SEC Petition Evaluation Report 

Petition SEC-00094 

Report Rev # 0 Report Submittal Date: 3/12/2008 

Subject Expert(s): Joe Guido, Bob Coblentz 

Site Expert(s): N/A 

Petition Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Petition B 

Qualification Date 

DOE/AWE Facility Name 

SEC-00094 83.13 October 11, 2007 Horizons, Inc. 

Petitioner Class Definition 

All employees who worked in all locations at Horizons, Inc., from January 1, 1944 – December 31, 1956 and 

from January 1, 1957 – July 31, 2006 (residual period). 

Class Evaluated by NIOSH 

All Atomic Weapons Employer employees who worked at Horizons, Inc., from January 1, 1944 through 

December 31, 1956 and from January 1, 1957 through July 31, 2006 (residual period). 

NIOSH-Proposed Class(es) to be Added to the SEC 

All Atomic Weapons Employer employees who worked at Horizons, Inc., for a number of work days 

aggregating at least 250 work days from January 1, 1952 through December 31, 1956, or in combination with 

work days within the parameters established for one or more other classes of employees in the SEC. 

Related Petition Summary Information 

SEC Petition Tracking #(s) Petition Type DOE/AWE Facility Name Petition Status 

None 

Related Evaluation Report Information 

Report Title DOE/AWE Facility Name 

None 

ORAU Lead Technical Evaluator: Raymond Weaver ORAU Review Completed By: Daniel H. Stempfley 

Peer Review Completed By: [Signature on file] 

LaVon Rutherford 

03/12/2008 

Date 

SEC Petition Evaluation Reviewed By: [Signature on file] 

J. W. Neton 

03/14/2008 

Date 

SEC Evaluation Approved By: [Signature on file] 

Larry Elliott 

03/14/2008 

Date 
SEC-00094 03-12-08 Horizons, Inc. 

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SEC-00094 03-12-08 Horizons, Inc. 

Evaluation Report Summary: SEC-00094, Horizons, Inc. 

This evaluation report by the National Institute for Occupational Safety and Health (NIOSH) 

addresses a class of employees proposed for addition to the Special Exposure Cohort (SEC) per the 

Energy Employees Occupational Illness Compensation Program Act of 2000, as amended, 42 U.S.C. 

§ 7384 et seq. (EEOICPA) and 42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as 

Members of the Special Exposure Cohort under the Energy Employees Occupational Illness 

Compensation Program Act of 2000. 

Petitioner-Requested Class Definition 

Petition SEC-00094, qualified on October 11, 2007, requested that NIOSH consider the following 

class: All employees who worked in all locations at Horizons, Inc. from January 1, 1944 – December 

31, 1956 and from January 1, 1957 – July 31, 2006 (residual period). 

Class Evaluated by NIOSH 

Based on its preliminary research, NIOSH accepted the petitioner-requested class. NIOSH evaluated 

the following class: All AWE employees who worked at Horizons, Inc. from January 1, 1944 through 

December 31, 1956 and from January 1, 1957 through July 31, 2006 (residual period). 

NIOSH-Proposed Class(es) to be Added to the SEC 

Based on its research, NIOSH evaluated the class to define a single class of employees for which 

NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSH-proposed class includes 

all AWE employees who worked at Horizons, Inc., for a number of work days aggregating at least 250 

work days from January 1, 1952 through December 31, 1956, or in combination with work days 

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

NIOSH modified the petitioner-proposed class because NIOSH has access to the necessary 

information to support its conclusion that the site was not licensed to operate at the covered location 

prior to September 4, 1947, and NIOSH has found no evidence that radiological material was on site 

prior to 1952; therefore, NIOSH finds that there would be no health endangerment associated with 

radiological activities at this site location prior to this time (as discussed below). NIOSH does has 

evidence that site activities involving radioactive material were performed after 1951, and that it lacks 

sufficient information to support the ability to perform bounding dose reconstructions with sufficient 

accuracy for pre-1957 workers; however, NIOSH does have access to sufficient monitoring 

information for the residual radioactivity period to support performing bounding dose reconstructions 

with sufficient accuracy for post-1956 workers. 

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SEC-00094 03-12-08 Horizons, Inc. 

Feasibility of Dose Reconstruction 

NIOSH finds it is not feasible to estimate internal exposures with sufficient accuracy for all workers at 

the site from January 1, 1952 through December 31, 1956 (NIOSH has identified no evidence of 

operations involving radioactive material at the site prior to1952). During this period there was no 

internal monitoring program and there is insufficient other data to support sufficiently accurate 

estimates of these doses. Because of the nature of operations at Horizons, these potential internal 

exposures are not limited to discrete workgroups or operational areas at Horizons; therefore, it is not 

feasible to completely reconstruct the radiation doses of any AWE employees at the facility. With the 

exception of this class, per EEOICPA and 42 C.F.R. § 83.13(c)(1), NIOSH has established that it has 

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

for which radiation doses are reconstructed, that could have been incurred in plausible circumstances 

by any member of the class; or (2) estimate radiation doses of members of the class more precisely 

than an estimate of maximum dose. Information available from additional resources is sufficient to 

document or estimate the maximum internal and external potential exposure to members of the 

proposed class under plausible circumstances during the specified period (the residual period from 

January 1, 1957 through July 31, 2006). 

Health Endangerment Determination 

Per EEOICPA and 42 C.F.R. § 83.13(c)(3), a health endangerment determination is required because 

NIOSH has determined that it is not feasible to estimate with sufficient accuracy doses associated with 

internal exposures for the members of the proposed class from January 1, 1952 through December 31, 

1956. For the post-1956 period, a health endangerment determination is not required because NIOSH 

has determined that it has sufficient information to estimate dose for the members of the proposed 

class. 

NIOSH has confirmed that it has the necessary information to conclude that the site was not licensed 

to operate at the covered location prior to September 4, 1947, and NIOSH has no evidence of 

radioactive material on site prior to 1952. Consequently, NIOSH finds there would be no radiological 

source of exposure, and thus, no health endangerment associated with radiological activities at this 

location prior to January 1, 1952. Therefore, the determination for the period from January 1, 1944 

through December 31, 1951 is that there was no health endangerment. 

NIOSH did not identify any evidence supplied by the petitioners or from other resources that would 

establish that the proposed class who worked at Horizons, Inc., from January 1, 1952 through 

December 31, 1956 was exposed to radiation during a discrete incident likely to have involved 

exceptionally high-level exposures. However, evidence indicates that some workers in this proposed 

class may have accumulated substantial chronic internal exposures through episodic intakes of 

radionuclides, combined with external exposures to gamma and beta radiation. Consequently, NIOSH 

has determined that health was endangered for those workers covered by the NIOSH-proposed SEC 

class defined in this evaluation who were employed for at least 250 aggregated work days either solely 

under their employment or in combination with work days within the parameters established for other 

SEC classes (excluding aggregate work day requirements). 

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Table of Contents 

Evaluation Report Summary: SEC-00094, Horizons, Inc. ...................................................................... 3 

1.0 Purpose and Scope.......................................................................................................................... 7 

2.0 Introduction .................................................................................................................................... 7 

3.0 Petitioner-Requested Class/Basis & NIOSH-Proposed Class/Basis .............................................. 8 

4.0 Data Sources Reviewed by NIOSH................................................................................................ 9 

4.1 Site Profile Technical Basis Documents (TBDs) .................................................................. 9 

4.2 ORAU Technical Information Bulletins (OTIBs) and Procedures ..................................... 10 

4.3 Facility Employees and Experts .......................................................................................... 10 

4.4 Previous Dose Reconstructions ........................................................................................... 11 

4.5 NIOSH Site Research Database .......................................................................................... 11 

4.6 Other Technical Sources...................................................................................................... 12 

4.7 Documentation and/or Affidavits Provided by Petitioners ................................................. 12 

5.0 Radiological Operations Relevant to the Class Evaluated by NIOSH ......................................... 12 

5.1 Horizons Plant and Process Descriptions ............................................................................ 12 

5.2 Horizons Functional Areas .................................................................................................. 14 

5.2.1 Horizons Thorium Operations ................................................................................. 14 

5.2.2 Horizons Uranium Operations................................................................................. 14 

5.2.3 Horizons Silver Operations ..................................................................................... 15 

5.2.4 Summary of Key Horizons Operations ................................................................... 15 

5.3 Radiological Exposure Sources from Horizons Operations ................................................ 16 

5.3.1 Alpha ....................................................................................................................... 17 

5.3.2 Beta.......................................................................................................................... 17 

5.3.3 Neutron .................................................................................................................... 18 

5.3.4 Photon...................................................................................................................... 18 

5.3.5 Incidents .................................................................................................................. 18 

6.0 Summary of Available Monitoring Data for the Class Evaluated by NIOSH ............................. 18 

6.1 Horizons Internal Monitoring Data ..................................................................................... 18 

6.2 Horizons External Monitoring Data .................................................................................... 19 

6.3 Horizons Air Sampling Data ............................................................................................... 19
 

7.0 Feasibility of Dose Reconstruction for the Class Evaluated by NIOSH ...................................... 20 

7.1 Pedigree of Horizons Data................................................................................................... 20 

7.1.1 Internal Monitoring Data Review............................................................................ 21 

7.1.2 External Monitoring Data Review........................................................................... 21 

7.2 Internal Radiation Doses at Horizons.................................................................................. 22 

7.2.1 Sources of Internal Radiation Dose and Related Monitoring Data ......................... 22 

7.2.1.1 Operations-Related Internal Dose ............................................................ 23 

7.2.1.2 Residual Radioactivity-Related Internal Dose ......................................... 24 

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7.2.2 Internal Dose Reconstruction .................................................................................. 24 

7.2.2.1 Operational Period .................................................................................... 24 

7.2.2.2 Residual Period......................................................................................... 25 

7.2.3 Internal Dose Reconstruction Feasibility Conclusion ............................................. 28 

7.3 External Radiation Doses at Horizons................................................................................. 29 

7.3.1 Sources of External Radiation Dose and Related Monitoring Data ........................ 29 

7.3.1.1 Operations-Related External Dose ........................................................... 29 

7.3.1.2 Residual Radioactivity Period-Related External Dose............................. 29 

7.3.2 Horizons Occupational X-Ray Examinations ......................................................... 29 

7.3.3 External Dose Reconstruction ................................................................................. 30 

7.3.3.1 Photon/Electron Dose during the Operational Period .............................. 30 

7.3.3.2 Photon/Electron Dose during the Residual Period ................................... 31 

7.3.3.3 Medical X-ray........................................................................................... 32 

7.3.4 External Dose Reconstruction Feasibility Conclusion ............................................ 32 

7.4 Evaluation of Petition Basis for SEC-00094 ....................................................................... 32 

7.5 Summary of Feasibility Findings for Petition SEC-00094.................................................. 33 

8.0 Evaluation of Health Endangerment for Petition SEC-00094...................................................... 34 

9.0 NIOSH-Proposed Class for Petition SEC-00094 ......................................................................... 34 

10.0 References .................................................................................................................................... 37 

Tables 

4-1: No. of Horizons Claims Submitted Under the Dose Reconstruction Rule .................................... 11 

5-1: Horizons Operating Facilities ........................................................................................................ 13 

5-2: Horizons Key Operations and Dates of Operation......................................................................... 16 

7-1: Thorium and Ra-228 Inhalation..................................................................................................... 26 

7-2: Thorium and Ra-228 Ingestion ...................................................................................................... 27 

7-3: Thoron (Rn-220) ............................................................................................................................ 28 

7-4: Horizons Film Badge Gamma Radiation Results .......................................................................... 31 

7-5: Horizons Film Badge Beta Radiation Results................................................................................ 31 

7-6: Summary of Available Data........................................................................................................... 31 

7-7: Recommended Dose Values .......................................................................................................... 32 

7-8: Summary of Feasibility Findings for SEC-00094.......................................................................... 33 

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SEC-00094 03-12-08 Horizons, Inc. 

