a guide to - centers for disease control and …a guide to the hanford thyroid disease study about...

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HANFORD

F I N A L R E P O R T

A Guide ToThe Hanford Thyroid Disease Study

About This Guide

Following more than 12 years of scientific research, the Centers forDisease Control and Prevention (CDC) and the Fred Hutchinson CancerResearch Center have released the Hanford Thyroid Disease Study(HTDS) Final Report.

The HTDS, mandated by Congress in 1988, was conducted to determinewhether thyroid disease is increased among people who were exposed aschildren to atmospheric releases of radioactive iodine from the HanfordNuclear Site (Hanford) in Washington State from 1944 through 1957.

CDC and the Fred Hutchinson Cancer Research Center prepared thisguide to help communicate the meaning of the HTDS to the public. The guide summarizes the findings, explains how and why the study was conducted, and includes information about the treatment of thyroid disease.

In the mid-1980s, the U.S. Department of Energy released documentsshowing that large amounts of radioactive materials, including iodine-131,had been released into the environment from Hanford since the mid-1940s.The public, health officials and scientists were concerned that these materials could have harmed the health of people living in the region.

The HTDS was conducted in response to these concerns. While nostudy can determine the cause of an individual case of thyroid disease,an epidemiological study, such as the HTDS, provides the best way todetermine whether disease has increased in a population exposed to apotentially harmful agent such as radiation.

Over the years, many thousands of people have been involved in theHTDS, including the 3,440 participants of the study. Members of thepublic, health care officials, physicians, scientists and many others havealso been involved.

CDC remains committed to providing useful information to the publicabout the HTDS and related issues. Please refer to page 22 of this guidefor additional sources of information.

Overview of the Hanford Thyroid Disease Study

A Guide to the Hanford Thyroid Disease Study – Final Report

ABOUT THE HANFORD THYROID DISEASE STUDY

The Hanford Thyroid Disease Study(HTDS) is a scientific study conductedto determine whether the risk of thyroid disease is increased amongpeople exposed to radioactive iodine(iodine-131) from the HanfordNuclear Site in Washington from1944 through 1957.

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

Study Focus — Iodine-131 was theprimary source of radiation for many people exposed to Hanford’sradiation releases. Since iodine-131concentrates in the thyroid glandwhen it is inhaled or consumed incontaminated food, the HTDSfocused on thyroid disease.

Research Team — The HTDS wasmanaged by the Centers for DiseaseControl and Prevention (CDC), anagency in the U.S. Department ofHealth and Human Services. TheFred Hutchinson Cancer ResearchCenter in Seattle, Washington conducted the scientific and technicalwork. The HTDS Final Report wasreleased in June 2002.

WHAT HAPPENED AT HANFORD (see page 2)

The Hanford Nuclear Site was built inthe 1940s in southeastern WashingtonState to produce plutonium for nuclearweapons.

In the mid 1980s, as a result of public requests, the U.S. Departmentof Energy released previously unavailable or classified documentsabout past operations at Hanford. Theinformation showed that largeamounts of iodine-131 and otherradioactive materials were releasedinto the air from Hanford from 1944through 1957.

Concerns about the possible healtheffects of Hanford’s radiation led to adecision by Congress to mandatethe HTDS in 1988.

HOW THE STUDY WAS CONDUCTED (see page 6)

To study the health effects of Hanford’siodine-131, researchers investigateda group of people with a wide rangeof radiation doses to the thyroid. Inthis way, researchers could comparegroups of people with similar characteristics (such as lifestyle anddiet) but different levels of exposure.

Participant Selection — Other studiessuggest that young children may bethe most susceptible to the effects of radiation on the thyroid gland.Therefore, the HTDS selected participants who were young childrenwhen Hanford releases of iodine-131were highest. Scientists also ensuredthat the HTDS participants includedmany people who lived in areasaround Hanford where the highestthyroid radiation doses occurred.

From a sampling of 5,199 birthrecords, scientists were able tolocate 3,440 people who were bothwilling to participate and able to provide the necessary data forevaluation of thyroid disease.

Data Collection — Participants underwentcomplete evaluations for thyroid disease,and provided detailed informationabout the places they lived and thequantities and sources of the foodand milk they consumed.

Data Analysis — For each type ofthyroid disease, the research teamexamined how the rates of diseasevaried in relation to participants’ estimated radiation doses fromHanford’s iodine-131.

Iodine-131 concentrates in

the thyroid.

People wereexposed

to Hanford’s iodine-131 throughvarious pathways,

including the consumption of

contaminated milk.

HOW WERE PEOPLE EXPOSED TO IODINE-131 FROM HANFORD?

THYROID GLAND

Thyroid Gland, Right Lobe

The thyroid gland is butterfly-shaped, with two lobes about the size of teaspoons. It is located in the front of the neck, below the Adam’s apple.

Trachea

Thyroid Gland, Left Lobe

Thyroid Cartilage

ABOUT THYROID DISEASE (see page 20)

The thyroid gland is located at thebase of the neck (see figure below).

Thyroid disease is common in thegeneral population. Thyroid diseaseincludes functional disorders andabnormal growth in the gland,including cancer. Most thyroid problems can be detected and treated.

If you are concerned about exposureto iodine-131 from Hanford or experience thyroid disease symptoms,you are encouraged to see your doctor for a thyroid evaluation.

FINDINGS (see page 9)

The HTDS data show that the risk ofthyroid disease was about the sameregardless of the radiation dosespeople received from Hanford. Inother words, no associations betweenHanford’s iodine-131 and thyroid disease were observed.

> Researchers studied all types of thyroid disease, a disease ofthe parathyroid glands, and abnormalities of the thyroid gland that can be seen on ultrasound examinations.

> The percentages of people witheach kind of thyroid disease orwith ultrasound abnormalitieswere about the same regardless oftheir estimated radiation dosefrom Hanford’s iodine-131.

The findings do not prove thatHanford radiation had no effect onthe health of the area population.However, they show that if there is an increased risk of thyroid disease from exposure to Hanford’siodine-131, it is probably too small toobserve using the best epidemiologicmethods available.

Thyroid disease was found in thestudy population. This was expectedbecause thyroid disease is commonin other populations, especiallyamong older people and women.

Based on a review of other studies,researchers found that the rates of thyroid disease in the HTDS population were generally consistentwith the rates of disease detected inother populations.

PUBLIC INVOLVEMENTAND SCIENTIFIC REVIEW (see page 18)

CDC formed a committee of scientistsand members of the public to adviseCDC on the design and implementationof the study. Members of the publicand public interest groups providedinput in public meetings and writtencomments to CDC throughout the study.

