The document provides an overview of the Linear No-Threshold (LNT) model of radiation risk and an alternative model called radiation hormesis. The LNT model suggests that any amount of radiation causes DNA damage and mutations leading to increased cancer risk, but it is inconsistent with evidence. The radiation hormesis model posits that low doses of radiation activate the body's defenses like antioxidants and DNA repair enzymes, reducing overall DNA damage and cancer risk compared to no exposure. It is supported by evidence that radiation stimulates natural killer cells that eliminate cancer cells.

1. Brief Primer on the LNT Model and Radiation Hormesis
Version 1.0
Aug 8, 2018
LNT Model (simplistic, easy to understand and so popular, but is wrong, i.e. not consistent with evidence):
1. Low-dose radiation causes some DNA damage and mutations.
2. Increased mutations mean increased cancers.
Radiation Hormesis (realistic, requires more thinking to understand, and is correct, i.e. consistent with evidence)
1. Low-dose radiation causes some DNA damage.
2. Even in the absence of the low-dose radiation, DNA damage does occur due to natural causes. This damage is
much more than the damage due to low-dose radiation.
3. Our body responds to the additional DNA damage due to low-dose radiation by increasing defenses such as
antioxidants and DNA repair enzymes. These elevated defenses last for some time.
4. The elevated defenses not only repair the damage caused by low-dose radiation but also repair and prevent
some of the damage that would have occurred due to natural causes in the subsequent period.
5. The net result is that there would be reduced DNA damage and mutations following the exposure to low-dose
radiation, in comparison to having no radiation exposure.
6. The primary cause of cancer is not cancerous mutations. (Almost all of us have cancerous mutations within us
but only a small percentage of us have cancer.)
7. The primary cause of cancer is the suppression of the immune system. (There is plenty of data showing that
when the immune system is suppressed, cancer risk increases, and when the immune system is boosted, cancer
risk decreases.)
8. Low-dose radiation causes some DNA damage. The damaged cells up-regulate RAE-1 and other ligands of the
NKG2D receptor activating natural killer cells. (This is the mechanistic reason for the radiation hormesis).
9. Natural killer cells eliminate cancer cells, and so there would be less cancers following exposure to low-dose
radiation.
Radiation Hormesis (simpler explanation – omitting the discussion of DNA damage and mutations):
1. Low-dose radiation increases activation of natural killer cells.
2. Natural killer cells eliminate cancer cells, and so there would be less cancers following exposure to low-dose
radiation.
Mohan Doss, PhD, MCCPM,
Diagnostic Imaging, Fox Chase Cancer Center, Philadelphia, PA,
E-mail: mohan.doss@fccc.edu