W.R. Grace and Company

Special Exposure Cohort 

Evaluation Report

James W. Neton, Ph.D., CHP

Associate Director for Science

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support

August 2011

Richland, WA
Background

 W.R. Grace is located in Curtis Bay, MD

 Originally 260 acres, now 109 acres

 Original site owned by Davison Chemical Company

 W.R. Grace bought Davison Chemical in 1954

 Rare Earths Inc., entered AEC contract in 1955, license 

transferred to W.R. Grace in ~ 1957

 W.R. Grace to extract thorium from monazite sand for 

AEC at two facilities (Wayne, NJ and Curtis Bay, MD)
Background—cont.

Building 23

Former 

monazite 

processing 

area
Site Operations

 Process AEC-owned monazite ore to extract 

thorium and rare earths

 Monazite contains ~ 6% thorium oxide

 95% of thorium in ore to be extracted

• 5% remained in residual material buried on-site

 Total of 997 tons of monazite processed between 

May 1956 and Spring 1957

 Problems with process led to contract termination
Site Operations—cont.

 All thorium work done in part of Building 23

• Monazite ground in ball mill

• Reacted with concentrated sulfuric acid

• Crystallizer tanks

• Rake classifier (crude separation)

• Filtering of Th-bearing solution and separation from 

unreacted material

• Precipitation and reaction to end product (thorium 

hydrate)

• Finished product shipped to Curtis Bay Government 

Storage Depot
Petition Overview

 December 21, 2010: NIOSH received an 

83.13 petition 

 February 17, 2011: Petition qualified for 

evaluation

 July 14, 2011: Evaluation Report approved
Proposed and Evaluated SEC Class

 Petitioner proposed 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.

 NIOSH evaluated 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.
Petition Bases and Concerns

 Unmonitored workers

• Petitioner presented an affidavit indicating 

that 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 is missing
Sources of Available Information

 ORAU Technical Information Bulletins

 Case files in NIOSH database

 NIOSH Site Research Database

• 132 documents pertaining to W.R. Grace - MD

 Documentation and/or affidavits provided by 

petitioner

 Interviews – one former worker, one petitioner 

representative

 Various electronic databases (DOE, NRC)
Previous Dose Reconstructions

NIOSH OCAS Claims Tracking System 

Information available as of August 2, 2011

 W.R. Grace MD claims submitted to NIOSH 1

 Claims that meet the class definition 1

 Dose reconstructions completed for claims 

that meet the class definition 1

 Claims containing internal dosimetry 0

 Claims containing external dosimetry 0
Potential Internal Radiation Exposure

 Monazite processing resulted in worker 

exposures from thorium, uranium and their 

decay products

• Inhalation and ingestion of dust from 

operations, especially dry-handling of 

materials

• Inhalation and ingestion of re-suspended 

particles in work areas

• Ingestion of particles from eating and drinking 

in work areas

• Inhalation of gaseous decay products (radon 

and thoron)
Potential External Radiation Exposures

 Photon/beta exposure from thorium and 

uranium and decay products present in monazite 

sands during milling and extraction operations
Availability of Internal 

Dosimetry Data

 Operational period:

• No internal dosimetry data, air sample data or 

sufficient source term or process data have been 

located

 Residual Period:

• Air sample data from Rare Earths/W.R. Grace, Wayne, 

NJ from 1959 and 1961 (shared contract with W.R. 

Grace, MD)

• 1986 and 2000/2001 site characterization data from 

FUSRAP
Availability of External Dosimetry Data

 Operational period:

• No external personnel or area monitoring data 

(including medical X-rays) have been located 

 Residual period:

• Dose rate data from 1986 site characterization from 

FUSRAP
Approach to Residual Period Dose 

Reconstruction

 Internal: 

• Use of air concentration values at beginning and later 

during the residual period to calculate intake rates

• Assume exponential relationship to calculate intake 

rates for intervening time periods

 External: 

• Radiation dose rate data measured in 1986

• Application of depletion factor determined above
Evaluation Process

 Two-prong test established by EEOICPA and 

incorporated into 42 C.F.R. § 83.13 (c)(1) and 42 

C.F.R. § 83.13 (c)(3):

1. Is it feasible to estimate the level of radiation doses 

of individual members of the class with sufficient 

accuracy?

2. Is there a reasonable likelihood that such radiation 

dose may have endangered the health of members of 

the class?
Feasibility of Dose Reconstruction

The process and source term information provide 

insufficient information to estimate doses 

associated with monazite processing with 

sufficient accuracy for workers at W.R. Grace and 

Company.
Summary

Feasibility Findings for W. R. Grace and Company Petition

May 1, 1956 – January 31, 1958

Source of Exposure Reconstruction 

Feasible

Reconstruction 

NOT Feasible

Internal

- all radionuclides X

External

- Photon X

- Beta X

- Neutron N/A

- Occupational

Medical X-ray

N/A
Summary—cont. 

Feasibility Findings for W. R. Grace and Company

February 1958 – October 2009

Source of Exposure Reconstruction 

Feasible

Reconstruction 

NOT Feasible

Internal

- all radionuclides X

External

- Photon X

- Beta X

- Neutron N/A

- Occupational

Medical X-ray

N/A
Health Endangerment

 The evidence reviewed in this evaluation 

indicates that some workers in the class may 

have accumulated chronic radiation exposures 

through intakes of radionuclides and direct 

exposure to radioactive materials.

 Consequently, NIOSH is specifying that health 

may have been endangered for those workers 

covered by this evaluation who were employed 

for a number of work days aggregating at least 

250 work days within the parameters 

established for this class or in combination with 

work days within the parameters established for 

one or more other classes of employees in the 

SEC .
Proposed Class

All Atomic Weapons Employees who worked in 

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.
Recommendation

 For the period May 1, 1956 – January 31, 1958, 

NIOSH finds that radiation dose estimates cannot 

be reconstructed for compensation purposes

Class Feasibility Health Endangerment

May 1, 1956 – January 

31, 1958 No Yes