LNT meaning

LNT (linear no-threshold) is the risk model used in legal practice to estimate the likelihood of harm (principally cancer) from ionising radiation at any dose. It assumes a straight-line relationship between dose and risk with no safe threshold and that risk per unit dose is constant, regardless of dose rate, though some guidance applies a dose and dose‑rate effectiveness factor (DDREF). LNT is not defined in statute, but is the prevailing scientific hypothesis adopted by international bodies (including ICRP and UNSCEAR) and reflected in UK and Irish regulation and guidance. In the UK this includes the Ionising Radiations Regulations 2017 (and the Northern Ireland equivalent), environmental permitting regimes, and health protection guidance from UKHSA and HSE. In Ireland it is reflected in the transposition of the EU Basic Safety Standards and guidance from the Environmental Protection Agency. LNT underpins duties of justification and optimisation (ALARA/ALARP), the setting of dose limits, and radiation risk assessments across environmental permitting, medical exposures and occupational health. In litigation, it informs expert evidence on causation and quantum for low‑dose and cumulative exposure claims. While subject to ongoing academic debate, regulators and courts across England & Wales, Scotland, Northern Ireland and Ireland generally apply LNT unless authoritative guidance...