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Dosimetry for Epidemiological Studies: Learning from the Past, Looking to theFutureAuthor(s): Steven L. Simon, André Bouville, Ruth Kleinerman, and Elaine RonSource: Radiation Research, 166(1):313-318. 2006.Published By: Radiation Research SocietyDOI: http://dx.doi.org/10.1667/RR3536.1URL: http://www.bioone.org/doi/full/10.1667/RR3536.1

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RADIATION RESEARCH 166, 313–318 (2006)0033-7587/06 $15.00q 2006 by Radiation Research Society.All rights of reproduction in any form reserved.

SUMMARY

Dosimetry for Epidemiological Studies: Learning from the Past,Looking to the Future

Steven L. Simon,1 Andre Bouville, Ruth Kleinerman and Elaine Ron

Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland

INTRODUCTION

Assembling the suite of manuscripts for this special issueof Radiation Research has afforded us a unique opportunityto evaluate the various methods of dosimetry used in sup-port of epidemiological studies as well as the strengths andweaknesses of different dosimetric approaches. Of equalimportance is having the opportunity to highlight elementsof dosimetry that are especially important to conductingconvincing epidemiological studies.

In general, analytical epidemiological studies of radiationeffects attempt to combine information on disease (e.g. can-cer) occurrence with estimates of radiation dose to individ-uals such that the relationship between the increase in dis-ease incidence compared to the background rate as a func-tion of the true dose can be described. With regard to thelanguage and science of dosimetry, there are a number ofterms, assumptions and implied meanings that are often notclear to the variety of scientists involved in radiation epi-demiology studies. This issue should help inform these re-searchers.

In this special issue of Radiation Research devoted tothe dosimetric aspects of radiation epidemiology, we at-tempted to clarify what is meant by ‘‘dosimetry for epi-demiological studies’’, what is required to ensure that thefindings of dosimetry-based epidemiological studies are ascredible and generalizable as possible, and to give practicalexamples from current or recent studies. While this collec-tion of papers certainly does not cover all of the aspects ofdosimetry in epidemiology, it is meant to describe wherewe have been in terms of applying dosimetry for epide-miological purposes and where we are going to further ad-vance the discipline.

SUMMARY OF STUDIES PRESENTED

Readers of this issue of Radiation Research are probablyalready acquainted with a wide range of dosimetric meth-

1 Address for correspondence: Division of Cancer Epidemiology andGenetics, National Cancer Institute, 6120 Executive Blvd., Room 7100,Bethesda, MD 20892; e-mail: ssimon@mail.nih.gov.

ods. Here we briefly summarize the principal identifyingcomponents of the ten applications of dosimetric methodsdescribed in the individual papers. Table 1 contains a listingof the papers and a greatly abbreviated description of themethods employed and the available input data.

Medical Dosimetry

Methods for estimation of organ doses after the admin-istration of radioisotopes as described by Brill et al. (1) arewell developed and have depended for several decades onthe formulations of the Medical Internal Radiation Dose(MIRD) Committee [see ref. (2) for a primer on those meth-ods]. The basis for dose estimation by these methods is ametabolic model coupled with a measured amount of ad-ministered radioactive material. Unlike occupational andenvironmental dose estimations, the great advantage inthese situations is that the amount of activity administeredis usually known. Though the ability to accurately measurethe administered activity does not pose any great technicalchallenges, differences between individuals in their metab-olism (kinetics) and anatomy (size and exact location oforgans) lead to uncertainties in the absorbed dose for anyidentified person. Thus, even when activity intake is known,doses cannot be estimated with absolute precision. One ofthe limitations in estimating individual dose arises from theuse of standardized or mathematical phantoms that are as-sumed to representing the individual receiving the treatmentdose.

Even iodine-131, one of the most studied nuclides forwhich kinetics in the human body has been described sincethe early 1950s (3), has dose uncertainties, partly becauseof human variation, but also due to secular changes in thedietary component of stable iodine. Changes in iodine in-take have occurred at the local, national and internationallevels, and these can affect the amount of radioiodine ab-sorbed by each individual thyroid gland.

