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SEC Petition Evaluation Report 

Petition SEC-00182 

Report Rev #: 0 Report Submittal Date: July 14, 2011 

Subject Expert(s): Ray Clark, Bob Coblentz, Jason Davis, Joe Guido 

Site Expert(s): N/A

Petition Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Petition 

Receipt Date 

Qualification Date DOE/AWE Facility Name 

SEC-00182 83.13 December 21, 2010 February 17, 2011 W.R. Grace and Company (Maryland) 

Petitioner-Requested Class Definition 

Chemical operators, bar mill operators, and pot operators who worked with or on rotary dryers, pill machines, 

nauta mixes (sieves), hydroxide dryer, blenders #1 and #3, Reactor 906 and 902 material, Red Dog and Vanadium 

material at the Specialty, Monasito [sic], LDI Plants, Tech Center, Buildings 109, 193, 194, and 224 at W.R. 

Grace and Company, Curtis Bay, Maryland, from 1955 through 2009. 

Class Evaluated by NIOSH 

All Atomic Weapons Employees who worked at W.R. Grace and Company in Curtis Bay, Maryland, for the 

operational period from January 1, 1955 through December 31, 1958 and the residual radiation period from 

January 1, 1959 through October 31, 2009. 

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

All Atomic Weapons Employees who worked at any building or area at the facility owned by W.R. Grace and 

Company in Curtis Bay, Maryland, for the operational period from May 1, 1956 through January 31, 1958, for a 

number of work days aggregating at least 250 work days, occurring either solely under this employment, or in 

combination with work days within the parameters established for one or more other classes of employees in the 

Special Exposure Cohort.

Related Petition Summary Information 

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

N/A N/A N/A N/A 

Related Evaluation Report Information 

Report Title DOE/AWE Facility Name 

N/A N/A 

ORAU Lead Technical Evaluator: Ray Clark ORAU Peer Review Completed By: Daniel Stempfley 

Peer Review Completed By: [Signature on File] 7/13/2011 

Lara Hughes Date 

SEC Petition Evaluation Reviewed By: [Signature on File] 7/14/2011 

J. W. Neton Date 

SEC Evaluation Approved By: [Signature on File] 7/14/2011 

Stuart L. Hinnefeld Date 
SEC-00182 07-14-11 W.R. Grace and Co. (Maryland)

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Evaluation Report Summary: SEC-00182, W.R. Grace and Company 

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-00182 was received on December 21, 2010, and qualified on February 17, 2011. The 

petitioner requested that NIOSH consider the following class: Chemical operators, bar mill operators, 

and pot operators who worked with or on rotary dryers, pill machines, nauta mixes (sieves), 

hydroxide dryer, blenders #1 and #3, Reactor 906 and 902 material, Red Dog and Vanadium material 

at the Specialty, Monasito [sic], LDI Plants, Tech Center, Buildings 109, 193, 194, and 224 at W.R. 

Grace and Company, Curtis Bay, Maryland, from 1955 through 2009.

Class Evaluated by NIOSH

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

the following class: All Atomic Weapons Employees who worked at W.R. Grace and Company in 

Curtis Bay, Maryland, for the operational period from January 1, 1955 through December 31, 1958 

and the residual radiation period from January 1, 1959 through October 31, 2009. Note: The DOE 

defines the dates for the operational period as “1955-1958,” and the dates for the residual period as 

“1959-October 2009.” NIOSH has applied the earliest logical start dates and latest logical end dates 

for defining the periods to be evaluated. 

NIOSH-Proposed Class to be Added to the SEC

Based on its full research of the class under evaluation, NIOSH has defined a single class of 

employees for which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSHproposed class includes all Atomic Weapons Employees who worked at any building or area at the 

facility owned by W.R. Grace and Company in Curtis Bay, Maryland, for the operational period from 

May 1, 1956 through January 31, 1958, for a number of work days aggregating at least 250 work 

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

parameters established for one or more other classes of employees in the Special Exposure Cohort. 

The class under evaluation was modified (see Section 3.0 below). The time period was reduced to 

correspond to the duration of the monazite sand and thorium work. The job titles were expanded to 

include all workers because, although all thorium-refining work was completed within Building 23, all 

workers may have had unlimited access to the building. The period before May 1, 1956 is not 

included in the proposed SEC class because NIOSH has determined that AEC-related operations 

involving radioactive materials did not start at the Curtis Bay, Maryland site until May 1956 with the 

completion of site construction. Based on this information, that period will not be included in the 

radiological dose assessment included in this evaluation. The period from February 1, 1958 through 

December 31, 1958 is not included in the proposed SEC class because NIOSH has determined that 
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AEC-related operations had ceased at the site by the end of January 1958. Therefore, these eleven 

months along with the period from January 1, 1959 through October 31, 2009 are considered the 

residual radiation period. The residual radiation period is not included in the NIOSH-proposed SEC 

class because dose reconstruction has been determined to be feasible. 

Feasibility of Dose Reconstruction

NIOSH finds it is not feasible to estimate internal or external exposures with sufficient accuracy for 

all workers at the site for the operational period from May 1, 1956 through January 31, 1958. Internal 

monitoring data, work area radiological monitoring data, and source term data are not available. 

Furthermore, NIOSH has not identified any external monitoring records or personal dosimetry data 

associated with the thorium processing that occurred during the operational period under evaluation. 

NIOSH also has not been able to identify any radiological surveys or area monitoring data conducted 

or gathered during the operational period. 

For the residual radiation period, 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 more precisely than an 

estimate of maximum dose. Information available from additional resources for other site performing 

similar work is sufficient to document or estimate the maximum internal and external potential 

exposure to members of the evaluated class under plausible circumstances during the residual 

radioactivity period from February 1, 1958 through October 31, 2009. 

The NIOSH dose reconstruction feasibility findings are based on the following: 

• Principal sources of internal radiation for members of the proposed class included exposures to 

uranium, thorium, and their progeny present in the monazite sands during milling and extraction 

operations. The modes of exposure were inhalation and ingestion of dust generated during the 

various processes associated with monazite sand. Isotopic components of monazite sand include 

U-238 and Th-232 and their decay progeny. Depending on their geographical source, monazite 

sands contain approximately 2.5% to 8 % thorium oxides. 

• Thorium was the only radionuclide refined during the operational period; internal exposure was 

primarily a concern during this process. NIOSH finds that it lacks sufficient personnel or area 

monitoring data, source term data, and operational information to support assessing internal dose 

with sufficient accuracy during the operational period from May 1, 1956 through January 31, 

1958, which encompasses the period that AEC-related radiological operations were performed on 

site. 
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• During the residual period, workers had a potential for internal exposure due to re-suspended 

surface contamination. NIOSH finds that it has access to sufficient area monitoring data and 

surrogate site information to support assessing internal dose with sufficient accuracy during the 

residual radioactivity period from February 1, 1958 through October 31, 2009. 

• Principal sources of external radiation for members of the proposed class included exposures to 

uranium, thorium, and their progeny present in the monazite sands during milling and extraction 

operations. NIOSH finds that it lacks sufficient personnel or area monitoring data, source term 

data, and operational information to support assessing external dose with sufficient accuracy 

during the operational period from May 1, 1956 through January 31, 1958, which encompasses the 

period that AEC-related radiological operations were performed on site. 

• During the residual period, workers were potentially exposed to external radiation from residual 

surface contamination. NIOSH finds that it has access to sufficient area monitoring data and 

surrogate site information to support assessing external dose with sufficient accuracy during the 

residual radioactivity period from February 1, 1958 through October 31, 2009. 

• Based on its research, NIOSH has concluded that physical examinations with X-rays were not 

performed at the site. Therefore, medical X-ray dose is not a consideration for W.R. Grace and 

Company-Maryland workers. 

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

either: (1) estimate the maximum radiation dose, for every type of cancer for which radiation 

doses are reconstructed, that could have been incurred under plausible circumstances by any 

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

than a maximum dose estimate. 

• Although NIOSH found that it is not possible to completely reconstruct radiation doses for the 

proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). Therefore, dose reconstructions for individuals employed 

at W.R. Grace and Company in Curtis Bay, Maryland during the period from May 1, 1956 through 

January 31, 1958, but who do not qualify for inclusion in the SEC, may be performed using these 

data as appropriate. 

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 does not have sufficient information to estimate dose for the members 

of the proposed class during the operational period from May 1, 1956 through January 31, 1958. 

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

establish that the proposed class was exposed to radiation during a discrete incident likely to have 

involved exceptionally high-level exposures. However, evidence indicates that some workers in the 

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

thorium and uranium, combined with external exposures to gamma, beta, and neutron radiation. 
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Consequently, NIOSH has determined that health was endangered for those workers covered by this 

evaluation who were employed for at least 250 aggregated work days either solely under this 

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

classes. 

For the residual radioactivity period from February 1, 1958 through October 31, 2009, a health 

endangerment determination is not required because NIOSH has determined that it has sufficient 

information to estimate dose for the members of the evaluated class. 
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Table of Contents 

1.0 Purpose and Scope ........................................................................................................................ 11

2.0 Introduction .................................................................................................................................. 11

3.0 SEC-00182, W.R. Grace and Company (Maryland) Class Definitions ....................................... 12

3.1 Petitioner-Requested Class Definition and Basis ................................................................ 12

3.2 Class Evaluated by NIOSH ................................................................................................. 13

3.3 NIOSH-Proposed Class to be Added to the SEC ................................................................ 14

4.0 Data Sources Reviewed by NIOSH to Evaluate the Class ........................................................... 14

4.1 Site Profile Technical Basis Documents (TBDs) ................................................................ 15

4.2 Technical Information Bulletins .......................................................................................... 15

4.3 Facility Employees and Experts .......................................................................................... 15

4.4 Previous Dose Reconstructions ........................................................................................... 16

4.5 NIOSH Site Research Database .......................................................................................... 16

4.6 Documentation and/or Affidavits Provided by Petitioners ................................................. 17

5.0 Radiological Operations Relevant to the Class Evaluated by NIOSH ......................................... 17

5.1 W.R. Grace and Company (Maryland) Plant and Process Descriptions ............................. 17

5.2 Radiological Exposure Sources from W.R. Grace & Co. (MD) Operations ....................... 20

5.2.1 Internal Radiological Exposure Sources - W.R. Grace & Co. (MD) Operations .... 20

5.2.1.1 Uranium .................................................................................................... 21

5.2.1.2 Thorium .................................................................................................... 21

5.2.1.3 Radon/Thoron and Progeny ...................................................................... 21

5.2.2 External Radiological Exposure Sources - W.R. Grace & Co. (MD) Operations ... 21

5.2.2.1 Photon ....................................................................................................... 21

5.2.2.2 Beta ........................................................................................................... 23

5.2.2.3 Neutron ..................................................................................................... 23

6.0 Summary of Available Monitoring Data for the Class Evaluated by NIOSH ............................. 24

6.1 Available W.R. Grace and Company (Maryland) Internal Monitoring Data ...................... 24

6.1.1 Bldg. 23 - Site Characterization Data from W.R. Grace, Curtis Bay - 1986 .......... 24

6.1.2 Air Monitoring Data from W.R. Grace / Rare Earths in Wayne, NJ ...................... 27

6.1.3 Radioactive Waste Disposal Area (RWDA) Site Characterization ......................... 27

6.2 Available W.R. Grace and Company (Maryland) External Monitoring Data ..................... 29

6.2.1 W.R. Grace, Curtis Bay MD – Building 23 ............................................................ 29

6.2.2 W.R. Grace Pompton Plains Facility (Wayne NJ) .................................................. 30

6.2.3 Lindsay Light, West Chicago, IL ............................................................................ 31

6.2.4 Radioactive Waste Disposal Area (RWDA) Site Characterization ......................... 31

7.0 Feasibility of Dose Reconstruction for the Class Evaluated by NIOSH ...................................... 32

7.1 Pedigree of W.R. Grace and Company (Maryland) Data .................................................... 33

7.1.1 Internal Monitoring Data Pedigree Review ............................................................. 33

7.1.2 External Monitoring Data Pedigree Review ............................................................ 33
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7.2 Evaluation of Bounding Internal Radiation Doses at W.R. Grace (MD) ............................ 34

7.2.1 Evaluation of Bounding Process-Related Internal Doses ........................................ 34

7.2.2 Evaluation of Bounding Residual Period Internal Doses ........................................ 34

7.2.3 Methods for Bounding Internal Dose at W.R. Grace and Company (Maryland) .... 34

7.2.3.1 Methods for Bounding Operational Period Internal Dose ........................ 35

7.2.3.2 Methods for Bounding Residual Period Internal Dose ............................. 35

7.2.4 Internal Dose Reconstruction Feasibility Conclusion ............................................. 40

7.3 Evaluation of Bounding External Radiation Doses at W.R. Grace (MD) ........................... 40

7.3.1 Evaluation of Bounding Process-Related External Doses ....................................... 40

7.3.2 Evaluation of Bounding Residual Period External Doses ....................................... 40

7.3.3 W.R. Grace and Company (Maryland) Occupational X-Ray Examinations ........... 41

7.3.4 Methods for Bounding External Dose at W.R. Grace and Company ...................... 41

7.3.4.1 Methods for Bounding Operational Period External Dose ....................... 41

7.3.4.2 Methods for Bounding Residual Period External Doses .......................... 41

7.3.5 External Dose Reconstruction Feasibility Conclusion ............................................ 43

7.4 Evaluation of Petition Basis for SEC-00182 ....................................................................... 44

7.5 Summary of Feasibility Findings for Petition SEC-00182 .................................................. 45

8.0 Evaluation of Health Endangerment for Petition SEC-00182 ...................................................... 46

9.0 Class Conclusion for Petition SEC-00182 ................................................................................... 47

10.0 References .................................................................................................................................... 49