SEC Petition Evaluation Report for SEC-00094 

ATTRIBUTION AND ANNOTATION: This is a single-author document. All conclusions drawn from 

the data presented in this evaluation were made by the Oak Ridge Associated Universities Team Lead 

Technical Evaluator: Raymond Weaver, MJW Corp. These conclusions were peer-reviewed by the 

individuals listed on the cover page. The rationales for all conclusions in this document are explained 

in the associated text. 

1.0 Purpose and Scope 

This report evaluates the feasibility of reconstructing doses for all employees who worked at 

Horizons, Inc., from January 1, 1944 through December 31, 1956 and from January 1, 1957 through 

July 31, 2006 (residual period). It provides information and analyses germane to considering a 

petition for adding a class of employees to the congressionally-created SEC. 

This report does not make any determinations concerning the feasibility of dose reconstruction that 

necessarily apply to any individual energy employee who might require a dose reconstruction from 

NIOSH. This report also does not contain the final determination as to whether the proposed class 

will be added to the SEC (see Section 2.0). 

This evaluation was conducted in accordance with the requirements of EEOICPA, 42 C.F.R. pt. 83, 

and the guidance contained in the Office of Compensation Analysis and Support’s (OCAS) Internal 

Procedures for the Evaluation of Special Exposure Cohort Petitions, OCAS-PR-004. 

2.0 Introduction 

Both EEOICPA and 42 C.F.R. pt. 83 require NIOSH to evaluate qualified petitions requesting that the 

Department of Health and Human Services (HHS) add a class of employees to the SEC. The 

evaluation is intended to provide a fair, science-based determination of whether it is feasible to 

estimate with sufficient accuracy the radiation doses of the class of employees through NIOSH dose 

reconstructions.1 

42 C.F.R. § 83.13(c)(1) states: Radiation doses can 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 in 

plausible circumstances by any member of the class, or if NIOSH has established that it has access to 

sufficient information to estimate the radiation doses of members of the class more precisely than an 

estimate of the maximum radiation dose. 

1

 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 C.F.R. pt. 82 and 

the detailed implementation guidelines available at http://www.cdc.gov/niosh/ocas. 

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SEC-00094 03-12-08 Horizons, Inc. 

Under 42 C.F.R. § 83.13(c)(3), if it is not feasible to estimate with sufficient accuracy radiation doses 

for members of the class, then NIOSH must determine that there is a reasonable likelihood that such 

radiation doses may have endangered the health of members of the class The regulation requires 

NIOSH to assume that any duration of unprotected exposure may have endangered the health of 

members of a class when it has been established that the class may have been exposed to radiation 

during a discrete incident likely to have involved levels of exposure similarly high to those occurring 

during nuclear criticality incidents. If the occurrence of such an exceptionally high-level exposure has 

not been established, then NIOSH is required to specify that health was endangered for those workers 

who were employed for at least 250 aggregated work days within the parameters established for the 

class or in combination with work days within the parameters established for other SEC classes 

(excluding aggregate work day requirements). 

NIOSH is required to document its evaluation in a report, and to do so, relies upon both its own dose 

reconstruction expertise as well as technical support from its contractor, Oak Ridge Associated 

Universities (ORAU). Once completed, NIOSH provides the report to both the petitioner(s) and to the 

Advisory Board on Radiation and Worker Health (Board). The Board will consider the NIOSH 

evaluation report, together with the petition, petitioner(s) comments, and other information the Board 

considers appropriate, in order to make recommendations to the Secretary of HHS on whether or not 

to add one or more classes of employees to the SEC. Once NIOSH has received and considered the 

advice of the Board, the Director of NIOSH will propose a decision on behalf of HHS. The Secretary 

of HHS will make the final decision, taking into account the NIOSH evaluation, the advice of the 

Board, and the proposed decision issued by NIOSH. As part of this decision process, petitioners may 

seek a review of certain types of final decisions issued by the Secretary of HHS.2 

3.0 Petitioner-Requested Class/Basis & NIOSH-Proposed Class/Basis 

Petition SEC-00094, qualified on October 11, 2007, requested that NIOSH consider the following 

class for addition to the SEC: All employees who worked in all locations at Horizons, Inc., from 

January 1, 1944 – December 31, 1956 and from January 1, 1957 – July 31, 2006 (residual period). 

The petitioner provided information and affidavit statements in support of the petitioner’s belief that 

accurate dose reconstruction over time is impossible for the Horizons workers in question. NIOSH 

deemed the following information and affidavit statements sufficient to qualify SEC-00094 for 

evaluation: 

The petitioner provided an affidavit claiming that he/she has no knowledge of any 

monitoring data at Horizons, Inc. 

Based on its Horizons research and data capture efforts, NIOSH determined that it has access to 

external monitoring data and records for Horizons workers during the time period under evaluation. 

However, NIOSH also determined that internal monitoring records are not complete for all time 

periods or for all radionuclides. NIOSH concluded that there is sufficient documentation to support 

the petition basis that internal radiation exposures and radiation doses were not adequately monitored 

at Horizons, either through personal monitoring or area monitoring for the period from January 1, 

2 See 42 C.F.R. pt. 83 for a full description of the procedures summarized here. Additional internal procedures are 

available at http://www.cdc.gov/niosh/ocas. 

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SEC-00094 03-12-08 Horizons, Inc. 

1952 through December 31, 1956. The information and statements provided by the petitioner, and the 

lack of internal monitoring data, qualified petition SEC-00094 to be evaluated for further 

consideration by NIOSH, the Board, and HHS. The details of the petition basis are addressed in 

Section 7.4. 

Based on its research, NIOSH modified the petitioner-requested class as to define a single class of 

employees for which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSHproposed class includes all Atomic Weapons Employer (AWE) employees who worked at Horizons, 

Inc., for a number of work days aggregating at least 250 work days from January 1, 1952 through 

December 31, 1956, or in combination with work days within the parameters established for one or 

more other classes of employees in the SEC. The class was modified as a result of the review of site 

operations documented in Section 5.0 and the feasibility evaluation documented in Section 7.0. 

4.0 Data Sources Reviewed by NIOSH 

NIOSH identified and reviewed numerous data sources to evaluate the feasibility of dose 

reconstruction for the class of employees proposed for this petition. This included determining the 

availability of information on personal monitoring, area monitoring, industrial processes, and 

radiation source materials. The following subsections summarize the data sources identified and 

reviewed by NIOSH. 

4.1 Site Profile Technical Basis Documents (TBDs) 

A Site Profile provides specific information concerning the documentation of historical practices at 

the specified site. Dose reconstructors can use the Site Profile to evaluate internal and external 

dosimetry data for monitored and unmonitored workers, and to supplement, or substitute for, 

individual monitoring data. A Site Profile consists of an Introduction and five Technical Basis 

Documents (TBDs) that provide process history information, information on personal and area 

monitoring, radiation source descriptions, and references to primary documents relevant to the 

radiological operations at the site. The Site Profile for a small site may consist of a single document. 

No site profile has been developed for Horizons, Inc. However, as part of this evaluation, NIOSH 

examined the following TBDs for insights into Horizons operations or related topics/operations at 

other sites: 

•	 TBD: Site Profiles for Atomic Weapons Employers that Worked Uranium and Thorium, BattelleTBD-6000, Rev. F0; December 13, 2006; SRDB Ref ID: 30671 

•	 TBD: Site Profiles for Atomic Weapons Employers that Refined Uranium and Thorium, BattelleTBD-6001, Rev. F0; December 13, 2006; SRDB Ref ID: 30673 

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4.2 ORAU Technical Information Bulletins (OTIBs) and Procedures 

An ORAU Technical Information Bulletin (OTIB) is a general working document that provides 

guidance for preparing dose reconstructions at particular sites or categories of sites. An ORAU 

Procedure provides specific requirements and guidance regarding EEOICPA project-level activities, 

including preparation of dose reconstructions at particular sites or categories of sites. NIOSH 

reviewed the following OTIBs and procedure as part of its evaluation: 

•	 OTIB: Dose Reconstruction From Occupationally Related X-Ray Procedures, ORAUT-OTIB0006, Rev 03 PC-1; December 21, 2005; SRDB Ref ID: 20220 

•	 OTIB: Lung Dose Conversion Factor For Thoron WLM, OCAS-TIB-0011, Rev 2; January 13, 

2006; SRDB Ref ID: 22409 

•	 PROC: Occupational X-Ray Dose Reconstruction for DOE Sites, ORAUT-PROC-0061, Rev 00; 

July 21, 2006; SRDB Ref ID: 29987 

•	 TIB: Default Assumptions and Methods for Atomic Weapons Employer Dose Reconstructions, 

Battelle-TIB-5000, Rev. 00; April 7, 2007; SRBD Ref ID: 32016 

4.3 Facility Employees and Experts 

To obtain additional information, NIOSH researched its NOCTS database, located one former 

Horizons employee who is still alive, and interviewed this individual. As of the time of this report, all 

other claims in NOCTS are for Horizons employees who are deceased. 

•	 Personal Communication, 2007, Personal Communication with Metallurgical Engineer; 

Telephone Interview by ORAU Team; November 26, 2007; OSA Ref ID: 38320 

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4.4 Previous Dose Reconstructions 

NIOSH reviewed its NIOSH OCAS Claims Tracking System (NOCTS) to locate EEOICPA-related 

dose reconstructions that might provide information relevant to the petition evaluation. A review of 

the employment history for the four claims in NOCTS indicates that none of the four had employment 

prior to January 1, 1952. This supports the NIOSH determination that AEC radiological work was not 

performed at the Horizons facility prior to January 1, 1952. Table 4-1 summarizes the results of this 

review for the evaluated class period of January 1, 1944 through December 31, 1956, and from 

January 1, 1957 through July 31, 2006 (residual period). (NOCTS data available as of March 14, 

2008). 

Table 4-1: No. of Horizons Claims Submitted Under the Dose Reconstruction Rule 

Description Totals 

Total number of claims submitted for dose reconstruction 4 

Total number of claims submitted for energy employees who meet the proposed class definition 

criteria with employment from January 1, 1944 through December 31, 1956 and from January 1, 

1957 through July 31, 2006 (residual period) 4 

Number of dose reconstructions completed for energy employees who meet the proposed class 

definition criteria 0 

Number of claims for which internal dosimetry records were obtained for the identified years in the 

proposed class definition 0 

Number of claims for which external dosimetry records were obtained for the identified years in the 

proposed class definition 3 

NIOSH reviewed each claim to determine whether internal and/or external personal monitoring 

records could be obtained for the employee. NIOSH located external monitoring data for the period 

evaluated in this report, but no internal monitoring data. 

4.5 NIOSH Site Research Database 

NIOSH also examined its Site Research Database to locate documents supporting the evaluation of 

the proposed class. Seventy-eight documents in this database were identified as pertaining to 

Horizons, Inc. These documents were evaluated for their relevance to this petition. The documents 

include historical background on monitoring, some program descriptions, process material 

information, process descriptions, air monitoring data, as well as later Formerly Utilized Sites 

Remedial Action Program (FUSRAP) and site D&D/remediation information. 

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4.6 Other Technical Sources 

Information on AEC-related work performed by Horizons was also identified and gathered from the 

State of Ohio Department of Health, and from the United States Department of Energy, Office of 

Scientific and Technical Information (OSTI). 

