Effective Date: 01/29/2016 Page 1 of 15

 

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NTS RESUSPENSION ISSUES and COMMENTS MATRIX

TBD 

No. TBD Issue NIOSH response

1

On page 12, Section 4.1.2 of the TBD, the following statement 

is made: 

Therefore, dose reconstructions for individuals employed at 

NTS during the period from 1951 through December 31, 1992, 

but who do not qualify for inclusion in the SEC, can be 

performed using these data as appropriate. 

We have a concern with this statement, because the TBD 

actually provides a protocol for reconstructing the internal 

doses from resuspension of radionuclides from January 1, 

1963, through December 31, 1992.2 This statement should be 

corrected. 

We also have a concern with the following statement made in 

Appendix A of the TBD: 

If an internal exposure was suspected, bioassay was 

performed. Managing radioactive material in the form of 

devices was episodic and limited to a few workers (e.g., 

radiation safety and industrial hygiene personnel, miners, and 

experimenters). These workers are identified on the rosters 

that were published before the event, and these workers are 

likely to have bioassay results in the DOE records. 

It is our understanding that an SEC was granted in part because 

there was inadequate bioassay data and many employees were 

exposed in situations where there were no rosters, thereby 

precluding the ability to develop a coworker model. This topic 

was discussed thoroughly during the NTS WG meetings on 

October 29, 2008 (ABRWH 2008); April 23, 2009 (ABRWH 

NIOSH agrees that additional clarification should be added to 

ORAUT-TKBS-0008-4 (the NTS environmental TBD) to instruct 

dose reconstructors to include environmental inhalation and ingestion 

intakes as prescribed in Sections 4.2.1.2 and 4.2.2, respectively, 

beginning on January 1, 1963. 

NIOSH agrees and will make the following change to the Attachment 

A text: 

These workers are usually identified on the rosters that were published 

before the event, and these workers are likely to have bioassay results in 

the DOE records.
Effective Date: 01/29/2016 Page 2 of 15

 

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TBD 

No. TBD Issue NIOSH response

2009a); and December 15, 2009 (ABRWH 2009b).

2 A method for analyzing chronic environmental exposures 

associated with resuspension processes is provided for the time 

period beginning in January 1, 1963, approximately 6 months 

after the “last above ground test.” Inspection of the Anspaugh 

et al. (2002) resuspension factor equation reveals that by 180 

days after deposition, the resuspension factor drops down to 

about 5 × 10-9/m. For earlier times, closer to the end of aboveground testing, the resuspension factors, according to the 

Anspaugh model, are orders of magnitude greater. SC&A 

believes that it is possible to back extrapolate the dose 

reconstruction to mid-1962, at the end of aboveground testing. 

Such calculations would be more complete and will likely 

reveal substantially higher doses from resuspension during that 

6-month period. The intended time period of coverage for 

these calculations should be discussed and agreed upon with 

the members of the NTS WG. There is no reason that the 

important time period of July 1962 to December 31, 1962, is 

not included in the material in the TBD. 

The evaluation report for SEC-00055 (SRDB Ref ID: 150574), which 

covers the time period of 1/27/51 – 12/31/62, specifically discusses 

the inability to reconstruct doses between the cessation of testing in 

July of 1962 and the end of that year. The last paragraph of section 

4.5 states:

Above-ground testing at the NTS began on January 27, 1951, 

and concluded on July 17, 1962. NIOSH considers 

reconstruction of internal doses at the NTS feasible for periods 

after cessation of atmospheric testing beginning on January 1, 

1963. During the period of atmospheric testing, the source term 

to which workers were exposed changed with each detonation, 

due mainly to re-suspension and mixing of fallout caused by the 

blast waves. After the final above-ground test, NIOSH considers 

the radiological source term to be sufficiently stable so as to 

allow assumptions adequate for dose reconstruction. The 

extension of the SEC period through December 31, 1962, 

approximately six months after the last atmospheric test, allows 

time for the stabilization of the source term and for decay of the 

shorter-lived radionuclides associated with the final atmospheric 

tests. 

In addition, the ER for SEC-0084 (SRDB Ref ID: 77699) describes a 

model for the reconstruction of environmental internal doses 

beginning on 1/1/63. Thus, the ERs for the SECs are clear on the

time period for which environmental doses can be reconstructed. 
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TBD 

No. TBD Issue NIOSH response

_______________________________________________ 

Further confusion on this point arises from the following 

statement on page 42 of the TBD under “Instruction to Dose 

Reconstructors:” 

With the exception of cases that can be worked using the 

bounding assumption in ORAUT-OTIB-0018 (ORAUT 2005), 

environmental inhalation and ingestion intakes listed in Tables 

4-7 and 4-11, respectively, shall be applied starting in 1964. 

