A Review of ORAUT-OTIB-0087 for 

Extremity Doses for Mound Exposures to 

Plutonium-238

Ron Buchanan, PhD, CHP

Richard Griffiths, MS

Advisory Board on Radiation and Worker Health, 

Subcommittee for Procedure Reviews

June 21, 2023
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ORAUT-OTIB-0087

 Issued by NIOSH September 18, 2017, rev. 00.

 Provides information that may be used to determine ratios to assist in the 

assignment of extremity doses. 

 Some energy employees (EEs) at Mound were only assigned whole-body 

(WB) dosimetry. 

 However, the work they performed may have included handling or 

working around plutonium (Pu)-238.

 It would be expected that the dose to the extremities (forearm, wrist, 

hand, or finger) would be elevated in comparison with the WB dose. 

 If an EE’s extremity dosimeter results are available, those results should 

be used to assign dose to the cancer site on the extremity. If not, the 

extremity-to-WB ratio applied to the WB dose can be used to determine 

the dose to the cancer site on the extremity.
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SC&A review of OTIB-0087: Chronology

 October 26, 2022: The SPR tasked SC&A to review ORAUTOTIB-0087, revision 00

 April 21, 2023: SC&A issued (not PA-cleared) “A Review of 

ORAUT-OTIB-0087 for Extremity Doses for Mound Exposures 

to Plutonium-238” to SPR and NIOSH

 May 2023: SC&A issued a PA-cleared version
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Mound 1972 extremity dose study

 Mound initiated a study in September 1972 to determine the need 

for extremity monitoring for personnel involved in Pu-238 operations 

at the site (Bigler, 1973). 

 Wrist badges for determining gamma exposure using lithiumfluoride (LiF) thermoluminescent dosimeters (TLDs) and neutron 

exposure using nuclear track emulsion, type A (NTA) film were 

selected. 

 Workers who performed the operations were monitored for various 

lengths of time ranging from 2 to 22 weeks, with a 2-week dosimeter 

exchange frequency.
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Mound 1972–1973 fingertip dose study

 A study (Bigler & Phillabaum, 1973) was also performed 1972–1973 

with wrist and WB gamma and neutron dosimeters during work in 

gloveboxes where the workers were wearing leaded rubber gloves. 

 The monitoring approach for detecting the gamma and neutron 

dose used the same monitoring approach (i.e., LiF TLDs and NTA 

film, respectively) as the 1972 extremity study. 

 This study also involved taping TLDs to the fingertips on the second 

or third finger of each hand to determine the gamma dose to the 

fingertips. The number of days the dosimetry was worn ranged from 

3 to 10 days.
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NIOSH’s use of data from these two studies

 NIOSH used these data to determine ratios for:

– Left wrist-to-WB and right wrist-to-WB for gamma and neutron 

exposures

– Left finger-to-left wrist and right finger-to-right wrist gamma ratios for a 

limited number of applications
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Wrist-to-whole body gamma dosimetry data 

analysis

 Table 5-1 of OTIB-0087 summarizes wrist-to-WB gamma dosimetry 

data for the left and right wrist for 28 employees covering nine 

different operations involving the handling of Pu-238 at Mound. 

 NIOSH found that wrist-to-WB gamma dosimetry data were best 

represented using a Weibull distribution. 

 Figure 5-1 of OTIB-0087 provides a summary plot of the fit 

comparison for the gamma wrist-to-WB ratio. 

 NIOSH determined the Weibull distribution values were 1.3295 

(shape of curve), 1.9271 (scale), and 0.3436 (location).
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Wrist-to-whole body neutron dosimetry data 

analysis

 Table 5-1 of OTIB-0087 summarizes wrist-to-WB neutron dosimetry 

data for the left and right wrist for 28 employees covering nine 

different operations involving the handling of Pu-238 at Mound. 

 NIOSH found that the wrist-to-WB neutron dosimetry data were best 

represented using a lognormal distribution. 

 Figure 5-2 of OTIB-0087 provides a summary plot of the fit 

comparison for the neutron wrist-to-WB ratio. 

