Health Physics Archeology

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Health Physics Archeology

• An Overview of
• Dose Reconstruction

Radiation Studies Branch National Center for
Environmental Health Centers for Disease Control
and Prevention
August, 2004
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Outline

• Overview of dose reconstruction principles
• Examples of CDC dose reconstruction projects
• Lessons learned from dose reconstruction projects

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Principles of Dose Reconstruction
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Dose Reconstruction
Dose reconstruction is a comprehensive analysis
of the exposure received by individuals in the
vicinity of facilities that release contaminants
to the environment (i.e., real doses to real
people).
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Health Physics Archeology
Dose Reconstruction
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Purpose of Dose Reconstruction

• Provide a comprehensive history of site
  operations, including releases of radioactive
  material.
• Provide dose distribution estimates used in
  epidemiological studies.
• Provide an independent, comprehensive evaluation
  of risk.
• Provide a baseline for analyzing effects of other
  activities (e.g., clean-up).

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Major Goals of Dose Reconstruction

• Assure the soundness of the science
• Gain public acceptance

No matter how good the science, if the public
does not accept the results, we fail.
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Basic Assumptions

• No standard methodological guide book exists.
• Each site has unique attributes.
• Lessons can be learned from each study.
• Common approaches can be developed.

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Dose Reconstruction Process

• 1. Retrieval and assessment of data
• 2. Development of initial source term and pathway
  analysis
• 3. Calculation of screening doses and exposures
• 4. Development of methods for assessing
  environmental doses
• 5. Calculation of environmental exposures, doses,
  and risks

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Stages of the Process

• Stages of the process may overlap in time.
• Stages may be performed iteratively.
• All stages may not be necessary at all sites.
• Total process at each site may take 47 years or
  more to complete.

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Preliminary Analysis

• Assess the amount of public interest.
• Conduct a literature review of all research in a
  related area.
• Gather all relevant data and records for the
  particular site.
• Conduct personal interviews.

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Dose Assessment

• Three Levels
• Preliminary (Scoping Study)
• Comprehensive Analysis
• Individual Dose Assessment

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New Dose Assessment Paradigm
If risk health effect, conservative dose est
imates of dose will be nonconservative for
epidemiology
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Preliminary Dose Assessment

• Scoping Study A preliminary analysis used to
  determine whether a comprehensive dose
  reconstruction study is appropriate as the basis
  for a continued comprehensive epidemiological
  study

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Variables in a Scoping Study

• Conditions of the Release
• Chemical and physical form
• Time dependence
• Conditions of the Environment
• Geographical
• Agricultural
• Meteorological

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Variables in a Scoping Study (continued)

• Conditions of the Population
• Size
• Diversity
• Structure
• Human interactions

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Variables in a Scoping Study (continued)

• Statistical Requirements
• Availability and quality of records
• Doses that can be estimated
• Large population size

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Analysis of Scoping Study Results
Based on the outcome of the scoping study, the
project may come to halt or proceed to a full
dose reconstruction.
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Comprehensive Dose Assessment
Estimation of

• the source term amount of radionuclides or
  chemicals released from a site to the environment
  during a specific period)
• both internal and external sources of radiation
  encountered by human beings

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Comprehensive Analysis

• Ways to determine and estimate the source term
• Engineering estimates
• Historic reports of measured releases
• Reconstruction
• Redundant analyses are desirable.

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Individual Dose Assessment

• Variables that may affect individual risk must be
  recorded, such as gender, age, size, lifestyle,
  and diet.
• Children are often the most affected population.

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Gathering Data Criteria

• Measured (quantitative)
• Described in understandable units
• Raw data required (not summaries, reports, or
  interpretations)
• Withstand scientific scrutiny
• Unbiased
• Recorded by specialists or experienced staff

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Gathering Data Source Preferences

• Interviews of reliable witnesses
• Data sheets (e.g., sample mass, activity, or
  concentration measurement records)
• Logbooks
• Incident reports
• Production reports
• Safety organizations

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Data Collection and Analysis

• Data could be missing because of
• Loss
• Destruction
• Considered obsolete
• Concern about security
• Models must be developed to extrapolate missing
  data.

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Other Data Complications

• Data may be recorded from releases that are
• Episodic lasting 10 days
• Chronic recurring over a period of time
• Accidental resulting from a single unexpected
  incident

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Uncertainty Analysis

• Quantification of the extent of uncertainty in
  the model from all conceivable sources.
• Involves propagation of uncertainty in the input
  parameters and the methodology.
• Often expressed as a confidence interval.

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Sensitivity Analysis

• Evaluation of the extent to which changes in
  values of independent variables (or model
  parameters) of an equation (or mathematical
  model) bring about changes in the results.
• Allows identification of the parameters that
  dominate the overall uncertainty in the model.

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Dose Reconstruction and Epidemiology

• After completion of dose reconstruction, the
  information can be used as input in an
  epidemiological study.

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Epidemiology
The study of disease in human populations
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Objectives of an Epidemiological Study
Questions used to determine objectives

• What is the most likely radiation exposure in the
  community?
• What health effects have been reported from
  similar exposures?
• What concerns are expressed by the community?

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Epidemiological Studies

• Case-Control Study
• Compares two groups
• - one group with the health effect to
• - one group without the health effect.
• Differences between the two groups that may have
  caused the health effect are then determined.

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Epidemiological Studies (continued)

• Prospective Study
• Follows two groups through time
• - exposed group
• - not exposed group.
• Compares disease rates between the two groups.

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Epidemiological Studies (continued)

• Cohort Study
• Exposed group is studied.
• Exposed group's disease rates are compared to
  expected rates.

