One year after the Chernobyl nuclear accident killed 31 people, hospitalized 500 more and exposed at least 135,000 to the long-term risk of cancer, the medical lessons to be learned from the catastrophe are still evolving. But in some ways the disaster has already contributed advances in medical care--and to a worldwide awareness of the need to be prepared for Chernobyl-like events.
On the eve of the first anniversary of the April 26, 1986, accident, scientists say that much of the most important medical information to be gained from Chernobyl will surface as an international team of researchers tracks the long-term health effects of the radiation that spewed out after an explosion and fire at the Ukrainian nuclear power plant.
But already, say the Soviet and American doctors who struggled to save the lives of acutely burned and irradiated victims, they have learned much that may be useful if such an emergency were to occur today.
These findings range from the possibility that people can survive higher doses of radiation than previously believed, provided they receive proper supportive care, to knowledge that is useful in the treatment of leukemia patients.
The accident also gave researchers a wider perspective on the acute health effects of radiation. Previously, scientists had relied mainly on knowledge derived from the 1945 atomic bombings of Hiroshima and Nagasaki, Japan. But major differences between the effects of the blasts in Japan and the Chernobyl reactor accident have given scientists a broader understanding of the complex effects of radiation and fire.
Another spinoff has been the establishment in the United States of a national network of bone marrow donors who will be available to provide marrow for leukemia and aplastic anemia patients--for whom a bone marrow transplant can be lifesaving--and presumably also for victims of any reactor accident.
And, through collaboration with the Soviets, the Armand Hammer Center for Advanced Studies in Nuclear Energy and Health has established a research program in which a group of international scientists will follow 135,000 Soviet evacuees from the Chernobyl area at least over the next generation to learn the extent to which the accident will result in an increase in the number of cases of cancer, mental retardation and genetic defects.
The effects of radiation sometimes take as long as 20 years to surface as cancer, for example. Studying the incidence of these delayed radiation effects is expected to add importantly to the information already gained from long-term studies of the survivors of the Hiroshima and Nagasaki A-bomb blasts, which probably caused different patterns of radiation exposure from those that emanated from Chernobyl.
Team of Experts
In Japan, humans were exposed to an instantaneous explosion of radiation whose immediate effects were mainly to the skin and other external organs, according to experts. At Chernobyl, the acute radiation effects were more complicated, they said, because the radiation was emitted more slowly over a period of days from a plume that rose above the reactor and, drifting with the wind, affected humans who inhaled and ingested radioactive gases and particles.
As part of the new awareness of the need to be prepared, the Hammer Center also is slated to form a special team of nuclear disaster experts ready to rush anywhere in the world to give governments advice on how to respond to such emergencies.
Because the accident was nuclear in nature and because it occurred within the closed society of the Soviet Union, special obstacles have been placed in the way of experts seeking access to the data that they need for a better understanding of the accident's medical consequences.
So far, except for a meeting of the International Atomic Energy Agency in Vienna last August at which the Soviets released some important information, U.S. agencies say they have had scant contact with the Soviet scientists who have been involved in studying the accident's health effects.
"We do not know whether we ever will get the kind of data that we don't now have," said Robert Wood, director of physical and technological research for the U.S. Department of Energy. Examples of the missing data needed to arrive at a better evaluation, he said, include detailed estimates of the radiation exposure to internal organs of persons who inhaled or ingested radioactive particles.
Although the Soviets appear to be avoiding a government-to-government relationship, preferring to channel information to the West through the IAEA in Vienna, they have been willing to meet with Dr. Robert P. Gale, the UCLA physician who headed the only team of foreign doctors allowed to help in treating Chernobyl victims. It was through Gale, who is president of the Hammer Center, that U.S. government agencies gained much of the medical information now available.
The kinds of medical problems that confronted the Soviet and American doctors were complex because victims often had an array of different types of injuries. For example, about 200 of the 500 persons injured seriously enough to be hospitalized--many were firemen--suffered from both the effects of radiation and thermal burns caused by the fire that engulfed the reactor.
Supportive Care Cited
In addition, some workers had breathed or swallowed radioactive particles that damaged internal organs and added considerably to the medical care problems.
While bone marrow transplants received the major share of public attention at the time, the reason more workers did not die, Gale said in an interview this week, is because of the kind of supportive care that they received while in the hospital. Some of the procedures had rarely, if ever, been tried before, he said.
One such technique tried by the Soviets, which Gale said had not been used before for this purpose, consisted of removing plasma from burn patients and screening out toxic substances that were byproducts of burns so that their adverse effects on the brain and other organs were reduced. The "clean" plasma was then reintroduced to the patient.
