Charting Chernobyl's legacy

On the night of April 26, 1986, Reactor No. 4 at the Chernobyl nuclear power station in northern Ukraine exploded, blowing the thousand-ton cover off the building and unleashing vast amounts of radiation that were carried by the wind far beyond the disaster site.

Thirty people were killed immediately from the blast, which remains the worst accident of its kind in history. Yet experts fear that the worst health effects of the explosion have yet to come. The threat of radioactive contamination lingers in the region and the risk of cancer and other radiation-associated diseases for the estimated five million exposed to the radiation remains unknown.

More than 5,000 miles away, in his office in Fred Hutchinson's Public Health Sciences building, Dr. Scott Davis contemplates Chernobyl's tragic legacy on a daily basis. As the leader of a research team that has spent 14 years investigating the cancer risks posed by this massive public-health crisis, he's even walked within the 30-kilometer evacuation zone around the plant in which residents are still forbidden to live.

"When you go there and see it up close, it's very sobering," he said. "So much vegetation is gone. And it's going to be like that for years, certainly for our lifetime."

One aspect of the devastation Davis can address is to offer the world a more detailed understanding of some of the health risks posed by the Chernobyl incident. This may lead to strategies to minimize them. His international team of researchers is now putting the final touches on the most thorough risk analysis to date for thyroid cancer among those who were children at the time of the disaster. The study, to be published next year, is the only one conducted on this population group to estimate an individual's cancer risk based on his or her estimated dose of radiation.

For his contributions, Davis has become the first foreign epidemiologist elected to the Russian Academy of Medical Sciences, a group whose status in that country is on a par with the esteemed National Academy of Sciences in the United States. He will receive an honorary diploma in Moscow later this month during his 31st visit to the region.

But Davis isn't content to rest on these accomplishments. During the next phase of his research, Davis' team — which includes Dr. Ken Kopecky, and more recently, Drs. Robert Kimmel and Paul Neiman — will extend these cancer-risk studies to older Chernobyl survivors. The scientists also plan to investigate how the damage caused to DNA by radiation influences the risk of developing thyroid cancer. Collectively, all of these studies will bring a wealth of new information to researchers around the world who study radiation-associated cancers.

Providing some long-awaited answers to Chernobyl survivors has been a rewarding research endeavor. Yet, it hasn't been a straightforward one, Davis said. Some of the team's greatest achievements were simply establishing the working relationships and infrastructure necessary to get the studies off the ground.

"Within the first year of the accident, Ken and I were very interested in seeing if we could get involved and participate in long-term studies of health effects," said Davis, who is also chairman of the Epidemiology Department at the University of Washington. "But at the time of the accident, our government and that of the former Soviet Union were not friendly, so establishing connections through that route didn't work."

Davis and Kopecky, who is also a PHS investigator, had similarly poor luck obtaining support for their proposed cancer-risk studies through the private foundations established after the accident. Most of these organizations focused on providing medical aid and assistance to survivors.

"We were completely shut down; there was no interest in the project," Davis said. "So we just put the idea aside."

But in 1990, an opportunity surfaced when a Russian helicopter pilot involved in the initial efforts to contain the radiation developed leukemia and came to the center for a bone-marrow transplant. After his treatment, an informal exchange program began between Fred Hutchinson and the National Center for Hematology in Moscow. The relationship deepened when the director of the Moscow center approached Dr. Robert Day, who was then Fred Hutchinson's president and director, for assistance in developing a research and treatment institute for victims in Gomel, a town heavily contaminated from Chernobyl, situated in what was then Belorussia. Day solicited help from Davis and Kopecky, who made their first trip to Moscow in fall of that year.

"From that began a pretty concerted effort to establish what was needed to do epidemiological research," Davis said.

He and Kopecky were well suited for the job. Both had spent time conducting similar research at the Radiation Effects Research Foundation in Hiroshima, where Davis was a research associate from 1983 to 1985.

