It's Time for a New Low-Dose-Radiation Risk Assessment Paradigm—One that Acknowledges Hormesis

Scott, Bobby R.

doi:10.2203/dose-response.07-005.scott

Cited by 78 publications

(70 citation statements)

References 71 publications

(109 reference statements)

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“…Through evolution, mammalian life forms have developed natural cancer preventative processes (chemically and biologically regulated) that are stimulated by low doses and dose rates of sparsely ionizing forms of radiation (e.g., x rays, gamma rays, beta particles) (Parsons 2001(Parsons , 2003Sakai et al 2003;Liu 2007). Low doses and dose rates of these radiations stimulate protective intercellular and intracellular signaling that leads to activated natural protection (ANP) against cancer and other genomic-instability-associated diseases (Olivieri et al 1984;Mitchel et al 1999;Sakai et al 2006;Mitchel 2007;Scott 2007a). The protective signaling appears to be a generalized response to mild stress above an individual-specific threshold level (Scott 2005).…”

Section: Introductionmentioning

confidence: 99%

Low-Dose-Radiation Stimulated Natural Chemical and Biological Protection against Lung Cancer

Scott

2008

Dose-Response

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Research is being conducted world-wide related to chemoprevention of future lung cancer among smokers. The fact that low doses and dose rates of some sparsely ionizing forms of radiation (e.g., x rays, gamma rays, and beta radiation) stimulate transient natural chemical and biological protection against cancer in high-risk individuals is little known. The cancer preventative properties relate to radiation adaptive response (radiation hormesis) and involve stimulated protective biological signaling (a mild stress response). The biological processes associated with the protective signaling are now better understood and include: increased availability of efficient DNA double-strand break repair (p53-related and in competition with normal apoptosis), stimulated auxiliary apoptosis of aberrant cells (presumed p53-independent), and stimulated protective immune functions. This system of low-dose radiation activated natural protection (ANP) requires an individual-specific threshold level of mild stress and when invoked can efficiently prevent the occurrence of cancers as well as other genomic-instability-associated diseases. In this paper, low, essentially harmless doses of gamma rays spread over an extended period are shown via use of a biological-based, hormetic relative risk (HRR) model to be highly efficient in preventing lung cancer induction by alpha radiation from inhaled plutonium.

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Section: Introductionmentioning

confidence: 99%

Low-Dose-Radiation Stimulated Natural Chemical and Biological Protection against Lung Cancer

Scott

2008

Dose-Response

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“…The topics of the threshold, hormesis and DDREF are interrelated with the linear no-threshold theory (LNT). Hormesis and LNT are considered controversial by many scientists; discussion is in [3][4][5][6][7][8]. The LNT is corroborated by the following arguments: the more tracks go through a cell nucleus, the more DNA damage would result and the higher the risk of malignant transformation would be.…”

Section: Arguments Against Linear No-threshold Theory (Lnt)mentioning

confidence: 99%

“…Hormesis cannot be used in the radiation safety regulations without compelling experimental evidence from largescale animal experiments using different species. Epidemiological studies in humans would be less informative because of the relatively low sensitivity and biases [7,81], in particular, dose-dependent quality of medical surveillance and more frequent self-reporting of people with higher doses (self-selection bias). The dose-response …”

Section: On the Dose-response Relationshipmentioning

confidence: 99%

Biological Effectiveness of Ionizing Radiation: Acute vs. Protracted Exposures

2016

J Environ Stud

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This letter refers to the current discussion around re-evaluation of the dose and dose rate effectiveness factor (DDREF) equal to 2, presently recommended by the International Commission on Radiological Protection. The topics of the threshold, hormesis and DDREF are interrelated with the linear no-threshold theory (LNT). The LNT does not take into account that DNA damage and repair are permanent processes in dynamic equilibrium. Given the evolutionary prerequisite of best fitness, it would be reasonable to assume that living organisms have been adapted by the natural selection to the background levels of ionizing radiation. Accordingly, there must be an optimal exposure level, as it is for many environmental factors. Several studies cited in the literature in support of the LNT and lowering of the DDREF down to 1 are discussed here. In the author's opinion, the dose-effect relationships with non-neoplastic diseases found in certain exposed populations call in question dose-effect relationships with cancer. Self-selection and other biases in epidemiological studies are discussed. The dose-response relationships should be clarified in largescale experiments involving different animal species. In conclusion, the LNT and under-estimation of DDREF tend to exaggerate radiationrelated health risks at low radiation doses and dose rates. Arguments against Linear No-Threshold Theory (LNT)Radiation-related cancer risk estimates have been primarily based on the data from atomic bomb survivors. To adjust the risk estimates at acute exposures to low dose and continuous (low dose rate) exposures, a dose and dose rate effectiveness factor (DDREF) is used [1]. This letter refers to the discussion around re-evaluation of the DDREF value equal to 2, currently recommended by the International Commission on Radiological Protection (ICRP) [2]. The topics of the threshold, hormesis and DDREF are interrelated with the linear no-threshold theory (LNT). Hormesis and LNT are considered controversial by many scientists; discussion is in [3][4][5][6][7][8]. The LNT is corroborated by the following arguments: the more tracks go through a cell nucleus, the more DNA damage would result and the higher the risk of malignant transformation would be. "Decreasing the number of damaged cells by a factor of 10 would be expected to decrease the biological response by the same factor of 10" [9]. This concept does not take into account that DNA damage and repair are permanent processes in dynamic equilibrium. Given the evolutionary prerequisite of best fitness, it would be reasonable to assume that living organisms have been adapted by the natural selection to background levels of ionizing radiation [10]. Accordingly, there must be an optimal exposure level, as it is for many environmental factors: visible and ultraviolet light, different chemical elements and compounds [11], as well as the products from radiolysis of water [12]. Evolutionary adaptation to a changing environmental factor would lag behind its current value and correspond to some ...

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“…When the precautionary principle is taken too far, it may adversely affect human health if it reduces exposures below those at which beneficial adaptive responses are induced (9). The "lower is always better" mantra of regulatory agencies will often counter the goal of enhancing public health (10,11).…”

Section: Commentarymentioning

confidence: 99%

Improving the scientific foundations for estimating health risks from the Fukushima incident

Calabrese

2011

Proc. Natl. Acad. Sci. U.S.A.

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It's Time for a New Low-Dose-Radiation Risk Assessment Paradigm—One that Acknowledges Hormesis

Cited by 78 publications

References 71 publications

Low-Dose-Radiation Stimulated Natural Chemical and Biological Protection against Lung Cancer

Low-Dose-Radiation Stimulated Natural Chemical and Biological Protection against Lung Cancer

Biological Effectiveness of Ionizing Radiation: Acute vs. Protracted Exposures

Improving the scientific foundations for estimating health risks from the Fukushima incident

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