Memo to DRSC – Re: Allied DR 1 SC&A – May 12, 2015

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

MEMO

TO: Dose Reconstruction Subcommittee

FROM: John Mauro, SC&A

SUBJECT: Comments on SC&A’s ‘Method B’ Blind Dose Reconstruction of Exposure to 

Radon for a Worker at Allied Chemical and Dye Corporation in North Claymont, 

Delaware 

DATE: May 12, 2015

One of the topics discussed during the meeting of the Dose Reconstruction Subcommittee 

(DRSC) held on April 14, 2015, was exposure of a worker to radon at Allied Chemical and Dye 

Corporation in North Claymont, Delaware (Allied). The worker was an energy employee (EE) 

who worked at Allied from [redact] 1942 to [redact] 1954 and [redact] 1956 to [redact] 1975. 

This employment period spans the operational period of 1950 through 1969, when Allied was 

involved in a small-scale pilot operation recovering uranium from a phosphoric acid plant, as 

well as for most of the residual contamination period of 1970 through 1977. According to the 

Department of Labor (DOL) records and the Computer-Assisted Telephone Interview (CATI), 

the EE worked as a [redact] during both employment periods. No employee monitoring records 

or site survey records were found. The EE was diagnosed with oat cell carcinoma of the lung 

(ICD-9 Code 162.9) in [redact] 1981.

This blind dose reconstruction (DR) was summarized in SC&A’s report, Comparison of SC&A’s 

Blind Dose Reconstruction to NIOSH’s Dose Reconstruction of Case #[redact] from the Allied 

Chemical Plant and Dye Corporation, North Claymont, Delaware, December 2014. In that 

report, SC&A compares the lung doses reconstructed by NIOSH with the lung doses 

reconstructed by two independent SC&A methods (i.e., ‘Method A’ and ‘Method B’). SC&A 

performed its DR using information supplied by the Department of Energy (DOE) regarding this 

site and worker, and any other information SC&A could obtain from the open literature and from 

the NIOSH Site Research Database (SRDB). However, SC&A did not have access to NIOSH’s 

DR until the comparisons were made in the above referenced report. It is also noteworthy that, 

for this blind DR, SC&A’s ‘Method A’ (which made use of all of NIOSH’s protocols and tools) 

worked independently and did not communicate with the ‘Method B’ DR team (which was based 

on fundamental health physics principles, without necessarily relying on NIOSH guidance or 

NIOSH contractor workbooks). The following table, excerpted directly from the above-cited 

report, compares the reconstructed doses/radon progeny exposures performed by NIOSH and 

SC&A.
Memo to DRSC – Re: Allied DR 2 SC&A – May 12, 2015

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

Table 3-1. Comparison of Total External and Internal Doses to the Lung

Total Doses SC&A-Method A 

(rem)

SC&A-Method B

(rem)

NIOSH

(rem)

External Lung Doses:

 - Operational Period

 - Residual Period

 - Occupational Medical

1.041

0.194

1.886

NA

NA

NA

0.381

0.103

1.592

Internal Lung Doses:

 - Operational Period

 - Residual Period

93.679

24.635

NA

NA

15.106

0.088

Total Lung Dose 121.435 NA 17.271

Total Radon 0.812 WLM 2.115 WLM 0.214 WLM

POC 85.4% 64.1% 45.90%

NA = Not applicable.

During the DRSC meeting, one of the interesting discussions pertained to comparisons between 

the radon exposures estimated by SC&A and those estimated by NIOSH. As part of the 

Subcommittee discussions on this subject, we found that SC&A ‘Method A’ strictly followed 

NIOSH’s guidance provided in ORAUT-OTIB-0043 for the operations period and ORAUTOTIB-0070 for the residual period. During the Subcommittee meeting, NIOSH explained that 

they used fundamentally the same procedures, but divided all values recommended in OTIB0043 for the operational period by a factor of 10, because they felt that the amount of phosphate 

processed as part of Allied’s Atomic Weapons Employer (AWE) activities was so small that 

OTIB-0043, which is intended to be used for DR of large phosphate ore processing plants, would 

result in a gross overestimate of the doses; hence, the 10-fold reduction factor in the default 

radiation exposure parameters recommended in OTIB-0043. This is the main reason for the 

large differences in all exposures between NIOSH’s DR and SC&A’s ‘Method A’ DR.

