Radiation affected all of U.S.

Tuesday, July 29, 1997 | 9:47 a.m.

People living north and east of the Nevada Test Site received the highest exposure to radioactive particles believed to cause thyroid cancer when nuclear bombs exploded above ground during the 1950s.

The National Cancer Institute released a statement Monday based on a study due later this year naming 3,071 counties in the continental United States and the amounts of radioactive iodine exposing people, especially children, from bomb fallout.

The nuclear experiments blasted into Nevada skies sent radioactive particles across the entire country. Rain and snow caused "hot spots" where children who drank exposed milk were at higher risk of cancer.

Virtually everyone in the country got a small dose of radioactivity, but higher levels of radiation fell in thunderstorms and snowstorms as far away as upstate New York, experts familiar with the study said.

The fallout pattern traced by the scientists suggests that these radioactive particles crossed the U.S. border into Canada. But no cloud-tracking records are available for most of the tests.

Scientists said children with smaller thyroid glands are most vulnerable to radioactive iodine. Children were also at risk because they drank more milk than adults. Radioactive particles fell on grass, which was eaten by cows and eventually consumed by people in milk.

Smaller radioactive amounts came from eating other dairy products, eggs and leafy vegetables as well as inhaling the particles.

Because of all those factors, children 3 months to 5 years old from 1951 to 1958 averaged about 10 times the radioactive dose received by U.S. adults, the NCI said.

The average cumulative thyroid dose to the 160 million people in the country at the time averaged 2 rads, about the same amount that was used in diagnostic thyroid scans in the 1950s. People living in Western states north and east of the Test Site received doses averaging 5 to 16 rads.

A small number of earlier studies among people exposed to Iodine 131 from Test Site fallout suggest, but do not conclude, that such exposure is linked to cancer. The U.S. Public Health Service and the University of Utah in Salt Lake City studied thyroid disease and came to uncertain conclusions.

In 1997 an estimated 16,100 Americans will be diagnosed with thyroid cancer and 1,230 will die from the disease. Thyroid cancer is rare in children. The rate for women is more than twice as high as men. Thyroid cancer is highly curable.