Attachment 1: Data Capture Synopsis ................................................................................................... 53
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Tables 

4-1: No. of W.R. Grace & Co. (MD) Claims Submitted Under the Dose Reconstruction Rule ........... 16

5-1: Principal Radiation Emissions from Th-232 and its Short-Lived Decay Products ........................ 22

5-2: Principal Radiation Emissions from Natural Uranium and Its Short-lived Decay Products ......... 23

6-1: Summary of Direct and Removable Alpha Surface Contamination Data – Curtis Bay ................ 24

6-2: Summary of Rn-220 and Rn-222 Air Activity Data – Curtis Bay ................................................. 25

6-3: Summary of Th-232 Air Activity Data – Curtis Bay ..................................................................... 25

6-4: Summary of Th-232 and U-238 Concentration Data in Building Dust – Curtis Bay .................... 25

6-5: FUSRAP Area of Concern (AOC) Designations – Curtis Bay ...................................................... 26

6-6: Air Monitoring Data - W.R. Grace, Wayne NJ Facility ................................................................ 27

6-7: Soil Concentration Within RWDA ................................................................................................ 28

6-8: Th-228 and Th-232 Isotopic Analysis Results ............................................................................... 28

6-9: Air Monitoring Data Collected During RWDA Sampling/Site Investigation ............................... 29

6-10: Average Gamma Dose Rates in Work Areas in Building 23 ....................................................... 29

6-11: External Dose Survey of Wayne, NJ Facility .............................................................................. 30

6-12: Summary of Radiation Measurements at Lindsay Light ............................................................. 31

6-13: Radiation Measurements Collected in the RWDA ...................................................................... 32

7-1: Residual Period Inhalation and Ingestion Intakes – Bldg. 23 ........................................................ 36

7-2: Inhalation Intake Rates Based on Source Concentration Data ...................................................... 37

7-3: Residual Period Inhalation Intakes (RWDA) ................................................................................. 39

7-4: Adjusted External Dose Rates for the RWDA ............................................................................... 42

7-5: Summary of Feasibility Findings for SEC-00182 .......................................................................... 45
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SEC Petition Evaluation Report for SEC-00182 

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

the data presented in this evaluation were made by the ORAU Team Lead Technical Evaluator: Ray 

Clark, Oak Ridge Associated Universities. 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 Atomic Weapons Employees who 

worked at W.R. Grace and Company in Curtis Bay, Maryland, for the operational period from January 

1, 1955 through December 31, 1958 and the residual radiation period from January 1, 1959 through 

October 31, 2009. 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 Division of Compensation Analysis and Support’s (DCAS) Internal 

Procedures for the Evaluation of Special Exposure Cohort Petitions, OCAS-PR-004.1

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.2

 

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.

 

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 

 

1

 DCAS was formerly known as the Office of Compensation Analysis and Support (OCAS). 

2

 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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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 one or more other SEC 

classes. 

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 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.3

 

3.0 SEC-00182, W.R. Grace and Company (Maryland) Class 

Definitions 

The following subsections address the evolution of the class definition for SEC-00182, W.R. Grace 

and Company, located in Curtis Bay, Maryland. When a petition is submitted, the requested class 

definition is reviewed as submitted. Based on its review of the available site information and data, 

NIOSH will make a determination whether to qualify for full evaluation all, some, or no part of the 

petitioner-requested class. If some portion of the petitioner-requested class is qualified, NIOSH will 

specify that class along with a justification for any modification of the petitioner’s class. After a full 

evaluation of the qualified class, NIOSH will determine whether to propose a class for addition to the 

SEC and will specify that proposed class definition. 

3.1 Petitioner-Requested Class Definition and Basis 

Petition SEC-00182 was received on December 21, 2010, and qualified on February 17, 2011. The 

petitioner requested that NIOSH consider the following class: Chemical operators, bar mill operators, 

and pot operators who worked with or on rotary dryers, pill machines, nauta mixes (sieves), 

hydroxide dryer, blenders #1 and #3, Reactor 906 and 902 material, Red Dog and Vanadium material 

at the Specialty, Monasito [sic], LDI Plants, Tech Center, Buildings 109, 193, 194, and 224 at W.R. 

Grace and Company, Curtis Bay, Maryland, from 1955 through 2009.

3

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

accurate dose reconstruction over time is impossible for the W.R. Grace and Company (Maryland) 

workers in question. NIOSH deemed the following information and affidavit statements sufficient to 

qualify SEC-00182 for evaluation: 

The petitioner submitted an individual dose reconstruction report indicating that individual 

monitoring records do not exist for the W.R. Grace and Company (Maryland) for the operational 

and residual periods. 

On page 5 of the NIOSH dose reconstruction report: [NIOSH ID and DOL Case Number 

Redacted] it clearly states that no records were found to indicate any monitoring was done for the 

period from 1955 through 1989. 

Based on its W.R. Grace and Company (Maryland) research and data capture efforts, NIOSH 

determined that it has access to contracts, amendments, and process records for W.R. Grace and 

Company (Maryland) workers during the time period under evaluation. However, NIOSH also 

determined that monitoring records are not complete for all time periods or for all radionuclides. 

NIOSH concluded that there is sufficient documentation to support, for at least part of the requested 

time period, the petition basis that internal and external radiation exposures and radiation doses were 

not adequately monitored at W.R. Grace and Company (Maryland), either through personal 

monitoring or area monitoring. The information and statements provided by the petitioner qualified 

the petition for further consideration by NIOSH, the Board, and HHS. The details of the petition basis 

are addressed in Section 7.4. 

3.2 Class Evaluated by NIOSH 

Based on its preliminary research, NIOSH modified the petitioner-requested class. The time period 

was divided into an operational period and a residual radiation period. The worker specifications were 

expanded to include all workers because it was unclear whether exposures could be limited to certain 

buildings/areas and job titles. Therefore, NIOSH defined the following class for further evaluation: 

All Atomic Weapons Employees who worked at W.R. Grace and Company in Curtis Bay, Maryland, 

for the operational period from January 1, 1955 through December 31, 1958 and the residual radiation 

period from January 1, 1959 through October 31, 2009. Note: DOE defines the dates for operations as 

“1955-1958,” and the dates for the residual period as “1959-October 2009.” NIOSH has applied the 

earliest logical start dates and latest logical end dates for defining the periods to be evaluated. 
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3.3 NIOSH-Proposed Class to be Added to the SEC 

Based on its research of the class under evaluation, NIOSH has defined a single class of employees for 

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

to be added to the SEC includes all Atomic Weapons Employees who worked at any building or area 

at the facility owned by W.R. Grace and Company in Curtis Bay, Maryland, for the operational period 

from May 1, 1956 through January 31, 1958, for a number of work days aggregating at least 250 work 

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

parameters established for one or more other classes of employees in the Special Exposure Cohort. 

The period before May 1, 1956 is not included in the proposed SEC class because NIOSH has 

determined that AEC-related operations involving radioactive materials did not start at the Curtis Bay, 

Maryland site until May 1956 with the completion of site construction. Based on this information, 

this period will not be included in the radiological dose assessment included in this evaluation. The 

period from February 1, 1958 through December 31, 1958 is not included in the proposed SEC class 

because NIOSH has determined that AEC-related operations had ceased at the site by the end of 

January 1958. Therefore, these eleven months along with the period from January 1, 1959 through 

October 31, 2009 are considered the residual radiation period. The residual radiation period is not 

included in the NIOSH-proposed SEC class because dose reconstruction has been determined to be 

feasible. 

4.0 Data Sources Reviewed by NIOSH to Evaluate the Class 

As is standard practice, NIOSH completed an extensive database and Internet search for information 

regarding W.R. Grace and Company. The database search included the DOE Legacy Management 

Considered Sites database, the DOE Office of Scientific and Technical Information (OSTI) database, 

the Energy Citations database, the Atomic Energy Technical Report database, and the Hanford 

Declassified Document Retrieval System. In addition to general Internet searches, the NIOSH 

Internet search included OSTI OpenNet Advanced searches, OSTI Information Bridge Fielded 

searches, Nuclear Regulatory Commission (NRC) Agency-wide Documents Access and Management 

(ADAMS) web searches, the DOE Office of Human Radiation Experiments website, and the DOENational Nuclear Security Administration-Nevada Site Office-search. Attachment 1 contains a 

summary of W.R. Grace and Company documents. The summary specifically identifies data capture 

details and general descriptions of the documents retrieved. 

In addition to the database and Internet searches listed above, NIOSH identified and reviewed 

numerous data sources to determine information relevant to determining the feasibility of dose 

reconstruction for the class of employees under evaluation. 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. 
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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. 

As part of NIOSH’s evaluation detailed herein, it examined the following Site Profiles for insights 

into W.R. Grace and Company (Maryland) operations or related topics/operations at other sites: 

• Site Profiles for Atomic Weapons Employers that Worked Uranium and Thorium Metals, BattelleTBD-6000, PNWD-3738, Rev 0; Battelle; December 13, 2006; SRDB Ref ID: 30671 

4.2 Technical Information Bulletins 

A Technical Information Bulletin is a general working document that provides guidance for preparing 

dose reconstructions at particular sites or categories of sites. NIOSH reviewed the following 

Technical Information Bulletins as part of its evaluation: 

• Estimation of Ingestion Intakes, OCAS-TIB-009, Rev. 0; National Institute for Occupational 

Safety and Health (NIOSH); April 13, 2004; SRDB Ref ID: 22397 

• Estimating the Maximum Plausible Dose to Workers at Atomic Weapons Employer Facilities, 

ORAUT-OTIB-0004, Rev. 03 PC-2; Oak Ridge Associated Universities; December 6, 2006; 

SRDB Ref ID: 29949

• Dose Reconstruction During Residual Radioactivity Periods at Atomic Weapons Employer 

Facilities, ORAUT-OTIB-0070, Rev. 00; Oak Ridge Associated Universities; March 10, 2008; 

SRDB Ref ID: 41603

4.3 Facility Employees and Experts 

To obtain additional information, NIOSH interviewed an SEC petitioner representative and a former 

W.R. Grace and Company (Maryland) employee. 

• Personal Communication, 2011a, Personal Communication with Petitioner Representative;

Telephone Interview by ORAU Team; May 5, 2011; SRDB Ref ID: 96226

• Personal Communication, 2011b, Personal Communication with former W.R. Grace and 

Company (Maryland) Supervisor; Telephone Interview by ORAU Team; May 11, 2011; SRDB 

Ref ID: 96224
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4.4 Previous Dose Reconstructions 

NIOSH reviewed its NIOSH DCAS Claims Tracking System (referred to as NOCTS) to locate 

EEOICPA-related dose reconstructions that might provide information relevant to the petition 

evaluation. Table 4-1 summarizes the results of this review. (NOCTS data available as of June 15, 

2011) 

Table 4-1: No. of W.R. Grace & Co. (MD) Claims Submitted Under the Dose Reconstruction Rule 

Description Totals 

Total number of claims submitted for dose reconstruction 1 

Total number of claims submitted for energy employees who worked during the period under 

evaluation (January 1, 1955 through December 31, 1958 [operational period]; January 1, 1959 

through October 31, 2009 [residual radiation period]) 1 

Number of dose reconstructions completed for energy employees who worked during the period 

under evaluation (i.e., the number of such claims completed by NIOSH and submitted to the 

Department of Labor for final approval). 1 

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

evaluated class definition 0 

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

evaluated class definition 0 

NIOSH reviewed the one claim submitted for dose reconstruction to determine whether internal 

and/or external personal monitoring records could be obtained for the employee. This claim did not 

contain any exposure data. 

4.5 NIOSH Site Research Database 

NIOSH also examined its Site Research Database (SRDB) to locate documents supporting the 

assessment of the evaluated class. One hundred thirty-two documents in this database were identified 

as pertaining to W.R. Grace and Company (Maryland) (as of June 13, 2011). These documents were 

evaluated for their relevance to this petition. The documents include contracts, amendments, and 

process records. 
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4.6 Documentation and/or Affidavits Provided by Petitioners 

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

petitioner: 

• SEC Petition Form B for SEC-00182, W.R. Grace and Company (Maryland); [Name redacted]; 

December 21, 2010; OSA Ref ID: 112871, pdf pp. 1-10

• NIOSH Report of Dose Reconstruction under the Energy Employees Occupational Illness 

Compensation Program (EEOICPA); [Case No. redacted]; July 1, 2009; OSA Ref ID: 112871, pdf 

pp. 13-31

5.0 Radiological Operations Relevant to the Class Evaluated by 

NIOSH 

The following subsections summarize both radiological operations at W.R. Grace and Company from 

January 1, 1955 through December 31, 1958 (operational period), and January 1, 1959 through 

October 31, 2009 (residual radiation 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 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 intended only to be a summary of the available information. 

5.1 W.R. Grace and Company (Maryland) Plant and Process Descriptions 

W.R. Grace and Company (as it is currently named) is located in Curtis Bay, Maryland. The site 

(currently 109 acres; originally 260 acres) is partially covered with chemical plant facilities in the 

northwest section and spoils ponds and a disposal area in the northeast section (Remedial 

Investigation, 2000, pdf p. 3). Atomic Energy Commission (AEC) contract work was carried out in 

the southwest section of one building, Building 23, within an area measuring 100 feet east/west by 

200 feet north/south and five levels in height (60-70 feet) (Trip Report, 1985, pdf p.7). For the period 

evaluated by NIOSH, the W.R. Grace and Company (Maryland) workforce consisted of 25-30 

workers (Personal Communication, 2011b). 

In 1909, the Davison Chemical Corporation purchased the Curtis Bay Works location, then known as 

"Chairs Farm." By the early 1940s, Davison Chemical Corporation was producing several 

agricultural and industrial chemicals (mainly fertilizers). In 1954, W.R. Grace, a Connecticut 

corporation, acquired Davison Chemical Corporation. The Curtis Bay Works location became known 

as the Davison Chemical Division of W.R. Grace and Company (Remedial Investigation, 2000). 

