Dr. Ron Mitchel is a Canadian scientist with a PhD in biochemistry who has been studying the biological effects of low dose radiation on living creatures for the past 35 years. In January 2013, he gave a talk to the Pittsburgh chapter of the American Nuclear Society on biological responses to low dose radiation. Dr. Rita Bowser introduced him to the audience. Though the production quality of this video is not the greatest, the audio is good and the video is clear enough for effective information transmittal.
I’m not sure how I missed this or why it has been watched by only one person per day in the 11 months it has been posted. It is FAR more important for people to spend the next 50 minutes watching this informative presentation instead of watching another episode of Survivor, one quarter of a college football bowl game, or an NCIS rerun.
Here are some highlights of the presentation, in case you are still wondering if it is worth your time to watch.
During her introduction, Dr. Bowser told an interesting tale about her time working with the Mescalero Apache Indian tribe at a place called Inn of the Mountain Gods. That is in the foothills of the mountains near Alamogordo, NM. It is near the Trinity site where the first atomic bomb was tested without telling the Indians in advance of the test. Several of the elders of the tribe described to Dr. Bowser their memories of the day when they saw the incredibly bright light and heard the thunderous roar. It was a searing memory.
While Dr. Bowser lived and worked on the reservation, she taught the Mescalero Apaches about radiation and nuclear energy so that they could take advantage of some of the career opportunities offered by the local nuclear industry. As part of that training, she gave them some demonstrations in which she showed Geiger counter responses to naturally occurring radiation sources.
One of the more interesting objects she measured was the large turquoise belt buckle that the chief always wore. She described how it eased concerns when the chief told everyone that he was not worried, even though the Geiger counter showed a considerable count rate from his constantly-worn belt buckle.
Dr. Bowser ended the introduction by describing how the tribal language had no direct translation for radiation, so the Mescalero Apaches came up with the following phrase in their native tongue – “hot rocks that shoot ghost bullets.” She then asked Dr. Mitchel to describe how his research has answered the question, “Are the ghost bullets harmful, helpful, or do they simply pass right through us?”
Dr. Mitchel told the audience that radiation exposure is one of many possible changes in an organism’s environment that creates a stress. The basic rule in biology in a changing environment is “Adapt or Die.”
Aside: That phrase reminded me of the phrase my colleagues who were Marines often repeated, “That which does not kill you, makes you stronger.” I have always admired the resilience of my Marine Corps colleagues. End Aside.
At about minute 17 in the video, Dr. Mitchel talks to a slide that describes “adaptive response.” That is a characteristic where exposure of cells or organisms to radiation at a low dose and low dose rate (or to any other mild stress) induces mechanisms that protect against the detrimental effects of other events or agents, including radiation.
He then provides about a half an hour’s worth of specific, experimental examples in which adaptive responses have been measured in a variety of organisms. He points out how the effects differ depending on the presence and the magnitude of other induces stressors.
Somewhere around minute 42, he starts to explain why he has serious disagreements with the assumptions and methods used by epidemiologists that have made assumptions about the health effects of low dose radiation based upon their assumed “gold standard” population of atomic bomb survivors. He reminded the audience how the effects his experiments have measured were dependent on controlling for the additional stressors in the environment.
He asked “Is A-bomb survivor data the gold standard for radiation response?” In answer to his own question he said, “I cannot think of a population that is more stressed. They had an A-bomb dropped on their heads.” His slide included the following bullet points.
- Exposed to radiation
- Exposed to physical trauma from the blast
- Exposed to burns from blast
- No food; nutritional stress
- No housing or blankets; thermal stress
He left out a few other stressors that must have affected the population, notably the fact that they were most likely subject to depression from having just lost a lengthy war, and the fact that they were labeled “hibakusha” and ostracized as a result of their classification as atomic bomb victims.
Dr. Mitchel concluded with a slide titled “Implications for radiation protection.” While talking to that slide he emphasized that at low doses, from a biological point of view, all of the basic LNT assumptions are WRONG. (Emphasis in the original.)
The LNT assumes that dose is a surrogate for risk and that every increase in dose results in an increase in risk. As his experimental data show, some doses actually reduce risk, especially in the case where a low dose is given before a substantially higher dose.
The LNT assumes that doses are additive, but that is again belied by the fact that there is strong evidence of prophylactic doses that stimulate defenses against later doses. He pointed out that tissue weighting factors cannot be determined independent of dose and that radiation weighting factors that convert deposited energy (Grays) into risk (Sieverts) have no meaning at low dose.
He recommends a new approach to radiation protection at low dose. In response to a question from the audience, he made a statement that seemed to cause quite a bit of consternation in the audience because it so strongly contradicted all previous training and indoctrination. According to Dr. Mitchel’s research, anything below about 1 mGy/minute is a low dose.
People with a moderate facility with arithmetic can readily compute that 1 mGy/min of Co-60 gamma radiation results in an accumulated dose of 60 mSv/hour (6 rem/hr). By current radiation protection standards, a radiation worker would exceed his annual limit of 20 mSv (2 rem) in just 20 minutes at that rate.
As Dr. Mitchel’s work and presentation demonstrates, our current radiation protection limits are not even within orders of magnitude of limits that would be determined based on actual biological risk determination.