In fact, radiation is a far less potent carcinogen than other toxic substances. Studies of more than 80,000 survivors of the Hiroshima and Nagasaki blasts have found that about 9,000 people subsequently died of some form of cancer. But only about 500 of those cases could be attributed to the radiation exposure the people experienced.
The average amount of radiation that victims in Hiroshima and Nagasaki were exposed to would increase the risk of dying from lung cancer by about 40 percent, Boice said. Smoking a pack of cigarettes a day increases the risk of dying of lung cancer by about 400 percent.
“Radiation is a universal carcinogen, but it’s a very weak carcinogen compared to other carcinogens,” Boice said. “Even when you are exposed, it’s very unlikely you will get an adverse effect. But fear of radiation is very strong.”
From Wikipedia I see that the range of estimated deaths resulting from Chernobyl is wide, but the most credible numbers appear quite low:
The Chernobyl Forum is a regular meeting of IAEA, other United Nations organizations (FAO, UN-OCHA, UNDP, UNEP, UNSCEAR, WHO, and the World Bank), and the governments of Belarus, Russia, and Ukraine that issues regular scientific assessments of the evidence for health effects of the Chernobyl accident. The Chernobyl Forum concluded that twenty-eight emergency workers died from acute radiation syndrome including beta burns and 15 patients died from thyroid cancer, and it roughly estimated that cancer deaths caused by Chernobyl may reach a total of about 4,000 among the 600,000 people having received the greatest exposures. It also concluded that a greater risk than the long-term effects of radiation exposure is the risk to mental health of exaggerated fears about the effects of radiation:The designation of the affected population as “victims” rather than “survivors” has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption ofmushrooms, berries and game from areas still designated as highly contaminated, overuse of alcohol and tobacco, and unprotectedpromiscuoussexual activity.
Fred Mettler commented that 20 years later:The population remains largely unsure of what the effects of radiation actually are and retain a sense of foreboding. A number of adolescents and young adults who have been exposed to modest or small amounts of radiation feel that they are somehow fatally flawed and there is no downside to using illicit drugs or having unprotected sex. To reverse such attitudes and behaviors will likely take years although some youth groups have begun programs that have promise.