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Discussion in 'Travel Security' started by rwoman, Feb 28, 2012.
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MSNBC: Controversial airport scanner are safe, report says
Take it for what you will..
You know, I have no real problems with those things, but then (OVERSHARE ALERT!!!) being naked has never been a big deal to me.
Just imagine how many miles you would be earning if you were being screened and flying that much.
the annual radiation dose limit is 5rem. it's 2.5-3x lower than that for where I work. 5rem=5000mrem. 5000/17000 = 0.294mrem per screening. that's not much, but i'm still opting out.
I'm guessing you work in a tree-friendly hilltop town in east TN, not too far from Knoxville?
The OIG report provides a bit more detail than the press summary. Several relevant quotes are posted below. Your 5rem number is an order of magnitude larger than the standard used for the machines.
NIST also confirmed in 2008 that the machines met the ANSI standard, as did Johns Hopkins University Applied Physics Lab, which seems to be the source of that 17,000 scans number:
The calculation was revised in 2010 to 1.46 urem per screening, so it's actually >17,000 scans in a year to hit the maximum-allowed-under-the-ANSI-standard 25mrem of exposure.
I wonder what OSHA says about safety for the TSA workers who are near the things all day every day.
I don't think IG's know much about radiation.
not far from knox, no, but not really hilltop
it's hour 9 of the work day, so i'm just goint to accept your rebutal. it's probably much more accurate than the 5 minutes i spent doing my own calc and summary.
One of the earlier indepedent measurements mentioned in the report included a measurement of exposure to the operator. It was measured at 0.68 microrem/scan. That report recommended the addition of wing shields to reduce the exposure to the operator. Those wing shields were added, and another independent test was run by a different entity. The exposure to the operator was measured at 0.02 microrem/scan. OSHA probably doesn't have much to say about it at all. That's 1.25 million scans per year for the operator to hit the 25mrem exposure level set by the ANSI standard--which is really low compared to the standards for professionals working at nuclear power plants and research facilities. Math check: 25mrem = 25,000 microrem, 25,000 microrem / .02 microrem/scan = 1.25 million scans.
Probably depends on the IG. In this case, they relied heavily on outside research. Their task wasn't, afterall, to determine if the scanners were safe, but to determine if TSA had taken proper steps to make that determination themselves. The DHS-IG seems comfortable saying that they did, based on review of research done by third parties.
I was thinking more about the name of the town than its actual geography.
Your calculation was good. I just think the standard used for the backscatter x-ray is a MUCH lower annual exposure level than is typically seen for professionals working in fields that expose them to radiation--or for people in areas affected by contamination of some sort. I'm surprised by how low the ANSI standard seems to be, quite honestly.
so 25mrem is the standard? that's proposterous!
Seems that way, which strikes me as a very low annual dosage relative to other standards--albeit those standards are for very different contexts.
it's ridiculous and laughable. i'm so ticked off i'm getting off of here. plus i have knee therapy to go to, now
They can declare whatever they want about radiation levels, the usage of these is embarrassing on many, many levels.
I have always been of the opinion that the machines are safe but that are a poor substitute for better policies.
You questionin' my manhood, mane???
Course they've defined a convenient test for themselves.
Here's another test: will the millions of scans being done by these machines result in additional cancer case? Yes/No?
Huh? What's the convenient test? There's really only one relevant test with regards to the use of such a machine: do a set of scans with a dosimeter in the machine, record results from dosimeter. The bottom line is that the machines were designed, built and tested to meet a particular standard set by a non-profit, non-governmental entity. It turns out that the standard is extremely conservative with respect to the amount of radiation dosage that is allowed on a per scan and annual basis. The machines easily satisfy those standards based on tests from several reputable indepedent groups. From my reading of various materials independent of the DHS-OIG report, the community has largely determined that dosages in this range are not significant enough to have any measurable affect on health or cancer rates. Actually, the dosage from this machine appears to be significantly less than the dosage you receive while on your flight. In fact, you'd have to be scanned 2,055 times to be exposed to the same dosage as a roundtrip from JFK to LAX.
Someone's got to take one for the team. Maybe a Presidential Medal of Freedom should be awarded as a reward for "an especially meritorious contribution to the security or national interests of the United States, world peace, cultural or other significant public or private endeavors"
Well, you have the miles and want to travel. Can you start arranging your travel so that you hit as many scanners and possible and let us know how it turns out?
I am afraid some of my comments here will make me ineligible for any sort of US government medal
The big problem is third-party audit capability of settings. As to the machines, I'll believe ionizing radiation is safe when my oncologist tells me so.
I, and every expert I have found who provides specific numbers, continue to maintain that if you are afraid of the cancer risks associated with the backscatter scanners, you should not be flying at all because you will receiving higher doses of radiation generally, and ionizing radiation specifically by flying at jet cruising altitude for any length of time than you will receive during a scan. From what I've read from numerous sources, including reputable, independent physicists and oncologists, is that the ionizing radiation exposure from one scan is equivalent to the dosage of something on the order of 2 minutes at 30,000 ft.
Double-check my math here, please:
17,000 screenings = annual radiation limit (per OP).
one screening = 2 minutes at 30k feet
17,000 screenings = annual limit = 17,000 * 2 mins = 34,000 mins = 566 hrs
So if I spend 566 hrs per year in that metal tube, I reach that annual radiation limit. That's "just" roughly 11 hrs per week (rounded, considering that not all flight minutes are at 30k ft etc.). I'd think there are consultants etc. out there that fly transcons back and forth every week.
So if my math is right... should they be concerned (without added radiation courtesy of the TSA)? Since their flying is perhaps unavoidable, would it not be reasonable to avoid additional radiation exposure that serves no good purpose?
(me, personally, I am flying way less than 566 hrs per year... and I am glad about it for many other reasons)
I'll check the math against some other numbers in the original OIG report and another source or two in a little bit, but I think the typical consultant clearly isn't the one to worry about with regards to flight exposure plus scanning exposure. It's the pilots and flight attendants that are getting the highest altitude-related dosage. There are several studies that do actually show some higher risk of cancer--particularly skin cancers, including melanoma, non-melanoma and basel cell cancers--amongst overseas/long-haul or other pole-centric airline pilots. I say it that way because one of the studies I found was specific to pilots with the various Nordic airlines. Those routes are exposed to the highest levels of cosmic radiation because they are closest to the poles and the amount of atmosphere through which cosmic radiation passes is lower at the poles. The increased risk is small, but it has shown up in several studies, all of which recommended further study due to the complicated nature of cancer generlaly, and skin cancer specifically--genetic predisposition, exposure to direct sun while at the beach, etc. all being significant factors.
OK, as I started to look back at some of the exposure numbers, I'm not sure this estimation of yours makes sense, and not because of anything you've done. The standard total dosage estimate for a roundtrip JFK-LAX-JFK is 3 mrem. The ANSI standard used when testing the backscatter scanners calls for a max annual dosage of 25mrem. So to put things back into the overall perspective of the scanner vs. flying in the first place, it takes ~17,000 scans to hit the annual dosage max called for by the ANSI standard--again, what appears to me to be a ridiculously conservative standard--compared to just 8 1/3 roundrips from JFK-LAX-JFK.
And I'm not even yet getting into the debate over whether linear no-threshold (LNT) models should be preffered over a different exposure risk models.