

Leading scientists say backscatter X-ray may be far more dangerous than thought - zacharyvoase
http://www.npr.org/assets/news/2010/05/17/concern.pdf

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AngryParsley
That letter is from April. The FDA wrote a response last month:
[http://www.fda.gov/Radiation-
EmittingProducts/RadiationEmitt...](http://www.fda.gov/Radiation-
EmittingProducts/RadiationEmittingProductsandProcedures/SecuritySystems/ucm231857.htm)

 _The recommended limit for annual dose to the skin for the general public is
50,000 µSv. The dose to the skin from one screening would be approximately
0.56 µSv when the effective dose for that same screening would be 0.25 µSv.
Therefore the dose to skin for the example screening is at least 89,000 times
lower than the annual limit._

Most of the concerns in the letter are addressed. It's easy to spread FUD, but
these devices are likely safe. Other organizations and governments have
evaluated their safety independently.

~~~
tomjen3
It does not matter if they are safe (which they aren't), it matters that they
be removed.

A little fud now and then is a good thing.

~~~
chroma
If you're willing to say anything to make the other side look bad, why should
anyone give you credence?

~~~
tomjen3
There is a big difference between a little fud and being willing to say
anything. These machines have been called, by a reputable scientist, as
potentially very dangerous. I see no problem making sure everybody knows that
they are dangerous, nor do I particular care to present both sides of the
argument.

~~~
AngryParsley
_These machines have been called, by a reputable scientist, as potentially
very dangerous._

And 1 out of 5 dentists recommend sugar gum. There are enough scientists in
the world that you can always find one who shares your belief. Scientific
consensus is a much more reliable indicator of correct beliefs.

 _...nor do I particular care to present both sides of the argument._

I can think of half a dozen pieces of evidence that would change my belief
about whether or not backscatter devices are safe. What evidence would you
need to convince you that they are safe?

~~~
tomjen3
This isn't about whether they are safe or not (a subject I don't give much of
anything about), but about getting them banned. If we can't get them banned
for privacy issues (as they should be) but we can get them banned for
something else, then I will take that.

And it was a leading scientist.

------
carson
I found the most interesting part of this to be the end when they list one of
the concerns as Software. For those who want a point of reference of what
_could_ go wrong check out the Therac-25 story
<http://en.wikipedia.org/wiki/Therac-25>

~~~
jambo
I had the exact same thought.

"Because this device can scan a human in a few seconds, the X-ray beam is very
intense. Any glitch in power at any point in the hardware (or more importantly
in software) that stops the device could cause an intense radiation dose to a
single spot on the skin."

------
sstone
The document was linked here before but is very detailed and interesting, even
naming specific issues:

A) The large population of older travelers, >65 years of age, is particularly
at risk from the mutagenic effects of the X-rays based on the known biology of
melanocyte aging.

B) A fraction of the female population is especially sensitive to mutagenesis
provoking radiation leading to breast cancer. Notably, because these women,
who have defects in DNA repair mechanisms, are particularly prone to cancer,
X-ray mammograms are not performed on them. The dose to breast tissue beneath
the skin represents a similar risk.

C) Blood (white blood cells) perfusing the skin is also at risk.

D) The population of immunocompromised individuals--HIV and cancer patients
(see above) is likely to be at risk for cancer induction by the high skin
dose.

E) The risk of radiation emission to children and adolescents does not appear
to have been fully evaluated.

F) The policy towards pregnant women needs to be defined once the theoretical
risks to the fetus are determined.

G) Because of the proximity of the testicles to skin, this tissue is at risk
for sperm mutagenesis.

H) Have the effects of the radiation on the cornea and thymus been determined?

~~~
pygy_
I've been told by an engineer friend of mine that the radiation dose these
scanners deliver was dwarfed by the in-flight cosmic irradiation.

He didn't give me numbers, though. It would be nice if a radiotherapist (or
another expert) could chime in on this topic.

\----------------------------

edit: answering my own question: he's wrong.

from [1] :

>The estimated occupational effective dose for the aircraft crew (A 320)
working 500 h per year was 1.64 mSv.

> Other experiments, or dose rate measurements with the neutron dosimeter,
> consisting of LR-115 track detector and boron foil BN-1 or 10B converter,
> were performed on five intercontinental flights.

> Comparison of the dose rates of the non-neutron component (low LET) and the
> neutron one (high LET) of the radiation field at the aircraft flight level
> showed that the neutron component carried about 50% of the total dose.

> The dose rate measurements on the flights from the Middle Europe to the
> South and Middle America, then to Korea and Japan, showed that the flights
> over or near the equator region carried less dose rate; this was in
> accordance with the known geomagnetic latitude effect.

[1]
[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi...](http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VB2-4P2JD46-1&_user=10&_coverDate=12/31/2007&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1533561355&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=520a0ee22c14a68863a239e971832eea&searchtype=a)