This memorandum, however, is concerned primarily with SC&A’s ‘Method B’ DR. The author 

of that DR (John Mauro) decided to perform what is commonly referred to as a minimizing DR, 

by simply assuming that the workers at Allied during the AWE period were exposed to relatively 

low concentrations of radon, namely 4 pCi/L for the entire AWE contract period. This resulted 

in a radon progeny exposure of 2.115 WLM over the course of this worker’s employment at 

Allied. The intent of this simple calculation was to determine whether this assumed level of 

exposure was sufficient to result in a probability of causation (POC) of greater than 50%. As it 

turned out, this first attempt at SC&A ‘Method B’ resulted in a POC of 64.1%, and the 

‘Method B’ blind DR was concluded.

During the DRSC meeting, NIOSH and its contractors expressed that they believed that 4 pCi/L 

was not necessarily a very low radon concentration in light of the data reported in OTIB-0043 for 

phosphate plants, and the Subcommittee directed SC&A to take a closer look at this assumption, 

in light of the information provided in OTIB-0043. This memorandum provides the results of 

SC&A’s follow-up investigations into this matter.
Memo to DRSC – Re: Allied DR 3 SC&A – May 12, 2015

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

The results of these follow-up investigations are interesting for a number of reasons, creating a 

conundrum on how to address this particular set of circumstances. SC&A believes that the 

discussion that follows leads one to conclude that it is difficult to deny this worker compensation 

under the circumstances encountered at this facility.

OTIB-0043 provides guidance regarding the reconstruction of doses to workers at AWE facilities 

that processed phosphate rock for the purpose of producing various phosphate products and/or 

uranium. In the case of Allied Chemical and Dye Company in North Claymont, Delaware, our 

review of the SRDB (see Appendix 1) reveals that very little uranium was produced, but the 

reports are silent on the amount of phosphate rock that was processed. We have no information 

regarding whether Allied produced phosphate commercially during the AWE time period, nor do 

we have information regarding how much phosphate rock was processed in support of AWE 

operations. One could back-calculate the amount of phosphate rock that would need to be 

processed to produce a few pounds of uranium, but that doesn’t necessarily mean that value 

places a plausible upper bound on the amount of phosphate rock that was processed over the 

AWE time period. Nevertheless, we can agree that the amount of phosphate rock processed at 

Allied was small relative to the amount of phosphate rock processed at the facilities in Florida, 

which are used as a starting point for developing surrogate data for Allied.

Based on the above discussion, one could come to the erroneous conclusion that the 

concentrations of radon in air at the Allied facility were likely a small fraction of the 

concentrations of radon observed in phosphate processing buildings in Florida. The reason we 

consider this to be a false conclusion is that the buildings that processed phosphate rock in 

Florida were open buildings; i.e., they didn’t have walls. This issue was discussed beginning on 

page 60 of the transcript of the June 5, 2008, Blockson Work Group meeting and beginning on 

page 19 of the January 23, 2009, transcript of the Blockson Work Group meeting. The outcome 

of these discussions revealed that the radon concentration data summarized in OTIB-0043, which 

are based on a massive amount of data compiled by the Florida Institute of Phosphate Research 

(FIPR), cannot be reliably used as a surrogate for enclosed buildings that processed phosphate 

rock. It is for this reason that FIPR radon concentration data could not be used as a surrogate for 

DRs for the Blockson Chemical Company, which was a commercial phosphate processing 

company that also produced uranium in support of the weapons complex. To a large degree, this 

same issue also applies to Allied.

It is noteworthy that the concentrations of airborne radon reported for phosphate processing 

facilities in Florida are largely less than 1 pCi/L. These are the concentrations that one would 

expect outdoors at phosphate facilities, where these slightly elevated levels of outdoor radon (as 

compared to typical outdoor radon concentrations) are likely due to radon emanation from 

phosphogypsum stored outdoors. It is therefore apparent to SC&A that OTIB-0043 cannot be 

applied to closed buildings that processed phosphate rock, such as the Allied building.

Notwithstanding these types of arguments, the radon concentrations used by NIOSH in its DR 

for this case and those used by SC&A in ‘Method B’ are not necessarily wrong. The most likely 

scenario is that the building had some level of radon in it that was from naturally occurring 

sources and some that was from processing phosphate rock. The Environmental Protection 

Agency’s (EPA’s) national radon database reveals that 10.3% of private homes in Claymont,
Memo to DRSC – Re: Allied DR 4 SC&A – May 12, 2015

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

Delaware, have radon concentrations above 4 pCi/L (i.e., 64 homes out of a total of 621 tested

1

). 

