Ames Laboratory

Special Exposure Cohort 

Petition Evaluation Report

LaVon B. Rutherford, CHP

Special Exposure Cohort Health Physics Team Leader

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support

July 2011
Petition Overview

 March 31, 2011: NIOSH informed an Ames 

Laboratory claimant that we were unable to 

reconstruct the radiation dose for the claim

 April 7, 2011: NIOSH received an 83.14 SEC 

petition

 April 13, 2011: petition qualified for evaluation

 June 9, 2011: NIOSH Evaluation Report issued 
Petition Overview—cont.

 NIOSH proposed class to be added to the SEC:

All Department of Energy employees, its predecessor 

agencies, and its contractors and subcontractors who 

worked in any area of the Ames Laboratory at Iowa State 

University during the period from January 1, 1942 

through December 31, 1970, 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 classes of employees included in the Special 

Exposure Cohort.
Background

 Ames Laboratory is located at Iowa State University 

in Ames, Iowa.

 Ames Laboratory is a DOE facility with operations 

beginning in 1942 and continuing to present.

 During the World War II years, the primary mission 

of the Ames Laboratory was the process 

development and production of uranium and 

thorium metal.

 After the war, the mission of the Ames Laboratory 

shifted to mainly research and development.
Background—cont.

 There currently are three SEC classes associated with 

the Ames Laboratory:

1. All DOE employees or contractors who worked at one of 

the following facilities/locations: Chemistry Annex 1 (also 

known as “the old women’s gymnasium” and “Little 

Ankeny”), Chemistry Annex 2, Chemistry Building (also 

known as “Gilman Hall”), Research Building, or the 

Metallurgical Building (also known as “Harley Wilhelm 

Hall”) from January 1, 1942 through December 31, 1954 

(SEC-0038).
Background—cont.

 SEC classes (cont.): 

2. Sheet metal workers, physical plant maintenance and 

associated support staff (including all maintenance shop 

personnel), and supervisory staff who were monitored or 

should have been monitored for potential internal 

radiation exposures associated with the maintenance 

and renovation activities of the thorium production areas 

in Wilhelm Hall (a.k.a. the Metallurgy Building or “Old” 

Metallurgy Building) at the Ames Laboratory from 

January 1, 1955, through December 31, 1970 (SEC-0075). 
Background—cont.

 SEC classes (cont.):

3. 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 

(SEC-0166).
Background—cont.

 SEC class definition review

• In November 2010, DCAS provided a report (DCAS Assessment 

Report–Review of SEC Class Definitions) that systematically 

reviewed all existing SEC class definitions based on a NIOSH 

evaluation and recommendation to add a class. 

• The class definitions were reviewed based on criteria of 

consistency, applicability, and whether any actions may be 

required by NIOSH to correct an existing class definition (e.g., 

because of possible problems with implementation by DOL). 

• The review was specific to the criteria used in the SEC evaluation 

report to develop the class definition (e.g., feasibility time 

period, access controls, DOL implementation).
Background– cont.

 Review findings

• Most of the issues and discrepancies identified in the DCAS 

report were associated with the evolution of the DCAS 

process for defining a class in an SEC Evaluation Report. 

—Early classes were closely related to the petitioner proposed 

class

—Early classes were established based on perceived limitations 

and sometimes without the review by DOL to ensure they could 

be implemented as written

• Over time, the need to expand and/or adjust the proposed 

SEC class to address DOL class implementation issues was 

recognized to ensure claimants were not inadvertently 

excluded.
Background—cont.

 The report identified a couple of classes 

associated with the Ames Laboratory that had 

potential issues and would not be defined the 

same way using today’s criteria.

• SEC-0038—a facility specific definition associated with 

the 1942 through 1954 period

• SEC-0075—included job specific requirements and 

monitored or should have been monitored criteria for 

the period of 1955 through 1970
Background—cont.

 SEC-0166 Evaluation Report was presented at 

the August 2010 Advisory Board meeting.

 NIOSH recommended a class of “All Employees” 

for the period of 1955 through 1960.

• The end date was based on the petitioner proposed 

end date to expedite the evaluation and move the 

class forward.

• NIOSH committed to continue to review the 

information to ensure a proper end date for the class.
Background---cont.

 The class defined in the SEC-0185 Evaluation 

Report was developed to remove the issues 

associated with the earlier class definitions and 

to provide a proper class end date for SEC-0186.
Feasibility of Dose Reconstruction

 There are insufficient monitoring and source-term data 

from which to draw conclusions regarding potential 

magnitude of internal doses for the period from 

January 1, 1942 through December 31, 1970.

• SEC-0038—infeasibility was driven by the inability to bound 

internal exposures from thorium operations

• SEC-0075—infeasibility was driven by the inability to bound 

thorium exposures during routine maintenance and renovation 

activities at Wilhelm Hall (a.k.a. Metallurgy Building)

• SEC-0166—infeasibility centered around the inability to bound 

internal exposures from radionuclides in the Research Building 

Hot Cave
Feasibility Summary

Feasibility Findings for SEC-00185

Source of Exposure

Dose 

Reconstruction 

Feasible

Dose Reconstruction 

NOT Feasible

Internal

X

External

- Beta-Gamma X

- Neutron X

- Occup. Medical X-ray X
Health Endangerment

 The evidence reviewed in this evaluation 

indicates that some workers in the class may 

have accumulated chronic radiation exposures 

through intakes of radionuclides and direct 

exposure to radioactive materials.

 Consequently, NIOSH is specifying that health 

may have been endangered for those workers 

covered by this evaluation who were 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 established for 

one or more other classes of employees in the 

SEC.
Proposed Class

All Department of Energy employees, its 

predecessor agencies, and its contractors and 

subcontractors who worked in any area of the 

Ames Laboratory at Iowa State University during 

the period from January 1, 1942 through 

December 31, 1970, 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 classes 

of employees included in the Special Exposure 

Cohort.
Recommendation

 For the period January 1, 1942 through 

December 31, 1970, NIOSH finds that radiation 

dose estimates cannot be reconstructed for 

compensation purposes

Class Feasibility Health 

Endangerment

January 1, 1942 –

December 31, 1970 No Yes