[ RadSafe ] Airport Whole Body Scanner Risks

[Otto G. Raabe]

At 02:53 PM 11/22/2010, Brennan, Mike  (DOH) wrote:

>I don't know if this has been posted here yet or not, but here is a link
>to FDA's response to the UCSF concerns:
>www.whitehouse.gov/sites/default/files/microsites/ostp/fda-backscatter-response.pdf

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The important letter above to Dr. Holden from the Department of 
Health and Human Services lays out in detail the radiation dosimetry 
issues associated with the whole body x ray scanners. Please read it.

An important sentence on page 4 that I don't quite understand is "The 
dose to the skin from one screening would be approximately 0.56 uSv 
when the effective dose for that same screening would be 
approximately 0.25 uSv." The tissue weighting factor for skin is 
0.01, so this sentence makes no sense to me. However, the letter is 
clear that they like to use the "effective dose" in describing these 
exposures.

However, the use of a tissue weighting factor of 0.01 based on the 
atomic bomb survivor studies to calculate the either 56 urem or 25 
urem effective dose per screening to skin may not be appropriate. The 
high energy gamma radiation received by the atomic bomb survivors my 
not have the same biological effectiveness per unit of dose as weak x 
rays in the case of the skin. Also, cancer  promotion from weak x ray 
exposures may be more important than cancer induction in the case of the skin.

I presume that the actual absorbed dose to skin per screening is 5.6 
mrem or 2.5 mrem based on the information in the letter to Dr. 
Holden. Therefore, it is safe to assume that the skin absorbed dose 
per scan is a few mrem.

The main issue related to skin irradiation is skin cancer. Skin 
cancer including some life-threatening forms, have been clearly 
associated with ultraviolet light exposures. UV light is less 
energetic than x rays and we can presume that ionizing weak x rays 
are more effective than UV light in promoting skin cancer. The 
promotional effect of repeated skin x ray exposures at airports 
rather than the cancer initiation by x rays may be the most important 
issue for people with high risk of skin cancer. People from southern 
states where UV exposure is high and skin cancer is common might be 
more affected by repeated whole body skin exposures to x rays that others.

Comments please......

Otto

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Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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