Estimation of doses from medical procedures, includingtreatments and diagnostic procedures, as described by Sto-vall et al. (4), involves traditional treatment planning tech-niques, archival data collection, and contemporary mea-

314 SUMMARY

TABLE 1Summary of Physical or Calculation-Based Dosimetric Methods Described in Publications of this Issue

Exposurecategory/authors

Exposure setting, population,and location

Organs/tissues fordose estimation

Mode of exposure(internal, external)

Primary methods andinput data

Medical

Brill et al. (1) Clinical: patients (emphasis onU.S.)

Thyroid primarily Internal (131I) Metabolic model using measuredadministered radionuclides

Stovall et al. (4) Clinical: patients (emphasis onU.S.)

All organs 1 redbone marrow(RBM)

External and internal Measurements and calculationsbased on records from admin-istered treatments and/or diag-nostic tests

Occupational

Bouville et al. (6) Reactor: clean-up workers(Ukraine)

RBM primarily, in-ternal (minor)

External primarily,internal (minor)

Film badge measurements (indi-vidual or group), exposurerate, questionnaire responses

Gilbert et al. (7) Various reactors: workers (U.S.,Europe)

Whole-body External primarily Film badge and other dosimetermeasurements

Simon et al. (8) Clinical: radiologic technolo-gists (U.S.)

All organs, emphasison breast, skin,RBM

External Film badge measurements, ques-tionnaire responses, historicalliterature

Environmental

Beck et al. (9) Public: population living down-wind of nuclear test sites(U.S., Kazakhstan, MarshallIslands)

Thyroid primarily,also RBM

External and internal Measurements of exposure ratecoupled with environmentaltransfer models, questionnaireresponses

Cullings et al. (12) Public: A-bomb survivors (Hi-roshima and Nagasaki, Japan)

Whole-body External Reconstruction of detonationconditions (source term), geo-graphic location, house con-struction

Degteva et al. (11) Public: people living near con-taminated river (Chelyabinsk,Russia)

All organs 1 RBM External and internal Release data and environmentaltransfer model

Likhtarev et al. (10) Public: people living nearChernobyl reactor (Ukraine,Belarus)

Thyroid External and internal Measurements of 131I in thyroidplus model

Puskin et al. (15) Homes and mines (internation-al)

Lung Internal by inhala-tion

Physics based model to convertfrom exposure to dose, depen-dent on environmental mea-surements of 222Rn

surements, sometimes of aged radiation-generating ma-chines. The goal of those various techniques is, in general,to characterize the dose to organs/tissues outside of treat-ment areas, primarily due to within-body scatter of radia-tion and leakage from the treatment machine. Various typesof phantoms are used for dose measurements and dose es-timation, including mathematical, anthropometric and waterphantoms. Therapy doses are particularly amenable to re-construction because, much like when radiopharmaceuticalsare administered, the irradiation conditions were controlledand the dose to the treatment site was recorded, althoughdetailed radiation records are not always accessible (5).Since patients comprise the largest population group ex-posed to doses ranging from very low to extremely high,dosimetry and risk associated with those exposures willcontinue to be a major focus of study.

Occupational Dosimetry

Occupational exposure includes a wide range of job de-scriptions in the medical, weapons construction, and nucle-

ar power industries, and dosimetric methods reflect thosevarious conditions.

Dose estimation for the Chernobyl clean-up workers asdescribed by Bouville et al. (6) took advantage of theunique exposure conditions that could be assumed as rela-tively homogeneous over the body. In that study, doseswere estimated by one of four different methods, dependingon the individual study subject and the data available forthat subject: individual film badge measurements, a groupfilm badge measurement, group assessment based on thedose rate at the work assignment location, or individualreconstruction based on time spent at different locationstaking into account the respective dose rates at those lo-cations. The doses for the Estonian workers were also es-timated by biodosimetric methods, but neither GPA norFISH was able to detect any biological changes comparedto control subjects. The failure of biodosimetry to supportestimated doses was likely related to the overestimation ofrecorded doses for those exposed workers as well as the

315SUMMARY

limits of detection. Nuclear workers, in the context of thepaper by Gilbert et al. (7), include personnel involved inweapons production, nuclear power generation, and relatedresearch activities in the U.S., UK and Canada. Studies ofthose workers encountered some of the same problems asthe study of radiological technologists (8) in that workerswere monitored over time (from the 1940s through recentyears) when the calibration methods for personnel moni-toring badges were evolving. In addition to different typesof calibrations, dosimeters used early in the profession didnot respond accurately to all radiation energies or uniformlywith direction. Gilbert and colleagues (7) primarily char-acterize the bias and uncertainties related to the dosimetryand describe some ways to account for the uncertainty sothat dose–response analyses are not unnecessarily limited.

