When reactor No. 4 at the Chernobyl station in the Ukraine blew apart at 1:24 a.m. on April 26, 1986, the explosion and the 10 days of burning that followed propelled radioactive particles and gases into the air. They dispersed over an area of the Soviet Union that is now the republics of the Ukraine, Belorussia and Russia.

Most of the larger radioactive fallout particles settled into the 30-kilometer "exclusion zone," where the massive radiation doses immediately killed two nuclear plant workers and exfoliated a nearby forest. About 200 firemen, rescue workers and employees experienced severe radiation sickness. Within four to six weeks, 32 died from burns and effects of the radiation, which destroyed their nervous, gastrointestinal and immune systems.

A few days after the explosion, about 40,000 "liquidators" were dispatched to the scene to clean up.

Over the next several years, the Soviet Union conscripted between 300,000 and 600,000 young men - soldiers and civilians, most of them 20 to 35 years of age - to continue the work.

"They did not have protective gear, and during the early months very few wore dosimeters to measure the amount of radiation they absorbed," says hematologist Stuart Finch. "Some of their work consisted of climbing up into the top of the reactor and throwing radioactive graphite into its smoldering and highly radioactive core." One of the world's foremost experts on the effects of radiation exposure on blood and bone marrow, Finch is professor emeritus at UMDNJ-Robert Wood Johnson Medical School at Camden.

During the next 18 months, many Ukrainian liquidators will undergo medical evaluations and biodosimetry tests to calculate the radiation dose each received. About 90,000 are expected to be entered into a registry and followed for 20 years or more for evidence of late radiation effects.

"Preliminary research conducted several years ago by the Ukrainian government concluded there was no significant rise in the number of cases of leukemia," notes Finch.

"We will be confirming these results and studying the risks of other blood-related cancers and disorders such as lymphomas and aplastic anemia. The latency period can be 10 years or more. Solid tumors may take even longer to develop."

So how did a 1944 graduate of the University of Rochester School of Medicine and Dentistry, whose goal was to be a general practitioner in his hometown of Broadalbin, New York (population about 1,500), end up in this field?

"Fate dictated something vastly different for me," he says.

A two-year stint with the U.S. Army Medical Corps and a visit to the city of Kure, Japan, several miles from Hiroshima, was the springboard for his career.

A medical school classmate was beginning a study of the effects of radiation exposure on those in Hiroshima and Nagasaki during the atomic bombings.

"I became intrigued with the research," Finch recalls. He returned to the U.S. in 1948 and completed a residency in medicine and a fellowship in hematology at hospitals affiliated with Harvard and Boston universities. He taught at Boston University Medical School for one year, and in 1953 joined the faculty of the Yale University School of Medicine.

In 1958, Yale became the administrator of the National Academy of Sciences' medical programs in Hiroshima and Nagasaki. Finch, who then headed the school's hematology/oncology division, was appointed the Atomic Bomb Casualty Commission's chief of medicine. He, his wife, Patricia, and their two sons and two daughters, ages 1 1/2 to 12, left for Japan in 1960 and lived there for the next two years. The Finches quickly assimilated, learning to speak Japanese and attending plays, concerts and pottery-making demonstrations.

The children went to Japanese schools, and Patricia taught her women friends how to speak English and do American crafts. "The Japanese sought out relationships with Americans and were hungry to learn about our culture, sports and music," recalls Stuart.

"After returning to Japan in 1975 and resigning from Yale in 1977, I planned to remain in Japan permanently," he recalls. "I was immersed in the research, and my wife and I enjoyed living there."

But an encounter with former Yale colleague Frank Gray - then chair of medicine at Thomas Jefferson Medical College in Philadelphia - steered him in a new direction. Gray told Finch that his institution had just ended a clinical affiliation with Cooper Medical Center in Camden, and that Cooper's new partner, Rutgers Medical School, was looking for a new chair of medicine.