OTIB-0018 seems to be an inappropriate reference within the 

context of outdoor chronic exposures at the NTS. OTIB-0018 

is more appropriately employed indoors at sites that have a 

comprehensive health physics and airborne monitoring 

program, which is not the case for the NTS. 

The referenced exception does not infer that OTIB-0018 intakes 

would be applied instead of environmental intakes. OTIB-0018 

intakes are typically applied as an efficiency method to obviate the 

need to assess negative (less than MDA) bioassay data for 

noncompensable cases. When OTIB-0018 intakes are applied, the 

addition of environmental intakes is unnecessary because the OTIB0018 intakes envelope the environmental intakes. 

3

It is important that the time period to be covered be carefully 

considered by the members of the NTS WG. SC&A believes 

that the logical time period to be covered is July 1962 through 

December 31, 1992. 

________________________________________________ 

The method of environmental occupational dose reconstruction 

is strongly based upon measurements of the concentrations of 

Pu-239/240 in air samples starting in 1971. SC&A was 

originally concerned that the air-sampling locations were not 

representative of the locations where workers were exposed. 

We originally detailed these concerns in the Anspaugh report 

dated October 21, 2008 (Anspaugh 2008). At that time, these 

concerns were based on the assumption that our interest was in 

See response to Issue 2 above.

NIOSH agrees with this observation.
Effective Date: 01/29/2016 Page 4 of 15

 

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TBD 

No. TBD Issue NIOSH response

“active environments” where operational activities were 

ongoing. However, within the context of using these airsampling data as a means to characterize airborne Pu-239/240 

concentrations during relatively quiescent conditions, referred 

to as chronic environmental exposure, these concerns are 

greatly diminished. It is important to note that the current 

scope of dose estimation from residual radioactivity is limited 

to environmental dose not associated with work activities. 

Exposure during work-related activities that disturb soil is not 

included within the scope of the TBD. 

4

The soil radionuclide inventory data collected in the 1980s by 

the Radionuclide Inventory and Distribution Program (RIDP) 

(Kordas and Anspaugh 1982; McArthur 1991) characterized 

soil contamination at the site during the 1980s. However, the 

TBD extrapolates back in time to derive the soil contamination 

levels that were present on January 1, 1963,so that doses could 

be reconstructed from the resuspension process during early 

years following the end of aboveground testing. One of the 

limitations of the back extrapolation process used in the TBD 

is there is evidence that some areas were decontaminated 

(McArthur 1991, p. 34) before the RIDP measurements were 

made. Also, significant contamination occurred in Areas 20 

and 30 from Plowshare activities after 1963, and the Baneberry 

event in 1970 produced major contamination in Areas 8 and 

12. These concerns need to be addressed in terms of the degree 

to which the TBD remains scientifically sound and claimant 

favorable, notwithstanding these events. 

In order to assure that intakes and resultant doses from environmental 

intakes was not underestimated, NIOSH used the highest 

measurement of airborne plutonium to calculate reasonable intakes 

for all other years and all other areas. The highest measured airborne 

concentration measured in any area was in 1972 in Area 9 of 4.3 x 10-

3 pCi/m3

. To determine the intake, exposure to this concentration was 

assumed to be 2,400 m3 per year which resulted in a calculated intake 

of 0.381 Bq/yr. To determine bounding intakes for other 

radionuclides measured in the NTS soils but not measured by air 

sampling (e.g., Am-241, Pu-238, Co-60, Cs-137, Sr-90 and Eu-152, 

154, and 155), the maximum ratio of these radionuclides to Pu-239 

for all areas was used. These methods would mitigate the effects of 

decontamination venting in later years. In section 3.1 of the 

Resuspension Issue Status Report (Status Report on Resuspension 

Issues at the Nevada Test Site, Contract No. 211-2014-58081, Rev, 

S.Cohen & Associates, Vienna, VA, July 2015), on page 19, the 

following statement is made:
Effective Date: 01/29/2016 Page 5 of 15

 

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TBD 

No. TBD Issue NIOSH response

For example, by selecting the location and year with the highest 

annual average airborne plutonium concentration for the 

purposes of partial dose reconstruction, there is a level of 

assurance that reconstructed internal exposures are claimant 

favorable for all workers during those time periods, and also for 

earlier time periods where back-extrapolation was required. One 

could also argue that this strategy would be reasonable for 

earlier time periods and locations, even for locations that were 

cleaned-up prior to the commencement of the air-sampling 

program. 