Radiation technologists began to be needed in the earlypart of the 20th century during the developmental periodof diagnostic and therapeutic radiology. Throughout the20th century, the responsibilities of these medical profes-sionals changed from a mixture of all tasks in a radiologydepartment to becoming more specialized in specific pro-cedures. Over that same period, understanding and recog-nition of radiation risks, development of ALARA (as lowas reasonably achievable) principles, and improved tech-nologies served to reduce the doses per individual proce-dure to the patient and the technologist. At the same time,the workload of technologists has increased due to thewidespread use of radiological procedures in medicine. Es-timation of doses to medical workers rarely goes beyond areported value of the personal dose equivalent, a regulatoryquantity derived directly from a calibrated film badge. Inthe dosimetric methods described by Simon et al. (8), as-sumptions based on literature review were used to describethe nature and quality of radiation fields to which individualtechnologists were exposed, thus allowing for estimation oforgan doses and their uncertainties. For reconstruction ofdoses to radiation technologists, responses to detailed ques-tionnaires were used as well as large national databases offilm badge readings that included data on members of thecohort.

Environmental Dosimetry

The estimation of doses from exposure to radioactivefallout from nuclear weapons tests and from releases ofradionuclides to the environment occupies a special nichein dosimetric applications because it includes a wide varietyof disciplines including physics, environmental science,anatomy and physiology, and even human behavior.

There are several unique qualities of fallout dosimetry.First was the large number of source terms; between 1945and 1980, over 500 weapons tests were conducted in theatmosphere at a number of locations around the world. An-other unique quality of fallout studies is that individual do-simetry data, except occasionally for military personnel, arenever available. Even for military personnel, monitoring

data would apply only to external exposures, and falloutdose estimation usually includes internal exposure as well.Hence dose estimation for fallout exposure almost alwaysrequires the use of complex models with numerous param-eters. To characterize those parameters, only very limitedamounts of real data are typically available, resulting inhigh uncertainty, particularly for internal dose. Second, thelong interval since the exposures occurred has resulted inloss of some original data, although the sparse historicalmeasurement data available are generally sufficient to es-timate external exposure doses reasonably well. Recon-struction of internal doses from ingestion and inhalation ofradionuclides is significantly more complex and is almostalways more uncertain than for external dose estimation.Internal dose estimates are typically based on estimates ofthe ground deposition per unit area of specific radionuclidesand subsequent transport of radionuclides through the foodchain whereas, for external dose estimation, reconstructionis reasonably straightforward and relevant data in the formof exposure rates are often available.

In the description of fallout dosimetry methods by Becket al. (9), the number of locations for which dose estimateshas been made is impressive and covers most of the con-tinents as well as some island locations. Moreover, becauseof the large numbers of measurements of fallout radionu-clides in the environment and in humans, fallout studieshave been some of the most innovative in terms of devel-oping individual dose and uncertainty estimates.

Despite nearly 50 years of study, technical challenges infallout dosimetry still remain. These include needed im-provements in modeling of radionuclide fractionation withchanges in distance and particle size, consistency of modelsbetween U.S., Russian and other investigators, and the con-tinuing need to archive historical data that are at risk ofpermanent loss.

Individual thyroid doses from 131I, as well as uncertain-ties, have been estimated for two cohort studies of approx-imately 13,000 Ukrainians and 12,000 Belarussians ex-posed to fallout from the Chernobyl accident. The studydescribed by Likhtarev et al. (10) is unique in that few, ifany, other studies of environmental exposure have beenable to rely on measurements of activity in the thyroid ofeach study subject. The assessment of the individual thyroiddoses from intakes of 131I is based on the results of mea-surements of external g radiation by means of radiationdetectors placed against the neck. Within a few weeks afterthe Chernobyl accident, approximately 200,000 of thosemeasurements were made in Belarus and 150,000 inUkraine. In common with many other studies of exposureof the thyroid gland, the parameter that accounts for a largepart of the uncertainty is the thyroid mass. However, unlikeother studies, there was uncertainty in the determination ofthe 131I content in the thyroid due to the direct g-ray mea-surements and their interpretation.