At the request of CDC, the NationalAcademy of Sciences peer reviewedthe HTDS at key points in the study.Peer review is an independent analysis of a study that providesconfidence that the correct methodsare being used.

1A Guide to the Hanford Thyroid Disease Study – Final Report

What Happened? A Brief History of Hanford 2

How the Study Was Conducted 6

Findings and Interpretations 9

Hanford Thyroid Disease Study Timeline 16

Public Involvement and Scientific Review 18

About Thyroid Disease 20

Information Resources 22

The HTDS Research Team 23

Table of Contents

> About the Hanford Nuclear Site

> Exposures to Radiation

> Classified InformationReleased

> Why the HTDS Was Conducted

SECTION SUMMARY> From 1944 through 1957, large

amounts of radioactive materialswere released into the atmosphere at Hanford.

> Milk consumption was the major waymost people were exposed to Hanford’siodine-131.

> Public concern led to the release ofpreviously classified informationabout Hanford’s operations.

> No other studies are directly comparable to the Hanford situation.

ABOUT THE HANFORD NUCLEAR SITEThe Hanford Nuclear Site occupiesabout 560 square miles in southeastern Washington State, adjacent to the towns of Pasco,Kennewick and Richland. Thefacility was the world’s first large-scale nuclear productionplant. It was constructed in theearly 1940s as part of theManhattan Project to produceplutonium for nuclear weapons.

Over the course of many years,large amounts of radioactivematerials (radionuclides) werereleased into the atmosphere andthe Columbia River as part of theplutonium production process.

The major radioactive releasesoccurred in the form of gases andparticles into the air from 1944through 1957. These releases

What Happened? A Brief History of Hanford

2 A Guide to the Hanford Thyroid Disease Study – Final Report

occurred mainly because ofincreased production and lack offilter systems. Changes in theproduction process over the yearsgreatly reduced releases into the air.

Many different kinds of radioactivematerials were released. Formany people living in the region,most of their dose was due toiodine-131 released into the air.

EXPOSURES TO RADIATIONIodine-131 was carried by windsto surrounding areas and depositedon vegetation. It was thenabsorbed in the milk of cows and goats that grazed on the contaminated vegetation.Drinking contaminated milkcaused most of the radiation dosefor most of the exposed people.

People were also exposed by eating contaminated fruits andvegetables, and by breathing contaminated air.

CLASSIFIED INFORMATIONRELEASEDFor a long time, details aboutHanford’s operations were notpublic. In 1986, as a result ofpublic concerns and requestsmade through the Freedom ofInformation Act, the U.S.Department of Energy (DOE)began releasing tens of thousands

People were also exposed by. . .


of pages of previously classified orunavailable documents.

The documents revealed to thepublic, for the first time, thatsubstantial quantities of radionuclides were released intothe environment from Hanford.

CDC convened a panel of independent scientists (HanfordHealth Effects Review Panel) toevaluate the DOE documents.Two of the panel’s most importantrecommendations were to conduct

a study to estimate the radioactivematerials released from Hanfordand to determine the feasibility ofstudying the health effects to thethyroid of that exposure.

The panel’s recommendationsevolved into what are known todayas the Hanford EnvironmentalDose Reconstruction Project(HEDR) and the Hanford ThyroidDisease Study (HTDS).

WHY THE HTDS WAS CONDUCTED The main reason why the HTDSwas conducted is that the public,health officials and scientists wereconcerned about the possible healtheffects of Hanford’s radiation.

Thyroid disease was a particularconcern because iodine concentratesin the thyroid gland and the DOE documents showed thatlarge amounts of iodine-131 werereleased from Hanford. Inresponse to public concerns,

HOW WERE PEOPLE EXPOSED TO IODINE-131 FROM HANFORD?

Iodine-131 concentrates in

the thyroid.

Iodine-131 was carried by

winds and deposited on

vegetation, fruitsand vegetables.

Cows and goatsgrazed on the

vegetation contaminated by

iodine-131.

Iodine-131 passedinto cow’s and goat’s milk and

was consumed byarea residents.

eating contaminated fruits and vegetables.

Iodine-131 released into air.

Most people received most of their dose from contaminated milk.

breathing contaminated air.

What Happened? A Brief History

of Hanford

Congress directed CDC to conduct a study of the effects ofHanford’s iodine-131 on thyroiddisease.

Many people ask, “Didn’t wealready know that Hanford radiation causes thyroid disease?”Over the years, many studies ofother populations have providedcompelling reasons to suspectthat the risk of thyroid diseasemight have increased in peoplewho were exposed to Hanford’siodine-131.

Nevertheless, the published literature left room for doubt,since none of the studies examinedcircumstances quite like those ofthe Hanford experience. The following are ways other radiationstudies are different from theHanford situation:

Type of radiation exposure –External irradiation by gammarays (such as the atomic bombings in World War II) or x-rays used in medical treatmentsmay have different effects thaniodine-131.

The people who were exposed –People who received iodine-131for treatment or diagnosis alreadyhad, or were likely to have, thyroid diseases, while peopleexposed to Hanford’s iodine-131were a general population,including some people with goodhealth and some with poor health.


Hanford Thyroid Disease Study (HTDS)

Hanford Environmental Dose Reconstruction Project (HEDR)

Purpose> Estimate type and amount of

radioactive materials released fromHanford.

> Model how radioactive materialsmoved through the environment andfood chain.

> Develop computer software for estimating individual doses.

> Estimate radiation doses to representative individuals in theHanford region.

Conduct of the Study> Began in 1987; final report issued

in 1994.

> The study was directed by an independent technical steering panelselected by deans of research universities in Washington and Oregon.

> The study was conducted by BattellePacific Northwest Laboratories originally under contract with the U.S.Department of Energy (DOE).Management responsibility was transferred to CDC in 1993.

IN THE LATE 1980S, THE FEDERAL GOVERNMENT BEGAN TWO HANFORD-RELATED STUDIES

Purpose> Study the risk of thyroid disease

among persons exposed to radioactiveiodine-131 from Hanford.

Conduct of the Study> Began in 1989; final report issued in

2002.

> Scientific and technical work were performed by the Fred HutchinsonCancer Research Center under contractwith CDC.

> The research team used HEDR computersoftware together with information provided by HTDS participants to estimate individual radiation doses tothe thyroid.

What Happened? A Brief History of Hanford

WASHINGTON

OREGON IDAHO

HEDRStudy Area


How big the doses were – Doses ofiodine-131 used for medical treatments are much higher thananyone is likely to have receivedfrom Hanford’s iodine-131. Dosesfrom Chernobyl’s fallout werehigher as well.

