REPORT TO THE ADVISORY BOARD ON RADIATION AND 

WORKER HEALTH 

National Institute of Occupational Safety and Health 

Audit of Case #PIID* from the Bethlehem Steel Facility 

Contract No. 200-2004-03805 Task Order No. 4 

SCA-TR-TASK4-CNPIID* 

Prepared by 

John Mauro, PhD CHP S. Cohen & Associates 6858 Old Dominion Road, Suite 301 

McLean, Virginia 22101 

February 2005 

NOTICE: This information is protected by Privacy Act 5 USC §552a; disclosure to any third party 

without the written consent of the individual to whom the information pertains is strictly prohibited. 
S. Cohen & Associates: 

Technical Support for the Advisory Board on Radiation 

& Worker Health Review of NIOSH Dose 

Reconstruction Program 

AUDIT OF CASE #PIID* FROM THE 

BETHLEHEM STEEL FACILITY 

Task Manager: ___________________ Date: 02/04/05 

Hans Behling, PhD, MPH 

Project Manager: _________________ Date: 02/04/05 

John Mauro, PhD, CHP 

Document No. 

SCA-TR-TASK4-CNPIID* 

Effective Date: February 4, 2005 

Revision No. 1 

Page 2 of 17 

 Supersedes: 

Draft Rev. 0 
 

 

 

TABLE OF CONTENTS 

Summary ........................................................................................................ 4 

1.0 Introduction ........................................................................................ 6 

2.0 Summary of Doses .............................................................. 8 

3.0 Independent Reproduction and Review of Selected NIOSH Derived 

Doses ................... 10 

3.1 Internal Dose from Inhalation ........................................... 10 

3.2 External Exposures ........................................................... 13 

3.2.1 External Exposures to Uranium Sources .......................... 13
 

3.2.2 External Annual Doses to Red Bone Marrow Due to Submersion in
 

Air Containing Uranium Dust ......................................................... 14 

3.2.3 External Annual Doses to Red Bone Marrow Due to Photons from
 

Contaminated Surfaces .................................................................... 14 

3.2.4 External doses to Red Bone Marrow Due to Routine, Work-Related 

Medical X-Ray Examinations .......................................................... 14 

3.3 Conclusions ........................................................................... 15 

References ......................................................................................... 17 
SUMMARY 

This report presents the results of an independent audit of a dose reconstruction 

performed by the National Institute of Occupational Safety and Health (NIOSH) for an 

energy employee (Case #PIID*) that worked at the Bethlehem Steel Corporation from 

PIID*, through PIID*. This time period includes the time period (1949 to 1952) when the 

Bethlehem Steel facility in Lackawanna, New York, was under contract with the Atomic 

Energy Commission (AEC) to develop rolling mill pass schedules for the rolling of 5­

inch natural uranium billets into 1.5-inch rods to be used in nuclear reactors. As a result 

of the worker’s employment at the facility during and following the uranium rolling 

operations, the worker likely experienced internal exposures due to the inhalation of 

airborne particles of uranium oxide and external exposure from working in the vicinity of 

the uranium billets, rods, and residual uranium. In addition, the worker is believed to 

have had routine x-rays as part of Bethlehem Steel’s medical surveillance program. The 

worker was not provided with film badge or thermoluminescent dosimeters (TLDs) to 

measure external exposures, nor were bioassays performed to estimate internal exposures. 

As a result, exposures experienced by the worker were estimated using the exposure 

matrix provided in the site profile or Technical Background Document (TBD) prepared 

by NIOSH for the Bethlehem Steel plant (ORAUT-TKBS-0001, March 31, 2003). 

In PIID*, following his employment, the energy employee was diagnosed with multiple 

myeloma. Table 1 summarizes the results of NIOSH’s reconstruction of the doses to the 

energy employee’s red bone marrow for the purpose of deriving the probability of 

causation (POC) using IREP. Table 1 also presents the results of the audit. The results of 

the audit are expressed in terms of whether we found the exposures to have been derived 

in a scientifically valid and claimant-favorable manner. 