4.7 Documentation and/or Affidavits Provided by Petitioners 

In qualifying and evaluating the petition, NIOSH reviewed the following documents submitted by the 

petitioners: 

• Affidavit from [Survivor Name redacted]; November 26, 2007; OSA Ref ID: 38320 

5.0 Radiological Operations Relevant to the Class Evaluated by 

NIOSH 

The following subsections summarize both radiological operations at the Horizons, Inc., facility from 

January 1, 1944 through December 31, 1956 and from January 1, 1957 through July 31, 2006 

(residual period), and the information available to NIOSH to characterize particular processes and 

radioactive source materials. From available sources NIOSH has gathered process and source 

descriptions, information regarding the identity and quantities of each radionuclide of concern, and 

information describing both processes through which radiation exposures may have occurred and the 

physical environment in which they may have occurred. The information included within this 

evaluation report is only a summary of the available information. 

5.1 Horizons Plant and Process Descriptions 

There are no records of any operations at the Cleveland, Ohio facility prior to September 1947. 

Available documentation indicates that Horizons, Inc., was not performing business in Ohio prior to 

this time; Horizons was licensed to do business in the state of Ohio on September 4, 1947 (License, 

1993). The MED/AEC-related work under evaluation was performed at the facility owned and 

operated by Horizons, Inc., and located at 2909 East 79th St. in Cleveland, Ohio. Two of the three 

original buildings (B and C) at this location were initially used to perform research and development 

of electrochemical processes, and then during the 1950s, production processes for the Atomic Energy 

Commission (AEC) and other government agencies (Wagoner, 1990). A third original building also 

existed at the facility. No specific information is available regarding activities or operations that may 

have been performed in that building; however, available site remediation documentation does appear 

to indicate that no radioactive material operations were performed in this third building. However, 

due to the widespread contamination from the Horizons processes, and the inability to identify or 

designate specific work locations for any workers, no specific work locations or buildings will be 

called out in the evaluation of the proposed Horizons worker class. The conclusions and 

recommendations presented in this report include all Horizons work locations. 

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SEC-00094 03-12-08 Horizons, Inc. 

Horizons was working in the field of high-temperature fused salt electrochemistry as early as 1948. 

Most of the research was with titanium and zirconium. In early 1949, Horizons was contracted by the 

AEC to determine the feasibility of producing ductile zirconium in coherent form via electrolysis. 

From April 1952 through June 1956, Horizons was contracted by the AEC to determine the most 

economical method for the production of thorium metal. During the same time period, another 

contract covered research and development of high-purity niobium metal via electrolysis (FUSRAP, 

1985). In addition to the thorium contract work, Horizons also had other radiological contracts, 

licenses, research, and work associated with uranium (Musser, 1954; USAEC, 1956) and radioactive 

silver (USAEC, 1958; USNRC, 1993; Maybaum, 1958). 

In December 1954, a radiological survey was conducted by the AEC’s Health and Safety Laboratory 

(HASL) (HASL, 1955). This survey discovered poor housekeeping, inadequate ventilation, 

nonexistent controls for certain operations, and improper work habits in violation of accepted 

housekeeping procedures. 

In February 1977, Oak Ridge National Laboratory (ORNL) conducted a radiological survey as part of 

the FUSRAP program. The survey results identified thorium contamination in excess of free-release 

limits (ORNL, 1977). 

In 1997 and 1998, another radiological survey was conducted by B. Koh & Associates which 

confirmed that thorium was present in excess of free-release limits (Koh, 1998). As a result of these 

findings, B. Koh & Associates developed and submitted a Site Remediation Plan in March 1998 (Koh, 

1998). 

Table 5-1 summarizes the Horizons, Inc., known facility operations over the period under evaluation. 

Table 5-1: Horizons Operating Facilities 

Building Purpose 

B Wet Plant (24,500 ft2

): Feed material received, weighed into batches, placed into a dissolving tank, 

blended, and transferred as a salt to Dry Plant. 

C Dry Plant (5,185 ft2

): Metal was produced via an electrolytic process; metal was chipped from a 

cathode, crushed, dried, and packaged for final shipment. 

Note: The source for the above information is the NRC inspection summary report for the former Horizons, Inc., site 

(USNRC, 1993). NIOSH research discovered no radiological information regarding a third original building at the 

Horizons, Inc., Cleveland location. 

One report (FUSRAP, 1985) indicates that the buildings used for radiological work (B and C) may 

have more recently been consolidated into one large facility. Horizons sold the Cleveland facility 

during the 1966-67 timeframe. The facility changed hands several times in the years following the 

Horizons sale. The companies that owned and operated the former Horizons facilities constructed 

additions to the existing buildings and used the buildings for non-radioactive activities (USNRC, 

1993). 

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5.2 Horizons Functional Areas 

Horizons operations included the following functional areas: 

• Thorium operations 

• Uranium operations 

• Silver operations 

5.2.1 Horizons Thorium Operations 

The thorium processes and activities, which were the largest radiological activities performed on the 

site, were performed in both Buildings B and C. Building C was originally used for receiving and 

processing radioactive materials, and Building B was used for bulk storage and final processing of the 

radioactive materials. The feed material was brought into the Wet Plant (Building C), weighed into 

batches, and placed in a dissolving tank. The thorium nitrate was converted to ammonium thorium 

chloride, blended with sodium chloride, and then transferred as a calcined salt to the Dry Plant 

(Building B), where thorium metal was produced by a high-temperature electrolytic process. The 

resulting metal was chipped from the cathode, crushed, washed, dried, and packaged in Building B for 

final shipment off site (USNRC, 1993). 

From April 1952 to April 1954, Horizons focused on evaluation of all possible systems or methods for 

production and extrusion of thorium metal. Electrolytic operations were conducted in small, researchsized laboratory cells originally designed for titanium and zirconium metal research and production 

(FUSRAP, 1985). 

In May 1954, by direction of the AEC, Horizons activities increased from small developmental 

quantities of thorium metal to scale pilot-plant operations for the production of hundreds of pounds of 

thorium. According to Horizons own “final report” (Fisher, 1956), this scale-up was initiated with 

little regard for suitability of the process for preparation of thorium nitrate tetrahydrate and availability 

of suitable equipment. This scale-up to production levels of thorium metal was to be accomplished 

within a six-month period. By the end of July 1954, 2000 pounds of thorium nitrate tetrahydrate had 

been delivered to the Horizons facility to be used as feed material for the electrochemical process. 

During summer 1955, up to 10,000 pounds of thorium nitrate had been delivered to Horizons, yet by 

June 1956 all production related to thorium metal recovery had stopped (Fisher, 1956). 

5.2.2 Horizons Uranium Operations 

Horizons conducted research and development work with uranium metal. A 1953 Horizons 

semi-annual report to the AEC concerning research issuance material indicates the receipt of eight 

bars of uranium metal (total: 8290.8 grams) (Semi-annual Report, 1953). Another AEC memo in May 

1954 indicates that Horizons received 39.8 pounds of uranium bars and blocks in support of uranium 

research (Uranium Bars, 1954). Although limited information exists on the actual operations, it 

appears that the research performed with this material included roll-cladding experimentation 

(cladding of uranium with zirconium). In July 1955, Horizons submitted a proposal for the research 

into electrolytic production of uranium; however, the AEC rejected the proposal (Bloch, 1955; 

FUSRAP, 1985). 

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5.2.3 Horizons Silver Operations 

A July 1954 letter discusses the desired research to be performed at Horizons (Mataich, 1954). 

Planned research included the use of radioactive silver in fundamental studies to determine the surface 

diffusion rate of silver on gold or other materials. The process and controls are generally described in 

the letter, including the requirement to perform the work in a hood, for personnel to wear film badges, 

and for radiological surveys of the areas where work is to be performed. In 1955, Horizons requested 

a license from the AEC for 20 mCi of Ag-110 for research purposes. This material was received, 

used, and shipped back to the AEC (i.e., Oak Ridge National Laboratory) by September 23, 1958 

(Maybaum, 1958). NIOSH concluded that the material being used was actually Ag-110m. Ag-110 

has a 24.6-second half-life; therefore, Ag-110 would have decayed prior to receipt (Ag-110m has a 

250-day half-life). 

It appears that radioactive silver (Ag-110m) may have been on site during the residual radioactivity 

period. However, any potential internal dose associated with Ag-100m will not be included or 

accounted for in this report because silver operations were not part of the AEC-related work, and 

therefore, are not covered under the EEOICPA radiological dose reconstruction program for the 

residual radioactivity period. Therefore, further discussion of this radionuclide is not included or 

evaluated for the residual radioactivity period. 

5.2.4 Summary of Key Horizons Operations 

NIOSH reviewed the available information and determined that each of the thorium, uranium, and 

silver operations occurred within the time period under evaluation in this report. There is no 

information regarding AEC-related thorium operations for the period prior to 1952, nor information 

that indicates these thorium operations occurred prior to 1952 The information associated with the 

uranium operations is limited, but documentation states that uranium was on site in 1953 (DOE, 

1985). Research using radioactive silver is not discussed in the available documentation prior to 1954 

(Maybaum, 1958). The earliest available radioactive silver license request would support that 

radioactive silver was not on site until 1955 (DOE, 1985). All AEC-related activities associated with 

these radionuclides ended at Horizons in 1956, although some of the radioactive silver may have 

remained on site for other non-AEC related work after AEC-related operations were terminated 

(possibly remaining on site up to 1958) (Maybaum, 1958; FUSRAP, 1985). 

As previously discussed, NIOSH has information that Horizons was working in the field of 

high-temperature fused-salt electrochemistry (mostly with titanium and zirconium) as early as 1948. 

In early 1949, Horizons was contracted for non-radioactive work by the AEC to determine the 

feasibility of producing ductile zirconium in coherent form via electrolysis. NIOSH has discovered no 

information for any operations or activities at the Horizons site in Cleveland prior to September 4, 

1947. 

Documentation demonstrates that AEC-related radioactive operations stopped at the Horizons facility 

after December 31, 1956. After January 1, 1957, the Horizons facility was used by other companies 

to perform non-radiological commercial work (Plan, 1993). Clean-up of the former Horizons facility 

was performed in the late 1990s. On February 26, 2001, an inspection of the clean-up work was 

performed by the NRC who deemed the facility acceptable for “free release” (Remediation Report, 

2001). 

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Table 5-2 summarizes the Horizons, Inc., key processes and dates of operation known to NIOSH. 

Table 5-2: Horizons Key Operations and Dates of Operation 

Operation Associated Activity Dates 

Thorium Thorium electrolytic processing and associated operations 1952-1956 

Uranium Uranium roll-cladding experimentation and review of electrolytic processing 1953-1956 

Silver Research into the diffusion rate of silver in other materials 1954-1956 

Based on the above information, NIOSH has concluded there was no potential for any AEC-related 

operations at the Horizons site prior to January 1, 1952. Therefore, further evaluation of the 

pre-January 1, 1952 period will not be performed or included in this report. 

Documentation and information supports that Horizons performed AEC-related activities after 

September 4, 1947. However, NIOSH has no evidence of radioactive material on site prior to 1952. 

Based on the available information, all AEC-related work at Horizons stopped in 1956. On February 

26, 2001, the site was deemed remediated and acceptable for “free release”; however, NIOSH has 

maintained the end date for the residual period as July 31, 2006 to be consistent with the DOE Office 

of Worker Advocacy, and in light of NIOSH’s dose reconstruction feasibility conclusions for the 

residual radioactivity period (see Section 7.0). Therefore, NIOSH concludes that the operational 

period to be evaluated in this report extends from January 1, 1952 through December 31, 1956, and 

the residual radioactivity period to be evaluated in this report extends from January 1, 1957 through 

July 31, 2006. 