The conundrum regarding this case arises from the following facts:

1. It is quite possible that the airborne concentrations of radon in the Allied building in 

North Claymont, Delaware, were a few pCi/L, perhaps 4 pCi/L or higher.

2. The amount of naturally occurring radon versus radon generated as a result of phosphate 

processing is difficult to discern.

3. The radon concentration data provided in OTIB-0043 for buildings processing phosphate 

cannot be used as a surrogate for Allied, because they are based on open buildings, as 

reported by the FIPR.

4. It requires only a few pCi/L exposure to radon and its progeny for several years to result 

in a POC for lung cancer in excess of 50%.

Given this set of circumstances, SC&A believes that it is difficult to deny this claim.

 

 

1

See http://www.dhss.delaware.gov/dph/hsp/files/hhinsideradonzip.pdf. This web site provides the results 

of EPA’s national radon testing program.
Memo to DRSC – Re: Allied DR 5 SC&A – May 12, 2015

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

Appendix 1

Review of Allied Chemical and Dye Company Files in the SRDB

SC&A reviewed all of the records in the NIOSH SRDB pertaining to Allied Chemical Corp. in 

North Claymont, Delaware. There does not appear to be any information regarding how much 

phosphoric acid was processed in the plant outside of the Atomic Energy Commission (AEC)

operations. The majority of known information on AEC activities at Allied comes from the 

Formerly Utilized Sites Remedial Action Program (FUSRAP) document published on the site in 

1977, which describes the following:

In the early 1950s, Allied Chemical was involved in research and development 

and small pilot-scale operations on uranium recovery from a phosphoric acid 

plant at North Claymont. The work, under AEC contracts AT(49-1)-610 and 

AT(49-6)-913, was performed on a small scale. Former AEC employees 

estimated that, at most, only a few pounds of uranium concentrate were produced 

(page 12 of SRDB 13209).

A document titled, “Major activities in atomic energy programs July 1951–Dec 1951” (SRDB 

40448, page 16) lists Allied Chemical as a company under AEC contract to carry out “process 

studies of uranium extraction,” indicating that AEC operations began sometime in 1951. In 

1956, AEC began a program to declassify reports and information for plants that had an annual 

production of 100 tons or less of U3O8 and Allied Chemical and Dye in Delaware was included 

on that list (pages 9–13 of SRDB 123636).

In 1977, interviews were conducted with several former employees. Handwritten notes from 

these interviews are published in the document, Report of Findings at Allied Chemical 

Corporation Site (SRDB 16503). In an interview dated November 14, 1977, one worker 

describes the amount of uranium processed at Allied as “less than 2–10 pounds of uranium 

separated, doesn’t remember a uranium analytical capability with Claymont” (page 7 of SRDB 

16503).

The FUSRAP report concluded the following concerning potential contamination at Allied:

Operations at the phosphoric acid plant ceased in the late 1960s and the plant 

was demolished in the early 1970s. The contractor, Cleveland Wrecking, 

salvaged reusable building materials and disposed of the remaining rubble in 

local landfills. The exact location on the site where the AEC work was performed 

is not known.

DOE (then the Energy Research and Development Administration) Oak Ridge 

Operations Office contacted Allied on July 18, 1977. A contact report, furnished 

to DOE Headquarters on December 12, 1977, concluded that the potential for 

uranium contamination was insignificant. DOE headquarters has approved the 

operations office recommendation that further investigation to locate and assess 

the AEC contract work area of the site be terminated. The site has been 
Memo to DRSC – Re: Allied DR 6 SC&A – May 12, 2015

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution.

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

eliminated from consideration for inclusion in the Formerly Utilized Sites 

Remedial Action Program (page 13 in SRDB 13209).

SRDB 123636: Johnson, Jesse C. Authority to declassify documents relating to the raw 

materials program. Atomic Energy Commission. 1956.

SRDB 13209: FUSRAP Elimination report for Former Allied Chemical Corporation, Chemicals 

Company (Now General Chemicals Corporation) North Claymont, DE, DOE. 1977.

SRDB 16503: Report of Findings at Allied Chemical Corporation Site. 1977.

SRDB 40448: Major activities in atomic energy programs July 1951–Dec 1951.