Many atomic bomb survivors did not marry, fearing the bomb's after-effects could be passed on to their children.

It took decades to prove that fear groundless.

"We have not found any effects on the (survivors') children so far," said Dr. Yutaka Hasegawa, director of the Nagasaki branch of the Radiation Effects Research Foundation, a joint Japanese and American project.

A continuing 45-year-old study on atomic bomb survivors indicates bomb aftereffects were limited to those who actually lived through the Hiroshima and Nagasaki blasts.

In 1950, about 120,000 atomic bomb survivors - about one-fourth from Nagasaki - became part of the longest-running human health study ever attempted.

"We think we have another 10 to 20 years of work because ... 52 percent of the people we're studying still survive," said Dr. Mortimer Mendelsohn, the foundation's vice chairman.

Dr. Kazuo Neriishi, a foundation physician, said the studies are entering a critical period. That is because people exposed to the bombs as extremely young children are now entering their 50s, an age where cancer becomes more likely.

The question is whether cancer will show up 50 years after being exposed to radiation, Neriishi said.

The foundation has conducted hundreds of studies looking at cancers, blood, genetics, immune systems, bones, intelligence and other variables.

In 1947, Japan and the United States formed a joint Atomic Bomb Casualty Commission, which reorganized as the Radiation Effects Research Foundation in 1975.

The foundation's headquarters and most of its scientists are in Hiroshima. A branch in Nagasaki conducts exams.

Foundation studies have found strong evidence the atomic bombs led to increased chances of survivors contracting cancer - as well as some types of leukemia - in the thyroid, breast, colon, stomach, lungs and ovaries.

Those chances increased the closer a survivor was to the blast. Hasegawa said other factors also were important - such as whether someone was outside, in a wood building or in a concrete building.

Also, studies showed if a pregnant woman was irradiated, her baby had a good chance of becoming mentally retarded.

The studies also showed no link between the atomic bombs and other types of cancer and leukemia, nor any effects on fertility, some immune system diseases or aging.

The foundation barely looked at how survivors coped psychologically.

"It is a weak point. There is very little study on the psychological effects. The physical effects were overwhelming," Hasegawa acknowledged.

Mendelsohn added, "There is an enormous reluctance in Japan to get involved with that. One would suspect these people to be severely scarred in the psychological sense. They went through an enormous catastrophe.

"They saw families destroyed around them. I'd suspect they'd be ridden with guilt and shock and stress."

Bomb survivor study results are used extensively in the field of radiation health. Foundation scientists were consulted after Chernobyl and other radiation accidents in the Soviet Union and South America.

Because the foundation has 45 years of continuous health data on a large group of people, some research not related to the atomic bombs has been done.

For example, Mendelsohn said cholesterol levels found in a control group in one foundation study led to speculation that Western food might be affecting Japanese health.

The foundation has crossed paths with Battelle-Northwest researchers at Hanford.

Neriishi's studies on radiation and blood chemistry overlapped with Battelle cancer epidemiologist Richard Stevens' work studying iron in the diet.

The two collaborated on a study that showed too much iron in a man's diet could increase his risk of cancer.