Defense Threat Reduction Agency

8725 John J. Kingman Road, MS 6201

Fort Belvoir, VA 22060-6201

TECHNICAL REPORT

DTRA-TR-09-16

Radiation Doses to Skin From Dermal 

Contamination

HDTRA1-07-C-0015 

A. Iulian Apostoaei and 

David C. Kocher 

Prepared by:

SENES Oak Ridge, Inc.

Center for Risk Analysis

Oak Ridge, Tennessee

October 2010

Approved for public release; distribution is unlimited.

Defense Threat Reduction Agency

8725 John J. Kingman Road, Stop 6201
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection 

of information, including suggestions for reducing this burden to Washington Headquarters Service, Directorate for Information Operations and Reports, 

1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Manag ent and Budget, em

PLEASE DO NOT RETURN YOUR ORM TO THE ABOVE DDRESS.

Paperwork Reduction Project (0704-0188) Washington, DC 20503. 

F A

1. REPORT DATE (DD-MM-YYYY)

10-28-2010 

2. REPORT TYPE

Technical report 

3. DATES COVERED (From - To)

5a. CONTRACT NUMBER

HDTRA1-07-C-0015 

5b. GRANT NUMBER

 

4. TITLE AND SUBTITLE

Radiation Doses to Skin from Dermal Contamination 

5c. PROGRAM ELEMENT NUMBER

139D 

5d. PROJECT NUMBER

CS 

5e. TASK NUMBER

AH 

6. AUTHOR(S)

A. Iulian Apostoaei and David C. Kocher 

5f. WORK UNIT NUMBER

 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

SENES Oak Ridge, Inc. 

102 Donner Drive 

Oak Ridge, TN 37830 

8. PERFORMING ORGANIZATION 

REPORT NUMBER

10. SPONSOR/MONITOR'S ACRONYM(S)

DTRA RD-NTSN 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

Nuclear Technologies Directorate 

Defense Threat Reduction Agency 

8725 John J. Kingman Road, Stop 6201 

Fort Belvoir, VA 22060-6201 

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER

DTRA-TR-09-16 

12. DISTRIBUTION AVAILABILITY STATEMENT

Approved for public release; distribution is unlimited. 

13. SUPPLEMENTARY NOTES

14. ABSTRACT

This report presents a methodology for estimating radiation doses to skin from dermal contamination due to a uniform 

deposition of airborne radioactive material in specific regions of the body. This methodology includes a model to 

estimate increases in doses due to long-term retention of radioactive material on skin when removal by showering is 

incomplete. The primary focus of this report is estimation of doses from exposure to electrons (beta particles) 

emitted by radionuclides on the body surface. Estimation of doses from radionuclides that emit alpha particles also is 

considered. Models to estimate doses to skin from dermal contamination in various scenarios are described, 

including exposure to descending fallout from a nuclear weapon detonation and exposure to material resuspended 

from the ground surface by different human activities or the wind. 

15. SUBJECT TERMS

Nuclear Test Personnel Review, Veterans, Atmospheric Nuclear Weapons Test, Skin Dose, Dermal Contamination 

16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON 

Dr. Paul K. Blake

a. EPORT R

U

b.

A TRACT BS

U

c. THIS 

P E AG

U

17. IMITATION 

OF BSTRACT 

 L

 A

UU

18. NUMBER 

OF PAGES 

 

 238 19b. TELEPONE NUMBER (Include area code ) 

703 767-3384 
CONVERSION TABLE 

Conversion Factors for U.S. Customary to metric (SI) units of measurement. 

MULTIPLY BY TO GET 

 TO GET BY DIVIDE 

meters (m) 

kilo pascal (kPa) 

kilo pascal (kPa) 

meter2

 (m2) 

joule (J) 

joule (J) 

mega joule/m2

 (MJ/m2) 

*giga becquerel (GBq) 

radian (rad) 

degree kelvin (K) 

joule (J) 

joule (J) 

watt (W) 

meter (m) 

joule (J) 

meter3

 (m3) 

meter (m) 

joule (J) 

Gray (Gy) 

terajoules 

newton (N) 

kilo pascal (kPa) 

newton-second/m2

 (N-s/m2) 

meter (m) 

meter (m) 

meter (m) 

kilogram (kg) 

newton (N) 

newton-meter (N-m) 

newton/meter (N/m) 

kilo pascal (kPa) 

kilo pascal (kPa) 

kilogram (kg) 

kilogram-meter2

 (kg-m

2

) 

kilogram-meter3

 (kg/m3) 

**Gray (Gy) 

coulomb/kilogram (C/kg) 

second (s) 

kilogram (kg) 

kilo pascal (kPa)

1.000 000 x E -10 

1.013 250 x E +2 

1.000 000 x E +2 

1.000 000 x E -28 

1.054 350 x E +3 

4.184 000 

4.184 000 x E -2 

3.700 000 x E +1 

1.745 329 x E -2 

tk

 = (tof + 459.67)/1.8 

1.602 190 x E -19 

1.000 000 x E -7 

1.000 000 x E -7 

3.048 000 x E -1 

1.355 818 

3.785 412 x E -3 

2.540 000 x E -2 

1.000 000 x E +9 

1.000 000 

4.183 

4.448 222 x E +3 

6.894 757 x E +3 

1.000 000 x E +2 

1.000 000 x E -6 

2.540 000 x E -5 

1.609 344 x E +3 

2.834 952 x E -2 

4.448 222 

1.129 848 x E -1 

1.751 268 x E +2 

4.788 026 x E -2 

6.894 757 

4.535 924 x E -1 

4.214 011 x E -2 

1.601 846 x E +1 

1.000 000 x E -2 

2.579 760 x E -4 

1.000 000 x E -8 

1.459 390 x E +1 

1.333 220 x E -1

angstrom 

atmosphere (normal) 

bar 

barn 

British thermal unit (thermochemical) 

calorie (thermochemical) 

cal (thermochemical/cm2

)

curie 

degree (angle) 

degree Fahrenheit 

electron volt 

erg 

erg/second 

foot 

foot-pound-force 

gallon (U.S. liquid) 

inch 

jerk 

joule/kilogram (J/kg) radiation 

 absorbed dose 

kilotons 

kip (1000 lbf) 

kip/inch2

 (ksi) 

ktap 

micron 

mil 

mile (international) 

ounce 

pound-force (lbs avoirdupois) 

pound-force inch 

pound-force/inch 

pound-force/foot2

pound-force/inch2

 (psi) 

pound-mass (lbm avoirdupois) 

pound-mass-foot2

 (moment of inertia) 

pound-mass/foot3

rad (radiation dose absorbed) 

roentgen 

shake 

slug 

torr (mm Hg, 00

 C) 

 *The becquerel (Bq) is the SI unit of radioactivity; 1 Bq = 1 event/s.

**The gray (Gy) is the SI unit of absorbed dose.
ABSTRACT 

Many military personnel who participated in the atmospheric nuclear-weapons testing 

program were subjected to contamination of skin and clothing by radioactive particles, and such 

contamination could have been an important contributor to external doses to skin. The main 

purpose of this report is to present a methodology to estimate doses to skin from dermal 

contamination due to a uniform deposition of airborne radioactive material in specific regions of 

the body. This methodology includes a model to estimate increases in doses due to long-term 

retention of radioactive material on skin when removal by showering is incomplete. The primary 

focus of this report is estimation of doses from exposure to electrons (beta particles) emitted by 

radionuclides on the body surface. Estimation of doses from radionuclides that emit alpha 

particles also is considered. Models to estimate doses to skin from dermal contamination in 

various scenarios are described, including exposure to descending fallout from a nuclear weapon 

detonation and exposure to material resuspended from the ground surface by different human 

activities or the wind. Available data that can be used to estimate dermal contamination by 

airborne particles are discussed and summarized, including studies of deposition and retention of 

volcanic ash on human subjects in Costa Rica, studies using wind tunnels, studies involving 

direct contact with soil, and largely theoretical considerations of the effect of particle size. For 

each model developed in this report, recommended parameter values are provided as point 

(deterministic) estimates and as probability distributions to represent their uncertainty. Example 

calculations of doses to skin from beta-emitting radionuclides are used to investigate exposure 

scenarios in which the dose from dermal contamination is at least a significant fraction of the 

dose from exposure to radionuclides on the ground surface, situations in which inefficient 

showering can result in large increases in doses compared with an assumption of complete 

removal of contamination in the first shower, and uncertainties in estimated doses from dermal 

contamination and their sensitivity to uncertainties in model parameters. Doses to skin from 

contaminated clothing and from dermal contamination by direct contact with contaminated 

objects (including soil) also are discussed but are not treated in detail. The development of 

models and recommendations on parameter values in this report on the basis of limited data 

illustrates the importance of judgment in estimating doses to skin from dermal contamination. 
TABLE OF CONTENTS 

LIST OF TABLES...........................................................................................................................v 

LIST OF FIGURES ..................................................................................................................... viii 

1 INTRODUCTION .....................................................................................................................1 

2 REVIEW OF DERMAL CONTAMINATION STUDIES........................................................3 

2.1 Dust Loading on Skin .......................................................................................................4 

2.2 Interception and Retention of Fallout Particles ................................................................7 

2.2.1 Experiments Involving Deposition of Volcanic Ash...............................................8 

2.2.2 Wind-Tunnel Experiments.....................................................................................11 

2.2.3 Experiments Involving Dermal Contamination in Indoor Environments..............13 

2.2.4 Consideration of Effects of Particle Size...............................................................15 

3 MODELS TO ESTIMATE DOSES TO SKIN FROM DERMAL 

 CONTAMINATION................................................................................................................21 

3.1 Description of General Approach ...................................................................................21 

3.2 Contamination of Skin from Exposure to Descending Fallout.......................................23 

3.2.1 Dose from Single Radionuclide.............................................................................25 

3.2.2 Dose from All Radionuclides Combined...............................................................26 

3.3 Contamination of Skin from Exposure to Resuspended Material ..................................28 

3.3.1 General Properties of Resuspended Material.........................................................29 

3.3.2 Resuspension by Human Activities .......................................................................32 

3.3.2.1 Dose from Single Radionuclide....................................................................33 

3.3.2.2 Dose from All Radionuclides Combined......................................................36 

3.3.3 Wind-Driven Resuspension ...................................................................................39 

3.3.4 Resuspension by Nuclear Detonations...................................................................41 

3.4 Contamination of Skin from Other Activities.................................................................44 

3.5 Effect of Inefficient Showering ......................................................................................45 

3.5.1 Modeling of Removal of Radionuclides from Skin by Exfoliation and 

 Washing .................................................................................................................46 

3.5.2 Effect of Inefficient Showering – Acute Deposition Before First Shower............47 

3.5.3 Effect of Inefficient Showering – Continuous Deposition Before First 

 Shower ...................................................................................................................49 

3.5.4 Effect of Inefficient Showering – Deposition Continues After First Shower........51 

3.6 Modeling of Doses from Alpha-Emitting Radionuclides ...............................................53 

4 PARAMETERS IN MODELS TO ESTIMATE DOSES TO SKIN FROM DERMAL 

CONTAMINATION................................................................................................................56

i 
4.1 Interception and Retention Fraction................................................................................56 

4.1.1 Interception and Retention Fraction for Hair on Scalp..........................................57 

4.1.2 Interception and Retention Fraction for Skin of Forearms ....................................58 

4.1.3 Interception and Retention Fraction for Skin of Face............................................59 

4.1.4 Interception and Retention Fraction for Other Regions of Body...........................61 

4.1.5 Interception and Retention Fraction for Special Regions of Body........................62 

4.1.6 Interception and Retention Fraction for Material Resuspended by Winds............64 

4.2 Adjustments to Interception and Retention Fractions ....................................................65 

4.2.1 Particle-Size Adjustment .......................................................................................66 

4.2.1.1 Exposure to Small Particles ..........................................................................67 

4.2.1.2 Exposure to Large Particles ..........................................................................69 

4.2.1.3 Exposure to Unknown Particle Sizes............................................................69 

4.2.2 Enhancement of Retention Due to Moisture on Skin ............................................70 

4.2.3 Enrichment of Specific Activity ............................................................................71 

4.2.4 Activity-Weight Adjustment Factor ......................................................................73 

4.2.5 Exposure to Known Mixtures of Large and Small Particles..................................75 

4.3 Resuspension Factor .......................................................................................................76 

4.3.1 Resuspension Associated with Human Activities..................................................76 

4.3.1.1 Resuspension Due to Vehicular Traffic........................................................76 

4.3.1.2 Resuspension Due to Walking......................................................................78 

4.3.1.3 Resuspension Due to Helicopter Take-off or Landing .................................79 

4.3.2 Wind-Driven Resuspension ...................................................................................79 

4.3.3 Resuspension by Nuclear Detonations at NTS ......................................................81 

4.4 Deposition Velocity ........................................................................................................83 

4.5 Wind Speed.....................................................................................................................85 

4.6 Dose-Rate Factors...........................................................................................................86 

4.6.1 Dose-Rate Factors for Beta-Emitting Radionuclides.............................................86 

4.6.1.1 Nominal Dose-Rate Factor at Depth of 7 mg cm–2.......................................87 

4.6.1.2 Skin-Depth Modification Factor...................................................................91 

4.6.1.2.1 Skin-depth modification factor at nominal depth of 4 mg cm–2 .......93 

4.6.1.2.2 Skin-depth modification factor at nominal depth of 8 mg cm–2 .......94 

4.6.1.2.3 Skin-depth modification factor at nominal depth of 40 mg cm–2 .....95 

4.6.2 Dose-Rate Factors for Alpha-Emitting Radionuclides ..........................................96 

4.7 Efficiency of Showering ...............................................................................................101 

4.7.1 Removal of Radionuclides from Skin by Exfoliation of Skin Cells....................102 

4.7.2 Removal of Radionuclides from Skin by Showering ..........................................103 

ii 
4.7.3 Calculations to Investigate Effects of Inefficient Showering ..............................105 

4.8 Additional Discussions .................................................................................................109 

5 DOSES TO SKIN FROM CONTAMINATED CLOTHING ...............................................125 

5.1 Soil Loading on Clothing..............................................................................................125 

5.2 Deposition and Retention of Airborne Particles on Clothing .......................................126 

5.3 Modification of Dose-Rate Factors Due to Shielding by Clothing...............................128 

6 EVALUATION OF IMPORTANCE OF DOSES TO SKIN FROM DERMAL 

CONTAMINATION..............................................................................................................130 

7 SUMMARY AND CONCLUSIONS ...................................................................................138 

8 REFERENCES ......................................................................................................................143 

APPENDIX A ADDITIONAL DATA USED IN ESTIMATING DOSES TO SKIN 

FROM DERMAL CONTAMINATION ..........................................................147 

A.1 Data on Soil Loading on Skin and Clothing .................................................................148 

A.2 Surface Area of Skin.....................................................................................................156 

A.3 Resuspension Factors....................................................................................................160

A.4 References.....................................................................................................................163 

APPENDIX B ALTERNATE APPROACH TO ESTIMATING DOSES TO SKIN 

FROM DERMAL CONTAMINATION BY RESUSPENDED 

MATERIAL......................................................................................................164 

APPENDIX C PARAMETER VALUES USED TO EVALUATE IMPORTANCE OF 

DOSES TO SKIN FROM DERMAL CONTAMINATION............................168 

APPENDIX D EFFECT OF INEFFICIENT SHOWERING ON DOSE TO SKIN 

FROM DERMAL CONTAMINATION – MODELING AND 

AVAILABLE DATA .......................................................................................176 

D.1 Model of Effect of Inefficient Showering on Dose to Skin from Acute Dermal 

Contamination...............................................................................................................178

D.1.1 Period from T0 to T1 .............................................................................................178 

D.1.2 Period from T1 to T2 .............................................................................................179 

D.1.3 Period from T2 to T3 .............................................................................................180 

D.1.4 Period from TN–1 to TN..........................................................................................181 

D.2 Data on Removal of Skin Cells by Exfoliation and Efficiency of Washing in 

Removing Contamination from Skin............................................................................183 

D.2.1 Data on Exfoliation of Skin Cells ........................................................................183 

D.2.2 Data on Efficiency of Washing in Removing Contamination from Skin ............184 

iii 
D.2.2.1 General Discussion of Data and Application to Modeling of 

Inefficient Showering..................................................................................184 

D.2.2.2 Data from Study by Boeniger .....................................................................185 

D.2.2.3 Data from Study by Boeniger et al. ............................................................185 

D.2.2.4 Data from Study by Sharp and Chapman ...................................................186 

D.2.2.5 Data from Study by Friedman.....................................................................188 

D.2.2.6 Data from Study by Fogh et al....................................................................189 

D.3 References.....................................................................................................................197 

APPENDIX E EXAMPLE CALCULATIONS OF DOSES TO SKIN FROM 

DERMAL CONTAMINATION.......................................................................198 

E.1 Dermal Contamination by Descending Fallout at NTS ................................................199 

E.2 Dermal Contamination by Descending Fallout in the Pacific ......................................203 

E.2.1 Introduction..........................................................................................................203 

E.2.2 Methods................................................................................................................203 

E.2.3 Description of Parameters and Assumed Probability Distributions ....................207 

E.2.3.1 Measured Exposure Rate (I) ....................................................................207 

E.2.3.2 Bias in Instrument Reading (km) ..............................................................208 

E.2.3.3 Gamma Constant (Г)................................................................................208 

E.2.3.4 Bias to Account for Finite Area of Contaminated Surface (kf)................209 

E.2.3.5 Bias to Account for Surface Roughness (kr)............................................209 

E.2.3.6 Radioactive Decay Exponent (x) .............................................................210 

E.2.3.7 Time from Deposition on Skin Until First Shower (ΔTpost); Time 

 Between Showers.....................................................................................210 

E.2.3.8 Interception and Retention Fraction (r) ...................................................210 

E.2.3.9 Particle-Size Adjustment (PSa) ................................................................211 

E.2.3.10 Enhancement of Retention Due to Moisture on Skin (EM).....................211 

E.2.3.11 Enrichment of Specific Activity (EF)......................................................211 

E.2.3.12 Activity-Weight Adjustment Factor (AW)...............................................212 

E.2.3.13 Dose-Rate Factor (DRF) at Depth of 7 mg cm–2 .....................................212 

E.2.3.14 Skin-Depth Modification Factor (SDMF) ...............................................213 

E.2.3.15 Removal Fractions of Contamination from Skin (γj, β)...........................213 

E.2.4 Estimated Doses to Skin at Kwajalein Atoll........................................................214 

E.3 References.....................................................................................................................223 

iv 
LIST OF TABLES 

2-1 Specific activity enrichment ratios from experiments with soils labeled with 

 uranium ..............................................................................................................................17 

2-2 Skin contamination factors (ah) obtained from studies of deposition of volcanic ash 

 in CENIZA-ARENA experiments in Costa Rica...............................................................18 

2-3 Experimental details and summary of estimates of efficiency of particle retention 

on skin obtained in wind-tunnel studies.............................................................................19 

4-1 Interception and retention fractions estimated from data obtained in 

 CENIZA-ARENA volcanic-ash studies in Costa Rica....................................................111 

4-2 Summary of parameter values used to estimate electron doses to skin from dermal 

contamination...................................................................................................................112 

4-3 Summary of resuspension factors (RF, m

–1) used to estimate airborne 

 concentrations of radionuclides due to resuspension of radionuclides deposited 

 on ground surface.............................................................................................................113 

4-4 Dose-rate factors for selected alpha-emitting radionuclides deposited on skin in 

 specific regions of the body .............................................................................................114 

4-5 Summary of values of parameters used to model effect of inefficient showering on 

doses to skin from dermal contamination ........................................................................115 

6-1 Estimated doses to skin from external exposure to beta-emitting radionuclides on 

 ground surface and doses to skin from dermal contamination in selected scenarios 

 for exposure to airborne particles – Exposure at times shortly after a detonation...........136 

6-2 Estimated doses to skin from external exposure to beta-emitting radionuclides on 

 ground surface and doses to skin due to dermal contamination in selected scenarios 

 for exposure to airborne particles – Exposure at long times after detonation .................137 

A-1 Summary of studies to estimate soil loading on skin resulting from various 

 activities ...........................................................................................................................149 

A-2 Estimates of soil loading on skin in different body regions resulting from various 

 activities ...........................................................................................................................151 

A-3 Average soil loading on skin and clothing of fully equipped military personnel 

 while performing combat crawling in different environments ........................................153 

A-4 Variability of soil loading on skin (mg cm–2) of fully equipped military personnel 

 while performing combat crawling in different environments ........................................154 

v 
A-5 Variability of soil loading on clothing (mg cm–2) of fully equipped military 

 personnel while performing combat crawling in different environments........................155 

A-6 Surface area of various body regions (m2

) in adults........................................................157 

A-7 Percent of total body surface area in various body regions in adults...............................158 

A-8 Coefficients in empirical model to estimate surface area of total body based on 

individual’s height and weight.........................................................................................159 

A-9 Summary of resuspension factors associated with mechanical stresses at sites 

 where nuclear weapons were tested.................................................................................161 

A-10 Summary of resuspension factors associated with winds at sites where nuclear 

 weapons were tested ........................................................................................................162

C-1 Parameter values used to estimate doses to skin from exposure to descending 

 fallout ...............................................................................................................................170 

C-2 Parameter values used to estimate doses to skin from exposure to radionuclides 

 resuspended by vehicular traffic ......................................................................................171 

C-3 Parameter values used to estimate doses to skin from exposure to radionuclides 

 resuspended by winds at times shortly after detonation ..................................................172 

C-4 Parameter values used to estimate doses to skin from exposure to radionuclides 

 resuspended by winds at times long after detonation ......................................................173 

C-5 Parameter values used to estimate doses to skin from exposure to radionuclides 

 resuspended by blast wave in detonation at NTS ............................................................174 

C-6 Parameter values used to estimate doses to skin from exposure to radionuclides 

 resuspended by thermal pulse in detonation at NTS........................................................175 

D-1 Mean fractions of PbO initially deposited on palms of hands that was removed in 

successive 30-s wipes ......................................................................................................190 

D-2 Mean fractions of PbO deposited on palms of hands at time of each wiping that 

 was removed in successive wipes (γ) estimated from data in Table D-1 ........................191 

D-3 Measurements of radioactive contamination of 15 native Marshallese affected by 

 fallout from Operation CASTLE, Shot BRAVO in March 1954 ....................................192 

D-4 Fractional reductions in measured exposure rates at time of each shower after 

 three successive showers (γ) estimated from data in Table D-3......................................193 

D-5 Measurements of radioactive contamination of 28 military personnel affected by 

 fallout from Operation CASTLE, Shot BRAVO in March 1954 ....................................194 

vi 
D-6 Mean cumulative fractions of initially deposited labeled soil on forearms of 

 volunteers that was removed in successive washings......................................................195 

D-7 Mean fractions of labeled soil deposited on forearms at time of each washing that 

 was removed in successive washings (γ) estimated from data in Table D-6...................196 

E-1 Probabilistic estimates of electron doses to skin from dermal contamination by 90Sr 

 in descending fallout at NTS and comparison with dose from exposure to 90Sr on 

 ground surface..................................................................................................................202 

E-2 Summary of parameter values used in estimating electron doses to skin of the face 

 from dermal contamination by descending fallout ..........................................................216 

E-3 Dimensions of typical ships of U.S. Navy (1940–1945) .................................................218 

E-4 Deterministic and probabilistic estimates of electron doses to skin from dermal 

contamination by descending fallout for participants on ship stationed at 

 Kwajalein Atoll during Operation SANDSTONE...........................................................219 

E-5 Sensitivity analysis of probabilistic estimates of electron doses to skin of the face 

 from dermal contamination by descending fallout from Shot YOKE for 

 participants on ship stationed at Kwajalein Atoll during Operation SANDSTONE.......220 

E-6 Deterministic and probabilistic estimates of electron doses to skin from dermal 

contamination by descending fallout for participants on land at Kwajalein Atoll 

 during Operation SANDSTONE .....................................................................................221 

E-7 Sensitivity analysis of probabilistic estimates of electron doses to skin of the face 

 from dermal contamination by descending fallout from Shot YOKE for 

 participants on land at Kwajalein Atoll during Operation SANDSTONE ......................222 

vii 
viii 

LIST OF FIGURES 

2-1 Variability of contamination factor, ah, for hair obtained in studies of deposition of 

volcanic ash in CENIZA-ARENA experiments ................................................................20 

3-1 Time sequence of occurrences in scenario involving multiple days of deposition 

 onto skin due to wind-driven resuspension followed by long-term exposure of skin 

 resulting from inefficiency of showering in removing contamination ..............................55 

4-1 Cumulative weight distributions of volcanic ash particles in personnel 

 contamination studies during eruption of Irazu Volcano in Costa Rica ..........................116 

4-2 Cumulative weight distributions of particles in fallout at NTS .......................................117 

4-3 Electron dose-rate factors at various depths in skin vs emitted electron energy for 

monoenergetic sources deposited uniformly on the body surface...................................118 

4-4 Dependence of dose to skin after first shower for normal and highly efficient 

 showering on time after detonation when deposition on skin ceased (T0) and 

 time to first shower (ΔTpost); calculations assume deposition on trunk of body..............119 

4-5 Dependence of dose to skin after first shower in different regions of body on 

 time after detonation when deposition on skin ceased (T0), assuming highly 

 efficient showering and time to first shower (ΔTpost) of 6 hours .....................................120 

4-6 Dependence of dose to skin to time of first shower, dose to skin after first shower, 

 and total dose on time to first shower (ΔTpost), assuming normal showering and 

 time after detonation when deposition on skin ceased of 2 hours; calculations 

 assume deposition on trunk of body ................................................................................121 

4-7 Dependence of dose to skin to time of first shower, dose to skin after first shower, 

 and total dose on time to first shower (ΔTpost), assuming normal showering and 

 time after detonation when deposition on skin ceased of 6 months; calculations 

 assume deposition on trunk of body ................................................................................122 

4-8 Dependence of dose to skin to time of first shower, dose to skin after first shower, 

 and total dose on time to first shower (ΔTpost), assuming normal showering and 

 time after detonation when deposition on skin ceased of 6 months; calculations are 

 same as in Fig. 4-7, except additional dose during continuous deposition on skin 

 for period of 4 hours is included......................................................................................123 

4-9 Uncertainties in doses to skin after first shower for normal and highly efficient 

 showering and different times after detonation when deposition on skin ceased 

 (T0), assuming time to first shower of 6 hours; calculations assume deposition on 

 trunk of body....................................................................................................................124 
1. INTRODUCTION 

Many military personnel who participated in the atmospheric nuclear-weapons testing 

program were subjected to contamination of skin and clothing by particles carrying beta-emitting 

radionuclides, and such contamination could have been an important contributor to external 

doses to skin. Deposition of radioactive particles on skin and clothing may have occurred as a 

result of exposure to descending fallout from detonation of a nuclear weapon or exposure to 

radioactive material that was resuspended from the ground surface by winds, by human activities 

(e.g., vehicular traffic), or by the blast wave produced in another detonation. Contamination of 

skin and clothing also may have occurred as a result of direct contact with contaminated objects 

or contaminated soil on the ground. 

