Re: Gy and Sv = J/kg

[JMUCKERHEIDE@delphi.com]

Jack Couch reflects the fact, but does not quite say, that Gy and Sv having
the same units is unscientific and indefensible: 

> At 03:48 AM 10/5/96 -0500, Jim Muckerheide wrote:
> 
> >Jack Couch missed the point:
>  <snip>
> >
> >Jack Couch had written:=20
> >> There are other examples, such as Circumference =3D 2 pi Radius.<snip> =
> >
> Jim wrote:
> >This "conversion" doesn't change the _meter_! It does not say 6.28=3D1.=
>  Totally
> >unlike saying 20=3D1 for Gy-Sv "conversion" (as opposed to an actual change=
>  in a=20
> >total value of 20 vs 1 as measuring different quantities). R and C are
> >different vectors, they have a different number of meters. They are not
> >converting meters to equivalent-meters! =20
> >
> My intent was to agree that when using SI units in connection with H and=20
> D the numbers of J/kg's don't necessarily equate. Perhaps I could have=20
> chosen a more suitable parallel and been more clear.

Eliminate the word "necessarily" :-) 

> F. Attix said it much better: "Thus where the dimensionless quality factor
> Q has a value of, say, 2, the dose equivalent in tissue would be 2 Sv (or 2
> J/kg).
> This does not mean that 2 J/kg =3D 1 J/kg, any more than saying that if a
>  room has a length of 5 m and a width of 3 meters, then 5 m must equal 
> 3 m."
> [Health Physics Vol. 41, pp. 210-213, 1981]
> 
> T. R. Crites, in his lament concerning the dose equivalent unit, says:
>  "Deposit 1 J/kg of 2.5 MeV neutrons for a dose of 1 [Gy] in a body and 
> you'll have something like 9 [Sv] of dose equivalent, but you really 
> don't have 9 J/kg of energy deposited anywhere." 
> [Health Physics Vol. 38, pp. 431-432, 1980]

Right. It's not science. As ICRP and NCRP are not science organizations.
 
> >> David Golnick* offers a nice solution to those (including my students)
> >> who agonize over this point. He endows Q with the "units" Sv/Gy...This
> >> of course breaks both with tradition and the formal definition of Q,
> >> where Q carries no units.
> >
> >This is good; its true. But it still doesn't provide a "solution" to J/kg,
>  nor help the student figure it out.
> >
> Yes, it hides the issue. And at some point everyone, including
> students, must be let in on our sticky little secret. Why should we be the
> only ones lying awake at night agonizing over it. :-)

My only point is that rather than agonize, state plainly that this is
scientific junk; and state it as such in opportunity and every course and
insist such junk be changed to stop being an embarrasment to those in HP who
have any interest in the subject as a science rather than a bureaucratic
policy enterprise. 
(Unless your funding would suffer  :-)

> Apparently, the idea of assigning Sv/Gy to Q has been around awhile. The
> earliest citation I can find is by J. Sabol, et al. in 1977 (I can provide a
> reference if anyone is interested.)
> 
> >Louis had it right.  The conversion factor _changes the units_!   The =
>  wrong.
> >With Gy in J/kg, Sv is in "units" of "the biological damage equivalent to
>  the damage of J/kg of low LET radiation" (J-eq-damage/kg?)  
> >
> This "conversion factor" doesn't convert units. Its dimensionless.

Funny, it says "_changes the units_!"  It is not "dimensionless" (no matter
what ICRP and NCRP say). Maybe the problem is in the English. :-) 

> The J/kg remains a J/kg. The problem can't be solved by adding camouflage=20
> to the SI units of H. I do agree that H is not D, and Q is a dimensionless=
> weighting factor with an assigned value based on comparative bio-damage.

Not right. Q is not a valid  "dimensionless weighting factor".  As stated I
simply point out that this "equivalency" can not exist in science. 