5.3 Radiological Exposure Sources from Horizons Operations 

The thorium and uranium electrolytic processing operations at Horizons resulted in alpha, beta, and 

gamma radiation exposures to workers. Because of the comparative sizes of the associated operations 

(thorium activities were much larger in scale than the uranium operations), the greatest source of 

contamination and internal radiological exposures in the buildings resulted from surface, airborne, and 

re-suspended dust particles contaminated with thorium and its progeny (e.g., thoron). During the 

production operations, thorium surface contamination and airborne dust resulted from hightemperature electrolytic processing, manual operations, and hand contact (e.g., chipping, crushing, 

sweeping) with thorium and uranium materials. In addition, radioactive silver (posing a beta radiation 

exposure hazard) was used on site for diffusion studies and research. 

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After the AEC-related operations were terminated at Horizons, residual thorium, thorium progeny and 

uranium radioactivity remained at levels that can be bounded by the operational exposure data. Work 

during the residual era also included alpha and gamma radiation exposures to workers. The residual 

exposures would have resulted from workers being in close proximity to contamination as well as the 

re-suspension of contaminated particles remaining from the Horizons operational period. The specific 

sources of exposure are listed in the following sections. 

5.3.1 Alpha 

Alpha particle emissions from the radioactive materials handled at Horizons present the greatest 

potential for exposure through internal deposition via inhalation and ingestion (alpha particles do not 

present an external exposure hazard). The principal alpha-emitting radioactive materials associated 

with Horizons, Inc. operations were uranium and thorium (and associated progeny). Processed natural 

uranium consists of approximately equal activities of U-238 (4.20 MeV and 4.15 MeV alpha particles) 

and U-234 (4.77 MeV and 4.72 MeV alpha particles) (Radiological Health, 1970). There are smaller 

amounts of U-235 (approximately 1/20 of the activity levels of U-238 or U-234) with alpha particles 

of 4.40 MeV and 4.36 MeV. 

Th-232 emits alpha particles of 4.01 MeV and 3.95 MeV, and the natural thorium decay series 

includes six daughter products that also emit alpha particles, with energies ranging from 5.34 MeV to 

8.78 MeV. The abundance of these daughter product emissions depends on the state of equilibrium 

with the Th-232 parent. Th-232 decays into Ra-228, emitting two primary alpha particles of 3.95 

MeV (24%) and 4.01 MeV (76%). The decay series contains several other progeny, most of which 

decay by alpha particle emission, but each has a half-life of less than 12 hours. Other isotopes of 

thorium were likely to have existed at Horizons, including Th-228 (5.52 MeV) and Th-230 (4.62 MeV 

and 4.69 MeV), and are considered contributors to the thorium dose at the site. 

5.3.2 Beta 

As with the alpha emitters, the majority of the beta exposures at Horizons could have resulted from 

exposure to natural thorium and its progeny, or uranium and its decay products. For processed natural 

uranium, the dominant beta radiation was likely from U-238 decay products. The most energetic of 

these beta particles is 2.29 MeV from Pa-234m. 

Thorium processes also involved unshielded contact with sources of beta radiation. While Th-232 

itself does not emit beta particles, five of the daughter radionuclides in the natural thorium decay 

series do have beta emissions, ranging in energy up to a maximum of 2.26 MeV (Radiological Health, 

1970). The abundance of these daughter product emissions depends on the state of equilibrium with 

the Th-232 parent. 

Beta exposures were also possible from radioactive silver research and activities at Horizons, with 

energies ranging from 21.83 keV to 1.20 MeV. 

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5.3.3	 Neutron 

Based on the radioactive materials present on the Horizons site, no source of neutron exposures would 

result from the operations performed. Therefore, further discussion or evaluation of neutron 

exposures will not be included in this evaluation. 

5.3.4 Photon 

Photons from uranium are primarily from the Th-234 daughter of U-238 and are in the energy range 

of 30 - 250 KeV. There are higher-energy photons, up to 1.00 MeV, from another U-238 daughter, 

Pa-234m, but the abundance of these photons is less than 1%. Th-232 itself has no photons; however, 

many of the daughter radionuclides in the natural thorium decay series do emit photons. These 

photons have an energy range up to a maximum of 2.61 MeV (Radiological Health, 1970). The 

photon energies associated with radioactive silver range from 116 keV to 657 keV. 

5.3.5 Incidents 

Although there is information on a minor incident included in the documentation available to NIOSH 

for the Horizons site, no incidents of significant dose consequence (i.e., no discrete incidents) 

requiring evaluation were identified. Because personnel external dosimetry information is available 

for the proposed class, and because source term information associated with the potential non-discrete 

incident radionuclide exposures exists, further discussion or evaluation of incident exposures will not 

be included in this evaluation. 

6.0 Summary of Available Monitoring Data for the Class Evaluated 

by NIOSH 

The following represents an overview of the state of the available internal and external monitoring 

data for the Horizons, Inc., class under evaluation. 

6.1 Horizons Internal Monitoring Data 

No urine sampling or whole-body counting was found during any time period evaluated in this report. 

The only available internal monitoring data are from periodic air monitoring conducted in the facility. 

Air samples and wipe samples were taken and analyzed for (alpha) thorium and reported in December 

1954, and again for September 1955. Limited uranium air samples were also taken and reported for 

July 1953. In addition, source term information and associated process and operations information are 

available for the proposed worker class time period. Air monitoring is discussed further in Section 

6.3. 

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6.2 Horizons External Monitoring Data 

External monitoring data were located during the NIOSH data capture efforts. These monitoring data 

include dosimeter results from May 1954 to December 1955 (USAEC, 1954; USAEC, 1955). These 

data provide weekly dosimeter results from May 1954 through June 1955; monthly reports are 

provided for October 1955 through December 1955. Cycle data are also available for the 1954 

Horizons workers (USAEC, 1954; Horizons, 1954; USAEC, 1955). A memo regarding a trip report 

to Horizons in July 1953 states that Horizons management instituted the wearing of film badges 

provided by Tracerlab; however, no film badge data have been located prior to May 1954 (Visit, 

1953). There also appears to be a data gap between mid-May 1955 and October 1955. External dose 

measurements were recorded for beta and gamma exposures. Other than the data identified above, no 

other personnel external monitoring data were identified for the January 1, 1956 through December 

31, 1956 part of the operational period, or for the entire residual radioactivity period. There are data 

from area monitoring performed as a part of the FUSRAP and remediation surveys; these data can be 

used with the available personnel monitoring data to bound doses for the residual radioactivity period, 

as discussed in the dose reconstruction feasibility evaluation in Section 7.0. 

6.3 Horizons Air Sampling Data 

Air sampling was conducted periodically at Horizons. Air samples and wipe samples were taken and 

analyzed for (alpha) thorium and reported in December 1954, and again for September 1955. Limited 

uranium air samples were also taken and reported for July 1953. There is no indication why the 

samples were taken or the method used to count the samples; therefore, these data will not be 

employed in this evaluation. Sampling (general air, breathing zone air, direct, and wipe) was also 

conducted at Horizons by the Health and Safety Laboratory (HASL) in February 1955 with the intent 

of: (1) estimating the daily weighted average exposures of personnel working on the AEC project; (2) 

determining the degree and extent of radioactive contamination of building and equipment; and (3) 

providing a basis for control recommendations where necessary. The methods used to collect and 

count the samples are clearly described in the HASL report and provide the data used to bound 

occupational exposures during the residual period. The HASL results indicated exposures exceeding 

the maximum permissible concentration to thorium relative to the limits prevailing at that time period 

(HASL, 1955). 

During the post-AEC residual period at the former Horizons site, several inspections/evaluations and 

remediation surveys were performed. In 1977, the Oak Ridge National Laboratory (ORNL) 

performed a survey of the former Horizons site at the request of the Energy Research and 

Development Administration (ERDA). The survey included surface contamination and radiation 

surveys as well as thoron (radon-220) progeny airborne concentrations in the former production 

buildings (ORNL, Aug77; ORNL, Feb77; FUSRAP, 1979). The United States Nuclear Regulatory 

Commission (USNRC) also conducted a 1993 inspection of the former Horizons site that included 

radiological surveys of the former production facilities (USNRC, 1993). There were also two 

pre-remediation surveys of the site that included surface contamination evaluations and airborne 

radioactivity surveys (Fluor Daniel, 1994; Koh, 1998). 

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7.0 Feasibility of Dose Reconstruction for the Class Evaluated by 

NIOSH 

The feasibility determinations for the class of employees under evaluation in this report are governed 

by both EEOICPA and 42 C.F.R. § 83.13(c)(1). Under that Act and rule, NIOSH must establish 

whether or not it has access to sufficient information either 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, or to estimate the radiation doses to 

members of the class more precisely than a maximum dose estimate. If NIOSH has access to 

sufficient information for either case, NIOSH would then determine that it would be feasible to 

conduct dose reconstructions. 

In determining feasibility, NIOSH begins by evaluating whether current or completed NIOSH dose 

reconstructions demonstrate the feasibility of estimating with sufficient accuracy the potential 

radiation exposures of the class. If the conclusion is one of infeasibility, NIOSH systematically 

evaluates the sufficiency of different types of monitoring data, process and source or source term data, 

which together or individually might assure that NIOSH can estimate either the maximum doses that 

members of the class might have incurred, or more precise quantities that reflect the variability of 

exposures experienced by groups or individual members of the class as summarized in Section 5.3. 

This approach is discussed in OCAS’s SEC Petition Evaluation Internal Procedures, which are 

available at http://www.cdc.gov/niosh/ocas. The next four major subsections of this Evaluation 

Report examine: 

• The sufficiency and reliability of the available data. (Section 7.1) 

• The feasibility of reconstructing internal radiation doses. (Section 7.2) 

• The feasibility of reconstructing external radiation doses. (Section 7.3) 

• The bases for petition SEC-00094 as submitted by the petitioner. (Section 7.4) 

7.1 Pedigree of Horizons Data 

This subsection answers questions that need to be asked before performing a feasibility evaluation. 

Data Pedigree addresses the background, history, and origin of the data. It requires looking at site 

methodologies that may have changed over time; primary versus secondary data sources and whether 

they match; and whether data are internally consistent. All these issues form the bedrock of the 

researcher’s confidence and later conclusions about the data’s quality, credibility, reliability, 

representativeness, and sufficiency for determining the feasibility of dose reconstruction. The 

feasibility evaluation presupposes that data pedigree issues have been settled. 

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7.1.1 Internal Monitoring Data Review 

NIOSH did not locate any bioassay monitoring data for any period under evaluation. Therefore, an 

internal data sufficiency and pedigree evaluation is not possible for this data type. 

NIOSH has access to some source term information for the thorium, uranium, and silver process 

activities during the operational period (January 1, 1952 through December 31, 1956). The 1985 

FUSRAP report (DOE, 1985) and the 1954 HASL review of operations (HASL, 1955) document the 

operational conditions at the site, the scale-up in electrolytic operations prior to 1954, and the 

radiological conditions that existed prior to the implementation of the HASL corrective actions. The 

HASL report includes an air sample and surface contamination evaluation of the potential internal 

exposure conditions. NIOSH has drawn the following conclusions from its review of the source term 

data in these reports: 

•	 The available thorium and thorium progeny data are not sufficient to support dose reconstruction 

during the operational period. 

•	 The available data are sufficient to support bounding the internal dose for the residual radioactivity 

period. 

The 1985 FUSRAP report supports NIOSH’s view that the available radiological data represent the 

bounding exposure scenarios for the residual period (1957-2006). Not only is it illogical for the 

potential exposures from the residual period to exceed the operational period, but Horizons conducted 

clean-up activities and safety/exposure improvements after the HASL Survey (R&D, 1955). In 

support of this view, NIOSH compared data from the 1977 FUSRAP survey, the 1985 FUSRAP 

report, and the 1993-1995 remediation surveys. The results showed that the 1977 FUSRAP data 

would represent the highest potential radiological exposures during the residual radioactivity period. 

