[ RadSafe ] Cancer Risk at Prolonged Low-Level Exposures

[Brennan, Mike (DOH)]

I read most if this, and skimmed the rest, and have a couple of thoughts:

1) Professionally, it would be easiest for me if this study's findings are correct, so I am not trying to shoot holes in it for personal benefit.

2) I think their attempts to account for smoking by excluding cancers associated with smoking is sound.

3) If they explained why they excluded leukemia I did not find it.

4)  Even though this was a meta study to examine the cancer mortality rate due to ionizing radiation exposure, I believe they should have included a control group, demographically matched to the subjects in the study.  If the background cancer rate is higher than the cancer rate at the lower end of their exposure graph, that would present interesting questions.

5)  I am not confident "Death Registries" or "dose records" capture all the relevant information.  As an example, both of my parents were diagnosed with multiple forms of cancer over their lifetimes, but neither died of cancer.  Neither were ever in any dosimetry program, but both of them received many orders of magnitude more radiation (from medical sources) than I have, even though I've been in a dosimetry program much of my adult life.  

6)  The study did not (and likely could not) take into account exposure to individuals who had been in the military.  I know that my personal exposure while on Active Duty in the US Navy was much, much higher than it has been while in my present program.  I suspect this is true for many (most?) of the radiation workers in the US who got their start in the Navy Nuclear Power Program.  (the other countries I cannot speak to)

7)  There is a time issue worth considering.  "Back in the Day" allowable exposures were higher, organizations were more willing to burn people out, so accumulated doses were probably higher.  Cancer detection and treatment were less successful.  I am not sure of all the nuances those facts introduce to the analysis, but they should be looked at.  It could lead to the higher accumulated exposure having a higher mortality rate due to technology changes, which would complicate the findings of this report.

8)  There is an age factor that should be considered.  Unless I misread the report, there was no attempt to account for age.  Thus someone in a dosimetry program who is in their 20s with a small accumulated dose and someone in their 60s with a much larger accumulated dose are both considered the same, but you would expect a higher cancer death rate among older people.  What happens to the conclusion if, once age is accounted for, the cancer rate is flat across the exposure range?  

An interesting study, but I don't think it is as conclusive as might be hoped. 

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Conway Lowe Family
Sent: Wednesday, October 21, 2015 11:30 AM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] Cancer Risk at Prolonged Low-Level Exposures

For your reading interest, see
https://srp-uk.org/news/article/102/study-provides-more-precise-estimates-of
-cancer-risks-associated-with-prolonged-low-level-radiation-exposure

 

This extensive study of workers (available for download from the British Medical Journal, BMJ) provides more precise estimates of cancer risks and radiation exposures at low levels.  According to the associated commentary in the BMJ, it does not provide any evidence for a threshold level (no risk below the threshold) or for a hormetic effect.

 

Leo Lowe (mostly retired)

(formerly with SENES Consultants and Arcadis Canada)

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