A committee of the National Research Council (NRC 2003) reviewed the methodology 

used by the Defense Threat Reduction Agency (DTRA) and its contractors to estimate doses to 

military participants in the atmospheric weapons testing program. The NRC committee’s review 

indicated that none of the estimated doses to skin in any exposure scenarios included electron 

doses due to contamination of skin or clothing, even though the possible importance of this 

exposure pathway has been acknowledged (Barss 2000). 

The main purpose of this report is to present a methodology that can be used to estimate 

doses to skin from dermal contamination due to a uniform deposition of airborne radioactive 

material in specific regions of the body.1

 This report focuses on doses from electrons (beta 

particles) emitted by radionuclides deposited on skin or clothing, but doses from radionuclides 

that emit alpha particles also are discussed. Section 2 summarizes various experimental data 

related to deposition and retention of particles on skin. Section 3 presents modeling approaches 

to estimate levels of dermal contamination and doses to skin. Following a description of the 

general approach in Section 3.1, models are developed that apply to descending fallout from a 

nuclear weapon detonation (Section 3.2), deposition of radioactive material that is resuspended 

from the ground surface (Section 3.3), or direct contact with contaminated objects or 

contaminated surface soil (Section 3.4). Section 3 also presents models to estimate the effects of 

inefficient showering on doses to skin from dermal contamination (Section 3.5) and to estimate 

 

1

 For purposes of estimating dose, “skin” refers to radiosensitive tissues in the basal layer, which is the 

inner layer of the epidermis containing basal cells that continually divide to produce squamous cells. 

1
doses from alpha-emitting radionuclides deposited on skin (Section 3.6). For each modeling 

approach discussed in this report, Section 4 provides recommended parameter values, including 

point (deterministic) estimates and probability distributions to represent their uncertainty. 

Doses to skin from contamination of clothing by beta-emitting radionuclides are 

discussed in Section 5. The importance of electron doses to skin from dermal contamination 

relative to doses to skin from exposure to beta-emitting radionuclides on the ground surface in 

various exposure scenarios is investigated in Section 6. Section 7 provides a brief summary of 

developments in this report and highlights important conclusions. 

This report includes several appendices. Appendix A presents a summary of data that 

can be used to estimate soil loadings on skin and clothing resulting from different human 

activities, data on the surface area of skin in different regions of the body, and data on 

resuspension factors associated with natural and human stresses. Appendix B describes an 

alternative approach to estimating doses to skin due to deposition of radioactive material that is 

resuspended from the ground surface. Appendix C provides a summary of parameter values that 

were used to investigate the importance of electron doses to skin from dermal contamination 

compared with doses from exposure to beta-emitting radionuclides on the ground surface in a 

variety of exposure scenarios. Appendix D provides data and modeling details on the efficiency 

of showering in removing deposited material from skin and the effect of inefficient showering on 

doses to skin from dermal contamination. Finally, Appendix E provides example calculations of 

electron doses to skin from dermal contamination, including quantification of uncertainties in 

estimated doses and investigations of the sensitivity of uncertainties in estimated doses to 

uncertainties in individual parameters. 

2
2. REVIEW OF DERMAL CONTAMINATION STUDIES 

Doses to skin from dermal contamination depend on the extent of deposition and 

retention of radioactive material on skin. This section summarizes the findings of experimental 

and theoretical studies on deposition and retention of particles on skin. These findings are 

important in developing modeling approaches presented in Sections 3.1 to 3.4. Some of the data 

that were extracted from those studies and used to develop estimates of model parameters are 

presented and discussed in this section. Additional data are presented in Appendix A.1. 

Various kinds of particles can deposit and accumulate on skin, including soil particles 

with different percentages of clay, loam or sand, ash particles, debris from a weapon detonation, 

or dust particles. Different types of particles have been used in studies of dermal contamination. 

The type of particle is mentioned when known, and the effect of particle type on levels of dermal 

contamination is discussed to the extent possible. When the particle type is not specified, the 

term “soil particle,” “dust particle,” or simply “particle” is used. 

Doses from radioactive particles deposited on skin depend on the specific activity 

(activity per unit mass) of the particles (μCi g–1), the mass of particles per unit area of skin 

(g cm–2), the dose rate per unit activity concentration on skin (rem h–1 per μCi cm–2

skin), and the 

exposure time (h).2 In the NTPR Program, doses to skin usually are calculated using estimates 

of activity concentrations on skin (μCi cm–2

skin) that are obtained by methods that avoid use of 

the specific activity of particles, which generally is unknown in cases of exposure of milita

participants at atmospheric weapons tests. 

ry 

 

The activity of radionuclides in the environment where military participants were 

exposed usually is expressed in terms of an activity concentration on the ground (Ci m–2

ground), 

which is estimated on the basis of historical measurements of external exposure rates in air. 

Thus, an approach to estimating doses from dermal contamination should use such a quantity. 

Different types of studies have investigated the accumulation of soil particles on skin 

under various conditions. Section 2.1 describes studies that provide information on the mass 

2

 Except as noted, conventional units of activity (Ci) and equivalent dose (rem) are used in this report to 

be consistent with units used in the Nuclear Test Personnel Review (NTPR) Program to assess doses to 

military participants at atmospheric weapons tests.

3
loading of particles per unit area of skin (g cm–2) by any means (e.g., handling of different types 

of soil or performing common activities, such as gardening). Section 2.2 describes 

measurements of interception and retention of airborne particles on skin, which is specified as a 

fraction of the mass of particles deposited per unit area of soil (g cm–2

soil) that is intercepted and 

retained by a unit area of skin. 

2.1. Dust Loading on Skin 

Doses to skin from dermal contamination depend on the mass of radioactive particles that 

adhere to skin per unit area. A comprehensive review of studies of adhesion of soil to skin under 

a variety of conditions was performed by the U.S. Environmental Protection Agency (EPA 

1997). Two important studies are those by Driver et al. (1989), which was included in EPA’s 

review, and Sheppard and Evenden (1994). Those studies describe measurements of adhesion of 

soil particles under conditions of direct contact of skin with soil (e.g., concentrations of soil on 

hands resulting from touching or handling soil). Other studies considered in EPA’s review 

investigated accumulation of soil on skin during various activities, such as playing outdoor 

sports, gardening, farming, or engaging in archeological investigations. Studies reviewed by 

EPA (1997) provide important information on the efficiency of soil adhesion to human skin in 

different situations, including resuspension from the ground surface by walking, running, or 

mechanical disturbances. In addition to EPA’s review, Kochendorfer and Ulberg (1967) 

published a largely theoretical study of human exposure to particulate debris from break-up of 

nuclear-powered aerospace vehicles that provides insight into important aspects of particle 

interception and retention on skin. Other experiments include those reported by Black (1962), 

who studied accumulation of soil on clothing and skin of military personnel who were dressed in 

full combat fatigues while crawling under simulated combat conditions for several hundred feet 

through two test areas (bare soil and dry clipped grass) that were contaminated with soil particles 

labeled with 140La. 

The main findings of the studies noted above are summarized as follows. 

 Particle size is the most important parameter that determines adhesion to skin. The 

smaller the particle size, the more efficient the adhesion to skin. 

4
 Particles of diameter3

 less than 2 m, which are of the same scale as surface roughness 

features of skin, can be incorporated into the skin surface and be very resistant to 

cleaning (especially clay particles). 

 Particles of diameter greater than 50 m adhere to bare skin (i.e., dry particles on dry 

skin) much less efficiently than smaller particles (Sheppard and Evenden 1994). 

However, larger particles can be trapped by hair and retained on or close to skin. 

 Soil loadings on skin of the hands of adults under conditions of contact of dry skin with 

dry soil measured by Driver et al. (1989) were about 1.4 mgsoil per cm2

skin for particle 

sizes less than 150 m, 1 mgsoil per cm2

skin when the maximum particle size was 

increased to 250 m, and 0.6 mgsoil per cm2

skin for unsieved soils. Particle size was the 

most important determinant of soil loading, while soil type and organic content were less 

important. Experiments by Sheppard and Evenden (1994) indicated soil loadings of 0.2 

to 2.0 mgsoil per cm2

skin, with a typical value of 0.8 mgsoil per cm2skin, for 11 types of dry 

soils sieved through a 5-mm mesh. Thus, a typical soil loading of dry soil on dry skin 

under contact conditions is about 1 mgsoil per cm2

skin. 

 Lower soil loadings occur if skin is partially protected by clothing or if contact with soil 

is inadvertent. Studies in which the amount of soil on skin was measured after activities 

such as gardening, farming, and playing sports (EPA 1997) or performing combat 

crawling (Black 1962) indicated that soil loading varies in different regions of the body. 

The highest accumulations of soil were observed in places where skin contacts soil (e.g., 

hands, wrists, knees, elbows) or in wrinkles of skin. The lowest soil loadings were 

observed on skin of the face. 

 Soil loading on skin depends on an individual’s activity [see Appendix A.1, Tables A-1 

and A-2 reproduced from EPA (1997) and Tables A-3 and A-4 based on data reported by 

Black (1962)]. The largest soil loadings were observed for such outdoor workers as 

gardeners, farmers, or earth-moving machine operators (up to 0.7 mg cm–2 on hands), 

followed by individuals who engaged in outdoor recreation activities (e.g., soccer, 

 

3 In contrast to studies of aerosols, in which different types of diameters can be defined to capture the 

aerodynamic properties of particles, the term “particle diameter” is used in this report as an indicator of 

the physical size of particles, mainly to differentiate small particles from large particles.

5
football, rugby; up to 0.4 mg cm

–2 on hands) and individuals who engaged in indoor 

activities (e.g., greenhouse workers; up to 0.04 mg cm–2 on hands). 

 Soil loading on clothing can be 10 to 100 times greater than on skin (0.5 to 13 mg cm–2) 

when clothing is contaminated by contact (e.g., after combat crawling). Soil loading on 

clothing greater than 5 mg cm–2 has the appearance of “caking” (Black 1962). 

 Experiments by Sheppard and Evenden (1994) also indicated that typical soil loadings on 

skin resulting from touching soils with bare hands increase to about 2 mgsoil per cm2

skin

when soil is moist or wet. At soil loadings of 2 mgsoil per cm2

skin or more, soil is visible 

on skin and individuals would normally wash their hands, which would lead to short 

retention times on skin. One can infer from those experiments that if soil is moist, the 

soil loading under conditions of direct contact with surface soil may increase from about 

0.8 mgsoil per cm2

skin to about 2 mgsoil per cm2skin, or by a factor of about 2.5. 

 In the study of military personnel by Black (1962), perspiration was noted visually to 

have a marked effect on soil loading on skin. Those subjects whose skin was dampened 

by perspiration showed high soil loadings. However, as soon as skin dried, much of the 

soil dropped off. No quantitative statements were made by Black (1962) to indicate a 

relationship between soil loading and the amount of moisture on skin. In the absence of 

data, one could assume that accumulation of dry soil particles on moist skin is similar in 

magnitude to accumulation of moist soil on dry skin. 

 Kochendorfer and Ulberg (1967) described results of an experiment performed at Oak 

Ridge National Laboratory (ORNL) by Fish et al. (1964) that was designed to determine 

the duration of retention of particles on skin. Those studies used wax and plastic spheres 

with diameters ranging from 50 to 1,000 m that were loaded with fluorescent powder. 

The retention time was found to depend on surface conditions of skin, including oiliness 

and dampness (as from perspiration), the weight of particles, and the level of activity of 

the individual. However, no quantitative relationship between the degree of moisture or 

oiliness of skin and the retention time was reported. The number of particles remaining 

on skin was found to decrease exponentially with time, and the mean retention time on 

skin decreased with increasing particle diameter from 3 to 6 hours for 60 m particles to 

1.5 to 3 hours for 1,000 m particles. The mean retention time for 40 μm particles was 

6
 Experiments by Sheppard and Evenden (1994) used soils labeled with uranium. Since 

uranium was added to soil,4

 it is likely that the uranium accumulated on the surface of 

soil particles. Those experiments indicated that the specific activity of soil (activity of 

uranium per unit mass of soil) retained on skin is greater than the specific activity of 

labeled soil. This enrichment of specific activity probably was due to the greater 

retention of smaller particles on skin noted above. Because uranium presumably was 

distributed on the surface of soil particles, smaller particles had a higher specific activity 

than larger particles. Thus, skin preferentially retains particles with higher specific 

activity when radionuclides are concentrated on the surface of particles. Enrichment 

factors, defined as ratios of the specific activity of uranium in soil retained on skin to the 

specific activity of uranium in soil that contacts skin, for different soil types measured by 

Sheppard and Evenden (1994) are given in Table 2-1. Enrichment factors were as low as 

1.2 to 2.4 for clay and loam soil particles and as high as 10 for sand particles. 

 Soil type is less important in determining loading on skin than particle size or moisture 

content. For example, soil loading is not strongly influenced by the clay or organic 

content of soil. 

2.2 Interception and Retention of Fallout Particles

A simple way to describe accumulation of airborne particles on skin is to quantify the 

fraction of the mass of incident particles that is intercepted and retained on skin. This section 

describes two sets of experiments that were designed to determine the magnitude of the 

interception and retention fraction of particles on skin. One set of experiments involved 

 

4 Uranium oxide powder was dissolved in concentrated nitric acid to obtained uranyl nitrate solutions, 

which were used to treat soils.

7
deposition of ash following a volcanic eruption in Costa Rica; the other set involved specially 

prepared particles and controlled air flow in a wind tunnel. 

2.2.1 Experiments Involving Deposition of Volcanic Ash

Interception and retention of airborne particles on skin of humans was studied in the 

aftermath of the eruption of the Irazu Volcano in Costa Rica. Experiments known as the 

CENIZA-ARENA (ash-sand) studies (Miller 1966a,b,c; 1967) consisted of measurements of the 

accumulation of ash and soil particles on subjects’ skin, clothing and hair while performing 

normal activities (i.e., mostly walking or standing) during passage of a cloud of debris released 

from the volcano. The parameter of interest measured in those experiments is the skin 

contamination factor (ah; in cm2

), which is defined as the mass of material that accumulated on a 

specific portion of an exposed body surface (wh; in g) divided by the mass of the deposit per 

unit area on the ground surface during the period of exposure (m; in g cm–2). This factor 

accounts for interception of airborne particles and initial retention on skin. Thus, it accounts for 

effects of weathering during the deposition event and shortly afterwards5 until contamination 

was removed for measurement. Similar factors have been reported for accumulation of particles

on clothing and in hair. 

 

Costa Rica has a warm and humid climate. Irazu Volcano is located in the central 

highlands of Costa Rica, where the average temperature is 22–24C (72–75F), with little 

seasonal variation, and the average relative humidity is about 70%. Annual rainfall is about 

200 cm, with the dry season from December to April and the rainy season from May to 

November. The personnel contamination experiments took place from June 15, 1965, to 

January 7, 1966 (Miller 1966c, pages 213–214). Given the warm temperatures and humid 

conditions, the observed interception and retention of particles on skin is expected to be 

enhanced compared with interception and retention when the humidity is low. 

5 Personnel in those studies worked at various sites that were affected by ash fallout from the Irazu 

Volcano. Deposition on their skin ended when they boarded a Jeep that would take them to the location 

of the laboratory where ash deposited on skin was collected. We could not find statements about the time 

delay between the end of deposition and collection of ash from skin.

8
Ash particles from the Irazu Volcano eruption were similar in sizes and shapes to 

particles from nuclear weapons fallout. At diameters between 50 and 100 m, for example, the 

similarity between the two types of particles was apparent from a comparison of photographs of 

volcanic ash particles and particles from nuclear weapons fallout collected near ground zero. 

From this point of view, the volcanic ash studies are relevant to modeling interception and 

retention of fallout particles produced by detonation of nuclear weapons. 

Information obtained from the volcanic ash studies of relevance to assessing doses to skin 

from dermal contamination of military participants is summarized as follows: 

 During some days when the CENIZA-ARENA studies took place, volcanic ash contained 

a distribution of particle sizes that was heavily weighted towards large particles 

(> 100 m). That distribution of particle sizes is similar to the distribution of particle 

sizes in nuclear weapons fallout that deposits near ground zero and, thus, is relevant to 

dose reconstructions for military personnel at the Nevada Test Site (NTS). However, that 

particle-size distribution is different from particle-size distributions in fallout at larger 

distances from ground zero, which contained mostly smaller particles. Since military 

personnel who participated at nuclear weapons tests in the Pacific usually were located 

tens or even hundreds of miles from ground zero, an adjustment of estimates of 

interception and retention obtained from the volcanic ash studies to account for the 

preponderance of smaller particles is needed in such cases. 

 In the CENIZA-ARENA studies, the particle-size distribution of volcanic ash that 

accumulated on skin, clothing or hair had a larger number of small particles compared 

with the particle-size distribution of ash that deposited on the ground. Particles with 

diameters as low as 40 m were identified on all individuals. For some individuals, 

particles sizes as low as 3 m were detected. 

 As summarized in Table 2-2, values of the skin contamination factor (ah) measured in the 

CENIZA-ARENA studies varied over the following ranges: 

– Face: 2.5–19 cm2 [geometric mean (GM) of 7 cm2; two measurements]; 

– Forearms and hands: 66–172 cm2

 (GM of 115 cm2; three measurements); 

– Forehead: 7.5 cm2 (one measurement); 

9
– Inside ears: 5.8–6.8 cm2

 (GM of 6 cm2; three measurements); 

– Hair, male, crew cut: 10–585 cm2 [eight measurements, three with incomplete 

collection of material; as indicated in Fig. 2-1, the remaining five measurements 

follow a lognormal distribution with a GM of 182 cm2 and geometric standard 

deviation (GSD) of 2.8]; 

– Hair, male, medium cut: 17–620 cm2

 [eight measurements, two with incomplete 

collection of material; as indicated in Fig. 2-1, the remaining six measurements 

follow a lognormal distribution with a GM of 163 cm2

 and GSD of 2.56]; 

– Clothing (blouse): 385 cm2

 (one measurement); 

– Range of all measurements on skin and hair: 2.5–620 cm2

. 

 In general, larger particles were retained to a greater extent on skin covered with hair than 

on skin without hair. Values of ah for forearms were relatively large and similar to those 

observed for hair; they probably reflect an enhanced retention due to the presence of hair 

on forearms. 

 The most numerous measurements of ah were reported on the hair of two males, with 

different styles of haircut. These data provide an indication of the variability of ah for a 

single individual exposed at different times. As shown in Fig. 2-1, measured skin 

contamination factors for hair for the two individuals follow lognormal distributions with 

similar GMs (182 and 163 cm2

) and GSDs (2.8 and 2.56). When the single measurement 

of ah for hair for a third individual in Table 2-2 is included, the GM of all measurements 

combined is 164 cm2

, and the GSD is 2.45. 

In applying data from the studies of interception and retention of volcanic ash particles on 

skin to estimation of doses to skin from exposure to nuclear weapons fallout, it is important to 

understand the limitations of the data. The main issues that may affect how data from these 

studies are applied in estimating doses to military participants are summarized as follows: 

 Values of the skin contamination factor (ah) were determined only under conditions of 

standing or walking. 

10
 Values of the skin contamination factor were determined only on limited portions of the 

body (i.e., forearms and hands, face, forehead, hair, and inside the ears). 

 The definition of the “face” is not clear. It may be reasonable to assume that “face” 

includes the forehead, even though values of ah for “forehead” were reported separately. 

 There are no measured ah values for skin of the torso or legs. 

 Even if ah values for bare skin of the torso or legs were available, deposition of particles 

on skin in those regions of the body often occurs in the presence of clothing, which 

reduces, but does not eliminate, skin contamination. Clothing could act as a filter to 

remove large particles and prevent their deposition on skin. However, fine particles have 

a greater tendency to travel with the flow of air under clothing, especially during the 

summer when clothing is worn loosely. 

 Additional doses to skin can result from accumulation of radionuclides on clothing. 

Thus, it is important to quantify activity concentrations on clothing due to contamination 

by descending or resuspended fallout or by direct contact with contaminated materials. 

The CENIZA-ARENA studies offer only one measurement of the skin contamination 

factor for clothing, without specifying the part of clothing for which ah was measured. A 

discussion of contamination of clothing is presented in Section 5. 

2.2.2 Wind-Tunnel Experiments 

In a set of experiments involving controlled conditions in a wind tunnel, Asset and Pury 

(1954) studied deposition of small, wind-driven particles on human skin. Those experiments 

used specially prepared spherical particles with median diameters less than 10 m that were 

dispersed in an air flow with controlled wind speed. Results of those studies are given in 

Table 2-3. An interpretation of findings of the wind-tunnel studies as they may apply to dermal 

contamination of military participants is summarized as follows: 

 Forearms of volunteers were exposed for 10, 15 or 30 minutes to particles with mass 

median diameters (MMD) of 1.3 or 6.5 m that were carried by simulated winds at 

speeds of either 2 or 5 miles per hour (mph). The aerosol used was triphenyl phosphate 

11
 Retention of particles was enhanced on the hairy part of forearms, compared with the 

hairless part. Retention increased when the wind speed was increased from 2 to 5 mph, 

an effect which was attributed to the increased number of particles impacting the skin. 

 An efficiency of particle retention, defined as E = m/A where m is the mass of aerosol 

deposited per unit area of forearm during exposure and A is the mass of aerosol that 

passed through a unit area whose plane is perpendicular to the direction of flow, was 

estimated. This efficiency of retention is similar to an interception and retention fraction 

discussed in Section 3.2, which is estimated by dividing a skin contamination factor (ah) 

obtained in the volcanic ash studies described in Section 2.2.1 by the surface area s of 

skin in the region of the body where ah was measured. The efficiency of retention of 

6.5 m particles varied from 0.54 to 0.9% at a wind speed of 5 mph (2.2 m s–1), and a 

value of 0.17% was estimated at a wind speed of 2 mph (0.89 m s–1). There was no 

measurable accumulation on skin when 1.3 m particles were used, which indicates that 

very small particles (d < 3 m) carried by winds are transported around the body with the 

air flow, thus resulting in a probability of impaction of essentially zero. 

 Landahl (1944), as cited by Asset and Pury (1954), performed similar experiments using 

particles with an MMD of 4.5 μm, but having a wider particle-size distribution with a 

maximum diameter of 70 μm. Efficiencies of retention of about 2% at a wind speed of 

5.5 mph (2.5 m s–1) were reported. The difference in results compared with those 

obtained by Asset and Pury (1954) was attributed to differences in the particle-size 

distributions in the two experiments. Only 7% of the particles in experiments by Asset 

and Pury (1954) were larger than 10 m (maximum diameter of 20 m), while 20% of 

the particles in the experiments by Landahl (1944) were larger than 10 m (maximum 

diameter of 70 m). 

12
The wind-tunnel experiments summarized above are not entirely relevant to assessments 

of doses from deposition of nuclear weapons fallout because they used very small particles, they 

were performed under dry conditions using specially prepared spherical particles and constant 

wind speeds, and they involved only short exposure times (less than 30 minutes). 

2.2.3 Experiments Involving Dermal Contamination in Indoor Environments

More recently, contamination of human skin in indoor environments was studied by Fogh 

et al. (1999). The purpose of that study was to gather information that could be used to estimate 

doses to skin from dermal contamination by radioactive particles released from a nuclear facility. 

The experiments involved particles with diameters ranging from 0.02 to 20 m in indoor dry 

environments with little or no air movement. Particles were labeled with stable tracers that could 

be activated by neutrons or with fluorescent tracers, depending on the type of study. The various 

experiments included studies of deposition of particles on skin, hair or clothing of human 

volunteers and on samples of rat skin or other materials (filter paper, felt and polyethylene) 

mounted on fixed cylinders. Studies of dermal contamination investigated deposition of 

particles, contamination by contact transfer, retention and clearance of particles, and the removal 

efficiency of wiping, washing, waxing or vacuuming. Studies of contamination on clothing or 

hair investigated deposition and clearance of particles. 

Deposition of particles on skin, hair or clothing was described in terms of a deposition 

velocity, defined as the flux density of particles toward the body surface divided by the 

concentration in air. The flux density of particles toward the body surface refers to the mass of 

particles that impact and are retained on the surface at a particular location and is given by the 

mass deposited and retained per unit area divided by the exposure time. Measured deposition 

velocities on skin under dry, windless conditions in a test chamber increased as the particle size 

was increased from 2.5 to 8 μm. Fogh et al. (1999) speculated that a cause of the lower 

deposition velocities of smaller particles was the greater effect of convective currents generated 

by body heat in deflecting those particles around the body surface. Reported deposition 

velocities on skin are discussed further in Section 4.4, and information on contamination of 

clothing obtained from that study is discussed in Section 5.2. 

