Dear Bureaupat,

How much radiation are we receiving in our bodies as we pass through the security x-ray machines every day as we enter our Federal Building? I'm worried that over time, we may be accumulating damaging radiation. Are the machines safe?

Dear Radioactive,

As a federal employee, you know the extent to which national security has become a top federal priority, especially since the September 11, 2001 terrorist attacks.

Entry into federal buildings has completely changed and you can't get access these days without passing through checkpoints of armed guards and advanced screening devices. We should be thankful that we don't have to take off our shoes too... Oops, I hope I didn't just jinx us!

Getting serious for a second, the intense scanning of federal personnel and their articles clearly has raised concerns in the minds of some about radiation exposure from these security measures. If you count yourself among the worried or skeptical, I think your concerns will be alleviated after you hear more information.

The cabinet x-ray system used to scan your personal items is an enclosed system that uses shielding to keep radiation from exiting the walls of the unit. There is a strict standard on the amount of radiation that a cabinet x-ray system is allowed to emit. In addition, the standard also requires safety features that include warning lights, warning labels, and locks.

The Food and Drug Administration (FDA) has responsibility for assuring manufacturers produce x-ray systems that do not pose a radiation safety hazard and requires that all machines be properly calibrated and maintained.

So is it safe to stand or walk near a cabinet x-ray system while it is producing x-rays?

Yes. Manufacturers are required to certify that their products meet the Federal radiation safety performance standard for cabinet x-ray systems. Specifically, the standard requires that the radiation emitted from a cabinet x-ray system not exceed an exposure of 0.5 milliroentgens in one hour at any point five centimeters from the external surface. Most cabinet x-ray systems emit less than this limit.

For comparison, the average person in the United States receives a dose of about 360 millirem of radiation per year from background radiation. (Note: 1 milliroentgen of exposure to x-rays will result in approximately 1 millirem of dose.

Not to make this too scientific but here are some needed definitions:

• Dose means the quantity of radiation or energy absorbed.
• Roentgen (R) is a unit of exposure of ionizing radiation and indicates the strength of the ionizing radiation. One Roentgen is the amount of x-ray needed to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimeter of dry air under standard conditions.
• Roentgen Equivalent Man (rem) is the basic unit of equivalent dose, and relates the absorbed dose in human tissue to the biological effect of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose.

By the way, "background radiation" is radiation that is always present in the environment. Eighty percent of that exposure comes from natural sources: radon gas, the human body, outer space, rocks, and soil. The remaining 20 percent comes from man-made radiation sources, primarily medical x-rays.

One further note: It is also safe for pregnant women to stand or walk near a cabinet x-ray system while it is producing x-rays. The limit on radiation emission established by the performance standard is sufficiently restrictive that there is no additional hazard for specific populations such as children or pregnant women.

So that glow your colleagues are sporting every morning? — It's obviously just the thrill of starting another day of work inside the federal government!

Yours in Gov,

Bureaupat

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