How long people were exposed –External irradiation typicallyoccurs within a few seconds orminutes. Medical exposures ofiodine-131 typically occur overdays to weeks. Exposure to

the question of whether thyroiddisease had been increased byHanford’s iodine-131.

No study can determine the cause of an individual case ofthyroid disease. However, an epidemiological study, such as theHTDS, provides the best way to determine whether disease hasincreased in a population exposedto a potentially harmful agent suchas radiation. ■

Chernobyl’s fallout occurred fromweeks to months. In contrast,many of those exposed to Hanford’siodine-131 were exposed over aperiod of several years.

Because other studies haveaddressed situations differentfrom Hanford in important ways,it was necessary to study peoplewho were actually exposed toHanford’s iodine-131 in order toget the most reliable answer to

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Chelan

Kittitas

Yakima

Klickitat

Sherman

Wasco

Jefferson Wheeler

GilliamMorrow

Umatilla

Grant

Douglas

Lincoln

Whitman

Columbia

Garfield

AsotinLewis

Latah

Spokane

Nez Perce

Benewah

Kootenai

Bonner

PendOreille

Benton

Walla Walla

Franklin

Adams

Okanogan Ferry

Stevens

HANFORD

Scientists used computer software developedunder the HEDR Project to estimate radiationdoses to the thyroid that HTDS participantsaccumulated while living within the HEDRStudy Area.

The HEDR Study Area constitutes a 246-by-306mile area around Hanford.

Source: Hanford Environmental Dose ReconstructionProject (HEDR)

]HANFORD NUCLEAR SITE AND SURROUNDING AREAS

What Happened? A Brief History

of Hanford

> Study Group Selection

> How Data Were Collected

> How Data Were Analyzed

> Consideration of OtherSources of Radiation

> Native Americans and the HTDS

in young children may be more sensitive to the effects of radiation.

The study participants represent arange of possible doses of iodine-131 from Hanford, from thehighest doses to very low doses.

Starting from birth certificates of5,199 people born between 1940and 1946, investigators were ableto locate 94 percent of the group(4,350 people still living and 527deceased). Of these, 3,440 werewilling and able to participate fully.

Of the 3,440 study participants,249 moved out of the Hanfordregion before Hanford operationsbegan and did not move back intothe region any time before the endof 1957. They are referred to as“out of area” participants in theHTDS. Because their thyroiddoses could not be estimated withthe computer models used by theHTDS, out of area participantswere included in the data analysesas a separate group (see Figures 1-4in Findings and Interpretations).

HOW DATA WERE COLLECTEDTo estimate participants’ radiationdoses as precisely as possible, participants were asked to providedetailed information about thesources and amounts of foods andmilk they consumed, and wherethey lived during the years 1944through 1957. The largest

SECTION SUMMARY> The HTDS studied a group of people

from the Hanford region who wereyoung children at the time of thelargest radiation releases fromHanford.

> Each participant attended a medicalclinic for a complete diagnostic evaluation for thyroid disease.

> Scientists analyzed whether study participants with higher radiationdoses had more thyroid disease thanthose with lower doses.

> Based on information from NativeAmerican Tribes and Nations, a studysuch as the HTDS in Native American populations alone was not feasiblebecause it would have too littlechance of detecting any healtheffects from Hanford’s iodine-131.

STUDY GROUP SELECTIONThe HTDS study population represents a sampling of peopleborn between 1940 and 1946 tomothers who lived in seven countiesin Washington State: Benton,Franklin, Adams, Walla Walla,Okanogan, Ferry and Stevens.

All of the participants wereyoung children at the time of thelargest radiation releases fromHanford. It is believed that youngchildren receive a higher dose tothe thyroid for the same level ofexposure than do adolescents andadults, and that the thyroid gland

How the Study Was Conducted



amounts of iodine-131 werereleased from Hanford duringthose years, especially in 1945.

Of course, participants could notbe expected to remember all thedetails of their childhood years,so whenever possible the information was obtained fromsomeone with personal knowledgeof the participant’s early life,often the participant’s mother.

In addition, participants attendeda medical clinic for a completediagnostic evaluation for thyroiddisease. At the clinic, each participant:

> Completed a personal interviewregarding his/her residential history, dietary history, past medical or occupational radiationexposures, and any history ofthyroid disease.

> Received a thyroid ultrasoundexamination.

> Provided a blood sample to test for thyroid function andthe presence of antibody markers for autoimmune thyroiditis. Serum calcium was also measured to test for hyperparathyroidism.

4,877 — Were located(4,350 living, 527 deceased*)

3,440 — Participated fully in the study.

*An analysis of the underlying causes of death revealed no indication that thyroid disease or thyroid cancercaused any of the deaths.

> Received a physical examinationof the thyroid by two experiencedthyroid physicians, each independently of the other.

If the person had a history of thyroid disease, medical recordsconcerning that disease were also sought.

If any thyroid abnormality wasfound, the participant was advisedto see a health care provider forevaluation or treatment.

The research team estimated eachparticipant’s radiation dose to thethyroid. To do this, scientists usedcomputer software developed underthe Hanford Environmental DoseReconstruction Project (HEDR)together with the information provided by the HTDS participants.

HOW DATA WERE ANALYZEDIn analyzing the data, researcherslooked for what is called a “dose-response.” A dose-responseis when risk of disease increaseswith increasing dose of radiation.If a study finds a dose-response, itprovides very strong evidencelinking radiation to the disease.

In the case of the HTDS, researchersstudied how rates of thyroid diseasein the study group varied in relation to participants’ radiationdoses from Hanford’s iodine-131.

HOW MANY PEOPLE PARTICIPATED IN THE HTDS?

Total number of potential participants...

5,199 — Identified from birthrecords


The HTDS is an “internally controlled study.” This approachenables researchers to comparegroups of people who have similarcharacteristics (such as age, diet,lifestyle or environment) but different levels of exposure.

This approach of using one population composed of individualswith different levels of exposurehas been used extensively inassessing the effects of radiationexposure in human populations.

A less effective approach wouldbe to compare the study group toa separate population presumedto be unexposed to radiation(“unexposed control group”).That approach would be lessdesirable because thyroid diseasemay be a function of a number offactors other than exposure toradiation, and those factors maydiffer considerably between different populations.

Had the HTDS used an unexposedcontrol group from another partof the country, scientists couldnot have known whether any differences in the rates of diseasebetween the groups were due to adifference in exposure levels orsome other factor.

CONSIDERATION OF OTHERSOURCES OF RADIATIONScientists specifically designed theHTDS to assess the health effectsof iodine-131 from Hanford.However, to be sure that anyapparent health effects ofHanford’s iodine-131 were notactually due to other causes,researchers needed to considerother possible radiation exposures.

