[ RadSafe ] dose RATE is the decisive variable

[John Jacobus]

Rainer,
Interesting paper and chart.  However, I do not think
this is really new information, which is noted in the
abstract of the paper.  It was demonstrated at the
turn of the 20th century that fractionated doses
delivered to therapy patients increased the chance of
survival.  Factionation allows for replication and
repopulation of normal tissue into the tumor site. 
Tables were developed to establish proper
factionation, and the earliest I have seen is from
1914.  Even the BEIR committee recognizes there exists
a dose and dose-rate effectiveness factor (DDREF).  

It would seem to me the way to demonstate a dose rate
effect.  However, you have included the A-bomb and
external beam (therapy?) data, to determine your
"threshold."  There is not dose-rate effect with the
A-bomb data.  Without this data set, I doubt that you
can show a threshold exists.  

Looking at the data, I appears that the data for
external beam represents the exposure rates where the
"capacities" of the system are becoming
"overstrained."  Essentially, the patient is receiving
a great deal of radiation over several weeks, but not
over their lifetime.

--- Rainer.Facius at dlr.de wrote:

> The recent paper below elaborates a seemingly
> trivial principle, i.e., the response of (not only
> nonlinear) systems capable of intrinsic
> counteractive measures to compensate external
> stimuli is not primarily determined by the stimulus'
> amplitude but rather by the ratio between the
> stimulus' temporal gradient and the characteristic
> 'response' time of the system's feed-back control
> systems - as long as its capacities are not
> overstrained. Thus the rate is not a parameter - as
> conventionally it is conceived of - but a primary
> independent variable. 
> 
> Applying this 'law' to that subset of 13
> epidemiological studies which have been compiled by
> UNSCEAR 2000 and which provide the necessary data to
> pursue this approach (no cherry picking!), the
> authors arrive at a rather provocative result. I
> have prepared a graph from their table similar to
> their own but somewhat enhanced to facilitate the
> contemplation and mental digestion of these data
> which at face value would suggest that a threshold
> (or even the region for beneficial effects in terms
> of cancer mortality) extends to much higher chronic
> exposures (rates) than so far publicly discussed
> (e.g. the 5 mrem annually invoked the other day by
> Bernard Cohen). I attach that graph as PDF, hoping
> it will pass the moderator.
> 
> Enjoy, Rainer
> 
> Gregoire O, Cleland M.
> Novel approach to analyzing the carcinogenic effect
> of ionizing radiations
>
<http://www.ingentaconnect.com/content/tandf/trab/2006/00000082/00000001/art00002>
>  
> International Journal of Radiation Biology
> 82#1(2006)13-19
> 
> Abstract:
> Purpose: Cancer incidence of ionizing radiations
> exposure is considered to be proportional to the
> absorbed dose. However, there are disagreements
> between substantial amounts of epidemiological
> studies. In this study, we question the basic
> relationship of the risk estimate with total
> accumulated dose, and reanalyse available data on
> the basis of a daily dose concept. 
> 
> Materials and methods: The data analysed were
> relative mortality risk from all cancers vs.
> total-body dose on a daily basis. References have
> been selected on the basis of objective criteria. 
> 
> Results: We found that this relationship removes
> major discrepancies. It revises estimates of
> low-level exposures, with consequences regarding
> nuclear power plants safety, wastes management,
> medical applications or homeland security. 
> 
> Conclusions: The idea that the dose rate may have a
> significant impact on health effects of ionizing
> radiations is not new, but has always been
> considered as a parameter in models based on
> integrated dose. The novel approach in this paper is
> to consider the primary relevant parameter as an
> average of dose rate over a time period of one day.
> This is an argument to revise the whole philosophy
> in radioprotection, and place regulatory limits on
> specific locations instead of annual limits relevant
> to individual persons. 
> 


+++++++++++++++++++
May we never confuse honest dissent with disloyal subversion. 
Dwight D. Eisenhower  

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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