 NIOSH determined the most appropriate fit to be a lognormal 

distribution with a geometric mean of 1.5796 and geometric 

standard deviation of 2.5414.
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Finger-to-wrist gamma dosimetry data 

analysis

 Table 5-2 of OTIB-0087 summarizes finger-to-wrist gamma dosimetry 

data for the left and right wrist for six workers covering three different 

operations involving the handling of Pu-238 at Mound. 

 NIOSH found that since the data are limited, a fit comparison could not be 

determined. Therefore, NIOSH recommends the use of a normal 

distribution model. 

 From the limited dataset, NIOSH calculated an average:

• Left-hand finger-to-wrist ratio of 3.18, with a standard deviation of 0.53

• Right-hand finger-to-wrist ratio of 2.76, with a standard deviation of 0.85

 Unless it is known that a worker is right- or left-handed, NIOSH 

recommends that the higher ratio should be used (i.e., 3.18 with a 

standard deviation of 0.53).
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SC&A’s review of ORAUT-OTIB-0087

 SC&A evaluated:

– The original recorded Mound data

– NIOSH’s use of the data in constructing tables 5-1 and 5-2 and 

figures 5-1 and 5-2 of OTIB-0087

– Dose reconstruction (DR) recommendations in OTIB-0087, section 6.0

 SC&A also performed a statistical analysis of the data used in 

OTIB-0087
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SC&A’s evaluation of original Mound data 

used in OTIB-0087

 SC&A reviewed the tabulated Mound data (Bigler, 1973, PDF pp. 177–

183; Bigler & Phillabaum, 1973, PDF pp. 203–206). 

 SC&A found that the measurements were conducted using acceptable 

dosimetry methods. 

 However, SC&A found that the quantity of data was somewhat limited:

– Data from 28 employees for determining wrist-to-WB ratios

– Data from 6 employees for determining finger-to-wrist ratios

 Large variations in the resulting ratio values (0.3 to 7) were listed in 

table 5-1 of OTIB-0087 for both gamma and neutron wrist-to-WB dose 

ratios.
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Wrist-to-WB ratios as a function of operation

 SC&A reviewed the wrist-to-WB ratios to determine if there was 

a general correlation of ratio values to the operation the 

workers performed.

 SC&A found that the right and left wrist-to-WB ratios varied 

according to the type of operation being performed (for both 

gamma and neutron doses), as summarized in tables 1 and 2 

of SC&A’s review report.

 Relationship of wrist-to-WB ratios is examined in more detail in 

attachment A of SC&A’s review report.
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Caution when applying ratios to other 

operating periods or DOE sites

Finding 1: When applying ratios to other operating periods or 

DOE sites, NIOSH should have an understanding that the 

exposure conditions are similar to those used in OTIB-0087

 Considering the variations in wrist-to-WB ratio values as a function of 

operation, it is important when applying the Mound extremity ratio values 

to DRs from other operating periods at Mound or other U.S. Department 

of Energy (DOE) sites to first ascertain that the conditions of exposure to 

Pu-238 are encompassed by the Mound operations.
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SC&A’s evaluation of tables 5-1and 5-2

Observation 1: Two entries from Mound data not located in OTIB-0087

 SC&A found that NIOSH incorporated all six entries of the Mound data for 

finger-wrist-to-WB exposure into table 5-2 of OTIB-0087. 

 SC&A found that NIOSH incorporated the first four entries of the Mound 

data for finger-wrist-to-WB exposure into table 5-1.

 It does not appear that the last two entries of the Mound data for fingerwrist-to-WB exposure were incorporated into table 5-1.

 This omission would not greatly affect the results. However, it would be 

helpful for NIOSH to clarify why these last two entries appear to be 

omitted.
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SC&A’s evaluation of figures 5-1 and 5-2

Observation 2: Discrepancies in number of ratios and values between 

table 5-1 and figures 5-1 and 5-2

 Figure 5-1 reports that 55 values were used to construct the histogram and fit the Weibull 

curve. However, only 45 valid wrist-WB gamma ratios are reported in table 5-1. 

