The Lawrence Berkeley National Laboratory issued a press release on December 20, 2011 titled New Take on Impacts of Low Dose Radiation: Berkeley Lab Researchers Find Evidence Suggesting Risk May Not Be Proportional to Dose at Low Dose Levels.
The press release summarizes the results of a paper that has been published in the Proceedings of the National Academy of Sciences. That paper is titled “Evidence for formation of DNA repair centers and dose-response nonlinearity in human cells.”
The science used in the study is fascinating. I will not attempt to explain it in much detail other than to state that it uses time lapse, high-resolution photography and mathematical modeling to show how cell repair mechanisms work at various radiation doses. Not surprisingly, the repair mechanisms work better when they are not overwhelmed by a high rate of damage caused by high dose rates. At dose rates similar to those that might be experienced as a result of using nuclear energy – even under accident release scenarios – cellular repair mechanisms appear to be particularly effective.
The discovered repair mechanism leads to a decidedly non-linear damage response curve. Researchers using similar techniques might be able to demonstrate through cellular response measurements, in addition to the epidemiological studies that already show the same effect, that there is a threshold dose rate response curve.
Below that threshold dose rate, we can be confident that repair mechanisms work. If the experiments are followed through, the researchers should be able to prove that our evolved ability to effectively repair cell damage means that radiation doses do not accumulate. That would allow a conclusion that there is no need for any particular limits on lifetime exposure.
As long as people keep their short term doses below the levels at which their naturally evolved repair mechanisms are not overwhelmed, they should have no fear of radiation-caused cancers sometime in the distant future. That would be exceptionally good news for us all – except, of course, for those people who make their living by maintaining the fiction that our economy will be almost completely dependent upon hydrocarbon fuels for the foreseeable future.