[ RadSafe ] definition of Rad

edmond0033 edmond0033 at comcast.net
Tue Oct 9 20:42:30 CDT 2007


I don't believe there was an X-Ray tube at that time that could last that 
long to kill a  poor rat.!!!.  It must have been calculated by some preEPA 
person.

Ed Baratta

edmond0033 at comcast.net
----- Original Message ----- 
From: <Rainer.Facius at dlr.de>
To: <eic at shaw.ca>; <Colette.Tremblay at ssp.ulaval.ca>; <radsafe at radlab.nl>
Sent: Tuesday, October 09, 2007 12:12 PM
Subject: AW: [ RadSafe ] definition of Rad


'The rad was first defined in 1918 as the unit of X-ray dose delivered per 
hour required to kill a mouse in 1000 hours'



Dear Kai,



Your new entry is much closer to the truth. Nevertheless, protracting the 
exposure over 1000 hours = 41 2/3 days would raise the LD50(30) by a factor 
of perhaps three or even more, i.e., to 3000 R due to the repair and 
recovery taking place during exposure. So the new 'definition' again is 
wrong by this "dose rate effectiveness factor" (the size of which I just 
guesstimated).



Radiation biology is much more intricate than realized 1918 - and by one or 
the other even today. :-)



Perhaps someone should try to look into the Russ (1918) paper to find out 
what really has been said (I am trying to get a copy).



Kind regards, Rainer


________________________________

Von: Kai Kaletsch [mailto:eic at shaw.ca]
Gesendet: Di 09.10.2007 14:37
An: Facius, Rainer; Colette.Tremblay at ssp.ulaval.ca; radsafe at radlab.nl
Betreff: Re: [ RadSafe ] definition of Rad



The Wikipedia entry has been changed to: 'The rad was first defined in 1918
as the unit of X-ray dose delivered per hour required to kill a mouse in
1000 hours', which agrees well with the numbers that Rainer found, but not
so well with the 1986 edition of Dictionary of Scientific units.

The reference given in Wikipedia is still Russ S, Arch Rad and Electrotech
23, 226, 1918 according to Jerrard and McNeil (1992). Dictionary of
Scientific Units. Chapman and Hall.

Regards,
Kai


----- Original Message -----
From: <Rainer.Facius at dlr.de>
To: <Colette.Tremblay at ssp.ulaval.ca>; <eic at shaw.ca>; <radsafe at radlab.nl>
Sent: Friday, October 05, 2007 8:37 AM
Subject: AW: [ RadSafe ] definition of Rad


Thank you, Colette.



So it is yet another 'unit'.



To think of it; for me, the familiar abbreviation of the ICRU-unit is "rad".



In Kai's original post he wrote " the Wikipedia entry for 'Rad', ", which
indeed to the very careful reader might have signalled that another 'unit'
was addressed. :-)



Kind regards, Rainer



________________________________

Von: Colette Tremblay [mailto:Colette.Tremblay at ssp.ulaval.ca]
Gesendet: Fr 05.10.2007 15:59
An: Facius, Rainer; eic at shaw.ca; radsafe at radlab.nl
Betreff: RE: [ RadSafe ] definition of Rad



Hi Rainer,

I checked the 1986 edition of Jerrard. I quote it:

Historically the rad can be traced back to 1918. In this year Russ suggested
that the unit of X-Ray dose should be the dose required to kill a mouse and
that the unit should be named the rad (4)
(4) Russ S., Arch Rad and Electrotech 23:226 (1918)

What I understand is that the name proposed by Russ was later adopted but
the magnitude of the adopted unit was much smaller than what he had in mind.
Maybe this caveat could be added to the Wikipedia entry to remove any
confusion?