Similar to Chernobyl, where doses were estimated toworkers (6) and the public (10) living downwind of the

316 SUMMARY

damaged reactor, reconstructed doses to populations livingdownstream from the Mayak reactor have also been esti-mated. The Techa River dosimetry system, as described byDegteva et al. (11), estimates dose to the population livingalong the river that received discharges from the Mayakfacility. The Techa River dosimetry system was developedso that health risks of low to moderate dose rates could beevaluated in several exposed cohorts. In that dosimetry sys-tem, unique data on 90Sr in teeth (assayed by surface b-particle activity), whole-body measurements, and autopsymeasurements have been used for validation of estimateddoses.

In the paper by Cullings et al. (12), we get an appreci-ation for the evolution of the dosimetry for A-bomb sur-vivors from the first implementation, T57D, to the presentsystem, DS02. More importantly, this paper clarifies thatwhat was previously thought to be a substantial ‘‘neutrondiscrepancy’’ was actually not a major deficiency. The ex-ercise of applying the latest nuclear weapons codes andother computationally intensive calculations, made feasibleby continued improvements in computer speed, served toimprove the estimates of explosive yield and height of burstand to increase the spatial and temporal resolution of theDS02 calculations over previous versions.

A-bomb survivor dosimetry is unique in many ways.First, there was a single acute exposure, a rare event exceptfor some unintended criticality events, none of which arediscussed in the papers here. The predominant difficulty inA-bomb survivor dosimetry has been to accurately describethe source term and the energy fluence and air kerma at thelocation of each survivor. No other dosimetry system usedfor an epidemiological study has had such stringent require-ments. To arrive at the most recent dose estimates, hundredsof person-years of effort have been expended over a periodof about 50 years. Most remaining issues requiring furtherstudy appear to be related to risk analyses, e.g., adjustmentsfor dosimetry error, although the Nagasaki factory workersstill appear to indicate a positive bias in their estimateddoses.

Radon gas is believed to be a primary source of radiationrisk to the public and has been the subject of informationcampaigns (see http://www.epa.gov/radon/pubs/), reports ofwell-respected committees (13, 14), and countless studies,conference presentations, and letters to journal editors de-bating the degree of risk. It may come as a surprise to somereaders that radon risk continues to be so hotly debated andthat risk estimation has been based for decades on exposure(a measure of the a-particle energy released in air, inte-grated over time) rather than on absorbed dose delivered totissue. Puskin et al. (15) discuss the labyrinth of issuesrelated to lung dosimetry from radon progeny. Though thedecay of radon gas through a series of radioactive by-prod-ucts has been thoroughly understood for decades, the esti-mation of tissue dose has been one of the last issues re-solved, partly because the short range of a-particle radia-tion complicates calculations, but also because the distri-

bution of the radioactive progeny in the respiratory tract isfar from uniform. In addition, it is widely known that thequality of air in mines, where most risk studies have beenconducted, and in homes, where greater numbers of peopleare exposed, differs considerably. These differences inevi-tably have led to uncertainty in estimated doses from radon.

Looking to the Future

Here we discuss some specific challenges that becameapparent during the review of the dosimetry applicationspresented in this issue. Meeting these challenges will serveto improve future epidemiological analyses by providingmore precise organ dose estimates for individuals whileeliminating bias and reducing dose misclassification.

Uncertainty

Understanding the uncertainty of models and estimateddoses (16), minimizing uncertainly where possible and cor-recting dose–response relationships (17) for distortion ofthe dose response (i.e. the risk) in the presence of ‘‘clas-sical’’ error will likely remain a challenge in all low-doseradiation studies. Whereas dosimetry papers typically rep-resent a challenge for epidemiologists and biostatisticiansto understand, physicists and dosimetrists meet similar dif-ficulties in assimilating the concepts explained by Schaefferand Gilbert (18) in their discussion on statistical implica-tions of uncertainty. Readers will note the concerted at-tempt by those authors to provide a non-technical discus-sion, though the complexity of the issues can quickly beappreciated by trying to determine the degree to which anyset of estimated doses contains classical or Berkson errorsor combinations of the two. The additional problem of thelurking ‘‘shared errors’’ that result from complex estimationschemes and models, commonly used in dose reconstruc-tion for environmental exposure scenarios, is discussed.