Based on this comparison, NIOSH used the 1977 FUSRAP survey data as a lower-bounding 

condition, and the 1954 HASL Survey operational data (HASL, 1955) as an upper-bounding condition 

for the internal exposure feasibility evaluation of the residual radioactivity period. 

The internal dose reconstruction feasibility evaluations for all periods under evaluation are presented 

in Section 7.2. 

7.1.2 External Monitoring Data Review 

NIOSH has access to the original external dosimetry information and documentation for the period 

from 1954 through 1955 (some gaps in data do exist); this would be during the period of pilot-scale 

operations when thorium activities were performed on a constant basis in contrast to earlier, 

small-scale research and development (DOE, 1985; Service, 1954; Visit, 1953; Final Report 1954; 

Fused Salt, 1955; Report, 1954; 1Q Progress Report, 1952; 5Q Progress Report, 1953; 6Q Progress 

Report, 1953). In addition, NIOSH has source term information for the thorium, uranium, and silver 

process activities. The original external dosimetry data provide actual doses recorded by individuals 

for a specific time period (exchange frequencies were weekly or monthly depending on the time 

period). Only positive results were reported; all others are “X-ed” out. It is assumed that the “X” 

represents an actual datum that is below the limits of detection for the film. 

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Information included in the 1985 FUSRAP report (DOE, 1985) and the 1954 HASL review of 

operations (HASL, 1955) documents the conditions at Horizons during the operational period. These 

documents discuss the scale-up in electrolytic operations over the early years and the radiological 

conditions that existed prior to the implementation of the HASL corrective actions. The 1954 HASL 

Report names individuals who, based upon the report, would have a potential for external radiation 

exposure (i.e., furnace operator, metal chipping, and washing). NIOSH has identified recorded 

external doses for all but one of the individuals named in the report. In addition, many other 

individuals not named in the report also have recorded external doses. 

In light of the conclusions reached regarding internal dose reconstruction feasibility for the 

operational period (see Sections 7.1.1 and 7.2.3), NIOSH did not perform an extensive external data 

sufficiency and pedigree evaluation for the external data associated with Horizons operations. 

Although no specific conclusions were drawn about the external data during the operational period 

and the associated dose reconstruction feasibility, NIOSH has drawn following general conclusions: 

•	 The external data and source term information will be used for partial dose reconstructions for the 

operational period. 

•	 The external data are sufficient to support bounding the external dose for the residual radioactivity 

period. 

Using the data from the 1955 HASL survey (HASL, 1955) and the 1977 FUSRAP survey (ORNL, 

Aug77), it will be possible to interpolate the potential external exposure between the time of the two 

surveys. As discussed in Section 7.1.1, the 1977 FUSRAP survey data represent the highest potential 

radiological exposures during the residual radioactivity period when compared to the 1985 FUSRAP 

and 1993-1995 remediation survey data). Therefore, the 1977 FUSRAP survey data serve as a 

lower-bounding condition, and the 1954 HASL survey data (HASL, 1955) serve as the 

upper-bounding condition for the external exposure feasibility evaluation for the residual radioactivity 

period. 

The external dose reconstruction feasibility evaluations for all periods under evaluation are presented 

in Section 7.3. 

7.2 Internal Radiation Doses at Horizons 

The principal source of internal radiation doses for members of the proposed class was exposures to 

thorium (as well as thorium daughter products and thoron), uranium, and radioactive silver (FUSRAP, 

1985; Mataich, 1954). A discussion of the feasibility of internal dose reconstruction for the proposed 

class is provided below. 

7.2.1 Sources of Internal Radiation Dose and Related Monitoring Data 

The following subsections summarize the extent and limitations of information available for 

reconstructing the internal doses of members of the proposed class. As previously discussed, no 

in vivo or in vitro bioassay data are available for the Horizons proposed worker class. Therefore, the 

internal dose feasibility evaluation is based solely on air monitoring, source term, and process 

information. 

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7.2.1.1 Operations-Related Internal Dose 

Internal exposures during the Horizons operational period (January 1, 1952 through December 31, 

1956) included exposures related to the high-temperature electrolytic operations, laboratory analysis 

and testing, and related activities. Exposures were possible in the direct vicinity of the 

operations/activities, and also from ambient environmental exposures (in the immediately surrounding 

work areas). The analyses of potential personnel exposures for this time period are described below. 

Airborne Levels 

The 1954 HASL report includes an airborne monitoring and surface contamination evaluation 

conducted during the stage of Horizons operations at which radiological controls were insufficient for 

maintaining personnel occupational internal exposures below maximum permissible exposure levels 

in effect at that time (HASL, 1955). Descriptions of the operations evaluated during the period of the 

HASL review discussed activities that were likely to produce significant personnel internal exposures 

(i.e., open area radioactive material chipping and crushing, sweeping of contaminated surfaces, and 

hand-scooping of materials). The air sampling data (alpha radiation counts of general area and 

personnel breathing zone) are representative of elevated exposure scenarios for such operations in 

both buildings associated with the high-temperature electrolytic processes during that time. However, 

there is not enough evidence to support that these data provide bounding values for the operational 

period. Therefore, these data cannot be used to perform dose reconstructions for internal exposures at 

Horizons. NIOSH concludes that the HASL data are not appropriate for dose reconstruction during 

the operational period for the following reasons: 

1.	 Although the HASL study was performed during Horizons pilot-scale operations when more 

radioactive material was present at (as opposed to R&D activities), NIOSH has little information 

about the initial process, process changes, and process controls implemented during the R&D 

period that would allow NIOSH to conclude that exposure levels were likely lower during the 

R&D period. 

2.	 Based on its review and analysis of the electrolytic process, NIOSH has concluded that the high 

temperature associated with the thorium electrolytic operations would have likely resulted in the 

release of radium (Ra-228 and Ra-224), thoron (Rn-220), and associated radon progeny (Bi-212 

and Pb-212). This would have resulted in significant localized internal exposure conditions in the 

electrolytic process equipment. The delay period between the collection and counting of the 

HASL air sample data (24 to 34 days), and the associated half-lives of the radium and thoron and 

associated progeny, directly impact NIOSH’s ability to bound the radium internal exposures or to 

reconstruct with sufficient accuracy the internal exposures from these radionuclides. 

Information associated with Horizons silver operations discusses the controls that were in place for the 

research and plating work performed with the radioactive silver (Mataich, 1954; DOE, 1985). The 

silver operations were performed after the HASL site evaluation and were performed with radiological 

controls (i.e., within ventilation hoods) to prevent personnel exposures (Mataich, 1954). Because 

NIOSH had already determined that the internal dose cannot be reconstructed during the operational 

period, NIOSH did not make a feasibility determination with respect to silver exposures. NIOSH 

currently has no personnel monitoring data for silver exposures. If monitoring data become available, 

NIOSH will evaluate the use of these data for partial dose reconstructions. 

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7.2.1.2 Residual Radioactivity-Related Internal Dose 

Ambient environmental dose is the primary source of internal dose for the residual radioactivity 

period under evaluation in this report (January 1, 1957 through July 31, 2006). The internal dose for 

this period can be estimated (as described below) based on the data available from the 1955 HASL 

survey and the 1977 post-operation remediation survey; each dataset provides values that represent the 

maximum exposure points at the time of the survey (HASL, 1955; Survey, 1955). 

After AEC-related operations ceased at Horizons in 1956, the contracts and associated radioactive 

material licenses were terminated (FUSRAP, 1985; DOE, 1985). No AEC-related thorium or uranium 

high-temperature operations occurred during the residual radioactivity period, thus eliminating any 

localized source of internal exposures from uranium or thorium (or its progeny). Cessation of 

AEC-related high-temperature operations also eliminated the Ra-224 and thoron exposures produced 

these processes. The short half-lives of radium, thoron, and its associated progeny contributed to this 

elimination. Ra-228 exposures can be bounded using FUSRAP report data and Ra-228 decay 

information. 

Considering the above information, NIOSH assumes that the 1955 HASL data are appropriate for 

bounding internal dose reconstruction during the residual period for the following reasons: (1) the 

HASL study was performed toward the end of operations when more radioactive material was present 

at Horizons; (2) the study was specifically performed as an assessment of workers’ exposure; (3) 

conditions improved after the study because operations were suspended while decontamination efforts 

were performed (R&D, 1955); and (4) of the limited data available during the operational period, the 

HASL study data provide the highest level of confidence that the samples were collected and analyzed 

appropriately. Therefore, the radiological conditions at any point during the residual period could not 

have been any worse than described in that study. 

Compared to the 1993, 1994, or 1998 survey data, the 1977 FUSRAP data represent the highest 

potential intakes associated with the residual radioactivity (post-operational) period. This outcome 

supports the application of the 1977 FUSRAP data as the lower bound in the evaluation of internal 

dose for the residual radioactivity period. 

7.2.2 Internal Dose Reconstruction 

The following subsections present the general dose reconstruction methodology for determining 

whether doses can be bounded or reconstructed with sufficient accuracy for the proposed class of 

Horizons workers. 

7.2.2.1 Operational Period 

The Horizons operational period will not be discussed because NIOSH has already determined that 

dose reconstruction for the operational period is infeasible. 

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7.2.2.2 Residual Period 

Based on the available Horizons process information, source term information, air sample data for the 

operational period, and pre-remediation survey data over multiple periods, NIOSH has the necessary 

data to support bounding internal exposures for uranium, thorium, and thorium progeny during the 

residual period. Because radioactive operations were terminated at the end of the operational period, 

the residual period doses can be bounded through the application of the operational data, although this 

would result in over-estimates for residual period exposures and doses. The methods described in this 

section provide a sufficiently accurate estimation of the residual radioactivity period doses at Horizons 

(January 1, 1957 through July 31, 2006). 

Based on the elimination of the exposure source after operations ceased, and the half-life and decay of 

any residual contamination, no exposure evaluation of the radioactive silver was required or 

performed for the residual period. 

Thorium and Radium Internal Dose Reconstruction during the Residual Period 

Thorium and radium intakes during the residual period can be bounded using data from the 1955 

HASL survey to represent the upper bound air activity at the start of the residual period (January 1, 

1957), and data from the 1977 FUSRAP report (Survey, 1955) to represent the air activity in 1977. 

The information provided by HASL, and from the Quarterly Report to the AEC immediately after the 

HASL report was issued (R&D, 1955)indicating that work had been temporarily suspended for cleanup and implementation of the HASL recommendations, demonstrates that the data provided by HASL 

are bounding. Since contamination levels documented in the 1993 pre-remediation survey were 

similar to those documented in 1977, and lower than those identified by the HASL report, the 1977 air 

activity is assumed to be representative of air concentrations during the 1978-1993 period as well. 

With cessation of operational activities (and any associated acute localized releases of radioactivity), 

air concentrations would be driven by re-suspension of previously- deposited materials. Resuspension of contamination within the facility is assumed to decrease according to an exponential 

model (Healy, 1971; Sehmel, 1980; Till, 1983), as described below. 

•	 1957 Air Concentration: HASL conducted a thorough airborne radioactivity survey during the end 

of the operational period. This survey included both breathing zone and general area air samples. 

A bounding estimate of airborne radioactivity during the start of the residual period was calculated 

using the 95th percentile of the general area air samples collected in the HASL study (64 samples 

total). Samples that were labeled as breathing zone, or were clearly associated with operational 

activities, were excluded from this dataset. The general area room air concentrations included one 

location that was 16 times higher than all the others and therefore excluded because it was clearly 

impacted by operational activities. The resultant air concentration was 12 pCi/m3

 resulting in an 

intake of 77 pCi/d (averaged over one year). Since the HASL air sample data were total alpha, 

this intake quantity represents both Th-232 and Th-228 (i.e., Th-232 + Th-228). 

