Workgroup Members

Wanda Munn, Chair

James Melius

Brad Clawson

Genevieve Roessler
Site Operational History

Site manufactured wet process phosphoric acid

Located in Joliet, Illinois, used Florida phosphate rock

1950-51 AEC contracted to extract uranium from H3PO4

Constructed Building 55 for separation operation

Processing continued through June 1960

All Blockson chemical production ended in 1991

Building 55 was demolished in 1996.
Department of Energy Designation

 Blockson Chemical Company at Joliet is designated as 

an Atomic Weapons Employer from l951 to 1960

 The residual period was originally defined as ending in 

2009; later revised to March, 2011.
Special Exposure Cohort History

First SEC petition, #58, received May 11, 2006

Covered all employees on the Joliet site

Covered period from March 1, 1951 to June 30, 1960

Petition approved effective October 3, 2010

Basis: Inability to reconstruct with sufficient accuracy 

the exposure of workers to radon in Building 40 where 

digestion of the phosphate rock took place.
Special Exposure Cohort History - 2

Second, i.e., current Petition #255, received February 

24, 2015

Covers residual period, July 1, 1960 - December 31, 1991

Covers all employees on the Joliet site

Dose reconstruction feasibility not relevant here since 

AEC activities were no longer under way

Residual contamination could be possible in Buildings 

40 and 55 and external phosphogypsum pile
Special Exposure History - 3

NIOSH evaluation determined dose reconstruction 

was feasible

Sanford, Cohen & Associates was directed to review 

findings November, 2015

Review returned 5 Findings and 1 Observation
Special Exposure History - 4

Workgroup addressed each item in detail on June 28, 

2016

Two Findings were determined to be Technical Basis 

Document issues and not applicable to a petition for 

claims beyond the operational period 

Three Findings and the Observation were closed.
SEC 225 Findings & Observation

Finding 1 – Issue on how Technical Basis Document 

estimates residual photon dose. Transferred to TBD.

Finding 2 – Concern on determination of external dose 

from phosphogypsum stack resolved by agreement 

that exposure was bounded by Building 55 exposure. 

Closed.

Finding 3 – Issue on residual beta dose determined to 

be a TBD concern. Transferred to TBD.
SEC 225 Findings & Observation

Finding 4 – Concern on inhalation of particulates from 

phosphogypsum stack, agreed to be bound by 

Building 55 exposure. Closed.

Finding 5 – Concern on estimates of residual radon 

exposure resolved by agreement after discussion that 

methods were reasonable and favorable. Closed.

Observation 1 – Additional comment on radon 

exposure covered by Finding 5 discussion. Closed.
Workgroup Recommendation

Based on the discussions of all questions raised with 

respect to SEC Petition 225, the Workgroup agrees 

with the NIOSH conclusion that sufficiently accurate 

dose reconstruction is possible for all covered 

Blockson Chemical Company workers during the 

residual period July 1, 1960 to December 31, 1991. 

The Workgroup therefore recommends that the 

petition be denied. 
Questions?