Radiobiology > Stochastic Effects > No-Threshold Models of Risk

No-Threshold Models of Risk

The excess risk for solid tumor formation in survivors of Nagasaki and Hiroshima bombings follows a dose response curve best described by a linear or linear-quadratic function. There is no statistically significant advantage to using the more complex linear-quadratic expression for estimating solid tumor risk. For leukemia data, however, a linear quadratic model is most appropriate.

Only the linear and linear-quadratic functions are currently recognized by major risk assessment and management agencies. The figure below summarizes all potential functions offered to explain low dose exposures and cancer risk.

Alternative relationships for cancer risk vs. radiation dose as extrapolate to low-dose exposures, given a known risk at a high dose: supra-linearity (A), linear (B), linear-quadratic (C) and hormesis, which implies a biologically beneficial effect at low dose (D).

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