Introduction
	For more than thousands of years humans have tried to judge, evaluate and avoid hazardous environmental situations and the development of nuclear technologies have made it possible for man to cause catastrophic and long-lasting damage. The complex nuclear technology with its harmful and rare effects is unfamiliar for most people and trial-and-error learning is thus difficult since few people have experienced this environmental hazard. Most individuals obtain their information through news media, that thoroughly document mishaps, accidents, and catastrophes around the world. Much of the public fear of radiation is caused by the association of radiation with nuclear explosions and nuclear war and the potential late effects of 131I thus continue to cause anxiety in the general public and medical community. Other radionuclides are used for diagnosis of thyroid disorders but 131I is still used in most institutes, particularly for the treatment of hyperthyroidism and thyroid cancer. Fears of carcinogenic and genetic effects limits the use of radioiodines in children and adolescents although some clinicians advocate the use of 131I in children due to the effectiveness and low cost. The present paper reviews the current epidemiological knowledge on radiation-associated cancer, focusing on exposure to radioiodines, and describes the latest findings from the Swedish iodine cohorts. A short section on some of the latest findings from the Chernobyl area is also added.