The possibility that either simpler or more complex ex-posure assessment models could be developed as a meansto reduce dosimetric uncertainty has been considered. How-ever, extremely complex models, while possibly justified asa means to understand physical processes, will not neces-sarily reduce uncertainty because of the additional param-eters involved (19). Reviews of the reliability of the param-eter values used in biokinetic and dosimetric models havebeen helpful in identifying the areas where improvementscan be made (20–22).

Independent Verification of Estimated Doses

Within this issue of Radiation Research, there are at leastten methods described for estimating doses under differentexposure scenarios or where different types of data areavailable. Radiation doses received by tissues of interestare not directly observable. Nor are data usually availableto estimate tissue doses precisely except, perhaps, wheredosimeters are placed in situ before an exposure takesplace. Retrospective dose estimation, used extensively in

317SUMMARY

radiation epidemiology, has the distinct disadvantage thatdose to the tissue of interest was almost never measured.With the exception of medical exposures, models are al-most always employed to deduce the absorbed energy andthe toolbox of techniques available for retrospective esti-mation typically have common weaknesses related to mod-els and reliability of input data.

As a useful addition to the dosimetric toolbox, we haverecently added the capability to make measurements of cer-tain biological changes induced by radiation, i.e. biodosi-metric measurements (23, 24). These measurements in-clude, for example, fluorescence in situ hybridization fortranslocation analysis (using peripheral blood lymphocytes)and electron paramagnetic resonance (using tooth enamel).These techniques potentially allow for testing the reliabilityof estimated doses. There are limitations of the techniquesthemselves, including temporal stability, minimum detec-tion limits, and sample collection. Verification of estimateddoses, to the degree possible, will continue to be a neces-sary part of determining risks per unit dose whenever in-dependent reliability is demanded.

The immediate challenge for biodosimetry is to developalternative technologies that are less expensive and that canbe implemented more quickly, are less biologically inva-sive, and have lower detection limits, while maintaining thesignal many years after the exposure, as is currently pos-sible for the FISH and EPR techniques. One current attemptis to develop in vivo EPR measurement methods that canbe carried out without having to obtain extracted teeth. In-novations of this type would be useful, particularly to anymoderate-sized epidemiological study that depended on ret-rospective dosimetry as well as being a useful tool afterradiological terrorism events.

Other New Tools

The toolbox for estimating doses has long included var-ious types of models. The set of tools that are available fordose estimation continues to expand, but the most basic setincludes historical archived data, contemporary physicalmeasurements to supplement historical data, models oftransport phenomena, biokinetics, behaviors (e.g. food in-gestion rates), and numerical simulation.

Due to advances in computer hardware as well as soft-ware implementation of complex algorithms, the applica-tion of simulation has expanded to cover nearly all aspectsof dosimetry including environmental transport, energy andparticle transport, and models of complex emission sourcesand complex-shaped receptors, e.g. the human body. Re-cently, voxel-based phantoms have seen a surge of devel-opment that will serve to improve the realism of dosimetricestimates. Voxels (meaning volume elements) are the three-dimensional equivalents of image pixels. Unlike mathe-matical phantoms that are equation-based descriptions ofthe geometry of the human body, voxel phantoms are basedon computed tomographic or magnetic resonance images

obtained from high-resolution scans of single individuals.Voxel phantoms consist of a huge number of volume ele-ments (voxels) and are at the moment the most precise rep-resentation of the human anatomy (25). Studies of externaldoses to individuals, e.g. the study of radiation technolo-gists (8), could take advantage of a new generation of phan-toms and further individualize doses based on variations inindividual morphology.

FINAL REMARKS

This review of the application of dosimetry in epidemi-ology has shown that for the most part, estimated doses canbe usefully grouped by the exposure categories of medical,occupational and environmental. Moreover, those catego-ries are generally indicative of the degree of uncertaintythat should be expected in the estimated doses. Reconstruc-tion of medically related doses will always have the ad-vantage that irradiations were conducted under controlledconditions and that individual records are usually availablefor radiotherapy patients. This leads to the advantage oflower uncertainty of estimated doses and applies to bothinternal and external exposures. Dose received in an oc-cupational setting would generally be less controlled thanin medical settings, but the occupational environment oftenhas monitoring data available, on either a group or individ-ual level. Environmental exposures will almost always bethe most uncertain and will require more complex models,particularly for estimating internal exposures. Moreover, thedata available to reconstruct environmental exposures willgenerally be sparse compared to the other settings and willrequire more extensive use of interpolation and estimationstrategies. However, past environmental exposure scenarioshave an inherent importance because they represent thetype of exposure that could affect the public in the futureif accidents or radiological terrorism events occur.