Rare Earths, Inc. entered into contract AT (49-6)-993 with the AEC on July 18, 1955, to process 7,900 

tons of monazite sands at the Curtis Bay Facility and at the Pompton Plains Facility in Wayne, New 

Jersey (Remedial Investigation, 2000, pdf p. 4). Rare Earths obtained a license under the Atomic 

Energy Act of 1954 to possess, transfer, and use the radioactive material thorium, which is defined by 
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the U. S. Code as a "source material” (Contracts and Amendments, 1950s, pdf p. 2). This license was 

transferred to W.R. Grace and Company (Maryland) in late 1956 or early 1957. W.R. Grace and 

Company (the sole shareholder in Rare Earths) became a party to contract AT (49-6)-993 on 

November 30, 1956, with the dissolution of Rare Earths, Inc. The contract called for W.R. Grace and 

Company to process the AEC-owned monazite ore at a plant in New Jersey and/or one to be 

constructed in Curtis Bay, Maryland. Various documents indicate that the Curtis Bay, Maryland plant 

was completed and placed in operation sometime between May and June 1956 (Johnson, 1958, pdf p. 

3, FUSRAP documents, various dates). The Curtis Bay facility did most of the processing of the AEC 

ore for this contract (Designation Summary, date unknown, pdf p. 2). 

Thorium was shipped to the Davison Chemical Division as a component of monazite sand obtained 

from India and other foreign and domestic sources (e.g., Brazil, Asia, and Idaho). The average 

thorium content was about 6 percent thorium dioxide. The title to the monazite and the thorium 

remained with the government during the performance of the contract work. According to the 

contract terms, at least 95% of the thorium and rare earths in the ore were to be returned to the AEC 

(Designation Summary, date unknown). 

The monazite gangue (i.e., unreacted material) consisted primarily of silica, calcium sulfate, 

diatomaceous earth, and unreacted monazite including certain thorium and uranium compounds and 

compounds of their progeny. The gangue was said to not contain more than 5% of the original 

thorium content. At the direction of the AEC, the gangue was retained by W. R. Grace for noncommercial disposition (Designation Summary, date unknown, pdf p. 2). 

Building 23 and the Monazite Sand Thorium-Recovery Process 

AEC contract work was carried out in one building, Building 23. The southwest section of Building 

23 is the only portion of any site building where monazite sands processing was conducted. The 

southwest section of Building 23 measures 100 feet east/west by 200 feet north/south and has a height 

of five levels (60-70 feet). The building is a steel frame structure with 8-feet deep steel roof trusses 

with corrugated metal siding. An elevator shaft is present which was used for transport of the 

monazite sands. An enclosed (brick) electrical substation is present at the southwest corner of the 

building. The ground floor level has concrete slab floor with piping floor chases. Intermediate floor 

levels are concrete slab and metal decking supported by steel beam frames. Typical equipment 

includes pumps, tanks, piping, dust hoppers, and a rotary kiln. Some corrosion to steel columns and 

beams was noted. Access to the roof was available and several exhaust ducts and stacks were present 

(Trip Report, 1985, pdf p. 7). 

Monazite sand was ground through 200 mesh in a Hardinge ball mill and transferred to the reactors, 

which were jacketed Dopp kettles. There, the ground sand was reacted with concentrated sulfuric acid 

for approximately four hours. The viscous mass was then dropped into large crystallizer tanks made 

up of diluted recycled thorium-bearing acid. The crystallizer slurry was pumped into a Dorr rake 

classifier where a crude separation of rare earth sulfate crystals from the thorium-bearing acid solution 

was accomplished. The thorium-bearing solution was then filtered on a large Dorr-Oliver rotary drum 

vacuum pre-coat filter. The thorium-bearing solution was separated from unreacted gangue and 

further processed by precipitation with concentrated hydrofluoric acid, forming thorium fluoride. The 

thorium fluoride was reacted with 50% caustic soda, forming sodium fluoride that was washed free of 
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the insoluble thorium hydrate. The thorium hydrate was twin-drum dried and packaged for shipment 

to the Curtis Bay Government Storage Depot (Monazite Process, date unknown, pdf p. 12). 

The aforementioned gangue, made up of various forms of calcium sulfate, calcium silicate, iron 

sulfate, and unreacted monazite, was retained on the pre-coat (diatomaceous earth) of the filter and 

uniformly cut off by a doctor blade, collected in Dempster Dumpster-type tubs and removed from the 

plant by the yard crew truck. The Dempster Dumpsters were emptied into the designated area of the 

Curtis Bay dump (Monazite Process, date unknown, pdf p. 12). The radioactive gangue was buried at 

various depths up to about nine feet. Other contaminated materials such as filter cloths and 

miscellaneous equipment were disposed of in the same manner (Designation Summary, date 

unknown, pdf p. 2). The landfill-type area covers about four acres. It is a few hundred feet south of 

the bay and is bordered on the south and west by a Baltimore and Ohio Railroad spur running over the 

W.R. Grace and Company property. The surrounding areas are industrial, and the nearest residence is 

about one-half mile away. The facility is still owned by W.R. Grace and Company. The site is fenced 

and has been patrolled by W.R. Grace guards since 1976 (Designation Summary, date unknown, pdf 

p. 3). 

The facility at Curtis Bay was developmental and the workforce was small. A former W.R. Grace 

(Maryland) supervisor estimates that there were only 20-30 employees during the 1950-1960 period 

(Personal Communication, 2011b). It had serious problems in handling the AEC monazite and was 

never fully completed. It operated for about one year from May 1956 through late spring 1957. As a 

result of the processing problems and other considerations, AEC and W.R. Grace and Company 

mutually agreed to terminate the contract, effective January 31, 1958 (FUSRAP documents, various 

dates). In line with this agreement, effective January 31, 1958, the total quantity of ore required to be 

processed under the contract was reduced, through Amendment 3, to 997.6l tons, the total amount 

processed to that date (Designation Summary, date unknown, pdf p. 3). 

A review of the contract file and discussions with individuals with peripheral knowledge of Company 

matters dating back to the late 1950s lead to the conclusion that the failure of the commercial facility 

and the termination of the AEC contract caused W.R. Grace and Company to dismiss the entire 

project as concluded. The plant facility was shut down in 1957, the assets were disposed of, and the 

project abandoned (Shaw, 1978, pdf p. 13). The northwest section of the property contains the plant 

buildings, including Building 23, whose southwest part was used for thorium processing and is the 

only potentially radiologically-contaminated building (Trip Report, 1985, pdf p. 3). NIOSH found 

indications that work with radioactive materials may have continued after the contract was cancelled. 

The work involved uranium and was done in the 1970s in support of operations of the W.R. Grace site 

in Erwin, TN. This work is currently outside the Atomic Weapons Employer operations period as 

defined by DOE. 

Radioactive Waste Disposal Area (RWDA)

From May 1956 through late spring 1957, radioactive gangue from processing operations at Curtis 

Bay was reportedly buried on plant property in a landfill area east of Herring Pond (encompassing the 

RWDA). Approximately 26,000 cubic yards of residue were buried with other miscellaneous 

equipment, rare earth double salt, filter cloths, and mechanical scrap. General waste, including rock, 

refuse (glass, paper, wood, and metal) and dredged soil was also disposed of in this area. Waste is 

believed to be buried at various depths up to 9 feet, but may be as deep as 25 feet (RWDA Remedial 

Investigation Vol. 1, 2001).
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The RWDA lies in the central, undeveloped portion of the Curtis Bay Facility; however, the exact 

RWDA boundary is unknown. A radiological surface survey in 1978 identified an area covering 

approximately 4 acres containing radioactive contamination (Shaw, 1978). At the time of the 1978 

survey, the area was not fenced; however, the 1978 report states: 

Since early May, 1978, the four acre site has been observed by each guard shift without entry 

on to the site. The site is unoccupied and untraversed, remote, and within the fenced 

enclosure surrounding the entire plant property, but not separately fenced or marked. 

In 1995, a fence was installed around the area. During fence installation, the fence line was 

radiologically surveyed by RSO, Inc. (a W.R. Grace subcontractor). RSO personnel were 

accompanied by the W.R. Grace Radiation Safety Officer to ensure that areas of elevated radioactivity 

were enclosed by the fence. Based on survey results and site conditions (i.e., heavy vegetation and 

trees on the east side of Herring Pond), no fencing was placed along the western border of the RWDA 

(along Herring Pond). Instead, the fence was run down to the Herring Pond water line on the 

northeast and southeast corners of the pond. The area encompassed by the fence is approximately 7.2 

acres (RWDA Remedial Investigation Vol. 1, 2001).

5.2 Radiological Exposure Sources from W.R. Grace & Co. (MD) Operations 

The following subsections provide an overview of the internal and external exposure sources for the 

W.R. Grace and Company class under evaluation. 

5.2.1 Internal Radiological Exposure Sources - W.R. Grace & Co. (MD) Operations 

W.R. Grace and Company (Maryland), under contract with AEC, processed monazite sands for 

thorium extraction. Depending on the geographical source, monazite sands contain (by weight) 

approximately 2.5% to 8% thorium, and about 0.15% to 0.5% uranium (Monazite Process, 1951, pdf 

p. 4; Monazite, 1949, pdf p. 2). The monazite processes likely resulted in worker internal exposures 

to uranium, thorium, and their respective decay products. Tables 5-1 and 5-2 list the respective decay 

products. 

The primary internal exposure pathways for workers were likely to include: 

• Inhalation and ingestion of dust generated during the processes employed for thorium extraction, 

particularly during dry-product-handling evolutions 

• Inhalation and ingestion of re-suspended particulates from the build-up of contamination in work 

areas and on equipment 

• Ingestion of particulates by workers who ate or drank in areas where a buildup of contamination 

had occurred (e.g., lunch rooms, locker rooms, etc.) 

• Inhalation of radon (Rn-222) and thoron (Rn-220) and the associated progeny 
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5.2.1.1 Uranium

The principal source of internal exposure to uranium radionuclides at the site was from the inhalation 

of dust or fumes generated during the refining process. Isotopic components of monazite sand include 

U-238 and its decay progeny. The decay progeny of U-238 (i.e., Th-230, Ra-226, etc.) in the raw 

monazite sand would also be expected to have a similar concentration ratio in relation to Th-232 

(Feasibility Study, 2003, pdf p. 3). During the refining processes, there was the possibility of airborne 

dust or fumes that potentially contained uranium. 

5.2.1.2 Thorium

Thorium was the only radionuclide refined during the operational period; exposure was primarily 

during this process. Monazite sands, depending on the geographical source, contain approximately 

2.5% to 8 % thorium oxides. By typical methods, thorium extraction processes are capable of 

collecting greater than 90% of the thorium fraction. This could have resulted in significant amounts 

of thorium concentrates, resulting in potential internal exposures to personnel who were handling 

those concentrates at the various stages in the process. However, total amounts cannot be determined 

from currently available information. 

5.2.1.3 Radon/Thoron and Progeny

Thoron (Rn-220) is the second decay product of Th-228, and would be in equilibrium with the parent 

Th-228 within monazite sands. Similarly, radon (Rn-222) would be in equilibrium with the uranium 

that might be present with the sands. Potential exposures to radon/radon progeny and thoron/thoron 

progeny could have occurred in the areas that handled and/or processed the monazite sand during the 

operational period. 

5.2.2 External Radiological Exposure Sources - W.R. Grace & Co. (MD) Operations 

The principal source of external exposure during the operational period was the direct exposure to 

uranium, thorium, and their progeny present in the monazite sands during milling and extraction 

operations. 

5.2.2.1 Photon

Thorium has a significant number of higher-energy photons in the Th-232 decay chain. Based on the 

half-lives of the progeny, only a partial equilibrium is possible; therefore, it is conservative to state 

that equilibrium would be reached in this decay chain. It has been assumed that Ra-228 and Th-228 

progeny were in equilibrium with Th-232. Therefore, air concentrations were assumed equal for all 

progeny. Under this assumption, the progeny are the major source of both penetrating and 

non-penetrating external exposure. 
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Table 5-1 shows the primary isotopes and photon energies associated with thorium and its progeny. 

Table 5-1: Principal Radiation Emissions from Th-232 and its Short-Lived Decay Products 

Radionuclide Half-life Beta Energy (MeV Max) Photon (x or γ) Energy (MeV) 

Th-232 1.405 x 1010 years None 0.059 (0.19%) 

0.126 (0.04%) 

Ra-228 5.71 years 0.389 (100%) 0.0067 (6 x 10-5%) 

Ac-228 6.25 hours 0.983 (7%) 0.338 (11.4%) 

1.014 (6.6%) 0.911 (27.7%) 

1.115 (3.4%) 0.969 (16.6%) 

1.17 (32%) 1.588 (3.5%) 

1.74 (12%) --- 

2.08 (8%) --- 

(+33 more βs) --- 

Th-228 1.9116 years 

None 

0.084 (1.19%) 

0.132 (0.11%) 

0.166 0.08%) 

0.216 (0.27%) 

Bi-212 60.55 minutes 1.59 (8%) 0.040 (1%) 

2.246 (48.4%) 0.727 (11.8$) 

--- 1.620 (2.75%) 

Tl-208 3.1 minutes 1.28 (25%) 0.277 (6%) 

1.52 (21%) 0.5108 (21.6%) 

1.80(50%) 0.583 (85.8%) 

--- 0.860 (12%) 

--- 2.614 (100%) 

Source: Handbook of Health Physics and Radiological Health (Rad Handbook, 1998). Intensities refer to the percentage 

of disintegrations of the nuclide itself, not to original parent of series. Gamma percents are given in terms of observable 

emissions, not transitions. 
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Table 5-2 shows the primary isotopes and photon energies associated with uranium. 