The implications of this audit are that there are many aspects of the methods used by 

NIOSH to reconstruct the doses to the bone marrow of this worker that do not appear to 

be entirely scientifically valid or claimant favorable. However, there are other aspects 

of the dose reconstruction methods that are conservative. On balance, it would appear 

that there are many issues associated with the dose reconstruction methods used by 

NIOSH that need to be more thoroughly explored and which may reveal that the 

reconstructed doses to this worker were not as scientifically robust or claimant favorable 

as represented in the dose reconstruction report for this worker and the supporting TBD. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1. Summary of Internal and External Exposure to the Red Bone Marrow as 

Estimated by NIOSH, Along with the Audit Results 

(The values reported here are the modes of a triangular distribution) 

Exposure Scenario 

NIOSH Derived 

Annual Doses (rem) 

Scientifically 

Valid? 

Claimant 

Favorable? 

Internal exposure from inhalation (alpha) during 

operations 

About 3E-3 during 

AEC operations 

We have 

concerns 

We have 

concerns 

Internal exposures from ingestion (alpha) during 

operations 

Negligible We have 

concerns 

We have 

concerns 

Internal exposure from inhalation (alpha) of residual 

resuspended particles following the conclusion of 

operations 

Negligible We have 

concerns 

We have 

concerns 

External exposures during operations (PIID*) 

Ground surface contamination (chronic) Negligible Yes, 

considering 

the method 

used to derive 

exposures to 

from uranium 

sources 

Yes, 

considering 

the method 

used to derive 

exposures to 

from uranium 

sources 

Natural Uranium Source (chronic) 0.1 Yes Yes 

 Submersion in airborne plume (chronic) Negligible Yes NA* 

Diagnostic x-rays (acute) 0.027 Yes Not 

necessarily 

Chronic external exposure to residual contamination 

following the conclusion of AEC operations in 1952 

Assumed to be 

negligible 

Cannot be 

determined 

Not likely 

* NA refers to not applicable. 
1.0 INTRODUCTION 

This report presents the results of an independent audit of a dose reconstruction 

performed by the National Institute of Occupational Safety and Health (NIOSH) for an 

energy employee that worked at the Bethlehem Steel facility in Lackawanna, New York. 

This audit is one of several dose reconstruction audits being performed by S. Cohen & 

Associates (SC&A, Inc.) on behalf of the Advisory Board on Radiation and Worker 

Health. 

This audit report makes extensive use of the findings provided in a separate report 

prepared by SC&A entitled Review of NIOSH Site profile for Bethlehem Steel Plant, 

Lackawanna, NY (SCA-TR-TASK1-001, October 2004). The review of the site profile 

prepared by SC&A is currently being reviewed by NIOSH. We expect that NIOSH will 

provide comments on the SC&A site profile review that, upon consideration by SC&A, 

may affect the findings of this audit report. 

This report has been prepared taking into consideration this extensive factual 

accuracy and technical review process. 

Part one of this audit report presents a summary of our understanding of the doses 

derived by NIOSH, along with a brief description of the basic approach and assumptions 

employed by NIOSH to derive the doses. This material is extracted directly from the final 

dose reconstruction report published by NIOSH for this case, along with supporting 

documentation, including the Technical Basis Document (TBD) for the Bethlehem Steel 

facility (ORAUT-TKBS-0001, March 31, 2003). This section of the report summarizes 

our understanding of the methods used by NIOSH to reconstruct the doses to workers, 

and also serves as a baseline for the discussion and audit provided in Section 3 of this 

report. 

Part two of the audit process (provided in Section 3 of this report) consists of an attempt 

to independently reproduce doses derived by NIOSH and a discussion of the validity of 

the methods employed. The doses selected for review are based on the judgment of the 

reviewers as to the importance of the particular doses to the totality of the doses 

experienced by the energy employee. The reason for this step in the audit process is to 

provide the author, NIOSH, and the Advisory Board with a level of assurance that the 

auditors understand how NIOSH went about deriving the doses provided in their dose 

reconstruction report. In the process of attempting to reproduce the NIOSH derived 

doses, we also provide a critical review of the fundamental data, information, models, 

and assumptions used by NIOSH to perform the dose reconstruction. This review draws 

heavily from a draft review of the TBD prepared by SC&A and submitted to the 

Advisory Board in October 2004.1

 This part of the audit explores the degree to which the 

data are adequate to support the dose reconstruction, and whether the models and 
 

assumptions adopted by NIOSH to perform the dose reconstruction are scientifically 

sound and claimant favorable. Areas where the methods are found to meet these criteria, 

or are deemed to be inadequate with regard to these criteria, are identified and discussed. 