There are several other conclusions to be drawn fromthis review. First, we believe that organ absorbed dose,reported in grays (Gy), and associated with information onthe radiation quality, is the most relevant metric for epi-demiological studies. Variations of dose involving the useof weighting factors, such as the effective dose, were de-vised for radiation protection purposes and not for scientificanalyses. Those metrics of dose are confounded by regu-latory weighting factors that are subject to change withtime. Therefore, equivalent dose or effective dose does nothave a place in epidemiology to elucidate radiation risk,where the most accurate possible estimates of absorbeddoses are desired.

The movement within the epidemiology community toinvolve physicists/dosimetrists in radiation health effectsstudies, from the earliest study planning stages through thefinal analysis, represents a paradigm shift over past decades.We believe that this collaboration offers multiple benefitsto improving epidemiology studies and risk estimation. Inparticular, it ensures that doses used to derive risk estimates

318 SUMMARY

are appropriate for the task and were estimated with a clearunderstanding as to their purpose.

Understanding and characterizing the uncertainty of es-timated doses cannot be ignored even though, on occasion,extensive uncertainty analysis has not changed epidemio-logical conclusions. For reasons of credibility, and to allowfor innovations in correcting for distortion of the dose–re-sponse function, uncertainty estimation remains a priority.

Improvements in previously used dose estimation tools,e.g. phantoms of the human body and computer simulationmethods, will benefit dosimetric estimation and related ep-idemiological studies. Continued development and im-provement of such tools should be encouraged. The devel-opment of new dosimetric tools, e.g. inexpensive biodosi-metry methods with low detection limits, would enable ver-ification or modification of model-based dose estimates.

The National Cancer Institute, having taken note of therelative void in the literature on how to apply dosimetry toimprove epidemiological studies, undertook preparation ofthis special issue to share new knowledge and to encouragefurther development of these concepts. We anticipate thatthe measure of our success will be seen over the next 20years when studies now only being contemplated are com-pleted and bear some fruit of these developmental efforts.

REFERENCES

1. A. B. Brill, M. Stabin, A. Bouville and E. Ron, Normal organ radi-ation dosimetry and associated uncertainties in nuclear medicine,with emphasis on 131I. Radiat. Res. 166, 128–140 (2006).

2. R. Loevinger, T. F. Budinger and E. E. Watson, MIRD Primer forAbsorbed Dose Calculations, revised ed. The Society of NuclearMedicine, New York, 1991.

3. D. S. Riggs, Iodine metabolism in man. Pharmacol. Rev. 4, 1–284(1952).

4. M. Stovall, R. Weathers, C. Kasper, S. A. Smith, R. Kleinerman andE. Ron, Absorbed dose to anatomical sites outside radiation therapybeams. Radiat. Res. 166, 141–157 (2006).

5. D. W. Schafer, J. H. Lubin, E. Ron, M. Stovall and R. J. Carroll,Thyroid cancer following scalp irradiation: A reanalysis accountingfor uncertainty in dosimetry. Biometrics 57, 689–697 (2001).

6. A. Bouville, V. V. Chumak, P. Inskip, V. Kryuchkov and N. Lucky-anov, Chornobyl accident: Estimation of radiation doses received bythe clean-up workers. Radiat. Res. 166, 158–167 (2006).

7. E. S. Gilbert, I. Thierry-Chef, E. Cardis, J. J. Fix and M. Marshall,External dose estimation for nuclear worker studies. Radiat. Res. 166,168–173 (2006).

8. S. L. Simon, R. M. Weinstock, M. M. Doody, J. Neton, T. Wenzl, P.Stewart, A. K. Mohan, R. C. Yoder, M. Hauptmann and M. Linet,Estimating historical radiation doses to a cohort of U.S. radiologictechnologists. Radiat. Res. 166, 174–192 (2006).