 The mean ratio is reported as 2.116 in figure 5-1, but the mean of the wrist-WB gamma 

ratios in table 5-1 is 2.143.

 Figure 5-2 reports that 53 values were used to construct the histogram and fit the 

lognormal distribution. However, there are only 43 valid wrist-WB neutron ratios in 

table 5-1. 

 Figure 5-2 lists minimum and mean neutron ratio values of 0.179 and 2.551, respectively. 

The minimum wrist-WB neutron ratio listed in table 5-1 is 0.27, and the mean wrist-WB 

neutron ratio in the table is 2.502.
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SC&A’s statistical analysis of available data

 The sparsity and variation of the data in table 5-1 suggests that the 

estimated ratios in OTIB-0087 are likely quite imprecise. There are 

several issues that suggest this:

– Sparsity of data: A relatively small number of observations are used in the 

estimation.

– Outliers: Some large outliers in the ratio measurements affect the ability to accurately 

fit empirical distributions.

– Linear relationship: The use of ratios to estimate wrist doses from WB doses 

assumes a linear relationship between the two types of doses. The linear relationship 

is not entirely evident from the data in table 5-1.

– Operation type: There are indications that the relationship between wrist doses and 

WB doses differs by operation type, which suggests the need for different estimated 

ratios by operation type for imputations to be valid.
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Result of SC&A’s analysis of available data 

 Attachment A of SC&A’s review report summarizes SC&A’s 

analysis of the data.

 As a result of this analysis, SC&A had the finding 2 about the 

ratio values.

 Finding 2: Use of upper bound may be more appropriate in 

dose reconstruction

– Considering the limitations of the data, SC&A suggests that it would be 

more claimant favorable to use an upper bound ratio, such as the 

upper limit of the confidence interval, instead of a distribution or 

average ratio value.
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NIOSH’s recommendations in OTIB-0087, 

section 6.0

 To determine the gamma dose to the wrist: Use the Weibull 

distribution in conjunction with the gamma WB dose.

 To determine the neutron dose to the wrist: Use the lognormal 

distribution in conjunction with the neutron WB dose.

 When evaluating the finger-to-wrist extremity dose:

– Use the ratio value of 3.18 times the wrist dose for the left finger dose

– Use the ratio value of 2.76 times the wrist dose for the right finger. 

– If it is not known if the worker was right- or left-handed, use the greater of 

the ratio values, 3.18.
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SC&A’s conclusions

 SC&A evaluated the original recorded Mound data, its use in 

constructing tables 5-1 and 5-2, and the DR recommendations

 SC&A also performed a statistical analysis of recorded data 

 SC&A identified two findings and two observations:

– Finding 1: Caution when applying ratios to other operating periods or DOE 

sites

– Finding 2: Use of upper bound may be more appropriate in dose 

reconstruction

– Observation 1: Two entries from Mound data not located in OTIB-0087

– Observation 2: Discrepancies in number of ratios and values between 

table 5-1 and figures 5-1 and 5-2
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References

Bigler, W. A. (1973). Extremity monitoring study of personnel in plutonium 

operations. Monsanto Research Corporation, Mound Facility, Miamisburg, Ohio. 

SRDB Ref. ID 003281, PDF pp. 177–191

Bigler, W. A., & Phillabaum, G. L. (1973). Wrist and fingertip dose measurements 

for plutonium-238 processing operations. Monsanto Research Corporation, Mound 

Facility, Miamisburg, Ohio. SRDB Ref. ID 003281, PDF pp. 203–206

Oak Ridge Associated Universities Team. (2017). Extremity doses for Mound 

exposures to plutonium-238 (ORAUT-OTIB-0087, rev. 00). 

https://www.cdc.gov/niosh/ocas/pdfs/tibs/or-t87-r0.pdf

SC&A, Inc. (2023). A review of ORAUT-OTIB-0087 for extremity doses for Mound 

exposures to plutonium-238 (SCA-TR-2023-PR087, rev. 0).