AcknowledgmentThis decision aid was developed using the decision support format of the Ottawa Health Decision Centre, at the University of Ottawa and Ottawa Health Research Institute, Ontario, Canada.
This information is for you if:
- You lived in the United States between 1951 and 1963
- You are concerned that exposure to I-131 from the Nevada nuclear weapons tests may have affected your thyroid gland
- You want to consider options for thyroid screening
You will learn about:
- I-131 radioactive fallout and the risk of thyroid disease
- The pros and cons of thyroid screening
- How to decide if you should be screened
This workbook focuses on the pros and cons of thyroid cancer screening. It will help you make an informed decision about thyroid cancer screening. At the back of the booklet there is a worksheet to aid your decision-making.
We suggest you complete the worksheet and discuss it with a health care professional. Then you can make a final decision about thyroid cancer screening.
What is exposure to iodine-131?
Between 1951 and 1963, the United States conducted about one hundred above-ground nuclear weapons tests at the Nevada Test Site. These tests released radioactive materials, including iodine-131 (I-131), mainly during 1952, 1953, and 1957. I-131 released from the tests was carried by the wind and deposited on soil and vegetation throughout the United States. The areas most affected were downwind of the test site, to the north and east of Nevada. The areas least affected were on the West Coast of the United States. Because I-131 breaks down quickly, most exposure occurred within three months after each test.
The most common way people came in contact with I-131 was through contaminated milk. This was because the I-131 fell onto pasture grasses eaten by cows and goats, and was absorbed into their milk. The I-131 concentrated in the thyroid glands of people who drank milk. Children usually drink larger amounts of milk, so young children absorbed more I-131 than adults did. Children's thyroid glands are smaller as well, so the larger amount of I-131 was concentrated in less tissue. Children may have received 10 times the I-131 doses that adults did as a result of the Nevada tests. People, particularly children, who were exposed to I-131 from the tests, probably have an increased risk for thyroid disease.