The report is not exhaustive in the review of these matters, but is limited to those areas 

of inquiry that are judged by the auditors to be significant with respect to the dose 

reconstruction and the derivation of the probability of causation (POC). 

1

 SC&A’s review of the Bethlehem Steel TBD was delivered to the Advisory Board in draft form 

in October 2004. The report is entitled Review of the NIOSH Site Profile for Bethlehem Steel Plant, 

Lackawanna, NY, Contract No. 200-2004-03805, Task Order No. 1, SCA-TR-TASK1-001, October 2004. 

The Board has not yet officially accepted the report, and NIOSH has not yet had an opportunity to respond 

to the SC&A’s findings. 

Methods employed by NIOSH that are found to be either scientifically inappropriate or 

not necessarily clamant favorable are identified, but no attempt is made to correct these 

deficiencies and redo the dose calculations. It is assumed that NIOSH and the Advisory 

Board will have an opportunity to consider the results of this audit and determine whether 

a revision of the dose reconstruction is needed, and if so, how to go about making the 

necessary revisions. 
2.0 SUMMARY OF DOSES 

The energy employee worked at the Bethlehem Steel Corporation from PIID*,, through 

PIID*. This time period includes the time period (1949 to 1952) when the Bethlehem 

Steel facility in Lackawanna, New York was under contract with the Atomic Energy 

Commission (AEC) to develop rolling mill pass schedules for the rolling of 5-inch 

natural uranium billets into 1.5-inch rods to be used in nuclear reactors. In PIID*, 

following employment, the energy employee was diagnosed with multiple myeloma. 

Table 2 presents the results of NIOSH’s reconstruction of the doses to the energy 

employee’s red bone marrow for the purpose of deriving the probability of causation 

(POC) using IREP. 

The notations used in Table 2 to present the doses include the year in which the dose was 

received by the organ of interest, the statistical distribution that was used, and the key 

parameters for the distribution. For example, for exposure period number 1 in Table 2 

(PIID*), internal exposure of the bone marrow to alpha emitters is assumed to have a 

triangular distribution with a minimum of 0, a mode of 1.35E-3, and a maximum of 

9.57E-1 rem due to the inhalation of uranium dust. A discussion of various types of 

statistical distributions and other parameters used as input to NIOSH-IREP is provided in 

NIOSH (2002). The internal dose to the organ of interest was determined by NIOSH to 

have a range of 0 to 24.2 rem, with a mode of 0.034 rem. The external dose to the organ 

of interest was determined by NIOSH to have a range of 0.07 to 1.23 rem, with a mode 

of 0.56 rem. Based on these reconstructed doses, the POC was determined to be less than 

50%, and the claim was denied. 

The final dose reconstruction report and the technical basis document (TBD) provide 

detailed descriptions of the methods and assumptions used by NIOSH to derive the doses 

presented in Table 2. As may be noted, Table 2 presents doses in terms of annual doses 

due to internal alpha exposure resulting from the inhalation of uranium, and external 

exposure from low energy and higher energy gamma emissions associated with working 

at the facility. These include external exposures due to working in the vicinity of the 

uranium and diagnostic x-rays performed as part of job-related routine medical 

surveillance. None of the dose estimates are based on the use of dosimeters worn by the 

energy employee, such as film badges or TLDs, which, if used, would have provided a 

generally reliable method for determining external doses to the organ of concern. In 

addition, none of the dose estimates are based on bioassay data, such as urine or fecal 

analysis, or whole-body counting, which would have provided a generally reliable basis 

for estimating internal doses to most organs from the inhalation and/or ingestion of 

uranium. Instead, the doses were derived indirectly, using the generic methodologies 

described in the TBD. 
Table 2. Doses to the Red Bone Marrow of the Employee as Derived by NIOSH for 

Use as 

Input to IREP for the Purpose of Deriving Probability of Causation 

The following table was deleted – please see hard copy #3. 
3.0 INDEPENDENT REPRODUCTION AND REVIEW OF 

SELECTED 

NIOSH DERIVED DOSES 

This section presents a series of hand and computer calculations that attempt to reproduce 

selected doses derived by NIOSH. In so doing, we will have confirmed that we 

understand how NIOSH performed the dose reconstruction and that the calculations are 

correct, given the models and assumptions employed by NIOSH. In the process of 

attempting to reproduce the doses, we also discuss and critically review the data, models, 

and assumptions employed by NIOSH to reconstruct the doses. 

