U.S. Atomic Tests in '50s Exposed Millions to Risk, Study Says

WASHINGTON (July 29, 1997 12:04 p.m. EDT) -- Atmospheric nuclear bomb tests in Nevada from 1951 to 1962 exposed millions of American children to large amounts of radioactive iodine, a component of fallout that can affect the thyroid gland, the National Cancer Institute said on Monday.

The releases were larger than earlier estimates, and at least 10 times larger than those caused by the 1986 explosion at the Chernobyl nuclear plant in Ukraine. Under federal rules implemented in 1992 to deal with accidents at nuclear power plants, some of the tests would require protective actions like moving cows to shelter, or dumping their milk that would tend to have high concentrations of radioactive iodine. But no such precautions were taken at the time of the Nevada tests.

The cancer institute could not say whether any cases of thyroid cancer were caused by the fallout. But several experts said the levels of exposure could justify special monitoring for some people -- particularly those who were children in the 1950s and 1960s.

The information is from a 100,000-page study by the cancer institute that was ordered by Congress in 1982. The study was begun in 1983 and a draft report was completed in 1994. It has been undergoing revisions and rewriting since then.

A summary of the study, prepared for internal use at the Department of Energy and obtained by The New York Times, says that according to formulas in international use for calculating radiation damage, the doses were large enough to produce 25,000 to 50,000 cases of thyroid cancer around the country, of which 2,500 would be expected to be fatal. But the accuracy of those formulas is not certain, experts at the Department of Energy and elsewhere say, because the data on exposures at that level are limited.

The Department of Energy did not play a role in the study beyond providing some of the raw data. The department is a successor to the Atomic Energy Agency, which detonated most of the bombs.

The leader of the cancer institute study, Dr. Bruce Wachholz, said it was not clear that the exposures were high enough to increase the cancer risk. Studies of people in Utah immediately downwind from the test site did not find a clear association with thyroid cancer, Wachholz said.

The new study says the average dose to the approximately 160 million people living in the country in that period was 2 rads, a unit that stands for "radiation absorbed dose" and refers to the amount of energy absorbed by flesh. But, the cancer institute said on Monday, people living in "Western states to the north and east of the test site" received doses averaging 5 to 16 rads. Children aged 3 months to 5 years had doses 10 times higher, the institute said.

The main pathway for radioactive iodine exposure is through milk, which children consume in larger quantities than adults, especially in comparison to their body weight. When the contaminated milk is consumed, the human body delivers the iodine to the thyroid, where it can cause the development of cancerous nodules.

In addition, children's thyroids are smaller, and an equal quantity of the radioactive iodine in a smaller gland would deliver more energy per kilogram of tissue.

In contrast to the 50 to 160 rads those children are believed to have received, federal rules for nuclear power plant accidents call for taking protective action when the dose to human thyroids is anticipated to reach 15 rads. And another government agency, a branch of the Public Health Service, studying thyroid exposures around a government nuclear bomb factory at Hanford, Wash., has recommended medical monitoring for adults who absorbed 10 rads or more as children.

"There's a reasonable association" between radioactive iodine exposure and cancer, said Dr. Robert Spengler, the assistant director for science of the agency that made the recommendation, the Agency for Toxic Substances and Disease Registry. He said the association was demonstrated by a growing body of literature, from people in the Marshall Islands, where tests were also conducted, and elsewhere.

But Wachholz said "we really don't understand the dose-effect relationship" for radioactive iodine.

He said studies by his agency in the 1980s of 2,500 adults in Utah who had also been studied as children in the 1960s had not found a basis for a firm statistical finding of an association.

"I think it raises some serious questions," said E. Cooper Brown, chairman of the National Committee for Radiation Victims, a coalition of groups that includes soldiers exposed in the field, uranium miners and people who lived downwind of the test site. "I don't think you can say, 'aha, definitely.' That would be stepping way out of bounds. But you can't just shrug your shoulders and say, ah, it probably didn't hurt anybody."

The iodine form in question, iodine 131, is created when uranium or plutonium is split, in a reactor or a bomb. It is intensely radioactive, losing half of its radioactivity every eight days, meaning that within a few weeks it has disappeared. But if the release is large enough, it can be carried thousands of miles in the upper atmosphere and come to earth with enough energy remaining to deliver substantial doses.

The cancer institute said that its dose estimates were subject to "a large degree of uncertainty" because they were based on a small number of radiation measurements made at the time. One factor in estimating the dose is calculating the average amount of milk consumed, and its average time to market.

The institute said it had accomplished two of the goals that Congress set for it in 1982: developing a way to estimate the dose, and making the estimate. The third, assessing the risk of cancer from the exposures, is still to be finished, the institute said. It released the information after several days of reports about the contents of the study, which it plans to complete by October.

The cancer institute warned doctors in 1977 that the incidence of thyroid cancer had risen, to 3.9 cases per 100,000 population in a 1969-71 survey, from 2.4 cases in 1947. Among white people aged 20 to 35, the increase was "twofold to fourfold," the institute said, referring to people who were children at the time. But the cause is not clear; doctors had been using radiation to treat everything from acne to deafness from the 1920s on.

Thyroid cancer is a relatively rare disease. According to the American Cancer Society, it will kill about 1,230 people this year, out of a total 560,000 deaths from all forms of cancer. The disease has a cure rate of 90 percent to 95 percent, although patients require drug therapy for the rest of their lives.

The size of the doses being estimated surprised experts.

"This is especially tragic, because it could have been avoided," said Arjun Makhijani, the president of the Institute for Energy and Environmental Research, a nonprofit group based here that specializes in nuclear weapons. "They knew when the tests were and chose not to warn the population, and they located the test site in the West, knowing there would be fallout over the whole country."

The Department of Energy summary contrasted the new estimate of radiation dose to an estimate submitted to the old Joint Committee on Atomic Energy in 1959, which was .2 to .4 rads, or more than 100 times smaller than the average now cited for Western states.

The new study attempts to reconstruct the effects of 90 blasts at the Nevada Test Site, which was used by this country and Britain, across the 3,070 counties in the 48 contiguous states.

The study found Iodine 131 "hot spots" from a series of tests in 1953 that included large areas of New Mexico, Oklahoma, Iowa, Wisconsin, New York and Massachusetts, including one event in the Troy/Albany area. That event was briefly described by the Defense Nuclear Agency in 1982, when it said people living there may have received a dose of 2 rads to the whole body, and was widely reported at that time.

The Department of Energy summary of the new study, however, puts the Troy/Albany event in a new light, since 2 rads would not necessarily have required protective action under the rules that would be adopted later. But the thyroid dose there was high enough to have required protective action, had those rules been in effect at the time, the summary said.

By MATTHEW L. WALD, N.Y. Times News Service