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Re: Airport screening and medicine
Richard, Julian and all:
It was my experience with several intercontinental flights that the amount
of radiation detected by this RM-70 detector is highly influenced by the
elevation of the sun above the horizon.
When the sun was above the plane, the radiation level I measured was about
X50 the background radiation.
Indeed, this detector does not detect particulate cosmic radiation, which
are ionized, thus affecting a much higher damage to the human tissue.
The current NCRP imposed limit of 5 Rads/year for occupational staff member,
used to be much higher in the past 30 to 40 years, and has been lowered
several times since than.
This limit is for gamma radiation only (I thing for neutron radiation too,
but I can't be sure) where the 'rule-of-thumb' : 1 Roentgen ~~ 1 Rem ~~ 1
Rad applies.
I am sure that many scientist are mulling about this current limit since it
appears to be too high: nobody will disagree that for pregnant occupational
employees, this 5 Rads/year is too high.
Now, the X-ray radiation which the TOTAL BODY airport screening machines
were not approved yet by the FDA. I recall seeing these pictures a year ago
on the webpage of the manufacturer.
These machines, I understand, utilize low energy X-Rays (10 -20 KV or
somewhat lower) which are readily (back)scattered. It is this backscattered
radiation that is detected and converted into images. Low energy X-Ray
radiation such as this is highly absorbed by the human tissue! I am not sure
what is the ratio between the amount of such radiation absorbed to the
amount of radiation (back)scattered from the body. I even think it is not
relevant since even the (back)scattered radiation had a chance to interact
with the human skin / tissue and cause damage.
Here are some point of concern if these machines a used on the population:
1. Damage to the eyes -- unprotected.
2. Damage to the thyroid gland - practically unprotected.
3. Damage to the gonads of males and ovaries of females, especially pre- and
in their productive age.
4. Damage to the skin which is the part of the human tissue which will
absorb most of this radiation.
On a personal level, I wholeheartedly second the wise contribution of Julian
who wrote:
"...For me radiation and radioactivity continue to have important uses in
modern society. We should not be aiming to achieve zero doses, we should be
looking to minimize these to sensible amounts that allow practices to
continue, and to use advances in science, where it is sensible and cost
effective to do so, to minimize peoples exposure."
"SENSIBLE" for me includes prudent use and utilization of SAFE technology
not resorting to "dry" and emotionless "mortality tables" calculation of
"cost / benefit";
Thus, I even dare to predict that those "screening" devices as described,
will not be approved by the Health Authorities to be operated 'en mess' on
the population.
People who are stating that the radiation a pessanger is absorbing during
such "screening" is less than "x%" than the radiation the passenger will be
subjected to, or absorbed, during the flight, are actually comparing bananas
to apples and do not understand all the aspect of radiation demages to the
human tissue.
Best regards to all.
Reuven Zach
Medical Physicist
===================================================================
From: "Richard L. Hess" <lists@richardhess.com>
To: <radsafe@list.vanderbilt.edu>
Sent: Saturday, November 13, 2004 4:39 PM
Subject: Re: Airport screening and medicine
> Reuven and all,
>
> I did this in 2002 and came up with an interesting plot showing about 25X
> the LA background level using an Aware RM-70 which is a small pancake G-M
> tube.
>
> I have the flight plot at http://www.richardhess.com/be/radlog/
>
> The file is named
> 3-hr LAX-CHI.jpg
>
> At the time I did this, the good folks here suggested that the G-M tube
> under-reports the high-energy cosmic ray particles.
>
> Cheers,
>
> Richard
>
> At 01:26 PM 11/13/2004 -0800, you wrote:
>>Sandy:
>>
>>I used the AWARE Electronics Model RM-60
>>Micro Roentgen Radiation Monitor attached to Laptop PC.
>>
>>I tested it prior to the flight on a mammography machine and found it to
>>be quite accurate and reliable.
>>
>>Here in LA, the background radiation was measured to be, if my memory does
>>not fail me, to be
>>around 10 microR/hour.
>>
>>Now, on what are you basing your statement " ... This does seem a bit
>>high. I travel quite
>>a bit, and, I don't expect that I have observed the dose rates you are
>>quoting..." ?
>>
>>Did you do such measurements?
>>With what detector(s)?
>>
>>Reuven Zach
>>
>>========================================================
>>
>>
>>----- Original Message ----- From: "Sandy Perle" <sandyfl@earthlink.net>
>>To: <radsafe@list.vanderbilt.edu>; "M Nivas" <motnivas@YAHOO.COM>; "Brian
>>Rees" <brees@LANL.GOV>; "Reuven" <reuven99@newsguy.com>
>>Sent: Saturday, November 13, 2004 12:51 PM
>>Subject: Re: Airport screening and medicine
>>
>>
>>>On 13 Nov 2004 at 12:03, Reuven wrote:
>>>
>>>>I once MEASURED the radiation dose during an intercontinental flight:
>>>>It was *** 50 times *** HIGHER than the background radiation at sea
>>>>level.
>>>
>>>Reuven,
>>>
>>>What did you use to measure the dose described above, and, what was
>>>the duration of the flight?
>>>
>>>If one considers the natural background to be, for assumption
>>>purposes, equals 7 microR/hr, then you're stating that the rate you
>>>observed was 350 microR/hr. This does seem a bit high. I travel quite
>>>a bit, and, I don't expect that I have observed the dose rates you
>>>are quoting. Additional source information would be appreciated.
>>>
>>>----------------------------------------------------------------
>>>Sandy Perle
>>>Senior Vice President, Technical Operations
>>>Global Dosimetry Solutions, Inc.
>>>2652 McGaw Avenue
>>>Irvine, CA 92614
>>>
>>>Tel: (949) 296-2306 / (888) 437-1714 Extension 2306
>>>Fax:(949) 296-1144
>>>
>>>Global Dosimetry Website: http://www.dosimetry.com/
>>>Personal Website: http://sandy-travels.com/
>>
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>>
>
>
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