Ramsar, Iran: Holds the record for the highest level of natural background radiation. Hot springs bring radium to the surface, which local rocks and soils absorb. Residents receive yearly radiation doses up to 131 millisieverts from external exposure alone in extreme cases, far above normal global limits. Despite exposure rates over 100 times the global average, extensive biological and health studies indicate no increased rates of cancer, birth defects, or reduced lifespan among residents compared to normal-background populations. In fact, preliminary data suggest residents may develop higher radio-resistance and DNA repair capabilities....