The explosions and fires that wrecked the Chernobyl nuclear reactor 10 years ago last April brought on what is universally recognized as a catastrophe. Besides the immediate fatalities and human upheaval, which left hundreds of thousands disoriented, anxious about their own health, and bitterly concerned about their children, the accident inflicted incalculable material losses. In economic terms alone (though not in terms of casualties), Chernobyl was the greatest peacetime industrial disaster of all time. Its 10th anniversary was a fitting occasion for stocktaking—for determining what has been and has yet to be learned about the event, and for improving efforts to help the victims.
The one salvageable benefit is vital new information on how ionizing radiation affects human health. Already, to be sure, that relationship is better understood than the effects of most industrial pollutants, in both qualitative and quantitative terms. Further, unlike other contaminants, radiation doses are easy to reconstruct from the trails left by radioactive decay. But until now, the most important data on radiation health effects have come from the ongoing studies of survivors of the Hiroshima and Nagasaki atomic bombings. And inferences drawn from those intense exposures to radiation have not always meshed well with the results found when less radiation over a longer time is involved. Chernobyl is the first instance of huge populations being exposed to mostly low doses for many months and years.
As the 10th anniversary of the April 26, 1986, nuclear accident drew near, three major international conferences on its health effects were mounted. The culmination was a large gathering of experts in early April at the Austria Centre in Vienna, which IEEE Spectrum attended. It was sponsored by the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), and the European Commission (EC). Concurrently, the Nuclear Energy Agency, based in Paris, issued an appraisal of the accident’s radiological and health consequences. As for the two earlier conferences, one was sponsored by the WHO in Geneva, in November 1995, and the other was sponsored by the EC, Belarus, Russia, and the Ukraine in March 1996 in Minsk, Russia.
The scale of the reevaluations and the large overlap among the specialists taking part encouraged a fair degree of consensus about the accident's health effects so far. Still, first findings are tentative. One U.S. expert at the IAEA conference, radiologist F. A. Mettler, frowned on the Vienna meeting’s billing: “Summing Up the Consequences of the Accident.” Mettler, a member of the University of New Mexico's School of Medicine, Albuquerque, observed that full comprehension would take not 10 but 50 years.
Vastly complicating analysis is the crisis afflicting the former Soviets since the breakup of the USSR. In Russia, where national output is thought to have dropped by 50 percent and industrial production by nearly 75 percent, life expectancy for men has plummeted about seven years (to 58!) since 1986.
Often, too, those responsible for the welfare of victims are tempted to exaggerate, desperate as they are for funds. Belarus, the Ukraine, and Russia each have had at one time or another a ministry just for Chernobyl relief and monitoring. In Belarus, home to the worst-affected districts, 20-25 percent of the state budget goes to remedying Chernobyl's effects. Small wonder that Angela Merkel, Germany's environmental minister and the president and keynote speaker of the Vienna conference, agreed with Mettler that Chernobyl's consequences “cannot be summarized conclusively even today, 10 years after the accident.”
That said, three early results stand out:
- The incidence of thyroid cancer has risen far more than expected among infants and even children still in the womb who were in the most contaminated zones right after the accident.
- There is as yet no significant rise in leukemia among the inhabitants of those same zones or among the emergency workers and evacuees hit by the highest initial doses of radiation.
- Perhaps most widespread are psychosomatic illnesses--even in not-too-contaminated areas, there has been a large upswing in stress-related physical ailments, notably stomach and autoimmune disorders. In fact, morbidity and mortality due to such disorders may well in the end exceed sicknesses and deaths caused by radiation.
Scope of accident
The amount of radioactive materials released in the Chernobyl accident totaled about 10 exabecquerels (EBq, or 1018 Bq), which resulted in a global dose of about 600 000 person.sievert [see Defining Terms, above]. About six tons of the reactor fuel, or roughly 3.5 percent of the reactor's initial fuel mass, is thought to have been ejected: first, when fuel fragmented during the initial explosion(s), and a week to 10 days later, when temperatures climbed again, maybe as graphite continued to burn and the remaining core reconfigured itself and melted down more radically. While the releases contained numerous fission products [Table 1], the iodide and cesium components were the most deleterious. Releases of Cs137 are put at 85 petabecquerels (1015 Bq) and of I131, at 1760 PBq (2040 and 5060 percent respectively of initial inventory).
A comparison with the effects of atmospheric tests of nuclear weapons was made by B.G. Bennett, secretary of the United Nations Scientific Committee on the Effects of Atomic Radiation (Unscear), Vienna. At the summing-up, he said that the amount of Cs137 released at Chernobyl was about one-tenth the total from the weapons tests, but that the amount deposited in Central Europe in April through December 1986 was equivalent to the total deposited over all the years in which weapons testing took place. Thus, “the greatest global release of radionuclides from a man-made source was atmospheric testing of nuclear weapons. The greatest local impact of man-made releases was, however, the Chernobyl accident.”
Of the total dose of 600 000 person sievert from Chernobyl, about 40 percent fell on the former Soviet states, 50 percent on Europe, and the rest elsewhere in the Northern Hemisphere. At least a third of the dose was delivered to people by the first anniversary of the accident.
Persons nearest the blast
The health record is clearest for plant employees and emergency workers identified right after the accident as suffering from acute radiation sickness: 134, out of the 237 immediately hospitalized with clinical syndromes attributable to radiation. Out of the 134 acute cases, 28 died. In addition, two workers died at the site from injuries unrelated to radiation, and 14 more of the 237 have died in the 10 years since, not necessarily of causes related to radiation.
Most of the 28 who died early on were exposed to more than 6 gray, according to a report presented at Vienna and coauthored by one the world's leading experts on acute radiation sickness, Angelina K. Guskova of the Institute of Biophysics, Moscow. “In almost all of these cases, there was combined injury due to beta exposure resulting in skin radiation injury,” the report said. Other major damage was to bone marrow and to mucous membranes in the digestive and respiratory tracts.
Those diagnosed as acute cases tended to suffer impaired fertility for rather long after the accident. Besides being at greater risk of contracting cancer, they may be more prone to cataracts and cardiovascular and gastrointestinal problems many years hence. Nevertheless, “to date, a detailed and scientifically sound overall account of clinical signs and symptoms of the surviving patients in the population of 237 is lacking in general,” the Vienna report said. “Also, confounding factors have not always been dissociated from possible radiation effects.”
In terms of treatment, Chernobyl's unequivocal lesson is that bone marrow treatment did not work. It was done at the time by the physician Robert Peter Gale of the Medical Center of the University of California at Los Angeles (UCLA). But most of those given transplants, as directed by Gale in collaboration with Guskova, died. So, as Gerard Wagemaker drily noted in Vienna, the focus needs to be on therapies that “don't do more harm than good.” Wagemaker, a radiobiologist at Erasmus University, Rotterdam, the Netherlands, was principal author of the report on acute radiation sickness.