Many radiation-related epidemiological studies
are cohort studies.
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Type of Cohort Study Dose Response
Disease
Dose
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Strong Dose Response
Disease
Dose
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Weak Dose Response
Disease
Dose
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No Dose Response
Disease
Dose
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Feasibility Analysis

• In order to determine the feasibility of an
  epidemiological study, the statistical power of
  the study must be high enough to identify an
  increased risk for health effects if one exists.

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Statistical Power
Probability that the study can distinguish
between a true exposure-to-disease relation and a
coincidence
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Statistical Power
The variables for statistical power are

• Size of population
• Amount of exposure
• Expected strength of association between exposure
  and disease
• Number of cases of disease under investigation

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Overview of CDC Dose Reconstruction Projects
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CDCs Dose Reconstruction Projects

• 1990 - Memorandum of Understanding (MOU) was
  signed between Departments of Energy (DOE) and
  Health and Human Services (HHS). Renewed in 1995
  and 2000.
• MOU transferred energy-related epidemiological
  research program from DOE to HHS. CDC designated
  as lead agency for HHS.

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CDCs Dose Reconstruction Projects

• National Center for Environmental Health (NCEH)
  coordinates program and conducts environmental
  health studies.
• National Institute of Occupational Safety and
  Health (NIOSH) conducts worker health studies.
• The Agency for Toxic Substances and Disease
  Registry (ATSDR) conducts work related to Super
  Fund sites.

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Dose Reconstruction Activities
Hanford
Idaho National Engineering
Environmental Laboratory
Ashtabula
Lawrence
Mound
Livermore
Nevada
Rocky Flats
Fernald
Bendix
Portsmouth
Test Site
Paducah
Oak Ridge
Los Alamos
Pantex
Savannah River Site
Sandia
Republic of the
Marshall Islands
Pinellas
Current Activities Technical Support No Current
Involvement Activities Complete
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Fernald, Ohio

• 19511988 Site produced uranium feed materials.
• 1990 CDC began dose reconstruction project.
• 1998 CDC released final reports on the dose
  reconstruction issued (radon and uranium primary
  radionuclides).
• 19981999 CDC performed a risk analysis for lung
  cancer.
• June 1999 CDC presented a screening analysis for
  other cancers.
• Currently No additional studies planned.

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Hanford, Washington

• 19441990 Site produced plutonium.
• 1987 CDC began epidemiological project.
• 1994 CDC released primary results of Hanford
  Environmental Dose Reconstruction (HEDR).
• 19982000 Washington, Oregon, Idaho provided
  individual I-131 dose estimates for exposed
  people using HEDR models.
• 2002 Hanford Thyroid Disease Study completed.

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Hanford, Washington (continued)

• Currently
• Follow-up of Columbia River dose reconstruction
• Development of a computer program to estimate
  doses from radioactive particles and short-lived
  radionuclides
• Development of Web-based individual dose
  assessment tool

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Idaho National Engineering and Environmental
Laboratory (INEEL)

• 1949 Site began operation as a National Reactor
  Testing Station.
• 1992 CDC began dose reconstruction project.
• 1995 CDC issued 2 reports on Phase I (document
  search database development).
• October 2002 CDC completed preliminary studies
  of chemical and radionuclide releases.
• Currently CDC is performing radionuclide dose
  reconstructions for selected years at Idaho
  Chemical Processing Plant and screening
  calculations at the Aircraft Nuclear Propulsion
  Program.

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Los Alamos National Laboratory (LANL)

• 1998 CDC began Los Alamos Historical Documents
  Retrieval and Assessment (LAHDRA) Project.
• Documents will be retrieved and evaluated for
  their usefulness for offsite dose assessment.
• Relevant documents will be declassified, copied,
  and made available to the public.
• Relevant documents will be entered into an
  electronic database.
• Prioritized list of contaminant releases from the
  LANL site will be developed.

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Republic of the Marshall Islands (RMI)

• 19461958 RMI was the site of 69 U.S. nuclear
  weapons tests.
• CDC completed a cooperative agreement with the
  RMI government for
• methods development and validation work for
  cesium deposition and
• soil analysis for iodine-129.

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Per Capita Thyroid Dose Estimates From Nuclear
Weapons Tests at the Nevada Test Site
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Nuclear Weapons Fallout Study

• 1998 U.S. Senate Appropriations Committee
  requested a report on the feasibility of studying
  global fallout.
• 1998 CDC and the National Cancer Institute (NCI)
  published feasibility report.
• 19992001 CDC and NCI developed crude
  assessment of dose and risk.
• 2002 Draft technical feasibility report issued
  reviewed by National Academy of Sciences in 2003.

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Savannah River Site, South Carolina

• 19532003 Site produced plutonium and tritium.
• 1992 CDC began dose reconstruction project.
• 1995 CDC issued three reports on Phase I
  (document search and database development).
• 2001 CDC issued final report for Phase II
  (source term development).
• Currently CDC is conducting Phase III (screening
  analyses and preliminary dose estimation).

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Review Process

• All CDC dose reconstruction work is open to the
  public at every stage of the process.
• Each technical report is first published in draft
  form for external technical review and public
  comment.
• Final draft published

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Lessons Learned
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Lessons Learned

• Dose reconstruction requires a great deal of time
  and money.
• Communication materials/strategies are vital.
• Expertise in database management and software
  development is also important.

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Conclusions

• Dose reconstruction is an integral part of
  analytical epidemiology and risk assessment.
• Dose reconstruction is scientifically
  challenging.
• Scientific integrity of dose reconstruction must
  be maintained.
• Public acceptance is vital.