Table 5-2: Principal Radiation Emissions from Natural Uranium and Its Short-lived Decay Products 

Radionuclide Half-life Beta Energy (MeV Max) Photon (x or γ) Energy (MeV) 

U-238 4.468 x 109 years None x: 0.013 (8.8%) 

Th-234 24.1 days 0.096 (25%) x: 0.013 (9.6%) 

0.189 (73%) γ: 0.063 (3.8%) 

γ: 0.093 (5.4%)

Pa-234m 1.17 minutes 2.28 (98.6%) γ: 0.765 (0.2%)

~1.4 (1.4%) γ: 01.001 (0.6%)

U-235 7.038 x 109 years None x: 0.013 (31%) 

x: 0.090-0.105 (9.3%)

γ: 0.144 (10.5%)

γ: 0.163 (4.7%)

γ: 0.186 (54%)

γ: 0.205 (4.7%) 

Th-231 25.5 hours 0.206 (15%) x: 0.013 (71%)

0.288 (49%) γ: 0.026 (14.7%)

0.305 (35%) γ: 0.084 (6.4%)

U-234 244,500 years None x: 0.013 (10.5%)

γ: 0.053 (0.2%) 

Source: Handbook of Health Physics and Radiological Health (Rad Handbook, 1998). Intensities refer to the 

percentage of disintegrations of the nuclide itself, not to original parent of series. Gamma percents are given in terms of 

observable emissions, not transitions. 

5.2.2.2 Beta

Tables 5-1 and 5-2 show the principal beta emitters and their energies for the thorium and uranium 

present in monazite sands. As indicated in these tables, there are a significant number of high-energy 

beta radiations that represent a shallow dose exposure concern for site workers. Workers who handled 

monazite and the refined thorium could have received shallow dose exposures. The primary exposure 

areas would have been the hands and forearms, the neck and face, and other areas of the body that 

might not have been covered. 

5.2.2.3 Neutron

Neutrons were not measured at W.R. Grace (Maryland) and were not expected to be an exposure 

source for the class under evaluation. However, neutrons could arise from the α-n reaction with light 

elements, interactions with the oxides, and through spontaneous fission. According to Battelle-TBD6000, uranium oxides would be the most common generators of (α,n) reactions. Spontaneous fission 

yields and (α,n) yields in oxides are provided in Table 3.5 of Battelle-TBD-6000. Based on its 

analysis, NIOSH concludes that none of these sources would be sufficient to result in a significant 

neutron exposure and, therefore, are not further assessed in this evaluation. 
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6.0 Summary of Available Monitoring Data for the Class Evaluated 

by NIOSH 

The following subsections provide an overview of the state of the available internal and external 

monitoring data for the W.R. Grace and Company (Maryland) class under evaluation. 

6.1 Available W.R. Grace and Company (Maryland) Internal Monitoring Data 

Internal monitoring data are not available for workers at W.R. Grace and Company (Maryland). 

Process radiological monitoring data and source term data are also not available for the operational 

period from January 1, 1955 through December 31, 1958. 

For the residual period, site characterization data from the Curtis Bay site are available starting in 

1986, collected under the Formerly Utilized Sites Remedial Action Program (FUSRAP). In addition, 

air monitoring data are available for monazite ore-processing operations at the Rare Earths / W.R. 

Grace monazite-processing facility located in Wayne, New Jersey. These datasets are summarized 

below. 

6.1.1 Bldg. 23 - Site Characterization Data from W.R. Grace, Curtis Bay - 1986 

The W.R. Grace site at Curtis Bay was slated for further investigation as a result of a 1979 aerial 

survey conducted by the Department of Energy (Aerial Survey, 1979). The subsequent 

characterization survey was performed in October and December of 1986 by the Health and Safety 

Research Division (HASRD) of the Oak Ridge National Laboratory (ORNL) under the FUSRAP 

program (Cottrell, 1989). A summary of surface contamination (both direct and removable), airborne 

radioactivity, and dust sample measurements found in Building 23 are contained in Tables 6-1, 6-2, 

6-3, and 6-4 below. 

Table 6-1: Summary of Direct and Removable Alpha Surface Contamination Data – Curtis Bay 

(collected in Building 23 by ORNL HASRD in Oct. and Dec. 1986) 

Location Count 

Total Surface Activity 

(gross alpha, dpm/100 cm2) 

Removable Surface Activity 

(gross alpha, dpm/100 cm2) 

Min Max Average Min Max Average 

1st floor 4 7 120 49.75 ND ND ND 

2nd floor 2 140 840 490 3 3 3 

3rd floor 2 42 690 366 7 7 7 

4th floor 12 39 7800 

(200,000)a 842a 10 10 10 

5th floor 9 30 39,000 11,739 3 10 6.8 

Source: Cottrell, 1989 

a

 A measurement of 200,000 dpm/100 cm2 was collected inside ductwork and was not included in the 

calculated average. The next highest value was 7800 dpm/100 cm2

. 
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Table 6-2: Summary of Rn-220 and Rn-222 Air Activity Data – Curtis Bay 

(collected in Building 23 by ORNL HASRD in Oct. and Dec. 1986)

Location Count Rn220 (pCi/L) Rn222 (WL) 

Min Max Average Min Max Average 

1st floor 

2 0.01 0.03 0.02 <0.001 <0.001 <0.001 

2nd floor 

3 0.03 0.05 0.04 <0.001 <0.001 <0.001 

3rd floor 

6 0.06 1.6 0.75 <0.001 <0.001 <0.001 

4th floor 

3 0.04 0.2 0.1 <0.001 <0.001 <0.001 

5th floor 

6 0.02 12 3.668 <0.001 <0.001 <0.001 

Source: Cottrell, 1989 

Table 6-3: Summary of Th-232 Air Activity Data – Curtis Bay 

(collected in Building 23 by ORNL HASRD in Oct. and Dec. 1986)

Location Count Th-232 (mCi/ml) 

Min Max Average 

4th floor 

2 5.00E-14 1.1E-13 8.00E-14 

5th floor 

2 1E-13 1E-13 1E-13 

Source: Cottrell, 1989 

Table 6-4: Summary of Th-232 and U-238 Concentration Data in Building Dust – Curtis Bay 

(collected in Building 23 by ORNL HASRD in Oct. and Dec. 1986)

Location Count Th-232 (pCi/g) U-238 (pCi/g) % Th-232 

Min Max Average Min Max Average 

1st floor 

1 5.4 5.4 5.4 2 2 2 73% 

4th floor 

4 1.8 26 9.9 0.64 2 0.89 92% 

5th floor 

3 1.2 11 6.5 0.41 1.8 1.27 84% 

Source: Cottrell, 1989 
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FUSRAP Data for W.R. Grace and Company in Curtis Bay, MD - 2000-2001

A second set of characterization data was collected during a site remedial investigation conducted by 

the U.S. Army Corps of Engineers under FUSRAP from June 2000 through May 2001 (Army Corps, 

2002). This investigation included more than 1.9 million measurements using a surface contamination 

monitor (SCM) system, 2520 beta/gamma exposure measurements, 44 in situ gamma spectroscopy 

measurements, 84 supplemental alpha/beta measurements, and 543 surface wipes. A total of 24 cores 

were collected in Building 23, 19 of which were collected from the floor slabs and five on the asphalt 

roof. For the purpose of the survey, the building was broken into 11 Areas of Concern (AOC). Table 

6-5 provides a summary of the surface contamination data reported for AOCs 1-9. Surface 

contamination measurements were not performed in AOC 10 and 11. 

Table 6-5: FUSRAP Area of Concern (AOC) Designations – Curtis Bay 

(collected in Building 23 by U.S. Army Corps of Engineers during June 2000 through May 2001)

AOC Floor Survey Type Total Area Surveyed 

(m2) 

Maximum Activity (total) 

(dpm/100 cm2) 

1 1 Floors 3.2 5795 

2 1 Lower Walls 14.3 3269 

3 1 Lower Walls 16.1 4975 

4 2 Floors 44.4 3339 

5 3 Floors 1.1 865 

6 3 Floors 59.6 2914 

Lower Walls 9.3 2559 

Upper Walls 5.4 1956 

Ceilings 1.3 26843 

7 3 Floors 8.6 6184 

Lower Walls 19.3 2979 

Upper Walls 3.6 3320 

8 4 Floors 343 13571 

Lower Walls 6.5 11311 

Ceilings 1.6 16547 

Columns 4.9 3115 

9 5 Floors 290.7 52114 

Lower Walls 13.3 1618 

Ceilings 33.7 11496 

Columns 2.9 1464 

Source: Army Corps, 2002 
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6.1.2 Air Monitoring Data from W.R. Grace / Rare Earths in Wayne, NJ 

Air monitoring data are available for the W.R. Grace site in Wayne, New Jersey (formerly owned by 

Rare Earths, Inc.) during the period in which monazite ore was processed there. Two measurements 

were collected during an AEC inspection in 1959 at the location of the feeder hopper and the ball mill. 

Results indicated a general area air concentration of 1 x 10-10 μCi/ml and 1.89 x 10-11μCi/ml, 

respectively (Inspection, 1961, pdf p. 368). Additional air monitoring data were collected by W.R. 

Grace in 1961 (Survey, 1961) and are summarized in Table 6-6 below. 

Table 6-6: Air Monitoring Data - W.R. Grace, Wayne NJ Facility 

(collected by W.R. Grace in 1961)

Location Result (alpha/100 ft3

 of air) 

μCi/ml 

Shipping Room 3.7 x 10 -12 

Pulverizing Room 1.8 x 10 -12

Calcining Furnace 1.6 x 10 -12

Thorium Refining 4.1 x 10 -12

Thorium Crystallizer 1.3 x 10 -11

Process Storage 5.4 x 10 -12

Ball Mill 2.9 x 10 -11

Monazite Storage 1.0 x 10 -11

Lunch Room 1.1 x 10 -12

Kettle Area 2.7 x 10 -12

Control Lab 2.3 x 10 -12

Source: Survey, 1961, pdf p. 378 

6.1.3 Radioactive Waste Disposal Area (RWDA) Site Characterization 

Soil Sample Data

Limited radiological characterization of the on-site RWDA was conducted starting in 1978; however, 

results were reported only for Th-232 (Shaw, 1978). 

The most extensive site survey, conducted in 1999, was performed as part of the CERCLA Remedial 

Investigation (Building 23 Remedial Investigation, 2002). A total of 115 soil samples and 38 

groundwater samples (including total and dissolved aliquots) were collected for laboratory analysis. 

The samples were submitted to the laboratory for analysis of Target Compound List (TCL) VOCs, 

semi-volatile organic compounds (SVOCs), pesticides/polychlorinated biphenyls (PCBs), Target 

Analyte List (TAL) inorganic compounds (metals and cyanide), grain size, rare earth metals, and 

radiological parameters. 
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Table 6-7 provides a summary of the average measured concentrations as well as the associated 95% 

confidence level. 

Table 6-7: Soil Concentration Within RWDA 

Radionuclide 

Concentration (pCi/g) 

Average 

Avg. at 95% Confidence 

Level 

Ra-226 10.07 18.63 

Ra-228 18.91 34.81 

Th-228 7.28 11.73 

Th-230 3.13 4.37 

Th-232 6.19 10.19 

U-233/234 2.74 3.52 

U-238 2.66 3.4 

Source: RWDA Remedial Investigation Vol. 1, 2001, Table 6-3 

Sample analysis included gamma spectroscopy, alpha spectroscopy (isotopic uranium and thorium) as 

well as Ra-226 and Ra-228 analysis. Results of isotopic analysis for Th-228 and Th-232 are shown in 

Table 6-8 (only the most elevated samples are shown). 

 

Table 6-8: Th-228 and Th-232 Isotopic Analysis Results 

Sample Location Radionuclide Conc. (pCi/g) 

Th-228 Th-232 

B75-SO-SPLIT 5.78 6.52 

BO03-SO-02 3.31 3.51 

B07-SO-02 17 19.8 

B08-SO-02 34.3 47.8 

B18-SO-02 7.54 8.64 

B24-SO-02 5.45 6.41 

B30-SO-02 71.3 73.9 

B32-SO-02 26.7 31.9 

B36-SO-02 2.37 2.73 

B70-SO-04 1.55 1.93 

SO-DUP-02 30.1 34 

B18-SO-02 5.96 7.56 

Source: RWDA Remedial Investigation Vol. 1, 2001, Table 5-5 
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Air Monitoring Data

Air samples were collected during the performance of site characterization efforts. The results of 

these samples (based on gross alpha and beta analysis) are summarized in Table 6-9. 

Table 6-9: Air Monitoring Data Collected During RWDA Sampling/Site Investigation 

Location Gross Alpha (μCi/ml)a Gross Beta (μCi/ml) 

Low High Average Low High Average 

RWDA-Cont. Reduction Zone 1.22E-15 3.63E-15 1.97E-15 1.73E-14 3.74E-14 2.83E-14 

EA Trailer 1.76E-15 2.90E-15 2.22E-15 2.50E-14 4.90E-14 3.84E-14 

Analytical Lab Room 1.66E-15 2.90E-15 2.18E-15 2.38E-14 4.95E-14 3.61E-14 

a

 Statistics shown are for 13 weekly samples collected between July 27, 1999 and October 27, 1999. 

Source: RWDA Remedial Investigation Vol. 2, 2001, Appendix D, pdf p. 256 

6.2 Available W.R. Grace and Company (Maryland) External Monitoring Data 

6.2.1 W.R. Grace, Curtis Bay MD – Building 23 

NIOSH has found no external personnel monitoring results (including medical X-ray records) for the 

W.R. Grace (Maryland) operational period under evaluation (January 1, 1955 through December 31, 

1958). 