For the HTDS, the research teamconsidered exposures due to fallout from nuclear testing at theNevada Test Site in the 1950s.They also considered exposuresthat individual study participantsmay have received from diagnosticor therapeutic irradiation, orfrom jobs that involved workingwith radioactive materials. Byexplicitly accounting for suchexposures in the analyses of thedata, researchers were able to single out the effects of Hanfordradiation.

NATIVE AMERICANS AND THE HTDS The HTDS research team conducted a feasibility study todetermine whether it would bepossible to conduct a study likethe HTDS of the Native American


populations that were exposed toHanford’s iodine-131. ThoseTribes and Nations include: Colville,Couer d’Alene, Kalispell, Kootenai,Nez Perce, Spokane, Umatilla,Warm Springs and Yakama.

A separate feasibility study wasconducted because it was recognized that aspects of thelifestyles of Native Americans differed from non-Natives, particularly regarding diet, foodsources and seasonal residencechanges. All of these factorscould have affected the dose people received.

Eight of the nine tribes providedtribal-specific information for usein estimating the number of tribalmembers exposed and the likelymagnitude of their radiation doseto the thyroid. Based on theseestimates, it was determined thata separate study like the HTDSamong Native Americans wouldnot be feasible because it wouldhave too little chance of detectingany health effects from Hanford’siodine-131.

Nevertheless, Native Americanswere included in the HTDS if theywere identified in the group of5,199 that made up the studycohort. ■


SECTION SUMMARY> The HTDS is a scientific study

conducted to determine whetherthere was an increased risk of developing thyroid disease amongpeople exposed to iodine-131 from Hanford.

> The HTDS data show that the risks ofthyroid disease were about the sameregardless of the radiation doses people received.

> The findings mean that if there is anincreased risk of thyroid disease fromexposure to Hanford’s iodine-131, it is probably too small to observeusing the best epidemiologic methodsavailable.

> Researchers found that the occurrenceof thyroid disease in the study groupwas about the same as has beenreported for other populations.

STUDY OBJECTIVE The HTDS is an epidemiologicalstudy conducted to determinewhether thyroid disease isincreased among people whowere exposed as young childrento releases of iodine-131 from theHanford Nuclear Site from 1944through 1957.

The HTDS was designed to testwhether the risk of thyroid diseasein a group of people exposed toHanford’s iodine-131 differed inrelation to the radiation dosestheir thyroid glands received.

> Study Objective

> Findings

> How the Prevalence ofThyroid Disease in the HTDSCompares to OtherPopulations

> How the HTDS FindingsCompare to Other RadiationStudies

> How Reliable Are the Resultsof the HTDS?

The study cannot determine thecause of an individual’s disease.

FINDINGSThe HTDS data show that therisks of thyroid disease wereabout the same regardless of theradiation doses people received.In other words, no associationsbetween Hanford’s iodine-131and thyroid disease were observed.

The findings do not prove thatHanford radiation had no effecton the health of the area population.However, the findings show thatif there is an increased risk ofthyroid disease from exposure toHanford’s iodine-131, it is probablytoo small to observe using the bestepidemiologic methods available.

Researchers studied all types ofthyroid disease, as well as a diseaseof the parathyroid glands calledhyperparathyroidism, and abnormalities of the thyroidgland that can be seen only on ultrasound examinations.

In each case, the results were thesame. The percentages of peoplewith each kind of thyroid diseaseor with ultrasound abnormalitieswere about the same regardless of their estimated radiation dosefrom Hanford’s iodine-131.There were no statistically significant dose-responses for any of the diseases or ultrasoundabnormalities studied.

Findings andInterpretations



Non-Disease OutcomesThe proportion of participantswith thyroid abnormalities thatcould be seen on their ultrasoundexaminations did not increase significantly with increasing radiation dose (see Figure 4).

Mortality in the Study PopulationOf the 5,199 people originallyidentified for inclusion in the

0%

2%

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6%

8%

10%

Thyroid radiation dose (mGy)*

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*MilliGray (mGy) is a measure of radiation dose. **Out of area participants: No dose estimate available (see page 6).

Figure 1. OCCURRENCE OF THYROID CANCER AMONG FEMALE AND MALE HTDS PARTICIPANTS

out ofarea**

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percentage of cases among women

percentage of cases among men

Thyroid disease was found in thestudy population. This wasexpected because thyroid diseaseis common in other populations,especially among older peopleand women.

Researchers found that the ratesof thyroid disease in the HTDSpopulation were generally consistentwith the rates of disease detected inother populations.

Thyroid DiseaseResearchers studied all kinds ofthyroid disease, including thyroidcancer (see Figure 1), benign thyroid nodules (see Figure 2)and hypothyroidism or underactivethyroid (see Figure 3).

For each type of thyroid disease,the study found that people withhigher doses had about the sameamount of disease as people withlower doses.

HyperparathyroidismThe study found no evidence thatthe risk of hyperparathyroidismincreased with increasing radiationdose. This disease occurs whenthe parathyroid glands producetoo much parathyroid hormone,resulting in high calcium levels inthe body.

However, the study did detect astatistically significant relationshipbetween radiation dose anddecreasing calcium levels.

Average levels of calcium in theblood were slightly lower —though still within the normalrange — in people with higherestimated thyroid radiation doses.

Researchers have no explanationfor the finding. Nevertheless, thedecrease in calcium levels was sosmall that even participants withthe highest doses had calcium values within the normal range.



study, researchers found that 527were deceased. Researchers wereable to locate death certificatesfor 504 of the 527 deceased individuals. None of the deathcertificates indicated that any thyroid disease, including thyroidcancer, was responsible for any ofthe deaths.

Overall mortality rates in thestudy population were about thesame as those in the state of

before the releases of iodine-131from Hanford began.

HOW THE PREVALENCE OF THYROID DISEASE IN THE HTDS COMPARES TO OTHERPOPULATIONS People often ask how the occurrence of thyroid disease inthe HTDS compares to otherpopulations not exposed toiodine-131 from Hanford. Basedon a descriptive analysis of themost comparable informationfrom other studies, the HTDSresearch team found that the ratesof thyroid disease in the studypopulation are generally consistentwith the published literature onother populations. In other words,there is no indication that the levels of disease in the HTDSpopulation are any higher thanwhat have been reported aroundthe world in a variety of differentcircumstances.

There are a number of reasonswhy a more definitive comparisonbetween the HTDS populationand other populations groups isnot possible:

> There are no national estimates of thyroid diseases to which the HTDS can be compared.Moreover, populations with different characteristics and different exposures may exhibitvery different disease rates.