13
Results of experiments by Fogh et al. (1999) probably cannot be used to assess doses 

from nuclear weapons fallout. Those studies were performed in dry indoor environments under 

conditions very different from those encountered at nuclear weapons testing sites. The 

experiments involved little or no air movement, a situation very different from that experienced 

in the field by military participants. Particle sizes used in those studies are smaller than the size 

of most fallout particles (i.e., less than 20 m, with one of the tracers attached to particles with a 

median diameter of 0.7 m). At those particle sizes, and given that there was no air movement 

and the volunteers were mostly stationary, deposition probably was increased by electrostatic 

forces, which should be less important at larger particle sizes.6

 

Another difficulty is the presentation of results of those experiments in terms of a 

deposition velocity. To use a deposition velocity in calculating dermal contamination, an 

estimate of an air concentration or time-integrated air concentration at the location of an exposed 

individual is needed. While measurements of air concentration may be common at nuclear 

facilities, estimates of dose to military participants rely on measurements of external exposure 

rates (R h–1) following deposition of fallout on the ground surface. An exposure rate would need 

to be converted to a concentration in air, e.g., by using an estimate of the deposition velocity that 

could have produced the activity concentration on the ground surface that resulted in the 

measured exposure rate. Such a procedure would involve significant uncertainties. In addition, 

both deposition velocities (on skin or on the ground) depend on particle size, so that application 

of those results to exposure to larger particles in nuclear fallout adds more uncertainty. These 

uncertainties would be larger than uncertainties associated with application of data from the 

volcanic ash studies, which directly relate the mass of material deposited on skin to the mass of 

material deposited on the ground. Thus, results of the volcanic ash studies with respect to 

deposition on skin or clothing are used directly in this report. 

Studies by Fogh et al. (1999) also provide information on the efficiency of removal of 

contamination from skin by wiping or washing. This information is discussed in 

Appendix D.2.2.6. 

 

6

 The importance of electrostatic forces in determining deposition of small particles on skin was indicated 

by measurements which showed that the deposition velocity on skin of the hand was lower if the hand 

was electrostatically grounded (Fogh et al. 1999; Table 4.3). 

14
2.2.4 Consideration of Effects of Particle Size

Particle size probably is the most important parameter that affects interception and 

retention on skin. In a theoretical part of their paper, Asset and Pury (1954) indicated that the 

larger the particle diameter, the larger the probability of inertial impaction. At the same particle 

diameter, the probability of inertial impaction also increased with increasing wind speed and 

particle density. Kochendorfer and Ulberg (1967) also noted an increase in the probability of 

inertial impaction with increasing particle size. They found that the probability that a particle 

will stick to skin for a significant length of time decreases as 1/d, where d is the particle 

diameter. This relationship applies at least for particles of diameter greater than 100 m. 

Kochendorfer and Ulberg (1967) pointed out a compensatory effect of particle size. 

Specifically, for particles of diameter greater than 10 μm, the larger the particle size, the larger 

the probability of impaction on skin but the lower the initial retention due to reduced adhesion.7 

According to those investigators, the dominant process is the decrease in initial retention with 

increasing particle size—i.e., when the effect of particle size on the probability of impaction is 

combined with the effect on adhesion, the overall result is a decrease in initial interception and 

retention with increasing particle size. Given that estimates of the skin contamination factor (ah) 

obtained in the volcanic ash studies apply to particle-size distributions that included particles of 

diameter up to 300 m with a median diameter of 50 to 80 m, it is possible that exposure to a 

distribution of particles weighted towards smaller sizes would result in a higher level of skin 

contamination and, thus, larger values of the skin contamination factor, because smaller particles 

adhere to skin better than larger particles. 

For very small particles (diameter less than 10 μm), the wind-tunnel studies by Asset and 

Pury (1954) and the indoor deposition studies by Fogh et al. (1999) seem to indicate that initial 

deposition and retention increases with increasing particle size. The authors of those studies 

suggested that very small particles have a low probability of impaction on the body surface due 

to their transport in air currents that flow around the body. This explanation is consistent with 

 

7

 A lower initial retention of larger airborne particles due to reduced adhesion is consistent with the 

reduced soil loading at larger particle sizes under conditions of direct contact of skin with soil reported by 

Driver et al. (1989) and discussed in Section 2.1. 

15
observations that very small particles that are inhaled can largely avoid obstacles and filters in 

the respiratory tract and are deposited mainly in regions of the deep lung (ICRP 1994). 

Studies summarized above indicate that interception and retention of airborne particles on 

skin may increase with increasing particle size up to about 10 μm, but is expected to decrease 

with increasing particle size at diameters greater than about 50 to 100 μm. Military personnel 

exposed to weapons fallout encountered particles with size distributions that were heavily 

weighted toward particles of diameter greater than 10 μm. Exposure to previously deposited 

fallout that was resuspended by winds involved particles of diameter about 100 μm or less 

(Sehmel 1984), with most resuspended fallout particles also larger than 10 μm. Thus, for 

exposure situations of concern to this report, interception and retention can be considered to 

decrease with increasing particle size, at least at diameters greater than about 50 to 100 μm. 

16
Table 2-1. Specific activity enrichment ratios from experiments 

with soils labeled with uranium (Sheppard and Evenden 1994) 

Soil typea 

Clay 

content 

(%) 

Enrichment ratiob 

(adhesion to hands) 

Clay 33 2.0 

Heavy loam 24 2.3 

Garden 18 1.2 

Medium loam 15 7.8 

Rich loam 13 2.4 

Carbonated loam 12 1.9 

Medium sand 6 2.7 

Fine sand 4 8.4 

Limed sand 3 9.9 

Acid sand 1 10.4 

Peat <1 2.9 

a Soils were dry and sieved through a course 5-mm mesh. Thus, 

particle diameters ranged over orders of magnitude. 

b Ratio of activity of uranium per unit mass in soil on skin to 

activity of uranium per unit mass in whole soil.

17
Table 2-2. Skin contamination factors (ah) obtained from studies of deposition of volcanic ash 

in CENIZA-ARENA experiments in Costa Rica (Miller 1966c) 

Individual / Sample description

Date / 

Exposure 

duration (h)

ma

(g ft–2)

wh 

a

 

(g)

ah = wh/ma

(cm2) 

Deposition on skin only 

WBL; inside ears, spray-wash 6-15 / 2.93 5.1 0.037 6.8 

CFM; inside ears, spray-wash 6-15 / 2.93 5.1 0.032 5.8 

CFM; inside ears, spray-wash 1-7 / 5.00 1.6 0.010 6.0 

CFM; forehead, spray-wash 6-16 / 2.47 13.8 0.11 7.5 

CFM; face, wash plus shave 8-11 / 7.10 15.1 0.040 2.5 

CFM; face; spray-wash 1-7 / 5.00 1.6 0.032 19 

CFM; forearms; spray-wash plus rubbing 10-6 / 7.00 1.1 0.16 135 

CFM; forearms and hands, spray-wash 1-7 / 5.00 1.6 0.11 66 

CFM; forearms and hands, spray-wash 1-7 / 0.92 0.16 0.029 172 

Deposition on hair and skin 

WBL; hair & face, spray-wash 1-7 / 4.00 1.20 0.24 190 

WBL; hair & face, spray-wash +dry combing 1-7 / 4.00 1.20 0.32 247 

Deposition on hairb

WBL; hair, spray-wash plus wet brushing 6-16 / 2.47 13.82 1.00 67 

WBL; hair, spray-washc 6-16 / 2.47 13.82 0.15 10 

WBL; hair, spray-wash plus brushing 6-15 / 2.93 5.14 1.20 216 

WBL; hair, spray-washc 6-15 / 2.93 5.14 0.99 179 

WBL; hair, dry brushing 12-9 / 0.67 0.042 0.0026 57 

WBL; hair, dry combing plus spray-wash 1-7 / 0.92 0.16 0.071 419 

WBL; hair, dry combingc 1-7 / 0.92 0.16 0.035 206 

WBL; hair, spray-wash 1-15 / 0.25 0.77 0.49 585 

JLJ; hair, spray-wash with combing 1-7 / 5.00 1.58 0.16 96 

CFM; hair, spray-wash plus wet brushing 6-16 / 2.47 13.82 0.71 48 

CFM; hair, spray-wash plus brushing 6-15 / 2.93 5.14 0.65 118 

CFM; hair, spray-washc 6-15 / 2.93 5.14 0.50 90 

CFM; hair, spray-wash 6-16 / 2.47 13.82 0.25 17 

CFM; hair, dry brushing 8-11 / 7.10 15.13 1.57 97 

CFM; hair, spray-wash with combing 1-7 / 5.00 1.58 0.24 143 

CFM, hair, spray-washc 1-7 / 0.92 0.16 0.11 620 

CFM, hair, spray-wash 1-15 / 0.25 0.77 0.33 393 

Deposition on clothing 

JLJ, blouse, spray-wash 1-7 / 2.67 0.80 0.33 385 

a m is mass of ash particles deposited per unit area of ground surface, and wh is mass of ash particles accumulated 

on sampled area of skin, hair or clothing. Skin contamination factor (ah) is given in units of cm2

 used in this report. 

b

 Hair cut: WBL, crew, male; CFM, medium, male; JLJ, medium, female. 

c

 Measurements with incomplete collection of material; data were not used in our analysis. 

18
Table 2-3. Experimental details and summary of estimates of efficiency of 

particle retention on skin obtained in wind-tunnel studies 

Efficiency of particle 

retentionb

Location (%) 

Exposure 

duration 

(min) 

No.of 

runs 

Particle 

sizea

 (μm)

Wind 

speed 

(mph) Average Range 

Asset and Pury (1954)c 

Effect of exposure duration

Hairy surface of forearm 10 7 6.5 5 0.58 1 zero; 

0.23–0.93 

Hairy surface of forearm 15 3 6.5 5 0.54 0.13–0.66 

Hairy surface of forearm 30 4 6.5 5 0.64 0.33–0.95 

Effect of hair 

Hairy surface of forearm 15 7 6.5 5 0.63 0.43–0.80 

Hairless surface of forearm 15 10 6.5 5 0.07 7 zeros; 

0.11–0.37 

Effect of wind speed and particle size 

Hairy surface of forearm 20 10 1.3d 5 0 none 

detected 

Hairy surface of forearm 20 11 6.5 2 0.17 6 zeros; 

0.18–0.65 

Hairy surface of forearm 20 8 6.5 5 0.9 0.39–1.9 

Landahl (1944)e 

Hairy surface of forearm 10 4.5 5.5 1.9 Not reported 

a

 Mass median diameter of distribution of particle sizes. 

b

 Ratio of mass of particles deposited per unit area of forearm to mass of particles that passed through unit 

area of plane perpendicular to direction of flow. 

c

 Unless otherwise noted, about 7% of mass was carried on particles of diameter greater than 10 m and 

maximum diameter was 20 m. 

d

 About 5% of mass was carried on particles of diameter greater than 2.6 m; maximum diameter was not 

reported. By assuming that particle-size distribution was lognormal with median of 1.3 m and 95th

percentile of 2.6 m, maximum particle size (taken to be close to 99.9th percentile) should have been 

about 5 m. 

e

 About 20% of mass was carried on particles of diameter greater than 10 m, and maximum diameter 

was 70 m. 

19
101

102

103

.1 1 5 10 50 90 95 99 99.9

WBL (GM = 182 cm2; GSD = 2.80)

CFM (GM = 163 cm2; GSD = 2.56)

All (GM = 164 cm2; GSD = 2.45)

a

h for hair [cm

2

]

Percent

WBL, male with crew cut; 

CFM, male with medium cut

Figure 2-1. Variability of contamination factor, ah, for hair obtained in studies of deposition of 

volcanic ash in CENIZA-ARENA experiments (Miller 1966b). 

20
3. MODELS TO ESTIMATE DOSES TO SKIN FROM 

DERMAL CONTAMINATION 

Models to estimate doses to skin from dermal contamination by radioactive material were 

developed on the basis of data obtained in the various studies summarized in Section 2. The 

general approach is described in Section 3.1. This approach is used to develop models for 

dermal contamination by descending fallout (Section 3.2), resuspension of old fallout 

(Section 3.3), and other activities (Section 3.4). The approach distinguishes between doses from 

exposure to a single radionuclide and exposure to a mixture of radionuclides in fallout. 

Contaminants retained on skin are removed by washing, but the removal process is only 

partially efficient. An approach to modeling the effect of inefficient washing on doses to skin 

from dermal contamination is described in Section 3.5. 

Models developed in this report are concerned primarily with estimating doses to skin 

from exposure to electrons emitted by radionuclides that are deposited and retained on skin or 

clothing. Emitted electrons of concern include continuous spectra of beta particles and internal 

conversion and Auger electrons of discrete energies. When mixtures of radionuclides in fallout 

from a nuclear weapon are deposited on skin or clothing, doses to skin from photons should be 

negligible compared with doses from electrons (Barss and Weitz 2006) and are not considered in 

this report. This report also considers doses from alpha-emitting radionuclides deposited on 

uncovered skin; the rationale for considering alpha doses to skin is discussed in Section 3.6. 

All parameters in models developed in this report are defined in this section. Values of 

each parameter are discussed in Section 4 for several types of exposure scenarios that are defined 

according to the source of contamination (i.e., fallout or resuspended material), duration of 

deposition onto skin (i.e., acute deposition, single continuous deposition, or chronic long-term 

and intermittent deposition), particle size, humidity conditions, and wind speed. 

3.1 Description of General Approach

The dose rate to radiosensitive tissues in the basal layer of skin from electrons or alpha 

particles emitted by radionuclides deposited on the body surface can be estimated as: 

21
  (3-1) skin DRFtCtD skin  

where 

 ) = dose rate to skin at time t (rem h–1 (tD ); 

 Cskin(t) = activity concentration of radionuclides on skin at time t (μCi cm–2); 

 DRFskin = dose-rate factor (dose rate per unit activity concentration of radionuclides 

deposited on skin) for electrons or alpha particles at assumed depth of 

radiosensitive tissues below the body surface (rem h–1 per μCi cm–2). 

In cases of exposure to descending fallout, skin is contaminated in a relatively short 

period of time. The activity concentration on skin reaches its maximum value at the end of the 

deposition event and then decreases over time by radioactive decay and other loss processes. For 

purposes of estimating dose from dermal contamination by descending fallout, the activity 

concentration on skin is assumed to reach its maximum value instantaneously. Equations that 

apply to an acute deposition of descending fallout are given in Section 3.2. 

In contrast to exposure to descending fallout, estimation of doses to skin from dermal 

contamination by resuspension of nuclear weapon debris is modeled as a continuous process. 

Resuspension can occur as a natural phenomenon (i.e., resuspension by winds) or as a result of 

such human activities as vehicular traffic (e.g., marching behind a vehicle), take-off or landing of 

helicopters, and walking through a contaminated area. Deposition of resuspended fallout onto 

skin can take place over many hours or days. In such cases, the activity concentration on skin is 

a function of time determined by the rate of deposition and the rate of loss of radioactive material 

on skin. Doses to skin from a single day’s deposition of resuspended material are calculated by 

integrating eq. (3-1), thus accounting for the dose during the period of resuspension and 

deposition on that day and the dose after deposition ceased (e.g., after leaving a contaminated 

area). Equations that apply to exposure to resuspended material are given in Section 3.3. Doses 

from many days of exposure to resuspended material can be estimated by summing doses 

received as a result of each day’s deposition onto skin. 

Skin contamination is reduced by washing. However, washing may not eliminate all 

contamination, especially smaller particles that become embedded in pores and creases of the 

skin. For example, Appendix D.2.2.4 discusses data on military participants for whom even a 

22
vigorous showering did not reduce skin contamination by a large amount and repeated showers 

and washing occurred in an effort to achieve decontamination. 

The modeling approach presented in Sections 3.2 to 3.4 provides estimates of dose from 

the time dermal contamination begins until the time of the first shower. In Section 3.5, a model 

is developed to estimate the additional dose received after the first shower from exposure to 

residual radioactive material that is not removed from skin by showering. 

3.2 Contamination of Skin from Exposure to Descending Fallout

In this report, contamination of skin by descending fallout is treated as an acute event that 

is assumed to occur essentially instantaneously. This assumption is equivalent to an assumption 

that the dose to skin during the period of deposition by descending fallout is negligible compared 

with the dose after deposition ceases. 

As indicated by eq. (3-1), dose rates to skin from deposition of descending fallout are 

proportional to the activity concentration of radionuclides on skin. The most common and 

reliable type of data obtained at locations where military personnel were exposed are 

measurements of external exposure rates (R h–1), from which activity concentrations of 

radionuclides on the ground surface (Ci m–2) are derived (Barrett et al. 1986). It is desirable to 

relate the activity concentration on skin to the derived activity concentration on the ground 

surface. In this study, we use an effective interception and retention fraction, ARf, which 

represents the fraction of the activity concentration deposited on the ground surface that is 

intercepted and retained on skin. Using this parameter, the dose rate to skin at time t is given by: 

    (3-2) skin skin gs f DRFARtCDRFtCtD skin  

where 

 Cgs(t) = activity concentration of radionuclides in fallout deposited on the ground 

surface (μCi cm–2); 

 ARf = effective interception and retention fraction (unitless). 

The CENIZA-ARENA volcanic ash studies described in Section 2.2.1 provide data that 

can be used to estimate an interception and retention fraction, r (unitless), which is defined as the 

23
ratio of the skin contamination factor ah (cm2

), for which data are summarized in Table 2-2, to 

the area of skin s (cm2) over which ah was measured: 





 



  s

a

r h (3-3) 

Data on the surface area of skin in different regions of the body are presented in Appendix A.2. 

The interception and retention fraction, r, represents the fraction of the mass of fallout particles 

deposited on the ground surface that is intercepted and retained on skin. 

In contrast to r, ARf is an effective interception and retention fraction that represents the 

fraction of the activity concentration of fallout deposited on the ground surface that is intercepted 

and retained on skin. As discussed in Section 2, interception and retention is affected by the 

amount of moisture on skin, the particle size, and the distribution of radionuclides on the surface 

or in the volume of fallout particles at the location of exposure. The effective interception and 

retention fraction, ARf, accounts for the fact that exposure conditions for military personnel 

could have differed from exposure conditions in the volcanic ash studies. This parameter is 

calculated by adjusting the interception and retention fraction, r = (ah/s), estimated from the 

volcanic ash studies for the effects of moisture, enrichment of specific activity, particle size, and 

the distribution of radionuclides on particles as:

AWEFEMPS

s

a AR a

h

f   

 



  (3-4) 

where 

 PSa = adjustment factor (unitless) to represent how retention on skin depends on 

particle size and to account for the difference between the particle-size 

distribution at a location of interest and the particle-size distribution for which a 

skin contamination factor (ah) was measured; 

 EM = adjustment factor (unitless) to account for an increase in retention efficiency 

with increasing moisture on skin; 

 EF = specific-activity enrichment factor (μCi g–1

skin per μCi g–1ground) to account for 

experimental evidence indicating that the specific activity of soil retained on 

24
skin is higher than the specific activity of soil on the ground when radionuclides 

are preferentially distributed on particle surfaces; 

 AW = activity-weight adjustment factor (unitless) to account for the difference 

between the activity and weight particle-size distributions in fallout. 

These adjustment factors are discussed in more detail in Section 4.2. 

The interception and retention fraction [r=(ah/s)] is derived mainly from data obtained in 

the volcanic ash studies. Data from the wind-tunnel experiments presented in Section 2.2.2 are 

used as complementary information. Experimental conditions in the wind-tunnel studies (small 

particles, dry conditions, constant and unidirectional winds, and exposure durations of 

30 minutes or less) differed from conditions in the volcanic ash studies (medium-to-large 

particles, humid conditions, variable wind speeds and directions, and exposure durations of 

hours). Thus, to apply an interception and retention fraction obtained from the wind-tunnel 

studies to military participants at atmospheric tests, values of parameters described above must 

be selected to adapt the conditions of those studies to the exposure conditions of military 

participants. When appropriate adjustments are made to data from the wind-tunnel studies, the 

interception and retention fractions obtained from the two studies are not inconsistent. 

3.2.1 Dose from Single Radionuclide

The dose delivered to skin during a time period Δt after an acute fallout event at time T0

can be estimated by integrating eq. (3-2). In the absence of showering or washing, the activity 

concentration on skin is reduced by radioactive decay and weathering (unintentional loss) of 

particles from skin. Radioactive decay is important for short-lived radionuclides and should be 

taken into account during the period after an acute deposition of fallout. Weathering can be 

important for large particles, which can fall from the skin or are easily removed by normal 

movement or light brushing. Weathering could occur during and after a deposition event. 

Weathering is much less important for small particles than for large particles (Fish et al. 1964). 

Small particles are lighter and thus are less affected by gravity, and they are harder to see on the 

skin, which reduces the chance of willful brushing or cleaning. Smaller, lighter particles also are 

more affected by electrostatic attraction than larger, heavier particles. Finally, very small 

particles can become embedded in skin imperfections and be very resilient even to washing. 

25
By assuming that all particles retained on skin are sufficiently small that they are not 

easily removed by weathering, which is equivalent to assuming that skin contamination factors, 

ah, measured in the volcanic ash studies include effects of weathering over a few hours, eq. (3-2) 

can be integrated to account only for radioactive decay after a deposition event. For a single 

radionuclide, the dose to skin (rem) during the period Δt in hours after an acute fallout event is: 

 

R

t

fgs skin

tT

T

λ Tt R

R e DRFARCteDtD

λ

1 )( d

Δ

0

0

0

λ

0

0

        (3-5) 

where 

 T0 = time after detonation when deposition of fallout occurs (h), 

 = dose rate to skin at time T0 (rem h–1

0 ), 

D

 = activity concentration of radionuclide on the ground surface at time T0 0 Cgs

 (μCi cm–2) 

R = radionuclide decay constant (h–1). 

If the time Δt that contamination is retained on skin (e.g., before removal by showering) 

exceeds the radionuclide half-life by a factor of about six or more, the total dose is given by the 

initial dose rate divided by the radionuclide decay constant, independent of Δt. If the 

radionuclide half-life is long compared with Δt, the dose rate is approximately constant in time 

and the total dose is given by the initial dose rate multiplied by Δt. If the radionuclide has 

radioactive decay products, in-growth of all important progeny has to be taken into account using 

the Bateman equations. 

3.2.2 Dose from All Radionuclides Combined

The number of radionuclides in fallout is large, especially at times shortly after a 

detonation. The dose from all radionuclides combined can be obtained by calculating the dose 

from individual radionuclides using eq. (3-5) and summing the results. However, that approach 

can lead to intensive calculations. 

A more practical approach to estimating dose when many radionuclides are present in 

fallout is to use the empirical relationship that the activity concentration of all radionuclides 

26
combined decreases with time after detonation as t

–x

, where the exponent x in the power function 

often is about 1.2 at times shortly after detonation (Glasstone and Dolan 1977; Turner 1995). 

This relationship can be used to estimate doses from mixtures of radionuclides in fallout by 

applying equations given above, provided that the activity concentration represents the total 

activity concentration of all radionuclides combined. The specific-activity enrichment factor 

(EF), the dose-rate factor (DRF), and the activity-weight adjustment factor (AW) may be 

radionuclide-specific. However, as described in Section 4.2, values of these parameters can be 

specified that are representative of values for all radionuclides combined. 

Using the power function for the time-dependence of the total activity of all radionuclides 

in fallout described above, the dose to skin during time period Δt after an acute fallout event 

(assuming negligible weathering of deposited radioactive material from skin) is given by: 

 

1 )( d

1

0

1

0

0

0

0 0

0

0 

 

 

   

 x

tTT DRFARTCttTDtD

x x

f skin

x

gs

tT

T

xx (3-6) 

where 

 = total activity concentration of all radionuclides on the ground surface at time T0

after detonation (μCi cm–2). 

0 Cgs

The total activity concentration on the ground surface at the time of deposition T0 is 

estimated from measurements of exposure rate at various times after a detonation. Thus, if an 

activity concentration Cmeas is obtained from measurements at time tmeas, the total activity 

concentration on the ground surface at time T0 is estimated as: 

 (3-7) x x

gs meas meas TtCC   0

0

Equation (3-6) and other similar equations in this section could be written as a function of 

the concentration Cmeas at the time an exposure rate was measured. However, since exposure 

rates usually were measured at different times tmeas and measurement times usually were not the 

same as the time of deposition of fallout, we prefer to use the activity concentration on the 

ground surface at the time of deposition, T0, as an input to the model. Values of the effective 

interception and retention fraction (ARf) and dose-rate factor (DRF) must apply to all 

radionuclides combined. Discussions in Sections 4.1 to 4.6 focus on estimating values of the 

interception and retention fraction r = (ah/s), its adjustment factors indicated in eq. (3-4), and 

27
dose-rate factors that apply to all beta-emitting radionuclides in fallout combined. An example 

calculation for a single radionuclide is presented in Appendix E.1, and Appendix E.2 provides an 

example of a dose assessment that includes the combined effect of all beta-emitting 

radionuclides in fallout. 

3.3 Contamination of Skin from Exposure to Resuspended Material

Deposition of radioactive particles on skin can occur not only by deposition of 

descending fallout from a nuclear weapon detonation, but also by deposition of resuspended old 

fallout. In the latter scenario, a fraction of the old fallout is lofted into the air by various 

mechanisms, and subsequent deposition leads to dermal contamination. Resuspension can occur 

as a result of various human activities, such as walking, driving a vehicle, take-off or landing of a 

helicopter, and detonation of weapons in areas where old fallout exists. A natural cause of 

resuspension is the wind. 

Contamination of skin by descending fallout or by material resuspended by a nuclear 

detonation at a given location can be a short-term (acute) event. In contrast, resuspension by 

winds or some human activities can result in longer-term (continuous) contamination of skin 

over many hours or days. For example, military personnel who march behind vehicles can be 

exposed to material resuspended by the vehicles for as long as a maneuver lasts. Thus, modeling 

of contamination of skin by resuspension due to winds and certain human activities should 

reflect the continuous nature of deposition onto skin. 

