Problems of current radiation standards and solution (Grant Meadows)

The Problems Of Current Radiation Standards And The Solution

Grant Meadows 1415 Engineering Drive, Madison, WI, 53706, University of Wisconsin-Madison, gmeadows234@gmail.com The current safety regulations of low-dose ionizing radiation exposure are erroneous. The linear nothreshold model (LNT), proposed in the 1950s and accepted as the science behind regulation protections, now serves as an obstacle towards progress, rather than a tool of the nuclear community. The LNT model should be replaced by the more accurate model, called hormesis. By adopting hormesis, a threshold model of acute and chronic radiation exposure can be instituted, leading to immeasurable gain for millions of people.

I. THE HISTORY AND PROBLEMS OF CURRENT STANDARDS In 1956, the Biological Effects of Atomic Radiation (BEAR) Committee of the National Academy of Sciences proposed using the linear no-threshold model as the basis for radiation safety standards. This announcement was a significant change in the underlying science of radiation safety, which had used a threshold model for decades before. After the BEAR Committee made their recommendations, the LNT model was adopted, and has remained in place ever since then. The linear no-threshold model stipulates that any ionizing radiation absorbed by living organisms increases the rate of mutations, which increases the chance of developing cancer from the mutation. For smaller doses of ionizing radiation, there is a smaller chance of cancer, with the likelihood of cancer growing proportionally from zero. [1] The implications of the BEAR I report were significant. All regulatory agencies follow the LNT model, such as the Nuclear Regulatory Commission (NRC) and the Environmental Protection Agency. [2], [3] The circumstances surrounding this report were later found to be suspicious, to say the least. There were multiple letters exchanged that suggested the members of the BEAR I report were acting in their own self-interest when they declared the LNT to be the most accurate model for low-dose radiation exposure. For example, several members said “Let us be honest with ourselves – we are both interested in genetics research, and for the sake of it, we are willing to stretch a point when necessary” when referring to the LNT-inferred risks of radiation exposure. 1 [4] Although the faults of the first BEAR report may not seem like a huge issue, all subsequent reports have cited the first one, leading to a propagation of conflictions of interest. (Later reports are

called the Biologic Effects of Ionizing Radiation [BEIR] reports.) Even the newest BEIR Report, BEIR VII, references the original report. [5] The LNT model traces its roots to the 1920s, when biologists were developing theories for the causes of evolution. The first discovery was by Hermann Muller, who discovered that x-rays can cause mutations in fruit flies. He believed that radiation mutations would explain evolution. Many decades later, however, it was shown that the endogenous metabolism was the cause for most mutations and genetic evolution, rather than radiation sources. Several mathematical theories were developed to create a basis for the biological effect that was observed.

The evidence used to show mutations of fruit fly germ cells was based on high doses of radiation exposure.

There were three studies right around 1930 that Muller used to explain the LNT model. However, the lowest cumulative dose out of the three studies was 2.85 Gray (Gy), about an order of magnitude higher than the threshold exposure to be advocated for in later sections.

[1] The current standards for radiation protection in nuclear energy facilities are dictated by the Nuclear Regulatory Commission (NRC). The NRC states that the maximum dose equivalent, measured in Sieverts (Sv), allowed on a yearly basis for the public is one millisievert (mSv). [6] In addition, in compliance with the consequences of the LNT model, the NRC dictates that the nuclear industry follow the philosophy of As Low As Reasonably Achievable (ALARA) exposure to ionizing radiation, creating an incentive to always reduce radiation exposure in medical radiation and nuclear facilities. [2] There are many problems with the linear no-threshold model and its implications. With its basic definition, when applied to other areas of life, one might pause and consider the logic of its arguments. For example, if the LNT model was applied to jumping out of buildings, then if a jump of 100 feet caused certain death, a jump of 1 foot, with 1/100 the height, should be 1/100 as toxic.

Therefore, if someone jumps out of a building one foot off the ground, they have 1/100 a chance of dying. Does this make sense? Nevertheless, despite the simplicity of these arguments, the linear no-threshold model is based on this logic.

