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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 Outline Overview of dose reconstruction principles Examples of CDC dose reconstruction projects

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health physics archeology

“Health Physics Archeology”

An Overview of

Dose Reconstruction

Radiation Studies Branch

National Center for Environmental Health

Centers for Disease Control and Prevention

August, 2004

outline
Outline
  • Overview of dose reconstruction principles
  • Examples of CDC dose reconstruction projects
  • Lessons learned from dose reconstruction projects
dose reconstruction
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).

purpose of dose reconstruction
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).
major goals of dose reconstruction
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.

basic assumptions
Basic Assumptions
  • No standard methodological guide book exists.
  • Each site has uniqueattributes.
  • Lessons can be learned from each study.
  • Common approaches can be developed.
dose reconstruction process
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

stages of the process
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 4–7 years or more to complete.
preliminary analysis
Preliminary Analysis
  • Assess the amount of public interest.
  • Conduct a literature review of all research in a related area.
  • Gather all relevant dataand recordsfor the particular site.
  • Conduct personal interviews.
dose assessment
Dose Assessment

Three Levels:

  • Preliminary (Scoping Study)
  • Comprehensive Analysis
  • Individual Dose Assessment
new dose assessment paradigm
New Dose Assessment Paradigm

If risk = health effect, conservative

dose

estimates of dose will be nonconservative

for epidemiology

preliminary dose assessment
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

variables in a scoping study
Variables in a Scoping Study

Conditions of the Release:

  • Chemical and physical form
  • Time dependence

Conditions of the Environment:

  • Geographical
  • Agricultural
  • Meteorological
variables in a scoping study continued
Variables in a Scoping Study (continued)

Conditions of the Population:

  • Size
  • Diversity
  • Structure
  • Human interactions
variables in a scoping study continued17
Variables in a Scoping Study (continued)

Statistical Requirements:

  • Availability and quality of records
  • Doses that can be estimated
  • Large population size
analysis of scoping study results
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.

comprehensive dose assessment
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
comprehensive analysis
Comprehensive Analysis

Ways to determine and estimate the source term:

  • Engineering estimates
  • Historic reports of measured releases
  • Reconstruction

Redundant analyses are desirable.

individual dose assessment
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.
gathering data criteria
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
gathering data source preferences
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
data collection and analysis
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.

other data complications
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
uncertainty analysis
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.’

sensitivity analysis
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.

dose reconstruction and epidemiology
Dose Reconstruction and Epidemiology

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

epidemiology
Epidemiology

The study of disease in human populations

objectives of an epidemiological study
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?
epidemiological studies
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.
epidemiological studies continued
Epidemiological Studies (continued)

Prospective Study

  • Follows two groups through time:

- exposed group

- not exposed group.

  • Compares disease rates between the two groups.
epidemiological studies continued33
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.

no dose response
No Dose Response

Disease

Dose

feasibility analysis
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.

statistical power
Statistical Power

Probability that the study can distinguish between a true exposure-to-disease relation and a coincidence

statistical power40
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
cdc s dose reconstruction projects
CDC’s 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.
cdc s dose reconstruction projects43
CDC’s 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.
slide44

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

fernald ohio
Fernald, Ohio
  • 1951–1988: 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).
  • 1998–1999: CDC performed a risk analysis for lung cancer.
  • June 1999: CDC presented a screening analysis for other cancers.
  • Currently: No additional studies planned.
hanford washington
Hanford, Washington
  • 1944–1990: Site produced plutonium.
  • 1987: CDC began epidemiological project.
  • 1994: CDC released primary results of Hanford Environmental Dose Reconstruction (HEDR).
  • 1998–2000: Washington, Oregon, & Idaho provided individual I-131 dose estimates for exposed people using HEDR models.
  • 2002: Hanford Thyroid Disease Study completed.
hanford washington continued
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
idaho national engineering and environmental laboratory ineel
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.
los alamos national laboratory lanl
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 contaminantreleases from the LANL site will be developed.
republic of the marshall islands rmi
Republic of the Marshall Islands (RMI)
  • 1946–1958: 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.
nuclear weapons fallout study
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.
  • 1999–2001: CDC and NCI developed “crude” assessment of dose and risk.
  • 2002: Draft technical feasibility report issued; reviewed by National Academy of Sciences in 2003.
savannah river site south carolina
Savannah River Site, South Carolina
  • 1953–2003: 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).
review process
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
lessons learned56
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.
conclusions
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.