Detonation of a nuclear weapon in an area of old fallout is a special case of resuspension 

by human activity over a large region extending from ground zero. Exposure to large particles in 

descending old fallout that is resuspended by a nuclear detonation can be modeled as an acute 

event, in a manner similar to exposure to descending fresh fallout. However, exposure to 

resuspended small particles with fall times to Earth as long as several hours should be modeled 

as a continuous process. 

Section 3.3.1 describes general properties of resuspended material. Section 3.3.2 presents 

an approach to estimating doses to skin due to resuspension of old fallout by such human 

activities as walking, driving a vehicle, or take-off or landing of a helicopter. Section 3.3.3 

28
describes resuspension by winds. Finally, Section 3.3.4 addresses resuspension by a nuclear 

weapon detonation in an area of old fallout. 

In most cases of exposure to resuspended material, our approach is based on a proposal 

by an analyst at Science Applications International Corporation (SAIC).8

 Given an activity 

concentration of radionuclides on the ground surface, we first estimate the activity concentration 

in air using a resuspension factor, which is defined as the ratio of the activity concentration in air 

to the activity concentration on the ground surface and normally is given in units of m–1. We 

then estimate the flux of resuspended material incident on the body per unit area. In cases of 

wind-driven resuspension, resuspended material is carried towards the body by winds. In most 

cases of resuspension by human activities (and in the absence of significant wind), resuspended 

material is intercepted by the body at a speed given by its deposition velocity or the velocity of 

an individual relative to surrounding air; the one exception discussed in Section 3.3.4 involves 

exposure of forward observers at NTS to larger particles in old fallout that was resuspended by a 

nuclear detonation. In all cases, interception and retention fractions, r, obtained from the 

CENIZA-ARENA volcanic ash studies augmented by information from wind-tunnel studies (see 

Section 2.2) are used to estimate the fraction of the activity of resuspended material incident on 

the body that is ultimately retained on skin. Values of the adjustment factors that are applied to r

[see eq. (3-4)] are chosen to represent the characteristics of resuspended material. 

3.3.1 General Properties of Resuspended Material

Resuspension of material from the ground surface is influenced by many factors, such as 

particle size, material properties, topographical conditions, and meteorological conditions 

(Sehmel 1984). For instance, if soil is saturated with moisture, little or no wind-driven 

resuspension occurs. If soil is dry and the right meteorological conditions occur, dust devils can 

loft more particles than normally expected by wind-driven resuspension. The effect of these 

factors is acknowledged in the literature but has not yet been quantified in great detail. 

An important factor in predicting doses from dermal contamination is the particle-size 

distribution of resuspended material, because interception and retention on skin and clothing 

 

8 Personal communication from J. Klemm, SAIC, McLean, Virginia (2004).

29
depends on particle size. Fallout at locations tens to hundred of miles from ground zero of a 

nuclear test contains mostly small particles with diameters of 100 m or less (Glasstone and 

Dolan 1977; Sehmel and Hodgson 1976). Resuspension of this material will generate airborne 

particles with diameters less than 100 m. At locations within a few miles of ground zero, 

diameters of fallout particles may range from a few to hundreds of μm (Miller 1969). However, 

under certain conditions (e.g., resuspension by winds or by such human activities as normal 

walking), resuspended fallout at locations close to ground zero will contain mostly smaller 

particles and, thus, a greater fraction of small particles than fallout on the ground surface. 

Lee and Tamura (1981), citing Healy (1974) and Chepil (1945), state that resuspendable 

particles generally have diameters less than 100 m. This should be the case for wind-driven 

resuspension under normal conditions (e.g., wind speeds less than 10 m s–1, or 22 mph) (Garger 

et al. 1997a). However, very strong winds, blast waves from nuclear detonations, dust devils, or 

similar vigorous air movements can resuspend particles with diameters greater than 100 m. 

Sehmel (1984) showed that larger soil particles can be broken into smaller, respirable 

particles (< 10 m) when subjected to the right amount of force. For example, to the extent that 

fallout particles are similar to soil particles, vehicular traffic could break larger particles into 

smaller ones before they are lofted into the air. However, even when large fallout particles are 

thrown into the air by vehicles without breakage, they probably would be lofted only to modest 

heights (perhaps a few meters or less) and would fall rapidly to the ground. Thus, at locations 

close to ground zero of a nuclear detonation (e.g., at NTS), it is expected that radioactive 

material resuspended by moving vehicles that could deposit on skin of nearby individuals 

contained mostly smaller particles compared with the size distribution of fallout particles.9

 

The blast wave produced in a nuclear detonation can create overpressures of many 

pounds per square inch at ground level over distances of thousands of feet from ground zero 

(Glasstone and Dolan 1977). Strong winds associated with a blast wave, which can be hundreds 

of miles per hour (Glasstone and Dolan 1977), and the thermal pulse at locations closest to 

ground zero presumably could loft even the largest radioactive particles. Two exposure 

situations can be distinguished in cases of resuspension by a nuclear detonation (Kocher et al. 

 

9 Another factor that limited resuspension of larger particles by vehicles at NTS was speed limits that 

were imposed on vehicular traffic to reduce resuspension. 

30
2009). The first situation involves exposure to large particles that were redeposited on the 

ground within minutes after a detonation. Only forward observers who were located close to 

ground zero at the time of a detonation would be exposed to large particles in resuspended old 

fallout. A second situation involves exposure to small particles in resuspended old fallout that 

may have remained airborne for as much as a few hours after a detonation. Maneuver troops 

who entered an area impacted by a detonation after large particles had redeposited or forward 

observers who remained in that area for some time could have been exposed to small particles in 

those lingering dust clouds. 

Thus, at NTS, individuals who encountered material that was resuspended by slow to 

moderate winds or slow moving vehicles or who encountered dust clouds that lingered after a 

nuclear detonation probably were exposed to particles with diameters that tended to be smaller 

than the diameters of fallout particles on the ground surface. Sizes of most resuspended particles 

should be less than 100 m in such cases. Forward observers at locations close to ground zero 

during a test or other participants who were located in areas of strong winds (e.g., at locations of 

helicopter take-off or landing) presumably were exposed to resuspended particles with sizes from 

a few microns to hundreds of microns. 

The amount of radioactive material on the ground surface that can be resuspended 

decreases with time due to leaching of soluble radionuclides, runoff, downward migration of 

particles, and other loss processes (Garger et al. 1997b). Consequently, resuspension may be less 

efficient a few years after an initial deposition of fallout than immediately after deposition. 

Exposure scenarios discussed in this report involve resuspension events that occurred at times 

from shortly after deposition (e.g., marching through a fresh fallout field) to as much as a few 

months or years (e.g., exposure to old fallout on a residence island in the Pacific). 

3.3.2 Resuspension by Human Activities

This section discusses an approach to estimating doses to skin from dermal contamination 

due to resuspension of nuclear weapon debris by such human activities as vehicular traffic (e.g., 

marching behind a vehicle), take-off or landing of helicopters, or walking through a 

contaminated area. In contrast to descending fallout, which is modeled as an acute event, this 

31
approach takes into account that deposition of resuspended fallout onto skin on a given day may 

take place over many hours, in which case resuspension and deposition should be modeled as a 

continuous process. Furthermore, in some exposure scenarios for military participants (e.g., 

exposure on a residence island in the Pacific), contamination of skin due to resuspension of 

fallout by human activities may have occurred each day over a period of weeks or months. 

If human activities of interest are performed in an area that is contaminated at an average 

concentration (Cgs; μCi m–2

ground), a resuspension factor (RF; m–1) can be used to derive an 

average air concentration AA (μCi m–3) = Cgs × RF. An individual located in that area is 

subjected to a flux density of airborne particles given by AA × VD (μCi m–2 s–1), where VD is a 

velocity (m s–1), either the deposition velocity of particles or the speed that an individual moves 

relative to the surrounding air.10 Of all airborne particles that impact the body, only a fraction 

will be retained on skin. This fraction is described by an interception and retention fraction, r, 

similar to that developed for descending fallout. 

As in the model for an acute deposition onto skin by a fallout event described in 

Section 3.2, contamination of skin by deposition of resuspended material is assumed to start at 

time T0 after a detonation. In resuspension scenarios, the time T0 often is not the same as the 

time after detonation when fallout was deposited on the ground. Deposition then continues for a 

period Tdep and ceases at time Tdep. After deposition ceases, skin is assumed to remain 

contaminated for a post-deposition period Tpost until decontamination occurs (most likely by 

showering). Skin thus is assumed to be irradiated continuously over a period Tex = Tdep + 

Tpost, during which the dose rate can vary with time. 

While showering, a fraction of the radioactive material deposited on skin is removed by 

washing and exfoliation of skin cells. After showering, the activity of material remaining on 

skin continues to be reduced by radioactive decay. In this section, we account only for doses to 

skin that are received up to the time of the first shower. Doses from contamination that remains 

on skin after the first and any subsequent showers are taken into account using a model described 

 

10 The units of length (m) and time (s) in these formulations are based on the considerations that 

resuspension factors generally are given in m–1 and that deposition velocities would be given in m s–1 in a 

compatible system of units. 

32
in Section 3.5, and recommended values of parameters to be used in implementing the model for 

inefficient showering are provided in Sections 4.7.1 and 4.7.2. 

Models developed in the following two sections to estimate doses received during the 

period of a continuous deposition onto skin and after deposition ceases to the time of the first 

shower represent doses from a single day’s exposure to resuspended material. Doses from 

multiple days of exposure to resuspended material are obtained by summing the doses from each 

day’s exposure. All parameters in the models to estimate doses from resuspended material are 

discussed in Section 4 except the duration of exposure characterized by Tdep and Tpost, which 

are specified by the analyst according to a defined exposure scenario. 

3.3.2.1 Dose from Single Radionuclide 

In cases of continuous resuspension and deposition onto skin, the rate of change of the 

activity concentration of a single radionuclide on skin, Cskin (μCi cm–2), at time t is given by the 

rate at which the concentration on skin increases due to deposition minus the rate at which the 

concentration decreases due to radioactive decay, assuming no other losses from skin: 

      0

0 λ )( 36.0 λ ,)( d

d 0 ARVRFeC TttC

t

tC

fD R skin

Tt

gs

skin R    (3-8) 

where 

 = activity concentration of radionuclide on ground surface at time T0 (μCi m–2); 0 Cgs

R = radioactive decay constant (h–1); 

 RF = resuspension factor (m–1); 

 VD = deposition velocity of particles onto skin (m s–1); 

 ARf = effective interception and retention fraction (unitless); and 

 t = time after detonation (h). 

The constant 0.36 is a units conversion factor that includes a conversion of the units of 

deposition velocity to m h–1 to be consistent with the units of time (h) and the radioactive decay 

constant (h–1) and a conversion of the unit of area on the ground surface in m2

 to the unit of area 

on skin in cm2

 to give an activity concentration on skin, Cskin, in μCi cm–2. 

33
The model in eq. (3-8) is based on the following assumptions: (1) the activity 

concentration of radionuclides in fallout that is intercepted and retained on skin is a function of 

the activity concentration on the ground surface, which decreases with time only by radioactive 

decay (i.e., no significant loss of radionuclides from the ground surface occurs by leaching or 

other processes during the exposure period); (2) the resuspension factor is constant during the 

time deposition onto skin occurs; (3) deposition onto skin occurs at a sufficiently low rate that 

the concentration of fallout particles on skin does not saturate during the deposition period; and 

(4) the effect of weathering of radioactive material from skin is incorporated in values of the 

interception and retention fraction r, which are based on measured accumulations on skin in the 

volcanic ash studies under conditions of chronic deposition over several hours (Section 2.2.1), 

and, thus, the rate of reduction of the activity concentration of radionuclides on skin is 

determined by the radioactive decay constant. 

Equation (3-8) can be solved by using the initial condition that Cskin = 0 at the beginning 

of a deposition onto skin at time t = T0. The result is: 

   

0

λ

0

0 36.0)( , 0 TteTtARVRFCtC Tt

skin gs fD R    (3-9) 

The dose rate (rem h–1) during the period of deposition then is given by: 

  (3-10)     0

λ

0

0 36.0)( , 0 tD eTtARVRFC skin TtDRF Tt

gs fD R    

The total dose (rem) during the period of deposition onto skin (Tdep), denoted by Ddep, is: 

   

2

Δλ

0

λ

11 Δλ e

36.0

d)( 0

R

T

depR

gs fD skin

T

T dep

depR

dep

T

DRFARVRFC

D ttD





 

 

 (3-11) 

After deposition ceases, radionuclides are assumed to remain on skin until the first 

shower, except for removal by radioactive decay, for an additional period Tpost. By using 

eqs. (3-9) and (3-10), the dose rate at time t after deposition ceases is given by: 

  (3-12)  

skin dep

T Tt

gs depfD eeTARVRFCtD TtDRF depR depR      

0.36)( Δ , 0 Δλ λ

The dose delivered to skin during the post-deposition period, denoted by Dpost, then is: 

34
  skin

R

T

T

post gs fD dep DRF e D eTARVRFC

postR

depR   





λ

1 0.36 Δ

Δλ

0 Δλ (3-13) 

Again, the activity concentration of radionuclides on the ground surface, , in these equations 

is assumed to be given in units of μCi m–2, the resuspension factor, RF, in m–1, the deposition 

velocity, VD, in m s–1, all times in h, the radioactive decay constant, λR, in h–1, and the dose-rate 

factor, DRFskin, in rem h–1 per μCi cm–2; the constant 0.36 is a units conversion factor. 

0 Cgs

The total dose (before showering) is the sum of the dose during the period of deposition 

on skin (Ddep) given by eq. (3-11) and the dose after deposition on skin ceased (Dpost) given by 

eq. (3-13). The dose Dpost is very small if showering occurs immediately after deposition ceases. 

For exposure to a single radionuclide, doses Ddep and Dpost depend on differences in time Tdep

and Tpost, but do not depend on T0 for given values of Tdep and Tpost. The total dose (before 

showering) can be increased as described in Section 3.5 to account for the dose received after the 

first and subsequent showers if showering does not remove all radioactive material on skin. 

The equations given above apply to radionuclides for which radioactive decay is 

important during the period of exposure to resuspended material (about 24 hours or less for 

exposure on a single day). Such radionuclides are present in the environment only at times 

shortly after an initial deposition of fallout. 

For long-lived radionuclides (T1/2 >> 24 h), the equations given above can be applied by 

setting R to zero. Thus, for long-lived radionuclides, the activity concentration on skin at time t

during a deposition event is: 

  0 0

0

skin 36.0)( gs fD ,  TtTtARVRFCtC (3-14) 

and the total dose during the deposition event is: 

 

2

Δ

36.0

2

0 dep

dep gs fD skin

T

D DRFARVRFC  (3-15) 

The dose delivered by a long-lived radionuclide after deposition ceases is the product of the dose 

rate at the time deposition ceases and the post-deposition exposure time: 

 (3-16) Dpost gs depfD post DRFTTARVRFC skin 36.0( ) Δ  0

35
Again, the total dose (before showering) is the sum of the doses in eqs. (3-15) and (3-16), and 

this dose can be increased to account for the inefficiency of showering in removing radioactive 

material from skin using a model described in Section 3.5. 

3.3.2.2 Dose from All Radionuclides Combined

In modeling the dose from exposure to a mixture of radionuclides in fallout in a 

resuspension scenario, we again assume, as in the model for descending fallout in Section 3.2.2, 

that the total activity concentration decreases with time as t

–x

. The rate of change of the total 

activity concentration on the ground surface or on skin due only to radioactive decay then can be 

expressed as dC/dt ~ –xt

–1C. 

The rate of change of the activity concentration on skin again is given by the rate of 

increase due to deposition onto skin minus the rate of decrease due to radioactive decay, 

assuming no other losses from skin. However, in contrast to the case of a single radionuclide, for 

which the radioactive decay constant R is time-invariant, the fractional rate of change in activity 

concentration varies with time as xt

–1. Thus, during the period Tdep when deposition onto skin 

occurs, the rate of change of the activity concentration on skin is: 

    fD skin dep

xx

gs

skin TtTtCtxARVRFtTC

t

tC    

0

1

0

0 36.0 ,)( d

)(d (3-17) 

where is the total activity concentration of all radionuclides on the ground (μCi m–2) at time 

T0 after a detonation, which can be estimated as indicated in eq. (3-7). Except for the effect of 

radioactive decay, this model incorporates the same assumptions as the model for the dose from 

a single radionuclide in eq. (3-8). 

0 Cgs

By again assuming that the activity concentration on skin at the beginning of the 

deposition event is zero [Cskin(t=T0) = 0], eq. (3-17) can be solved to obtain the activity 

concentration on skin (μCi cm–2) at any time t during deposition of resuspended material: 

    dep

x x

fD

x

skin gs  TtTTttARVRFTCtC  0 0

)1(

0

0 36.0 , (3-18) 

The dose to skin during the period of deposition (Tdep) is given by: 

36
   

 )2(

0

)1(

0

0 )2(

0

0

)1(

0

0

)2()1( )2()1(

36.0

36.0d)( d 0 0

 



  

 

 

   

x x

dep

x

dep

fD skin

x

gs

T

T skin

x x

fD

x

gs

T

T dep

Tx TTTx

xx

DRFARVRFTC

D ttD tDRFTttARVRFTC dep dep

 (3-19) 

After deposition ceases, the activity concentration on skin decreases as t

–x

: 

  x

skin tKtC

  (3-20) 

where K is a constant. Since the activity concentration on skin must be a continuous function of 

time, the concentration at the time deposition ceases obtained from eq. (3-18) is the same as the 

concentration at that time obtained from eq. (3-20): 

    x

dep

x x

fD

x TC depskin gs dep dep TKTTTARVRFTC   

0  )1(0

0 36.0 (3-21) 

Solving for the constant K gives: 

  0 0

0 36.0 depfD TTARVRFTCK x

gs   (3-22) 

Thus, the activity concentration on skin at any time t after deposition ceases is given by: 

    dep

x

depfD

x

skin gs  TttTTARVRFTCtC   36.0 , 0 0

0 (3-23) 

After deposition ceases, skin is irradiated continuously to time Tex = Tdep + Tpost. During 

the post-deposition period Tpost, the dose to skin is given by: 

 (3-24)    ex

dep

T

T skin

x

post D dtDRFtK

Using the expression for the constant K in eq. (3-22), the result is: 

  dep ex

x x

dep dep

fD skin

x

gs

post

TtTTTTT

x

DRFARVRFTC

D

 

 

 

 



)( ,

)1(

36.0

)1(

ex

)1(

0

0

0

 (3-25) 

As noted previously, Dpost is very small if showering occurs immediately after deposition onto 

skin ceases. 

The dose from the time deposition ceases to the time of the first shower in eq. (3-25) also 

can be expressed in terms of the activity concentration of radionuclides on skin at the time 

37
deposition ceases, Cskin(Tdep). Using eq. (3-23) at time Tdep, the dose during the post-deposition 

period becomes: 

   

  dep ex

x

ex

x

dep

skin

x

post depskin dep TtT

TT

DRFTTCD  

  



 , 1x

)1()1(

 (3-26) 

Equation (3-26) is similar to eq. (3-6), which gives the dose due to an acute deposition from the 

time of contamination to the time of the first shower. In the case of a chronic deposition that 

ceases at time Tdep, the dose from time Tdep to the time of the first shower (Dpost) is the same as 

the dose during the same period from an acute deposition at time Tdep that results in an activity 

concentration on skin equal to the concentration at the time the chronic deposition ceases. 

The total dose delivered before the time of the first shower is the sum of the dose during 

deposition [Ddep, eq. (3-19)] and the dose after deposition ceases [Dpost, eq. (3-25)]: 

    )2(

0

)1(

0

)2(

0

0

)2(

)2)(1(

36.0

 





 

 

x x

dep ex

x

dep

fD skin

x

gs

T TTTTx

xx

DRFARVRFTC

D (3-27) 

Equation (3-27) was derived using a differential-equation approach. As shown in Appendix B, 

the same result can be derived using an integral-equation approach. In contrast to the case of 

exposure to a single radionuclide, doses Ddep and Dpost depend on the time after detonation, T0, 

for any period of deposition onto skin (ΔTdep) and post-deposition period (ΔTpost). 

When showering does not remove all contamination from skin, an additional dose is 

delivered after the first and subsequent showers. This additional dose is estimated using a model 

described in Section 3.5. 

The total dose in eq. (3-27) is the dose from deposition of resuspended material onto skin 

during a single day. The dose from multiple days of exposure to resuspended material is 

obtained by summing the doses from each day’s exposure. In Section 3.5, we show how this 

summation can be performed while accounting for inefficient showering. 

38
3.3.3 Wind-Driven Resuspension

Estimation of downwind airborne concentrations of material resuspended from the 

ground surface by winds is difficult and generally must rely on a resuspension rate, rather than a 

resuspension factor (Sehmel 1984). However, if an individual is located in a sufficiently large 

area that is contaminated at nearly constant levels, a resuspension factor can be used to estimate 

doses to skin from dermal contamination. 

A resuspension factor can be used to derive an average activity concentration in air AA

(μCi m–3) due to wind-driven resuspension. When the source is large and uniformly 

contaminated, the concentration in air is essentially constant over a large area. If an individual is 

standing on the ground and air is moving toward him with a wind speed VW (m s–1), the 

individual is subjected to a flux density of particles AA × VW (μCi m–2 s–1). This flux density is 

analogous to a deposition rate per unit area onto a horizontal surface, with the deposition velocity 

replaced by the wind speed. 

On the basis of the analogy between a deposition velocity and wind speed, equations 

developed in Section 3.3.2 can be applied to wind-driven resuspension by replacing the 

deposition velocity VD by the wind speed VW. As in modeling deposition of airborne material 

that was resuspended by human activities, wind-driven resuspension results in a continuous 

deposition onto skin during the time an individual is outdoors in an area open to winds. All 

assumptions described following eq. (3-8) (Section 3.3.2.1) are assumed to apply to wind-driven 

resuspension. The relevant equations to estimate dose from deposition onto skin during a single 

day’s exposure to resuspended material are reiterated as follows: 

 Dose from single radionuclide during period of deposition onto skin – eq. (3-11); 

 Dose from single radionuclide during period from time deposition onto skin ceases to 

time of first shower – eq. (3-13); 

 Dose from all radionuclides in fallout combined during period of deposition onto 

skin – eq. (3-19); 

 Dose from all radionuclides in fallout combined during period from time deposition 

onto skin ceases to time of first shower – eq. (3-25) or (3-26); 

39
 Total dose from all radionuclides in fallout combined from time deposition onto skin 

begins to time of first shower – eq. (3-27). 

Again, the dose from multiple days of exposure to resuspended material is obtained by summing 

the doses from each day’s exposure. 

In some scenarios involving wind-driven resuspension (e.g., exposure of military 

personnel on residence islands in the Pacific), deposition onto skin occurred over a period of 

weeks or months. During such long exposures, the resuspension factor (RF) often is assumed to 

decrease with time after an initial deposition on the ground surface. In Section 3.5.4, where the 

effect of inefficient showering on doses to skin in cases of multiple days of deposition onto skin 

is discussed, we show how a time-dependence of the resuspension factor can be taken into 

account in estimating the dose from multiple days of exposure. 

In some cases of exposure to fallout that was resuspended by winds (e.g., on residence 

islands in the Pacific), radionuclide concentrations on the ground surface at times of exposure 

may have resulted from two or more previous depositions of fallout that occurred at different 

times. If two or more previous fallout depositions contribute significantly to the total activity 

concentration of radionuclides on the ground at the time exposure to resuspended material 

occurred, doses to skin should be calculated by applying the model equations to each of the 

previous fallout depositions separately and adding the doses to skin from each deposition. It 

would not be correct to apply the model equations to the total activity concentration of 

radionuclides on the ground at the time exposure begins, essentially because the time T0 after 

detonation when exposure begins would be different for each contributing fallout deposition. 

Although Sections 3.3.2 and 3.3.3 discuss resuspension by human activities and by winds 

separately, this distinction is largely artificial. As indicated by model equations in the two cases, 

deposition onto skin during a given period of exposure is proportional to a deposition velocity, 

without regard for whether deposition occurs as a result of gravitational settling, in which case 

the deposition velocity is denoted by VD, impaction due to winds, in which case the deposition 

velocity is the same as the wind speed, VW, or any combination of processes. In any 

resuspension scenario, the required quantity is an estimate of the flux density of material 

impacting the body surface (i.e., amount of material deposited and retained per unit area per unit 

time) divided by the concentration in air. 

40
3.3.4 Resuspension by Nuclear Detonations

Resuspension of old fallout by the thermal pulse or blast wave produced in a nuclear 

weapon detonation (Kocher et al. 2009) is an acute event. In estimating doses from dermal 

contamination due to redeposition of resuspended material, the particle-size distribution of 

activity in old fallout that was resuspended by a nuclear detonation is assumed to be the same as 

the particle-size distribution of activity in old fallout on the ground surface. A distinction then is 

made between redeposition of larger particles of diameter greater than about 100 μm, which 

should occur within a few tens of minutes in the thermal-pulse region closest to ground zero and 

within a few minutes in the blast-wave region beyond the thermal-pulse region, and redeposition 

of smaller particles, which could occur over a period of several hours in the thermal-pulse region 

and a few hours in the blast-wave region (Kocher et al. 2009). Only forward observers who were 

located in the blast-wave region at the time of a detonation would be contaminated by 

redeposition of larger particles, whereas both forward observers and maneuver troops who 

entered the blast-wave or thermal-pulse region at some time after a detonation would be 

contaminated by redeposition of smaller particles. Contamination due to redeposition of larger 

particles should not occur in the thermal-pulse region, given that maneuver troops would not 

have entered that region until some time after larger particles were redeposited. 