•	 1977 Air Concentration: Total gross alpha surface contamination (fixed + removable) and 

removable alpha surface contamination measurements are documented in the 1977 FUSRAP 

survey. The 1977 air concentration was calculated by applying a re-suspension factor of 1E-6 to 

the 95th percentile of the total alpha surface contamination values collected in building B (200 

measurements) and a re-suspension factor of 1E-4 to the maximum removable activity in the 

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overhead areas of Building B. These two components were summed. The resultant intake 

quantity was 1.6 pCi/m3

 resulting in an intake of 10 pCi/d (averaged over one year). This value 

greatly exceeds the airborne alpha concentrations reported in the 1977 FUSRAP report based on a 

limited survey (0.0011 pCi/m3

). 

Building B values were used because they were higher than Building C and because it was likely 

impossible to estimate the time spent within each building. An evaluation of the suitability of the 

1E-6 re-suspension factor was performed using the RESRAD Build code (RESRAD, 2003). 

Probabilistic distributions for sensitive parameters (deposition velocity, re-suspension rate, air 

exchange rate, air release fraction, removable fraction and source lifetime) were selected (USNRC 

2000). The resultant re-suspension factor at the 95th percentile was 3E-7. 

•	 Exponential Model: The 1957 and 1977 daily intake rates were used to estimate the annual intake 

from the following equation: 

−λ*t It = I 0 

*e 

where: 

It = daily intake rate at time t 

t = time (days) since January 1, 1957 

I0 = daily intake on January 1, 1957 

λ = exponential constant 

The constant was determined to be 0.00028 day-1 . 

•	 Radium 228 Intake: Because of the potential for elevated levels of Ra-228 due to high-temperature 

operations, intakes were adjusted to account for the potential disequilibrium conditions. Since 

Th-232 and Ra-228 were shown to be in equilibrium in 1977 (FUSRAP, 1979), the maximum 

Ra-228 concentration in 1957 can be determined based on the radiological half-life of Ra-228 

(6.9 yr) and setting the Ra-228 intake quantity equal to the thorium value in 1977. 

Table 7-1 shows the resulting intake quantities for the period 1957 through 1977. No further 

reduction in intake quantity is assumed after 1977 based on the 1993 facility survey that showed 

contamination levels in 1993 that were similar but lower to those in 1977. Using the 1977 intake 

quantities provides a conservative approach to dose reconstruction post-1977. Corresponding 

ingestion intakes (OCAS-TIB-009) are shown in Table 7-2. 

Table 7-1: Thorium and Ra-228 Inhalation 

(pCi/d) (Table 7-1 spans two pages) 

Year Th-232 + Th-228 Ra-228 

1957 77 288 

1958 70 236 

1959 63 193 

1960 57 158 

1961 52 129 

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Table 7-1: Thorium and Ra-228 Inhalation 

(pCi/d) (Table 7-1 spans two pages) 

Year Th-232 + Th-228 Ra-228 

1962 47 105 

1963 42 86 

1964 38 70 

1965 34 58 

1966 31 47 

1967 28 39 

1968 25 31 

1969 23 26 

1970 21 21 

1971 19 17 

1972 17 14 

1973 15 12 

1974 14 9 

1975 13 8 

1976 11 6 

1977 10 5 

> 1977 10 5 

Table 7-2: Thorium and Ra-228 Ingestion 

(pCi/d) 

Year Th-232 + Th-228 Ra-228 

1957 2.4 8.8 

1958 2.1 7.2 

1959 1.9 5.9 

1960 1.7 4.8 

1961 1.6 3.9 

1962 1.4 3.2 

1963 1.3 2.6 

1964 1.2 2.1 

1965 1.0 1.8 

1966 0.9 1.4 

1967 0.9 1.2 

1968 0.8 1.0 

1969 0.7 0.8 

1970 0.6 0.6 

1971 0.6 0.5 

1972 0.5 0.4 

1973 0.5 0.3 

1974 0.4 0.3 

1975 0.4 0.2 

1976 0.3 0.2 

1977 0.3 0.2 

> 1977 0.3 0.2 

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SEC-00094 03-12-08 Horizons, Inc. 

Thorium Progeny Internal Dose Reconstruction 

During the 1977 FUSRAP survey, evidence of thoron emanation into the facility was identified 

(elevated alpha levels at floor drains and near cracks where floors and walls intersect). A series of 

measurements indicated Pb-212 levels ranging from 0.005 pCi/l to 0.49 pCi/l. Measured 

concentrations of Bi-212 ranged from non-detectable to 0.19 pCi/l. A bounding estimate of the 

Pb-212 concentrations in 1977 was made using the 95th percentile (0.38 pCi/l). The Rn-220 (thoron) 

concentration was assumed to be equal to the Pb-212 concentration. Since the thoron concentration 

would be expected to track with the total thorium inventory, the 1957 through 1976 concentrations 

were normalized to the thorium concentration in each respective year. Resultant values in units of 

working level month (Rn-220) are shown in Table 7-3. 

Table 7-3: Thoron (Rn-220) 

Year Rn-220 (WLM) 

1957 6.2E+00 

1958 5.5E+00 

1959 4.9E+00 

1960 4.4E+00 

1961 3.9E+00 

1962 3.5E+00 

1963 3.1E+00 

1964 2.7E+00 

1965 2.4E+00 

1966 2.2E+00 

1967 1.9E+00 

1968 1.7E+00 

1969 1.5E+00 

1970 1.3E+00 

1971 1.2E+00 

1972 1.1E+00 

1973 9.4E-01 

1974 8.4E-01 

1975 7.5E-01 

1976 6.6E-01 

1977 6.0E-01 

>1977 6.0E-01 

7.2.3 Internal Dose Reconstruction Feasibility Conclusion 

NIOSH has established that it cannot estimate with sufficient accuracy the internal exposures during 

the operational period (January 1, 1952 through December 31, 1956). However, NIOSH can bound 

the residual uranium, thorium, and thorium progeny exposures and associated doses for the residual 

radioactivity period (January 1, 1957 through July 31, 2006). 

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7.3 External Radiation Doses at Horizons 

The principal source of external radiation doses for members of the proposed class was exposures to 

thorium, uranium, and radioactive silver (FUSRAP, 1985; Mataich, 1954). A discussion of the 

feasibility of the external dose reconstruction for the proposed class is provided below. 

7.3.1 Sources of External Radiation Dose and Related Monitoring Data 

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related external doses of members of the proposed class. 

7.3.1.1 Operations-Related External Dose 

External exposures during the Horizons operational period (January 1, 1952 through December 31, 

1956) included exposures from thorium and uranium as well as Ag-110m during high-temperature 

electrolytic operations, laboratory analysis and testing, and related activities. Exposures were possible 

in the direct vicinity of the operations/activities, and also from ambient environmental exposures (in 

the immediately surrounding work areas). The analyses of the potential personnel exposures for this 

period are described below. 

Dosimeter Results for Horizons 

In addition to having the original personnel external dosimetry information and documentation for the 

period 1954-55 (some data gaps do exist), NIOSH has source term information for the thorium, 

uranium, and silver process activities. Beta and photon external exposures from these radioactive 

materials did occur as a result of the work at Horizons. 

7.3.1.2 Residual Radioactivity Period-Related External Dose 

Ambient environmental dose is the primary source of external dose for the residual radioactivity 

period under evaluation in this report (January 1, 1957 through July 31, 2006). The external dose for 

this period can be estimated (as described below) based on the data available from the 1955 HASL 

survey and the 1977 post-operation remediation survey; each dataset provides values that represent the 

maximum exposure points at the time of the survey (HASL, 1955; Survey, 1955). 

7.3.2 Horizons Occupational X-Ray Examinations 

No information is available on occupational medical X-ray examinations for Horizons workers during 

any covered timeframe. Information obtained from a former employee indicated that pre-employment 

physicals were required to work at Horizons, but there was no recollection if a chest X-ray was part of 

the exam. For the purpose of partial dose reconstructions, a single PA radiographic chest X-ray will 

be assumed to have been required during each pre-employment, annual, and termination physical at 

Horizons. The assignment of X-ray dose is in accordance with ORAUT-OTIB-0006. 

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7.3.3 External Dose Reconstruction 

By December 21, 2007, four EEOICPA claims meeting the proposed class definition being evaluated 

in this report had been submitted to NIOSH. Of those four claims, NIOSH has completed dose 

reconstructions for none of these claims. 

There is an established protocol for assessing external exposure when performing dose 

reconstructions. These protocol steps are discussed in the following subsections for both the 

operational and residual radioactivity periods. 

• Photon/Electron Dose (Monitored and Unmonitored) 

• Medical X-ray 

7.3.3.1 Photon/Electron Dose during the Operational Period 

The external dose for the operational period will be evaluated based on the available personnel 

dosimetry data for the period. The available external dosimetry data represent the maximally-exposed 

worker and exposure scenarios for the period. These data have been used to support NIOSH’s 

evaluation of the ability to bound external doses, as described in the following subsections. 

Monitored Individuals 

NIOSH will use the actual, original dosimetry documentation to reconstruct dose for those members 

of the proposed class for whom NIOSH has these data. This is the preferred data type and dose 

reconstruction method specified by the dose reconstruction program. When an individual is 

unmonitored (or data are unavailable, missing, or otherwise unavailable), the unmonitored approach 

can be used as a bounding approach for external dose reconstruction. 

Unmonitored Individuals 

Results of film badges worn from May 31, 1954 through December 1955 (Horizons, 1954; USAEC, 

1955) are summarized in Tables 7-4 and 7-5 and can be used either to fill in gaps between periods 

where monitoring data are available, or for unmonitored workers. Results from weekly badge cycles 

(May 1954 – June 13, 1955) and monthly cycles (September 1955 – December 1955) were analyzed 

separately. Positive badge results were fit to a lognormal distribution. Missed dose was based on a 

lognormal distribution with a geometric mean equal to the dosimeter LLD/2 and 95th percentile of the 

LLD (resulting GSD of 1.52). The annual dose quantities were determined by weighing measured and 

missed dose distribution by the fraction of cycles with measured and missed dose, respectively. A 

dosimeter LLD of 40 mR was used based on the typical response for film dosimetry (NRC, 1989). 

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Table 7-4: Horizons Film Badge Gamma Radiation Results 

(mR/hr or mrad/hr, as applicable) 

Period 

DD DM 

Total 

Dd+Dm 

GM GSD GM GSD GM GSD 

5/31/1954 - 6/13/1955 (weekly data) 189 1.71 961 1.52 1149 1.71 

September 1955 - December 1955 (monthly data) 863 1.54 116 1.52 979 1.54 

DD and DM are dosimeter dose and missed dose, respectively, as defined in OCAS-IG-001. 

Table 7-5: Horizons Film Badge Beta Radiation Results 

(mR/hr or mrad/hr, as applicable) 

Period 

DD DM 

Total 

Dd+Dm 

GM GSD GM GSD GM GSD 

5/31/1954 - 6/13/1955 (weekly data) 29 1.96 1240 1.52 1270 1.96 

September 1955 - December 1955 (monthly data) Analysis not performed, reported values were gamma only 

DD and DM are dosimeter dose and missed dose, respectively, as defined in OCAS-IG-001. 