3.1 INTERNAL DOSE FROM INHALATION 

As indicated in Table 2, the annual alpha doses to the red bone marrow were 

determined by NIOSH to build up to a peak mode of 3.76E-3 rem/y in PIID*, with a 

minimum of 0 and a maximum of 2.67. After PIID*, when AEC rolling operations 

ceased, the annual alpha doses to the red bone marrow gradually decline due to gradual 

clearance of the uranium from the bone marrow. In this section, the peak annual alpha 

dose delivered to the bone marrow in PIID* is checked by reviewing the source 

documents, and by performing hand and IMBA calculations. 

The starting point for this analysis is a description of the rolling operations and how 

workers were exposed to airborne particles of uranium. Uranium billets were shipped to 

Bethlehem Steel by freight cars, in which the billets were stored on site until the rolling 

operations were initiated. Since the facility was fully involved in rolling steel billets, 

uranium-rolling operations at Bethlehem Steel took place only on weekends. Table 1 of 

the TBD presents NIOSH’s estimate of the dates when experimental and production 

rollings took place, along with an estimate of the number of billets that were rolled. In 

general, uranium rollings occurred on weekends, and, during the week, the workers 

returned to their normal activities, which involved rolling steel billets. 

During the rolling operations, airborne uranium dust was generated primarily as a result 

of the oxidation and flaking of uranium particles as the billets were processed through the 

rollers. NIOSH performed a review of uranium dust loading measurements made at the 

Bethlehem Steel facility and another similar facility, Simonds Saw. Based on a review of 

these air-sampling data, NIOSH concluded that the amount of air-sampling data was very 

limited, making it difficult to construct a reliable characterization of the airborne uranium 

dust concentrations at the facility as a function of time and work location. Because of 

these uncertainties, NIOSH elected to construct two alternative distributions of the 

airborne uranium dust concentrations at the Bethlehem Steel facility. One distribution 

was considered a lower-bound estimate of the range of dust loadings throughout the 

facility, and the other was considered an upper-bound estimate of the uranium dust 

loadings throughout the facility. The lower-bound distribution was used as a basis for 

quickly determining whether a claimant should be compensated; i.e., if the reconstructed 

doses using the lower-bound distribution were determined to be compensable, the 

analysis was considered complete. However, if the use of the lower-bound distribution 
 

 

 

 

 

 

 

yielded doses that were not compensable, then the upper-bound distribution was used as 

the basis for rejecting a claim. 

The dose reconstruction undergoing review in this report is for a worker whose claim was 

denied. As a result, the focus of attention of this review is the upper-end radionuclide 

concentration distribution employed by NIOSH, as provided in Table 2b of the TBD, and 

which is reproduced here as Table 3. 

Table 3. Internal Exposure Matrix-Upper Bound 

(Reproduced from Table 2b of the TBD) 

Work period Air Concentration (dpm/m3) Breathing Rate (m3/hr)* Hours Annual Intake (pCi) 

Min Mode Max Light/heavy Min Mode Max 

PIID* 0 140 70,000 1.2/1.7 120 0 9.16E3 6.49E6 

PIID* 0 140 70,000 1.2/1.7 120 0 9.16E3 6.49E6 

PIID* 0 140 70,000 1.2/1.7 130 0 9.93E3 7.03E6 

PIID* 0 140 70,000 1.2/1.7 110 0 8.40E3 5.95E6 

* The breathing rate of 1.2 m3/hr was used to calculate the minimum and mode intake. The 

breathing rate of 1.7 m3

/hr was used to calculate the maximum intake. 

As an example, the uranium inhalation of 9.16E3 pCi for 1949 was derived as follows: 

(140 dis/min per m3)/(60sec/min) = 2.33 dis/sec per m3 = 63 pCi/ m3 

(63 pCi/ m3)(1.2 m3/hr)(120 hr/yr) = 9072 pCi/yr 

This value does not exactly match the value in Table 3, but the difference is small and 

it is not considered necessary to further evaluate the reasons for the difference. 