~~~
uvdiv
No, actually your data validates him. Maybe you are confusing 'm' with 'μ',
that is, milli- (10^-3) with micro- (10^-6)?

> _The estimated occupational effective dose for the aircraft crew (A 320)
> working 500 h per year was 1.64 mSv._

1.64 mSv (milliSieverts) / 500 hours = 3.28 μSv/hour. A 3-hour flight is 10
μSv.

For comparison, the FDA letter [1] linked in another comment here cites the
effective dose of the backscatter x-rays as 0.25 μSv.

The cosmic ray dose from a 3 hour flight is 40 times that of the backscatter
x-ray. Pretty much "dwarfs it".

(Note that while the FDA letter says the effective dose is 0.25 μSv, the
footnote there (11) says that RapiScan is <=0.05 μSv. Not sure how to parse
this -- maybe the 0.25 μSv is a regulatory definition, not the real dose. An
NPR article [2] I cited earlier claimed 0.02 μSv, consistent with that <=0.05
μSv figure.

While I'm in these parentheses, NOAA has a table [3] of cosmic ray doses as a
function of altitude. Pretty much consistent with your source -- 3 μSv/hr at
30,000 ft, 6 μSv/hr at 40,000 ft).

[1] [http://www.fda.gov/Radiation-
EmittingProducts/RadiationEmitt...](http://www.fda.gov/Radiation-
EmittingProducts/RadiationEmittingProductsandProcedures/SecuritySystems/ucm231857.htm)

[2]
[http://www.npr.org/templates/story/story.php?storyId=1268330...](http://www.npr.org/templates/story/story.php?storyId=126833083)

[3] <http://www.swpc.noaa.gov/info/RadHaz.html>

~~~
pygy_
Indeed. I know the difference between µ and m, but I missed it here.

/hides

------
jcromartie
Just as a general policy, I don't willingly step into superfluous machines
intended to irradiate me.

~~~
pjscott
The airplane itself is much less superfluous, but irradiates you far more than
the backscatter machines. Are you sure you're not just putting a sort of halo
of evilness around the backscatter machines because you dislike them for other
reasons?

(Full disclosure: I'm not particularly bothered by backscatter machines as
such, but I vehemently object to the paranoid, theatrical, and statistically
silly approach to security that has provided the impetus for their
installation.)

~~~
catch23
what's your source that the radiation emitted from sitting in the airplane
cabin is higher than a cat scan machine?

------
DanI-S
Airport security is ridiculous. What do we do when the first bright terrorist
figures out they can blow up 500 people in the line for the scanner?

~~~
pjscott
We'll faint dead away!

Seriously? We could implement pipelined multi-stage inspections, like a
security line to get into another security line, and hire more TSA people to
make sure everyone is spread out. And have bomb-sniffing dogs everywhere. This
would be silly, but I wouldn't put it past the TSA to actually do it.

------
DanielBMarkham
I believe what's happening is the use of the radiation concerns is a proxy for
the underlying problem: regularly taking naked pictures of the population in
the name of security.

I don't think anybody can effectively argue that the whole enterprise is in
dire need of grownups -- too easy to get screwed the next time there is an
attack. But you _could_ argue that radiation is a key factor, or just wave
your arms around and yell a lot. With enough arm-waving, smoke, and mirrors
you can make the case that the population is deeply concerned about radiation
effects -- regardless of the science -- so "something must be done".
"Something must be done" is what got us here in the first place, perhaps
"something must be done" is what can get us out.

~~~
Tamerlin
More to the point, it's the government engaging in pornography, illegal
search, and sexual assault combined with radiation overdoses in the name of
FALSE security.

We already know that they don't work, and they don't even pretend to address
any of the real security vulnerabilities. They'll only deter idiot terrorists,
not real ones.