In Section 3.1, on page 21 of the Resuspension Issue Status Report, 

the following statements appear:

The TBD acknowledges that the portion of the NTS where the 

RIDP data are provided is limited to only about one-third of the 

entire area of the NTS. However, the areas selected for the RIDP 

were those with measurable levels of contamination in soil 

above ubiquitous background. Hence, it certainly appears that a 

combination of the air-sampling data and the RIDP soilinventory data can be used to assign chronic intakes of these 

nine radionuclides to workers. In addition, if high-end airsampling and soil-inventory data are used, reconstructed doses 

associated with the chronic inhalation of these nine 

radionuclides would seem to be reasonably bounding. As 

presented in Table 4-6 of the TBD, this is, in fact, the approach 

adopted in the TBD to reconstruct radionuclide intake rates.

For these reasons, NIOSH believes the maximum intakes provided in 

Table 4-6 of the NTS environmental TBD to be scientifically sound 
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TBD 

No. TBD Issue NIOSH response

and claimant favorable even if specific consideration is given to 

decontamination activities and loss of containment incidents.

5 Derivation of the concentration of relatively short-lived 

radionuclides in soil for January 1, 1963, employed the Hicks’ 

tables (Hicks 1982) for the Small Boy event that occurred on 

July 14, 1962. In fact, the contamination in soil on January 1, 

1963, reflects fallout from numerous tests that resulted in 

surface contamination, such as the Sedan test on July 6, 1962, 

and Little Feller II on July 7, 1962, which occurred shortly 

before Small Boy, and Little Feller I that occurred after Small 

Boy on July 17, 1962. As such, NIOSH should address 

whether tests shortly before and after Small Boy on July 14, 

1962, could also have contributed substantively to the fallout 

levels in soil derived for January 1, 1963. 

_________________________________________________ 

In a related matter, the protocol used in the TBD to account 

for fractionation is overly simplistic and appears to rely 

primarily on the Small Boy event. NIOSH will need to 

demonstrate that the approach used to account for fractionation 

does not substantively underestimate doses. 

Soil radionuclide concentrations corrected to 1963 (see Table 4-5 of 

the NTS environmental TBD) only included radionuclides that are 

persistent in the environment (e.g., Am-241, Pu-238, Co-60, Cs-137, 

Sr-90 and Eu-152, 154, and 155). These radionuclides would include 

those deposited as a result of all atmospheric test and loss of 

containment incidents prior to the 1980s. The persistent 

radionuclides deposited after January 1, 1963 were still decay 

corrected back to January 1, 1963 so their contribution to the soil 

concentrations corrected to January 1, 1963 would have been 

overestimated since these incident related radionuclides would not 

have existed in the environment on January 1, 1963. The same 

overestimate would occur for any persistent radionuclides deposited 

as a result of the Plowshare program. Thus the soil radionuclide 

concentrations corrected to January 1, 1963 likely represent 

overestimates of the actual soil concentrations present at the time. 

In Section 3.4, page 25, of the NTS resuspension issues report, the 

following statement was made:

The Hicks’ tables that were used by NIOSH to support the 

reconstruction of environmental exposures onsite were actually 

originally derived for the purpose of evaluating offsite 

exposures. As a result, the Hicks’ tables understate the relative 

abundance of refractory elements onsite and overstate the 

presence of volatile elements.

In Section A.6, page 68, of the NTS environmental TBD, the process 

of adding the refractories back into the mix is discussed in some 
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TBD 

No. TBD Issue NIOSH response

detail. The discussion also includes a description of how the 

nearfield (i.e., NTS soils) was enriched with the refractories. 

Specifically, the NTS TBD states the following:

Because the Hicks data were developed to estimate offsite levels 

of fallout and resultant dose, fractionation effects were 

simulated in these data by the removal of a fraction of the 

refractory nuclides from the calculated abundances. In general, 

air drops were assumed to be unfractionated and offsite fallout 

from surface and cratering tests was assumed to have 0.4 of the 

refractory elements. For all other types of tests, offsite fallout 

was assumed to have 0.5 of the refractory elements present. 