In the TBD, NIOSH explains that the assumptions used to derive the uranium inhalation 

rates are conservative as applied to workers at the facility for several reasons. First, a 

mode of 140 dpm/ m3 is higher than the actual average airborne dust loading observed at 

Bethlehem Steel, and the maximum value was actually obtained from Simonds Saw data, 

not Bethlehem Steel data, where the maximum observed airborne dust loading was much 

lower. Second, the number of hours of exposure per year is characterized as being an 

upper bound. For example, Table 1 of the TBD indicates that in PIID* and PIID* there 

were only 6 and 8 days of rollings, respectively. Assuming 10 work hours per day, this 

would correspond to 60 hours and 80 hours of exposure per year, as opposed to the work 

hours employed in the TBD (i.e., the TBD assumed exposure durations that were 

approximately twice these values). For the purpose of deriving doses to internal organs 

other than the lungs, it was conservatively assumed that the uranium was Absorption 

Type M, when it is generally believed that the chemical form of the uranium was more 

likely Absorption Type S. Finally, the particle size of the airborne dust was assumed to 

have an AMAD of 5 micron. This is the default value recommended for use by ICRP, and 

is considered a generally conservative assumption. 
Table 2, which was reproduced directly from the dose reconstruction report, presents the 

annual alpha doses to the bone marrow for each year as a result of these inhalation rates 

and modeling assumptions. Our independent analysis using IMBA and the intake rates 

in Table 1 agrees with the doses provided in Table 2. 

SC&A’s independent review of the TBD identified a number of concerns regarding these 

assumptions, which indicate that the exposure matrix may not be entirely scientifically 

sound and claimant favorable. The principal concerns cited by SC&A in its site profile 

review of the TBD are as follows: 

1. The actual air-sampling data does not fit a triangular distribution. A much better 

fit is obtained using a lognormal distribution. 

2. The TBD claims that 70,000 dpm/m3 is a reasonable upper bound for the dust 

loading at the facility. However, inspection of the original data reveals a number of 

measurements made at Simonds Saw that exceed 70,000 dpm/m3 

. 

3. The radionuclide concentration distribution is applied to all workers at the facility. 

However, some workers may have had job responsibilities or worked at locations where 

they experienced prolonged exposures at the upper end of the distribution. 

4. The exposure matrix assumes that, immediately following each rolling campaign, 

the residue of uranium dust that settled on surfaces during uranium rollings was cleaned 

up. As a result, the TBD assumes that no inhalation exposures occurred during the work 

week while the workers were engaged in rolling steel. The SC&A review of the TBD 

provides evidence that there may have been substantial amounts of residual uranium dust 

on surfaces during the time periods between uranium rollings. 

5. The TBD also assumes that, after uranium rolling operations were believed to 

cease in 1952, residual uranium dust was cleaned up and there was no potential for 

inhalation of resuspended dust subsequent to 1952. 

6. The TBD assumed that there were no additional uranium rollings after 1952, 

when there is some indication that there may have been additional uranium rollings after 

1952. 

7. The TBD did not take into consideration that the rolling operations were 

physically demanding, requiring higher breathing rates and oro-nasal breathing, which 

would have resulted in greater quantities of inhaled uranium. 

8. Interviews with workers revealed that there were off-normal conditions, 

accidents, and maintenance operations, where the potential existed for substantially 

higher inhalation rates for uranium during short periods of time. 

9. The TBD did not take into consideration the possibility that the dust loading in the 

breathing zone of the workers may have been higher than that observed using general 

area air samplers. ICRP Reports Nos. 35 and 75 provide evidence that the dust loading in 

the breathing zone is often considerably higher than that determined by general air 

samplers. 

The SC&A review of the TBD provides a detailed discussion of these issues. The 

implications are that there are many aspects of the exposure matrix used by NIOSH to 

reconstruct the internal doses to the bone marrow of this worker that do not appear to be 
 

entirely scientifically valid or claimant favorable. However, there are other aspects of the 

exposure matrix provided in the TBD that are conservative. On balance, it would appear 

that there are many issues associated with the exposure matrix used to derive internal 

exposures at Bethlehem Steel that need to be more thoroughly explored, and which may 

reveal that the reconstructed doses to this worker were not as scientifically robust or 

claimant favorable as represented in the TBD. 

3.2 EXTERNAL EXPOSURES 

NIOSH estimated the external dose using the TBD. Three sources of external exposures 

were explicitly considered, including (1) external exposure to the metallic uranium 

feedstock and rods prior to, during, and following rolling; (2) external exposure to 

airborne uranium dust; and 

(3) annual x-ray exposures employed as part of the medical surveillance program. 

