Radiation Exposure in U.S. Atmospheric Nuclear Weapons Testing

The Defense Threat Reduction Agency (DTRA) is the Department of Defense (DOD) executive agent for the 

Nuclear Test Personnel Review (NTPR) Program, which serves the approximately 550,000 veterans who 

participated in U.S. atmospheric nuclear tests, served with the U.S. occupation forces of Hiroshima and 

Nagasaki, Japan, or were prisoners of war in Japan at the conclusion of World War II. The primary purpose of 

the NTPR Program is to provide participation data and radiation dose information for veterans.

U.S. Atmospheric Nuclear Tests

Military and civilian personnel participated in U.S. atmospheric nuclear tests that were conducted primarily in 

Nevada and the Pacific Ocean between 1945 and 1962. Many participants were exposed to low levels of 

ionizing radiation while performing various activities. Over 99 percent of these participants received radiation 

doses that were below the current federal occupational whole body dose limit (5 rem per year); the average 

whole body dose was less than 0.6 rem (see “rem” definition below). Current occupational dose limits for DOD

personnel are codified in DOD instruction 6055.8 and are based upon the Environmental Protection Agency’s 

“Radiation Protection Guidance to Federal Agencies for Occupational Exposure” (1987).

Hiroshima and Nagasaki Occupation Forces

Veterans participated in the post-World War II occupation of Hiroshima and Nagasaki, Japan, or were 

prisoners of war in these areas; over 95 percent of them received radiation doses below 0.1 rem. Only those 

Nagasaki occupation forces that regularly entered the Nishiyama area had the potential to receive doses up to 

and exceeding 1 rem.

Exposure and Dose Units

Ionizing radiation is capable of displacing electrons from atoms or molecules, thereby producing ions. By 

comparison, other radiations (such as microwaves and lasers) are not capable of producing ions and are 

examples of nonionizing radiation. Therefore, quantifying radiation exposure is a vital aspect of radiation 

protection.

Ionizing radiation survey instruments used during the atmospheric testing era (as well as many in use today) 

commonly read in roentgens (R), the traditional unit of exposure. This unit is defined only for photons (gamma

and x-rays) in air, making it of limited use when other radiation types (such as beta particles) or mediums (such 

as tissue) are concerned.

The “rad” is the traditional unit of absorbed dose, which is defined as energy absorbed per unit mass (usually 

in tissue). While absorbed dose is not limited to photons in air, it does not account for the effectiveness of 

different types of ionizing radiation to produce biological damage (i.e., alpha, beta, gamma, and neutron). For 

example, neutrons of specific energies can be more damaging than gamma radiation.
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The “rem” is the traditional unit of dose equivalent, which is used to quantify the potential biological effect of a 

given absorbed dose in humans. Under most circumstances, it can be assumed that 1 R = 1 rad = 1 rem. 

Since most occupationally-exposed individuals receive doses that are much less than 1 rem, it is often 

convenient to speak in terms of millirem, or 1/1000 of a rem.

Radiation Risk

According to the National Council on Radiation Protection and Measurements (NCRP, Report No. 160, 

Table 1.1), the general U.S. population receives about 0.62 rem per year from natural background radiation 

sources (radon, cosmic rays, and rocks) and man-made radiation sources (medical diagnostic x-rays and 

consumer products). As a basis of comparison, a standard diagnostic chest x-ray delivers a radiation dose of 

roughly 0.02 rem. 

The Health Physics Society states that the risk of health effects are either too small to be observed or are 

nonexistent at doses below 5 rem per year, and that radiation-induced health effects have not been 

consistently demonstrated below 10 rem.1

 This position is substantiated by the Radiation Effects Research 

Foundation (formerly the Atomic Bomb Casualty Commission), which has studied the health effects of radiation 

exposure in survivors of the atomic bombings at Hiroshima and Nagasaki since 1946.2

The American Cancer Society (ACS) and the National Cancer Institute (NCI) report the lifetime risk of 

developing any type of cancer for members of the U.S. general population to be greater than 40 percent. The 

lifetime risk is almost 45 percent for males (only), prompting ACS to estimate a man’s lifetime risk of 

developing cancer to be slightly less than 1 in 2. The risk of being diagnosed with cancer generally increases 

with age, as evidenced by the fact that three out of every four cancers are diagnosed in persons 55 and older. 

For more information on cancer incidence and diagnosis, contact ACS (800-ACS-2345, www.cancer.org) or 

NCI (800-4-CANCER, www.cancer.gov).