Before the LNT model was developed, the threshold model of radiation exposure was used for protection. It was stated that below a quantitative amount of radiation

exposure, there was little to no risk of negative consequences, such as developing cancer. [1] Now with the LNT model used as the overlying assumption for radiation exposure estimates, one would think there would be conclusive proof that the model works, sixty years after it was first recommended. Nevertheless, there are many studies that claim it is true, or not. There are two primary ways of estimating the effects of low-dose ionizing exposure to living beings, epidemiology and biology studies. For low-dose exposure research, epidemiology is usually the study of statistical trends related to excess cancer rates above a control population, and their corresponding radiation exposure rates. For high doses of exposure, the risk of cancer and other effects are well known, using epidemiology. Unfortunately, for low dose exposures, the number of people needed for studies increases exponentially. The reason why is because there is decreasing excess risk above the control population at lower and lower doses. For epidemiology alone, this single fact has kept the LNT model from being conclusively disproved. [7] Although the error bars are too large to notice trends at low doses, researchers have used the observed data points to draw trend lines in epidemiology studies. For example, the most important LNT study is the Atomic Bomb Survivor study, a study of the radiation exposures and their associated cancer incidences. Although the error bars are too large to create definite proof of LNT or other models, for many years, this model claimed to prove the existence of LNT, rather than other models. Recently, however, with new data, the study has shown a curve of cancerous risk that corresponds to a threshold or hormesis model (hormesis is explained below). [8] Two of the three models for low-dose radiation exposure risks, the LNT and threshold models, have been explained. However, the third model is the most accurate model. It is called hormesis. Hormesis is a model in that low doses of radiation exposure help reduce the chance of cancer. The idea stems from the increased action of the immune system against cancerous mutations caused by ionizing radiation. There are many epidemiological studies that point towards this model. For example, in the Nuclear Shipyard Worker Study, comparing about 70,000 workers total, the total mortality and cancer rates of the exposed workers was lower than the control population.

[9] Another study, comparing people affected by an explosion of a radioactive tank in the USSR with a control group in the same area, found no increase in mortality, and no trends of mortality compared to radiation dosage.

This accident happened in 1957, and is commonly called the Mayak study. [10] Two more studies are worth mentioning. The first was an accident in Taiwan, where Cobalt-60 was mixed into the steel later used to construct an apartment building. For adults ages 30 and older, there was no increase in cancers corresponding to radiation dose. [11] Finally, for 100 years, British radiologists

recorded their incidence of cancer, and the later data, from 1955 to 1979, there was no increase in cancer rates above the general population. Although rates of cancer were higher in years earlier than 1955, the dose rates were also most likely much higher. [12] All of these studies show that epidemiology points toward hormesis more than LNT, an important fact to remember.

As explained previously, although epidemiology can be useful, it has its limitations, especially in low-dose radiation exposure effects. Therefore, when making important policy decisions affecting hundreds of millions of people, it is best to use the biology studies in this field.

There are many biology studies demonstrating hormesis, [13], [14], [15] with a total of six in this article. If more peer-reviewed literature supporting hormesis is desired, the website x-lnt.org serves as a resource for many of these papers. Some studies look at the activation of the immune system from low-dose radiation at the cellular level. [13] Other studies look at the implanted cancer cells in rats and how low-dose irradiation increases the activity of the immune system, leading to a suppression of these cancer cells. [14] Still other studies point to the importance of the immune system in suppressing cancer, [15] even in human clinical trials. [16] II. THE SOLUTION FOR RADIATION STANDARDS With this mounting body of evidence, it is our responsibility as nuclear scientists or engineers to act, as the public trusts us to make informed decisions on their behalf. For making nuclear policy, it is important to state a threshold number for exposure. Based on the doseresponse activities of the immune system, the threshold should be set at 100 mGy, and for photonic ionizing exposure, this threshold becomes 100 mSv of dose effectiveness. Creating a threshold number is often the most difficult part of setting public policy, but this number was not pulled out of thin air. There are four cited studies in this paper alone, which demonstrate 100 mSv to be a bit under, or at the peak effectiveness of the hormetic response. By staying at or under the peak immune system activity, a buffer is created for those with weakened immune systems. This threshold number also has epidemiological support. [16], [17], [18], [19] Talking to nuclear engineering students and professors about this issue is troubling. The two most common responses heard when stressing the need for policy change is uncertainty and indifference towards this important issue. Uncertainty is the first issue needing to be addressed. The LNT model never had a strong basis for its use. The first committee recommending its use, the BEAR I Committee, used evidence of high dose exposure risks to draw a line to create a model of low dose risks.

[1] They also had conflicts of interest when proposing the LNT model, as they wanted money for genetics research.

