A new study which looked at the damage to mice DNA from continous, low dose radiation is sure to be ignored by the anti-nukes and overplayed by the pro-nukes. No significant DNA damage was found in those tissues examined in the study.
However, using BEIR VII estimates, the excess cancer risk associated with the delivered dose is only 1% excess risk. That would be very hard to see on a DNA level with so few animals. The authors acknowledge that any effects may be below their detection levels.
"However, using BEIR VII estimates, the excess cancer risk associated with the delivered dose is only 1% excess risk. That would be very hard to see on a DNA level with so few animals."
ReplyDeletePresumably the obvious next step would be to do a larger study over a longer period of time. Over a couple of years the assumed risk would be around 10-20% which should be observable.
I thought the main finding of the study was that the same low dose, delivered acutely via xrays, showed a definite detectable damage response. Whereas the same low dose delivered slowly, via I-125, over 5 weeks showed no such effect.
ColinG
I agree with your thoughts on the main finding of the study. And I'm all for more studies. However, for LNT the endpoint is cancer, not specific genetic damage endpoints. Until we fully understand how many ways cancer can manifest and what evidence we should expect to see, can we fully appreciate what this means. For example, epigenetic effects have been linked to cancer, not just genetic effects.
ReplyDeleteNote that in BEIR VII it was mice experiments with acute & chronic doses (with cancer as the endpoint) which played a large role in determining the DDREF (Annex 10B). And numerous molecular and cellular responses and peculiarites are described in Chapter 2.
Ultimately, the lower the dose rates and doses one probes, one ends up with same epidemiological problem on the cellular/molecular level as one does at the cancer/organism level. You can't say with 95% certainty that what you're observing isn't due to chance.
Look at Figure 1 in the paper. For continuous exposure, the treated group certainly appears to have greater base lesions than the control group. On the whole, the continuous exposure looks more detrimental than even the acute exposure. Yet, there is >5% chance that these differences are due to chance. So the authors conclude no statistical difference.