AW: AW: RE: AW: [ RadSafe ] DNA Damage and Oxydative Processes

[Rainer.Facius at dlr.de]

John:

The LNT concept for radiation protection is with us nearly twice as long, for more than 50 rather than 30 years. 

The vast majority of data obtained until 50 years ago on human health effects from low dose, low dose rate exposures favoured the idea that dose thresholds exist below which no detrimental effects could be observed and hence - in the realm of scientific knowledge - did exist. This was in line with the most fundamental concept of toxicology/pharmacology coined nearly 500 years ago by Theophrastus Phillippus Aureolus Bombastus von Hohenheim, AKA Paracelsus, as "dosis facit venenum", i.e., "the dose determines venomousness". As an aside, instead of dedicating your time to discussions on topics where you yourself claim insufficient expertise for developing independent own conclusions, you might wish to allocate some time on pondering why on earth one specific natural toxin, which like myriads of other ones has been acting upon the biosphere since its origin, namely ionizing radiation, should be exempt from this otherwise predominant rule. 

In the early 50s, in the aftermath of the atomic bombings when the necessity became pressing to assess the late human after effects of these acute exposures, the idea of LNT was adopted as a postulate(!!!) in order to err on the safe side when estimating these losses quantitatively. At that time one drew on the only empirical relation supporting this by then exceptional LNT idea, i.e., on the induction of mutations by exposing drosophila to high doses - today we know, misleadingly so.

Since to my knowledge neither before nor later until now any observation on human cancer induction from low dose and low dose rate exposures yielded data which - in the very ordinary sense of elementary curve fitting principles - favoured a LNT response function with a positive slope, this postulate never rose to the epistemological rank which you - probably unconsciously so - bestow on it in miscalling it a "model". 

In the hierarchy of scientific ideas - "model < hypothesis < theory" - the LNT postulate never made it to the lowest level "model" since simply there weren't data to be properly modelled with this idea. Again, and for the last time, I challenge you to search for such data and present them. Of course I do not wish to interfere with your proper right to believe - in BEIR, in LNT, in whatsoever you choose. 

As it pertains to the appropriateness of postulating LNT for practical and regulatory radiation protection purposes, I am not qualified to judge although it appears to me that its (the postulate's) repercussions for everyday life, for economic welfare as well as for psychological and even physiological wellbeing may not have been properly accounted for by, e.g., the BEIR VII press release.

Regards, Rainer

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

-----Ursprüngliche Nachricht-----
Von: John Jacobus [mailto:crispy_bird at yahoo.com] 
Gesendet: Montag, 11. Juli 2005 07:02
An: Facius, Rainer; jimm at WPI.EDU; jjcohen at prodigy.net; goldinem at songs.sce.com; radsafe at radlab.nl
Betreff: Re: AW: RE: AW: [ RadSafe ] DNA Damage and Oxydative Processes

Rainer,  the LNT model has been around for about 30 years.