HHS Special Exposure Cohort Designation:

Ames Laboratory, Ames, Iowa

HHS Designation of Additional Members of the 

Special Exposure Cohort 

under the 

Energy Employees Occupational Illness Compensation Program Act of 2000 

Designating a Class of Employees from 

Ames Laboratory

Ames, Iowa
HHS Special Exposure Cohort Designation: 

Ames Laboratory, Ames, Iowa Page 2

I. Designation 

I, Kathleen Sebelius, Secretary of Health and Human Services, designate the class 

of employees defined in Section II of this report for addition to the Special Exposure 

Cohort (SEC), as authorized under the Energy Employees Occupational Illness 

Compensation Program Act of 2000 (EEOICPA), 42 U.S.C. § 7384q.

October 6, 2010________ [Signature on File]_____________

Date Kathleen Sebelius

II. Employee Class Definition

All employees of the Department of Energy, its predecessor agencies, and its 

contractors and subcontractors who worked in any area of the Department of 

Energy facility at the Ames Laboratory from January 1, 1955 through December 

31, 1960, for a number of work days aggregating at least 250 work days, 

occurring either solely under this employment, or in combination with work days 

within the parameters established for one or more other classes of employees in 

the Special Exposure Cohort.

III. Designation Criteria and Recommendations

Pursuant to 42 U.S.C. § 7384q, for the class defined in Section II of this report, the 

Secretary has determined, and the Advisory Board on Radiation and Worker Health 

(Board) has recommended, that

(1) it is not feasible to estimate with sufficient accuracy the radiation dose that the 

class received; and

(2) there is a reasonable likelihood that such radiation dose may have 

endangered the health of members of the class.

The SEC final rule states in 42 C.F.R. § 83.13(c)(1) that it is feasible in two situations 

to estimate the radiation dose that the class received with sufficient accuracy. First, 

the rule states that radiation doses may be estimated with sufficient accuracy if 

NIOSH has established that it has access to sufficient information to estimate the 

maximum radiation dose for every type of cancer for which radiation doses are 

reconstructed that could have been incurred under plausible circumstances by any 

member of the class. Alternatively, radiation doses may be estimated with sufficient 

accuracy if NIOSH has established that it has access to sufficient information to 

estimate the radiation doses of members of the class more precisely than a 

maximum dose estimate.

The Board, pursuant to 42 U.S.C. § 7384q, advised the Secretary to designate the 

class as an addition to the SEC in a letter received by the Secretary on September 7, 

2010.
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Ames Laboratory, Ames, Iowa Page 3

IV. Designation Findings

Feasibility of Estimating Radiation Doses with Sufficient Accuracy

The Secretary established the feasibility determination for the class of employees 

covered by this report based upon the findings summarized below.

• Principal sources of internal radiation exposures for members of the proposed 

class included exposures to thorium, thorium decay products including thoron, 

uranium, and the uranium decay products thorium-234 and protactinium-234m.

• NIOSH found that survey and process data are sufficient to bound internal 

uranium exposures for Ames Laboratory workers. NIOSH has not, however,

located sufficient data, including bioassay results, ambient air concentrations, or 

process information to estimate with sufficient accuracy internal exposures to 

radionuclides other than uranium for workers in one of the Ames Laboratory 

buildings (the Research Building (Spedding Hall)), which includes an area known 

as the Hot Canyon. In addition, the Cave within the Hot Canyon did not provide 

a degree of containment that precluded the release of radioactive materials into 

the air. The air within the Cave was shared by the workers outside of it. Lacking 

bioassay data for these workers, air samples for the room, or detailed information 

on the materials being handled, NIOSH cannot assess the internal doses to 

personnel working in the Hot Canyon.

• Because Ames Laboratory employment data do not associate individuals with 

specific buildings or rooms, it is not possible to specify whether employees did or 

did not work in the Research Building; therefore, NIOSH must extend the 

assessment of its inability to bound internal dose in the Research Building to all 

employees, contractors, and subcontractors at the Ames Laboratory facility. 

Consequently, NIOSH finds that it is not feasible to estimate, with sufficient 

accuracy, the total internal dose for workers at the Ames Laboratory site during 

the period from January 1, 1955 through December 31, 1960.

• Principal sources of external radiation exposures for members of the proposed 

class included gamma (photon) and beta radiation associated with handling and 

working in proximity to the uranium decay products, thorium-234 and 

protactinium-234m, and thorium decay products, primarily radium-228.

