TSA and Backscatter radiation, follow up.
In the November 2010 edition of the Aegis Journal we discussed the issue of radiation emissions from TSA deployed backscatter Body Scanners at the airports in the United States. Now it seems they are emitting – in some cases more than 10 times the amount of radiations they are supposed to – attributed to a math error. Some of the stories we liked to illustrate the point are
The key to Due Diligence is not look for an answer that fits, but asking the right questions so one can seek the answer that is more correct than the others.
With questions in hand I went out to the Internet to read and read and stumble. Lucky I stumbled into Mr. Peter Rez, Professor Department of Physics at Arizona State University in Tempe, Arizona through his web page at
We had an email exchange of questions, answers. Professor Rez posses a very kind way of helping me to ask the right questions. This is the essence of due diligence… The following is a pastiche of the Q and A between via email.
Q) As it stands now, the numbers I have read is that there is a one in 20 million chance of getting cancer from one scan – about the same as being blown up by a terrorist. So the scanners are a push statistically in terms of saving lives and may not be worth the effort?
A) I think the probability of being killed by the terrorist is probably closer to 1 in 100 million. These events are so infrequent that it’s hard to derive meaningful numbers. As far as I can tell there have only been the 2 incidents (the 2 Chechen ladies) where a commercial aircraft was brought down by explosives in the passenger compartment. The shoe bomber and the crotch bomber wouldn’t have come close even if their charges had fully detonated.
Q) What is bubbling though my head is not the 1 in 20 million of getting cancer from one screen but what about those who travel often and may be screened regularly and often…
1) Frequent Flyers (I’ll go through 50 to 100 airport security checks per year – I have opted out all times except once.)
2) Pilots and Crew
3) Workers at the airport shops and restaurants
4) Reflection of, or leakage of, radiation to the TSA workers (if indeed this occurs.)
A) Pilots don’t have to go through, airport workers should have SIDA badges and not have to go through, but it is still issue with flight attendants.
Q) OK what about frequent flyers? Assuming a 1 in 20 million chance of contracting cancer from one scan but what if I go through a backscatter scanner 50 times, are my chances of cancer now 1 in 400K? If I do this for ten years are my chances for cancer now 1 in 40,000. Is this correct?
A) In principle you are right about the frequent fliers. It is believed that the effects of radiation doses are cumulative, but I’m not sure. The truth is that there is very little known about the effects of low levels of radiation. Though in principle radiation at any level can induce double stranded DNA breaks, there are also repair mechanisms in the cell that either fix these or kill off cells that can’t be repaired.
Q) On each and every scan radiation is emitted past the traveler and the backscatter device out into the screening area. It is reflected off the subject just as light would be. So, what about the real canary in a coalmine – the TSA backscatter lab mammals all daylong standing next to the machine?
A) According to the Johns Hopkins measurements the scatter dose at the position where the TSA person stands is 0.84 microrem (0.0084 microSv). Assuming 3 screenings per minute and 200 8 hr shifts a year means that they get a dose of 2.4 mSv. This is a factor of 10 greater than the administrative limit (the limit for members of the public) but below the limit for radiation workers. Maybe they should be so classified.
The high value of the scatter dose implies that their primary dose measurement must be wrong, and is probably closer to my estimate.
Bank to my rants…
I am not a scientist – I am a skeptic, actually even worse – a private investigator who specializes in due diligence, asset recovery and some IPCI issues. Thus, I see on a regular basis how very smart and skilled professionals get it (due diligence) massively wrong – because they have not learned how to ask the rights questions…
From the TSA, Homeland Security and the manufactures of the backscatter screening devices I hear familiar paternal tones of speech. Everything is fine, small chance, etc… which are the exact same tones the bakers, accountants and regulators gave to investors and the public about… Madoff, Alan Stanford, Long Term Capital Management, Enron, WorldCom…
These paternal tones remind me of the two weavers who sold a hapless vain Emperor a new suit of clothes that are invisible to those unfit for their positions, or because they are stupid, or incompetent. When the Emperor parades before his subjects in his new clothes, a child cries out, “But he isn’t wearing anything at all!” Thus, what I hear as an undertone to their assurances on these devices sounds more like… Go away you stupid and annoying public – you ignorant, foolish and scared member of the public, we know more and have just told you so. It has just has my spidey sense up…
Everything is “all right” is a conclusive statement – it is not an answer to the questions being posed.
Some independent, extensive – real world – tests need to be done, not only on the backscatter machines, but also on the type of radiation (micro millimeter) and the cumulative levels of radiation the TSA workers are receiving while standing next to them. As we have learned from history, the understanding of the science and its consequences are rarely as advanced as the science itself.
For those who opt out, be prepared for an extra ten minutes of very polite questions as to why your opted out, the TSA people correcting you on your questions about the radiation, and a thorough pat down. Be nice, courteous, and understand they have a job to do before you catch your flight.