For many years, I have been involved in discussions with a dedicated group of scientists and engineers who question the basis of our current radiation control limits. According to the way that these people, mostly member of an organization called Radiation, Science and Health, interpret the results of hundreds of carefully conducted studies, the Linear, No Threshold (LNT) model is completely wrong.
(Note: Please do not let the ugly RSH web site deter you. It hosts some fine science papers and commentary; it is too bad that the web master is more engineer than web designer.)
For those of you who are not familiar with the debate that is raging in certain circles, the LNT model assumes that there is no such thing as a safe level of radiation. The model draws a straight line from the hazards that can be measured at very high doses and assumes that the line goes all the way to the 0, 0 point on a risk versus dose graph.
Under the LNT model, risk is not zero until dose is zero. This is the model that is used to predict scary numbers of eventual cancer deaths in a very large population of people who receive minimal doses. The technique is called “collective dose”. It is particularly galling to many scientists to see it being used to predict large numbers of deaths from relatively benign causes.
Even with a very tiny, non zero risk number, if you multiply that number by an exposed population numbering in the tens of millions, you can end up with thousands of eventual deaths. My friends from RSH like to use an aspirin analogy to describe how frustratingly unscientific such a curve is if applied against other hazards.
The aspirin analogy goes something like this – a single person taking a whole bottle of 500 aspirin tablets at one time has a high probability of death. That same person consuming the bottle’s contents over a 500 day period is likely to have a positive health effect. The original bottle can also be consumed safely in a short period if the pills are given to 500 people. If the pills are distributed to 1000 or 10,000 people it would be absurd to compute that the bottle of pills could possibly lead to harm to any one of the members of the group.
The economic implications of using the LNT as the basis for regulation are incredibly large. For example, much of the money (nearly $10 billion so far) spent to characterize Yucca Mountain has been done to provide the scientific basis for meeting a 15 mrem per year exposure limit to the most exposed person. In a world where average background levels of radiation exposure exceed 300 mrem per year for some people and 7000 mrem per year for others, it is crazily expensive to design a system that can limit accidental exposures from used nuclear fuel to less than 15 mrem per year for 10,000 to 1,000,000 years.
The campaigners against the LNT keep hitting brick walls erected by bureaucrats whose careers have been built on the idea that there is no such thing as a safe dose and they have also been stymied by those companies who have captured the lion’s share of the billions spent in excessive protection efforts and clean ups. Never forget that “one man’s cost is another man’s revenue.”
The LNT supporters are facing increasing questioning because they do not have a scientific leg to stand on. A recent article in Spiegel Online discussed some of the recent efforts to determine just how dangerous radiation is for humans. The article is a two part exposition titled Nuclear Exaggeration: Is Atomic Radiation as Dangerous as We Thought? It is well worth a read to find out how curious researchers are finding out that many of the myths and assumptions are simply not true.
For example, the article states that there is simply no evidence at all of an increase in the normal rate of birth defects from the 87,000 member cohort of Hiroshima victims that has been intensively studied for more than 60 years. The article also provides some very intriguing commentary about the effects of exposure to a group of Soviet era plutonium workers. Go and read it now.
Please do not get me wrong, I know that radiation in sufficient doses can kill you. I also know, however, that there are doses where the hazard is low enough to be below concern and I am pretty well convinced that there is a range of doses which can provide beneficial stimulus response. According to some of my scientific friends, efforts to reduce doses to zero can actually be hazardous to your health by removing a necessary component of healthy, natural living. After all, the Earth is a naturally radioactive place, but humans are pretty well adapted to living here.
What do you think? Is it time to call loudly for reform of radiation protection measures and especially for a complete repudiation of the idea of applying collective dose computations in license applications and in accident analysis?