The federal occupational whole body dose limit (5 rem per year) is believed to carry a low risk of causing 

additional cancers above the level normally observed in the general population. This is supported by the 

lifetime risk model recently developed by the National Academy of Sciences Committee to Assess Health 

Risks from Exposure to Low Levels of Ionizing Radiation (BEIR VII Report), which indicates that one in 

100 persons would be expected to develop some form of cancer (fatal or non-fatal) from a radiation dose of 

10 rem above natural background radiation. By comparison, 42 of the 100 persons would be expected to 

develop cancer from other causes. At a dose of 5 rem, less than three excess fatal cancers would be 

expected in an exposed population of 1,000.

Film Badges

The most common method for measuring dose from ionizing radiation at U.S. atmospheric nuclear tests was 

the issuance of a film badge. Of the 237,000 DOD participants, about 45 percent have recorded doses from 

film badges. None of the Hiroshima or Nagasaki occupation forces were issued film badges. The majority of 

films from these badges are maintained by the Department of Energy at the Nuclear Testing Archive in Las 

Vegas, Nevada (702-295-1628). 

Until 1955, the availability of film badges varied. There were situations in which a group of personnel, such as 

a platoon or ship/aircraft crew, experienced similar conditions and were assigned a single film badge to 

represent the radiation dose for every individual in the group (cohort). The practice of monitoring a group in 

this manner was chosen because every member of the group performed similar work in roughly the same 

radiological environment over a similar duration of time.

After 1955, the DOD and the Atomic Energy Commission changed their policies to require that all participants 

having the potential for radiation exposure at an atmospheric nuclear test site be issued a film badge. Some 

film badges were damaged (by heat, humidity, and other causes), rendering them unreadable. A small number 
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of film badges were issued and not returned or were lost before they could be analyzed.

For additional information on film badges, see the National Research Council (NRC) report “Film Badge 

Dosimetry in Atmospheric Nuclear Tests.3

Reconstructed Doses

When radiation doses from film badges are not available, the NTPR Program performs dose reconstructions to 

calculate a dose using information contained in other records. These records include instrument readings from 

radiological surveys, radiochemistry data from aircraft sampling of nuclear clouds, and laboratory results of 

analyses. As a result, a significant portion of the NTPR effort has focused on characterization of radiological 

environments and developing technical assessment procedures to assess doses for personnel who were not 

issued film badges or personnel whose records are missing or incomplete. Veterans wishing to assist the 

NTPR Program’s dose reconstruction process may provide copies of military records to the NTPR Program.

Dose Reconstruction Methodology

In 1985, the NTPR dose reconstruction methodology was published in Title 32, Code of Federal Regulations, 

Part 218 (32 CFR 218). This methodology has been developed to provide a comprehensive analysis of both 

external and internal radiation doses, for application to units as well as individuals. Since 1985, the scientific 

methods used by the NTPR Program have been reviewed several times by the Government Accountability 

Office and the NRC, most recently in 2003. For more information, see the NTPR Program: Program Reviews 

and Scientific Studies fact sheet on DTRA’s webpage.

The NTPR Program uses the following three alternative approaches, as described in 32 CFR 218, to determine 

the radiation dose to individuals for whom film badge data are not available:

1. Determination of dose potential. Activities of an individual (or their unit) for the period of participation are 

researched. Unit locations and movements of the veteran are related to areas of radioactivity and radiation 

exposure. If personnel were beyond the range of initial radiation exposure from nuclear detonations 

(several miles), were not exposed to fallout, did not enter a radiologically contaminated area, and did not 

come into contact with radioactive materials, the dose evaluation will conclude that no radiation dose was 

received.

2. Dose based on film badges of others. Film badge data from badged personnel are used to derive individual 

radiation doses for unbadged personnel. A homogeneous group of participants is identified, consisting of 

personnel who performed common activities and therefore had a similar potential for radiation exposure. 

Identification of homogeneous groups is based upon research of historical records, technical reports, and 

correspondence. Using standard statistical methods, the film badge data are examined along with unit 

records and any available statements/questionnaires concerning the veteran’s activities to determine 

whether it is valid to assign an entire group’s average radiation dose to an individual. Often the dose or the 

periods over which film badges were worn indicate that the group should be further subdivided into personnel 

performing common functions before proceeding with the analysis. For each homogeneous group, the mean 

and upper-bound radiation doses are obtained from the distribution of film badge readings. The upper-bound 

dose is the value corresponding to a 95 percent probability that the actual dose received by the veteran is 

lower. This procedure ensures that unbadged personnel are provided mean and upper-bound radiation 

doses that reflect the uncertainties exhibited by the spread of film badge readings within their group. If 

individuals cannot be associated with a specific homogeneous group, then film badge doses for this group 

are not used.

3. Dose calculation. In accordance with 32 CFR 218, rigorous dose calculations are performed when film 

badge data is unavailable for all or part of the exposure period. The NTPR Program also performs 

calculations if film badges were damaged and cannot yield reliable dose information, if unique activities are 

credited to specific individuals, or if a neutron dose or a dose to the skin or an internal organ is necessary. 
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These calculations involve correlating the activities of an individual (as described in statements, 

questionnaires, and historical records) with the radiological environments encountered.