Therefore, the refractory elements in the Hicks data must be 

adjusted to produce the best estimate of their enriched 

abundances in the onsite environment to which workers could 

have been exposed. Adjustment factors for each radionuclide 

were determined from data in Hicks (1984); this report provided 

relative abundances of radionuclides assuming no fraction, 50% 

fraction, and 90% fraction of refractory elements. From these 

data, ratios were developed for the 50% fractionation case 

(Table A-8). These ratios were used to deplete the refractory 

elements in the far-field (i.e., offsite) environment to estimate 

doses to offsite individuals. Therefore, to enrich the near-field 

(i.e., onsite) environment, the inverse of these ratios was applied 

to the Hicks SMALL BOY data (see below). These inverse ratios 

were applied twice because the Hicks SMALL BOY data were 

provided to estimate fallout in the offsite environment. The first 

application results in the data that represent no fractionation 

while the second application results in data that are enriched 

with refractory elements.
Effective Date: 01/29/2016 Page 8 of 15

 

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TBD 

No. TBD Issue NIOSH response

NIOSH believes that the methods described above represent a 

reasonable treatment of refractories in the nearfield environment. 

However, NIOSH is continuing to research the methods used in the 

Hicks (1984) report for appropriateness for use in the NTS 

environmental TBD to assure that these methods are claimant 

favorable. 

6 The levels of contamination observed in soil by the RIDP 

performed in the 1980s captured some contamination that 

occurred many years subsequent to the termination of 

aboveground testing. This is a concern that needs to be 

addressed, because the TBD is based on the assumption that all 

radionuclides observed in soil in the 1980s were as a result of 

aboveground testing that occurred in July 1962. However, 

some of the contamination was deposited many years later. 

NIOSH should explain how this affects the dose reconstruction 

process. 

_________________________________________________ 

In a related manner, the TBD makes use of the Anspaugh 

equation to derive resuspension factors in order to calculate 

airborne mass loadings and associated intake rates after 

January 1, 1963. NIOSH needs to discuss how these 

resuspension factors might be affected if there are locations 

where soil contamination occurred well after January 1, 1963. 

The persistent radionuclides deposited after January 1, 1963 were still 

decay corrected back to January 1, 1963 so their contribution to the 

soil concentrations corrected to January 1, 1963 would have been 

overestimated since these radionuclides would not have existed in the 

environment on January 1, 1963. The same overestimate would 

occur for any persistent radionuclides deposited as a result of the 

Plowshare program. Thus the soil radionuclide concentrations 

corrected to January 1, 1963 likely represent overestimates of the 

actual soil concentrations present at the time.

____________________________________________________ 

The resuspension factors derived from the Anspaugh equation were 

not used to calculate airborne mass loadings. Rather they were used 

to develop correction (normalization) factors that could be applied to 

intakes derived from the highest airborne concentration of Pu-239 

measured at the NTS (i.e, Area 9, 1972). 

With the exception of the Plowshare program (which was conducted 

at a relatively small, remote area where personnel access would have 

been difficult) soil contamination occurring after 1963 was primarily 
Effective Date: 01/29/2016 Page 9 of 15

 

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TBD 

No. TBD Issue NIOSH response

the result of loss of containment incidents. For each of these events, 

DOE attempted to identify all workers that had a potential for 

exposure to radioactive material. Those that were identified as 

having been possibly exposed were subjected to external and internal 

monitoring. In addition, except for operational activities, access to 

these newly contaminated areas was controlled. Therefore, 

estimating the potential exposure of individuals to airborne 

radioactive materials resuspended from the newly contaminated soils 

would involve the introduction of large uncertainties. 

However, NIOSH believes the use of high-end air-sampling data (i.e. 

the highest air sample concentrations ever measured at the NTS) and 

soil-inventory data in reconstructing environmental doses associated 

with the chronic inhalation of radioactive material provides 

reasonable assurance that the assigned intakes and resultant doses are 

not underestimated. 

Also, in section 5, page 29, of the resuspension issues report, the 

statement is made that “. . .a mass loading of 0.168 mg/m3 gives the 

same dose as the resuspension method, and (3) 1 mg/m3 is reasonable 

and would be more claimant favorable.” Table 7-1 of OCRWM 

(2003) provides ranges of mass loading factors for various conditions 

in the Armargosa Valley where the NTS is located. For inactive 

outdoor conditions, the table provides a triangular distribution with a 

minimum of 0.025 mg/m3, a maximum of 0.100 mg/m3 and a mode of 

0.060 mg/m3. These data do not support a mass loading of 1 mg/m3

but do suggest that the implied mass loading factor of 1.68 mg/m3 is 

sufficiently claimant favorable.

