Answer to Question #11618 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
Recently I discovered at my place of employment that the lead shielding was removed from an x-ray fluorescence (XRF) analyzer that is mounted to the wall next to my office. The XRF analyzer uses ionizing x-ray radiation to identify the elements in metals and other materials. I believe the unit was being used without its lead shielding for the past five years. When this was discovered, the shielding was replaced and I was given a personnel dosimeter. My dosimeter readings were higher than the dosimeter readings of the people in the XRF room prior to the replacement of the lead shielding. I have been terribly ill with immunity issues, loss of hair, and stomach problems. My doctors are concerned about the past exposure. Could this chronic exposure to the ionizing radiation be contributing to my health issues?
Only a medical professional can tell if your chronic exposure to the unshielded XRF analyzer caused the symptoms you listed. However, I think this is unlikely, because the symptoms you describe have been seen only after a very large radiation exposure in a very short period of time. Typically it takes 1,000 to 10,000 millisieverts (mSv), delivered in a few hours or days, to see the symptoms you described. This information comes from the survivors of Hiroshima and Nagasaki, a handful of radiation exposure accidents, and a few cancer treatments using radiation.
To put this in perspective, the average person in the United States gets 3 mSv per year from natural background radiation. XRF devices are regulated by the U.S. Food and Drug Administration (FDA) to emit a maximum of 0.005 mSv per hour at 5 centimeters (cm) from the device. Sitting 1.8 meters (m) away from an approved XRF device, operating full-time for 2,000 hours a year, would give a dose of less than 0.008 mSv per year.
An additional concern may be the removal of installed lead shielding by an unauthorized person. It needs to be determined if the removal met state and/or federal regulations. Your facility's radiation safety officer and your management may need to do a dose reconstruction for the people working with or around the XRF device, with and without the lead shielding. Your facility may need to report this situation to a radiation-control regulatory authority. If you don't have a state radiation-control regulator, the FDA regulates x-ray producing machines, like the XRF analyzer.
Determining how much radiation exposure you got from the unshielded and the shielded XRF analyzer requires a detailed dose reconstruction. To do this the following information is required:
- The radiation dose rate from the XRF analyzer, towards your office, at a known distance, both with and without the lead shielding in place.
- The energy spectrum of the x rays from the XRF analyzer, because lower energy rays are easier to shield.
- The typical distances you were from the XRF analyzer during the work day.
- The time you spent at the various distances from the XRF analyzer.
- The physical characteristics (this includes each material's composition, density, and thickness) of any shielding between the XRF analyzer and you, including the wall materials, XRF device housing, and lead shielding.
- The hours of operation of the XRF analyzer during the year, while you were working, both with and without the lead shielding in place.
Until this information is gathered, your radiation exposure is unknown. The XRF analyzer manufacturer and/or the XRF analyzer technical manual may have some of the information for items 1 and 2.
Most XRF units operate in the very low x-ray-energy range, and their x rays are easily shielded, even by a Sheetrock wall. Also, most XRF units do not have manufacturer-installed lead shielding that is removable.
John Hageman, CHP