Table 4 summarizes these doses as reported in the NIOSH dose reconstruction report. 

The TBD also estimated the skin and shallow dose, but these exposures do not apply 

to exposure to red bone marrow and are not addressed here. 

Table 4. Summary of External Photon Exposures to Red Bone Marrow as Reported 

by NIOSH 

Source of Exposure Approximate Annual Organ Doses to Photons (rem) 

Minimum Mode Maximum 

Uranium sources 0.02 0.1 0.2 

X-rays 0 0.027 0.105 

Submersion Negligible (<<1 mrem) 

This section attempts to reproduce these values and then discusses the degree to 

which these estimated doses are scientifically robust and claimant favorable. 

3.2.1 External Exposures to Uranium Sources 

The external exposure to red bone marrow from external uranium sources were derived 

by NIOSH by assuming the worker was exposed to a semi-infinite plane source of natural 

uranium. The TBD sites several references as the basis for deriving the deep photon dose 

from this exposure setting. Citing reports by Coleman et al. 1983 and U.S. Army 1989, 

the TBD estimated a deep dose rate of 2 mrad/hr at a depth of 1,000 mg/cm2 (i.e. 1 cm 

depth dose). NIOSH further assumed that the 2 mrad/hr deep dose rate from the uranium 

source is evenly divided between photons with energies E=30-250 keV and E=>250 keV, 

and that the exposure orientation was anterior-posterior. 

The TBD also cites a report by U.S. AEC 1948b as the basis for assumptions regarding 

exposure time and distance. For the mode, NIOSH assumed the worker was located 1 

meter away from the extended source for 1 hour per 10-hour work shift. For the 

maximum dose, NIOSH assumed the worker was located 0.3 meters from the source for 6 
hours per shift and 1 meter for 4 hours per shift. Based on Table 2b of the TBD, the 

worker is assumed to work about twelve 10-hour shifts per year and that external 

exposures only occurred during these time periods. 

Based on the above assumptions, the red bone marrow doses can be reproduced as 

follows: 

(2 mrad/hr)(120 hrs/yr)(0.001 rem/mrem)(0.479)/2 + (2 mrad/hr)(120 hrs/yr)(0.001) 

rem/mrem)(0.746)/2 = 0.057 + 0.0895 = 0.147 rem/yr 

This value is in agreement with the value reported by NIOSH for the mode. 

As a means of checking on the 2 mrad/hr 1 cm absorbed dose rate, we ran MicroShield 

to determine the dose rate at a point 1 meter away from an effectively infinite slab of 

natural uranium metal with its short-lived progeny in equilibrium. The result of the 

analysis is a dose rate of 2 mrad/hr, in total agreement with the value reported in the 

TBD. 

With respect to the exposure distances and durations, these certainly appear to be 

claimant favorable, unless the uranium was stored in the immediate vicinity of the 

workers while they were rolling steel during the intervening work week. However, 

there is no indication in the literature that this was the case. Accordingly, it certainly 

appears that the methods used by NIOSH to estimate the red bone marrow dose to 

workers from external sources of uranium is scientifically valid and claimant 

favorable. 

3.2.2 External Annual Doses to Red Bone Marrow Due to Submersion in Air 

Containing Uranium Dust 

NIOSH concluded that this dose was negligible (below 1 mrem/year), and our analysis 

revealed the same result. 

3.2.3 External Annual Doses to Red Bone Marrow Due to Photons from 

Contaminated Surfaces 

The approach used by NIOSH to derive the external doses to red bone marrow from 

uranium sources assumed that the worker was exposed to an infinite slab of uranium. 

This approach not only accounts for exposure to sources of uranium, such as billets and 

rods, it also more than accounts for exposure to surfaces contaminated with dust during 

rolling operations. However, NIOSH assumes that the dust is thoroughly cleaned up 

upon completion of each uranium rolling campaign. If the cleanup was not thorough, 

there would be some continual external exposure to low levels of uranium dust on 

surfaces during the work week. However, the marginal additional exposures that may be 

associated with residual uranium following cleanup were probably small and more than 

accounted for by the conservatism inherent in the methods used to derive external 

exposures to sources of uranium. 
3.2.4 External doses to Red Bone Marrow Due to Routine, Work-Related 