If the _concept_ were even valid, then a new unit that reflects the intent
would be needed/created. BUT, the concept is NOT valid. As Victor Bond and
NCRP 104 state, no such conversion can be found in physical reality. Q can not 
be defined for alphas as 20. Different conditions/studies produce different
"results"; and no foundation in physical conditions exists as a basis for any
such unit. 

While not entirely valid, consider "J/kg" in physics. Now consider dropping a
shotput on the hood of your car, the windshield, a steel I-beam, a styrofoam
sheet, and a sheet of neoprene. Now define terms in units of J/kg that
reflects the damage. Now consider dropping a pillow of 16 lbs of feathers.
Real science has ways of considering the physical conditions and properties in 
quantities and units of matter that reflect the differences. "Rad science"
arbitrarily fabricates terms that even obfuscate the differences, while
ignoring completely parameters that reflect real physical distinctions. 

Now, when biology is (erroneously) seen as a physics problem (endemic to "rad
science"), the "linear model" is applied to the damage term of dropping the
mass (the shot and the pillow), on the hood, the windshield, the I-beam, the
styrofoam, and the neoprene. (And in biology there's a lot of neoprene.  :-) 

> As most list members know, this saga (Ralph Thomas called it a soap=20
> opera) over dose equivalent units has been ongoing since its inception=20
> by Cantril and Parker in 1945.=20
> 
> One of the clearest, most sensible statements I've read concerning the=20
> Sv is, again, by F. Attix in his letter to the editor.[Health Physics=20
> Vol. 46, p. 479, 1984] A couple of ideas included in his letter are well=20
> worth passing along.
> 
> "=85there is nothing wrong with the present definition=85"  "The same units=
> (e.g. J/kg) certainly can be applied to different co-existing quantities,=20
> such as [D] and [H] without being illogical." (Attix explains his position=
> with reference to ICRU Report 33.)

There's "nothing wrong" only if "units" are meaningless.  :-)   Where is
science?  

> Paraphrasing Attix: An alternate, equally valid definition [other than=20
> leaving Q unitless and defining H with SI (J/kg) units as we have it today]=
> could have been reached by ICRU at the outset by acknowledging that=20
> H *is not a physical quantity*. Therefore it need not be measured in terms=
> of an SI-derived unit. H could have been defined solely by H =3D QD in=20
> which D is a physical quantity but Q is a coefficient based on biological=20
> response information.=20

"More correct", not "equally valid".  :-)
 
> He continues by saying that it would have been perfectly reasonable=20
> (had the ICRU chosen to do so) to define the sievert as the (one and=20
> only) unit of dose equivalent, that the Sv would not be equated to=20
> 1 J/kg, and it would follow that Q would have units of Sv/Gy.=20

"acceptable", rather than "reasonable".

> Attix then states what perhaps many of us feel.  "I think this alternative=
> approach, if adopted initially, would have been more readily accepted=20
> by the health physics community. However changing to it now probably=20
> would not be worth the extra confusion attending any such change."

This is anti-science. This is ok only if _science_, developing and expanding
knowledge, means nothing in the face bureaucratic ineptitude and inertia, seen 
mostly as pushing paper. It would be much better to quote the many in science
who have tried to expand and correct these ICRP, ICRU, BEIR and NCRP failures, 
over the years. The real fallacy is the pretense that these organizations even 
attempt to reflect good science (even with much good science being done below
the "policy" level in their own specific topics and reports). As government
agents, the science and scientists are ignored in favor of serving government
policies that ignore science. See eg, Robley Evans, a giant of the science, in 
HPJ 1974 utterly embarrassing/destroying the corrupt "science" in explicit
language of the work of BEIR 1972. It had no effect because BEIR, then or now, 
is not based on science. 

Many science members of BEIR and NCRP and ICRP and ICRU, etc, are embarrassed
when asked, but in rad science there is no science equivalent to the
professional societies of the physicists or chemists etc. The many good
scientists that have worked in rad science have no organization to assess the
science without being beholden to those who serve the government bureaucracies 
and policies that directs their work. 

> Jack Couch
> Bloomsburg University

Thanks, Jack.

Regards, Jim Muckerheide
jmuckerheide@delphi.com