[ RadSafe ] Natural gamma rays supposedly linked to childhood leukemia

[Dixon, John E. (CDC/ONDIEH/NCEH)]

Thanks Bobby. I am glad to see common sense is still out there.

Regards,
John

From: Scott, Bobby [mailto:BScott at lrri.org]
Sent: Thursday, June 28, 2012 05:20 PM
To: radsafe at health.phys.iit.edu <radsafe at health.phys.iit.edu>
Cc: Brennan, Mike (DOH) <Mike.Brennan at DOH.WA.GOV>; Jess Addis <ajess at clemson.edu>; Dixon, John E. (CDC/ONDIEH/NCEH); Dan McCarn <hotgreenchile at gmail.com>; Jeff Terry <terryj at iit.edu>; Andy Howard <howard at phys.iit.edu>
Subject: Natural gamma rays supposedly linked to childhood leukemia


Hi All,

I have taken a look at the new paper by G. M. Kendall et al. in the Leukemia Journal claiming a link between natural background gamma rays and childhood leukemia. The paper is titled “A record-based case-control study of natural background radiation and the incidence of childhood leukaemia [leukemia] and other cancers in Great Britain during 1980-2006.” Because of the additional radiation-phobia-related casualties in Japan that could be promoted by this article, I thought it to be important to take a close look at the modeling approach used by the researchers.  Of special interest was the mathematical form used for relative risk (RR) evaluation and what values of RR would be expected based on the RR function used when radiation doses are significantly greater than those from natural background.  The authors used an exponential form for relative risk , i.e., RR = exp(alpha*dose) for the natural background radiation effect. The authors claim that their calculated 12% excess relative risk (ERR) of childhood leukemia per mGy of cumulative red-bone-marrow dose from natural-background-related gamma rays supports the extrapolation of high-dose-rate risk models (e.g., based on A-bomb survivors) to low-rate exposure.  A 12% excess relative risk per mGy after low-dose, low-rate exposure implies a value of 0.12 per mGy for the parameter alpha.  With this value, RR for childhood leukemia at 100 mGy (similar to the annual dose from natural background radiation for the Kerala coast, India) would be calculated to be RR = exp(12) = 162,755. For a 200 mGy (20 rad) dose (similar to the annual dose from natural background radiation in Ramsar, Iran), RR would be calculated to be 26,489,122,130. As I think others may agree, such a derived dose-response function for leukemia RR for children raises serious questions about the validity of the results of the study of Kendall et al.

Best wishes,
Bobby
B. R. Scott
Lovelace Respiratory Research Institute
2425 Ridgecrest Drive SE
Albuquerque, NM 87108, USA




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