Posts Tagged ‘radiation’

Potential change of NRC radiation exposure standards is something to care about

September 27, 2015

The United States Nuclear Regulatory Commission (NRC) is considering a change to the standards for allowable exposure to ionizing radiation. If you live in the US, this is something to care about since these standards affect what certain operations are normally allowed to put into the environment, and what is considered safe for the general public rather than just workers at such facilities as nuclear power plants. The NRC is taking public comments on the matter until November 19, 2015.

The standards for exposure start with a model to describe the health risk of a given exposure to ionizing radiation. The model used currently by the NRC and all other regulatory bodies in the world is known as the Linear No Threshold (LNT) model. This model has the premise that any exposure is bad, and the risk to health grows proportionally with the exposure. The alternative being considered is the radiation hormesis model. This model supposes that a small exposure has a positive effect on health, but too large an exposure is detrimental. After researching this over the course of a week and a half, I have decided that this isn’t a good change, but may not be as bad as it sounds.

Scientific research into how ionizing radiation affects the human body has produced some results that support the LNT model and some that support hormesis. There doesn’t seem to be a scientific consensus on the matter, so I haven’t found a good explanation for the discrepancies. There are scientists who argue passionately in support of one conclusion or the other, and they don’t always acknowledge evidence that contradicts their position. This leaves me uncertain about which model is closer to correct.

The NRC is responsible for establishing regulations that keep workers and the public safe. Since there is research supporting both models, the one that assigns greater risk to radiation exposure should be the one used. It will error more on the side of caution and suggest limits closer to the natural environment. The model that does this is LNT, the one currently in use.

The NRC was also asked in the petitions to raise the acceptable exposure limit for the general public to be the same as workers who deal with ionizing radiation on the job, such as people who work at nuclear power plants. Given that there is research supporting LNT, that people have varying susceptibility to cancer, and that some people undergo radiation therapy that may increase their susceptibility, this seems like a change that is a risky experiment in proving hormesis. Even if LNT was not well supported and hormesis was, it is not clear to me that the petitioners have considered people who may be more susceptible or vulnerable to cancer from radiation exposure.

My research first led me to the website of Dr. Ian Fairlie, a scientist who has published several papers on the health effects of radiation in peer reviewed journals. He wrote a post specifically on the matter before the NRC. There, he mentions several peer reviewed papers to support his case, such as Leuraud et al 2015. That one found Leukemia was more common in radiation monitored workers. It is an important finding because such workers are exposed to low, but higher than background, amounts of ionizing radiation over long periods of time. The finding directly supports the LNT model. It is also interesting since the work was partly supported by the US government, including funding and researchers from the Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, and the Department of Health and Human Services.

However, Dr. Fairlie also mentions a paper on the rates of childhood Leukemia near nuclear power plants in Germany (Kaatsch et al, 2008). While it does show that childhood Leukemia is more than twice as common within 5km of the power plants, it does not establish the cause. The authors concluded that radiation may have little to do with it. The paper states that the natural background radiation over the areas studied is much greater than that released by the power plants, but it seems neither was measured for the study. It also mentions other possible causes of Leukemia; there is some evidence of a cause by infection (Alexander et al, 1998). This may seem to question the results of the Leuraud et al study, but that one had the advantage of data from personal dosimeters while the Kaatsch et al study does not. In any case, it looks like Kaatsch et al really isn’t good evidence in support of, or contrary to, the LNT model.

From there, my research jumped to the petition of Dr. Carol Marcus to the NRC that seems to have started the process of reconsidering LNT and considering hormesis as a replacement. In it, Dr. Marcus writes, “There has never been scientifically valid support for this LNT hypothesis”. To support this statement, she mentions only one report (“Evaluation of the Linear-Nonthreshold Dose-Response Model for Ionizing Radiation”, from the National Council on Radiation Protection and Measurements, 2001, executive summary link) on the matter and presents an attack on it by Dr. Zbigniew Jaworowski and Dr. Michael Walig√≥rski. This is evidently supposed to discredit all evidence and research that is consistent with LNT rather than hormesis, but it doesn’t refute the kind of empirical data seen in the Leuraud et al study, and likely others as well.

The existence of good peer reviewed science supporting LNT makes Dr. Marcus’s claim of no valid scientific support for LNT false. However, there is also such science in support of hormesis, so she might yet be proven to be supporting the correct model. I do not think the NRC should be making radiation monitored workers and the general public accept a potentially greater risk without a scientific consensus on the matter. I do not think it is proper even if a little more radiation might decrease the risk of so called solid cancers, as claimed by Dr. Marcus in the petition, if it also increases the risk of Leukemia. I think further research should be done on the effects of a total lack of ionizing radiation, including natural background radiation. This could be very helpful in better understanding the biological response to radiation.

In researching all this, I also looked into the background of the scientists. The really interesting one was hormesis proponent Dr. Jaworowski. In addition to publishing science on the effects of radiation in peer reviewed journals, he also published articles about or related to global warming. He claimed people should be more worried about an upcoming ice age, but published many of these articles without peer review, and they have been largely discredited. So far as I can tell, he was not a climatologist. He had a number of articles published in 21st Century Science and Technology, and Executive Intelligence Review; both are publications with ties to Lyndon LaRouche, which brings in some very strange and unusual politics.

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