Dose Calculation Process

The calculation of a radiation dose is a scientific practice commonly employed by health physicists when an 

individual’s radiation exposure cannot be quantified by dosimetry (such as a film badge). The general process 

of radiation dose reconstruction for veterans is described here:

• The conditions of radiation exposure are reconstructed to include all known activities based on 

statements/questionnaires from the veteran, as well as information from official reports and historical 

documents. These statements and questionnaires form the basis for documenting the veteran’s activities 

and are used along with radiological information to provide dose information.

• The radiation environment is characterized in time and space, and matched with the activities and locations 

of the unit or individual. In addition to external gamma radiation measured by film badges, the contributions 

from other types of radiation (such as neutrons) are considered and included.

• Individual activities, as documented by statements and questionnaires from the veteran (including available 

shielding, body position, and other factors) are quantitatively associated with radiological environment 

information and a total integrated dose is calculated.

• Any available and valid (undamaged and otherwise scientifically accurate) film badge dosimetry is analyzed 

and compared with the calculated radiation dose to establish correlation confidence to the calculations.

• An uncertainty analysis is performed to consider the relative sensitivities of all parameter inputs and to 

provide an upper-bound radiation dose estimate (95th percentile).

Internal Doses

Where the potential existed for inhalation or ingestion of radioactive materials or fallout, internal dose 

commitments from alpha, beta, and gamma radiation to relevant target organs are derived. Since radioactive 

materials entering the body deliver their dose over a period of time (rather than instantly), internal radiation 

doses are determined for a 50-year period after the initial exposure, even if this period extends beyond the 

actual or expected lifetime of the veteran.

Comparison of Reconstructed Doses to Film Badge Records

Prior to implementation of the NTPR dose reconstruction methodology, it was applied to specific scenarios in 

which film badge data were available to determine if the methodology could accurately predict the actual film 

badge results. All parameters relating to radiation exposure (such as body position and activities performed) 

were identified, allowing the reconstructed dose to be directly compared to actual film badge readings. The 

resulting correlations were in satisfactory agreement and provided a high degree of confidence that NTPR 

dose reconstruction methodologies, as codified in 32 CFR 218, accurately predict film badge results.

Expedited Processing

In 2006 and 2007, the Veterans’ Advisory Board on Dose Reconstruction (VBDR) recommended that the 

NTPR Program develop screening procedures for skin, prostate, and posterior subcapsular cataract dose 

assessments that would allow expedited processing of cases for which the doses are well below or well above 

the level likely to result in a successful claim (thereby reducing the time required to generate an analysis of 

these doses). The VBDR also recommended that worst-case upper bound doses be used to provide 

maximum benefit of the doubt for the veteran. Based on subsequent recommendations by VBDR, expedited 

processing was expanded to include all but a select few organs.

Utilizing the scientific methods described above, bounding assumptions about exposure scenarios, and 
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previously calculated doses, the NTPR Program established conservative theoretical maximum doses that are 

much higher than most dose assessments and upper-bound dose determinations that were performed 

previously. Expedited doses are based on worst-case parameters and assumptions, not all of which may have 

been encountered by participating veterans; nevertheless, they are intended to adequately encompass any 

activities performed. To provide maximum benefit of the doubt for the veterans and ensure that reported doses 

are not less than actual doses, veteran input is carefully reviewed to ensure that no activities in an actual 

exposure scenario would result in a higher dose than that generated via the expedited process.

Dose Information Requests

The NTPR Program can provide or research information relevant to a veteran’s radiation exposure

environment, records, or estimates when requested by Veterans Affairs. 

Please note: radiation dose information or confirmation of participation from the NTPR Program is not a 

prerequisite to filing a compensation claim or obtaining priority health care.

NTPR Inquiries

Individuals seeking information about the NTPR Program can address their inquiries to:

Defense Threat Reduction Agency

ATTN: J9-NTSN

8725 John J. Kingman Road, Stop 6201

Fort Belvoir, Virginia 22060-6201

NTPR Program Helpline : 800-462-3683

E-mail: dtra-ntpr@mail.mil

http://www.dtra.mil/Home/NuclearTestPersonnelReview.aspx

May 2015

 1 Health Physics Society, Radiation Risk in Perspective (2004). http://hps.org/documents/radiationrisk.pdf

2 Radiation Effects Research Foundation, Life Span Study Report 13: Solid cancer and noncancer disease mortality: 

1950-1997 (2003).

3 National Research Council, Film Badge Dosimetry in Atmospheric Nuclear Tests (1989). 

http://books.nap.edu/catalog.php?record_id=1404