For the residual radiation period under evaluation, site characterization data from the Curtis Bay site 

(collected under the FUSRAP program) are available starting in 1986 and are summarized in Table 

6-10. 

Table 6-10: Average Gamma Dose Rates in Work Areas in Building 23 

(collected by ORNL HASRD in Oct. and Dec. 1986)

Location Average Gamma 

Exposure Rate 

(μR/hr) 

Maximum Gamma 

Exposure Rate at 1 m / 

contact (μR/hr) 

Maximum 

Beta/Gamma Dose 

Rate (mrad/hr) 

1st floor 50 54 / 160 0.04 

2nd floor 25 27 /81 

(120 inside tank) 

0.06 

3rd floor 29 54 / 110 0.06 

4th floor 40 680 / 490 

(2200 on overhead duct) 

15 (on duct) 

5th floor 120 270 / 570 

(1600 on duct) 

4.7 

Source: Cottrell, 1989 
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6.2.2 W.R. Grace Pompton Plains Facility (Wayne NJ) 

Survey data are available for the W.R. Grace, Wayne NJ facility whose operation predated those at the 

Curtis Bay, MD site. The Wayne facility was involved in thorium extraction operations similar to 

those at Curtis Bay and operated under the same AEC license as the Curtis Bay facility. Dose rates 

measured during a 1961 AEC inspection at the Wayne facility are shown in Table 6-11. 

Table 6-11: External Dose Survey of Wayne, NJ Facility 

Location Comments 

Restricted Area – Thorium Vault Maximum level: 10 mR/hr 

Average level: 3-4 mR/hr 

Ball Mill Area General radiation level: 2 mR/hr 

In contact with drum of yttrium sludge: 7.5 mR/hr 

At 1 ft. from the drum: 4 mR/hr 

In contact with drum containing ground monazite: 10 mR/hr 

At 1 ft. from this drum: 5 mR/hr 

Monazite Storage Area General radiation level: 5 mR/hr 

At 1 ft. from a bag containing monazite: 12 mR/hr 

Locker Room Area At 3 ft. above floor: 0.04 mR/hr 

Source: Inspection, 1961, pdf p. 368 
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6.2.3 Lindsay Light and Chemical Co., West Chicago, IL 

The Lindsay Light and Chemical Co. in West Chicago, IL, processed thorium ores starting in 1931, 

originally to extract thorium for gas mantles. Lindsay operations related to the processing of monazite 

ores and also involved the extraction of rare earth elements from these same ores. An extensive 

assessment of radiological conditions at the facility was conducted in 1953 by the Industrial Hygiene 

Branch of the AEC (Lindsay Light, 1953). This assessment included extensive external dose 

measurements within the facility as summarized in Table 6-12. 

Table 6-12: Summary of Radiation Measurements at Lindsay Light 

Material / Location Contact Exposure Rate (mR/hr) 

No. of Measurements Minimum Maximum Average 

Inside Plant 127 0.02 43 3.7 

Cerox Oxalate 2 0.2 0.2 0.2 

Gray Mud 1 20 20 20 

Monazite Bags 2 10 10 10 

R.E. Carbonate 2 0.7 0.7 0.7 

R.E. Flouride 2 0.08 0.08 0.08 

R.E. Hydrate 2 0.7 0.7 0.7 

Re2O3 1 0.5 0.5 0.5 

ThNO3 6 15 15 15 

ThO2 2 7 7 7 

Source: Lindsay Light, 1953, Table VII, pdf pp. 22-26 

Readings reported as “off scale” not included in this summary. 

6.2.4 Radioactive Waste Disposal Area (RWDA) Site Characterization 

The on-site RWDA was surveyed in 1978 by the Radiation Management Company. The survey 

consisted of external radiation measurements and surface and subsurface soil samples. External 

radiation levels were measured; results ranged from background to 17 mR/hr (Shaw 1978). 

An external radiation survey was conducted by ORNL in April and October, 1979. External radiation 

levels up to 50 μR/hr were measured three feet from the ground surface in the area outside the 

RWDA. External radiation levels inside the RWDA were reported to range upwards of 3 mR/hr 

(RWDA Remedial Investigation Vol. 1, 2001). 

During the characterization survey, a total of 46,407 data readings were collected for each of the 

survey instruments. The summary statistics resulting from the consolidated radiation survey data are 

listed in Table 6.13. 
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Table 6-13: Radiation Measurements Collected in the RWDA 

Minimum (μR/hr) Maximum (μR/hr) Mean (μR/hr) Std. Dev 

3.1 2292 48.3 104.9 

Source: RWDA Remedial Investigation Vol. 2, 2001, Appendix I, pdf p. 707 

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 ensure 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 7.5. 

This approach is discussed in DCAS’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-00182 as submitted by the petitioner. (Section 7.4) 
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7.1 Pedigree of W.R. Grace and Company (Maryland) 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. 

As described in Section 6.0, NIOSH was unable to locate any data directly from W.R. Grace and 

Company. Air sample data from a very similar process occurring at the W.R. Grace facility in Wayne, 

NJ are available and have been used in this evaluation. The data were evaluated against OCAS-IG004, “The Use of Data from Other Facilities in the Completion of Dose Reconstructions under the 

Energy Employees Occupational Illness Compensation Program Act” (OCAS-IG-004). 

 

The work performed at W.R. Grace and Company was very similar to the work performed at the W.R. 

Grace facility in New Jersey and the two facilities shared a single AEC contract and received the same 

materials from the AEC to process. The data have been determined to be appropriate for the purposes 

of bounding W.R. Grace and Company internal radiation exposures for the beginning of the residual 

period. Similarly the data pedigree (i.e., the background, history, origin, etc.) of the surrogate data 

sources used for this evaluation have been determined to be adequate to support the use of the 

methodology outlined in ORAUT-OTIB-0070 for the residual period. 

7.1.1 Internal Monitoring Data Pedigree Review 

Operational Period

NIOSH did not locate any internal monitoring data for the operational period under evaluation 

(January 1, 1955 through December 31, 1958). Therefore, a data sufficiency and pedigree evaluation 

is not possible for this data type for this period. 

Residual Period

NIOSH has determined that it has sufficient internal data of high pedigree for the residual 

radioactivity period. Radiological survey data collected by AEC representatives and the plant health 

physicist are available from the operational period at facilities with operations similar to Curtis Bay. 

In addition, data collected under the FUSRAP program are available, which include isotopic analysis 

results for sampling and surveys performed during the residual period. The data sources are copies of 

original reports and are, therefore, primary data sources. The data collection by AEC representatives 

would have been performed in accordance with standard practices using state-of-the-art methods of 

the day; furthermore, the FUSRAP program has a rigorous Quality Assurance program governing its 

methodologies. 

7.1.2 External Monitoring Data Pedigree Review 

Operational Period
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NIOSH did not locate any external monitoring data for the operational period under evaluation 

(January 1, 1955 through December 31, 1958). Therefore, a data sufficiency and pedigree evaluation 

is not possible for this data type for this period.

Residual Period

NIOSH has determined that it has sufficient external data of high pedigree for the residual 

radioactivity period. Radiological survey data collected by AEC representatives are available for the 

period preceding the end of the operational period. In addition, data collected under the FUSRAP 

program are available, which include isotopic analysis results for sampling and surveys performed 

during the residual period. The data sources are copies of original reports and are, therefore, primary 

data sources. The data collected by AEC representatives would have been performed in accordance 

with standard practices using state-of-the-art methods of the day; furthermore, the FUSRAP program 

has a rigorous Quality Assurance program governing its methodologies. 

7.2 Evaluation of Bounding Internal Radiation Doses at W.R. Grace (MD) 

The principal source of internal radiation doses for members of the class under evaluation was 

inhalation and ingestion of uranium- and thorium-laden dust generated during the processes employed 

for thorium extraction, particularly during dry product-handling evolutions. 

7.2.1 Evaluation of Bounding Process-Related Internal Doses 

Internal monitoring data, work area radiological monitoring data, and source term data are not 

available to support the assessment of internal dose at the W.R. Grace (Maryland) site. NIOSH has 

determined there were no potential internal radiological exposures at the Curtis Bay site before 

construction completion on May 1, 1956. NIOSH has also determined that AEC-related operations 

had ceased by the end of January 1958; work performed after this date is included in the residual 

radiation period assessment. Therefore, NIOSH finds that internal doses to personnel during the 

operational period from May 1, 1956 through January 31, 1958 cannot be bounded, and therefore, 

accurately reconstructed. 

7.2.2 Evaluation of Bounding Residual Period Internal Doses 

During the effective residual period workers were potentially exposed to re-suspended surface 

contamination. Bounding residual period air concentrations can be based on measurements of air 

concentrations at similar facilities and knowledge of surface contamination levels within Building 23 

at Curtis Bay during the post-operations period. Internal exposure during work in the RWDA can be 

bounded using soil concentration data collected during site remedial investigation activities along with 

an estimate of the particulate concentration in the air. NIOSH has determined that this information 

can be used to bound internal dose during the effective residual period, which includes (1) the postoperational, technical residual period from February 1, 1958 through December 31, 1958; and (2) the 

original DOE-defined residual period from January 1, 1959 through October 31, 2009. 

7.2.3 Methods for Bounding Internal Dose at W.R. Grace and Company (Maryland) 
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7.2.3.1 Methods for Bounding Operational Period Internal Dose

Internal monitoring data, work area radiological monitoring data, and source term data are not 

available. Therefore, NIOSH finds that internal doses to personnel during the operational period from 

May 1, 1956 through January 31, 1958 cannot be bounded, and therefore, accurately reconstructed. 

7.2.3.2 Methods for Bounding Residual Period Internal Dose 

Building 23

Internal exposure during the residual period can be bounded using the methodology in ORAUTOTIB-0070. In this methodology, air concentrations at the beginning and end of a time period are 

used with an assumption of an exponential relationship to calculate exposure rates for intervening time 

periods. 

The general area air sample results reported at the W.R. Grace, Wayne NJ facility (Table 6-6) during 

air monitoring studies conducted in 1961 were used as an estimate of the air concentration at the start 

of the residual period. In order to do this, the data in Table 6-6 were fit to a lognormal distribution 

and the geometric mean and standard deviation were calculated. The resultant distribution had a 

geometric mean of 4.14 x 10 -12

μCi/ml with a GSD of 2.70. This air concentration (4.14 x 10 -12

μCi/ml), which corresponds to an intake rate of 27 pCi/calendar day, would represent an upper bound 

of the level of airborne contamination present at the cessation of operations, which corresponds to the 

beginning of the residual period. 

Surface concentration values calculated for the Curtis Bay facility (Table 6-5) can be used to establish 

a bounding estimate of the air activity at the time of these measurements (i.e., 2000). The weighted 

average of the maximum reported floor surface activity of 27,000 dpm/100cm2, can be used to 

represent the bounding surface contamination present within the facility for the purpose of performing 

these re-suspension calculations. Using a re-suspension factor of 1 x 10-6, a predicted air 

concentration of 1.2 x 10-12μCi/ml is equivalent to an intake rate of 8 pCi/calendar day, which would 

correspond to the 27,000 dpm/100 cm2 surface contamination level. The 1 x 10-6 re-suspension factor 

is bounding given the fact that (1) the measured surface contamination levels represent total activity 

and the amount of removable contamination is a very small fraction of that value; and (2) the 

predicted air concentration (1.2 x 10-12

μCi/ml) is greater than the maximum measured air 

concentration measured during the 1986 survey (see Table 6-3). 

The intake rates indicated above were used to calculate an exponential rate constant relating the two 

values, separated by a time period of 42 years (1958 to 2000). The decay constant is calculated as 

0.029 yr-1 and is used to adjust the intake rates in Table 7-1 to account for the reduction in the intake 

rate over time. 

Consideration of exposure to uranium, which is also present in monazite sands, could be included 

based on the relative fraction of thorium within the process material. Based on data collected during 

the remedial investigation (Table 6-4), the average Th-232 component is 83% of the total gross 

activity (based on Th-232 and U-238). This activity fraction (0.83) is used to calculate the thorium 
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intakes shown in Table 7-1. Internal exposure from ingestion would be bounded based on the 

calculated inhalation intake using the methodology in OCAS-TIB-009. 

Internal exposure to radon (Rn-222) and thoron (Rn-220) can be bounded using data collected during 

the 1986 building survey. The average thoron concentration (based on the 20 samples collected) was 

1.15 pCi/l and the radon concentration was consistently < 0.001 WL. Exposure to thoron and radon 

can be bounded using air concentrations of 1.15 pCi/L and 0.001 WL, respectively, as the basis for the 

1986 intake, and by applying the depletion relationship detailed above to determine intakes in prior 

years. Since these values are based on average concentrations, they may be assigned as the median 

value of a lognormal distribution with a GSD of 5. 