Washington for the same timeperiod. However, mortality ratesfor non-hereditary causes due toconditions that occurred beforeor shortly after birth were somewhat higher than those inthe state of Washington for thesame period. The reasons for thishigher death rate are not known,though it is not likely related toHanford’s iodine-131 becauseincreased death rates from thesekinds of conditions occurred even

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Figure 2. OCCURENCE OF BENIGN THYROID NODULES AMONG FEMALE AND MALE HTDS PARTICIPANTS

*MilliGray (mGy) is a measure of radiation dose.**Out of area participants: No dose estimate available (see page 6).



a person gets in his or her diet, a person’s age at the time of exposure, how much time haspassed since the exposure and themethods researchers used tosearch for the disease.

Nevertheless, much can belearned from other radiation studies. For example, scientistsagree that high doses of externalradiation, as well as high doses ofinternal radiation received in


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Figure 3. OCCURRENCE OF HYPOTHYROIDISM AMONG FEMALE AND MALE HTDS PARTICIPANTS

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> Identification of thyroid diseasein a population depends to alarge extent on how aggressivelyone looks for the disease. Forexample, scientists are muchmore likely to detect thyroidnodules using ultrasound (suchas the HTDS) than they wouldconducting a routine thyroidexamination.

> Physicians use different definitions of various thyroidand other conditions, making itdifficult to compare prevalenceof diseases in different popula-tions. Such is the case withboth hyperparathyroidism andhypothyroidism.

> The methods used for detectingthyroid disease and other conditions have changed, making it difficult to comparestudies conducted during different time periods. Forexample, estimates of theprevalence of autoimmune thyroiditis and thyroid nodulesvary widely depending on themethod of detection.

Nevertheless, the best estimatesof the prevalence of thyroid diseases, including thyroid cancer,in the general population are consistent with that found in theHTDS population group.

HOW THE HTDS FINDINGSCOMPARE TO OTHER RADIATION STUDIESNo other radiation studies aredirectly comparable to the Hanfordsituation, and drawing comparisonswith other studies is difficultbecause many factors affect thyroidhealth. Factors include the typeof radiation (internal or external),the doses received, the rate atwhich the doses were received,how much non-radioactive iodine



cancer. People whose thyroidglands were exposed in childhoodto high levels of external radiation from x-ray treatmentsof the head and neck are also atincreased risk. (Medical uses ofx-ray treatments of children havechanged since the 1960s.)

What distinguishes these situationsfrom Hanford is that the exposureswere external and not fromiodine-131, the radiation doseswere much higher and the doseswere delivered in very short periods of time.

Mix of Internal and External Exposures

Studies show that children andadults exposed to internal andexternal radiation from nucleartesting in the Marshall Islands(largest test in 1954) have anincreased risk of thyroid nodules.Other studies show a largeincrease in thyroid cancer amongchildren exposed to iodine-131and other radiation fromChernobyl in 1986.

Neither situation is directly comparable to Hanford becausethe radiation received in bothinstances was a mixture of internal and external exposures,and the doses were higher anddelivered over shorter periods oftime. In the case of Chernobyl,iodine deficiency in the population

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0–9 10–49 50–99 100–199 200–399 400+



Figure 4. OCCURRENCE OF ULTRASOUND-DETECTED THYROID ABNORMALITIES AMONG FEMALE AND MALE HTDS PARTICIPANTS

0%

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short periods of time, increase therisk of certain thyroid diseases.There is also evidence that therisk from radiation is greater forpeople exposed at younger ages.

Much less is known about situations such as Hanford,where populations are exposed tolower levels of internal radiationfrom iodine-131 over prolongedperiods of time.

The following is a review of otherimportant radiation studies.(Refer to the chart on page 14.)

External Exposures

Studies of survivors of the atomicbombings of Hiroshima andNagasaki during World War IIshow that people exposed to highlevels of external gamma radiationface an increased risk of thyroid



MIX OF INTERNAL AND EXTERNAL EXPOSURESHigher Doses

Lower Doses

INTERNAL EXPOSURESEXTERNAL EXPOSURES

SUMMARY OF RADIATION STUDIES

X-RAY TREATMENT OF CHILDREN> Exposure to x-ray treatment.> Exposure lasted seconds

to minutes.> Studied exposure in

childhood.> Exposure resulted in

increased risk of thyroidcancer.

HIROSHIMA AND NAGASAKI> Exposure primarily to

gamma rays; some neutronexposure.

> Exposure lasted seconds. > Studied exposure at all ages.> Exposure resulted in

increased risk of thyroidcancer, with greatest risk in children; limited evidenceof an increased risk ofautoimmune thyroiditis.

MARSHALL ISLANDS> Exposure to iodine-131

plus other internal andexternal radionuclides.

> Exposure lasted weeks.> Studied exposure at all

ages.> Exposure resulted in

increased risk of thyroid nodules andhypothyroidism, primarily in children.

CHERNOBYL> Exposure to iodine-131

plus other internal andexternal radionuclides.

> Exposure lasted days toweeks.

> Studied exposure inchildhood.

> Exposure resulted inlarge increased risk of thyroid cancer in children. Iodine deficiencyin the diet may also be a contributing factor.

NEVADA TEST SITE> Exposure to iodine-131 plus other internal

and external radionuclides.> Exposure lasted weeks to months.> Studied exposure in children.> Exposure resulted in increased risk of

thyroid nodules; some indication of anincreased risk of thyroid cancer.

MEDICAL USES OF IODINE-131 FOR TREATMENT> Exposure to iodine-131. > Exposure lasted days to weeks.> Studied exposure at all ages,

primarily adults.> Exposure resulted in increased risk

of hypothyroidism (intent of thetreatment); no clear evidence of anincreased risk of thyroid cancerfrom iodine-131 exposure.

MEDICAL USES OF IODINE-131 FOR DIAGNOSIS> Exposure to iodine-131. > Exposure lasted days to weeks.> Studied exposure at all ages,

primarily adults.> Exposure not associated with an

increased risk of thyroid cancer.

HANFORD> Exposure almost entirely to

iodine-131. > Exposure lasted months to years.> Studied exposure in children.> Exposure not associated with an

increased risk of thyroid disease.



may also be a factor in the rate ofthyroid disease.

A study of people exposed aschildren to fallout from nucleartesting in the 1950s at theNevada Test Site is called theUtah Study. This study found anincreased risk of thyroid neoplasia,which is a category of diseasethat the researchers defined toinclude both thyroid cancer andcertain kinds of benign nodules.However, there was no clear evidence that the risk of thyroidcancer alone was increased.