The Soviets also attempted to control bleeding, which is one consequence of radiation exposure, by removing large numbers of a patient's platelets, blood cells that cause blood to clot, and preserving them outside of the body until the patient began to bleed. The platelets were then transfused.
Platelets, unlike certain other blood cells, are not as apt to have been destroyed by the radiation if removed soon after being exposed, according to Gale.
Gale said that while the plasma and platelet techniques may have promise, they require more testing before use in this country.
The Soviet doctors also used a treatment that only recently has been licensed in the United States for the treatment of AIDS and other ailments that impair the immune system. It consists of the intravenous injection of gamma globulin to increase patients' ability to fight infection.
Other lifesaving measures included the use of newly developed antibiotics that were flown to Moscow from the United States and anti-viral drugs that successfully controlled herpes infections that had been stimulated by radiation.
But perhaps the most significant finding to date involves the 13 irradiated workers on whom the Soviet and American doctors performed bone marrow transplants. Gale said two of the 13 remain alive, but the U.S. Nuclear Regulatory Commission reported in February that there is now only one survivor. None of the additional six patients in whom the Soviets transplanted fetal livers, another source of bone marrow, survived longer than one week.
Gale, who helped the Soviet doctors perform marrow transplants, agrees that judging how much radiation the workers had been exposed to was difficult. Yet such judgments were crucial in choosing candidates for the marrow transplants.
A controversy has surfaced among scientists over whether physicians consistently overestimated radiation exposures in those patients who also suffered burns. The doctors may have been attributing to radiation some symptoms that actually stemmed from the burns, experts on one side of the debate maintain.
If this indeed did happen, they say, it could mean that some of those who received bone marrow transplants may have undergone the surgery unnecessarily and been subjected to a transplant-reaction condition called graft-versus-host disease. In that situation, cells in the bone marrow literally turn against the patient and cause death.
According to Dr. Clarence C. Lushbaugh, a U.S. researcher at the Radiation Emergency Assistance Center in Oak Ridge, Tenn., the report released by the Soviets last August suggests that burns contributed to the deaths of at least 23 of the 29 radiation fatalities that have been attributed to the accident. The deaths of two workers killed in the initial explosion brought the total death count to 31.
Because the Chernobyl workers had not been wearing devices that measure radiation dosage, Lushbaugh said, the doctors who treated them had no accurate way to determine the dose they had received.
Addressing an American Medical Assn. conference on Chernobyl last fall, Lushbaugh said the Soviet physicians who treated the Chernobyl patients should release more detailed case reports so that the relative roles of fire and radiation can be determined. He said there is a growing amount of medical information suggesting that thermal burns of insufficient extent to cause death alone may cause death in combination with non-lethal amounts of radiation.
In an interview, Lushbaugh said the evidence that combined injury from radiation and burns can distort estimates of radiation dosage is the single most important medical finding to come from the Chernobyl experience.
As one of the physicians who helped perform some of those transplants, Gale vigorously denied that the effect of burns on the injured persons had influenced the Soviet doctors' estimates of radiation dosage.
"I saw the Soviet data last week while attending a meeting in England, and I am very impressed that they are accurate," he said.
According to Gale, the dosage had been calculated by determining the number of certain types of immune-system cells in the patients' blood and the number of damaged chromosomes. Gale said that neither of these measures is influenced by burns.
He said the Soviet doctors "have promised to publish their data in English," possibly next month.
Gale said that the Chernobyl experience has shown that the kind of "sophisticated" support care used in Moscow makes it possible today to hold off doing transplants on patients who previously would have received one.
"Before Chernobyl, the common wisdom was to do a transplant on persons who had received above 5 or 6 Grays (500 to 600 rads), and there was no upper ceiling," Gale said. "We think the lower level now is 8 or 9 Grays, and with very sophisticated care we think we can go to 14 or 15 Grays."
(Grays have replaced rads as a unit of radiation exposure. One Gray equals 100 rads. Five or six Grays is believed to be a lethal dose. A typical chest X-ray gives a radiation dose less than 20 thousandths of a rad.)
Bone marrow transplants will continue to be performed on other kinds of patients with leukemia or aplastic anemia, according to Gale and other experts who say the Chernobyl accident may increase use of the technique for those illnesses in this country.
In fact, stimulated by the problem that the Soviet doctors encountered locating suitable marrow donors, the Red Cross and other organizations, using U.S. Navy funding, are forming a national network of about 70,000 Americans who can serve as voluntary donors for patients in need of marrow.