Radiation hormesis

Alternative assumptions for the extrapolation of the cancer risk vs. radiation dose to low-dose levels, given a known risk at a high dose: supra-linearity (A), linear (B), linear-quadratic (C) and hormesis (D).

Radiation hormesis is the hypothesis that low doses of ionizing radiation (within the region of and just above natural background levels) are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation. The reserve repair mechanisms are hypothesized to be sufficiently effective when stimulated as to not only cancel the detrimental effects of ionizing radiation but also inhibit disease not related to radiation exposure (see hormesis).[1][2][3][4] It has been a mainstream concept since at least 2009.[5][unreliable source?]

While the effects of high and acute doses of ionising radiation are easily observed and understood in humans (e.g. Japanese atomic bomb survivors), the effects of low-level radiation are very difficult to observe and highly controversial. This is because the baseline cancer rate is already very high and the risk of developing cancer fluctuates 40% because of individual life style and environmental effects,[6][7] obscuring the subtle effects of low-level radiation. An acute effective dose of 100 millisieverts may increase cancer risk by ~0.8%. However, children are particularly sensitive to radioactivity, with childhood leukemias and other cancers increasing even within natural and man-made background radiation levels (under 4 mSv cumulative with 1 mSv being an average annual dose from terrestrial and cosmic radiation, excluding radon which primarily doses the lung).[8][9] There is limited evidence that exposures around this dose level will cause negative subclinical health impacts to neural development.[10] Students born in regions of higher Chernobyl fallout performed worse in secondary school, particularly in mathematics. "Damage is accentuated within families (i.e., siblings comparison) and among children born to parents with low education..." who often don't have the resources to overcome this additional health challenge.[11]

Hormesis remains largely unknown to the public. Government and regulatory bodies disagree on the existence of radiation hormesis and research points to the "severe problems and limitations" with the use of hormesis in general as the "principal dose-response default assumption in a risk assessment process charged with ensuring public health protection."[12]

Quoting results from a literature database research, the Académie des Sciences – Académie nationale de Médecine (French Academy of SciencesNational Academy of Medicine) stated in their 2005 report concerning the effects of low-level radiation that many laboratory studies have observed radiation hormesis.[13][14] However, they cautioned that it is not yet known if radiation hormesis occurs outside the laboratory, or in humans.[15]

Reports by the United States National Research Council and the National Council on Radiation Protection and Measurements and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) argue[16] that there is no evidence for hormesis in humans and in the case of the National Research Council hormesis is outright rejected as a possibility.[17] Therefore, estimating linear no-threshold model (LNT) continues to be the model generally used by regulatory agencies for human radiation exposure.

  1. ^ Calabrese, Edward J; Baldwin, Linda A (2003). "Toxicology rethinks its central belief". Nature. 421 (6924): 691–92. Bibcode:2003Natur.421..691C. doi:10.1038/421691a. PMID 12610596. S2CID 4419048.
  2. ^ Feinendegen, L E (2005). "Evidence for beneficial low level radiation effects and radiation hormesis". British Journal of Radiology. 78 (925): 3–7. doi:10.1259/bjr/63353075. PMID 15673519.
  3. ^ Kaiser, J. (2003). "HORMESIS: Sipping from a Poisoned Chalice". Science. 302 (5644): 376–79. doi:10.1126/science.302.5644.376. PMID 14563981. S2CID 58523840.
  4. ^ Wolff, Sheldon (1998). "The Adaptive Response in Radiobiology: Evolving Insights and Implications". Environmental Health Perspectives. 106 (Suppl 1): 277–83. doi:10.2307/3433927. JSTOR 3433927. PMC 1533272. PMID 9539019.
  5. ^ Allison, Wade (2009). Radiation and Reason: The Impact of Science on a Culture of Fear. York, England: York Publishing Services. p. 2. ISBN 978-0-9562756-1-5.
  6. ^ "WHO Cancer Fact sheet N°297". Retrieved 2011-04-29.
  7. ^ Parkin, D M; Boyd, L; Walker, L C (2011). "16. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010". British Journal of Cancer. 105 (Suppl 2): S77–81. doi:10.1038/bjc.2011.489. PMC 3252065. PMID 22158327.
  8. ^ Kendall; et al. (January 2013). "A record-based case-control study of natural background radiation and the incidence of childhood leukaemia and other cancers in Great Britain during 1980–2006". Leukemia. 27 (1): 3–9. doi:10.1038/leu.2012.151. PMC 3998763. PMID 22766784.
  9. ^ Spycher BD, Lupatsch JE, Zwahlen M, Röösli M, Niggli F, Grotzer MA, Rischewski J, Egger M, Kuehni CE (June 2015). "Background ionizing radiation and the risk of childhood cancer: a census-based nationwide cohort study". Environ. Health Perspect. 123 (6): 622–28. doi:10.1289/ehp.1408548. PMC 4455589. PMID 25707026.
  10. ^ Pasqual; et al. (2020). "Neurodevelopmental effects of low dose ionizing radiation exposure: A systematic review of the epidemiological evidence". Environment International. 136: 105371. Bibcode:2020EnInt.13605371P. doi:10.1016/j.envint.2019.105371. hdl:10230/46812. PMID 32007921.
  11. ^ Almond; et al. (2007). "Chernobyl's subclinical legacy: Prenatal exposure to radioactive fallout and school outcomes in Sweden" (PDF). Columbia University.
  12. ^ Kitchin KT, Drane JW (May 2005). "A critique of the use of hormesis in risk assessment". Hum Exp Toxicol. 24 (5): 249–53. Bibcode:2005HETox..24..249K. doi:10.1191/0960327105ht520oa. PMID 16004188. S2CID 9105845.
  13. ^ Calabrese, Edward J (2004). "Hormesis: From marginalization to mainstream". Toxicology and Applied Pharmacology. 197 (2): 125–36. doi:10.1016/j.taap.2004.02.007. PMID 15163548.
  14. ^ Duport, P. (2003). "A database of cancer induction by low-dose radiation in mammals: Overview and initial observations". International Journal of Low Radiation. 1: 120–31. doi:10.1504/IJLR.2003.003488.
  15. ^ Aurengo (2005-03-30). "Dose-effect relationships and estimation of the carcinogenic effects of low doses of ionizing radiation". Académie des Sciences & Académie nationale de Médecine. CiteSeerX 10.1.1.126.1681. {{cite journal}}: Cite journal requires |journal= (help)
  16. ^ UNSCEAR 2000 Report Vol. II: Sources and Effects of Ionizing Radiation: Annex G: Biological effects at low radiation doses.
  17. ^ BEIR VII Phase 2 2006