ORAU Team

Dose Reconstruction Project for NIOSH

Technical Information Bulletin – Validation of Thorium 

Annual Dose Conversion Factors

Document Number:

ORAUT-OTIB-0028

Effective Date: 02/14/2005 

Revision No.: 00

Controlled Copy No.: ______

Page 1 of 6

Subject Expert: Elizabeth M. Brackett

Document Owner

Approval: Signature on File Date: 02/08/2005

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Date: 02/04/2005

Richard E. Toohey, Project Director

Approval: Signature on File Date: 02/14/2005

James W. Neton, Associate Director for Science

Supersedes:

None
Effective Date: 02/14/2005 Revision No. 00 Document No. ORAUT-OTIB-0028 Page 2 of 6

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 01/12/2005 00-A New technical information bulletin for the 

validation of thorium dose conversion factors to 

be used for internal dose assessment. Initiated 

by Elizabeth M. Brackett.

02/14/2005 02/14/2005 00 First approved issue. Initiated by Elizabeth M. 

Brackett.
Effective Date: 02/14/2005 Revision No. 00 Document No. ORAUT-OTIB-0028 Page 3 of 6

1.0

This document validates the annual dose conversion factors used for the assessment of 232Th and 

228Th doses. 

PURPOSE

2.0

The IMBA Expert OCAS-Edition computer program is used for intake and dose assessments by the 

dose reconstructors on the Oak Ridge Associated Universities Dose Reconstruction Project for the 

National Institute for Occupational Safety and Health. The program was not designed to emulate 

independent kinetics for radionuclides with progeny chains, but the International Commission for 

Radiological Protection (ICRP) assumes independent kinetics for the progeny of several 

radionuclides. While this does not affect intake calculations, it results in inaccuracies for some of the 

doses. Dr. Keith Eckerman of the Oak Ridge National Laboratory generated annual dose conversion 

factor tables to be used in place of the IMBA values when a best estimate is needed. This document 

validates those values.

BACKGROUND

3.0

Documentation of the dose conversion factors applied in IMBA is detailed in a dose quality assurance 

appendix to the User Manual (ACJ 2004). Each of the radionuclides in IMBA was benchmarked 

against the United Kingdom’s National Radiological Protection Board’s PLEIADES program. 

PLEIADES has been used extensively by the ICRP to calculate dose coefficients for its various 

publications. Only committed doses are benchmarked for all radionuclides; committed organ doses 

calculated using IMBA and PLEIADES are tabulated and compared. 

VALIDATION 

As discussed in Section 2.0, replacement files for the thorium inhalation dose conversion factors were 

generated for use in cases where a best estimate is required. These files contain annual organ doses 

for the 65 years following an acute and 1-year chronic inhalation intake of 1 Bq of thorium. These 

values were validated in a manner similar to that used for the IMBA documentation. The annual 

organ doses in the replacement files were summed over the first 50 years and compared to the 

PLEIADES 50-year committed doses reported in the IMBA documentation. 

Dose conversion factors from chronic intakes were not included in the IMBA benchmark tabulation. 

However, while there is some variation between a chronic and acute intake in the annual doses, 

particularly in the first few years, the 50-year dose from a 1-year chronic intake is almost identical to 

that from an acute intake of the same magnitude. The replacement file chronic doses were therefore 

compared to the PLEIADES acute doses for validation purposes.

3.1 Th-232

Results of the 232Th comparisons are summarized in Tables 3-1 and 3-2. All of the replacement file 

values are within 5% of the PLEIADES values, with the majority falling within 3%.
Effective Date: 02/14/2005 Revision No. 00 Document No. ORAUT-OTIB-0028 Page 4 of 6

Table 3-1: Dose conversion factors for inhalation of 1 Bq type S Th-232

Organ Pleiades* 

(Sv/Bq)

Acute

(Sv/Bq)

% 

difference

1-yr 

Chronic 

(Sv/Bq)