The study is considered the most comparable to the Hanford situation, but there are importantdifferences. While exposure waslargely from iodine-131, it alsolikely included short-lived radio-active iodines as well as externalradiation. In addition, the Utahexposures were concentrated overshorter time periods.

Internal Exposures

There have been epidemiologicalstudies of the effect of iodine-131alone. However, these have allbeen based on people who receivediodine-131 to treat thyroid disease, or to diagnose suspectedthyroid disease. People exposedto radioactive iodine for medicalreasons (primarily for the treatmentof Graves disease) generally

so long ago is simply not possible.In addition, the amounts ofiodine-131 released from Hanford,and how that iodine-131 movedthrough the environment, are notknown exactly.

In order to account for the effectsof this uncertainty about the participants’ doses, HTDSresearchers performed special statistical analyses. They alsoexamined whether risks of thyroiddiseases and thyroid ultrasoundabnormalities differed accordingto where the participants livedand/or how much milk they consumed, rather than their estimated doses. None of theseadditional analyses led to a conclusion that risks of thyroiddisease increased with increasingexposure to Hanford’s iodine-131.

No epidemiological study canstate with absolute certaintywhether or not an exposure (suchas Hanford’s iodine-131) hasaffected people’s health.Nevertheless, studies such as theHTDS can be conducted in ways,and with enough participants, toprovide confidence that if anassociation exists it is likelysmall. In the HTDS, scientists didnot observe an association using acareful study design, thoroughclinical evaluation, and severalalternative approaches for estimating radiation dose andanalyzing study data. ■

received very high doses. Whileseveral studies found an increasedrisk of thyroid cancer, theresearchers concluded this waslikely due to the patients’ underlying thyroid diseases, nottheir iodine-131 exposures.

People exposed to radioactiveiodine for diagnostic purposesreceived much lower doses. Studieshave not found an increased riskof thyroid cancer associated withdiagnostic exposures.

HOW RELIABLE ARE THERESULTS OF THE HTDS?An important consideration inany epidemiological study is thereliability of the information. Inthe case of HTDS, researcherscould be confident that theirassessments of thyroid diseasewere very reliable because participants received thoroughexaminations of their thyroidglands by experienced doctors.

On the other hand, estimating radiation doses to the participants’thyroid glands was inherentlyuncertain. This is because theirdoses depended not only onwhere they lived, but also on thequantities and sources of the foodand milk products they consumedwhen they were infants andyoung children during 1944through 1957. Highly accuraterecollection of information from


Hanford Thyroid DiseaseStudy Timeline


1988DOE forms Technical Steering Panel

of scientists, representatives of Native American Tribes and community

representatives to oversee HEDR.

Congress directs CDC to conduct a study of thyroid disease in

the area around Hanford.

1989CDC awards contract to

Fred Hutchinson Cancer Research Centerfor HTDS. Work begins on HTDS

protocol and pilot study.

1991HTDS Advisory Committee

meetings begin on a regular basis. All meetings open to the public.

1992HTDS pilot study design and protocol

approved by the Federal Office of Management and Budget and the Institutional Review Board of

Fred Hutchinson Cancer Research Center.

1990HTDS scientists begin publiccommunications with public

meetings, mailings, newsletters and toll-free number.

U.S. Department of Health and HumanServices appoints HTDS Advisory

Committee (scientists, public health officials, public and Native American

representatives) to advise CDC on designand implementation of HTDS.

HTDS scientists hold public meetings in Northwest to solicit comments from the public and scientists on pilot study

design and protocol.

1993HEDR funding transferred from DOE to CDC.

1994HEDR final reports published.

1986 and 1987U.S. Department of Energy (DOE) releasesclassified documents describing radiation

releases at Hanford.

1986CDC forms an independent panel of

scientists (Hanford Health Effects ReviewPanel) to evaluate DOE documents.

Hanford Health Effects Review Panel recommends two studies: 1) to estimate

radiation doses received by area residents(which became known as the Hanford

Environmental Dose Reconstruction Project(HEDR)), 2) to examine the feasibility ofstudying the potential health effects ofiodine-131 among exposed populations

(which led to the HTDS).

CDC forms second independent panel(Hanford Historical Documents Review

Committee) to continue analysis of DOE documents.

1987Battelle Pacific Northwest Laboratories

begins work on HEDR under DOE contract.

1986 – 1987 1990 1993 – 1994

1988 – 1989 1991 – 1992


National Academy of Sciences conductspeer review of HTDS Analysis Plan (plan that describes how the data

would be analyzed).

HTDS Advisory Committee approvesHTDS Analysis Plan.

HTDS data collection completed. Data analysis begins.

CDC and Fred Hutchinson Cancer ResearchCenter release HTDS Draft Report for

purpose of scientific peer review and public comment. CDC and HTDS

scientists hold public meeting in Richland to review draft findings.

CDC holds five-month public comment period on HTDS Draft Report.

National Academy of Sciences conducts peer review of HTDS Draft Report.

NAS holds public meeting in Spokane.

HTDS Pilot Study Report issued. Full epidemiologic study determined feasible.

National Academy of Sciencesconducts peer review of HTDS Pilot

Study Report and finds study design to be sound science.

HTDS Advisory Committee reviews pilot study results and recommends

proceeding to full epidemiologic study.

Fred Hutchinson Cancer Research Centercompletes HTDS Draft Report.

CDC scientists evaluate report.

CDC convenes ad hoc review group of independent scientists who provide written reviews and opinions on HTDS Draft Report.

2000National Academy of Sciences issues its

report and recommendations on HTDS Draft Report.

2000 – 2002CDC and Fred Hutchinson Cancer ResearchCenter conduct additional technical workbased on National Academy of Sciences recommendations, and comments fromindependent scientists and the public.

2001CDC conducts audience research to

prepare for communication of HTDS FinalReport. Research includes discussiongroups with HTDS participants, Hanfordpublic, and local government and public

interest group representatives.

2002CDC and Fred Hutchinson Cancer Research

Center release the HTDS Final Report.

1995 1998 2000 – 2002

1997 1999

Hanford Thyroid DiseaseStudy Timeline

> Reviewers and Their Roles

> Review Process

The HTDS Advisory CommitteeThe HTDS Advisory Committee(officially known as the HanfordThyroid Morbidity Study AdvisoryCommittee) was created to advise CDC on the design and implementation of the study.

The committee was chartered bythe U.S. Department of Healthand Human Services. Scientists,state health officials, environmentalgroups, Indian Nations and thepublic were represented in thegroup.

The committee met regularly from1991 through 1999. At eachmeeting the public was given anopportunity to ask questions andoffer their own views on the study.