We first consider contamination of forward observers due to redeposition of larger 

particles that were resuspended by the blast wave in a nuclear detonation. As noted above, this 

exposure occurred within a few minutes. Data reviewed by Kocher et al. (2009) indicate that 

larger particles in old fallout at NTS carried more than 90% of the resuspended activity; the 

median estimate of this fraction is 99%. Therefore, in estimating contamination of forward 

observers due to redeposition of larger particles, it is a good approximation to assume that larger 

particles carried essentially all the activity of resuspended material. Under that condition, doses 

to skin of forward observers due to exposure to larger particles in old fallout that was 

resuspended by the blast wave can be estimated in a manner similar to doses due to descending 

fallout, and the dose rate at the time of detonation (t) can be estimated as: 

  (3-28) gsR f DRFARtCftD skin  

)(

41
This equation is the same as eq. (3-2) except it contains an additional parameter (fR; unitless), 

which is the fraction of the activity in old fallout on the ground surface that is resuspended by a 

detonation and redeposited on the ground surface at essentially the same time. In eq. (3-28), the 

activity concentration on the ground surface, Cgs, is the concentration of old fallout at the time of 

a detonation, not the concentration of any fallout from that detonation that might occur in the 

same area, and the effective interception and retention fraction, ARf, is a value that applies to 

larger particles with a median diameter greater than about 100 μm. 

In applying eq. (3-28) to contamination of forward observers due to redeposition of larger 

particles, the fraction of the activity of radionuclides on the ground surface that is resuspended 

by the blast wave (fR) can be estimated using a resuspension factor, RF: 

gs

air

C

C RF  (3-29) 

When resuspended radionuclides are redeposited onto the ground, they produce an activity per 

unit area (CR) on the ground surface. If resuspended radionuclides are assumed to be uniformly 

distributed in a layer of air of height H above ground, the following relationships are obtained: 

  R air gs Rgs       fCHRFCHCC (3-30) 

HRFf R   (3-31) 

Thus, the parameter fR in eq. (3-28) is estimated as the product of the resuspension factor that 

applies to all old fallout on the ground surface and the height of the cloud of resuspended 

material in the blast-wave region. 

During an assumed period of exposure after larger particles are redeposited, when only 

smaller particles would remain in air, dermal contamination of forward observers or maneuver 

troops in the blast-wave or thermal-pulse regions can be estimated using the equations that apply 

to resuspension by human activities in Section 3.3.2 and an assumed deposition velocity, VD (or 

wind speed, VW). The resuspension factor (RF) for smaller particles in resuspended fallout is the 

product of the resuspension factor that applies to the entire amount of old fallout [i.e., the value 

used to obtain the parameter fR in eq. (3-31) to estimate contamination of forward observers due 

to redeposition of larger particles in the blast-wave region or a higher value in the thermal-pulse 

region] and an assumed fraction of the activity in old fallout that was carried by smaller particles. 

42
In applying equations in Section 3.3.2, the effective interception and retention fraction, ARf, is a 

value that applies to smaller particles with a median diameter less than about 100 μm. 

An additional parameter that could be included in eq. (3-28) and in the model that uses a 

deposition velocity to estimate contamination due to redeposition of smaller particles is a 

dispersion factor, fD. This parameter would take into account that old fallout that was 

resuspended by a nuclear detonation may be spread over a larger area around ground zero, due to 

the outward-directed winds associated with a blast wave (Glasstone and Dolan 1977), than the 

area of old fallout prior to resuspension. This dispersion would result in a dilution of the 

concentration in air that is estimated using a resuspension factor. The dispersion factor, fD, can 

be estimated by assuming that a detonation resuspended material over the area of a circle of 

radius R1 and dispersed that material over the area of a circle of larger radius R2. For example, if 

the initial concentration of radionuclides on the ground is essentially uniform and resuspended 

material is assumed to be dispersed uniformly by a detonation, the dispersion factor is given by 

the ratio of the areas of the two circles. This dispersion factor accounts for horizontal dispersion 

of resuspended material. Vertical dispersion also occurs and is taken into account in the 

parameter fR, which is calculated using eq. (3-31). 

We expect that the dispersion factor, fD, generally should be small, i.e., less than a factor 

of two. A dispersion factor of two would mean that the radius of the cloud of resuspended 

material would be about 40% larger than the radius of the source region. Such a large increase 

seems extreme, especially at the outer boundary of the blast-wave region. Given that the 

uncertainty in a resuspension factor in the thermal-pulse and blast-wave regions is much larger 

than any credible value of the dispersion factor, we believe that it would be reasonable to ignore 

this parameter in most dose reconstructions for forward observers or maneuver troops. 

3.4 Contamination of Skin from Other Activities 

Accumulation of soil particles on skin also can occur as result of direct contact with soil 

or contaminated equipment while performing various activities. Studies of levels of 

accumulation of soil on skin while performing various common activities are summarized in 

Appendix A, Tables A-1 and A-2, and measured accumulations of soil on skin and clothing of 

troops while crawling under simulated combat conditions are summarized in Appendix A, 

43
Tables A-3 and A-4. As discussed in Section 2.1, more accumulation occurs in regions of the 

body where soil touches the skin, and accumulation is increased by the presence of moisture. 

Sheppard and Evenden (1994) observed soil loadings on skin from direct contact with 

soil of 2 to 6 mgsoil per cm2

skin when soil was moist. At soil loadings of 2 mgsoil per cm2skin or 

more, dirt is visible on skin, and it is likely that cleaning will take place sooner than when dirt is 

not easily visible. For all activities listed in Tables A-1 and A-2 except children playing in mud, 

the dermal soil loading was less than 1 mgsoil per cm2

skin. The largest accumulations of soil 

occurred on the skin of gardeners, farmers, and earth-scraping machine operators, all of whom 

perform operations that involve moving or handling dirt. 

Some military personnel performed similar activities, such as digging trenches, and other 

activities as well (e.g., handling contaminated equipment). To estimate doses to skin from 

dermal contamination during these activities, care should be taken in accounting for the type of 

activity, especially in assessing whether soil that was handled was contaminated. For example, 

digging a trench in a fallout field involved lots of dirt moving, but most of the dirt that was 

located well below the ground surface was uncontaminated. 

Once a soil loading on skin is estimated, the activity concentration of radionuclides on 

skin can be calculated using an estimate of the specific activity (μCi g–1) of the accumulated 

material. Doses to skin then can be calculated using dose-rate factors for all radionuclides in 

fallout combined discussed in Section 4.6 or dose-rate factors for individual radionuclides, such 

as those reported by Kocher and Eckerman (1987). 

Another potential exposure pathway is dermal contamination by transfer of radioactive 

particles due to contact with a contaminated surface (contact transfer). This pathway is 

potentially important, for example, for military personnel who maintained, repaired or 

decontaminated aircraft or ships. Contact transfer results in direct contamination of hands and 

perhaps other regions of the body (e.g., forearms, shoulders, legs). Contact transfer also can 

result in indirect contamination by transfer of radioactive material from hands to other regions of 

the body (e.g., contamination of the face when touched by a contaminated hand). 

Contact transfer was studied by Fogh et al. (1999) using surfaces that were uniformly 

contaminated with stable tracers that can be activated by neutrons. Tracers were attached to 

small particles with median diameters of 5 or 10 μm, and surfaces were touched by a gloved 

44
hand for 30 seconds. Gloves made of textured latex, which was considered to be a good 

representation of the surface of human skin, were used to eliminate concerns about uncertainties 

in the efficiency of recovery of particles from bare skin. Dry gloves picked up about 20% of the 

particles of either diameter (standard deviation about 11%) from such surfaces as cotton, paper, 

wood, or plastic. The efficiency of contact transfer increased to about 30% (standard deviation 

about 16%) when damp gloves were used. 

In another study, Brouwer et al. (1999) estimated a contact transfer efficiency of less than 

2% for fluorescent-dyed particles on surfaces with relatively low loadings of 10 to 200 μg cm–2. 

The average loading on skin in that study thus was on the order of 1 μg cm–2. 

The types of studies described above could be useful in estimating dermal contamination 

of hands and other body surfaces by direct contact if a reasonable estimate of the activity 

concentration on a contaminated surface or object can be obtained. If an activity concentration 

on skin is estimated using such contact transfer efficiencies, doses to skin can be estimated using 

models that apply to an acute deposition on skin presented in Section 3.2, with the effect of 

inefficient showering taken into account using models presented in the following section. 

 

3.5 Effect of Inefficient Showering

Doses to skin depend on the time that contaminated material stays on or close to the skin 

surface. Washing reduces but probably does not eliminate all contamination, especially 

contamination attached to smaller particles that become embedded in pores and creases of skin. 

When showering is inefficient in removing contamination, the total dose due to a given 

deposition onto skin is higher than the dose delivered to the time of the first shower. 

In previous sections, we developed models to estimate the dose to skin from the time 

dermal contamination begins until the time of the first shower. The model formulation depends 

on whether deposition onto skin is treated as an acute event (Section 3.2) or as a continuous 

occurrence over some period prior to the time of the first shower (Sections 3.3.2 and 3.3.3). 

In this section, we present models to estimate the total dose to skin when showering is 

only partially efficient in removing contamination; these models include contributions to the 

45
dose after the time of the first shower. In presenting models to represent the effects of inefficient 

showering, we consider three distinct exposure scenarios: 

[1] an acute (instantaneous) deposition onto skin before the time of the first shower; 

[2] a continuous deposition onto skin that ceases before the time of the first shower; 

[3] a chronic (long-term) deposition onto skin that continues after the time of the first 

shower and for a number of successive days. 

In the third scenario, deposition onto skin may occur only during a fraction of the time on each 

day (e.g., while an individual is outdoors), rather than continuously throughout each day. 

Activity concentrations of radionuclides on skin are reduced by two processes while 

showering: washing (i.e., removal from the surface of skin by water and soap) and exfoliation of 

skin cells (i.e., normal loss of skin cells due to scrubbing or other abrasions). When showering 

removes only a fraction of the contamination on skin at that time and the time between showers 

does not vary greatly, progressively lower doses are delivered after each shower. 

3.5.1 Modeling of Removal of Radionuclides from Skin by Exfoliation and Washing

 

Removal (and renewal) of skin cells is a natural process with a cell turnover time of about 

20 days on the upper limbs, 30 days on the lower limbs, 40 days on the abdomen, and 120 days 

on the scalp (ICRP 1975). While some removal of skin cells occurs between showers, 

exfoliation probably occurs mainly as result of scrubbing while showering, and it is expected that 

the loss of skin cells is similar during each shower. 

By assuming that an individual would shower once each day, the fraction of the 

contamination on skin that is removed by exfoliation during each shower, denoted by , is 

numerically equal to the reciprocal of the skin cell turnover time in days. The same fraction  is 

assumed to apply to the activity concentration on skin at the time of each shower (i.e., on each 

day). Thus, some contamination is assumed to remain on skin after all cells that were present at 

the time of deposition are removed by exfoliation. 

The first shower may remove much of the contamination from skin, but subsequent 

showers are less efficient (Sharp and Chapman 1957; Friedman 1958; Fogh et al. 1999) as the 

46
remaining contamination becomes more embedded in skin folds and pores. In this report, the 

fraction of the activity concentration of radionuclides on skin that is removed by washing during 

each shower is denoted by j, where j counts each shower after a deposition on skin (j = 1,...,N). 

The fraction of the activity concentration of radionuclides on skin at the time of the jth 

shower that remains after that shower, taking into account removal by exfoliation of skin cells 

and washing, is estimated as j = 1 – (j + ). As noted above, the fraction removed by 

exfoliation, β, is assumed to be the same in all showers. The fraction removed by washing, γj, is 

assumed to decrease or remain constant in each successive shower. Recommended probability 

distributions of β and γj are discussed in Sections 4.7.1 and 4.7.2, respectively. 

3.5.2 Effect of Inefficient Showering – Acute Deposition Before First Shower

After an acute dermal contamination event (i.e., an event that is assumed to occur 

instantaneously) at time T0 after a detonation, the dose D1 received from time T0 to the time of 

the first shower, T1, is given by eq. (3-5) in cases of exposure to a single radionuclide and by 

eq. (3-6) in cases of exposure to a mixture of radionuclides in fallout from a nuclear detonation. 

The time Δt in those equations is equal to T1 – T0. 

If an individual takes N showers at times T1, T2, ..., TN, the total dose during the period 

from T0 to TN (i.e., the sum of the dose to the time of the first shower and the dose after the first 

shower that results from inefficient showering) in cases of contamination by a single 

radionuclide is given by: 

 

   

  





 





 





















  

N 

j

j

k

k

R

TT TT

N skin skin

jR jR e e DRFTCD

1

1

1

λ λ

0 α

λ

01 0

 (3-32) 

As indicated in eq. (3-2) (Section 3.2), the activity concentration of the radionuclide on skin at 

the time of an acute deposition, Cskin(T0), is estimated as Cgs(T0) × ARf, where Cgs is the activity 

concentration of the radionuclide deposited on the ground surface and ARf is the effective 

interception and retention fraction. In cases of contamination by a mixture of radionuclides in 

fallout, the total dose from time T0 to time TN is given by: 

47
    







 

































 

 

N

j

j

k

k

x

j

x

j

skin

x

N skin

x

TT

DRFTTCD

1

1

1

)1()1(

1

00 α

1 (3-33) 

When j = 1 (i.e., at the time of the first shower), the term is equal to 1.0, and doses to 

the time of the first shower, D1, obtained from eqs. (3-32) and (3-33) are the same as given in 

eqs. (3-5) and (3-6), respectively. A derivation of eq. (3-33) is given in Appendix D.1. A similar 

approach can be used to derive eq. (3-32). 























1

1

α

j

k

k

By subtracting the dose delivered to the time of the first shower, T1, from the total dose in 

eq. (3-32), the dose delivered after the time of the first shower that results from inefficient 

showering, denoted by Dsh, in cases of exposure to a single radionuclide is given by: 

 

   

  





 

































  

N 

j

j

k

k

R

TT TT

sh skin skin

jR jR e e DRFTCD

2

1

1

λ λ

0 α

λ

01 0

 (3-34) 

Similarly, the dose delivered after the time of the first shower in cases of exposure to a mixture 

of radionuclides in fallout is given by: 

    







 

































 

 

N

j

j

k

k

x

j

x

j

skin

x

sh skin

x

TT

DRFTTCD

2

1

1

)1()1(

1

00 α

1 (3-35) 

The time between an acute deposition and the first shower usually would be defined by 

the assumed scenario. This time may be as little as an hour or less or much as 24 hours if an 

individual is assumed to shower once each day. After the first shower, the time between 

showers, Tj – Tj–1, normally should be 24 hours, but any times between showers can be assumed. 

In principle, the dose Dsh should be evaluated assuming a large number of showers, N. It 

usually should be sufficient to set N at no more than 120 days, which is the largest turnover time 

for skin cells due to exfoliation (ICRP 1975). Doses from contamination that remains on skin 

after 120 showers should be negligible. 

The importance of the dose after the first shower compared with the dose to the time of 

the first shower depends on the time between an acute deposition onto skin and the first shower 

(T1 –T0) and the efficiency of showering (αj). For example, the total dose is dominated by the 

dose received before the time of the first shower, regardless of the times when deposition and the 

48
first shower occur, if showering is highly efficient in removing contamination (α is close to 

zero), but the dose received after the time of the first shower is dominant if the first shower 

occurs close to the time of deposition and each shower removes only a small fraction of the 

contamination (α is close to 1.0). The rate of decay of radionuclides deposited on skin also 

affects this comparison. For given times T0 and T1 and values of αj, the dose after the first 

shower generally increases as the decay rate decreases, and vice versa. 

Sections 4.7.1 and 4.7.2 discuss available data related to efficiencies of showering and 

the effect of different assumptions about T0, T1, and αj on the importance of the dose received 

after the time of the first shower compared with the dose to the time of the first shower. 

3.5.3 Effect of Inefficient Showering – Continuous Deposition Before First Shower

In Sections 3.3.2 and 3.3.3, models were developed to estimate the dose delivered to the 

time of the first shower when a continuous deposition of resuspended material onto skin at a 

constant rate occurs. In this section, we consider the effect of inefficient showering on the total 

dose when a chronic deposition ceases before the time of the first shower. 

As in Section 3.3.2, contamination of skin due to a continuous deposition of resuspended 

radionuclides is assumed occur for a period Tdep, starting at time T0 after a detonation and 

ending at time Tdep. After deposition ceases, skin is assumed to remain contaminated for an 

additional post-deposition period Tpost until the first shower. The dose delivered to the time of 

the first shower is the sum of the doses during deposition and the post-deposition period. If Dsh

again denotes the dose received after the time of the first shower (i.e., the additional dose that 

results from incomplete removal of contamination from skin by showering), the total dose is: 

 dep  post  DDDD sh (3-36) 

Equation (3-36) applies in cases of exposure to a single radionuclide or a mixture of 

radionuclides. The following discussion considers exposure to a mixture of radionuclides in 

fallout. However, the same approach can be used in cases of exposure to a single radionuclide. 

49
In cases of exposure to a mixture of radionuclides in fallout, doses Ddep and Dpost in 

eq. (3-36) are calculated using eqs. (3-19) and (3-25), respectively. These doses are unaffected 

by inefficient showering, since they are delivered before the time of the first shower. 

The dose delivered after the first shower, Dsh, can be obtained from eq. (3-35), which 

applies to an acute deposition at time T0, by substituting the time deposition ceases, Tdep, for T0, 

because doses at any time after deposition onto skin ceases depend only on the activity 

concentration of radionuclides on skin at time Tdep but do not depend on the time history of 

deposition onto skin between the time deposition begins, T0, and the time deposition ceases [see 

discussion following eq. (3-26) in Section 3.3.2.2]. Thus, Dsh in cases of a continuous deposition 

onto skin that ceases before the time of the first shower can be expressed as: 

    







 

































 

  

N

j

j

k

k

x

j

x

j

skin

x

sh depskin dep x

TT

DRFTTCD

2

1

1

)1()1(

1

α

1 (3-37) 

The model formulation in eq. (3-37) illustrates the importance of the activity 

concentration on skin at the time deposition ceases. However, eq. (3-37) has a different 

formulation than the models to estimate doses Ddep and Dpost in eqs. (3-19) and (3-25), 

respectively. The same model formulations are obtained by expressing the concentration 

Cskin(Tdep) in eq. (3-37) in terms of its parameters using eq. (3-23) evaluated at time Tdep. The 

dose Dsh then is given by: 

  







 

































 

 

N

j

j

k

k

x

j

x

j

depfD skin

x

sh gs x

TT

D DRFTTARVRFTC

2

1

1

)1()1(

1

0 0

0 α

1

0 36. )( (3-38) 

This formulation of the dose delivered after the first shower is more transparent in indicating the 

parameters used to estimate deposition on skin. It also is more convenient when the 

concentration on skin at the time deposition ceases, Cskin(Tdep), generally would not be known but 

would be calculated using eq. (3-23). 

Use of the deposition velocity, VD, in eq. (3-38) indicates that the model applies in 

scenarios involving resuspension by human activities (Section 3.3.2). However, as discussed in 

Section 3.3.3, eq. (3-38) also applies in cases of exposure to radionuclides resuspended by winds, 

in which case the deposition velocity is the same as the wind speed, VW. 

50
3.5.4 Effect of Inefficient Showering – Deposition Continues After First Shower

This section considers the effect of inefficient showering when a chronic (long-term) 

deposition of radionuclides onto skin continues after the time of the first shower and for a 

number of successive days. Such a scenario could occur, for example, when military personnel 

were stationed on a residence island in the Pacific for a period of days or more and were exposed 

to fallout resuspended by winds. Resuspension is the only source of long-term deposition onto 

skin considered explicitly in this report, and wind-driven resuspension at wind speed VW (m s–1) 

is assumed in the model equations presented below. Deposition on any given day can be 

intermittent (e.g., while an individual is outdoors, but not while indoors). In addition, as in the 

previous section, only the case of exposure to a mixture of radionuclides in fallout is considered. 

A long-term chronic exposure is equivalent to a sequence of daily depositions onto skin 

that take place from a starting day (m = 1) to an ending day (m = M); the timeline of the sequence 

of daily depositions, including the time deposition begins on each day, the time deposition ceases 

on each day, and the time of a shower on each day, is depicted in Fig. 3-1. On any given day, the 

dose from the time deposition begins on that day to the time of the next shower is estimated 

using the model equations developed in Sections 3.3.2 as applied to wind-driven resuspension by 

replacing the deposition velocity, VD, by the wind speed, VW; in cases of exposure to a mixture of 

radionuclides in fallout, eq. (3-19) gives the dose during the period of deposition onto skin 

(Ddep), and eq. (3-25) gives the dose from the time deposition ceases to the time of the next 

shower (Dpost). The dose after the time of the next shower from that day’s deposition onto skin 

when showering is assumed to be inefficient in removing contamination from skin is estimated 

using eq. (3-38). The total dose from depositions during all days of exposure is the sum of the 

doses from each day’s deposition. 

In a scenario involving resuspension by winds, the resuspension factor (RF) can be 

considered constant over the course of any given day. However, the resuspension factor is 

expected to decrease with time after deposition of fallout on the ground surface (Anspaugh et al. 

1975, 2002; Garger et al. 1997b). 

Various mathematical formulations of the time-dependence of the resuspension factor 

have been proposed. In the following discussion, the resuspension factor is assumed to decrease 

51
with time in accordance with a power function, similar to the assumed dependence on time of the 

activity of a mixture of radionuclides in fallout. The resuspension factor is assumed to decrease 

with time as: 

  yy tTRFtRF



00  (3-39) 

where RF0 is the resuspension factor at time T0 after a detonation when fallout is deposited on 

the ground surface and t is the time after deposition; the times T0 and t are in hours. 

A power-function representation of the time-dependence of the resuspension factor, as in 

eq. (3-39), was introduced by Garland (1982) and Garland et al. (1991), who proposed a value of 

the exponent y of 1, meaning that the resuspension factor was assumed to decrease with time as 

1/t. In modifications of the power-function model that were based on studies of resuspension of 

fallout from the Chernobyl accident, Garger et al. (1997b) proposed a value y of 1.07, and Nair et 

al. (1997) proposed values of y of 1 for the first 1,000 days (about 3 years) after deposition and 

zero at later times (i.e., a constant resuspension factor). 

Given the assumption about the time-dependence of the resuspension factor in eq. (3-39) 

and the equations for the dose from deposition on skin on a given day in the previous section, the 

total doses during the three time periods of interest from exposure over M days are as follows: 

Dose during all periods of deposition onto skin – 

     

  

 

















 





M

m

x

m

x

mdepm

x

mdep

y

m

x y

m

m

gs

dep fW skin

Tx TTTx

xx

TTRFTC

D DRFARV

1

)2(

,0

)1(

,,0

)2(

,

,0 ,01,00

,0

)2()1( )2)(1(

36.0

 (3-40) 

Dose during all periods from time deposition onto skin ceases to time of next shower – 

    



 















  





M

m

x

m

x

mmdep mdep

y

m

x y

m

m

gs

post fW skin

TTTT

x

TTRFTC

D DRFARV

1

)1()1(

,0, .

,0 ,01,00

,0

)1(

( )

36.0

 (3-41) 

52
Dose during all periods after time of next shower – 

        





 

  



















































 



M

m

N

mj

mj

k

k

j j

mdep m

y

m

x y

m

m

gs

sh fW skin

x

TT

TTTTRFTC

D DRFARV

1 1 1

)1-x( )1-x(

1

,0 ,01,00 ,0,

,0 α

1

36.0

 (3-42) 

The constant 0.36 again is a units conversion factor that is defined following eq. (3-8) in 

Section 3.3.2.1. These equations can be applied to periods of exposure when the resuspension 

factor (RF) is considered to be constant by setting the exponent y equal to zero. 

3.6 Modeling of Doses from Alpha-Emitting Radionuclides

Doses to skin from dermal contamination by radionuclides that emit alpha particles 

usually are not considered in radiation dose assessments. Neglect of this exposure pathway 

perhaps has been based on a view that alpha particles emitted by radionuclides are not 

sufficiently energetic to penetrate the epidermis and irradiate radiosensitive tissues in the basal 

layer of skin. As indicated by calculations presented in Section 4.6.2, neglect of external 

exposure to many alpha-emitting radionuclides that might be deposited on the body surface is 

reasonable if the nominal depth of radiosensitive tissues is taken to be 7 mg cm–2, as is normally 

the case in radiation protection (ICRP 1977), because ranges of alpha particles emitted by most 

radionuclides of potential concern are less than that depth. 

However, data reported by Whitton (1973) indicate that the average thickness of the 

epidermis in some regions of the body is about 4 mg cm–2, and that the thickness can be as low 

as 2 mg cm–2 in those regions in some individuals. Such thicknesses are less than ranges of 

alpha particles emitted by important radionuclides in fallout. An early analysis by Harvey 

(1971) indicated that the alpha dose rate to skin per unit activity concentration on the body 

surface could be as high as 104

 rem h–1 per μCi cm–2 for such radionuclides as 242Cm in some 

regions of the body. Since dose-rate factors of that magnitude are much higher than dose-rate 

factors for beta-emitting radionuclides, which are on the order of 10 rem h–1 per μCi cm–2 or less 

(Kocher and Eckerman 1987), alpha doses to skin could be important even though concentrations 

of alpha emitters in fallout may be much less than concentrations of beta emitters. 

53
54

Models presented in Section 3 were developed primarily to address doses to skin from 

beta-emitting radionuclides. However, the same models can be used to estimate doses to skin 

from alpha-emitting radionuclides deposited on the body surface. The only difference is in 

values of the dose-rate factor (DRF). Appropriate dose-rate factors are discussed in 

Section 4.6.1 for beta emitters and Section 4.6.2 for alpha emitters. 
T0,1 Tdep,1 T1 T2 T3 T4 T5 T6 T7 T8 

Exposure on first day (m=1)

T1 T0,2 Tdep,2 T2 T3 T4 T5 T6 T7 T8 

Exposure on second day (m=2)

T1 T2 T0,3 Tdep,3 T3 T4 T5 T6 T7 T8 

Exposure on third day (m=3)

T0,m = time when deposition on skin begins during given day of exposure; m=1,...,M

Tdep,m = time when deposition on skin ends during given day of exposure; m=1,...,M

Tj = time of showering on given day; j=1,...,N

All times are specified in hours after time of detonation 

T1 Tm-3 Tm-2 Tm-1 Tm Tm+1 Tm

Exposure on day m

T2 T0,m Tdep,m

...