% 

difference

Adrenals 4.10E-07 4.21E-07 2.65 4.16E-07 1.34

UB_Wall 4.00E-07 4.14E-07 3.42 4.08E-07 2.09

Bone_Sur 1.40E-04 1.45E-04 3.40 1.43E-04 2.37

Brain 4.00E-07 4.15E-07 3.63 4.09E-07 2.31

Breasts 4.10E-07 4.20E-07 2.37 4.14E-07 1.07

St_Wall 4.10E-07 4.17E-07 1.68 4.12E-07 0.38

SI_Wall 4.10E-07 4.15E-07 1.34 4.10E-07 0.04

ULI_Wall 4.30E-07 4.40E-07 2.23 4.34E-07 0.97

LLI_Wall 4.80E-07 4.89E-07 1.85 4.83E-07 0.66

Kidneys 2.40E-06 2.41E-06 0.55 2.39E-06 -0.39

Liver 2.50E-06 2.55E-06 2.01 2.53E-06 1.02

ET1-bas 4.70E-07 4.84E-07 2.97 4.78E-07 1.73

ET2-bas 1.10E-04 1.05E-04 -4.50 1.05E-04 -4.12

LN-ET 7.10E-04 7.09E-04 -0.21 7.02E-04 -1.13

BBi-bas 3.30E-06 3.29E-06 -0.32 3.31E-06 0.26

BBi-sec 2.80E-05 2.75E-05 -1.63 2.78E-05 -0.63

AI 1.70E-04 1.68E-04 -1.04 1.68E-04 -1.44

LN-Th 2.60E-03 2.61E-03 0.50 2.59E-03 -0.42

Muscle 4.10E-07 4.16E-07 1.53 4.11E-07 0.24

Ovaries 1.30E-06 1.31E-06 0.69 1.30E-06 -0.36

Pancreas 4.10E-07 4.18E-07 2.00 4.13E-07 0.69

R_Marrow 6.10E-06 6.28E-06 2.90 6.22E-06 1.98

Skin 4.00E-07 4.14E-07 3.62 4.09E-07 2.29

Spleen 4.10E-07 4.18E-07 2.06 4.13E-07 0.75

Testes 1.30E-06 1.33E-06 2.03 1.31E-06 0.97

Thymus 4.10E-07 4.21E-07 2.76 4.16E-07 1.45

Thyroid 4.10E-07 4.16E-07 1.53 4.11E-07 0.24

Uterus 4.00E-07 4.14E-07 3.41 4.08E-07 2.08

Lung_66 7.70E-05 7.73E-05 0.36 7.71E-05 0.16

* From IMBA documentation (ACJ 2004)
Effective Date: 02/14/2005 Revision No. 00 Document No. ORAUT-OTIB-0028 Page 5 of 6

Table 3-2: Dose conversion factors for inhalation of 1 Bq type M Th-232

Organ Pleiades* 

(Sv/Bq)

Acute 

(Sv/Bq)

% 

difference

1-yr 

Chronic 

(Sv/Bq)

% 

difference

Adrenals 4.40E-06 4.37E-06 -0.63 4.32E-06 -1.81

UB_Wall 4.40E-06 4.36E-06 -0.89 4.31E-06 -2.06

Bone_Sur 1.50E-03 1.45E-03 -3.20 1.44E-03 -4.04

Brain 4.40E-06 4.37E-06 -0.75 4.32E-06 -1.93

Breasts 4.40E-06 4.36E-06 -1.02 4.30E-06 -2.20

St_Wall 4.40E-06 4.36E-06 -0.96 4.31E-06 -2.14

SI_Wall 4.40E-06 4.36E-06 -0.83 4.31E-06 -2.00

ULI_Wall 4.50E-06 4.45E-06 -1.03 4.40E-06 -2.20

LLI_Wall 4.60E-06 4.64E-06 0.82 4.58E-06 -0.37

Kidneys 2.30E-05 2.26E-05 -1.67 2.24E-05 -2.42

Liver 2.30E-05 2.28E-05 -1.02 2.26E-05 -1.87

ET1-bas 4.40E-06 4.37E-06 -0.73 4.32E-06 -1.91

ET2-bas 1.50E-05 1.48E-05 -1.49 1.48E-05 -1.19

LN-ET 4.90E-06 4.89E-06 -0.13 4.85E-06 -1.11

BBi-bas 5.80E-06 5.84E-06 0.63 5.80E-06 0.01

BBi-sec 2.40E-05 2.43E-05 1.18 2.44E-05 1.87

AI 1.10E-05 1.11E-05 1.35 1.12E-05 1.47

LN-Th 6.70E-06 6.71E-06 0.21 6.68E-06 -0.29

Muscle 4.40E-06 4.36E-06 -0.87 4.31E-06 -2.04

Ovaries 1.30E-05 1.32E-05 1.63 1.31E-05 0.67

Pancreas 4.40E-06 4.36E-06 -0.85 4.31E-06 -2.02

R_Marrow 5.70E-05 5.74E-05 0.68 5.70E-05 -0.01

Skin 4.40E-06 4.36E-06 -0.98 4.31E-06 -2.15

Spleen 4.40E-06 4.36E-06 -0.80 4.31E-06 -1.98

Testes 1.30E-05 1.34E-05 3.00 1.33E-05 2.04

Thymus 4.40E-06 4.36E-06 -0.94 4.31E-06 -2.13

Thyroid 4.40E-06 4.36E-06 -0.87 4.31E-06 -2.05

Uterus 4.40E-06 4.36E-06 -0.90 4.31E-06 -2.08

Lung_66 1.60E-05 1.58E-05 -1.22 1.59E-05 -0.77

* From IMBA documentation (ACJ 2004)

3.2 Th-228

Reserved.
Effective Date: 02/14/2005 Revision No. 00 Document No. ORAUT-OTIB-0028 Page 6 of 6

REFERENCES

ACJ & Associates, 2004, Appendix C: Dose Quality Assurance, User Manual for IMBA Expert OCASEdition, Phase II (Version 3.2), Richland, Washington, March.