[4] The hormesis model, on the other hand, has both epidemiological and solid biological evidence, as previously stated. Switching to a hormesis model is not a radical change in policy now. For example, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) now warns against the use of the LNT model for calculating low-dose radiation risks, an implicit acknowledgment of a threshold model. [20] Although future research would help provide even more evidence of hormesis, it is not necessary. The reason why is that by waiting ten or twenty years for more research before changing models, more people will be affected by air pollution, cancer, and a host of other factors, who could otherwise be saved by an increase use of nuclear power and a change in medical practices, topics soon to be addressed below. By not making a decision in policy, the decision is made to keep the status quo.

The second issue is indifference towards the topic. In both the Medical and Nuclear Industries, there would be dramatic improvements as a result of this policy change.

Although all the benefits cannot be listed from using the hormesis model, the most important ones will be mentioned in this article. In the nuclear industry, the impacts would be huge. There is always Fear, Uncertainty and Doubt (FUD) when speaking of ionizing radiation, and the LNT model has created this mindset, thanks to the idea of no safe threshold. Any level of radiation exposure can create cancer, according to the LNT, leaving people to wonder what level is safe. On many public forums, like Wikipedia, opponents of nuclear power cite safety and accidents as a concern for using nuclear power. The arguments about safety would be more simple and bring less FUD to social debates with the hormesis model. For example, in the Nuclear Power article on Wikipedia, the 2011 Fukushima Nuclear Accident is predicted to cause up to 1000 deaths. In the same article, the 1986 Chernobyl Nuclear Accident is expected to cause up to 25,000 deaths. [21] These numbers are believable and can be troubling to uninformed citizens, causing more FUD. However, they can only be argued by some scientists because of the LNT model. To emphasize the impacts of these numbers on the nuclear industry, as a result of the 2011 Fukushima accident, Germany decided to phase out all nuclear power, despite the fact that UNSCEAR has declared that the accident should cause no deaths. This political decision was directly caused by the Fukushima accident. [22] In another example, fear of radiation from the Fukushima accident caused a dramatic rise in the death rate of elderly people in the area around Fukushima.

During the accident, the LNT model directly caused about 200 deaths. [23] Using the LNT model directly caused deaths, wherein a hormesis model would have saved lives.

Another impact of switching to the hormesis model would be nuclear waste management. The Yucca Mountain repository was a failure as a permanent storage solution for nuclear waste. One of the reasons was the

usage of the LNT model. The EPA originally proposed a 0.15 mSv limit to public exposure, then added to it, by establishing a one mSv limit after 10,000 years. This change was forced by the National Academy of Sciences, which objected to the EPA’s original estimation, and prevented the repository from being approved until it was cut in funding. [24] Under a hormesis model of 100 mSv threshold exposure, there would have been no confusion in radiation limits. Most likely, the repository would have been operational long before a change in presidential administrations was able to affect budgeting.

There are many lives to be saved by switching to the hormesis model. One impact of the hormesis model would be reduced costs for the nuclear power industry, as the current NRC radiation exposure standards would increase to 100 mSv a year, versus the one mSv currently used. Although there are many economic factors involved in running nuclear plants, reducing costs for the industry would encourage expansion. The consequences of expansion of the nuclear industry would be vast and farreaching. The nuclear power industry has one of the lowest death rates per kilowatt-hour generated, according to Forbes. [25] If expanded, it would replace part of the fossil fuel industry, which includes coal power generation. If all of the coal in the United States was replaced with nuclear power, about 10,000 people would be saved every year from death.

The medical industry would also benefit from switching to a hormesis model. The first of many benefits would come in the form of better diagnoses of diseases.

With the LNT model and ALARA philosophy, lower doses of radiation are preferred for CT and other ionizing radiation-based scans. However, the lower dose scans can create misdiagnoses of medical issues, creating huge problems for patients down the line. [26] Finally, the most important benefit to the health industry would be the use of hormesis for treating cancer. Using the hormesis model of radiation exposure could allow for low-dose total-body irradiation, preventing cancer and improving the lives of millions of people.

III. CONCLUSION The LNT model is the basis for current safety regulations, and is well-proven at high levels of ionizing radiation exposure. However, its validity at low levels of exposure was never verified, and the first committee that proposed its use had many issues of conflicts of interest.

In a nutshell, it never had a strong foundation for its use, and without a strong foundation, it can be easily repealed.

On the other hand, the model of hormesis has both epidemiological and biological evidence, and it is the duty of the nuclear community to act on this evidence in representing the public before regulatory agencies. The change to the hormesis model will bring huge

improvements to the nuclear and medical industries, and hence the world.

ENDNOTES 1

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