Finch was offered the position and held it until 1986, when he took a two-year leave to again be chief of research and a permanent director of the Japan project. Upon his return, he was named Cooper Hospital/University Medical Center's vice president for research development. He continued in that position, as well as being professor of medicine at the renamed UMDNJ-Robert Wood Johnson Medical School at Camden, until retirement last year.

Results from the Japan project have been derived from life-span studies and other observations that have been ongoing for five decades. They include comparisons between exposed survivors of the Hiroshima and Nagasaki bombings and people who were in the cities, but beyond the point of radiation exposure.

Research from Japan has confirmed that intense radiation exposure is responsible for chromosome damage in lymphocytes and may lead to the development of cancerous cells in the blood or solid tumors. Finch's studies concluded that cases of leukemia - which have a minimum latency period of two to three years - peaked in 1953 and have steadily declined.

He is still investigating relationships between exposure and occurrences of lymphomas and some tumors that are expected to rise as the population ages. The risk for these cancers increases as people age and is even greater for those who have been exposed to radiation.

Finch's expertise in the health effects of radiation exposure led to a two-year stint as vice chair of the National Research Council's Committee on Radiological Safety in the Marshall Islands. Since 1985, residents of Rongelap had been living on the neighboring island of Megatto. They feared that fallout from the United States' detonation of the first thermonuclear device on nearby Bikini was still causing soil contamination and medical problems. Within two days of the detonation in 1954, all 300 residents of Rongelap were evacuated.

They returned to their homes in 1957 when it was declared safe by a U.S. Atomic Energy Commission study, but left again in 1985, suspicious of the project's findings. Finch says it was never clear why, but it was rumored that one or two residents had shown a high degree of radiation during routine check-ups. The high counts probably resulted from eating coconuts from trees that grew in the northern parts of Rongelap, where Finch and his group concluded there was still evidence of a radioactive element, cesium, in the soil.

"But with remediation - adding potassium which replaces cesium uptake in vegetation - the local food was deemed safe for consumption," he says. In 1994, the committee concluded that the residents could be safely resettled in their homes.

Marshall Island research studies over the years have confirmed that among the group there was only one case of leukemia, which could not be definitively linked to the explosion, and eight cases of thyroid cancer, hyperthyroidism and thyroid nodules among children. These were attributed to the bomb, because in a population of this size - about 300 people - less than one case would be expected.

They found no malignancies among the 12 crew members with radiation burns and radiation sickness who were aboard the Lucky Dragon, a Japanese fishing boat in the area at the time of the explosion.

Since 1995, Finch has been a member of a subcommittee of the federally funded National Council on Radiation Protection and Measurements, based in Bethesda, Md., which develops national standards for safe radiation dosages for adults, pregnant women and children. (Arthur Upton, MD, chair of this committee and a former director of the National Cancer Institute, is now on the faculty of the Environmental and Occupational Health Sciences Institute, a collaboration of UMDNJ-Robert Wood Johnson Medical School and Rutgers University.)

Finch says the U.S. population receives most of its lifetime natural radiation exposure from sun, soil, radon and radioactive potassium found in the human body. Diagnostic medical tests such as X-rays, CT scans and fluoroscopy account for 30 to 40 percent of the average person's total lifetime exposure. But, he points out, improvements in technology have decreased radiation exposure: "The amount is almost negligible in today's mammograms. They are very safe."

The subcommittee's members have been reviewing literature and information from all over the world in order to update safe, low-dose radiation exposure levels. These are particularly applicable for workers in the nuclear energy and radiology fields and for patients undergoing diagnostic tests. Although he is now officially retired, Finch often works in his hospital office. Artwork from Japan hangs on three walls. The fourth is lined with bookshelves holding textbooks, atlases, manuals and research data. A replica of a Japanese pagoda graces a cabinet.

Currently into what he calls his "fourth career," the researcher says he eventually plans to spend more time with his wife and visiting his children and four grandchildren. Finch celebrated his 76th birthday on August 6, which coincidentally falls on the date of the bombing of Hiroshima.

Photos by Peter Byron