9. H. L. Beck, L. R. Anspaugh, A. Bouville and S. L. Simon, Reviewof methods of dose estimation for epidemiological studies of theradiological impact of NTS and global fallout. Radiat. Res. 166, 209–218 (2006).

10. I. Likhtarev, A. Bouville, N. Luckyanov and P. Voilleque, Estimationof individual thyroid doses in Ukraine resulting from the Chernobylaccident. Radiat. Res. 166, 271–286 (2006).

11. M. O. Degteva, M. I. Vorobiova, E. I. Tolstykh, V. P. Kozheurov,N. B. Shagina, E. A. Shishkina, L. R. Anspaugh, B. A. Napier, N.G. Vougrov and V. A. Taranenko, Development of an improved dosereconstruction system for the general population affected by the op-eration of the Mayak production association. Radiat. Res. 166, 255–270 (2006).

12. H. M. Cullings, S. Fujita, S. Funamoto, E. J. Grant, G. D. Kerr andD. L. Preston, Dose estimation for the atomic bomb survivor studies:Evolution and present status. Radiat. Res. 166, 219–254 (2006).

13. National Research Council, Committee on the Biological Effects ofIonizing Radiation, Health Risks of Radon and Other Internally De-posited Alpha-Emitters (BEIR IV). National Academy Press, Wash-ington, DC, 1988.

14. National Research Council, Committee on the Biological Effects ofIonizing Radiation, Health Effects of Exposure to Radon (BEIR VI).National Academy Press, Washington, DC, 1999.

15. J. S. Puskin, A. C. James and P. Duport, Radon exposure assessmentand dosimetry applied to epidemiology and risk estimation. Radiat.Res. 166, 193–208 (2006).

16. NCRP, A Guide for Uncertainty Analysis in Dose and Risk Assess-ments Related to Environmental Contamination. Commentary No.14, National Council on Radiation Protection and Measurements, Be-thesda, MD, 1996.

17. E. Ron and F. O. Hoffman, Eds., Uncertainties in Radiation Dosim-etry and Their Impact on Dose–Response Analysis. NIH PublicationNo. 99-4541, National Cancer Institute, National Institutes of Health,Bethesda, MD, 1999.

18. D. W. Schafer and E. S. Gilbert, Statistical ramifications of doseuncertainty in radiation dose–response analyses. Radiat. Res. 166,303–312 (2006).

19. M. G. Morgan and M. Henrion, Uncertainty, A Guide to DealingWith Uncertainty in Quantitative Risk and Policy Management. Cam-bridge University Press, Cambridge, 1990.

20. J. D. Harrison, R. W. Leggett, D. Nosske, F. Paquet, A. W. Phipps,D. M. Taylor and H. Metivier, Reliability of the ICRP’s dose coef-ficients for members of the public, II. Uncertainties in the absorptionof ingestion radionuclides and the effect on dose estimates. Radiat.Prot. Dosim. 95, 295–308 (2001).

21. NCRP, Evaluating the Reliability of Biokinetic and Dosimetric Mod-els and Parameters Used to Assess Individual Doses for Risk As-sessment Purposes. Commentary No. 15, National Council on Ra-diation Protection and Measurements, Bethesda, MD, 1998.

22. R. W. Leggett, Reliability of the ICRP’s dose coefficients for mem-bers of the public. III. Plutonium as a case study of uncertainties inthe systemic biokinetics of radionuclides. Radiat. Prot. Dosim. 106,103–120 (2003).

23. T. Sugahara, L. Zhang, J. Wang, T. Aoyama and J. Zhang, Eds. Ret-rospective dosimetry, physical and biological aspects. Radiat. Prot.Dosim. 77, 1–138 (1998).

24. R. A. Kleinerman, A. A. Romanyukha, D. A. Schauer and J. D.Tucker, Retrospective assessment of radiation exposure using biolog-ical dosimetry: Chromosome painting, electron paramagnetic reso-nance and the glycophorin A mutation assay. Radiat. Res. 166, 287–302 (2006).

25. U. A. Fill, M. Zankl, N. Petoussi-Hens, M. Siebert and D. Regulla,Adult female voxel models of different stature and photon conversioncoefficients for radiation protection. Health Phys. 86, 253–272(2004).