LNT

LNT, short for Linear No-Threshold, is a model used in radiobiology and radiation protection to describe how the risk of health effects from ionizing radiation scales with dose. The model states that the probability of stochastic effects, such as cancer or genetic mutations, increases linearly with dose without a threshold. In other words, any amount of exposure carries some risk, and total risk accumulates with the amount of radiation received.

LNT is widely used in risk assessment and regulatory frameworks. It provides a conservative approach by extrapolating observed effects at high doses down to low-dose exposures and applying safety and uncertainty factors. International and national bodies, including the ICRP and BEIR committees, have relied on the LNT assumption to set occupational limits, public safety standards, and guidelines for medical imaging and environmental protection.

Advantages of the LNT model include its simplicity, consistency across different exposure scenarios, and a precautionary bias that helps protect public health in the face of uncertainty about low-dose effects. It avoids assuming a safe exposure level, which is useful when data at very low doses are ambiguous.

Critics argue that the evidence at low doses is not definitive and that some responses may be nonlinear or even exhibit thresholds or hormesis (beneficial effects at small doses). They contend that LNT may overestimate risk in certain contexts or oversimplify complex biological processes. Despite controversy, LNT remains the prevailing default in radiation protection policy due to its conservative risk management rationale.