HHS Special Exposure Cohort Designation:

Rocky Flats Plant, Golden, Colorado

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 

Rocky Flats Plant

Golden, Colorado
HHS Special Exposure Cohort Designation:

Rocky Flats Plant, Golden, Colorado Page 2

I. Designation 

I, Kathleen Sebelius, Secretary of the U.S. Department of Health and Human Services

(HHS), 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.

[Signature on File] December 12, 2013

Kathleen Sebelius Date

II. Employee Class Definition

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

their contractors and subcontractors who worked at the Rocky Flats Plant in 

Golden, Colorado, from April 1, 1952, through December 31, 1983, 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 included 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 the 

Centers for Disease Control and Prevention’s National Institute for Occupational 

Safety and Health (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.
HHS Special Exposure Cohort Designation:

Rocky Flats Plant, Golden, Colorado Page 3

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 November 12, 

2013.

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 doses for members of the proposed 

class included plutonium, tritium, thorium, uranium and associated progeny, 

and/or neptunium-237. The modes of exposure for these radionuclides were 

ingestion and inhalation.

• NIOSH evaluated the available personnel and workplace monitoring data and 

determined that these data are insufficient for estimating internal thorium 

exposures. In the absence of adequate personal or area monitoring, NIOSH 

would employ source term data. 

• NIOSH determined that it lacks sufficient source term data that are inclusive 

of the throughput amounts of thorium (i.e., they only represent a snapshot in 

time with regard to quantities). Therefore, the source term data do not support 

estimating potential internal exposures to thorium during the period of the 

Rocky Flats Plant (RFP) thorium operations from April 1, 1952, through 

December 31, 1966.

• NIOSH determined that uranium bioassay data may not be available for all 

potentially-affected individuals. In addition, the uranium co-worker model 

could not be used because the exposures supported by the uranium co-worker 

model are not necessarily indicative of the exposures that would have 

occurred from the U-233 operations. Those working with U-233 were also 

potentially exposed to Th-228. NIOSH lacks thorium bioassay data for Rocky 

Flats personnel.

• NIOSH determined that workplace air monitoring and contamination surveys 

for U-233 processes are insufficient for dose reconstruction purposes. 

Without uranium and thorium bioassay results, NIOSH concluded that it 

cannot estimate with sufficient accuracy the potential internal exposures to U233, U-232, and Th-228 that the proposed class may have received from 1964 

through 1983.
HHS Special Exposure Cohort Designation:

Rocky Flats Plant, Golden, Colorado Page 4

• Neptunium-237 exposure was associated with, and the result of, preparation of 

pure neptunium oxide, metal and metal alloys, and the recovery of Np-237 

from a variety of residues, including sand, slag, crucibles, casting skulls, and 

alloys. Evidence points to a number of specific tasks performed at the request 

of other DOE laboratories from 1962 through 1983 that involved a few grams 

to a few hundred grams of neptunium. There are only two bioassay samples 

for Np-237and no workplace specific monitoring data. In the absence of 

adequate personal or area monitoring NIOSH would employ source term data.

• NIOSH determined that it lacks sufficient source term data that are inclusive 

of the throughput amounts of neptunium (i.e., they only represent a snapshot 

in time with regard to quantities). These data do not support estimating 

potential internal exposures to neptunium during the period of January 1, 

1962, through December 31, 1983.

• The principal sources of external radiation doses, including medical x-ray 

dose, for members of the proposed class were evaluated in the NIOSH RFP 

SEC-00030 Evaluation Report (ER). In SEC-00030, NIOSH concluded that 

all external dose except neutrons could be estimated with sufficient accuracy. 

• The revision of NIOSH SEC-00192 ER was initiated based on NIOSH’s 

subsequent research and determination that internal radiation exposures to U233, thorium, and Np-237 could not be reconstructed. Consequently, NIOSH 

determined that there is no need to assess external exposures and the ability to 

reconstruct dose at RFP beyond what has already been presented and assessed 

in SEC-00030.

• In sum, NIOSH determined that it lacks sufficient information, which includes 

internal personnel monitoring data, process data, and radiological source term 

information, to allow it to estimate with sufficient accuracy the potential 

internal exposures to radionuclides which include thorium, uranium-233 and 

associated progeny, and/or neptunium-237 for workers at the RFP in Golden, 

Colorado, from April 1, 1952, through December 31, 1983.

• NIOSH determined that there is no need to assess external exposures and the 

ability to reconstruct dose at RFP beyond what has already been presented and 

assessed in SEC-00030.

• Although NIOSH found that it is not possible to completely reconstruct 

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

external monitoring data that may become available for an individual claim 

(and that can be interpreted using existing NIOSH dose reconstruction 

processes or procedures). Therefore, dose reconstructions for individuals 

employed at RFP during the period from April 1, 1952, through December 31, 

1983, but who do not qualify for inclusion in the SEC, may be performed 

using these data as appropriate.
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Rocky Flats Plant, Golden, Colorado Page 5

• 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 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.

• The Board recommended, and the NIOSH Director concurred with, 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), the NIOSH Director 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), the

NIOSH Director 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) The Board and the NIOSH Director 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 NIOSH Director concurred with the Board’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).

V. 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 
HHS Special Exposure Cohort Designation:

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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.”

VI. 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.