any of the warning lamps that indicate when X rays are being generated should burn out, the safety shutter will close. If any of the lamps that indicate that the shutter is open should burn out, then the shutter will not open. The beam stop reduces the exposed path of the incident beam.
ALARA goals are also achieved by the researcher practicing safe techniques when using the instrument. As noted above, the user should keep all parts of their body out of the expected main beam path at all times, especially when placing a sample in the instrument or removing a sample from the instrument. When the safety enclosure is opened, the user should keep as far from the X-ray source as practical. Finally, the cabinet doors should be kept closed whenever possible.
Monitoring Radiation Exposure
Personal radiation detection devices (Luxel Aluminum Oxide or Thermo-Luminescence Dosimeters - TLD badges) are used to monitor the radiation dose that a wearer may have received from an exposure, but these devices offer no additional protection to the wearer. These devices measure exposure in only a small area of the body. The chances of these devices being located in an area of the body that is exposed is very small. Thus the use of these devices is discontinued in the crystallography lab.
Another serious hazard from an X-ray diffraction instrument is electrical shock. The X-ray generator is a highly-regulated DC power supply that operates at an applied voltage of 40 to 50 kV in order to achieve an optimum flux of X rays. Also, the power supply that feeds the detector operates at about 1 kV. These power supplies should only be serviced by trained electrical engineers. If any object should fall under the generator cabinet, ask the Crystallography Lab staff to help you retrieve the object--do not go after the object by yourself.
Also note that the X-ray generator has several large capacitors. Even when the instrument is turned off, these capacitors store sufficient power to injure and possibly kill a person. All work on any X-ray generator should be done only by personnel trained in high-voltage electronics.
All users of the Small Molecule Crystallography Lab instrument must first
authorized users by completing the requirements of the OU
Radiation Safety Office. In addition, users must follow these additional rules.
Know the expected path of the main X-ray beam. Always keep all parts of your body outside of this path.
Whenever possible, keep the safety doors to the instrument closed and latched.
No unauthorized personnel may defeat or override any safety feature on the X-ray generators, the safety enclosures, or the goniometers including the collimators, tube shields, and shutters without the permission of the lab manager and the OU Radiation Safety Office.
No user may employ any power or hand tool on any part of the goniometer, detector, or low temperature device without express approval from the lab manager. The single exception to this rule involves the use of specific wrenches to adjust the goniometer head to position the sample in the center of the goniometer.
All actual or suspected X-ray exposures of any person should be handled in the following manner.
Medical emergencies must be treated by physicians at Norman Regional Hospital or Goddard Health Sciences Center. Call 911 for emergency transport.
If the instrument malfunctions, depress one of the red
X-RAY OFF buttons on
either side of the instrument. If time permits, tape a message to the front of the
INSTRUMENT PROBLEM and include your name, the date
and your telephone number. Report the incident to the University of Oklahoma
Radiation Safety Officer, George MacDurmon (or Casey Schmitz) at 271-6121 and
to the lab manager.
Small electrical fires may be put out by using the fire extinguisher located
in the entrance to the lab. Larger fires and medical emergencies should
be handled by calling 911. Notify others in the building of fires by using one of the fire
alarm pull stations near the exits of the building. In the case of large room fires or major
water leaks, be sure to turn off the X-ray generator by pressing either of the red
buttons on the front of the instrument. Be sure to contact the Crystallography
Lab manager about any lab-related problem.