......

Figure 3-1. Time sequence of occurrences in scenario involving multiple days of deposition onto skin due to wi

resuspension followed by long-term exposure of skin resulting from inefficiency of showering in removin

55
4. PARAMETERS IN MODELS TO ESTIMATE DOSES TO SKIN 

FROM DERMAL CONTAMINATION 

This section discusses recommended values of parameters in the models developed in 

Section 3 to estimate doses to skin from dermal contamination. Parameters discussed include the 

interception and retention fraction, r, and its adjustment factors introduced in eq. (3-4), the 

resuspension factor, the deposition velocity or wind speed, the dose-rate factor and its modifiers, 

and parameters in the models to account for inefficient showering. 

Parameter values discussed in this section are intended to apply in estimating doses to 

skin from dermal contamination by mixtures of radionuclides in fallout from nuclear detonations. 

Recommended parameter values are described by probability distributions to represent their 

uncertainty. A point estimate of each parameter that could be used in deterministic calculations 

(e.g., calculations to compare doses to skin from dermal contamination and doses from exposure 

to a contaminated ground surface described in Section 6) also is provided. 

4.1 Interception and Retention Fraction

The interception and retention fraction, r, is defined as the ratio of the mass of material 

that is deposited and retained per unit area on skin (mg cm–2) to the time-integrated flux density 

of material traveling towards the body (mg cm–2). In the case of exposure to descending fallout 

throughout the period of descent, the time-integrated flux density of material traveling towards 

the body is equal to the mass of material deposited per unit area on the ground surface. 

In this report, we mainly rely on data from the CENIZA-ARENA volcanic ash studies in 

Costa Rica to estimate interception and retention fractions in various regions of the body under 

conditions of exposure of military personnel at atmospheric weapons tests. Data obtained from 

wind-tunnel studies are used to complement and confirm data from the volcanic ash studies. As 

described in Section 2.2.1, the quantity estimated in the volcanic ash study is a skin 

contamination factor ah, which is defined as the ratio of the mass of descending ash that 

accumulated on a specific portion of an exposed body surface to the mass per unit area that was 

deposited on the ground surface; this quantity is given in units of cm2

. The interception and 

56
retention fraction then is estimated as the ratio of ah to the surface area of skin (s) over which ah

was measured [r = (ah/s); eq. (3-3) in Section 3.2]. 

Estimation of the interception and retention fraction, r, in different regions of the body is 

challenged by limitations in available data on the skin contamination factor, ah. As indicated in 

Table 2-2, estimates of ah are available for the forearms, face, forehead, and inside of the ears, 

but not for the torso, neck, or legs. A reasonable way to use the available data is to estimate the 

interception and retention fraction for regions of the body for which data are available and apply 

those estimates to other similar regions for which no data are available. The interception and 

retention fraction normally should be less than 1.0, given that skin cannot retain a mass of 

descending material per unit area larger than mass per unit area deposited on the ground surface. 

However, values of r greater than 1.0 are possible when inadvertent transfer of material from one 

region of the body (i.e., hand, forearms) to other regions (e.g., face, forehead) occurs. In 

addition, a larger mass per unit area than on the ground surface can accumulate in special regions 

of the body, such as the back of the neck under a collar, around the waist under a belt, on the shin 

area around the edge of a boot, or behind the ears. In these regions, a relatively small area of 

skin can accumulate particles that impact a larger area of the body. For example, particles that 

impact the back of the head may migrate and accumulate on skin under a collar. 

The following sections describe the probability distributions of interception and retention 

fractions, r, that are assumed to apply in various regions of the body. All assumed probability 

distributions are summarized in Table 4-1. 

4.1.1 Interception and Retention Fraction for Hair on Scalp

Measurements of the skin contamination factor, ah, for hair on the scalp are summarized 

in Table 2-2 and Fig. 2.1. Five distinct measurements for a male with a crew-cut hairstyle 

ranged from 10 to 585 cm2

. These measurements can be represented by a lognormal distribution 

with a GM of 182 cm2

 and GSD of 2.80. For a male with medium cut hair, six distinct 

measurements of ah ranged from 48 to 620 cm2

 and can be represented by a lognormal 

distribution with a GM of 163 cm2

 and GSD of 2.56. When all distinct measurements on all 

subjects are pooled, ah can be represented by a lognormal probability distribution with a GM of 

164 cm2

 and GSD of 2.45. 

57
For males, estimates of the surface area of the head have a mean of 1180 cm2

 and 

standard deviation of 160 cm2

 (Appendix A, Table A-6). These data can be represented by a 

lognormal probability distribution with a GM of 1169 cm2

 and GSD of 1.14. If we assume that 

the surface area of the scalp is about 60% of the surface area of the head and represent this 

uncertain fraction by a uniform probability distribution with a minimum at 0.5 and maximum at 

0.7, the surface area of the scalp can be represented by a lognormal probability distribution with 

a GM of 700 cm2

 and GSD of 1.14. 

By combining the skin contamination factor for all subjects and the surface area of the 

scalp described above, the resulting interception and retention fraction r = (ah/s) can be 

represented by a lognormal probability distribution with a GM of 0.23 and GSD of 2.45; the 90% 

credibility interval (CI) of this distribution is (0.053, 1.0). This probability distribution has about 

5% of its values greater than 1.0. Given that it is possible for material that accumulates on hands 

to be transferred to hair by running of fingers through hair, which is a common habit, this 

probability distribution is considered acceptable for estimating doses to skin of the scalp. 

The skin contamination factor, ah, for hair on the scalp should be positively correlated 

with the surface area of the head, s, given that a greater surface area increases the mass of 

descending ash that impacted that area; the same type of correlation should occur in other 

regions of the body. However, this correlation has a negligible effect on the uncertainty in the 

interception and retention fraction, r = ah/s, when the uncertainty in ah is much greater than the 

uncertainty in s, which is generally the case. This correlation is ignored in developing 

probability distributions of interception and retention fractions in any region of the body. 

4.1.2 Interception and Retention Fraction for Skin of Forearms

As indicated in Table 2-2, only three measurements of the skin contamination factor, ah, 

for the forearms were obtained in the volcanic ash studies (135, 66, and 172 cm2

). The last two 

values (66 and 172 cm2

) represent the amount of ash collected from forearms and hands. The 

geometric mean of the three measurements of ah is 115 cm2

. 

Estimates of the surface area of skin on the forearms in males have a mean of 1140 cm2

and standard deviation of 127 cm2

 (Appendix A, Table A-6). These data can be represented by a 

58
lognormal probability distribution with a GM of 1133 cm2

 and GSD of 1.12. Similarly, 

estimates of the surface area of skin on the hands, which have a mean of 840 cm2

 and standard 

deviation of 127 cm2

, can be represented by a lognormal probability distribution with a GM of 

831 cm2

 and GSD of 1.16. By adding the two probability distributions, the total surface area of 

the forearms and hands is assumed to have a GM of 1963 cm2

 and GSD of 1.14. 

The three measurements of the skin contamination factor, ah, for the forearms are 

insufficient to characterize its variability. Since the forearms and back of the hands often are 

covered by more abundant hair than the face and can be held in a horizontal position, a GSD of 

3.0 can be chosen for ah, similar to the estimated GSD for medium-cut hair indicated in Fig. 2-1. 

A lognormal probability distribution with a GM of 115 cm2

 and GSD of 3.0 has a 95th percentile 

of 700 cm2

, which is reasonably close to the largest measured value of ah for hair (620 cm2; 

Table 2-2). The 5th percentile of ah is 19 cm2

, which is the same as the larger measured value for 

the face discussed in the next section. Thus, the assumed lognormal probability distribution of 

the skin contamination factor, ah, for the forearms and hands seems reasonable. 

Using the skin contamination factor and skin surface area described above, the 

interception and retention fraction, r, for the forearms is assumed to be lognormally distributed 

with a GM of 0.06 and GSD of 3.0 [90% CI of (0.01, 0.36)]. This probability distribution has a 

reasonable 95th percentile, but the probability that r is greater than 1.0 is 0.7%. Thus, when 

eq. (3-4) is applied to estimate doses to skin of the forearms using Monte Carlo techniques to 

propagate uncertainty, a condition should be set to limit r to values less than 1.0. 

4.1.3 Interception and Retention Fraction for Skin of Face

As indicated in Table 2-2, only two measurements of the skin contamination factor, ah, 

for the face were obtained in the volcanic ash studies (2.5 and 19 cm2

). In the absence of more 

detailed information, we assume that a best estimate of the skin contamination factor for the face 

is the geometric mean of the two measured values, or 7 cm2

. 

The two measurements given above are insufficient to determine the variability in the 

skin contamination factor, ah, for the face. A greater number of measurements of ah is available 

for hair. As discussed in the previous section, the variability in ah for hair can be represented by 

59
a lognormal probability distribution with a GSD of either 2.80 for a male with a crew-cut 

hairstyle or 2.56 for a male with medium-cut hairstyle, and a GSD of 2.45 is obtained when the 

data from all subjects are pooled. 

It is expected that the variability in ah is larger for the face than for hair, in part because 

facial hair may or may not be present at the time of deposition. During the course of a day, facial 

hair on males can change from non-existent immediately after shaving to short rough growth 

(stubble) at the end of the day. This is potentially important when, on average and as indicated 

in Table 4-1, the interception and retention fraction for forearms, which are typically covered 

with some hair, is a factor of four greater than the interception and retention fraction for the face. 

This comparison indicates that the presence or absence of facial hair may add a variation of as 

much as a factor of four in the interception and retention fraction, which is equivalent to an 

uncertainty factor that can be represented by a GM of 1.0 and GSD of 2.3. 

If the GSD that represents the variability of data for hair is combined with the GSD of 2.3 

that accounts for the variability due to the presence or absence of facial hair (e.g., in quadrature 

or by Monte Carlo methods), a possible GSD of an uncertain ah of about 3.5 is obtained. In this 

study, we use a lognormal probability distribution with a GM of 7 cm2

 and GSD of 3.5 to 

represent the uncertainty in the skin contamination factor, ah, for the face. 

For males, data summarized in Appendix A.2 indicate that the surface area of the head 

has a mean of 1180 cm2

 and standard deviation of 160 cm2. The variability of the surface area of 

portions of human skin probably is described by lognormal probability distributions. We 

represent the uncertainty in the surface area of the head by a lognormal probability distribution 

with a mean of 1180 cm2

 and standard deviation of 160 cm2. This distribution has a GM of 

1169 cm2

 and GSD of 1.14. If we assume that the surface area of the face is about 40% of the 

surface area of the head and represent this uncertain fraction by a uniform probability 

distribution with a minimum at 0.3 and maximum at 0.5, the surface area of the face can be 

represented by a lognormal probability distribution with a GM of 460 cm2

 and GSD of 1.2. 

Using the skin contamination factor and skin surface area for the face described above, 

the interception and retention fraction, r, for the face was estimated using Monte Carlo methods 

60
of uncertainty propagation.11 The resulting probability distribution of r is lognormal with a GM 

of 0.015 and GSD of 3.6 [90% CI of (0.002, 0.12)]. We believe that the upper bound of this 

probability distribution is reasonable because unshaved skin of the face could have an 

interception and retention fraction similar to the value for crew-cut hair. 

4.1.4 Interception and Retention Fraction for Other Regions of Body

Interception and retention fractions, r, for other regions of the body can be assigned by 

analyzing similarities and differences between skin of the face and forearms and skin of other 

regions of interest. Accumulation of soil particles on special regions of the body, such as the 

back of the neck under a collar, is addressed in the next section. 

Deposition and retention on other regions of body that contain little or no hair and are in 

a vertical position when an individual is standing presumably is similar to deposition and 

retention on skin of the face. Such regions of the body include the back and sides of the naked 

torso, shoulders, and forehead. Thus, for those regions, we use the interception and retention 

fraction for skin of the face, which is represented by a lognormal probability distribution with a 

GM of 0.015 and GSD of 3.6 [90% CI of (0.002, 0.12)]. 

Similarly, the interception and retention fraction for the forearms could be used for other 

regions of the body covered by hair, such as the upper legs or lower legs above the edge of 

boots.12 Thus, for those regions, we use the interception and retention fraction for the forearms, 

which is represented by a lognormal probability distribution with a GM of 0.06 and GSD of 3.0 

[90% CI of (0.01, 0.36)]. 

Interception and retention on the front of the torso may be complicated by the presence of 

abundant hair on some persons but little or no hair on others. For individuals with chest hair, the 

interception and retention fraction for the forearms probably is appropriate, while data for skin of 

the face should be appropriate for individuals with little or no chest hair. Since information 

regarding the presence of hair on the front of the torso is not normally available, a distribution 

 

11 By taking 1,000 samples from the assumed probability distributions of ah and s using Latin hypercube 

sampling implemented in Crystal Ball® software (www.crystalball.com), a probability distribution of r

generated from 1,000 values of the ratio ah/s was obtained. 

12 Similar to forearms, upper legs can be exposed in a horizontal position (e.g., while sitting). 

61
that covers all situations could be used. If the probability distributions of r for the face and 

forearms/hands are combined with equal weights,13 the best fit to the resulting probability 

distribution is a lognormal distribution with a GM of 0.03 and GSD of 3.9 [90% CI of (0.003, 

0.28)]. This distribution is wider than either of the probability distributions of r for the face or 

forearms, because it accounts for uncertainty in interception and retention in both regions. 

The probability distributions described in this section are relevant in cases of exposure of 

bare skin or while wearing loose clothing. The term “loose clothing” refers to clothing that does 

not significantly affect the ability of depositing material to contact skin. Interception and 

retention is reduced if tightly fit clothing is worn (see Section 5 for additional discussions on the 

effect of clothing). As discussed in previous sections, when interception and retention fractions 

(r) are estimated as ah/s using probability distributions of the two parameters, values for many 

parts of the body should be constrained to not exceed 1.0. 

4.1.5 Interception and Retention Fraction for Special Regions of Body

Retention of particles on skin can be enhanced in special regions, such as the back of the 

neck beneath a collar, the waistline under a belt, the shin at the edge of a boot, or behind the ears. 

In those regions, accumulation of particles per unit area of skin can be larger than the mass per 

unit area impacting the body surface, due to migration of particles that are intercepted on other 

parts of the body; i.e., the interception and retention fraction, r, can be greater than 1.0. For 

example, particles that impact hair on the back of the head and are not retained there can roll or 

bounce and be trapped in the space between a collar and the back of the neck. Similar processes 

are responsible for enhanced accumulation in the other special regions mentioned above. 

The magnitude of the interception and retention fraction for the back of the neck under a 

collar can be estimated on the basis of simple geometrical considerations and available data. In 

the absence of a collar, or if a collar is very loose, the interception and retention fraction should 

be similar to that for skin of the face, given that the back of the neck at collar level is a nearly 

vertical surface with little or no hair. 

 

13 The two distributions were sampled using Monte Carlo techniques and combined by assigning 50% 

weight to the interception and retention fraction for the face and 50% weight to the interception and 

retention fraction for the forearms. 

62
If a collar is not loose, a fraction of the particles that impact hair in the occipital region 

and are not retained there may accumulate on skin under the collar, in addition to particles that 

impact the back of the neck. The lower limit of this fraction is zero, meaning that the amount of 

additional particles that accumulate under a collar is negligible (identical to the situation when a 

collar is loose). An upper limit of this fraction could be estimated at 20%, meaning that skin 

under a collar retains at most 20% of the particles that impact hair on the head and are not 

retained there. The estimate of 20% is obtained by observing that the surface area covered by 

hair in the occipital region can be as much as about 20% of the total surface area covered by hair. 

This value was chosen with respect to the total area covered by hair as opposed to the area of the 

entire head, because data from the volcanic ash studies are more abundant for hair. A uniform 

probability distribution between 0 and 0.2 was chosen to represent the uncertainty in the fraction 

(khair) of particles not retained on the scalp that are retained on skin under a collar. 

The interception and retention fraction (r) for the neck under a collar, including particles 

that are initially intercepted by hair on the back of the head, is calculated as the skin 

contamination factor for the back of the neck (ah neck) divided by the area of the neck beneath a 

collar (sneck): 

 

neck

hair

face hair hair

neck

hair

hair

hairh

neck hair

face

faceh

neck

neckh

neck

s

s rkr

s

s

s

a

ks

s

a

s

a

r



 



















1

1

 (4-1) 

The skin contamination factor for the back of the neck (ah neck) is the sum of the mass of particles 

that are intercepted and retained on the back of the neck and the mass of particles that do not 

stick to hair but are retained on the back of the neck divided by the concentration of particles that 

are deposited on the ground. The area of the neck beneath a collar (sneck) is about 1 × 5 inches to 

1 × 6 inches, or 32 to 38 cm2

. Allowing for uncertainty, the area of this region is represented by 

a uniform probability distribution between 30 and 40 cm2

. 

The interception and retention fraction (rneck) for the back of the neck was estimated as 

described above by using Monte Carlo methods of propagating uncertainty in the various 

parameters. The resulting probability distribution has a median value (50th percentile) of 1.5, a 

63
5th percentile of about 0.04, a 95th percentile of about 5, and a maximum value of about 8. This 

probability distribution is not well described by distribution functions, such as lognormal or 

triangular, that are used in this report to represent other uncertain parameters. A distribution 

function that reasonably fits the derived probability distribution is a gamma distribution 

(Decisioneering 2001) with 5th, 50th, and 95th percentiles at the values given above. This 

probability distribution is recommended to describe the uncertainty in the interception and 

retention fraction, r, for skin on the back of the neck under a collar. A majority of values in this 

probability distribution are greater than 1.0, which indicates a higher concentration on that part 

of the skin than the concentration of material deposited on the ground surface. 

The probability distribution of the interception and retention fraction for the back of the 

neck under a collar is assumed to be a reasonable choice for other special regions of the body, 

including the waistline under a belt, shin at the edge of a boot, or behind the ears. 

4.1.6 Interception and Retention Fraction for Material Resuspended by Winds

Another important consideration is the applicability of interception and retention 

fractions obtained from the volcanic ash study to deposition onto skin of fallout particles that are 

resuspended from the ground surface by winds. Interception and retention of wind-driven 

particles that impact the body of a standing person almost horizontally is conceptually similar to 

interception and retention of particles that settle by vertical motion on the body of a standing 

person, as in the case of depositing fallout. Fortunately, skin contamination factors (ah) have 

been measured under conditions in which individuals performed normal activities (mostly 

walking or standing). Those conditions included no wind or the presence of mild winds or air 

currents, as well as exposure times of 1 to 7 hours indicated in Table 2-2 that are similar to 

exposure times experienced by some military personnel. Estimated interception and retention 

fractions thus are average values for a combination of environmental conditions, including 

situations where particles were carried (or at least influenced) by winds, and they can be used to 

estimate doses to skin from wind-driven resuspension. As noted in Section 3.3.3, the dose to 

skin increases with increasing wind speed, not because of an increase in the interception and 

retention fraction but because of an enhanced flux of particles that impact the body surface. 

64
Wind-tunnel experiments performed by Asset and Pury (1954) and discussed in 

Section 2.2.2 included measurements using particles with a mass median diameter (MMD) of 

6.5 m and a wind speed of 5 mph (2.2 m s–1). Results include an estimated efficiency of 

particle retention on the hairy part of the forearms of volunteers (a quantity similar to the 

interception and retention fraction, r). As indicated in Table 2-3, the efficiency of retention was 

found to vary from 0.0054 to 0.009. Similar experiments using particles with an MMD of 

4.5 m and a wind speed of 5.5 mph (2.5 m s–1) were performed by Landahl (1944), who 

measured an efficiency of retention of about 0.02. In both experiments, skin and particles were 

dry. However, moist conditions similar those in the volcanic ash studies in Costa Rica can 

increase retention by a factor of 2.5 (Sheppard and Evenden 1994; see Section 2.1). Thus, if skin 

contamination occurs under moist conditions, the efficiency of retention estimated by Asset and 

Pury (1954) should increase to a range of 0.014 to 0.023, while the value reported by Landahl 

(1944) should increase to about 0.05. These estimates are consistent with the interception and 

retention fraction, r, for the forearms that we developed using data obtained in the volcanic ash 

studies, which has a geometric mean of 0.06 and 90% CI of (0.01, 0.34) (Table 4-1). 

On the basis of arguments presented above, we believe that interception and retention 

fractions for descending fallout can be applied to radioactive material resuspended by winds. 

4.2 Adjustments to Interception and Retention Fractions

As indicated in eq. (3-4) (Section 3.2), several adjustments factors are applied to 

interception and retention fractions, r, that are estimated on a mass basis from data obtained in 

the volcanic ash studies to develop effective interception and retention fractions, ARf, on an 

activity basis that apply to conditions of exposure of military participants at atmospheric nuclear 

tests at NTS or in the Pacific. This section discusses recommended probability distributions of 

these adjustment factors, which are intended to apply to mixtures of radionuclides in fallout. 

These recommendations are summarized in Table 4-2. 

65
4.2.1 Particle-Size Adjustment

The particle-size adjustment (PSa) is a unitless factor that is developed using data which 

indicate that retention on skin depends on particle size. This adjustment factor accounts for 

differences between the particle-size distribution of airborne material impacting the body at a 

location of exposure of military personnel of interest and the particle-size distribution for which 

skin contamination factors (ah) were measured in the volcanic ash studies. 

Skin contamination factors (ah) were estimated by measuring the mass of ash deposited 

on personnel during a few hours of fallout from eruption of the Irazu Volcano (Section 2.2.1). 

Measured particle-size distributions of volcanic ash on several days are summarized in Fig. 4-1. 

On the first day, those distributions had a median diameter of about 180 m, and some particle 

diameters were as large as 350 m. Three measurements of ah for hair were reported for that 

day. Particle-size distributions on all other days included particles of diameter up to 300 m, 

with a median diameter that varied between 60 and 80 m. Only the skin contamination factors 

(ah) that were measured after the first day, when the median particle size was about 70 m on 

average, were used to estimate interception and retention fractions (r). 

Kochendorfer and Ulberg (1967) indicated that the probability of retention on skin is 

inversely proportional to the median particle diameter (i.e., retention increases with decreasing 

median particle diameter as 1/d) at least at diameters greater than 100 m. At diameters less 

than 100 m, those investigators suggested that the probability of retention remains constant. 

Similarly, in experiments performed by Sheppard and Evenden (1994) and Driver et al. (1989), 

retention was found to decrease with increasing particle size for diameters greater than 50 m 

but was independent of particle size for diameters less than 50 m. 

On the basis of data summarized above, the dependence on particle diameter (d) of the 

probability that particles are retained on skin can be represented by the function: 











 



 μm50for 05

μm50for

)( d

d

a

a d

ds (4-2) 

66
where a is a constant. As indicated by eq. (4-3) below, the value of a is not needed in estimating 

a particle-size adjustment factor. 

4.2.1.1 Exposure to Small Particles

Given that the stabilization height of the cloud from a nuclear weapon detonation 

typically was about 30,000 ft or more, the settling time of 100-m fallout particles from a cloud 

is on the order of a few hours or more (Glasstone and Dolan 1977; Sehmel and Hodgson 1976). 

Thus, at locations where exposure to descending fallout occurred at times more than few hours 

after detonation, the size distribution of fallout particles probably was weighted more towards 

smaller particles. When fallout contained mostly smaller particles of diameter less than 100 m, 

the particle-size distribution can be assumed to have a median diameter of 50 m or less. Since 

smaller particles are more efficiently retained on skin than larger particles, interception and 

retention fractions obtained from the volcanic ash studies should be increased, since they apply 

to exposures to distributions of particle sizes in which the median diameter was about 70 μm and 

a substantial fraction of particles had a diameter greater than 100 μm. 

A similar situation occurs in cases of exposure to previously deposited fallout particles 

that were resuspended by winds or mild mechanical stresses (e.g., walking). Under such 

conditions, resuspended particles have diameters less than 100 m, and the median diameter 

usually is less than 50 m, even when previously deposited fallout contained a substantial 

fraction of larger particles (Sehmel 1984). 

In this report, the term “small particles” refers to size distributions by mass in which most 

particles have diameters less than 100 m and median diameter is less than 50 m. In cases of 

exposure to small particles, it is expected that retention was enhanced, compared with retention 

in the volcanic ash studies, by a particle-size adjustment factor PSa of about (70 m)/(50 m) = 

1.4, where 70 m is a median particle diameter in the volcanic ash studies (Fig. 4-1) and 50 m 

is a maximum median particle diameter in a distribution of small particles. 

A more rigorous approach to estimating PSa should take into account the particle-size 

distributions in the volcanic ash studies shown in Fig. 4-1 and the particle-size distribution at 

locations where military personnel were exposed. If p(d) is the probability density function of 

67
the particle-size distribution by mass, the mass of particles that accumulate on skin is 

proportional to the integral , where s(x) is the probability of retention as a 

function of particle diameter given in eq. (4-2).





0 d)()( xxsxp

14 

If the mass particle-size distribution in the volcanic ash studies (Fig. 4-1) and the 

distribution for an exposure situation of interest are denoted by p1(d) and p2(d), respectively, the 

particle-size adjustment factor (PSa) is given by: 











0 1

0 2

d)()(

d)()(

xxsxp

xxsxp

PSa (4-3) 

Using the particle-size distributions in the volcanic ash studies and assuming that all 

particles at a location of exposure to descending or resuspended fallout have a diameter less than 

50 m, the particle-size adjustment factor (PSa) estimated using eq. (4-3) varies from 1.3 to 1.5, 

where the range represents the minimum and maximum values of PSa obtained using the 

different distributions p1(d) shown in Fig. 4-1. The central value of PSa for exposure to small 

particles is about 1.4. Similarly, if 75% of radioactive particles to which military personnel were 

exposed have a diameter less than 50 m and 25% have a diameter of 50 to 100 m, the value of 

PSa estimated using eq. (4-3) is 1.3, with a range of 1.2 to 1.4. If 50% of the particles have a 

diameter less than 50 m and 50% have a diameter of 50 to 100 m, PSa becomes 1.2, with a 

range of 1.1 to 1.3. 

