RE: It is time to consider the lack of science in "effective dose"

["Christoph Hofmeyr" <chofmeyr@nnr.co.za>]

Prof Cameron,  Radsafers, 

Now this is very interesting and will probably have the radon brigade up

in arms.  A critical discussion from time to time of the science behind

our regulation is to be welcomed.  Own opinion.

Chris Hofmeyr

chofmeyr@nnr.co.za <mailto:chofmeyr@nnr.co.za> 

 

 

 



-----Original Message-----

From: John Cameron [mailto:jrcamero@facstaff.wisc.edu]

Sent: 12 January 2002 01:21

To: radsafe@list.vanderbilt.edu

Subject: It is time to consider the lack of science in "effective dose"





Dear Colleagues,  I think we should discuss the weak scientific basis of

effective dose from background or otherwise. Let us consider the

following debatable statements:



1. The WR value of alpha particles is probably closer to 3 than to 20.

(Personal communication from Robley Evans.)  There is (as far as I know)

no measured  RBE for alpha particles  close to 20.  The book Radiation

Protection Quantities:  A Radical Reappraisal by Simmons and Watt (Med.

Phys. Publ) states that no measured RBE of alphas is above 10. The ICRP

gave no documentation for their choice of 20.  When using helium nuclei

in radiation therapy, the RBE appears close to 1.



2. The equivalent dose to the lungs which presumably only increases the

risk of lung cancer cannot scientifically be added to the equivalent

dose to the other organs of the body. The tissue weighting factors have

never been evaluated by an independent scientific body other than the

ICRP which chose the values. NCRP Report No. 104 (1990) RE: determining

RBE values at doses below 0.2 Sv for radiation protection purposes, the

authors concluded that the Q value (now WR) could not be determined.

They suggested you choose an RBE you feel is reasonable! There is no

reason to believe that WT can be scientifically determined or that the

concept of adding up effective values from various organs can be

justified.



3. It is time to reject the unscientific concept of effective dose.  I

claim that the effective dose to the lungs from radon progeny is the

product of 3 unknowns: the dose to the lung tissue, the WR of alphas and

the WT for lungs.



4. I strongly suggest that we  use the physics quantity "imparted

energy" to describe the radiation to humans. This information would be

supplemented by a description (if available) of the type of radiation,

time factors, tissues exposed, etc. It is a rare event where an

accidental dose is of medical concern.



5. The IPSM (UK) report 53 on doses from diagnostic radiology shows that

the imparted energy correlates well with the effective dose.  The

imparted energy varies from 7 mJ (chest radiograph) to about 700 mJ for

a lower GI series. CT whole body doses are generally larger.  It should

be straight forward for the computer which is part every CT unit be

programmed to estimate the imparted energy from the physical parameters

for the scan.



6. The evidence from the nuclear shipyard worker study and the 100 years

of British radiologist mortality makes it clear that fractionated doses

up to about 0.2  Gy are almost certainly beneficial. See my article Is

radiation an essential trace energy?

http://www.aps.org/units/fps/oct01/a5oct01.html



7. We can not hope to see a scientific evaluation of radiation

protection quantities by the ICRP or NCRP. I suggest that HPS appoint an

ad hoc committee (perhaps in cooperation with other radiation scientific

groups) to study the validity of our present radiation protection

policies.



I suspect private $  would be available to help support this study. I

would be willing to donate $10K.



Best wishes, John





-- 

John R. Cameron, Ph.D.

Professor Emeritus,UW-Madison

Departments of Medical Physics, Radiology & Physics

Winter home address:

2678 SW 14th Dr. 

Gainesville, FL 32608 

(352) 371-9865  FAX 371-9866

e-mail: jrcamero@facstaff.wisc.edu



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