Table 7-1: Residual Period Inhalation and Ingestion Intakes – Bldg. 23 

(This table spans two pages)

Year Uranium (pCi/calendar day) Thorium (pCi/calendar day) Thoron 

(pCi/L) 

Radon 

Inhalation Ingestion Inhalation Ingestion (WL) 

1958 4.6E+00 9.6E-02 2.3E+01 4.7E-01 2.6E+00 2.3E-03 

1959 4.5E+00 9.4E-02 2.2E+01 4.6E-01 2.5E+00 2.2E-03 

1960 4.4E+00 9.1E-02 2.1E+01 4.4E-01 2.5E+00 2.1E-03 

1961 4.2E+00 8.8E-02 2.1E+01 4.3E-01 2.4E+00 2.1E-03 

1962 4.1E+00 8.6E-02 2.0E+01 4.2E-01 2.3E+00 2.0E-03 

1963 4.0E+00 8.3E-02 2.0E+01 4.1E-01 2.3E+00 2.0E-03 

1964 3.9E+00 8.1E-02 1.9E+01 3.9E-01 2.2E+00 1.9E-03 

1965 3.8E+00 7.9E-02 1.8E+01 3.8E-01 2.1E+00 1.8E-03 

1966 3.7E+00 7.6E-02 1.8E+01 3.7E-01 2.1E+00 1.8E-03 

1967 3.6E+00 7.4E-02 1.7E+01 3.6E-01 2.0E+00 1.7E-03 

1968 3.5E+00 7.2E-02 1.7E+01 3.5E-01 1.9E+00 1.7E-03 

1969 3.4E+00 7.0E-02 1.6E+01 3.4E-01 1.9E+00 1.6E-03 

1970 3.3E+00 6.8E-02 1.6E+01 3.3E-01 1.8E+00 1.6E-03 

1971 3.2E+00 6.6E-02 1.5E+01 3.2E-01 1.8E+00 1.6E-03 

1972 3.1E+00 6.4E-02 1.5E+01 3.1E-01 1.7E+00 1.5E-03 

1973 3.0E+00 6.2E-02 1.5E+01 3.0E-01 1.7E+00 1.5E-03 

1974 2.9E+00 6.0E-02 1.4E+01 2.9E-01 1.6E+00 1.4E-03 

1975 2.8E+00 5.9E-02 1.4E+01 2.9E-01 1.6E+00 1.4E-03 

1976 2.7E+00 5.7E-02 1.3E+01 2.8E-01 1.5E+00 1.3E-03 

1977 2.7E+00 5.5E-02 1.3E+01 2.7E-01 1.5E+00 1.3E-03 

1978 2.6E+00 5.4E-02 1.3E+01 2.6E-01 1.5E+00 1.3E-03 

1979 2.5E+00 5.2E-02 1.2E+01 2.5E-01 1.4E+00 1.2E-03 

1980 2.4E+00 5.1E-02 1.2E+01 2.5E-01 1.4E+00 1.2E-03 

1981 2.4E+00 4.9E-02 1.2E+01 2.4E-01 1.3E+00 1.2E-03 

1982 2.3E+00 4.8E-02 1.1E+01 2.3E-01 1.3E+00 1.1E-03 

1983 2.2E+00 4.6E-02 1.1E+01 2.3E-01 1.3E+00 1.1E-03 

1984 2.2E+00 4.5E-02 1.1E+01 2.2E-01 1.2E+00 1.1E-03 

1985 2.1E+00 4.4E-02 1.0E+01 2.1E-01 1.2E+00 1.0E-03 

1986 2.1E+00 4.4E-02 1.0E+01 2.1E-01 1.2E+00 1.0E-03 

1987 2.0E+00 4.3E-02 1.0E+01 2.1E-01 1.2E+00 1.0E-03 

1988 2.0E+00 4.1E-02 9.7E+00 2.0E-01 1.2E+00 1.0E-03 

1989 1.9E+00 4.0E-02 9.4E+00 2.0E-01 1.2E+00 1.0E-03 

1990 1.9E+00 3.9E-02 9.1E+00 1.9E-01 1.2E+00 1.0E-03 

1991 1.8E+00 3.8E-02 8.9E+00 1.8E-01 1.2E+00 1.0E-03 

1992 1.8E+00 3.7E-02 8.6E+00 1.8E-01 1.2E+00 1.0E-03 
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Table 7-1: Residual Period Inhalation and Ingestion Intakes – Bldg. 23 

(This table spans two pages)

Year Uranium (pCi/calendar day) Thorium (pCi/calendar day) Thoron 

(pCi/L) 

Radon 

Inhalation Ingestion Inhalation Ingestion (WL) 

1993 1.7E+00 3.6E-02 8.4E+00 1.7E-01 1.2E+00 1.0E-03 

1994 1.7E+00 3.5E-02 8.1E+00 1.7E-01 1.2E+00 1.0E-03 

1995 1.6E+00 3.4E-02 7.9E+00 1.6E-01 1.2E+00 1.0E-03 

1996 1.6E+00 3.3E-02 7.7E+00 1.6E-01 1.2E+00 1.0E-03 

1997 1.5E+00 3.2E-02 7.4E+00 1.5E-01 1.2E+00 1.0E-03 

1998 1.5E+00 3.1E-02 7.2E+00 1.5E-01 1.2E+00 1.0E-03 

1999 1.4E+00 3.0E-02 7.0E+00 1.5E-01 1.2E+00 1.0E-03 

2000 1.4E+00 2.9E-02 6.8E+00 1.4E-01 1.2E+00 1.0E-03 

2001 1.4E+00 2.8E-02 6.6E+00 1.4E-01 1.2E+00 1.0E-03 

2002 1.3E+00 2.7E-02 6.4E+00 1.3E-01 1.2E+00 1.0E-03 

2003 1.3E+00 2.7E-02 6.2E+00 1.3E-01 1.2E+00 1.0E-03 

2004 1.2E+00 2.6E-02 6.1E+00 1.3E-01 1.2E+00 1.0E-03 

2005 1.2E+00 2.5E-02 5.9E+00 1.2E-01 1.2E+00 1.0E-03 

2006 1.2E+00 2.4E-02 5.7E+00 1.2E-01 1.2E+00 1.0E-03 

2007 1.1E+00 2.4E-02 5.6E+00 1.2E-01 1.2E+00 1.0E-03 

2008 1.1E+00 2.3E-02 5.4E+00 1.1E-01 1.2E+00 1.0E-03 

2009 1.1E+00 2.2E-02 5.2E+00 1.1E-01 1.2E+00 1.0E-03 

a

 Uranium intake should be assigned as 100% U-234. 

b

 Thorium intake should be assigned at indicated rate to each of Th-232, Th-228, and Ra-228. 

Note: Values should be input as a constant distribution because they are based on 95th percentile values. 

Radioactive Waste Disposal Area (RWDA)

A bounding estimate for potential internal exposure within the on-site RWDA during the residual 

period was developed using the dust-loading methodology described in ORAUT-OTIB-0070, Section 

2.1.3. In this methodology, an ambient air dust loading of 100 μg/m3 is used along with soil 

concentration data to determine the potential air concentrations during the residual period. Inhalation 

intake rates were developed using the 95 percent confidence internal soil concentration data reported 

in the remedial investigation report (see Table 6-7); the calculation results are shown below in Table 

7-2. Intakes due to ingestion may be determined by multiplying by the factor 0.021 (based on the 

methodology contained in OCAS-TIB-009). 

Table 7-2: Inhalation Intake Rates Based on Source Concentration Data 

Radionuclide Inhalation Intake 

(pCi/calendar day) 

Ra-226 1.2E-02 

Ra-228 2.3E-02 

Th-228 7.7E-03 

Th-230 2.9E-03 

Th-232 6.7E-03 

Uranium 4.6E-03 
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Because the disposal area was dormant during the duration of the residual period and the 

contamination present was due to bulk material (i.e., not surface-deposited), no decrease in the source 

term inventory was applied. However, because the disposed material was concentrated in Ra-228, and 

owing to the parent-daughter relationship between Ra-228 and Th-228, it is necessary to make an 

adjustment to account for the likely presence of a larger concentration of these nuclides at the time of 

disposal. The general relationship between the parent-daughter concentrations is shown in the 

following equation: 

( ) λ −λ −λ −λ = −+

λ −λ

1 0t t 0 1 2

21 2

2 1

N Ne e N 2t e

Where: 

N1

0 = the number of parent atoms at time t = 0 

N1

 = the number of parent atoms at time t 

N2 = the number of daughter atoms at time t 

λ1 = decay constant for the parent nuclide – determined by dividing the natural log of two by 

the half-life of the isotope 

λ2 = decay constant for the daughter nuclide - determined by dividing the natural log of two by 

the half-life of the isotope 

e = Euler’s number (a constant) generally approximated to be 2.71828...) [unitless] 

t = time 

The above parent-daughter relationship was employed along with the assumption that the excess 

Th-228 present at the time of the 1999 remedial investigation (i.e., the Th-232 concentration minus the 

Th-228 concentration) was due entirely to Ra-228 that was present 41 years earlier. This equation 

was first solved to determine the Ra-228 concentration present in 1958 that would yield a unit activity 

of Th-228. The calculated Ra-228 concentration was then used to calculate the Th-228 in-growth over 

time. These relationships were then used to adjust the Th-228 and Ra-228 inhalation intake quantities 

shown above in Table 7-2. The results of this assessment, shown below in Table 7-3, could be used to 

bound internal exposure during the residual period. As previously noted, ingestion intakes can be 

determined by applying a multiplier of 0.21 to the inhalation intake quantity. Note that because 

RWDA access was restricted starting in 1978, intakes are calculated for the period 1958 to 1978 only. 

Internal exposure is assumed to be zero after this time due to the restricted access. 

However, for most workers at the W.R. Grace and Company facility it will be difficult to determine 

the exact work location and in such cases, inhalation intakes presented in Table 7-1 should be 

assigned, since the residual doses from process operations would be bounding. 
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Table 7-3: Residual Period Inhalation Intakes (RWDA) 

Year 

Inhalation Intake 

(pCi/calendar day) 

Ra-228 Th-228 Th-230 Th-232 Ra-226 Uranium 

1958 1.1E-01 2.3E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1959 1.0E-01 4.6E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1960 9.5E-02 6.0E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1961 8.7E-02 6.7E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1962 8.0E-02 7.0E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1963 7.3E-02 7.0E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1964 6.7E-02 6.8E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1965 6.2E-02 6.6E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1966 5.8E-02 6.3E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1967 5.4E-02 5.9E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1968 5.1E-02 5.6E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1969 4.7E-02 5.3E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1970 4.5E-02 5.0E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1971 4.2E-02 4.7E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1972 4.0E-02 4.5E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1973 3.8E-02 4.2E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1974 3.6E-02 4.0E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1975 3.5E-02 3.8E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1976 3.4E-02 3.7E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1977 3.2E-02 3.5E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

1978 3.1E-02 3.4E-02 2.9E-03 6.7E-03 1.2E-02 2.3E-03 

The air concentration corresponding to the intake quantities calculated in Table 7-2 (5E -15 μCi/ml) is 

slightly higher than air concentrations measured in 1999 during the remedial investigation (maximum 

value of 2E -15 μCi/ml), this indicating that the calculated intake is in fact bounding under conditions 

likely present during general site access. 
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7.2.4 Internal Dose Reconstruction Feasibility Conclusion 

Internal monitoring data, work area radiological monitoring data, and source term data are not 

available. Therefore, NIOSH finds that internal doses to personnel during the operational period from 

May 1, 1956 through January 31, 1958 cannot be bounded, and therefore, accurately reconstructed. 

NIOSH has determined that reconstruction of internal doses is feasible for the residual period using 

the assumptions and approaches presented within Section 7.2.2 of this report. The effective residual 

period includes: (1) the period from February 1, 1958 through December 31, 1958, which has been 

determined to be after the confirmed end of the operational period; and (2) the period from January 1, 

1959 through October 31, 2009, which is the residual period originally designated by DOE and for 

which dose reconstruction has been determined to be feasible. 

Although NIOSH found that it is not possible to completely reconstruct internal radiation doses for the 

operational period from May 1, 1956 through January 31, 1958, NIOSH intends to use any internal 

monitoring data that may become available for an individual claim (and that can be interpreted using 

existing NIOSH dose reconstruction processes or procedures). Dose reconstructions for individuals 

employed at W.R. Grace and Company during the period from May 1, 1956 through January 31, 

1958, but who do not qualify for inclusion in the SEC, may be performed using these data as 

appropriate. 

7.3 Evaluation of Bounding External Radiation Doses at W.R. Grace (MD) 

The principal source of external radiation doses for members of the evaluated class was direct 

exposure to uranium, thorium, and their progeny present in the monazite sands during milling and 

extraction operations. During the residual period, workers were potentially exposed to residual 

surface contamination. 

7.3.1 Evaluation of Bounding Process-Related External Doses 

NIOSH has not identified any external monitoring records or personal dosimetry data associated with 

the thorium processing that occurred during the operational period under evaluation. NIOSH has not 

been able to identify any radiological surveys or area monitoring data conducted during the 

operational period to support the assessment of external dose at the W.R. Grace (Maryland) site. 

NIOSH has determined that there were no potential external radiological exposures at the Curtis Bay 

site before construction completion on May 1, 1956. NIOSH has also determined that AEC-related 

operations had ceased by the end of January 1958; work performed after this date is included in the 

residual radiation period assessment. Therefore, NIOSH finds that external doses to personnel during 

the operational period from May 1, 1956 through January 31, 1958 cannot be bounded and, therefore, 

accurately reconstructed. 

7.3.2 Evaluation of Bounding Residual Period External Doses 

During the effective residual period, workers were potentially exposed to external radiation from 

residual surface contamination. Bounding residual period external dose estimates can be based on 

measurement of external dose rates at the Curtis Bay facility during the post-operations period. Data 

collected during the 1999 remedial investigation can be used to bound external exposure within the 
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RWDA (RWDA Remedial Investigation Vol. 1, 2001; RWDA Remedial Investigation Vol. 2, 2001). 

The effective residual period includes: (1) the post-operational, technical residual period from 

February 1, 1958 through December 31, 1958; and (2) the original DOE-defined residual period from 

January 1, 1959 through October 31, 2009. 

7.3.3 W.R. Grace and Company (Maryland) Occupational X-Ray Examinations 

No specific references could be found stating that X-rays or physical examinations were required at 

W.R. Grace and Company site at Curtis Bay. An interviewee stated that there were “no work-related 

X-rays done at the site” (Personal Communication, 2011a). A former W.R. Grace supervisor stated 

that physical examinations with X-rays were not begun until much later, possibly in the 1970s or 

1980s (Personal Communication, 2011b). Therefore, based on the documented evidence, NIOSH 

concludes that medical X-ray dose is not a consideration for W.R. Grace and Company (Maryland) 

workers and will not be discussed further in this evaluation. 