National Academy of Sciences (NAS)The NAS is one of the country’smost respected scientific organizations. At three points inthe study (Pilot Study, AnalysisPlan and HTDS Draft Report), anNAS committee peer reviewed thestudy and made recommendationsto the research team. The NAS committee included epidemiologists,statisticians and other scientists.

Peer review is an independent scientific evaluation that helpsensure that a study is of highquality.

SECTION SUMMARY> The public commented on design and

implementation issues throughoutthe study.

> The HTDS Advisory Committee provided ongoing advice to CDC onthe design and implementation of thestudy.

> A committee of the National Academyof Sciences peer reviewed the HTDSat three points: Pilot Study, AnalysisPlan and HTDS Draft Report.

> CDC convened other independent scientists to review the HTDS DraftReport.

REVIEWERS AND THEIR ROLESThroughout the study, HTDSresearchers received input andsuggestions from a wide varietyof sources.

The PublicIndividuals and public groupsprovided input in a variety ofways, including participation inpublic meetings and the HTDSAdvisory Committee, and withwritten comments to CDC.

The research team communicatedwith the public throughout thestudy using newsletters, mailersand a toll-free number. Under aseparate project funded by theFederal Government, theHanford Health InformationNetwork provided informationabout radiation health effects.

Public Involvementand Scientific Review



Independent ScientistsIn 1998, CDC convened a groupof independent scientists withexpertise in thyroid disease, radiation and epidemiology toreview the HTDS Draft Report.Their evaluation was made availablein a public report.

Other independent scientists offeredcritical review on the pilot studydesign and protocol during theearly phase of the study.

REVIEW PROCESSThe HTDS involved extensive scientific peer review and publicinvolvement.

Study DesignThe study design, or protocol,describes all the methods used forconducting the study, such as recruiting participants and conducting thyroid examinations.

Public interest groups, scientistsand members of the public wereinvited to comment on the protocolin public meetings in the Northwest.They were also encouraged tosend written comments to CDC.

The protocol was evaluated bythe HTDS Advisory Committee,and approved by CDC, theInstitutional Review Board of theFred Hutchinson Cancer ResearchCenter and the Federal Office ofManagement and Budget.

Committee. In addition, the publicwas invited to offer its own viewson the plan.

HTDS Draft ReportCDC released the HTDS DraftReport in January 1999. Anextensive review by the NAS concluded that the study was scientifically sound but had probablyoverstated the certainty of thefindings. The NAS recommendeda number of technical revisionsand clarifications.

Following the review, the researchteam conducted additional technicalwork to address the NAS recommendations as well as thosereceived from the public andother independent scientists. TheHTDS Final Report representscompletion of the study. ■

Pilot StudyIn the early 1990s, researchersbegan recruiting participants andcollecting data for a pilot studyto determine the feasibility of alarge-scale epidemiologic study.A Pilot Study Report was issuedin 1994, peer reviewed by theNAS, and approved by the HTDSAdvisory Committee. In 1995,both panels agreed that a full-scaleepidemiologic study was feasible.The NAS also recommended thatthe researchers develop an analysisplan describing how the datawould be analyzed.

Analysis PlanThe Analysis Plan was completedin 1997 and peer reviewed by theNAS. It was also reviewed andapproved by the HTDS Advisory

Reviewed variousaspects of the

science throughout the study.

Conducted scientific peer

reviews in 1995,1997 and 1999.

Participated in public meetings

and provided written commentsto CDC throughout

the study.

Advised CDC on design and

implementationissues from

1991 through1999.

THE PUBLIC ANDPUBLIC INTEREST

GROUPS

NATIONALACADEMY OF

SCIENCES

HTDS ADVISORYCOMMITTEE

OTHERINDEPENDENT

SCIENTISTS

THE REVIEWERS AND THEIR ROLES

Public Involvementand Scientific Review

> A Look at Thyroid Disorders

> Checking for Thyroid Disease

> Treatment of Thyroid Disease

> Recommendation for ThyroidCheck-ups

problems. These nodules occurwhen the cell growth within thenodule is abnormal. Nodules canoccasionally put pressure on theneck and cause trouble with swallowing, breathing or speakingif they are too large. The thyroidusually functions normally evenwhen nodules are present.

Thyroid cancers are much lesscommon than benign nodules.With treatment, the cure rate for thyroid cancer is more than 90 percent.

CHECKING FOR THYROID DISEASEChecking for thyroid disease issimilar to other kinds of medicalevaluations. The doctor considersthe patient’s medical history,examines the thyroid and mayorder a blood test or other diagnostic tests.

A standard physical examinationof the thyroid gland is done bypalpation — that is, feeling thethyroid gland. The doctor feelsfor the size and texture of thegland, and whether any masses or nodules are present.

Testing for Thyroid FunctionThere are two standard bloodtests of thyroid function: the measurement of thyroid hormone, usually T4, and themeasurement of thyrotropin

SECTION SUMMARY> Thyroid disease is common, especially

among older people and women.

> Checking for thyroid disease involvesan evaluation of the thyroid by anexperienced doctor.

> If you are concerned about exposureto iodine-131 from Hanford or experience thyroid disease symptoms,you should see your doctor for a thyroid evaluation.

A LOOK AT THYROID DISORDERSThe thyroid gland, located in thefront of the neck just below theAdam’s apple, takes iodine fromthe diet and makes thyroid hormone. Thyroid hormoneaffects a person’s physical energy,temperature, weight and mood.

Thyroid diseases generally fallinto two broad groups of disorders:abnormal function and abnormalgrowth (nodules) in the gland.These problems are common inthe general population, especiallyamong older people and women.Most thyroid problems can bedetected and treated.

Functional disorders are usuallyrelated to the gland producingtoo little thyroid hormone(hypothyroidism) or too muchthyroid hormone (hyperthyroidism).

Benign nodules in the thyroidgland are common and do notusually cause serious health

About Thyroid Disease



(TSH). TSH is a hormone secreted from the pituitary glandthat controls how much thyroid hormone the thyroid makes.

Abnormal blood tests usuallyreveal thyroid function problemsand not the presence of thyroidnodules or cancer.

Testing for NodulesIf a nodule is found during thephysical examination, a testcalled fine needle aspiration(FNA) biopsy may be done tohelp find out whether the noduleis cancerous or benign. In addition,a thyroid nuclear scan may helpthe doctor evaluate thyroid function or nodules. The scan isperformed by giving the patient aradioisotope and taking a specialpicture to see how much of theradioisotope is taken up by thethyroid gland.