Regards,

Colette

---
Colette Tremblay
Spécialiste en radioprotection
Service de sécurité et prévention
Université Laval

Pavillon Ernest-Lemieux, bureau 2527
2325, Rue de la Vie-Étudiante
Québec QC Canada  G1V 0B1

(418) 656-2131 poste 2893
Télécopie: (418) 656-5617

Colette.Tremblay at ssp.ulaval.ca
www.ssp.ulaval.ca/sgc/radioprotection
--

Message relatif à la confidentialité:
http://www.rec.ulaval.ca/lce/securite/confidentialite.htm


-----Message d'origine-----
De : Rainer.Facius at dlr.de [mailto:Rainer.Facius at dlr.de]
Envoyé : 5 octobre 2007 09:36
À : Colette Tremblay; eic at shaw.ca; radsafe at radlab.nl
Objet : AW: [ RadSafe ] definition of Rad

Collette:



The lethal doses for mice as quoted in the PNAS paper are given in the 'old'
unit R (Röntgen) which for practical purposes - depending on the material -
is nearly equivalent to the rad as defined by the ICRU in 1953 (what appears
to be part of the rationale for this choice).



With this unit of dose it takes MANY hundreds instead of ONE rad to kill
mice. If indeed your source (Jerrard and McNeil, 1992 ) says otherwise, it
either speaks of yet another "unit" or it speaks nonsense.



Kind regards, Rainer


________________________________

Von: radsafe-bounces at radlab.nl im Auftrag von Colette Tremblay
Gesendet: Do 04.10.2007 21:40
An: Facius, Rainer; eic at shaw.ca; radsafe at radlab.nl
Betreff: RE: [ RadSafe ] definition of Rad



Hi:

The Wikipedia entry states:

"The rad was first defined in 1918 as the unit of X-ray dose required to
kill a mouse.[1]"

And the reference given is:

[1] Russ S, Arch Rad and Electrotech 23, 226, 1918 according to Jerrard and
McNeil (1992). Dictionary of Scientific Units. Chapman and Hall.

Our library has the 1986 edition of Jerrard and McNeil. I'm going to check
it.

Colette
---
Colette Tremblay
Spécialiste en radioprotection
Service de sécurité et prévention
Université Laval

Pavillon Ernest-Lemieux, bureau 2527
2325, Rue de la Vie-Étudiante
Québec QC Canada  G1V 0B1

(418) 656-2131 poste 2893
Télécopie: (418) 656-5617

Colette.Tremblay at ssp.ulaval.ca
www.ssp.ulaval.ca/sgc/radioprotection
--

Message relatif à la confidentialité:
http://www.rec.ulaval.ca/lce/securite/confidentialite.htm

-----Message d'origine-----
De : radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] De la part
de Rainer.Facius at dlr.de
Envoyé : 4 octobre 2007 05:44
À : eic at shaw.ca; radsafe at radlab.nl
Objet : AW: [ RadSafe ] definition of Rad

Kai,

you may need up to thousand rads (up to 10 Gy)  of acute sparsely ionizing
radiation to kill an adult healthy mouse.

Rainer


Morton  J I, Siegel B V, Radiation Sensitivity of New Zealand Black Mice and
the Development of Autoimmune Disease and Neoplasia. Proc Natl Acad Sci U S
A. 68#1(1971)124-126.


"Young New Zealand Black (NZB) mice manifested extremely high resistance to
the lethal effects of acute exposures to ionizing radiation, with a dose
necessary to kill 50% of the animals within 30 days, LD50(30), of 964
roentgens (R) at 30 days of age and of 856 R for 90-day-old mice. In
contrast, Coombs' positive 9-month-old NZB mice (with low primary immune
response) were highly susceptible (LD50(30) = 543 R), possibly because of
anemia-stimulated erythropoiesis leading to a depletion of stem cells."

Dr. Rainer Facius
German Aerospace Center
Institute of Aerospace Medicine
Linder Hoehe
51147 Koeln
GERMANY
Voice: +49 2203 601 3147 or 3150
FAX:   +49 2203 61970

________________________________

Von: radsafe-bounces at radlab.nl im Auftrag von Kai Kaletsch
Gesendet: Di 02.10.2007 18:10
An: radsafe at radlab.nl
Betreff: [ RadSafe ] definition of Rad



Friends,

According to the Wikipedia entry for 'Rad', it was defined from 1918 to 1953
as the unit of X-ray dose required to kill a mouse. 1) I never heard this
definition before and 2) This seems like a very low dose for killing
anything.

This is somewhat before my time and I normally use SI units. Is the
Wikipedia statement correct?

Kai

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