Radiation exposure has significant health consequences. In cases of sudden high doses of ionizing radiation exposure (such as being in close vicinity to a nuclear meltdown as occurred most recently in Japan), a condition called acute radiation sickness can result, manifesting as constellation of symptoms which occur as a result of a loss of rapidly dividing cells, such as hair cells, cells of the inner lining of the gastrointestinal tract, and blood cells. Often this condition is fatal.
Low levels of radiation that remain at the site of nuclear accidents for some time after, such as Chernobyl, may also cause delayed adverse health effects to exposed populations. However, due to the prolonged period of time that must elapse before health consequences may reveal themselves, it is generally cumbersome to effectively determine the extent to which long-term residual exposure contributes to disease.
In a recent publication in the journal of Environmental Health Perspectives, Zablotska et al investigated the risk of developing leukemias (a group of blood cancers thought to be linked to radiation exposure) among Chornobyl cleanup workers. In their results, they indicate that "altogether, 16% of leukemia cases (15% of non-CLL, 18% of CLL) were attributed to radiation exposure." Furthermore, the authors conclude that "Exposure to low doses and low dose-rates of radiation from post-Chornobyl cleanup work was associated with a significant increase in risk of leukemia, which was statistically consistent with estimates for the Japanese atomic bomb survivors."
Overall these findings support that long-term low-dose exposure to radiation has at least some adverse health effects. Though some may believe that this is just logical, arguments have been made that low-dose radiation exposure does not have any adverse health effects. Indeed, some are proponents of the contrary, believing that low-dose exposure of ionizing radiation can have beneficial effects instead (theory of Radiation Hormesis).