7.3.4 Methods for Bounding External Dose at W.R. Grace and Company 

7.3.4.1 Methods for Bounding Operational Period External Dose

NIOSH has not identified any external monitoring records or personal dosimetry data associated with 

the thorium processing conducted during the period under evaluation. Therefore, NIOSH has 

concluded that external doses for the operational period of May 1, 1956 through January 31, 1958 for 

W. R. Grace cannot be bounded. 

7.3.4.2 Methods for Bounding Residual Period External Doses 

Building 23

External radiation survey data first measured in 1986 (as discussed in Section 7.3.2) can be used to 

bound Building 23 external exposure from both penetrating and non-penetrating radiation. The 

surveys conducted over the time period under evaluation provide sufficient detail and coverage to be 

used for this purpose. Based on a review of the 1986 survey data, a penetrating dose rate of 0.6 

mR/hour would be bounding. Application of the depletion factor calculated in Section 7.2.3.2 (0.029 

yr

-1) would predict a penetrating dose rate of 1.4 mR/hr at the beginning of the residual period (i.e., 

1958). If needed, a non-penetrating radiation may be assumed to be equal to the penetrating dose rate. 

This would be a bounding assumption based on the nature of the source term and considering 

operational experience at other monazite ore facilities such as the Lindsay Light Chemical Co. 

(Klevin, 1953). This exposure rate compares favorably with external dose rates measured within 

operational monazite processing facilities, such as the W.R. Grace site in Wayne, NJ and the Lindsay 

Light site in West Chicago. Data from these sites, shown in Tables 6-11 and 6-12, are comparable, 

with levels only considerably higher on process equipment and materials that would not be present 

during the residual period. 
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Radioactive Waste Disposal Area (RWDA)

External dose rate measurements collected during the 1999 remedial investigation can be used to 

bound external exposure during the residual period (RWDA Remedial Investigation Vol. 1, 2001; 

RWDA Remedial Investigation Vol. 2, 2001). As was previously done for internal exposure, an 

annual adjustment was applied to 1999 data to account for the likely presence of elevated levels of 

Tl-208 in the RWDA (Tl-208 is in equilibrium with Th-228). The results of this calculation are 

shown below in Table 7-4. Exposure data are shown only until 1978 because RWDA access was 

restricted thereafter. 

Table 7-4: Adjusted External Dose Rates for the RWDA 

Year Dose Rate (mR/hr) 

Maximum Mean 

1958 2.0 0.042 

1959 8.9 0.188 

1960 12.9 0.272 

1961 15.0 0.317 

1962 15.9 0.335 

1963 15.9 0.335 

1964 15.5 0.326 

1965 14.7 0.310 

1966 13.8 0.291 

1967 12.9 0.271 

1968 11.9 0.251 

1969 11.0 0.231 

1970 10.1 0.212 

1971 9.3 0.195 

1972 8.5 0.179 

1973 7.8 0.165 

1974 7.2 0.151 

1975 6.6 0.139 

1976 6.1 0.129 

1977 5.7 0.119 

1978 5.2 0.111 
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7.3.5 External Dose Reconstruction Feasibility Conclusion 

NIOSH has concluded that sufficient data are not available to estimate a bounding external dose from 

the thorium handling and processing that occurred during the operational period from May 1, 1956 

through January 31, 1958. Therefore, NIOSH has determined that reconstruction of external doses for 

W.R. Grace (Maryland) workers is not feasible for the operational period from May 1, 1956 through 

January 31, 1958.

NIOSH has determined that reconstruction of external doses is feasible for the residual period using 

the assumptions and approaches presented within Section 7.3.4.2 of this report. The effective residual 

period includes: (1) the period from February 1, 1958 through December 31, 1958, which has been 

determined to be after the confirmed end of the operational period; and (2) the period from January 1, 

1959 through October 31, 2009, which is the residual period originally designated by DOE and for 

which dose reconstruction has been determined to be feasible. 

Although NIOSH found that it is not possible to completely reconstruct external radiation doses for 

the period from May 1, 1956 through January 31, 1958, NIOSH intends to use any external 

monitoring data that may become available for an individual claim (and that can be interpreted using 

existing NIOSH dose reconstruction processes or procedures). Dose reconstructions for individuals 

employed at W.R. Grace and Company (Maryland) during the period from May 1, 1956 through 

January 31, 1958, but who do not qualify for inclusion in the SEC, may be performed using these data 

as appropriate. 
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7.4 Evaluation of Petition Basis for SEC-SEC-00182 

The following assertion was made on behalf of petition SEC-00182 for the W.R. Grace and Company 

(Maryland) site. 

Monitoring Data Missing or Lost 

SEC-00182: All work performed at the W.R. Grace facility in Curtis Bay, MD, between 1953 – 1990 

was conducted without the use of dose monitoring equipment or all monitoring data was destroyed or 

missing. 

Operational Period

Internal monitoring data are not available for workers at W.R. Grace and Company (Maryland). 

Process radiological monitoring data and source term data are also not available for the operational 

period. Therefore, internal doses to personnel during the operational period cannot be bounded, and 

therefore, accurately reconstructed. 

NIOSH has found no external personnel monitoring results for the W.R. Grace operational period. 

NIOSH has concluded that sufficient data are not available to estimate a bounding external dose from 

the thorium handling and processing that occurred during the operational period. 

Residual Radiation Period

Site characterization data from the Curtis Bay site are available starting in 1986. In addition, air 

monitoring data are available during monazite ore-processing operations at the Rare Earths / W.R. 

Grace monazite-processing facility located in Wayne, New Jersey. NIOSH has determined that 

reconstruction of internal doses is feasible for the residual period using the assumptions and 

approaches presented within Section 7.2.2 of this report. 

Site characterization data from the Curtis Bay site are available starting in 1986. NIOSH has 

determined that reconstruction of external doses is feasible for the effective residual period using the 

assumptions and approaches presented within Section 7.3.4.2 of this report. The effective residual 

period includes: (1) the post-operational, technical residual period from February 1, 1958 through 

December 31, 1958; and (2) the original DOE-defined residual period from January 1, 1959 through 

October 31, 2009. 
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7.5 Summary of Feasibility Findings for Petition SEC-00182 

This report evaluates the feasibility for completing dose reconstructions for employees at W.R. Grace 

and Company from January 1, 1955 through December 31, 1958 (operational period), and from 

January 1, 1959 through October 31, 2009 (residual radiation period). NIOSH found that the 

available monitoring records, process descriptions and source term data available are not sufficient to 

complete dose reconstructions for the evaluated class of employees for the operational period. 

However, for the residual radiation period, NIOSH has determined that reconstruction of internal and 

external doses is feasible using the assumptions and approaches presented within this report. 

Table 7-5 summarizes the results of the feasibility findings at W.R. Grace and Company (Maryland) 

for each exposure source during the operational period (May 1, 1956 through January 31, 1958) and 

the effective residual radiation period. The effective residual period includes: (1) the period from 

February 1, 1958 through December 31, 1958, which has been determined to be after the confirmed 

end of the operational period; and (2) the period from January 1, 1959 through October 31, 2009, 

which is the residual period originally designated by DOE and for which dose reconstruction has been 

determined to be feasible. 

Table 7-5: Summary of Feasibility Findings for SEC-00182 

May 1, 1956 through January 31, 1958 (operations); 

February 1, 1958 through December 31, 1958 (technical residual period) 

January 1, 1959 through October 31, 2009 (original residual period) 

Source of Exposure 

May 1, 1956 through January 31, 

1958 (operations) 

February 1, 1958 through October 

31, 2009 (effective residual period2) 

Reconstruction 

Feasible 

Reconstruction 

Not Feasible 

Reconstruction 

Feasible 

Reconstruction 

Not Feasible 

Internal X X 

 - Uranium X X 

 - Thorium X X 

 - Thoron / Radon X X 

External X X 

 - Gamma X X 

 - Beta X X 

 - Neutron N/A N/A N/A N/A 

 - Occupational Medical X-ray1 N/A N/A N/A N/A 

1

 No medical X-rays were performed on site during the operational period. Medical X-rays are not considered during the 

residual period. 2 Effective residual period = technical residual period + original residual period. 
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As of April 28, 2011, a total of one claim has been submitted to NIOSH for an individual who worked 

at W.R. Grace and Company during the period under evaluation in this report. A dose reconstruction 

has been completed for this individual (100%). 

Although NIOSH found that it is not possible to completely reconstruct radiation doses for the 

proposed class, NIOSH intends to use any internal and external monitoring data that may become 

available for an individual claim (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures). Therefore, dose reconstructions for individuals employed at 

W.R. Grace and Company (Maryland) during the period from May 1, 1956 through January 31, 1958, 

but who do not qualify for inclusion in the SEC, may be performed using these data as appropriate. 

8.0 Evaluation of Health Endangerment for Petition SEC-00182 

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. 

Internal and external monitoring data are not available for the operational period. For the residual 

radiation period, site characterization data from the Curtis Bay site are available starting in 1986. In 

addition, air monitoring data are available from monazite ore-processing operations at the Rare Earths 

/ W.R. Grace monazite-processing facility located in Wayne, New Jersey. Based on the sum of 

information available from available resources, NIOSH’s evaluation determined that it is not feasible 

to estimate radiation dose with sufficient accuracy for members of the NIOSH-evaluated class for the 

time period from May 1, 1956 through January 31, 1958. Therefore, the resulting NIOSH-proposed 

SEC class must include a minimum required employment period as a basis for specifying that health 

was endangered for this time period. NIOSH further determined that it is feasible to estimate 

radiation dose with sufficient accuracy for members of the NIOSH-evaluated class for the time period 

from February 1, 1958 through October 31, 2009. Therefore, a health endangerment determination is 

not required for this time period. 
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9.0 Class Conclusion for Petition SEC-00182 

Based on its full research of the class under evaluation, NIOSH has defined a single class of 

employees for which NIOSH cannot estimate radiation doses with sufficient accuracy. The NIOSHproposed class to be added to the SEC includes all Atomic Weapons Employees who worked at any 

building or area at the facility owned by W.R. Grace and Company in Curtis Bay, Maryland, for the 

operational period from May 1, 1956 through January 31, 1958, for a number of work days 

aggregating at least 250 work days, occurring either solely under this employment, or in combination 

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

Special Exposure Cohort. 

NIOSH has determined that it is feasible to estimate radiation dose with sufficient accuracy for 

members of the NIOSH-evaluated class for the effective residual radiation period based on available 

site characterization data and data from sites performing similar work. The effective residual period 

includes: (1) the period from February 1, 1958 through December 31, 1958, which has been 

determined to be after the confirmed end of the operational period; and (2) the period from January 1, 

1959 through October 31, 2009, which is the residual period originally designated by DOE. 

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-00182. 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 

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 the feasibility or infeasibility of reconstructing dose for the 

class under evaluation. 
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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 

Aerial Survey, 1979, An Aerial Radiological Survey of the Curtis Bay Facility of the W.R. Grace 

Company, Baltimore, Maryland, L. K. Hilton, The Remote Sensing Laboratory of the U.S. 

Department of Energy; November 1979; SRDB Ref ID: 7181 

Army Corps, 2002, Draft Final Feasibility Study of Building 23 at the W.R. Grace Curtis Bay 

Facility, Baltimore, Maryland; United States Army Corps of Engineers; July 2002; SRDB Ref ID: 

43458 

Battelle-TBD-6000, Site Profiles for Atomic Weapons Employers that Worked Uranium and Thorium 

Metals, PNWD-3738, Rev F0; Battelle; December 13, 2006; SRDB Ref ID: 30671 

Building 23 Remedial Investigation, 2002, Remedial Investigation (RI) Report of Building 23 at the 

W.R. Grace Curtis Bay Facility, Baltimore, Maryland, U.S. Army Corps of Engineers, Baltimore 

District, April, 2002; SRDB Red ID: 97409 

Contracts and Amendments, 1950s, Contracts and Amendments AT(49-6)-993 and AT(30-1)-1037, 

contractual documents and related letters between the U.S. Atomic Energy Commission and W.R. 

Grace & Co.; various dates and signatories in the 1950s; SRDB Ref ID: 69221 

Cottrell, 1989, Results of the Indoor Radiological Survey at the W.R. Grace Co., Curtis Bay Site, 

Baltimore, Maryland, ORNL/TM-10439; W. D. Cottrell, R. D. Foley, and C. A. Johnson, Oak Ridge 

National Laboratory; issued July 1989; SRDB Ref ID: 7188 

DCAS-PR-004, Internal Procedures for the Evaluation of Special Exposure Cohort Petitions, Rev. 1, 

National Institute for Occupational Safety and Health (NIOSH); Cincinnati, Ohio; April 15, 2011; 

SRDB Ref ID: 94768 
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Designation Summary, date unknown, Designation Summary: W.R. Grace & Company, Davison 

Chemical Division, Curtis Bay, MD, author unknown, but from context, like U.S. Department of 

Energy; data unknown, but from context, after 1984; SRDB Ref ID: 70416 

Feasibility Study, 2003, Final Feasibility Study (FS) of Building 23 at the W.R. Grace Curtis Bay 

Facility, Baltimore, Maryland; U.S. Army Corps of Engineers, Baltimore District; February 2003; 

SRDB Ref ID: 43512 

FUSRAP documents, various dates, Various Documents Related to the Formerly Utilized Sites 

Remedial Action Project (FUSRAP) Effort at the W.R. Grace Site at Curtis Bay, Maryland; some 

documents undated, others in 1970s or 1980s; SRDB Ref ID: 7251 

Inspection, 1961, Part 40 Inspection; date of inspection was June 29, 1961; SRDB Ref ID: 41327, pdf 

pp. 366-373 

Johnson, 1958, Thorium Procurement, office memorandum R. W. Cook from J. C. Johnson (U.S. 

