Unconventional Wisdom 5

How much?  How does it work?

“Curmudge, I’ve been telling my friends about our recent discussions…about how large doses of radiation are dangerous but very small doses are not only not a hazard but might even be good for you.  After my friends get over being incredulous, those who are truly perceptive start asking questions.  ‘Okay, Julie.  So as the radiation dose gets lower and lower, where does it stop being hazardous and start being beneficial?’ “

“That’s a very important question, Julie, but we should include more recent literature in our discussion.  Remember that Hiserodt’s book was published in 2005.  A more up-to-date resource is Volume 10 (2012) of the peer-reviewed journal, Dose-Response.  I recommend issue No. 2, a special issue on The Role of Linear and Nonlinear Dose-Response Models in Public Decision-Making, and issue No.4 dedicated to the distinguished Polish scientist, Zbigniew Jaworowski.  Actually, issue No. 4 is a follow-up to No. 2 on low doses of ionizing radiation.” 

“I won’t ask how you found this, Curmudge.  You’ve probably already forgotten.  But since you made the discovery and spent the past week reading the papers, would you be so kind as to share with me some of the authors’ more profound findings and comments?  They ought to help me answer my inquisitive and not-fully-believing friends. My friends may need to be reminded that for beta, gamma, and x-radiation, values expressed in sieverts (Sv) or grays (Gy) are numerically the same.”

“I’d be delighted to help inform your friends, Julie.  Let’s start with higher doses and work down.  We’ve learned from Hiserodt’s book:

·      At 100 cSv (100,000 mrem) people experience radiation sickness.

·      Below an instantaneous 70 cGy (70,000 mrem) dose Japanese atomic bomb survivors outlived their unexposed countrymen.  The optimum dose was around 10 cGy (10,000 mrem).  

·      At 48 cGy/yr (48,000 mrem) background, people in Ramasari, Iran are presumably healthy but likely unhappy with their despotic government.

·      According to T.D. Luckey, the optimum annual exposure is 10 cG/yr (10,000 mrem).”

“Okay, Old Guy, now let’s look at more recent literature.  When we refer to the Dose-Response journal, recall that the page numbers are sequential through a whole volume.”   

“In response to a question about whether an 11-mSv CT scan would be cause for worry about future cancer, C. L. Sanders provided this reassurance:  ‘Feel blessed that you have received this dose from CT scans.  You could receive an annual cumulative dose of 100 mSv (10,000 mrem) and experience the benefit of reduced cancer and other disease risk.’ (Personal communication, 2011.)

‘The (protective) adaptive response in mammalian cells and mammals operates within a certain window that can be defined by upper and lower dose thresholds, typically between about 1 and 100 mGy (100 and 10,000 mrem) for a single low dose rate exposure.’ (Mitchel, R. E. J.  Dose-Response Vol. 8, p. 192 [2010])   

‘For doses ≤ 100 mGy (10,000 mrem) [the equivalent of several CT scans] the frequency of neoplastic transformations was reduced below the spontaneous level, presumably because of gamma-ray activated natural protection with selective removal of aberrant cells via apoptosis.’ (Scott, et al.  See reference in our 8/08/11 blog posting.)”

“How do I answer if my friend next asks, ‘Well, Julie, since you seem to know so much, how does this radiation hormesis stuff work in the human body?’ “

“I’d say, ‘Read the literature.  There are great articles that deal with this in depth, including those by Cohen (J. Am. Phys. Sur. 13, no. 3:70[2008]), by Scott and Di Palma (Dose-Response Vol. 5, p. 230 [2006]) and by Vaiserman and by Tubiana et al. (references in our 8/08/11 blog posting).’  A statement by Tubiana et al. that caught my attention was, ‘Life developed in a bath of ionizing radiation and solar ultraviolet radiation and created aerobic organisms requiring (a) defenses against the metabolically induced reactive oxygen species, (b) DNA repair, and (c) elimination of damaged cells.’ It seems as if life required radiation hormesis from the very beginning.“

“But suppose my friend wants me to describe radiation hormesis briefly—as in an ‘elevator speech’.”

“Here it comes, Julie, in the words of Scott and Di Palma: ‘Low doses and dose rates of low LET radiation activate a system of cooperative processes in the body.  (They) include (a) defenses such as scavenging reactive oxygen species, (b) presumably p53 related activated high-fidelity DNA repair/apoptosis, (c) a novel auxiliary protected apoptosis mediated process that selectively eliminates aberrant cells, and (d) induced immunity.’ “       

“Wow, Curmudge.  I believe the big words in those papers tell us that CT scans are good for us and how they do the good things that they do.  By the way, do you understand those big words?”

“Consider me biology-challenged, Julie, but the hyperlink at p53 was really helpful.  I already knew that apoptosis means programmed cell death, and if the dying cells are cancer cells, that’s good news for all of us.”

“So what’s next, Obsolete Academic?”

“Let’s talk about policy issues.  That might be our ‘last hurrah’ on low doses of ionizing radiation, at least for the moment.”

Kaizen  Curmudgeon