Chernobyl’s 1986 reactor explosion remains the worst commercial nuclear disaster. Operators disabled safety systems and removed control rods for a night‑time test, causing coolant to overheat, steam to flash‑boil, and fuel to shatter. Graphite ignited, exposing 600 workers; 134 received doses between 800 and 16,000 mSv, and 28 died within three months. Long‑term monitoring found slight leukemia rise among responders but no increase in solid tumors.

Radioactive ash settled on Ukrainian pastures, contaminating dairy cows and entering milk. Children who drank the milk absorbed iodine in their thyroids, leading to about 6,000 diagnosed thyroid cancers and fifteen deaths so far. Authorities note that iodine’s eight‑day half‑life made the harm avoidable; Britain’s 1957 Windscale response discarded milk for 44 days, preventing similar outcomes. Evacuations added stress that may have outweighed radiation risk.

From 1982‑84 Taiwan unknowingly built over 180 structures with steel laced with cobalt-60, exposing roughly 10,000 residents to an average 400 mSv dose—seven times typical background. Epidemiology showed no radiation sickness and cancer rates lower than national averages, a result some attribute to hormesis. Critics argue age bias and statistical limits, warning against using such data to relax global radiation‑protection standards.