OCRWM, 2003, (Office of Civilian Radioactive Waste 

Management), Inhalation Exposure Input Parameters for the 
Effective Date: 01/29/2016 Page 10 of 15

 

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TBD 

No. TBD Issue NIOSH response

Biosphere Model, ANL-MGR-MD-000001 RREV 2 ICN 0, 

Yucca Mountain Project Office, Las Vegas, Nevada, June, 

2003. [SRDB Ref. ID: 35535] 

7

In order to prepare tables of doses to each organ and from each 

radionuclide as a function of time [which would have required 

an enormous number of Integrated Modules of Bioassay 

Analysis (IMBA) runs], NIOSH elected to prorate all doses 

based on the intake rate of Sr-90 beginning on January 1, 1963, 

and moving forward in time as the resuspension factors decline 

according to the Anspaugh equation and the radionuclide 

concentrations decline by radioactive decay. 

___________________________________________________

A review of the methods used to perform these calculations, as 

provided in Appendix A of the TBD, reveals that errors have 

been made in its use of equation A-2, which could profoundly 

In the NTS resuspension issues report in Section 3.5, page 26, the following 

statement is made:

There are two problems with this. The first is the implication 

that time zero is the time of the last detonation (i.e., July 1962), 

but this appears to be impossible, given that the authors show in 

their Table A-9 that the relative dose to the thyroid is the same 

as for 17 other organs. Due to the affinity of the thyroid for 

short-lived radioiodines, this cannot be correct.

It should be noted that Table A-9 does not provide relative doses. 

Rather, the table provides correction factor which when multiplied by 

the annual Sr-90 dose (to a particular organ) will account for short-lived 

fission and activation products. In other words, the correction factors 

given in Table A-9 are indicators of the relative importance of dose from 

Sr-90 (to a particular organ) to the total annual dose from short-lived 

fission and activation products. The reason the thyroid is grouped with 

the other 17 organs in Table A-9 is because the annual dose from the 

annual intakes of Sr-90 are similar for all 18 organs. The thyroid does 

not have an affinity for Sr-90.

___________________________________________________

In a related matter, the issues report also stated the following:
Effective Date: 01/29/2016 Page 11 of 15

 

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TBD 

No. TBD Issue NIOSH response

affect the dose fractions provided in Figures A-5 through A-11, 

and the doses calculated and reported in Tables 4-9, 4-14, and 

A-10. 

The second problem is the integration. The calculated value of 

0.026 is obviously very different from 0.0000738. 

The difference between these numbers is a factor of 365. The factor of 

0.0000738 is actually the average dose for one day – not one year as 

stated in the NTS environmental TBD. This will be corrected in the next 

TBD revision.

However, it should be noted that the integration of equation A-2 from 

Figure A-2 is not used in any way to calculate doses. The slope of 

the lines shown in Figures A-2, A-3 and A-4 of the NTS 

environmental TBD are what were used to demonstrate the relative 

importance of the lung dose from Sr-90 to the total dose from shortlived fission and activation products. The lower the slope, the lower 

the relative dose from Sr-90 when compared to the total dose from 

short-lived fission and activation products. The slope of the trend 

lines that predict the relative importance of 90Sr dose was determined 

to be 0.0001x for STORAX SMALL BOY, 0.0002x for STORAX 

LITTLE FELLER I (Figure A-3) and TEAPOT TURK (see Figure A4). Because the slope of the trend line is directly proportional to the 

relative importance of the Sr-90 dose to total dose (i.e., the larger the 

slope, the larger the relative importance of Sr-90 dose), the tests with 

the smallest slopes result in the highest multiplicative correction

factors for fission and activation products. Therefore, to ensure the 

organ dose from short-lived fission and activation products is not 

underestimated, the Hicks (1984) data for the STORAX SMALL 

BOY test were selected to be used to determine the fission and 

activation product dose correction factor. This assumption is justified 

by the fact that the test was very near the last atmospheric test (i.e., 

STORAX LITTLE FELLER I) and would therefore have been the 
Effective Date: 01/29/2016 Page 12 of 15

 

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TBD 

No. TBD Issue NIOSH response

test most likely to produce the short-lived fission and activation 

product intakes for workers at NTS after 1962 (the period for which 

organ dose from environmental intakes is calculated). 

