The Chernobyl accident is the only commercial nuclear power reactor accident in the world (including the recent accident in Japan, to be discussed next) where people actually died from radiation. Two people died immediately in the accident from the explosion and a third was reported to have died from a heart attack. Firefighters and Chernobyl power plant employees were the group most at risk. A total of 237 first-responders were hospitalized and 134 of them were diagnosed with acute radiation syndrome (see Chapter 7) after receiving doses ranging from 0.8 Gy up to 17 Gy (15). Five firefighters died the first night, and an additional 23 died within a month from acute radiation syndrome (19). Bone marrow trans­plants were done on 13 of these people, but they all died from the hematopoietic syndrome. Recall that about half of the people will die from a single dose of 4 Gy. By 2004 an additional 19 people in the most-exposed group died, though not from bone marrow failure (13, 15). In total, 28 people died from acute radiation effects, 2 from blast effects, one from a heart attack, and 19 from uncertain causes.

Many studies have been done since the Chernobyl accident on the long-term health consequences to the people who were exposed. Because there was so little public health information available for the exposed population prior to 1986, it is difficult to make accurate assessments. The International Atomic Energy Agency (IAEA) established the Chernobyl Forum in 2003 to study the environ­mental and health consequences of the accident, and the most definitive report of the accident was published in 2006. The Chernobyl Forum included experts from seven United Nations organizations, including the IAEA, the World Health Organization (WHO), and the United Nations Scientific Committee on the Atomic Effects of Radiation (UNSCEAR). It also included representatives from the governments of Belarus, Ukraine, and the Russian Federation (20). The full report on health effects was published by the WHO in 2006 (21). They project that eventually 4,000 people may die from cancer related to the Chernobyl acci­dent. A report was done by the anti-nuclear organization Greenpeace claiming that there were up to 200,000 deaths from Chernobyl by 2004, but this study lacks credibility. It is strongly at variance with the bulk of scientific published reports on Chernobyl. Virtually all of the authors were from Ukraine and were possibly somewhat biased in evaluating the consequences of the accident (22). Another report—TORCH (The Other Report on Chernobyl)—was commissioned by the Greens/European Free Alliance (EFA) party in Europe to respond to the conclu­sions of the Chernobyl Forum (23). They estimate that 30,000 to 60,000 cancer deaths will result from Chernobyl, far higher than the Chernobyl Forum report. Who is right?

There were four different groups of people who were exposed to significant doses of radiation from Chernobyl. The highest exposed group consisted of the “liquidators,” the emergency and recovery operations people who were involved in containing and cleaning up the accident. This included 240,000 workers exposed to high radiation levels, and eventually up to 600,000 liquidators were registered, though most of the latter were exposed to much lower doses. The average effec­tive dose to these individuals was estimated at 100 mSv. The second population consisted of 116,000 people who were evacuated in 1986 from the highly con­taminated 30-kilometer exclusion zone (Figure 10.1). These people had average doses of 33 mSv. Another 220,000 people were evacuated from a larger area (the strict-control zone) during 1986-2005 with cumulative doses of over 50 mSv over

those years. Finally, about 5 million people lived in the larger zones that received fallout from the accident and got doses of 10-20 mSv during 1986-2005 (20). Doses to anyone else in Europe were negligibly small.

As a frame of reference, recall that the annual background radiation dose in Colorado is about 4.5 mSv per year, so over 20 years, Colorado residents get cumulative doses of about 90 mSv. The background dose in Kiev is 12 micro — Roentgen3 per hour, which works out to be just under 1 mSv per year, far lower than the natural background in Colorado (24). So the people in the larger zone who got some contamination received an additional 1 or 2 mSv per year in addi­tion to natural background of 1 mSv/yr. This total dose is about half of what I get every year from natural background. It is about the same as the 3.2 mSv aver­age background radiation for all US citizens and half of the total average of 6.2 mSv for US citizens when medical doses are taken into account. The very high estimates of excess cancer deaths from the Greenpeace and TORCH reports are simply not realistic.

Since 131I is the biologically significant isotope released in the highest amounts, you would expect that children who drank contaminated milk would get high doses to the thyroid; indeed, that is what happened. About 5,000 cases of thyroid cancer have been identified in children and adolescents.

There are some interesting factors related to the thyroid cancer cases. First, the incidence of thyroid cancer could have been minimized if iodine pills had been rapidly given out to the population, though workers and their families in Pripyat were given iodine pills within the first 30 hours. Second, there was a general iodine deficiency in this region, with an abnormally high prevalence of goiters in the population (25). This would lead to a vigorous uptake of radioactive iodine. Third, the incidence of thyroid cancer happened more rapidly than was expected based on the Japanese bomb survivors. Fourth, children are much more sensitive to getting thyroid cancer than adults (and usually drink more milk). And finally, thyroid cancer is rarely fatal, with a survival rate of over 95% in the United States. Out of the nearly 5,000 cases of thyroid cancer, only 15 people died from the can­cer up to 2002 (26, 27). It is clear that more cases will arise in the future because solid cancers can develop over a lifetime. Interestingly, the standard treatment for thyroid cancer is surgery followed by high doses of 131I to kill thyroid cancer cells (28). Patients must then take thyroid hormone pills for the rest of their lives.

How about other cancers? Leukemia is the first cancer that was found in the Japanese bomb survivors because it has such a short latency period and the risk is over by about 15 years after exposure. However, there is no solid evidence that leukemia incidence has increased in the exposed population (21, 29). Out of the 600,000 liquidators exposed to an average dose of 100 mSv, the Chernobyl Forum projected that there might be an eventual 4,000 people dying of cancer from the radiation. This is compared to about 100,000 people in that population who will die from cancer due to normal conditions (20). Even though 26 years have passed since the Chernobyl accident, there will continue to be studies of the population, similar to the ongoing studies of the Japanese bomb survivors, and the number of excess cancers will become more defined. It is extremely unlikely that it will far exceed the 4,000 person estimate, however. As I discussed in Chapter 7, the risk of fatal cancer for a population that does not include children is 4% per Sv, when given at a low dose and low dose rate, as is the case for Chernobyl populations. So for 600,000 adults people exposed to an average dose of 100 mSv (0.1 Sv), the expected lifetime number of fatalities is 2,400 people. Estimates of tens to hun­dreds of thousands are simply not scientifically credible.

The largest public health problem resulting from Chernobyl has been the impact on mental health. People were moved out of their homes into communities where they did not feel comfortable or welcome. People had strongly negative attitudes about health and well-being and felt they had little control over their lives. They were convinced that they were doomed to a shorter life expectancy, and this fatal­ism led to a loss of initiative in getting jobs and taking care of their personal lives. Life expectancy in general has declined in the Russian Federation, quite apart from Chernobyl, and the average life expectancy in 2003 was just 59 years for men. There is also a sense of victimization by and dependency on the govern­ment. All of these factors have combined to create a huge public health problem as a legacy of Chernobyl (20, 30). Many of these problems might have been allevi­ated by government transparency, immediate action after the accident, and estab­lishing a legacy of trust that honest, accurate information was being disseminated.

These are issues that are applicable after any accident. Honesty and transparency by the government involved (and accurate reporting by the media) are essential in minimizing stress and psychological factors that were also the biggest problems after TMI and after the Japanese accident to be discussed later.