To account for uncertainty in the size distribution of small particles at a location of 

exposure of interest and uncertainty in particle-size distributions in the volcanic ash studies, a 

lognormal probability distribution with a GM of 1.3 and GSD of 1.1 [90% CI of (1.1, 1.5)] can 

be assumed to represent the particle-size adjustment factor (PSa) when exposure to particles of 

diameter less than 100 μm occurred (Table 4-2). 

 

 

14 In this and the following equation, the diameter of particles is denoted by x instead of d, so that the 

differential element dx is easily identified. 

68
4.2.1.2 Exposure to Large Particles

Distributions of particle sizes in descending fallout at locations close to ground zero are 

weighted toward larger diameters (Miller 1969) compared with particle-size distributions in the 

volcanic ash studies. In this report, the term “large particles” denotes particle-size distributions 

by mass in which a large fraction of particles have diameters greater than 50 m and the median 

is 100 m or greater. 

In cases of exposure to large particles, an interception and retention fraction, r, estimated 

from the volcanic ash studies should be corrected using a particle-size adjustment factor, PSa, 

with an average value less than 1.0. If the particle-size distribution of large particles has a 

median diameter of 150 m, for example, retention on skin should be reduced by a factor of 

about (70 m)/(150 m) = 0.47. By using eq. (4-3) and the distribution of particle sizes in 

fallout at 1.7 km from ground zero (GZ) of Shot DIABLO at NTS shown in Fig. 4-2, the 

estimated PSa is 0.6. A range of 0.56 to 0.63 is obtained when different particle-size 

distributions of volcanic ash [p1(d); Fig. 4-1] are used to estimate PSa. Similarly, the estimated 

PSa for fallout particles at 4 km from ground zero of Shot SHASTA (Fig. 4-2) is 0.5, with a 

range of 0.48 to 0.55. 

On the basis of these estimates and taking into account that the particle-size adjustment 

factor for large particles should be less than 1.0, a triangular probability distribution with a 

minimum at 0.4, mode at 0.8, and maximum at 1.0 can be used to represent the uncertainty in the 

particle-size adjustment factor (PSa) when exposure to large particles of diameter mostly greater 

than 100 μm occurred (Table 4-2). 

4.2.1.3 Exposure to Unknown Particle Sizes

If exposure to descending or resuspended fallout involved unknown particle sizes, a 

particle-size adjustment factor (PSa) intermediate between values that apply to exposure to 

mostly large or mostly small particles should be appropriate. Furthermore, the uncertainty in this 

adjustment factor in such cases should be greater than in cases of known exposure to mostly 

large or small particles. 

69
On the basis of the 95th percentile of the assumed lognormal probability distribution of 

PSa for small particles of 1.5 (Section 4.2.1.1) and the minimum of the triangular probability 

distribution of PSa for large particles of 0.4 (Section 4.2.1.2) and taking into account that a 

reasonable maximum PSa for small particles would be somewhat greater than 1.5, we assume 

that the particle-size adjustment factor for unknown particle-size distributions can be represented 

by a uniform probability distribution with a minimum at 0.4 and maximum at 1.6; the median of 

this distribution is 1.0 (Table 4-2). We note that this probability distribution implies that, on 

average, that assumed size distribution of particles of unknown size is about the same as size 

distributions in the volcanic ash study. 

4.2.2 Enhancement of Retention Due to Moisture on Skin

Retention of soil particles on skin is enhanced if skin is moist. Such an enhancement also 

should apply if soil is moist. There is limited information on the magnitude of such an effect. 

Data obtained by Sheppard and Evenden (1994) and described in Section 2.1 suggest that an 

enhancement in retention on skin due to moisture on skin or soil particles can be as high as a 

factor of 2.5. That study indicates that interception and retention fractions obtained from the 

volcanic ash studies should be adjusted downwards or upwards when applied to military 

personnel who were exposed under less or more humid conditions than in the volcanic ash 

studies, respectively. In addition, since the highest enhancement factor observed by Sheppard 

and Evenden (1994) is based on experiments in which a subject crushed and handled soil by 

hand under dry or moist conditions, an enhancement factor of 2.5 probably is an upper bound 

when applied to deposition of airborne soil particles on skin under the most humid conditions. 

Separate probability distributions of the enhancement factor due to moisture (EM) are 

developed for dry and humid conditions. These distributions should apply to most exposures at 

NTS and in the Pacific, respectively. 

Given the warm temperatures and high humidity in Costa Rica where the volcanic ash 

studies were carried out and given that study subjects were engaged in mild physical activity, 

estimates of interception and retention of particles obtained from those studies should be 

70
applicable in the Pacific, with little adjustment.15 The enhancement factor due to moisture (EM) 

for military personnel in the Pacific could be represented by a uniform probability distribution 

between 0.8 and 1.5. This distribution has a mean value slightly greater than 1.0 and, thus, 

incorporates an assumption that, on average, the effect of humidity in the Pacific is somewhat 

greater that in Costa Rica. The uncertainty in this enhancement factor accounts for an 

assumption that exposure conditions on any day in the Pacific can differ from the average 

exposure conditions in the volcanic ash studies in Costa Rica. 

Conditions at NTS generally were much dryer than in Costa Rica.16 Given that sweat 

evaporates rapidly in dry air, little buildup of moisture on skin of military personnel at NTS is 

expected. We assume that an enhancement factor due to moisture (EM) at NTS can be 

represented by a uniform probability distribution between 0.5 and 1.0, which gives a mean 

enhancement factor less than 1.0. This distribution reflects the belief that retention of particles 

on skin generally would be less at NTS than in Costa Rica, due to the dryer conditions. 

4.2.3 Enrichment of Specific Activity

A set of experiments using soils labeled with uranium (Sheppard and Evenden 1994) 

discussed in Section 2.1 indicated that the activity per unit mass (specific activity) of soil on skin 

can be greater than the activity per unit mass of soil. This enrichment of specific activity 

occurred because skin retained smaller particles more efficiently and the activity on particle 

surfaces per unit mass of soil increased with decreasing particle size. The enrichment of specific 

activity should be largest for larger particles and minimal for the smallest particles. For sand 

particles, which tend to be relatively large, the enrichment of specific activity was as high as a 

factor of 8 to 10; such a high enrichment was obtained when many sand particles were too large 

to be retained efficiently on skin. For loamy soil, this enrichment factor varied from 2 to 7, 

 

15 The temperature in the Marshall Islands varies between 75 and 85°F, and the average relative humidity 

is 80%. (Source: http:www.spc.int/prism/county/mh/stats/Geog/climate.htm; accessed September 2005.) 

16 For example, the monthly average relative humidity at 4 am in Las Vegas, which is close to the time of 

many detonations and subsequent exposures of military personnel, varies between 25% and 50% and the 

annual average is about 40%. The annual average relative humidity during the day is 20 to 30%, 

depending on the hour of the day. (Source: National Oceanic and Atmospheric Administration, 

http://www.wrh.noaa.gov/vef/climate/index.php; accessed September 2005.)

71
while the lowest enrichment factors (< 2) were observed for particles of soils rich in clay, which 

tend to have the smallest particle sizes and can readily adhere to skin. 

The enrichment of specific activity described above occurs when radionuclides are 

preferentially found on the surface of particles, as in the experiments by Sheppard and Evenden 

(1994). If radionuclides are distributed in the volume of particles, no enrichment is expected for 

any particle-size distribution because the activity per unit mass would not depend on particle 

size. When fallout particles are formed after a nuclear detonation, fractionation of radionuclides 

occurs, and some radionuclides (mainly refractory elements) tend to be distributed in the volume 

of particles, while others (mainly volatile elements) tend to be distributed on the surface of 

particles (Hicks 1982; Section IV.C.2.1.2 of NRC 2003). Fallout at locations close to ground 

zero (e.g., within the boundary of NTS) is expected to be enriched in refractory elements that 

tend to be dispersed in the volume of larger particles, which fall to Earth relatively rapidly, and 

depleted in volatile elements that tend to be attached to the surface of smaller particles, which 

fall to Earth more slowly and, thus, are carried farther from ground zero by winds.

At locations far from ground zero, fallout particles tend to be small (diameters less than 

100 m, with a median diameter less than 50 m), and they probably contain a higher proportion 

of volatile radionuclides (e.g., cesium, strontium and iodine) that are preferentially deposited on 

the surface of particles. Little or no enrichment of specific activity is expected when most 

radionuclides in fallout are volatile and, thus, are likely to be located on the surface of fallout 

particles and the particle-size distribution is heavily weighted towards small particles, which are 

efficiently retained by skin. 

We assume that the uncertainty in the specific-activity enrichment factor (EF) for small 

particles can be represented by a left-triangular probability distribution with a minimum and 

mode at 1.0 and maximum at 2.0 (Table 4-2). The upper bound of this distribution was obtained 

by observing that the probability that 100 m particles are retained on skin can be half the 

probability of retention of 50 m particles, and that the probability of retention is expected to be 

constant for particle diameters less than 50 m [Section 4.2.1, eq. (4-2)]. 

At locations close to ground zero, exposure to descending fallout mainly involves 

particle-size distributions that are heavily weighted towards large particles; exposure to mostly 

large particles also can occur in resuspension scenarios that involve vigorous stresses (e.g., 

72
resuspension by a nuclear detonation). Since fallout at such locations probably contains a higher 

proportion of refractory radionuclides that are distributed in the volume of particles, extreme 

enrichments of the specific activity of particles deposited on skin seem unlikely. However, since 

volatile radionuclides that are preferentially distributed on the surface of fallout particles are 

found even at locations close to ground zero, moderate levels of enrichment seem possible. For 

distributions of mostly large particles, available data indicate that a reasonable upper bound of 

the specific-activity enrichment factor (EF) is about 4. The lowest possible, but unlikely, value 

of EF is 1.0 (no enrichment of specific activity). Thus, in cases of exposure to mostly large 

particles, we assume that the uncertainty in the specific-activity enrichment factor (EF) can be 

represented by a triangular probability distribution with a minimum at 1.0, mode at 2.5, and 

maximum at 4.0 (Table 4-2). 

In cases of exposure to unknown distributions of particle sizes, the specific-activity 

enrichment factor can vary from 1.0 (no enrichment) to 4.0 (maximum enrichment), but we 

expect that lower values are more likely. A log-uniform probability distribution between 1.0 and 

4.0 is assumed to represent the uncertainty in the specific-activity enrichment factor (EF) in such 

cases; the median of this distribution is 2.0 (Table 4-2) and the mean is 2.2. 

Discussions in this section about enrichment of the specific activity of particles deposited 

on skin apply to the entire inventory of radionuclides in fallout. Specific-activity enrichment 

factors (EF) could be developed for specific radionuclides; a distinction could be made, for 

example, between refractory and volatile radionuclides. However, it is impractical to develop 

such enrichment factors when fallout includes a large number of radionuclides, especially 

immediately after a detonation, and the extent of fractionation of different radionuclides in 

fallout from particular detonations is largely unknown. 

4.2.4 Activity-Weight Adjustment Factor

Interception and retention fractions (r) derived from measurements of skin contamination 

factors (ah) in the volcanic ash studies represent interception and retention on a weight (mass) 

basis; i.e., ah is defined as the weight of volcanic ash particles retained on skin in a given region 

of the body divided by the weight of ash deposited per unit area on the ground surface. 

However, in fallout from nuclear weapon detonations, the activity particle-size distribution, 

73
which is the quantity of interest in estimating dose, generally is not the same as the weight 

particle-size distribution. For example, in fallout at a distance of 4.2 miles from ground zero of 

Shot SHASTA at NTS, 24% of the weight consisted of particles of diameter less than 100 m, 

but those particles carried only 0.75% of the total activity (Miller 1969; Figs. 13 and 15). Since 

most particles that could be retained on skin have a diameter less than 100 m, the activity of 

particles retained on skin relative to the activity of fallout deposited on the ground would be 

smaller at locations close to ground zero at NTS than indicated by values of the interception and 

retention fraction, r, derived from the volcanic ash studies. In the example noted above, an 

activity-weight adjustment factor (AW) of 0.0075/0.24 = 0.03 could be used to reduce r. In a 

similar analysis of fallout at 2.5 miles from ground zero of Shot SHASTA, 32% of the weight 

consisted of particles of diameter less than 100 m, but those particles carried only 0.30% of the 

total activity (Miller 1969; Figs. 11 and 12). Those data give an estimated activity-weight 

adjustment factor (AW) of 0.01. The same type of situation was observed in fallout at 1.1 miles 

from ground zero of Shot DIABLO at NTS. In that case, 30% of the weight of fallout particles 

consisted of particles of diameter less than 100 m, but those particles carried only 0.60% of the 

total activity (Miller 1969; Figs. 8 and 9), and the resulting AW is 0.02. These estimates of AW

are expected to represent lower bounds, because particles of diameter greater than 100 m also 

can be retained on skin, albeit with a much lower probability than smaller particles. 

On the basis of data on activity and weight particle-size distributions in fallout at NTS 

described above, the activity-weight adjustment factor (AW) that applies in cases of exposure to 

large fallout particles of diameter mostly greater than 100 μm could be represented by a 

lognormal probability distribution with a 90% CI of (0.01, 0.1) (Table 4-2). This distribution has 

a GM of 0.032 and GSD of 2.0. The GM is about the same as the estimated AW in fallout at 

4.2 miles from ground zero of Shot SHASTA. 

If exposure to small particles of diameter mostly less than 100 m occurred, activity and 

weight particle-size distributions consisted mostly of particles than can be retained on skin. This 

situation probably occurred in most exposures far from ground zero in the Pacific, exposures to 

fallout that was resuspended by winds or light vehicular traffic, and exposures to the fraction of 

fallout resuspended by nuclear detonations at NTS that remained airborne after larger particles 

fell to Earth. In cases of exposure to mostly small particles, little adjustment to the interception 

74
and retention fraction should be required to account for differences in activity and weight 

particle-size distributions. To account for uncertainty in the activity and weight particle-size 

distributions, the activity-weight adjustment factor (AW) for small particles could be represented 

by a right-triangular probability distribution with a minimum at 0.7 and a mode and maximum at 

1.0 (Table 4-2). The median and mean of this distribution is 0.9. 

When exposure to unknown distributions of particle sizes occurred, the activity-weight 

adjustment factor (AW) could range from a value that represents the low end of possible values 

for large particles to a value that represents the high end of possible values for small particles. 

However, extreme values should be unlikely. We represent an uncertain AW in such cases by a 

log-triangular probability distribution with a minimum at 0.01, mode (and median) at 0.1, and 

maximum at 1.0 (Table 4-2). The mean of this distribution is 0.15. 

4.2.5 Exposure to Known Mixtures of Large and Small Particles

The development of adjustments to the interception and retention fraction (r) to account 

for particle size (Section 4.2.1), enrichment of specific activity (Section 4.2.3), and differences 

between activity and weight particle-size distributions (Section 4.2.4) involved assumptions that 

most of the activity of radionuclides was carried either by larger particles of diameter mostly 

greater than 100 μm or by smaller particles. Adjustment factors that would apply to unknown 

distributions of particle sizes also were considered. 

There may be situations where military personnel at atmospheric nuclear tests were 

exposed to distributions of particle sizes in which substantial fractions of the activity of 

radionuclides were carried by small and large particles and those fractions can be estimated. In 

such situations, doses from dermal contamination can be estimated by estimating doses for the 

two size fractions separately using the appropriate adjustments to the interception and retention 

fraction for each size fraction and adding the two doses. Adjustment factors that apply to 

unknown distributions of particle sizes are not intended to be used in such cases. 

 

75
4.3 Resuspension Factor 

Measured resuspension factors associated with outdoor mechanical stresses range from 

10–10 to 10–3 m–1, and values ranging from 10–11 to 10–4 m–1 have been measured for resuspension 

by winds (Sehmel 1984). Resuspension factors relevant to processes modeled in this report were 

measured at sites where nuclear weapons were tested. Data on resuspension factors associated 

with vehicular traffic are given in Table 12.9 of Sehmel (1984) and summarized in Appendix A, 

Table A-9. Resuspension factors associated with winds are given in Table 12.7 of Sehmel 

(1984) and summarized in Appendix A, Table A-10. Except as noted, the reported resuspension 

factors presumably apply at a height above ground of about 1 m. 

This section discusses available data and develops recommendations on probability 

distributions of resuspension factors for use in different exposure scenarios involving human 

activities or resuspension by winds. The recommended probability distributions are summarized 

in Table 4-3. In using resuspension factors to estimate dermal contamination, it is important to 

identify particle sizes to which a particular resuspension factor applies to ensure that appropriate 

values of the particle-size adjustment factor (PSa), specific-activity enrichment factor (EF), and 

activity-weight adjustment factor (AW) are used to estimate effective interception and retention 

fractions (ARf) [eq. (3-4) and Section 4.2]. Relevant particle sizes are noted in discussing 

particular resuspension factors. 

4.3.1 Resuspension Associated with Human Activities

This section considers resuspension factors associated with vehicular traffic, walking, and 

helicopter take-off or landing. These stresses are potentially relevant in exposures of military 

personnel at atmospheric nuclear tests. 

4.3.1.1 Resuspension Due to Vehicular Traffic

As indicated in Table IV.C.2 of the NRC (2003) report, a resuspension factor of 10–5 m–1

is often assumed in dose reconstructions for military personnel. That resuspension factor is 

intended to be an upper bound that applies to resuspension due to walking, most vehicular traffic, 

76
and other light activities. In unusual scenarios involving assaults or marches behind armored 

vehicles at NTS, an upper-bound resuspension factor of 10–3 m–1 is assumed. 

Resuspension factors associated with mechanical stresses, mainly moving vehicles, at 

desert sites where nuclear weapons were tested summarized in Table A-9 range from about 10–8

to nearly 10–3 m–1. The highest values were measured at a height above ground of 0.3 m. On the 

basis of data on wind-driven resuspension summarized in Table A-10 that show a decrease in the 

resuspension factor with increasing height, the highest resuspension factors in Table A-9 could 

substantially overestimate values at a height of 1 m. A significant difference in resuspension at 

different heights above ground could be important at NTS, given that speed limits were imposed 

on vehicles in contaminated areas. However, reductions in wind-driven resuspension at a height 

of 1 m compared with 0.3 m may not apply to resuspension due to vehicular traffic, because the 

latter may provide more vigorous disturbances of surface soil than normal winds, even at low 

vehicle speeds. No other resuspension factors at 1 m associated with vehicular traffic at desert 

sites exceed 10–4 m–1. At the other extreme, a resuspension factor as low as about 10–8 m–1 was 

reported at a desert site in Australia during a road survey at 1 to 2 days after a detonation. More 

common lower values of the resuspension factor are around 10–7 m–1. 

Given the quality of available data, we define a single probability distribution of the 

resuspension factor associated with vehicular traffic that applies at NTS and in the Pacific and at 

heights of 0 to 2 m above the ground surface; 2 m represents the maximum height of most 

individuals while standing on the ground. On the basis of data in Table A-9, we assume that the 

resuspension factor associated with vehicular traffic can be represented by a lognormal 

probability distribution with a 90% CI of (4 × 10–7, 10–3) m–1; this distribution has a GM of 

2 × 10–5 m–1 and GSD of 11 (Table 4-3). Since dust clouds generated by vehicular traffic 

presumably can reach 2 m in height, we assume that this resuspension factor can be applied in 

estimating dermal contamination in any region of the body. 

Most exposures of military personnel to radionuclides that were resuspended by vehicular 

traffic probably involved smaller particles of diameter less than about 100 μm, regardless of the 

particle-size distribution on the ground surface. This would be the case if fallout consisted 

mainly of smaller particles (e.g., in most fallout on residence islands in the Pacific). At NTS, 

where most fallout consisted mainly of larger particles, resuspension by vehicular traffic 

77
nonetheless could have resulted in exposure mainly to smaller particles in most cases. The 

extent of resuspension of larger particles by vehicles often was affected by speed limits at the 

site. In addition, when an individual was located at an appreciable distance from a moving 

vehicle, larger resuspended particles with very short settling times could have redeposited on the 

ground before exposure occurred. 

There could be exceptions to the expectations described above. For example, if an 

individual was located close to moving vehicles, deposition of larger resuspended particles onto 

skin in lower regions of the body could have occurred. Marching behind groups of armored 

vehicles also could result in unusually high resuspension of larger particles and deposition onto 

skin when the greater height of a cloud of resuspended particles is taken into account. In such 

cases, it might be appropriate to assume that resuspended material contained a mixture of small 

and large particles, which could be considered separately in estimating dermal contamination. 

4.3.1.2 Resuspension Due to Walking

Resuspension due to walking results in airborne concentrations of resuspended material 

that apparently decrease with height within 2 m of the ground surface. In contrast to 

resuspension due to vehicular traffic, it may be reasonable to develop separate resuspension 

factors associated with walking at heights close to the ground and at greater heights, because 

walking should be a considerably less vigorous disturbance than vehicular traffic. 

Limited data summarized in Table A-9 indicate that resuspension factors associated with 

walking range from 1  10–6 to 3  10–4 m–1 at a height of 0.3 m. On the basis of those data, a 

reasonable probability distribution for use in estimating doses to skin from dermal contamination 

in lower regions of the body is a lognormal distribution with a 90% CI of (10–6, 3 × 10–4) m–1; 

this distribution has a GM of 2 × 10–5 m–1 and GSD of 5.7 (Table 4-3). The resuspension factor 

associated with walking to be used in estimating doses to skin in upper regions of the body 

presumably should be lower. On the basis of limited data summarized in Table A-9, a 

reasonable representation of the resuspension factor that applies in upper regions of the body is a 

lognormal probability distribution with a 90% CI of (10–8, 2 × 10–6) m–1; this distribution can be 

approximated by a distribution with a GM of 1 × 10–7 m–1 and GSD of 6.2 (Table 4-3). 

78
Exposure to radionuclides that were resuspended by walking usually should involve 

small particles only. Although walking could result in contamination of feet and ankles by large 

particles as dust is kicked up by shoes, measured resuspension factors associated with walking 

do not account for this process. 

4.3.1.3 Resuspension Due to Helicopter Take-off or Landing 

A less common exposure scenario for military personnel involves resuspension of 

material due to helicopter take-off or landing and exposure at locations close to the site of 

resuspension. This type of scenario apparently occurred occasionally at NTS. 

No measurements of resuspension factors associated with this type of stressor are 

available. However, helicopter take-off or landing results in strong local air currents that 

presumably generate substantially more vigorous lifting forces for particles on the ground and, 

thus, more resuspension than vehicular traffic. We assume that a reasonable representation of a 

resuspension factor in this case is a lognormal probability distribution with a 90% CI of (10–4, 

10–2) m–1; this distribution has a GM of 10–3 m–1 and GSD of 4.0 (Table 4-3). 

It is reasonable to assume that particles of all sizes are resuspended during helicopter 

landing or takeoff. Therefore, a particle-size distribution of resuspended radioactive material 

consistent with the particle-size distribution on the ground should be assumed. 

4.3.2 Wind-Driven Resuspension

Table A-10 summarizes measured resuspension factors associated with wind stresses at 

nuclear weapons testing sites. The lowest resuspension factors (3  10–10 and 2  10–9 m–1) 

involved resuspension of plutonium at NTS. More typical low resuspension factors are about 

10–8 to 10–7 m–1. The largest measured resuspension factor was 3  10–4 m–1 at a height of 0.3 m 

above ground; a resuspension factor of 10–5 m–1 at a height of 0.6 m was reported in the same 

study. We assume that these data represent wind-driven resuspension at NTS and in the Pacific. 

In addition to the decrease with increasing height above ground, resuspension factors 

associated with winds decrease over time after deposition (Anspaugh et al. 1975, 2002; Garger et 

79
al. 1997b; Garland 1982, 1992; Nair et al. 1997). Data reported by Sehmel (1984) suggest that 

upper credibility limits of the resuspension factor associated with winds of 10–4 m–1 and 10–5 m–1

are reasonable at times after deposition within 6 months and at later times, respectively. On the 

basis of available data and an assumption that probability distributions of the resuspension factor 

would be applied at NTS and in the Pacific, reasonable lower credibility limits of a resuspension 

factor associated with winds are 10–8 m–1 at times after deposition within 6 months and 10–10 m–1

at later times. 

Available data summarized above suggest that a lognormal probability distribution of the 

resuspension factor associated with winds with a 90% CI of (10–8, 10–4) m–1 (GM of 10–6 m–1; 

GSD of 16) is reasonable at short times after detonation (Table 4-3). A lower resuspension 

factor should be used when exposure occurred at longer times after detonation. A reasonable 

assumption would be a lognormal probability distribution with a 90% CI of (10–10, 10–5) m–1

(GM of 3 × 10–8 m–1; GSD of 33). These probability distributions are intended to apply to 

normal wind conditions; they may not apply in cases of intense winds of short duration. 

If we define the uncertainty in a resuspension factor as the ratio of the 95th percentile of 

an assumed probability distribution to the median, uncertainties in the recommended 

resuspension factors associated with winds described above are a factor of 100 or more. These 

uncertainties are much larger than the uncertainty of a factor of 10 proposed by Anspaugh et al. 

(2002). That uncertainty factor is intended to apply to an annual-average resuspension factor. 

Given the variability in available data, and taking into account that the data usually represent 

resuspension over periods of much less than a year, we believe that an uncertainty factor of 10 

could substantially underestimate the uncertainty in a resuspension factor associated with winds 

that applies over periods of a small fraction of a year. This is a potentially important 

consideration when exposures of military personnel often were of short duration, especially at 

NTS. Our recommended probability distributions are intended to account for this possibility. 

