Answer to Question #406 Submitted to "Ask the Experts"

Q

I'm about three weeks pregnant and I work in a cardiac catheterization laboratory. I work next to the physician during the procedures. I do wear my lead aprons all the time. My radiation badges usually read about 50 mrem per month. Is there anything I should be concerned about?

A

Excellent question. It so often happens that a pregnant employee is working in an area where fluoroscopy is being used and this question comes up. Before I get into a lot of detail, I don't believe there is any need for concern based on the information you've provided. I'm glad you did provide the amount of radiation your badge is measuring each month. It's very helpful. Let's start with that information. Since a radiation badge should be worn at the collar level outside the lead apron, I'm going to assume that is the location you've been wearing it. There are a couple of lead equivalent thicknesses of aprons: 0.5 mm and 0.25 mm. You can look at the tag on the apron you've been wearing to get this information. The 0.5 mm lead apron will attenuate about 97-98 percent of 100 keV x rays. The 0.25 mm apron will attenuate about 94-95 percent of 100 keV x rays. To be conservative, let's assume you've been wearing a 0.25 mm lead equivalent apron. If your radiation badge indicates an exposure of 50 mrem per month outside the apron, your abdomen underneath the apron would be receiving 50 mrem x 5 percent or about 2.5 mrem. Over the course of gestation this would be 2.5 mrem/mo. x 9 mo. = 22.5 mrem. This is very low and quite conservative because your abdominal tissue will also offer protection for the fetus from any x rays that penetrate the lead apron. The allowable level of exposure for the fetus of an occupationally exposed individual is 500 mrem in 9 months. Your exposure is well below this. But what does that 500 mrem really mean? Well, it's an amount of exposure considered "safe" because it is set at a level that is 10 times less than the lowest amount of radiation known to cause fetal effects—that dose is 5000 mrem. So, you don't need to be concerned with radiation exposure at the levels you're currently receiving. It is important though, and I'm glad you're already doing it, to keep track of your badge readings to make sure there are no significant deviations from what you normally receive.

Kelly Classic
Certified Medical Health Physicist