Davis and Kopecky were soon well on their way to a productive relationship with Soviet scientists. Then, in December of 1991, the Soviet Union collapsed.

"The area around Gomel became a separate country called Belarus," Davis said. "We were back to square one in terms of negotiations."

But thanks to efforts of Day and the late Adm. Elmo Zumwalt, a former Chief of Naval Operations for the U.S. Navy and Fred Hutchinson trustee, relationships were re-established with the newly formed countries. A research consortium consisting of three international teams was created in 1992 to study long-term health effects of the radiation released at Chernobyl. Through this arrangement, center scientists would partner with research counterparts in Russia. A second team was formed between scientists at Baylor College of Medicine in Houston and scientists in Ukraine, and researchers from Yale University/Bridgeport Hospital and Belarus comprised the third. The project was financed with grants from the Navy. Partnerships between Ukrainian and Belarussian scientists later were developed with investigators from Roswell Park Cancer Institute in Buffalo, N.Y.

"Our initial work in Russia was simply to conduct small pilot studies to establish in concrete terms whether we could carry out all phases of an epidemiological study," Davis said. "We had to figure out whether we'd be able to identify cancer cases, verify diagnoses, establish estimates of radiation dose for individual study participants, collect biological specimens and manage data. There was no history of doing this kind of research in Russia or the other two countries. We had to set it all up from scratch."

The center team

Several members of Davis' Radiation/Environmental Exposures research team have been integral to the project's success.

Laurie Shields and Theresa Taggart have served as project coordinators during different phases of the study, overseeing the data collection, preparation and implementation of study protocols and materials, and taking care of the multiple grants and contracts that have financed the work. Lynn Onstad has led much of the data analysis for the group's studies on thyroid cancer and leukemia risk assessment. Teri Kopp has been the group's liaison to the U.S. Civilian Research and Development Foundation, which has handled the complex payroll and money transfers required to conduct the overseas research.

Once the team established the capability to do the research, the group began studies of thyroid cancer, a disease linked to radiation exposure. The researchers focused their efforts on the Bryansk Oblast of Russia, an area that is located roughly 110 kilometers from Chernobyl. They identified thyroid cancer cases among those who had been children at the time of the explosion, and set about collecting information that would allow them to estimate each individual's radiation dose.

"This was based on where people were at the time of the accident, what they ate and drank, and whether they received prophylactic measures to reduce their radiation exposure," Davis said. "From this information, we used computer models to reconstruct their radiation dose."

Key findings

Compared to other studies of cancer risk in radiation-contaminated areas, a wealth of information was available to the researchers concerning residents' initial exposure. "That's because soon after the blast it was recognized that it was important to see what people received, so mobile units were sent out to perform thyroid and whole-body radiation counts, and lots of measurements of radiation levels in the environment were taken," Davis said.

Results from this study, as well as a related study on childhood leukemia in residents of the three consortium countries, will be published later this year. One of the key findings to emerge from the childhood thyroid study is evidence of a significant increase in risk associated with increasing radiation dose to the thyroid.

Another study published last year by Davis, Kopecky and colleagues in Russia revealed that children in the area with iodine deficiency — a common problem in the region — were more likely to develop thyroid cancer than those who had normal levels of iodine. The risk was particularly increased among those also exposed to Chernobyl radiation. The findings suggest that elimination of this deficiency through dietary supplementation could help reduce cancer risk.

Despite the lack of resources available to initiate these studies, Davis said that scientists and citizens of the three countries were eager for the research from the start. "Our collaborators in Russia have been terrific colleagues," he said. "We now have very close ties with our partner institutions."

He also credited the strong support of the senior administration at Fred Hutchinson for helping him and Kopecky establish stable working relationships with their overseas colleagues.

"One thing that set us apart from other research groups in earlier years was the ability to pay our colleagues there in U.S. dollars and do so reliably and consistently," he said. "The incredible support and flexibility of the center, especially early on, really made this happen. That can't be overstated."