Lawrence Berkeley laboratory scientists recently announced results of innovative radiation experiments. The scientists watched cells repairing themselves after being exposed to low-level radiation. Here's the press release: 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
Here's a quote from the press release:
“Our data show that at lower doses of ionizing radiation, DNA repair mechanisms work much better than at higher doses,” says Mina Bissell, a world-renowned breast cancer researcher with Berkeley Lab’s Life Sciences Division. “This non-linear DNA damage response casts doubt on the general assumption that any amount of ionizing radiation is harmful and additive.”
Mina Bissell is a member of the National Academy of Sciences, and is known throughout the world for her breast cancer research. Her awards include being elected a Fellow of the National Academy of Sciences, a Fellow of the Royal Society of Chemistry, and further honors from the Curie Institute in France and the American Cancer Society. She has so many awards that Portugal has named an award FOR her: the Mina J Bissell award to a scientist who has transformed our perception of a topic.
Though the techniques were innovative, and the scientists very distinguished, these recent low-level radiation results are not actually surprising. From common sense, we would expect that a body could heal itself well from several low-dose radiation exposures, while having a harder time healing from a single high dose exposure. After all, we expect ourselves to heal after any number of skinned knees, but that says nothing about our ability to heal from stab wounds.
Why Is This A Big Deal? Well, The Official Theory of Radiation is Response is Strictly Linear
In other words, the official theory of radiation response is that a couple of skinned knees is the same as a stabbing.
Risks from low levels of radiation are generally assessed with the Linear No Threshold (LNT) theory. This theory states that the risks of cancer are in direct proportion to the amount of exposure, even for very small exposures. This methodology of risk assessment is supported by a series of reports called the BEIR reports: Biological Effects of Ionizing Radiation. BEIR I through BEIR VII have been issued under the auspices of the National Academy of Sciences. I include a link to the BEIR VII summary document from the National Academy.
Despite this heritage, the BEIR reports are controversial. For one thing, the assumption that there is no threshold for radiation damage is impossible to prove in a world where everyone is exposed to background radiation. For another thing, the linearity of damage at low levels always struck many scientists as unlikely. In general, small amounts of toxins are handled well by organisms, while large amounts can kill. The relationship between zero effect and lethal dose is not generally linear.
Or, as one of my friends put it: BEIR says that if 100 aspirins taken at once is lethal, and 100 men each take one aspirin apiece--one of those men is going to die. That would be a linear response to low dosage aspirin consumption.
Actually, BEIR VII waffles a bit at low dosages. Here's a quote from the summary:
There are two competing hypotheses to the linear no-threshold model. One is that low doses of radiation are more harmful than a linear, no-threshold model of effects would suggest. BEIR VII finds that the radiation health effects research, taken as a whole, does not support this hypothesis. The other hypothesis suggests that risks are smaller than predicted by the linear no-threshold model are nonexistent (sic), or that low doses of radiation may even be beneficial. The report concludes that the preponderance of information indicates that there will be some risk, even at low doses, although the risk is small.
Note that the report does not actually claim that the risks are linear at low doses, but merely that there is some risk though the risk is small.
If you would like to think about some painful consequences of LNT, I encourage you to listen to this podcast about Fukushima or read my blog post about it. Rod Adams invited me and Cal Abel to be on a podcast to discuss the very real question of when Fukushima evacuees could go home. I especially encourage you to read the comments on both the podcast and the blog post.
Following LNT Would Lead to Really Weird Cancer Therapies
"When all is said and done, there's a lot more said than done."
I have always followed the policy of attempting to look at what people do, rather than what they say. People still get dental x-rays. People move to Denver, where background radiation is high. More people move to Denver than move to the Mississippi delta, despite the low background radiation in Mississippi. But let's look at a stronger example.
Let's look at radiation therapy for cancer. Many people undergo radiation treatmentS. The plural is important.
Radiation oncologists know that the healthy flesh heals after a treatment, so treatments are spaced out: six weeks of three times a week, two months of twice a week, etc. I remember one man in my writing group who moved to Boston for two months to be treated. Why did he have to do this? Why didn't he just visit Boston, get one massive treatment, and come home to Vermont? Because, even at high doses, the body heals between treatments. There is a repair mechanism, as there is for everything else our body encounters.
Giving radiation therapy in one dose would hugely damage the surrounding tissues, compared to giving the same amount in smaller doses over a long time. Even at the relatively high doses of radiotherapy, response to one dose versus response to many doses is not linear. Wade Allison has an excellent description of the planning behind radiation therapy in his book, Radiation and Reason.
LNT and Small Doses
From low-level radiation exposure research at Berkeley to the standard methodologies of radiation oncology specialists to Fukushima...it seems to me that it is time to stop using LNT as the gold standard for assessing risk.
LNT is wrong and therefore will lead to incorrect results. Even BEIR doesn't really defend it, and yet it is the de facto law of the land.
A major tip of the hat to Rod Adams of Atomic Insights blog, for his post Lawrence Berkeley National Lab announces breakthrough study of low radiation dose effects