7.3.3.2 Photon/Electron Dose during the Residual Period 

Dose rate measurements were performed in 1955 (HASL, 1955) during the HASL survey, and in 1977 

(Survey, 1955) during the FUSRAP survey. These results were fit to a lognormal distribution shown 

in Table 7-6. Note that for the 1955 data, only general area dose rate values (i.e., not associated with 

process equipment or material) were used in the analysis. Annualized values (based on a 2000-hr 

work year) are shown in Table 7-7 and may be used to bound external exposure during the residual 

period. Note that the 1955 values are assumed to remain constant until 1977, at which time the use of 

1977 values are recommended. 

Table 7-6: Summary of Available Data 

(mR/hr or mrad/hr, as applicable) 

Type 1955 HASL Report 1977 Fusrap Report 

GM GSD GM GSD 

Gamma 0.194 2.60 0.013 1.75 

Beta 0.053 2.01 0.045 2.13 

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Table 7-7: Recommended Dose Values 

(R/yr) 

Type 1957 - 1976 1977 onward 

GM GSD GM GSD 

Gamma 0.388 2.60 0.025 1.75 

Beta 0.106 2.01 0.091 2.13 

7.3.3.3 Medical X-ray 

A single PA radiographic chest X-ray is assumed to have been required during each pre-employment, 

annual, and termination physical at Horizons. Although no records are identified indicating that 

occupational medical X-rays were required of Horizons employees, for the purpose of partial dose 

reconstructions during the operational period (before January 1, 1957), X-ray exams will be assumed 

to have been required. This assumption provides a level of conservatism to the dose reconstruction. 

Organ doses from PA chest X-ray for all time periods are available in ORAUT-OTIB-0006. NIOSH 

believes that by using this methodology, occupational medical X-ray doses can be reconstructed. 

7.3.4 External Dose Reconstruction Feasibility Conclusion 

Using actual data or co-worker data and the methodologies described, NIOSH has established that it 

can estimate the external exposures associated with radioactive operations during the operational 

period and bound external exposures for the residual period. NIOSH believes that the data identified 

during the operational period (pilot-scale) are conservative relative to the earlier R&D period and the 

later post-operations period. Beginning in 1957, Horizons documentation discusses the clean-up 

effort undertaken in response to the HASL survey; this clean-up would be expected to result in lower 

exposure potential (USAEC, 1954; Horizons, 1954; USAEC, 1955; Film, 1955; Monthly, 1955). 

7.4 Evaluation of Petition Basis for SEC-00094 

The petition basis provided in SEC-00094 stated that members of the proposed class incurred 

unmonitored radiation exposures at Horizons (through lack of personal or area monitoring) and doses 

during the operations period (January 1, 1944 through December 31, 1956) and residual period 

(January 1, 1957 through July 31, 2006). The following topic was detailed in petition SEC-00094. 

Italicized statements are from the petition; the comments that follow are from NIOSH. 

SEC-00094: I have no knowledge of any monitoring data for Horizons, Inc 

Personal monitoring, area monitoring, or co-worker monitoring are not always required in order to 

develop an exposure model for a given facility. However, if these monitoring data are not available, 

NIOSH must have access to source term information and detailed process information in order to 

develop a sufficiently accurate exposure model. NIOSH has determined that it does not have adequate 

internal monitoring data for members of the proposed class, nor does it have enough source term or 

process information applicable to the class to develop a sufficiently accurate model for dose 

reconstruction for these exposures during the associated time period. However, as discussed in 

Section 5.0, NIOSH has discovered no information regarding any operations or activities at the 

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SEC-00094 03-12-08 Horizons, Inc. 

Horizons site in Cleveland prior to licensing on September 4, 1947. Furthermore, NIOSH has found 

no evidence that radiological material was on site prior to 1952; therefore, the operations period is 

considered to be January 1, 1952 through December 31, 1956. 

7.5 Summary of Feasibility Findings for Petition SEC-00094 

This report evaluates the feasibility for completing dose reconstructions for employees at Horizons, 

Inc., from January 1, 1944 through December 31, 1956, and for the residual period from January 1, 

1957 through July 31, 2006. As discussed in Section 5.0, NIOSH has discovered no information for 

any radiological operations or activities at the Horizons site in Cleveland prior to January 1, 1952; 

therefore, the operations period is considered to be January 1, 1952 through December 31, 1956. 

NIOSH found that the available monitoring records, process descriptions, and source term data are not 

sufficient to complete dose reconstructions for the class of employees who worked during the 

operational period under evaluation. 

Table 7-8 summarizes the results of the feasibility findings at Horizons for each exposure source 

during the time periods from January 1, 1952 through December 31, 1956 and from January 1, 1957 

through July 31, 2006. 

Table 7-8: Summary of Feasibility Findings for SEC-00094 

Operations Period from January 1, 1952 through December 31, 1956 

and Residual Period from January 1, 1957 through July 31, 2006 

Source of Exposure Reconstruction 

Feasible 

Reconstruction 

Not Feasible 

Internal (Operational Period: January 1, 1952 through Dec 31, 1956)1 X 

Internal (Residual Period: Jan 1, 1957 through Jul 31, 2006)1, 3 X --- 

External (Operational and Residual Periods)

 - Gamma X --- 

 - Beta X ---

 - Occupational Medical X-ray X --- 

1

 Internal includes an evaluation of airborne dust and source term data. 

2

 Includes radium (Ra-228 and Ra-224), thoron (Rn-220), and associated radon progeny (Bi-212 and Pb-212). 

3

 Ag-110m is not considered during the residual period. 

As of December 21, 2007, a total of four claims have been submitted to NIOSH for individuals who 

worked at Horizons, Inc. and are covered by the proposed class definition evaluated in this report. 

Dose reconstructions have been completed for none of these individuals. 

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8.0 Evaluation of Health Endangerment for Petition SEC-00094 

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by both EEOICPA and 42 C.F.R. § 83.13(c)(3). Under these requirements, if it is not 

feasible to estimate with sufficient accuracy radiation doses for members of the class, NIOSH must 

also determine that there is a reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. Section 83.13 requires NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If 

the occurrence of such an exceptionally high-level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those workers who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

Based on available data, knowledge of source terms and activities, and surveys conducted during both 

the operational and residual periods, NIOSH’s evaluation determined that it is not feasible to estimate 

internal radiation dose for members of the proposed class with sufficient accuracy during the 

operational period. Modification of the class definition regarding health endangerment and minimum 

required employment periods, therefore, is required. 

9.0 NIOSH-Proposed Class for Petition SEC-00094 

Based on its research, NIOSH modified the petitioner-requested class to define a single class of 

employees for which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSHproposed class includes all AWE employees who worked at Horizons, Inc., for a number of work days 

aggregating at least 250 work days from January 1, 1952 through December 31, 1956, or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. The class was modified because collected data are not sufficient to support 

reconstruction of internal radiation doses with sufficient accuracy during the operational period; 

however, collected data are sufficient to support reconstruction of doses with sufficient accuracy for 

the residual period. 

NIOSH has carefully reviewed all material sent in by the petitioner, including the specific assertions 

stated in the petition, and has responded herein (see Section 7.4). NIOSH has also reviewed available 

technical resources and many other references, including the Site Research Database (SRDB), for 

information relevant to SEC-00094. In addition, NIOSH reviewed its NOCTS dose reconstruction 

database to identify EEOICPA-related dose reconstructions that might provide information relevant to 

the petition evaluation. 

These actions are based on existing, approved NIOSH processes used in dose reconstruction for 

claims under EEOICPA. NIOSH’s guiding principle in conducting these dose reconstructions is to 

ensure that the assumptions used are fair, consistent, and well-grounded in the best available science. 

Simultaneously, uncertainties in the science and data must be handled to the advantage, rather than to 

the detriment, of the petitioners. When adequate personal dose monitoring information is not 

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available, or is very limited, NIOSH may use the highest reasonably possible radiation dose, based on 

reliable science, documented experience, and relevant data to determine the feasibility of 

reconstructing the dose of an SEC petition class. NIOSH contends that it has complied with these 

standards of performance in determining that it would not be feasible to reconstruct the dose for the 

class proposed in this petition during the operational period, but that it would be feasible to 

reconstruct dose for the residual period. 

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SEC-00094 03-12-08 Horizons, Inc. 

10.0 References 

42 C.F.R. pt. 81, Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol. 67, No. 85/Thursday, p 22,296; May 2, 2002; SRDB Ref ID: 19391 

42 C.F.R. pt. 82, Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 

19392 

42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the Special 

Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 

2000; Final Rule; May 28, 2004; SRDB Ref ID: 22001 

42 U.S.C. §§ 7384-7385 [EEOICPA], Energy Employees Occupational Illness Compensation 

Program Act of 2000, as amended 

Battelle-TIB-5000, Default Assumptions and Methods for Atomic Weapons Employer Dose 

Reconstructions, Rev. 00; April 7, 2007; SRBD Ref ID: 32016 

Battelle-TBD-6000, Site Profiles for Atomic Weapons Employers that Worked Uranium and Thorium, 

Rev. F0; December 13, 2006; SRDB Ref ID: 30671 

Battelle-TBD-6001, Site Profiles for Atomic Weapons Employers that Refined Uranium and Thorium, 

Rev. F0; December 13, 2006; SRDB Ref ID: 30673 

OCAS-IG-001, External Dose Reconstruction Implementation Guideline, Rev. 3, National Institute 

for Occupational Safety and Health (NIOSH); Cincinnati, Ohio; November 21, 2007; SRDB Ref ID: 

38864 

OCAS-PR-004, Internal Procedures for the Evaluation of Special Exposure Cohort Petitions, Rev. 0, 

National Institute for Occupational Safety and Health (NIOSH); Cincinnati, Ohio; September 23, 

2004; SRDB Ref ID: 32022 

OCAS-TIB-009, Estimation of Ingestion Intakes, Rev. 0, National Institute for Occupational Safety 

and Health (NIOSH); Cincinnati, Ohio; April 13, 2004; SRDB Ref ID: 22397 

OCAS-TIB-0011, Lung Dose Conversion Factor For Thoron WLM, Rev 2; January 13, 2006; SRDB 

Ref ID: 22409 

ORAUT-OTIB-0006, Dose Reconstruction From Occupationally Related X-Ray Procedures, Rev 03 

PC-1; December 21, 2005; SRDB Ref ID: 20220 

ORAUT-PROC-0061, Occupational X-Ray Dose Reconstruction for DOE Sites, Rev 00; July 21, 

2006; SRDB Ref ID: 29987 

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1Q Progress Report, 1952, Investigations for the Production of Thorium Metal; Technical Progress 

Report, First Quarter, May 1 to July 31, 1952; Horizons, Inc., Cleveland, Ohio, for the U.S. Atomic 

Energy Commission; July 31, 1952; SRDB Ref ID: 38073 

5Q Progress Report, 1953, Investigation for the Production of Thorium Metal; Technical Progress 

Report – Fifth Quarter; M. Merlub-Sobel (Horizons Incorporated, Cleveland, Ohio) for the U.S. 

Atomic Energy Commission; December 17, 1953; SRDB Ref ID: 38037 

6Q Progress Report, 1953, Investigations for the Production of Thorium Metal; Technical Progress 

Report – Sixth Quarter; J. C. Bleiweiss (Horizons Incorporated, Cleveland, Ohio) for the U.S. Atomic 

Energy Commission; December 1, 1953; SRDB Ref ID: 38066 

Affidavit, 2007, Affidavit from [Survivor Name redacted]; November 26, 2007; OSA Ref ID: 38320 

Bloch, 1955; Horizons Proposal for Research on Electrolytic Production of Uranium, proposal from 

E. J. Bloch to S. R. Sapirie; July 26, 1955; SRDB Ref ID: 38162. 

DOE, 1985, Authority Review of the Former Horizons, Inc., Site, Cleveland, Ohio, letter from the 

Department of Energy to R. C. Jackson (President, Lamotite, Inc.); December 1985; SRDB Ref ID: 

11008, pdf pp. 152 and 193 

Film, 1955, Film Badge Report, Horizons Inc; December 1955; SRDB Ref ID: 16926 

Final Report, 1954, Investigations for the Production of Thorium Metal; Final Report – May 1, 1952 

to April 30, 1954; B. C. Raynes, J. C. Bleiweiss, M. E. Sibert, M. A. Steinberg (Horizons 

Incorporated, Cleveland, Ohio) for the U.S. Atomic Energy Commission;; November 1, 1954; SRDB 

Ref ID: 38032 

Fisher, 1956; Research and Development in the Field of Thorium Chemistry and Metallurgy, Volume 

I, Preparation of Electrolytic Cell Feed for Production of Thorium Metal – Final Report; Charles E. 

