Some Questions and Answers on the National Cancer Institute Report on Radiation Fallout from Nuclear Bomb Tests in the 1950s.
AP 02-AUG-97
Some questions and answers on the National Cancer Institute report on radiation fallout from nuclear bomb tests in the 1950s.
Q: What caused the radiation and how widespread was it? A: The government conducted 90 atmospheric nuclear bomb tests over the Nevada desert from 1951-1958, sending radioactive particles across most of the country, including iodine-131. The highest levels of fallout were in the Northwest and Midwest states. Nationwide, 24 counties in five states were exposed to an average of 9 to 16 rads, enough to be called hot spots. Dozens of other counties throughout the Farm Belt and Northwest received above-average fallout as well.
Q: What is iodine-131? A: It is a radioactive isotope that decays rapidly in the environment. Its radiation is reduced by half every eight days, meaning risk of exposure is limited to about two months. But once ingested, it concentrates in the thyroid and may increase the risk of thyroid cancer, especially in children, over a lifetime.
Q: How were people exposed? A: The overwhelming pathway was from drinking contaminated milk. I-131 was carried over wide areas as part of the fallout, and fell on pastures either as a solid or in rain where it was eaten by cows, contaminating their milk. Smaller amounts contaminated other dairy products and leafy vegetables.
Q: What were the levels of exposure? A: While the average cumulative exposure for all 160 million people in the country at that time was estimated at 2 rads, exposure in some counties was as much as 16 rads for all age groups. But for children, it was sometimes as much as seven times the average for a county, or up to 105 rads. A rad, or "radiation absorbed dose," is the amount of radiation energy absorbed by body tissues. Two rads is about five times the radiation delivered by a modern mammogram. The Nuclear Regulatory Commission requires protective action when accumulative doses to thyroids in adults is expected to reach 15 rads.
Q: Why were children most at risk from 1950s fallout? A: Children generally drink more milk than adults and they have a smaller thyroid, so more I-131 would concentrate in a small amount of tissue.
Q: If exposed to I-131, what is the risk of getting thyroid cancer?
A: The risk of thyroid cancer from childhood exposure to external radiation has been clear for many years. But health experts are unsure about the risk of thyroid cancer from I-131. Increased cases of thyroid cancer have been found among children exposed to high levels of I-131 from the Chernobyl nuclear accident. Researchers hope data from Chernobyl will clarify the cancer risks posed by I-131.
Q: How many additional thyroid cancers might result from the bomb test fallout?
A: Based on average doses in the counties examined, the National Cancer Institute estimates that as many as 10,000 to 75,000 children exposed in 1950s might develop fallout-associated thyroid cancer over their lifetime with 30 percent of those cancers already diagnosed.
Q: How common is thyroid cancer? A: It is a very slow growing cancer and accounts for 1 percent of all cancers in the United States. An estimated 16,100 cases will be diagnosed this year with 1,230 being fatal. It is a highly curable cancer with the five-year survival rate at 95 percent.
Q: How do I know if I may have been exposed to high levels of I-131 from bomb test fallout?
A: The National Cancer Institute has established an Internet web site that provides a list of every county in the 48 contiguous states and the average exposure level. Internet users can log onto the web site at http://rex.nci.nih.gov
Q: What should someone do if they are worried about fallout exposure?
A: Ask for a thyroid examination at the next scheduled doctor's visit.
Q: What does the government plan to do next? A: The full 100,000-page report on fallout exposure will be released next October. Various studies are underway, including the Chernobyl studies, to clarify the relationship of I-131 thyroid exposure and the risks of thyroid cancer. The National Academy of Sciences' Institute of Medicine will review the data from the NCI report to assess the health risks to individuals. The Clinton administration also is establishing a special group to examine the broader policy issues, such as possible compensation for individuals adversely affected by the bomb test contamination.