Medical X-Ray Examinations 

The 0.027 rem annual dose to the red bone marrow from medical examinations of 

workers at Bethlehem Steel, as estimated in the TBD, is consistent with the value of 

0.018 rem for pre-1970 PA x-rays provided in Table 4.0-1 of ORAUT-OTIB-0006 (we 

are not quite sure of the reasons for the small difference between the TBD and the values 

in OTIB-0006, but the differences are too small to be of significance). However, in 

accordance with the guidance provided in OTIB006, lacking information to the contrary, 

it would have been more claimant favorable to assume that at least some examinations 

included photofluorography, as such examinations were a matter of standard practice 

prior to 1960. Table 4.0-1 recommends a default pre-1970 photofluorographic entrance 

kerma dose of 3,000 mrem, with a corresponding red bone marrow dose of 0.276 rem per 

photofluorograph. If the worker had, in fact, received some photofluoroscopic 

examinations, the annual doses to the organ of interest would have been substantially 

greater than the values employed in the dose reconstruction. 

3.3 CONCLUSIONS 

We have found that many aspects of the dose reconstruction are scientifically robust 

and claimant favorable, but other aspects are not. The scientifically robust and 

claimant favorable aspects of the dose reconstruction are as follows: 

1. The use of an effectively infinite slab of uranium as the source of external 

exposure to uranium, and that the workers were continually exposed to this source at a 

distance of 1 meter for the entire time that the rolling operations took place, is an 

extremely claimant-favorable assumption and may offset many of the less claimantfavorable assumptions described below. 

2. The assumption that the inhaled uranium is Absorption Type M and that the 

particle size distribution has an AMAD of 5 microns is claimant favorable for the 

purposes of deriving inhalation exposures to red bone marrow. 

Some of the less scientifically robust and claimant-favorable assumptions are as follows: 

1. The use of a triangular distribution for the airborne uranium concentrations at the 

facility during rolling as the basis for all worker inhalation exposures does not appear to 

be scientifically robust or necessarily favorable to all claimants. The reason is that a 

lognormal distribution appears to provide a much better fit to the data, and, more 

importantly, it does not seem to be appropriate to assume that all workers experienced the 

same airborne dust exposure distribution. 

2. It is likely that the dust loading in the breathing zone of workers was higher than 

in the general environment of the facility, and this possibility was not taken into 

consideration in the reconstruction of the inhalation doses. 
3. Given the strenuous nature of the work, consideration should have been given to 

the possibility that the workers had relatively high breathing rates, which included oronasal breathing, which would have increased the estimate of internal doses. 

4. There was likely some residual uranium dust on surfaces between rollings and 

following the termination of rollings that was not taken into consideration in the 

reconstruction of the inhalation doses. 

5. Routine diagnostic medical examinations may have included photofluoroscopic 

examinations, which would have greatly increased the estimated bone marrow dose 

associated with annual diagnostic x-ray examinations. 

6. Inadvertent ingestion of uranium-contaminated soot appears to have been 

significantly underestimated, given information available in the literature addressing this 

issue. 
REFERENCES 

EPA 1997, “Exposure Factors Handbook,” EPA/600/P-95/002Fa, August 1997. ICRP 1995, International Commission on Radiological Protection, “Age-dependent Doses to Members of the Public Radionuclides: Part 4 Inhalation Dose Coefficients,” ICRP Publication 71, 1995. Kathren, R.L., Shockley, V.E., Thomas, E.M., Taulbee, T.D., Technical Information Bulletin: Dose Reconstruction Occupationally Related Diagnostic X-ray Procedures, ORAUT-OTIB-0006, 2003. NIOSH 2002, “NIOSH-Interactive Radioepidemiological Program (NIOSH-IREP) Technical Documentation,” Fina2002 NIOSH 2002a, “External Dose Reconstruction Implementation Guideline,” OCAS-IG-0001, Rev 1, August 2002. ORAUT-TKBS-0001, Technical Basis Document: Basis for Development of an Exposure Matrix for Bethlehem Ste31, 2003. ORAUT-OTIB-0006, Technical Information Bulletin: Dose Reconstruction from Occupationally Related DiagnostiDecember 29, 2003. ORAT-OTIB-0004, Technical Information Bulletin: Technical Basis for Estimating the Maximum Plausible Dose tAtomic Weapons Employer Facilities, December 04, 2003.