[ RadSafe ] [Non-DoD Source] Re: Meaning of Rem? (UNCLASSIFIED)

Mon Nov 13 11:23:51 CST 2017

Thanks to the posters who provided the historical information on rem and the various links.  It's interesting that, according to Ron Kathren, Herbert Parker's cold contributed to the choice of an abbreviation.

I did a little more searching and found this excerpt from _The Dragon's Tail: Radiation Safety in the Manhattan Project, 1942-1946_  (Barton C. Hacker, Univ. of California Press, 1987, pp. 41-42; https://books.google.com/books?id=H2EzvHupWRkC&pg=PA41&f=false):

"In the health physics section [at the University of Chicago's Met Lab], research fell chiefly to Herbert Parker's [1910-1984] protection measurements group.   Instruments were not the sole concern.  Parker also faced the old problem of finding satisfactory units to relate the physics of ionization to biological effects.

"The roentgen was defined only for X and gamma rays, but the project faced, Parker noted, the 'practical problem of adding the doses received by a large group of workers from quantum radiation, alpha, beta, and neutron radiation.'     The answer was a common unit.  The key choice was to base it on energy absorbed rather than on ions produced.  The 'rep' (roentgen equivalent physical) measured dose as energy absorbed per unit mass (ergs per gram)  equivalent at a point in the body to exposure in roentgens.  since biological effects varied with kind of ray, Parker derived a second unit that included a biological factor.  Termed RBE (Relative Biological Effectiveness), it was found by experiment for each kind of radiation.  The measure of a biological dose was then the product of rep time RBE.  Parker called it the 'rem' (roentgen equivalent mammal or man). 'Roentgen equivalent biological' might have made better logic; he rejected that term when he learned that hearers might confuse rep and reb.   Parker completed the new system in early 1944.  [Health Physics Division Chief Robert S.] Stone proposed it for the project at a Met Lab meeting on 7 March.  Simple, thoughtful, and convenient, Parker's system won many users during the way.  Security prevented its public dissemination until 1948, but not until the late 1950s did rem, the dose unit, fully displace roentgen, the exposure unit, as the basic measure in radiological safety."

Another online reference is Herbert Parker and William C. Roesch, "Units, Radiation: Historical Development" in George L. Clark, ed., _The Encyclopedia of X-ray and Gamma Rays_ (1963), 1102-1107 (https://archive.org/stream/encyclopediaofxr00clar#page/1102/mode/1up).

Rick Strickert
Austin TX

-----Original Message-----
From: RadSafe [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Falo, Gerald A CIV USARMY MEDCOM APHC (US)
Sent: Monday, November 13, 2017 10:34 AM
To: The International Radiation Protection (Health Physics) Mailing List <radsafe at health.phys.iit.edu>
Subject: Re: [ RadSafe ] [Non-DoD Source] Re: Meaning of Rem? (UNCLASSIFIED)

Classification: UNCLASSIFIED
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Oak Ridge Associated University has a nice page discussing the origin of "selected radiological and nuclear terms" "Rem" can be found here - https://linkprotect.cudasvc.com/url?a=https://www.orau.org/ptp/articlesstories/names.htm%23rem.&c=E,1,UHEgF_a-LoasBJwoQX_kXl6eUut_UAS47C4vjGIdIaa3W8mb3vrxNn9u0iEuHWfa0KCLdiMsDwgPbKb9VF5IajJIzgRiNP6zvjHhvBCisfo,&typo=1

Scrolling leads to other interesting origin stories.

Enjoy,
Jerry
________________________________

Gerald A. Falo, Ph.D., CHP
U.S. Army Public Health Center - Health Physics Division gerald.a.falo.civ at mail.mil gerald.a.falo.civ at mail.smil.mil
410-436-4852
DSN: 584-4852

-----Original Message-----
From: RadSafe [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Delvan Neville
Sent: Friday, November 10, 2017 6:09 PM
To: The International Radiation Protection (Health Physics) Mailing List
Cc: Radsafe (radsafe at agni.phys.iit.edu)
Subject: [Non-DoD Source] Re: [ RadSafe ] Meaning of Rem?

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----

That's a holdover from the age of the terminology.  Originally one rem was defined as "a relevant biological effect equal to that produced by one roentgen" for x-rays, and there was the 'rep' (roentgen equivalent
physical) for radiations other than photons that then combined with an RBE to get rem. In the mid-50s ICRP suggested the use of the rad instead of the rep, and the definition of the rem changed to being the product of rad * RBE instead of the old definition that tied it directly to one roentgen.

Delvan Neville
Corvallis, OR

On Fri, Nov 10, 2017 at 11:07 AM Strickert, Rick (Consultant) < rstrickert at signaturescience.com> wrote:

> Why does "rem" stand for "roentgen equivalent man"?   The roentgen is an
> unit of gamma exposure in air.   Wouldn't the rem better stand for "rad
> equivalent man" given the rem included the Biological Quality Factor?
>
> Rick Strickert
> Austin, TX
>
>
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