Atomic Energy Commission); January 23, 1958; SRDB Ref ID: 70389 

Klevin, 1953, Lindsay Chemical Company Industrial Hygiene Survey Part I Occupational Exposure 

to Thorium Dust and Thoron; Paul B. Klevin and James Fresco; January 21, 1953; SRDB Ref ID: 

9085 

Lindsay Light, 1953, Lindsay Light Company Industrial Hygiene Survey, Part I, Occupational 

Exposure to Thorium Dust and Thoron, P.B. Klevin and J. Fresco; U.S. Atomic Energy Commission, 

New York Operations Office, Health and Safety Division; January 21, 1953; SRDB Ref ID: 9068 

Monazite, 1949, Using Monazite as a Source of Uranium; New York Operations Office; January 26, 

1949; SRDB Ref ID: 66924 

Monazite Process, date unknown, General Description of Curtis Bay Monazite Process, unknown 

author, but appears to be part of the Formerly Utilized Sites Remedial Action Project (FUSRAP); 

unknown date; SRDB Ref ID: 7251 

Monazite Process, 1951, Letter Describing Chemical Processing of Monazite Sand, from J. S. Murray 

(Lindsay Light & Chemical Company) to E. J. Lintner (Munitions Board, The Pentagon); January 1, 

1951; SRDB Ref ID: 81136 

NIOSH, 2009, NIOSH Report of Dose Reconstruction under the Energy Employees Occupational 

Illness Compensation Program (EEOICPA); [Case No. redacted]; July 1, 2009; OSA Ref ID: 112871, 

pdf pp. 13-31 

OCAS-IG-004, The Use of Data from Other Facilities in the Completion of Dose Reconstructions 

under the Energy Employees Occupational Illness Compensation Program Act, Rev. 0, Office of 

Compensation Analysis and Support Implementation Guideline, National Institute for Occupational 

Safety and Health, Cincinnati, Ohio, August 21, 2008, SRDB Ref ID: 49029
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OCAS-TIB-009, Estimation of Ingestion Intakes, Rev. 00, Office of Compensation Analysis and 

Support Technical Information Bulletin; National Institute for Occupational Safety and Health 

(NIOSH); Cincinnati, Ohio; April 13, 2004; SRDB Ref ID: 22397 

ORAUT-OTIB-0004, Estimating the Maximum Plausible Dose to Workers at Atomic Weapons 

Employer Facilities, Rev. 03 PC-2; Oak Ridge Associated Universities; December 6, 2006; SRDB 

Ref ID: 29949

ORAUT-OTIB-0070, Dose Reconstruction During Residual Radioactivity Periods at Atomic 

Weapons Employer Facilities, Rev. 00; Oak Ridge Associated Universities; March 10, 2008; SRDB 

Ref ID: 41603

Personal Communication, 2011a, Personal Communication with Petitioner Representative; Telephone 

Interview by ORAU Team; May 5, 2011; SRDB Ref ID: 96226

Personal Communication, 2011b, Personal Communication with former W.R. Grace and Company 

(Maryland) Supervisor; Telephone Interview by ORAU Team; May 11, 2011; SRDB Ref ID: 96224

Petition, 2010, SEC Petition Form B for SEC-00182, W.R. Grace and Company (Maryland); [Name 

redacted]; December 21, 2010; OSA Ref ID: 112871, pdf pp. 1-10

Rad Handbook, 1998, Handbook of Health Physics and Radiological Health, 3rd Edition, B. Shleien, 

L. A. Slaback, Jr., B. K. Birky, editors; 1998; SRDB Ref ID: 22737 (commonly available from public 

resources) 

RWDA Remedial Investigation Vol. 1, 2001, Revised Final: Remedial Investigation (RI) Report for 

the Radioactive Waste Disposal Area (RWDA) at the W.R. Grace Curtis Bay Facility, Baltimore, 

Maryland, Volume 1 of 2, U.S. Army Corps of Engineers, Baltimore District, July, 2001; SRDB Red 

ID: 97417 

RWDA Remedial Investigation Vol. 2, 2001, Revised Final: Remedial Investigation (RI) Report for 

the Radioactive Waste Disposal Area (RWDA) at the W.R. Grace Curtis Bay Facility, Baltimore, 

Maryland, Volume 2 of 2 (Appendices), U.S. Army Corps of Engineers, Baltimore District, July, 2001; 

SRDB Red ID: 97415 

Shaw, 1978, Account of Facts Pertaining to the Radioactive Waste Disposal Site on the Property of 

W.R. Grace at Curtis Bay, Maryland; with cover letter from F. V. Shaw (W.R. Grace) to D. H. Noren 

(Maryland State Dept. of Health and Mental Hygiene); October 20, 1978; SRDB Ref ID: 7176 

Survey, 1961, Survey of Radiological Air-Borne Contamination; May 10, 1961; SRDB Ref ID: 41327, 

pdf p. 378 

Trip Report, 1985, Trip Report on Visit to W.R. Grace, Curtis Bay, Maryland, M.G. Jones, et al, 

Bechtel National, Inc.; report on trip by BNI, ANL, and DOE personnel; November 11-12, 1985: 

SRDB Ref ID: 15303 
SEC-00182 07-14-11 W.R. Grace and Co. (Maryland)

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Attachment 1: Data Capture Synopsis 

Table A1-1: Data Capture Synopsis for W. R. Grace and Company (Maryland) 

Data Capture Information General Description of Documents Captured Dat

Primary Site/Company Name: W.R. Grace 

AWE 1955-1958; Residual Radiation 1959-1978 Other Site Names:

Davison Chemical Corp. Agri-Chemicals Div. Rare Earths, Inc. Physical size of the site: 

The Curtis Bay site encompasses approximately 260 acres. The waste disposal area occupies approximately 40 acres. Monazite sand processing was performed in Building 23, which has approximately 525,000 square feet under roof, based upon exterior dimensions of 300' by 350' and 5 floors. Monazite processing was performed in an area comprising approximately 1/4 of the total Building 23 floor area. Size of the workforce: 

No information regarding employment numbers during the operational period has been identified. In 1986, 90 employees worked in Building 23. Of these, 18 worked in the former monazite sand processing area. By 1987, 5 full time employees and 1 half time employee worked in the former monazite sand processing area. In 2009 total employment at the Curtis Bay site was 564; in 2010 it was 530. 

[Name redacted], [Title redacted], Public and Regulatory Affairs, confirmed that a company-wide search did not identify any relevant records from either the AWE operational period or the residual radiation period. NOTE: W. R. Grace is working the Curtis Bay clean up. 

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Table A1-1: Data Capture Synopsis for W. R. Grace and Company (Maryland) 

Data Capture Information General Description of Documents Captured Dat

State Contacted: Maryland Department of Environment Maryland state provided FUSRAP documents. Performed data 

capture at MD Department of Environment, Baltimore, MD. A 1999 incident response, 1982 inspection notes of low level radioactive waste, 1984 site inspection, an aerial view of the plant and surrounding area, Building 23 remedial investigation and feasibility studies, and radioactive waste disposal area remedial investigation. 

Nuclear Regulatory Commission (NRC) OPEN - 28 non publicly available documents are on order. DOE Germantown References to thorium work at W.R. Grace and descriptions of early 

thorium processing. 

DOE Hanford No relevant data identified. DOE Legacy Management - Grand Junction Office Oak Ridge National Laboratory survey plans, Rare Earths thorium 

documents and contracts, source material licenses, thorium shipments and receipts, FUSRAP documents, thorium process description, and building occupancy data. 

DOE Legacy Management - MoundView (Fernald Holdings, includes Fernald Legal Database) 

Response letter to a request for additional Th02 powder, inventory of thorium nitrate tetrahydrate, evaluation of TNT, and 1974 shipping documents. 

Internet AEC licenses, license application, and a license transfer application. Internet - Department of Energy (DOE) No relevant data identified. Internet - DOE Argonne National Laboratory No relevant data identified. Internet - DOE Comprehensive Epidemiologic Data Resource (CEDR) 

No relevant data identified. 

Internet - DOE Hanford Declassified Document Retrieval System (DDRS) 

No relevant data identified. 

Internet - DOE Legacy Management Considered Sites No relevant data identified. Internet - DOE Oak Ridge National Laboratory (ORNL) No relevant data identified. Internet - DOE OpenNet Linking Legacies Appendix B. Note: This document was added by 

site association review. 

Internet - DOE OSTI Energy Citations No relevant data identified. Internet - DOE OSTI Information Bridge Proceedings of the tenth DOE low-level radioactive waste 

conference. 

Internet - DOE Protecting Human Subjects No relevant data identified. Internet - Google Company history, site summary, site plans, and FUSRAP documents 

including assessments and studies. 

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Table A1-1: Data Capture Synopsis for W. R. Grace and Company (Maryland) 

Data Capture Information General Description of Documents Captured Dat

Internet - Health Physics Journal No relevant data identified. Internet - Journal of Occupational and Environmental Hygiene 

No relevant data identified. 

Internet - National Academies Press (NAP) No relevant data identified. Internet - National Nuclear Security Administration (NNSA) - Nevada Site Office 

No relevant data identified. 

Internet - NRC Agencywide Document Access and Management (ADAMS) 

AEC license amendment application, FOIA request and responses, and a 1958 inspection report. 

Internet - U.S. Army Corps of Engineers No relevant data identified. Internet - U.S. NRC No relevant data identified. Internet - Washington State University (U.S. Transuranium and Uranium Registries) 

No relevant data identified. 

Internet - Washington University Libraries - St. Louis No relevant data identified. National Archives and Records Administration (NARA) Atlanta 

A quotation for W.R. Grace to produce 1000 grams U-233 as U3O8 for Y-12. 

National Archives and Records Administration (NARA) Kansas City 

History information, survey data, description of site, survey and description of Building 23, and a description of uranium from phosphate contracts. 

ORAU Team A key to 1970s Landauer dosimetry reports and documented 

communication with a process knowledge expert. 

Unknown Radiation status of site, radiological survey results, a general 

description of Curtis Bay, former thorium sites investigation, a Rare Earths contract, and a reference to W.R. Grace processing of monazite sand. 

Westinghouse Site (United Nuclear), Hematite, MO Reference to W.R. Grace as a supplier of UO2 pellets including a 

brief process description. 

TOTAL 

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Table A1-2: Databases Searched for W. R. Grace and Company 

Database/Source Keywords 

NOTE: Database search terms employed for each of the databases listed below are available 

 in the Excel file “W R Grace Curtis Bay, MD, Rev 01 (83.13) 05-03-11” 

Department of Energy http://www.doe.gov/ COMPLETED 01/13/2008 

See Note above 

DOE Argonne National Laboratory http://www.anl.gov/ COMPLETED 01/10/2008 

See Note above 

DOE CEDR http://cedr.lbl.gov/ COMPLETED 03/01/2011 

See Note above 

DOE Hanford DDRS http://www2.hanford.gov/declass/ COMPLETED 04/14/2011 

See Note above 

DOE Legacy Management Considered Sites http://csd.lm.doe.gov/ COMPLETED 04/14/2011 

See Note above 

DOE Oak Ridge National Laboratory http://www.ornl.gov/ COMPLETED 01/13/2008 

See Note above 

DOE OpenNet http://www.osti.gov/opennet/advancedsearch.jsp COMPLETED 04/14/2011 

See Note above 

DOE OSTI Energy Citations http://www.osti.gov/energycitations/ COMPLETED 04/14/2011 

See Note above 

DOE OSTI Information Bridge http://www.osti.gov/bridge/advancedsearch.jsp COMPLETED 04/14/2011 

See Note above 

DOE Protecting Human Subjects Website http://humansubjects.energy.gov/ COMPLETED 01/20/2008 

See Note above 

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Table A1-2: Databases Searched for W. R. Grace and Company 

Database/Source Keywords 

Google http://www.google.com COMPLETED 04/14/2011 

See Note above 

HP Journal http://journals.lww.com/health-physics/pages/default.aspx COMPLETED 03/01/2011 

See Note above 

Journal of Occupational and Environmental Health http://www.ijoeh.com/index.php/ijoeh COMPLETED 03/01/2011 

See Note above 

National Academies Press http://www.nap.edu/ COMPLETED 04/14/2011 

See Note above 

NNSA - Nevada Site Office www.nv.doe.gov/main/search.htm COMPLETED 04/14/2011 

See Note above 

NRC ADAMS Reading Room http://www.nrc.gov/reading-rm/adams/web-based.html COMPLETED 04/14/2011 

See Note above 

USACE http://www.nan.usace.army.mil/ COMPLETED 04/14/2011 

See Note above 

U.S. NRC http://www.nrc.gov/site-help/search.html COMPLETED 01/15/2008 

See Note above 

U.S. Transuranium & Uranium Registries http://www.ustur.wsu.edu/ COMPLETED 04/14/2011 

See Note above 

Washington University Libraries - St. Louis http://library.wustl.edu/units/westcampus/govdocs/nukes/index.html COMPLETED 01/15/2008 

See Note above 

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Table A1-3: OSTI Documents Ordered for W. R. Grace and Company 

Document Number Document Title R

ORNL/TM-10439 REF ID: 7188 

Results of the Indoor Radiological Survey at the W.R. Grace Co., Curtis Bay Site, Baltimore, Maryland dated 7/1/1989. 

10/1

PB-90-163544/XAB Superfund Record of Decision (EPA Region 1): W.R. Grace, Acton, 

Massachusetts (First Remedial Action), September 1989 dated 9/29/1989. 

10/1

PB-90-260118/XAB Health Assessment for W.R. Grace and Co., Inc./Wayne Interim 

Storage Site, Wayne, Passaic County, New Jersey, Region 2. CERCLIS No. NJD891837980, Final Report dated 7/30/1990. 

10/1