In spite of the science, governments continue to use the LNT model
Radiation Hormesis Gets Another Look
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In late June the Nuclear Regulatory Commission (NRC) announced that three petitioners, a radiation-health organization, a health physicist, and a professor of radiation oncology at the University of California, Los Angeles, asked that it amend its radiation protection standards to change the basis of those regulations from the linear-no-threshold (LNT) model to the hormesis model. The NRC explained, “The radiation hormesis model provides that exposure of the human body to low levels of ionizing radiation is beneficial and protects the human body against deleterious effects of high levels of radiation.” (1)
The agency will be accepting comments on the matter until September 6.
When environmental toxicologist Edward Calabrese in the School of Public Health and Health Science at the University of Massachusetts heard this news he felt ‘a vindication of my 30-year career, in many ways.’ Calabrese recalls, “At Umass we have done a lot in terms of scientific leadership, publishing nearly 200 papers on the topic and encouraging others to test their own hypothesis. The field has really matured. In 2014 alone, there were 6,500 citations on many different topics including microbiology, arthritis, mitigating heart attacks, stroke, cancer therapies, preparing for organ transplantation, enhancing stem cell function and enhancing plant productivity. It’s very exciting how diverse the research has become.” (1)
The concept of hormesis has not escaped its share of controversy. Some researchers question whether scientists have developed adequate methods for distinguishing when a beneficial effect ends and a toxic one begins. The exact threshold for when a toxic reaction starts may vary by individual, making it difficult to use hormesis as a basis for drug therapies. Skepticism arises, too, when the basic concept is extended to ionizing radiation, such as x-rays, for which low doses have been shown to have beneficial effects on healthy lab animals. Various scientific advisory bodies, however, have rejected radiation as unsafe for humans even at the lowest levels. (2)
The linear-no-threshold assumption exists with ‘assumption’ as the all-important word that needs to be taken literally. While no one disputes that high doses of radiation cause harm, no one has proof that low levels cause harm. Surprisingly, the scientists and government bodies that adhere to the LNT assumption will tell you that no proof of harm at low levels is even possible because the risk is too low to measure statistically. In the absence of proof, they say, the only prudent course is to play it safe by assuming that low levels or radiation cause harm, reports Lawrence Solomon. (3)
Yet, here are some examples:
- - T. D. Luckey estimates that there are more than 2,000 published research papers showing enhanced health in animals and humans from low dose ionizing radiation. (4)
- - A book by Charles L. Sanders titled Radiation Hormesis and the Linear-No-Threshold Assumption reports on a case of ‘an almost perfect study in a human population that demonstrates the highly significant protective effects of near-continuous exposure to gamma radiation.’ This case involved more than 180 apartment buildings that had been constructed in Taiwan in the early 1980s using recycled steel that was subsequently discovered to have been contaminated with radioactive cobalt-60. The 10,000 people who were housed there received large doses of radiation over a period of 9 to 20 years that, according to LNT theory, should have led to a total of 302 cancer deaths over the 1983-2003 period studied, 232 of which would have been ordinarily expected had no radiation exposure occurred, with the additional 70 stemming from the exposure. To the researchers’ surprise, however, only seven cancer deaths were found, 225 fewer than would have occurred had the buildings been free of radiation. Instead of radiation increasing the death toll by 30%, it may have reduced the death toll by a staggering 97%. The number of birth defects among children born in this radioactive environment also confounded LNT theory. Instead of 48 defects expected, just three occurred.
- - Researchers Maurice Tubiana and colleagues report that the LNT has resulted in medical, economic and other societal harm.. Advances in radiation biology in the last two decades, and the discovery of defenses against carcinogenesis render the LNT obsolete. (5)
In industrialized countries, we now treat more than one million patients with radiotherapy, including 50 percent of all US cancer patients, with obvious positive results. Literally hundred of thousands of medical workers exposed to frequent low-level radiation have experienced similar positive health benefits. (6)
In spite of the science, governments continue to use the LNT model. Misuse of this model has produced spending in excess of $1 trillion in the United States alone for negligible health benefits just for governmental environmental cleanup programs, while truly significant measures that would protect public health remain unfunded. It’s long overdue that serious reconsideration be given to the LNT model.
1. Janet Lathrop, “Environmental toxicologist hopes hormesis hypothesis may be acknowledged by US regulatory action,” umass.edu, July 21, 2015
2. Mark P. Mattson, “What doesn’t kill you”, Scientific American, 313, 41, July 2015
3. Lawrence Solomon, “Radiation’s benefits,” Financial Post, September 2010
4. Arthur B. Robinson, Access to Energy, February 2011
5. Maurice Tubiana et al., “The linear-no-threshold relationship is inconsistent with radiation biologic and experimental data,” Radiology, 251, 6, 2009
6. Jay Lehr, “Low-level radiation benefits health,” Environment & Climate News, August 2011