Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Evaluation of Monitoring of 

Subcontractor Construction Trades 

Workers (CTWs) at the Savannah 

River Site (ORAUT-RPRT-0083)

Timothy D. Taulbee, PhD, CHP

Research Health Scientist

Division of Compensation Analysis and Support

Advisory Board on Radiation and Worker Health 118th meeting

Santa Fe, New Mexico

August 24, 2017
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Background

• Goal: Determine whether subcontractor Construction Trades 

Workers (CTWs) were sufficiently monitored for internal 

exposure to support co-worker model development.

• June 2016 - NIOSH located and captured a fairly large set of 

job plans for the 773A building over an extended time period 

(1981-1986)

• Job plans covered all off-normal work in the area including 

operations work, DuPont construction work (maintenance), 

and subcontractor construction work. 
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Example Job Plans
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Internal Monitoring of CTWs

• DuPont CTWs (Maintenance)

• Predominately routine monitoring (DPSOL 193-302), but 

also have incident based data, and some job specific data

• Subcontractor CTWs 

• Nearly equal routine monitoring vs. incident-based 

monitoring or job specific monitoring
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Subcontractor evaluation

• Evaluated 550 

subcontractor CTW-job 

pairings (255 unique 

subcontractor workers)

• Randomly selected 110 

subcontractors (133 

subcontractor CTW-job 

pairings)

• Reasonable distribution of 

crafts from random sample
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Data Collection and Evaluation

• Nov 2016 conducted data capture at SRS to obtain 

bioassay

• Bioassay data found for 105 of the 110 subcontractor 

Construction Trades Workers (CTWs) 

• Of the 133 subcontractor CTW-job pairings, 88 individual 

subcontractor CTWs required respirator use

• Some bioassay results found for the 105 workers were for Job Plans 

that did not required use respiratory protection and were not 

considered (i.e. only considered respiratory job plan work).

• Some bioassay results preceded the date of the job plan and were 

not considered (i.e. only considered post job plan bioassay). 
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Workers with Internal Monitoring Data

Year Subcontractor 

CTW-Job Pairings 

Subcontractor CTWs 

w/respirator use

Subcontractor CTW 

w/Bioassay

Percent 

monitored (%)

1980-1981 19 18 11 61.1

1982-1983 26 20 12 60.0

1984 29 11 6 54.5

1985 43 23 18 78.3

1986 16 16 12 75.0

Total 133 88 59 67.0
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Why is this reasonable for a Co-worker 

Model?

1) We use a distribution of bioassay data to develop the coworker model, typically assign 95th% to the unmonitored

worker. 

• 67% of the total data is sufficient as long as there isn’t a bias 

in the data. 

• Since we are using the 95th%, were high exposures or incident 

data present in the random sample? - Yes

• NIOSH did not find any evidence of a bias.
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Example of incident bioassay data

• Some of these bioassay data 

are positive. 

• Some were incidents and 

subsequent follow-up 

bioassay were negative or 

below detection limits. 

Positive Bioassay result from incident involving 13 subcontractor CTWs
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Why is this reasonable for a Co-worker 

Model? cont.

2) When we looked at co-workers(1,2) of the 29 unmonitored 

subcontractor CTWs, we found 23 of the 29 co-workers were 

monitored.

(1) Co-worker listed on the same job plan as the unmonitored worker

(2) Co-worker could be DuPont Operations, DuPont CTW, or Subcontractor CTW

• If this is considered the total increases to 82 of the 88 

subcontractors (93%) were either directly monitored or a 

co-worker on the same job was monitored. 
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Why is this reasonable for a Co-worker 

Model? cont.

3) Respirator use is a reasonable surrogate for the need of 

internal monitoring, but not all respirator use requires 

bioassay.

• Some use of respiratory protection is precautionary. (i.e. in 

case something happens or if contamination is unexpectedly 

encountered)

• If there is no contamination then there is no potential for an 

intake and bioassay is not necessary. 
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

So was wearing a respirator really 

necessary?

• Yes and No! 

• Health Physicist are generally conservative in an effort to 

prevent intakes of radioactive material. 

• Radiological safety culture would rather have a worker in a 

respirator and not need it, than a worker need a respirator 

and not have it.
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Example of respirator use where bioassay 

was not needed

• No transferable 

contamination

• Air concentration less than 

0.2x10-12 uCi/cc 

• < 10% of Derived Air 

Concentration – DAC
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Why is this reasonable for a Co-worker 

Model? cont.

4) There will NOT be 100% compliance with bioassay 

monitoring of subcontractor employees

• Limited ability to enforce bioassay compliance (work restriction)

• Some workers refuse to leave bioassay

• Subcontractor move onto another job not to return 

Question before the ABRWH is:

How much data is sufficient to support the development and 

use of a co-worker model for dose reconstruction? 
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary

• 97% of the subcontractors CTWs monitored for external dose

• 67% of the subcontractor CTWs were monitored by bioassay

• 34% routine monitoring

• 33% were incident based on job specific based

• Additional 79% of remaining unmonitored subcontractors 

workers had a co-worker on the job plan with bioassay 

• 82 of 88 subcontractor CTWs had either personal monitoring or a 

monitored co-worker (93%)
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Conclusions

• Radiation dose to subcontractor Construction Trades Workers 

(CTWs) may be reconstructed with sufficient accuracy using 

routine, incident based, and/or job specific bioassay 

monitoring data available for the individual worker, using 

coworker data, or using a combination of the two

• Radiation dose to the unmonitored subcontractor 

Construction Trades workers (CTWs) can be bounded using 

the 95th% of the co-worker distribution developed from the 

monitored Construction Trades Workers.
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Status of Issues

# Issue Topic Deliverable Delivered SC&A 

Comments

NIOSH 

Response

1 Co-worker 

Models

Initial or interim ORAUT-OTIB-0081 (Rev 3) Nov. 2016 Mar. 2017 Aug. 2017

Full ORAUT-OTIB-0081 (Rev 4) Nov. 2017

2 Neptunium

ORAUT-RPRT-0065 – Np Operations Sep. 2016 Mar. 2017 Jul. 2017

ORAUT-RPRT-0077 - Identification Nov. 2016 Apr. 2017

ORAUT-RPRT-0080: PuFF Construction Feb. 2017 Aug. 2017

3 Thorium

ORAUT-RPRT-0070: Thorium Exposures - 1972 Jun. 2017

ORAUT-RPRT-0081: Thoron Exposures Apr. 2017

4 Metal 

Hydrides

ORAUT-RPRT-0072: Metal Hydride exposures Jan. 2017

5 Subcontractor 

Follow-up

ORAUT-RPRT-0083: Job Plan Evaluation of 

Construction work

Jun. 2017
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Co-worker models

• Revision 4 of ORAUT-OTIB-0081 to contain all 

remaining radionuclides of interest3

• Data completeness and QA verification completed.

Final Modeling is progressing

Scheduled completion November 2017

3Plutonium, uranium, neptunium, mixed fission products, strontium, cesium, and cobalt
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Current Work following last week’s 

Workgroup Meeting

• Respond to Findings in SC&A reviews of documents submitted 

to the Workgroup

• Develop Response to SC&A report on Subcontractor 

Monitoring 

• Assess distributions (i.e. 95th%) of DuPont CTWs vs 

Subcontractor CTWs

• Follow-up with site regarding 1995-1997 assessments on 

Internal bioassay monitoring that lead to a Notice of Violation 

(NOV) of 10CFR830 (Nuclear Safety Management)