Thyroid Researchers Scrutinize Fallout Data Scientists Studying Downwinders Downplay Impact Of National Cancer Institute Study On Their Work

Revelations of major radiation doses to some children in the West from Cold War bomb tests are getting the attention of a Seattle team tracking radiation exposures among Hanford downwinders.

Scientists from the $18 million, taxpayer-funded Hanford Thyroid Disease Study had been trying unsuccessfully to obtain the National Cancer Institute’s fallout data, said Dr. Ken Kopecky of the Fred Hutchinson Research Center.

“We asked for it a year ago,” Kopecky said.

They wanted the data to see whether radiation from bomb fallout was significant enough to influence their landmark study of Hanford’s radiation releases.

The NCI fallout study probably won’t have a major impact on the Hanford study, said Dr. Thomas Hamilton, the Hanford study’s chief medical expert.

That’s because 75 percent of the 5,200 people identified for the study who were exposed to Hanford’s iodine 131 releases as children or teenagers stayed in Eastern Washington, where they got very little additional radiation from fallout.

“Washington and the West Coast had the lowest fallout exposures in the nation,” Hamilton said.

But kids who lived near Hanford in the 1940s and then moved to Montana, Idaho, Kansas or other high-fallout states could have received substantial radiation from fallout, Hamilton said.

“We’ll have to look at that,” he said.

Last week, the NCI reluctantly released a summary of the fallout study after a series of newspaper stories about its contents and possible public health consequences. The full report will be released in October.

While the average adult American got a 2-rad thyroid dose from fallout from 1951 to ‘58, infants and small children in Idaho and Montana exposed to fallout from open-air bomb tests in Nevada got doses up to 160 rad.

Hanford’s doses to children in Eastern Washington also were significant.

From 1944 to 1948, Hanford’s plutonium reprocessing factories released clouds of radioactive iodine 131 into the air.

Children in Eastern Washington exposed to the largest Hanford emissions got a thyroid dose between 54 and 870 rad, according to a 1994 Hanford dose reconstruction study.

A 10-rad radiation dose has been shown to double a child’s lifetime risk of thyroid abnormalities, according to studies by Elaine Ron of the National Cancer Institute. But there’s little chance of dying from thyroid cancer because people can be successfully treated.

For the past five years, Hamilton has spent his weekends giving thyroid exams to 3,400 people in the Hanford study.

One of the main clinics, which run through mid-September, has been at Deaconess Medical Center in Spokane.

“We are finding a lot of thyroid disease,” Hamilton said.

But he won’t know until after the clinics end this fall whether the people with the thyroid disease are also those who got the highest doses from living near Hanford.

In the blind and confidential study, doctors conducting the clinics don’t know whether the people they’re examining are from one of the high dose areas, or whether they’re from an unexposed or minimally exposed area.

As the Hanford study has unfolded, Hamilton and his colleagues have been surprised by a growing epidemic of thyroid cancer among Russian children exposed to the 1986 Chernobyl nuclear accident.

Hamilton also studied thyroid disease among children and adults in the Marshall Islands who were exposed to fallout from nuclear bombs exploded in the Pacific.

Before Chernobyl, the earliest latency period for thyroid disease - the lag time between exposure to radiation and occurrence of the disease - was eight to nine years, Hamilton said.

“It’s much faster with Chernobyl. We have three-year-olds with cancer,” he said.

Chernobyl “is a clear case where radiation caused thyroid cancer. But you can’t yet say which radionuclides caused the cancer,” he said.

Hanford’s iodine exposures were quite different from Chernobyl’s, Hamilton said.

The Chernobyl kids were hit with very short-lived isotopes of iodine and other highly toxic elements that spewed out of the exploding reactor core.

At Hanford, kids weren’t exposed to those short-lived elements because the reactor fuel from which plutonium was chemically separated was allowed to decay before reprocessing started.

That allowed the short-lived elements to lose some of their power before the fuel was reprocessed, Hamilton said.

There were exceptions - such as the December 1949 “Green run” in which “green” or short-cooled fuel was used in a military experiment at Hanford that spread a plume of radioactive iodine through the lower Columbia River valley near Walla Walla.

The Hanford study will be a major step toward answering the still-unresolved question: What is the association between iodine 131 and thyroid disease?

“We really don’t know the magnitude of risk to children exposed to relatively low doses of radiation. That’s what the Hanford study will be answering,” Hamilton said.

After the clinics end in mid-September, scientists will begin to correlate the medical exams with estimated radiation doses for each person. The study will be made public in September 1998.

“It should be a strong study. We’ve tracked the very people who can answer the question of whether there’s increasing risk to the thyroid from an increasing dose” of radiation, Kopecky said.

, DataTimes