8

A comparison of actual NIOSH dose reconstructions with the 

guidance provided in the TBD reveals that there are 

discrepancies and inconsistencies between the TBD guidance 

and the actual dose reconstructions. These inconsistencies need 

to be discussed with the WG. 

Without having the case numbers which would allow for more 

specific reasons for the observed discrepancies and inconsistencies, 

NIOSH will attempt to explain some of the observations outlined in 

Table 5 of the NTS resuspension issues report. 

1a. OTIB-0018 was utilized instead of environmental intakes 

when the NTS employment period coincided with employment at 

another site (LLNL, LANL, SNL etc.). 

OTIB-0018 intakes are typically applied as an efficiency method to 

obviate the need to assess negative (less than MDA) bioassay data for 

noncompensable cases. When OTIB-0018 intakes are applied, the 

addition of environmental intakes is unnecessary because the OTIB0018 intakes envelope the environmental intakes. 
Effective Date: 01/29/2016 Page 13 of 15

 

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TBD 

No. TBD Issue NIOSH response

1b. OTIB-0018 was applied instead of environmental intakes 

when employment was at NTS and not another site. 

Project guidance does not require the addition of environmental 

intakes if OTIB-0018 intakes have been assigned (see response 

above). 

2a. Some employment periods after 1963 were not assigned 

environmental intakes, because there was no dosimeter assigned 

to the EE for those periods. 

Current practice includes applying environmental doses for all cases 

starting in 1963. However, when the second SEC was issued in 2012, 

the interpretation was that internal doses could not be assigned 

without bioassay data. Therefore, for the next couple of years, 

environmental intakes and resultant doses were not assigned. The 

interpretation of SEC was subsequently revised and environmental 

intakes were then assigned to all cases. Further, for the 611 cases 

evaluated under PER46, if employment was after 1962, 

environmental intakes and resultant doses were assigned.

2b. Lack of a dosimeter during certain employment periods after 

1963 was not always used to preclude the assignment of 

environmental intakes. 

See response to 1b above. 

3. In some cases, OTIB-0018 was applied, but only for years 

after 1963. 

This was true for some cases because of the interpretation of the SEC. 
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See response to 2a above.

4. Four cases assigned only 10% of the environmental intake 

values. Only one of the four cases specifically mentioned this in 

the DR Report. Two of the four cases had POC values that were 

less than 10%; the other two were above 45%. 

Assignment of 10% of the environmental intakes is required for best 

estimates but not precluded for other cases.

5. Many cases did not evaluate ambient internal dose during 

NTS employment and cited the SEC and/or the lack of bioassay 

in the dose reconstruction report. 

See response to 2a above. 

6. One case assigned full environmental intakes from 1966–

1989, although the EE's covered employment was only for a 

single day in 1971 and 1982. 

This is an efficiency method that is employed because, currently, 

there is no way to truncate intakes when using the internal dose 

calculator (the CAD) tool. It should be noted that the resultant doses, 

even when the most claimant favorable assumptions are employed, 

are typically less than 0.010 rem which results in very small effect to 

the overall POC.

7. Several cases did not apply NTS environmental intakes and 

instead applied Tonopah Test Range (TTR) intake values, which 

are significantly lower than NTS intake rates (See Table 1). Not 

all of these observed cases had overlapping employment at 
Effective Date: 01/29/2016 Page 15 of 15

 

This is a working document prepared by NIOSH or its contractor for use in discussions with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or ABRWH (or their 

technical support and review contractors) positions unless specifically marked as such. This document represents preliminary positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and 

redact any information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

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No. TBD Issue NIOSH response

NTS/TTR. 

Without reviewing the cases, it is difficult to comment on these 

inconsistencies. The current practice is to apply NTS environmental 

intakes during employments periods at the NTS and Tonopah Test 

Range (TTR) intakes for periods of employment at the test range. As 

an efficiency method, NTS intakes can be used in place of the TTR 

intakes for cases that do not require a best estimate. 

9a. Some cases were not assigned environmental intakes, 

because the doses were deemed too low based on the short 

duration of covered employment. 

This practice is generally applied when visits to the NTS are one or 

two days in duration. NIOSH believes that the effort to apply the 

short-term intakes is not warranted because the resultant doses are 

always much less than 0.001 rem. 

9b. Some cases were assigned full years’ worth of environmental 

intakes even though covered employment was of short duration. 

This is an efficiency method that is used for cases that do not need a 

best estimate. As stated previously, even if the intakes are applied for 

a full year, the dose is usually less than 0.010 rem and has very little 

effect on the resultant POC.