• NIOSH found that adequate documentation of the employee medical monitoring 

program and film badge results for the period supports the estimation of 

individual external exposures for the evaluated worker class. Therefore, NIOSH

finds that there is sufficient information to bound occupational medical dose and 

external dose for Ames Laboratory workers during all periods. Consequently, 

NIOSH finds that it is feasible to estimate, with sufficient accuracy, the total 

medical X-ray and external dose for workers at the Ames Laboratory site during 

the period from January 1, 1955 through December 31, 1960.

• Pursuant to 42 C.F.R. § 83.13(c)(1), NIOSH determined that there is insufficient 

information to either: (1) estimate the maximum radiation dose, for every type of 

cancer for which radiation doses are reconstructed, that could have been 
HHS Special Exposure Cohort Designation: 

Ames Laboratory, Ames, Iowa Page 4

incurred under plausible circumstances by any member of the class; or (2) 

estimate the radiation doses of members of the class more precisely than a 

maximum dose estimate.

• Although NIOSH found that it is not possible to reconstruct internal radiation 

doses for the proposed class, NIOSH intends to use any internal and external 

monitoring data that may become available (and that can be interpreted using 

existing NIOSH dose reconstruction processes or procedures) for an individual 

claim. Dose reconstructions for individuals employed at the Ames Laboratory 

during the period from January 1, 1955 through December 31, 1960, but who do 

not qualify for inclusion in the SEC, may be performed using these data as 

appropriate.

• NIOSH finds that it is feasible to estimate, with sufficient accuracy, occupational 

medical dose for this class of employees using the assumptions and applicable 

protocols in the complex-wide Technical Information Bulletin, Dose 

Reconstruction from Occupationally Related Diagnostic X-Ray Procedures

(ORAUT-OTIB-0006).

• The Board concurred with the NIOSH evaluation and recommended the 

proposed class for addition to the SEC.

 Health Endangerment

The Secretary established the health endangerment determination for the class of 

employees covered by this report based upon the findings summarized below.

(1) Pursuant to 42 C.F.R. § 83.13(c)(3), NIOSH established that there is a 

reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. Pursuant to 42 C.F.R. § 83.13(c)(3)(ii), 

NIOSH specified a minimum duration of employment to satisfy this health 

endangerment criterion as “having been employed for a number of work days 

aggregating at least 250 work days within the parameters established for this 

class or in combination with work days within the parameters (excluding 

aggregate work day requirements) established for one or more other classes 

of employees in the Cohort.”

(2) NIOSH did not identify any evidence from the petitioners or from other 

resources that would establish that the class was exposed to radiation during 

a discrete incident likely to have involved exceptionally high-level exposures, 

such as a nuclear criticality incident, as defined under 42 C.F.R. § 

83.13(c)(3)(i). 

(3) The Board concurred with NIOSH’s finding that the health of the class may 

have been endangered and defined the class according to the 250-work day 

requirement specified under 42 C.F.R. § 83.13(c)(3)(ii). 
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Ames Laboratory, Ames, Iowa Page 5

IV. Effect and Effective Date of Designation

The Secretary submits this report on the designation of one additional class to the 

SEC for review by Congress, pursuant to 42 U.S.C. §§ 7384l(14)(C)(ii) and 

7384q(c)(2)(A), as amended by the Ronald W. Reagan National Defense 

Authorization Act for Fiscal Year 2005, Pub. L. No. 108-375 (codified as amended in 

scattered sections of 42 U.S.C.). Pursuant to 42 U.S.C. § 7384l(14)(C)(ii), as 

amended by the Ronald W. Reagan National Defense Authorization Act for Fiscal 

Year 2005, Pub. L. No. 108-375 (codified as amended in scattered sections of 42 

U.S.C.), the designation in this report will become effective 30 days after the date of 

this report’s submission to Congress “unless Congress otherwise provides.”

V. Administrative Review of Designation

The health endangerment determination of the designation provided in this report 

may be subject to an administrative review within HHS, pursuant to 42 C.F.R. § 

83.18(a). On the basis of such a review, if the Secretary decides to expand the class 

of employees covered by this designation, the Secretary would transmit a 

supplementary report to Congress providing the expanded employee class definition 

and the criteria and findings on which the decision was based.