Fisher and James L. Wyatt; June 30, 1956; SRDB Ref ID: 11008, pdf p. 206 

Fluor Daniel, 1994; Radiological Survey Report of the Lamotite Inc. Facility; report prepared by Fluor 

Daniel Environmental Services; February 3, 1994; SRDB Ref ID: 38129 

Fused Salt, 1955, The Preparation of Thorium Metal Powder by Fused Salt Electrochemical 

Techniques, J. L. Wyatt (Horizons, Inc., Cleveland) for the U.S. Atomic Energy Commission; August 

3, 1955; SRDB Ref ID: 38051 

FUSRAP, 1979; Formerly Utilized MED/AEC Sites Remedial Action Program – Radiological Survey 

of the Former Horizons Inc., Metal Handling Facility, Cleveland, Ohio; U.S. Department of Energy; 

Formerly Utilized Sites Remedial Action Program; February 1979; SRDB Ref ID: 36331 

FUSRAP, 1985; Authority Review for the Former Horizons, Inc. Site; U.S. Department of Energy; 

Formerly Utilized Sites Remedial Action Program; December 2, 1985; SRDB Ref ID: 11008, pdf p. 

38 of 41 

154 
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HASL, 1955; Occupational Exposure to Airborne Contaminants at Horizons, Inc.; U.S. Atomic 

Energy Commission, Health and Safety Laboratory; February 21, 1955 (survey performed December 

1-3, 1954); SRDB Ref ID: 16125 

Healy, 1971, Surface Contamination: Decision Levels, J.W. Healy; LA-4558-MS; Los Alamos 

Scientific Laboratory; Los Alamos, New Mexico; 1971; SRDB Ref ID: Not yet in SRDB 

Horizons, 1954, Film Badge Cycle Reports for Horizons, Inc., for 1954; SRDB Ref ID: 10596 

Koh, 1998; Site Remediation Plan for the Horizons Remediation Project Site, Cleveland, Ohio, 

performed by B. Koh & Associates; report dated March 1998 (survey performed in 1997 and 1998); 

SRDB Ref ID: 38218. 

License, 1993, Former Horizons Incorporated Site, Cleveland, Ohio, letter to J. A. Grobe (Chief, Fuel 

Cycle and Decommissioning Branch, Nuclear Regulatory Commission) from S. J. Petras (Counsel for 

Vorys, Sater, Seymour and Pease); October 12, 1993; SRDB Ref ID: 38198 

Mataich, 1954; Letter from Peter F. Mataich (Horizons Research Associate) to USAEC Isotopes 

Division to discuss and further explain the research and studies to be performed with radioactive 

silver; July 12, 1954; SRDB Ref ID: 11008 (page 58 of 357). 

Maybaum, 1953; Report from Paul S. Maybaum Jr. (Laboratory Superintendent) to Manager of 

Operations, USAEC (attn: Mr. R. L. Kirk (Director Production Division)); Semi-annual report for 

Research Issuance Material; June 25, 1953; SRDB Ref ID: 11008 (page 239 of 357). 

Maybaum, 1958; Three letters from Paul S. Maybaum Jr. (Laboratory Manager) to Carbide and 

Carbon Chemicals Corporation (ORNL) and the USAEC (Isotopes Branch; attn: Mr. James R. Mason 

(Chief)); letters regarding Horizons, Inc. various radioactive materials licenses; July 29, 1958 (two 

letters) and November 4, 1958; SRDB Ref ID: 38191. 

Monthly, 1955 , Monthly Progress Report Research and Development in the Field of Thorium 

Chemistry and Metallurgy, Dr. J. L. Wyatt, Project Director; April 16, 1955; SRDB Ref ID: 38039 

Musser, 1954; Memo from D.F. Musser (Chief, SF Materials Accountability Branch, Divisions of 

Production - Washington) to S. R. Gustavson (Chief, SF Accountability Branch, New York 

Operations Office), regarding Horizons, Inc., 2891-2905 E. 79 St., Cleveland, OH.; May 14, 1954; 

SRDB Ref ID: 11008, pdf pp. 45 and 166 

NRC, 1989, Film Badge Dosimetry in Atmospheric Nuclear Tests, Report 69114; National Research 

Council, Committee on Film Badge Dosimetry in Atmospheric Nuclear Tests; National Academy 

Press, Washington D.C.; 1989; SRDB Ref ID: 1905 

NUREG-1400, Air Sampling in the Workplace; Final Report; E. E. Hickey, G. A. Stoetzal, D. J. 

Strom, G. R. Cicotte, C. M. Wiblin, S. A. McGuire; U.S. Nuclear Regulatory Commission; September 

1993; SRDB Ref ID: 20129 

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SEC-00094 03-12-08 Horizons, Inc. 

ORNL, Feb77; Former Horizons, Inc., Building Thoron Concentration Calculations; Oak Ridge 

National Laboratory; February 1977; SRDB Ref ID: 16268 

ORNL, Aug77; ORNL Final Report – Radiological Survey of the Former Horizons, Inc. Metal 

Handling Facility, Cleveland, Ohio; Oak Ridge National Laboratory; August 1977; SRDB Ref ID: 

16450 

Personal Communication, 2007, Personal Communication with Metallurgical Engineer; Telephone 

Interview by ORAU Team; November 26, 2007; OSA Ref ID: 38320 

Plan, 1993, Letter providing Lamotite, Inc., schedule and plan for characterization and 

decontamination for the former Horizons site; letter to J. A. Grobe (Chief, Fuel Cycle and 

Decommissioning Branch, Nuclear Regulatory Commission) from R. M. Van Deventer (General 

Manager, Lamotite, Inc.); SRDB Ref ID: 38196 

R&D, 1955, Research and Development in the Field of Thorium Chemistry and Metallurgy Monthly 

Progress Report for March 15 thru April 15, 1955; Horizons, Inc., Cleveland; April 26, 1955; SRDB 

Ref ID: 38035 

Radiological Health, 1970, Radiological Health Handbook, Revised Edition; Public Health Service, 

U. S. Department of Health, Education, and Welfare; January 1970; Publicly Available 

Remediation Report. 2001, Cleveland Laminating Company (Formerly Horizons, Inc.) Final 

Remediation Report, J. Webb, Lead Inspector; Ohio Department of Health, Bureau of Radiation 

Protection; April 2001; SRDB Ref ID: 38121 

Report, 1954, Investigations for the Production of Thorium Metal, J. C. Bleiweiss and B. C. Raynes 

(Horizons, Inc., Cleveland) for the U.S. Atomic Energy Commission; February 26, 1954; SRDB Ref 

ID: 38058 

RESRAD, 2003, User’s Manual for RESRAD-BUILD Version 3, C. Yu, D.J. LePoire, J.-J. Cheng, E. 

Gnanapragasam, S. Kamboj, J. Arnish, B.M. Biwer. A.J. Zielen, W.A. Williams, A. Wallo III, and H. 

Peterson; ANL/EAD/03-1, Environmental Assessment Division, Argonne National Laboratory; 

Argonne, Illinois; June 2003; http://web.ead.anl.gov/resrad/documents/ANL-EAD-03-1.pdf 

Sehmel, 1980, Particle Resuspension: A Review, G. A. Sehmel, Environmental International 4:107-

127; 1980; SRDB Ref ID: Not yet in SRDB 

Semi-annual Report, 1953, Semi-annual Report for Research Issuance Material, P. S. Maybaum, 

Laboratory Superintendent; June 25, 1953; SRDB Ref ID: 38156 

Service, 1954, Radiation Safety Service for Horizons Incorporated, memo to W. D. Claus (Chief, 

Biophysics Branch, Division of Biology and Medicine, Washington, D.C.) from G. H. Giboney 

(Chief, Radiation Control Branch, SROO, Augusta, Georgia); November 19, 1954: SRDB Ref ID: 

11010 

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SEC-00094 03-12-08 Horizons, Inc. 

Survey, 1955, Radiological Survey of the Former Horizons, Inc., Metal Handling Facility, Cleveland, 

Ohio, R. W. Leggett, W. D. Cotrell, F. F. Haywood, W. H. Shinpaugh and R. W. Doane; April 1955; 

SRDB Ref ID: 16269 

Thorium, 1955, Research and Development in the Field of Thorium Chemistry and Metallurgy. 

Volume L. Preparation of Electrolytic Cell Feed for Production of Thorium Metal, C. E. Fisher & J. 

L. Wyatt, Project Director; SRDB Ref ID: 38306 

Till, 1983, Radiological Assessment. A Textbook on Environmental Dose Analysis, J. E. Till and H. R. 

Meyer; NUREG/CR-3332; U.S. Nuclear Regulatory Commission, Washington, D.C.; 1983; SRDB 

Ref ID: Not yet in SRDB 

Uranium Bars, 1954, Inventory of Uranium Bars at Horizons Incorporated, memo from D. F. Musser 

to S. R. Gustavson, D. F. Musser, Chief; May 14, 1954; SRDB Ref ID: 38158 

USAEC, 1954, Film Badge Reports for Horizons, Inc., from the USAEC – NYOO Health and Safety 

Division from May 1954 through December 1954; 1954; SRDB Ref ID: 10591 

USAEC, 1955, Film Badge Reports for Horizons, Inc., from the USAEC – NYOO Health and Safety 

Division from January 1955 through December 1955; 1955; SRDB Ref ID: 14900 

USAEC, 1956, Letter from Lyall Johnson (Chief, Licensing Branch, division of Civilian Application) 

to Horizons, Inc. (attn: Mr. Murray Medvin); Source Material License; April 24, 1956; SRDB Ref ID: 

38144 

USAEC, 1958, U.S. AEC Compliance Inspection Report, report regarding radioactive materials 

licenses at Horizons, Inc.; May 13, 1958; SRDB Ref ID: 38147 

USNRC, 1993; U.S. NRC Inspection Summary; Inspection of the Former Horizons, Inc. Site; U.S. 

Nuclear Regulatory Commission; June 25, 1993; SRDB Ref ID: 38116 

USNRC, 2000, Probabilistic Dose Analysis Using Parameter Distributions Developed for RESRAD 

and RESRAD-Build Codes; NUREG/CR-6676 <http://hps1.org/sections/decom/nrc_links.html>; U.S. 

Nuclear Regulatory Commission; Washington, D.C.; July 2000; http://www.nrc.gov/reading-rm/doccollections/nuregs/contract/cr6755/ 

Visit, 1953, Horizons, Inc. – Visit of July 24, 1953, memo from A. J. Breslin to W. B. Harris; August 

13, 1953; SRDB Ref ID: 17008, pdf p.137 

Wagoner, 1990; Letter from Mr. James W. Wagoner II (Off-Site Branch; Eastern Area Program 

Division; Office of Environmental Restoration) to Mr. Cliff Florczak (Ecology and Environment, Inc.) 

regarding Horizons, Inc. site information and summaries; June 7, 1990; SRDB Ref ID: 11008, pdf p. 

130 

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