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HTDS Guide - Overview

About the Hanford Thyroid Disease Study

The Hanford Thyroid Disease Study (HTDS) is a scientific study conducted to determine whether the risk of thyroid disease is increased among people exposed to radioactive iodine (iodine-131) from the Hanford Nuclear Site in Washington from 1944 through 1957.

The question was: "Did exposure to iodine-131 result in increased incidence of thyroid disease?"

Study Focus – Iodine-131 was the primary source of radiation for many people exposed to Hanford's radiation releases. Since iodine-131 concentrates in the thyroid gland when it is inhaled or consumed in contaminated food, the HTDS focused on thyroid disease.

Research Team – The HTDS was managed by the Centers for Disease Control and Prevention (CDC), an agency in the U.S. Department of Health and Human Services. The Fred Hutchinson Cancer Research Center in Seattle, Washington conducted the scientific and technical work. The HTDS Final Report was released in June 2002.

What Happened at Hanford

The Hanford Nuclear Site was built in the 1940s in southeastern Washington State to produce plutonium for nuclear weapons.

In the mid 1980s, as a result of public requests, the U.S. Department of Energy released previously unavailable or classified documents about past operations at Hanford. The information showed that large amounts of iodine-131 and other radioactive materials were released into the air from Hanford from 1944 through 1957.

Concerns about the possible health effects of Hanford's radiation led to a decision by Congress to mandate the HTDS in 1988.

How Were People Exposed to Iodine-131 from Hanford?

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How the Study Was Conducted

To study the health effects of Hanford's iodine-131, researchers investigated a group of people with a wide range of radiation doses to the thyroid. In this way, researchers could compare groups of people with similar characteristics (such as lifestyle and diet) but different levels of exposure.

Participant Selection – Other studies suggest that young children may be the most susceptible to the effects of radiation on the thyroid gland. Therefore, the HTDS selected participants who were young children when Hanford releases of iodine-131 were highest. Scientists also ensured that the HTDS participants included many people who lived in areas around Hanford where the highest thyroid radiation doses occurred.

From a sampling of 5,199 birth records, scientists were able to locate 3,440 people who were both willing to participate and able to provide the necessary data for evaluation of thyroid disease.

Data Collection – Participants underwent complete evaluations for thyroid disease, and provided detailed information about the places they lived and the quantities and sources of the food and milk they consumed.

Data Analysis – For each type of thyroid disease, the research team examined how the rates of disease varied in relation to participants' estimated radiation doses from Hanford's iodine-131.

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