A thyroid ultrasound scan is adiagnostic test that shows a pictureof the anatomy, or structure, ofthe thyroid gland. Ultrasound is

> The majority of benign nodulesdo not require treatment.Patients with benign nodulesare usually advised to have periodic follow-up examinations.

> Hypothyroidism usually requiresonly replacement of thyroidhormone by taking a singledaily tablet at a dose adjustedto produce normal thyroid hormone levels.

> Autoimmune thyroiditis is a disorder that may causehypothyroidism. It usually does not cause symptoms thatrequire treatment unlesshypothyroidism develops. Insuch cases, thyroid hormonereplacement is required.

> Treatment of hyperthyroidism may include antithyroid drugs,radioactive iodine-131 or inrare cases, thyroid surgery.

RECOMMENDATION FOR THYROID CHECK-UPSIf you have received regular healthcare and have no symptoms ofthyroid disease, you may not needto see a doctor to check for thyroid disease. However, if youare concerned about being exposedto iodine-131 from Hanford or experience thyroid disease symptoms, you should see your doctor for a thyroid examination. ■

most often used to determine if anodule is solid or cystic. Cysticnodules, containing only fluid,are usually benign.

Ultrasound is not usually performedas a routine screening test for thyroid nodules in the generalpopulation. The reason is thatsmall, nonpalpable ultrasoundabnormalities are very commonin people without evidence of thyroid disease.

TREATMENT OF THYROID DISEASEThe treatment of thyroid diseasedepends on many factors, includingthe type and severity of the thyroiddisorder and the age and overallhealth of the patient. Treatmentmust be specific to each individual.

> Thyroid cancer is initially treatedwith thyroid surgery. Manypatients also receive furthertreatment with iodine-131.Patients treated for thyroid cancer require lifelong thyroidhormone replacement.

SYMPTOMS OF ABNORMAL THYROID FUNCTION

TOO LITTLE THYROID HORMONE(HYPOTHYROIDISM)> Depression or feeling blue> Trouble concentrating > Tiredness> Dry skin and hair> Weight gain> Feeling cold all the time

TOO MUCH THYROID HORMONE(HYPERTHYROIDISM)

> Nervousness and anxiety > Weight loss > Tremor (shaking) > Fast, irregular pulse> Tiredness> Feeling hot all the time

About Thyroid Disease

Information about the HanfordThyroid Disease Study andrelated topics is availablethrough the Centers for DiseaseControl and Prevention (CDC)and other agencies in the U.S.Department of Health andHuman Services.

– Richland Library, Richland, WA– DOE Reading Room, Richland, WA

AGENCY FOR TOXIC SUBSTANCESAND DISEASE REGISTRY The Hanford Community HealthProject provides a variety of public health materials related toiodine-131 for individuals exposedas young children to releases ofiodine-131 from Hanford from 1945through 1951. The Project is sponsored by the Agency for Toxic Substances and DiseaseRegistry (ATSDR).

For more information:

Hanford Community Health Project 800-207-3996 [email protected]

or

ATSDR Information Center888-42ATSDR (888-422-8737)[email protected]

NATIONAL CANCER INSTITUTEThe National Cancer Institute has materials on thyroid cancer andscreening, and iodine-131 exposure.

For more information:

http://www.cancer.gov

or

800-4-CANCER (800-422-6237)

CENTERS FOR DISEASECONTROL AND PREVENTION

Hanford Thyroid Disease Study

> Write toHanford Thyroid Disease StudyCenters for Disease Control

and PreventionNational Center for

Environmental HealthRadiation Studies Branch1600 Clifton Road, NEMS E-39Atlanta, GA 30333

> [email protected]

> HTDS Web SiteThe HTDS Final Report and publicinformation materials are available at http://www.cdc.gov/nceh/radiation

> Public LibrariesThe HTDS Final Report can beviewed at the following librariesbeginning July 2002:

– University of Washington HealthSciences Library, Seattle, WA

– Seattle Public Library System,Seattle, WA

– King County Public LibrarySystem, Seattle, WA

– Gonzaga University Library(Foley Center Library),Spokane, WA

Information Resources


The HTDS was conducted by a team of scientists and physicians with extensive experience in epidemiologicalresearch, radiation exposureand thyroid disease.

The HTDS Research Team


Paul Garbe, D.V.M., M.P.H.Scientific Advisor, HTDS; Associate Director for Science, Division ofEnvironmental Hazards and Health Effects, National Center of EnvironmentalHealth

Dr. Garbe has worked at CDC for 20 years on issues related to the health effectsof environmental hazards. He served in CDC’s Epidemic Intelligence Service, andsince 1991, has coordinated CDC epidemiology projects which assess relationshipsbetween thyroid diseases and environmental radiation exposures.

Mike DonnellyHTDS Project ManagerMike Donnelly was CDC’s HTDS project officer through 2001 and has beeninvolved in Hanford issues since 1991. He has more than 20 years experiencewith CDC as a public health advisor working on a variety of public health issues.

THE CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC)

CDC protects people’s health and safety by preventing and controlling diseases and injuries, providing information on health issues, and promoting healthy livingthrough partnerships with local, national and international organizations.

FRED HUTCHINSON CANCER RESEARCH CENTER (FHCRC)

The Fred Hutchinson Cancer Research Center is an independent, non-profit research institution, which conducts scientific investigations of the causes and treatments of cancer and other potentially fatal diseases.

Scott Davis, Ph.D.Principal Investigator, HTDS;Program in Epidemiology, FHCRC;Professor and Chairman,Department of Epidemiology, Schoolof Public Health and CommunityMedicine, University of Washington

Dr. Davis’ research is focused oninvestigations of the health effects of radiation exposure in human populations, and includes studies of survivors of the atomic bombingsin Japan and people exposed to radiation from Chernobyl.

Kenneth J. Kopecky, Ph.D.Co-investigator, HTDS; Program inBiostatistics, FHCRC; AffiliateProfessor, Department ofBiostatistics, School of Public Healthand Community Medicine, Universityof Washington

Dr. Kopecky is a biostatistician withextensive experience in research intothe health effects of radiation,including studies of Japanese atomicbomb survivors and of peopleexposed to fallout from Chernobyl.Dr. Kopecky also served as a memberof the HEDR Technical Steering Panel.

Thomas Hamilton, M.D., Ph.D.Co-investigator, HTDS; ClinicalAssociate Professor, Division ofEndocrinology and Metabolism,University of Washington

Dr. Hamilton is a practicing endocrinologist and an expert in thediagnosis and management of thyroid disease. He has conductedresearch in the Marshall Islands,where he evaluated the risk of thyroid disease among peopleexposed to fallout from nuclearweapons testing.

June 21, 2002