We also acknowledge, however, that an uncertainty factor on the order of 10 could be 

appropriate in cases of exposure over periods of several months or more, as often occurred on 

residence islands in the Pacific. 

80
As in the case of resuspension due to walking, only smaller particles (diameters less than 

100 μm) generally are resuspended by normal winds. This should be a reasonable assumption at 

any height above ground. 

4.3.3 Resuspension by Nuclear Detonations at NTS

A scenario that occurred only at NTS involved resuspension of previously deposited 

fallout by a nuclear detonation and subsequent exposure of military personnel at locations near 

ground zero at times within a few hours after detonation. Inhalation doses in this type of 

scenario were assessed by Kocher et al. (2009). Results of that assessment of relevance to 

estimating dermal contamination are summarized below. 

Resuspension of previously deposited fallout by a nuclear detonation at NTS occurred in 

two distinct regions: the region closest to ground zero, referred to as the thermal-pulse region, 

where the intense thermal pulse produced in a detonation was an important cause of 

resuspension, and the region beyond the thermal-pulse region, referred to as the blast-wave 

region, where significant resuspension was caused only by the blast wave and associated high 

winds. Resuspension was higher in the thermal-pulse region, due to the importance of the 

thermal pulse and associated precursor to the blast wave in that region and the higher wind 

speeds associated with the blast wave compared with wind speeds in the blast-wave region. 

Exposure of military personnel may have occurred in both regions. Exposure in the 

thermal-pulse and blast-wave regions may have occurred when observers or maneuver troops 

entered those regions within a few hours after a detonation. In addition, forward observers were 

located in the blast-wave region at the time of some detonations, and those observers may have 

remained in the blast-wave region or entered the thermal-pulse region at times after a detonation. 

No forward observers were located in the thermal-pulse region at the time of a detonation. 

In estimating dermal contamination by old fallout that was resuspended by a nuclear 

detonation, two parameters are used to describe resuspension. The first is the resuspension factor 

that applies to all previously deposited fallout, which incorporates an assumption that fallout 

particles of all sizes were resuspended to the same extent in the thermal-pulse and blast-wave 

regions. As described in Section 3.3.4, this resuspension factor would be used to estimate 

81
dermal contamination of forward observers in the blast-wave region at the time of a detonation 

due to redeposition of large particles that carried nearly all the activity of resuspended old fallout 

and fell to Earth within a few minutes. During the short period of redeposition of large particles, 

dermal contamination of forward observers due to the slower redeposition of small particles that 

carried a very small fraction of the activity of resuspended old fallout would be negligible. The 

second parameter, which would be used to estimate dermal contamination of personnel who 

entered the thermal-pulse or blast-wave region at some time after a detonation and dermal 

contamination of forward observers during times spent in the blast-wave region after large 

particles were redeposited, is the fraction of the activity of resuspended fallout that was carried 

by small particles and remained airborne for times as long as a few hours. 

Kocher et al. (2009) judged that the resuspension factor that applies to all previously 

deposited fallout in the thermal-pulse region can be represented by a lognormal probability 

distribution with a GM of 10–3 m–1 and 90% CI of (10–4, 10–2) m–1 (GSD of 4.0). If it is assumed 

that resuspended material in the thermal-pulse region would be distributed uniformly to a height 

of 100 m, a resuspension factor of 10–3 m–1 corresponds to an assumption that 10% of all old 

fallout in that region was resuspended. In the blast-wave region, the resuspension factor that 

applies to all previously deposited fallout was assumed to be much lower and more uncertain, 

due to the less intense stressors and the decrease in wind speed associated with a blast wave with 

increasing distance beyond the thermal-pulse region. A lognormal probability distribution with a 

GM of 10–5 m–1 and 90% CI of (10–7, 10–3) m–1 was assumed (GSD of 16; Table 4-3). Again, 

this resuspension factor would be used to estimate dermal contamination of forward observers in 

the blast-wave region at the time of a detonation due to redeposition of large particles that carried 

nearly all the activity in resuspended old fallout. 

The fraction of the activity of resuspended fallout that was carried by small particles and 

remained airborne for an extended period after a detonation should be about the same as the 

inhalable fraction of resuspended fallout estimated by Kocher et al. (2009), which was assumed 

to consist of particles of diameter less than 100 μm. On the basis of data on activity particle-size 

distributions in fallout at NTS, inhalable particles carried a very small fraction of the activity of 

radionuclides in resuspended old fallout. Kocher et al. (2009) judged that the inhalable fraction 

of the activity of resuspended fallout that remained airborne for an extended period in the 

82
thermal-pulse and blast-wave regions can be represented by a lognormal probability distribution 

with a GM of 0.01 and 90% CI of (0.001, 0.1); the GSD of this distribution is 4.0. 

Combining the probability distributions of the two parameters described above gives a 

resuspension factor that applies to small particles in old fallout that was resuspended by a 

detonation and could be deposited on skin of military personnel who were exposed in the 

thermal-pulse or blast-wave region at times after large resuspended particles had redeposited and 

were no longer airborne. Limits of the 90% CI of the resulting probability distribution are 

rounded to the next lowest or highest power of 10 to better represent uncertainties in these 

estimates. In the thermal-pulse region, the desired resuspension factor is represented by a 

lognormal probability distribution with a GM of 10–5 m–1 and 90% CI of (10–7, 10–3) m–1 (GSD 

of 16; Table 4-3). The resuspension factor that applies to all previously deposited fallout and the 

inhalable fraction of resuspended fallout (i.e., the fraction of the resuspended activity carried by 

small particles) contribute about equally to this uncertainty. In the blast-wave region, the desired 

resuspension factor is represented by a lognormal probability distribution with a GM of 10–7 m–1

and 90% CI of (10–10, 10–4) m–1 (GSD of 67; Table 4-3). The resuspension factor that applies to 

all previously deposited fallout is the dominant source of uncertainty. 

Equations (3-28) and (3-31) in Section 3.3.4 present a model to estimate dermal 

contamination of forward observers due to deposition of large fallout particles that were 

resuspended by the blast wave and were redeposited on the ground surface within a few minutes. 

In applying that model, the height above ground over which resuspended material was 

distributed [the parameter H in eq. (3-31)] should be about 10 to 30 m (Kocher et al. 2009). The 

resuspension factor, RF, in that model is a value that applies to all old fallout in the blast-wave 

region. At times after all large particles fell to Earth, dermal contamination due to deposition of 

smaller fallout particles that remained airborne is estimated using a deposition velocity, VD (or 

wind speed, VW). 

4.4 Deposition Velocity

Deposition velocities onto the ground surface for particles of diameter between 0.001 and 

100 m are provided by Sehmel (1984) as function of particle density. Deposition velocities of 

83
material resuspended by human activities (e.g., vehicular traffic, agricultural machines) were 

estimated by Garger et al. (1998) from measurements in areas that experienced fallout of 137Cs 

from the Chernobyl accident; particle diameters in that study ranged from 0.1 to 100 m. 

Deposition velocities onto skin, hair and clothing for particles of diameter less than 10 m in the 

form of aerosols released in an indoor environment were measured by Fogh et al. (1999), as 

described in Section 2.2.3. These three sources indicate that deposition velocities are small over 

the range of particle sizes studied, i.e., between 0.0001 and 1 m s–1 in Sehmel (1984), 0.009 and 

0.06 m s–1 in Garger et al. (1998), and 0.001 and 0.02 m s–1 in Fogh et al. (1999). 

In the studies noted above, the surface onto which deposition occurred was stationary. 

However, individuals who are exposed to airborne particles in outdoor environments often are in 

motion, and deposition onto the human body depends on an individual’s speed of motion relative 

to ambient air (Kochendorfer and Ulberg 1967). A walking speed normally is about 3 mph 

(1.3 m s–1) and may range from 0.1 m s–1 (very slow walk at 0.25 mph) to 5 m s–1 (11 mph; 

running short distances). The lower bound of this range is equivalent to expected settling 

velocities for particles of diameter about 40 m. Larger speeds relative to ambient air are 

possible in other situations, such as riding in the back of a truck. When a person walks for a 

longer period of time (e.g., an hour or more), the average speed varies within a narrower range, 

probably between 0.5 m s–1 (1.1 mph) and 3 m s–1 (6.7 mph). 

Particles with a given settling velocity in still air (e.g., 0.1 m s–1) can impact only the 

non-vertical surfaces of a stationary individual (e.g., top of the head, shoulders). If an individual 

moves horizontally at 1 m s–1, particles will impact the body almost horizontally, thus offering a 

much larger surface area for particle deposition. A higher particle velocity at the body surface 

usually increases the probability of impaction due to particle inertia, which is important for 

particles of diameter greater than 10 m (Kochendorfer and Ulberg 1967; Sehmel 1984). 

For purposes of estimating doses to skin from dermal contamination for individuals in 

motion in a dust cloud, we believe that “deposition” velocities of about 1 m s–1 can be assumed. 

In the absence of wind, a deposition velocity for use in modeling deposition of airborne particles 

onto skin while walking could be represented by a triangular probability distribution with a 

minimum at 0.5 m s–1, mode at 1.0 m s–1 and maximum at 3 m s–1 on the basis of assumptions 

84
described above (Table 4-2). Deposition velocities can be 7 to 14 m s–1 if exposure occurred 

while riding in the back of a truck at 15 to 30 mph. 

If significant winds occurred at the time of exposure, a probability distribution of the 

wind speed described in the following section could be used as a surrogate for the deposition 

velocity, since modeling of wind-driven resuspension (Section 3.3.3) is the same as modeling of 

resuspension by human activities (Section 3.3.2) when the deposition velocity, VD, is replaced by 

the wind speed, VW. 

4.5 Wind Speed 

Ideally, measurements of wind speed would be available at locations and times of 

exposure. In the absence of measurements, a wind speed must be assumed in estimating doses 

from dermal contamination by material resuspended by winds. A long-term average wind speed 

at NTS17 is 4 m s–1, with monthly averages ranging from 3.6 to 5 m s–1. Average winds in the 

Pacific are stronger. At Kwajalein,18 the annual average wind speed is 6 m s–1, with monthly 

averages ranging from 4 to 7.5 m s–1. On Majuro Atoll,19 monthly average wind speeds range 

from 3 to 6 m s–1. 

Data described above indicate that the long-term average wind speed at NTS can be 

represented by a uniform probability distribution between 3 and 5 m s–1 (mean of 4 m s–1). In 

cases of short-term exposures at NTS over periods of a several hours or less, which were 

common, the average wind speed should be more uncertain and could be represented by a 

uniform probability distribution between 2 and 6 m s–1. For exposures on residence islands in 

the Pacific over periods of weeks or months, the long-term average wind speed can be 

represented by a uniform probability distribution between 3 and 7 m s–1 (mean of 5 m s–1). 

 

17 Source: data for Desert Rock-Mercury obtained from Western Regional Climate Center; 

www.wrcc.dri.edu/ htmlfiles/westwind.final.html; accessed September 2005.

18 Source: Western Regional Climate Center; http://www.wrcc.dri.edu/cgi-bin/clilcd.pl?pi40604; accessed 

September 2005.

19 Source: http://www.spc.int/prism/country/mh/stats/Geog/climate.htm; accessed September 2005.

85
4.6 Dose-Rate Factors

The main concern in cases of dermal contamination by radionuclides is exposure of 

radiosensitive tissues in the basal layer of skin to electrons (primarily beta particles). Exposure 

to radionuclides that emit alpha particles also is a potential concern. Dose-rate factors and their 

uncertainties for these two radiation types are discussed separately in the following sections. A 

dose-rate factor is defined as the dose rate per unit concentration of a radionuclide or 

radionuclides on the body surface. 

4.6.1 Dose-Rate Factors for Beta-Emitting Radionuclides

Doses to skin from dermal contamination by beta-emitting radionuclides are estimated 

using published dose-rate factors that apply to radiosensitive tissues in the basal layer of skin at 

depths of about 4 to 10 mg cm–2; the average depth is about 7 mg cm–2 (ICRP 1975; Charles 

1986). A depth of 7 mg cm–2 is about 70 μm at a density of tissue of about 1 g cm–3. The 

appropriate depth depends on the location of interest on the body surface. 

An important challenge in estimating doses from beta-emitting radionuclides in fallout 

from detonation of a nuclear weapon is that fallout contains many radionuclides of widely 

varying half-lives. Since exposure can occur at any time after a detonation, it is impractical to 

estimate doses using radionuclide-specific dose-rate factors that are applied to the concentration 

of each radionuclide. However, as indicated in the following discussions, electron doses to skin 

can be estimated using a nominal dose-rate factor that applies to the activity concentration of all 

beta-emitting radionuclides combined and is largely independent of time after a detonation. 

In this report, doses to skin from beta-emitting radionuclides on the body surface are 

estimated on the basis of a dose-rate factor that applies at a depth of 7 mg cm–2. In estimating 

doses at other depths, the dose-rate factor at 7 mg cm–2 is adjusted upward or downward by a 

factor that accounts for the depth of radiosensitive tissues of skin in the region of interest as: 

DRF DRF SDMF skin cmmg  2  7 (4-4) 

where 

86
 DRFskin = dose-rate factor at assumed depth of radiosensitive tissues for 

radionuclides deposited on skin (rem h–1 per μCi cm–2); 

= dose-rate factor at depth of 7 mg cm–2 (rem h–1 per μCi cm–2); 2 7  cmmg

DRF

 SDMF = skin-depth modification factor (unitless) to account for assumption of 

a nominal depth of radiosensitive tissues of skin in region of interest 

different from 7 mg cm–2 and to account for variability in depth of 

radiosensitive tissues in that region. 

Appropriate values of the dose-rate factor (DRF) at a depth of 7 mg cm–2 and the skin-depth 

modification factor (SDMF) at other depths are discussed in the following two sections. 

4.6.1.1 Nominal Dose-Rate Factor at Depth of 7 mg cm–2

Dose rates to skin from electrons per unit activity concentration of radionuclides on the 

body surface (dose-rate factors, DRF) were calculated by Kocher and Eckerman (1987) for many 

radionuclides of interest on the basis of an assumption that concentrations are uniform. Given 

that the electron range in tissue is less than 2 cm at most energies that occur in radioactive decay, 

it can be assumed that a surface area as small as 15 cm2

 is effectively infinite in extent for the 

purpose of estimating electron dose to skin at depths below the center of a contaminated area. 

Therefore, since dermal contamination by particles from nuclear weapons fallout20 is expected to 

cover areas of skin larger than 15 cm2

 and to be relatively uniform in a given region of the body 

(e.g., face, arms, legs, or back), dose-rate factors for uniform dermal contamination can be 

applied to estimate doses from contamination by fallout. Doses to skin due to single “hot” 

particles are not considered in this report. 

As noted above, it is impractical to estimate electron doses to skin using dose-rate factors 

for specific radionuclides when the contribution of each radionuclide to the total activity 

concentration of all radionuclides combined depends on time after a detonation. A more 

practical approach is to develop a nominal dose-rate factor that represents the dose rate per unit 

activity concentration all radionuclides in fallout combined. 

 

20 This discussion refers to particles in descending fallout and fallout particles resuspended by winds or 

mechanical stresses.

87
Development of a nominal dose-rate factor for all radionuclides in fallout combined is 

facilitated by calculations of the dose-rate factor as a function of electron energy (Kocher and 

Eckerman 1987) shown in Fig. 4-3. Those calculations indicate that the dose-rate factor is 

largely independent of energy in a plateau region where energies are slightly above the minimum 

energy required for an electron to penetrate to the depth of radiosensitive tissues. For example, 

at a depth of 8 mg cm–2, the dose-rate factor is nearly constant at energies above 0.1 MeV. 

Consequently, as indicated in Table 1 of Kocher and Eckerman (1987), dose-rate factors are 

nearly the same for specific radionuclides with an average energy of emitted electrons in the 

plateau region (e.g., above about 0.1 MeV at a depth of 8 mg cm–2). 

On the basis of calculations by Kocher and Eckerman (1987) described above, a nominal 

dose-rate factor can be estimated for all radionuclides in fallout combined that is largely 

independent of the contribution of each radionuclide to the total activity concentration on the 

body surface and, therefore, applies at any time after a detonation. Calculated dose-rate factors 

similar to those in the plateau region in Fig. 4-3, where the dose-rate factor is largely 

independent of energy, were used by Barss (2000) to develop a dose-rate factor at a depth of 

7 mg cm–2 for mixtures of radionuclides in fallout of 9 rem h–1 per Ci cm–2

skin.

21 

The nominal dose-rate factor for all radionuclides in fallout combined at a depth of 

7 mg cm–2 given above is an upper bound. A more realistic estimate would take into account 

that some radionuclides in fallout emit electrons of average energy less than about 0.1 MeV and, 

thus, do not contribute significantly to the electron dose to skin. In addition, calculations by 

Kocher and Eckerman (1987) assume that electrons are emitted in an infinite tissue medium, 

rather than at an air-tissue interface, which results in an overestimate of the contribution to the 

dose from backscattering of electrons that are emitted in directions away from the body surface. 

By considering all fission products (plus activation products 237U and 239Np) that would 

be present at 2 days and 4 years after a detonation (Trabalka and Kocher 2007), we estimated 

that the dose-rate factors for mixtures of radionuclides in fallout at those times are 5.1 and 

6.4 rem h–1 per μCi cm–2, respectively. Thus, accounting for low-energy beta emitters results in 

 

21 This dose-rate factor applies, for example, to the high-energy beta emitters 90Sr and 90Y and is a good 

approximation for other radionuclides with average energies of emitted electrons greater than about 

0.1 MeV. The dose-rate factor for mixtures of radionuclides in fallout estimated by Barss (2000) also 

includes a contribution of about 5% from photons. Such a small contribution can be neglected. 

88
nominal dose-rate factors for all radionuclides in fallout combined at a depth of 7 mg cm–2 that 

are lower by about 40% at times shortly after a detonation and about 30% at much longer times 

than the dose-rate factor of 9 rem h–1 per μCi cm–2 discussed by Barss (2000). 

When backscattering in tissue is assumed, as in the calculations by Kocher and Eckerman 

(1987), backscattered electrons impact the body surface only at locations close to the source, due 

to the short ranges of emitted electrons in tissue, and, therefore, contribute to the dose to 

radiosensitive tissues only at locations of contamination. However, the range of emitted 

electrons in air often is much greater than the dimensions of a source area on the body surface, 

even when the entire body is contaminated. Therefore, when backscattering occurs in air, some 

backscattered electrons either do not impact the body surface at locations close to the source or 

they miss the body entirely. In either case, the contribution to the dose to skin at locations of 

contamination from backscattered electrons is reduced compared with the dose obtained by 

assuming backscattering in tissue. 

Calculations by Cross et al. (1992) indicate that neglect of backscattering in air results in 

overestimates of the dose to radiosensitive tissues of skin when the maximum (endpoint) energy 

of electrons emitted in beta decay of a radionuclide exceeds 0.15 MeV. The factor by which the 

dose is overestimated increases nearly linearly with increasing endpoint energy to about 1.4 at an 

energy of 2 to 3 MeV and then decreases at higher endpoint energies. The maximum backscatter 

factor of about 1.4 applies, for example, to electrons emitted in decay of 90Y. A multiplicative 

correction to the nominal dose-rate factor to account for the effect of backscattering is the 

reciprocal of the backscatter factor calculated by Cross et al. (1992). Thus, we represent an 

uncertain backscatter correction to a nominal dose-rate factor for mixtures of radionuclides in 

fallout by a uniform probability distribution between 0.7 and 1.0. This correction factor is 

assumed to apply at any depth of radiosensitive tissues and in any part of a contaminated region 

of any size, even though Cross et al. (1992) calculated a backscatter correction only at a depth of 

7 mg cm–2 on the axis of a source of area 100 cm2

. 

Sources of uncertainty in calculated dose-rate factors that were considered by Kocher and 

Eckerman (1987) include use of the point-kernel method, use of approximate representations of 

continuous spectra of electrons from beta decay, and uncertainties in energies and intensities of 

electrons emitted by radionuclides. These uncertainties all should be small (about 10% or less). 

89
We represent the combined effect of these uncertainties by a normal probability distribution with 

a 90% CI of (0.9, 1.1). 

Another factor that can affect electron doses to skin from exposure to radioactive 

particles on the body surface is absorption of electrons by the particles. Most particles that are 

retained on skin for a significant period of time have diameters of 50 m or less (Section 2.1). 

At a density of fallout particles at NTS of about 2.7 g cm–3 (the density of fallout particles in the 

Pacific may be lower), a 50-μm particle at NTS provides a maximum shielding equivalent to 

about 14 mg cm–2 of tissue. If 90Y is selected as a representative high-energy beta emitter, an 

additional 14 mg cm–2 of shielding reduces the dose-rate factor by about 40%; this estimate is 

based on interpolation of dose-rate factors for 90Y at different depths in tissue in Table 1 of 

Kocher and Eckerman (1987). A reduction of 40% is a maximum effect at this particle size, 

because some radionuclides would be shielded by only a fraction of the particle diameter and 

radionuclides on the underlying surface (if any) would not be shielded. This reduction could be 

increased to perhaps 50% to take into account that the dose-rate factor for mixtures of 

radionuclides would decrease as the thickness of shielding increases when fewer radionuclides 

would have dose-rate factors in the plateau region of curves in Fig. 4-3. 

We also consider that some particles that are retained on skin should have a diameter 

greater than 50 μm, and that the shielding provided by such particles would be greater than the 

estimate given above. For example, for a 150-μm particle of density 2.7 g cm–3, which is 

equivalent to 40 mg cm–2 of tissue, the reduction in the dose-rate factor at high electron energies 

would be slightly less than a factor of two, and the reduction to account for mixtures of 

radionuclides that emit various average energies of beta particles probably would be greater than 

a factor of two. However, most of the dose to skin is expected to be due to particles of diameter 

less than 50 m, for which the probability of retention on skin is the highest (Section 4.2.1). 

On the basis of the foregoing considerations, we assume that the effect of shielding by 

particles is a reduction of the dose-rate factor for mixtures of radionuclides in fallout by a factor 

that can be represented by a triangular probability distribution with a minimum at 0.5, mode at 

0.8 (i.e., half the maximum reduction due only to shielding by a 50-μm fallout particle), and 

maximum at 1.0. 

90
By applying the probability distributions developed above to represent uncertainties in a 

backscatter correction, dose-rate factors calculated by Kocher and Eckerman (1987), and a 

correction for shielding provided by particles to the estimated dose-rate factor for mixtures of 

radionuclides in fallout at 2 days of 5.1 rem h–1 per μCi cm–2, a nominal dose-rate factor at a 

depth of 7 mg cm–2 for mixtures of radionuclides in 2-day old fallout in rem h–1 per μCi cm–2 can 

be represented by a triangular probability distribution with a minimum at 1.6, mode at 3.2, and 

maximum at 5.4. Similarly, a nominal dose-rate factor for mixtures of radionuclides in 4-year 

old fallout in the same units can be represented by a triangular probability distribution with a 

minimum at 2.0, mode at 4.1, and maximum at 6.8. 

The number of radionuclides and their relative activities in fallout change with time. 

However, given that the dose-rate factors for all radionuclides combined in 2-day and 4-year old 

fallout are similar, it is reasonable to develop a single dose-rate factor that applies at any time 

after a detonation. On the basis of the probability distributions at the two times given above, a 

nominal dose-rate factor at a depth of 7 mg cm–2 for mixtures of radionuclides in fallout in units 

of rem h–1 per μCi cm–2 that applies at any time can be represented by a triangular probability 

distribution with a minimum at 1.6, mode at 3.7, and maximum at 6.8 (Table 4-2). 

4.6.1.2 Skin-Depth Modification Factor

Dose-rate factors for beta-emitting radionuclides discussed in the previous section apply 

at a depth below the body surface of 7 mg cm–2 (70 m), which is considered to be the average 

thickness of the epidermis. However, radiosensitive tissues in the basal layer of skin are located 

at other depths in certain regions of the body. For example, radiosensitive tissues in skin of the 

face are located at an average depth of about 4 mg cm–2 (40 m), while radiosensitive tissues in 

skin of the forearms and lower legs are located at an average depth of about 8 mg cm–2 (80 m) 

(ICRP 1975; Charles 1986; Whitton 1973). The thickness of the epidermis is greatest on the 

palms of the hands and soles of the feet. Those regions also exhibit the largest variation in 

thickness, which ranges from about 60 mg cm–2 (600 m) on horny pads of the palms and soles 

to as low as about 20 mg cm–2 (200 m) in other areas. A thickness of 40 mg cm–2 (400 m) is 

generally accepted as an average in those regions. 

91
The nominal dose-rate factor for all radionuclides in fallout combined at a depth of 

7 mg cm–2 developed in the previous section needs to be adjusted using a skin-depth 

modification factor (SDMF) to estimate doses to skin from dermal contamination in regions of 

the body where radiosensitive tissues are located at a different depth. This adjustment factor is 

developed on the basis of two considerations. The first is the dependence of the dose-rate factor 

(DRF) in the plateau region in Fig. 4-3, where the dose-rate factor is largely independent of 

energy, on the depth of radiosensitive tissues. As the depth increases, the dose-rate factor in the 

plateau region decreases, and vice versa. Second, as the depth of radiosensitive tissues decreases 

(increases), the number of radionuclides with a dose-rate factor in the plateau region may 

increase (decrease), which results in an increase (decrease) in the dose-rate factor for mixtures of 

radionuclides in fallout relative to the nominal dose-rate factor at a depth of 7 mg cm–2. The 

contribution of the second effect to a skin-depth modification factor does not represent a double 

accounting of a similar effect that is incorporated in the probability distribution of the dose-rate 

factor discussed in the previous section, because that adjustment applies at a depth of 7 mg cm–2

where a skin-depth modification factor is not used [eq. (4-4)]. 

The two adjustments that are incorporated in a skin-dose modification factor should be 

positively correlated, given the relationship between the depth of radiosensitive tissues and the 

number of radionuclides with a dose-rate factor in the plateau region in Fig. 4-3 noted above. A 

perfect positive correlation (correlation coefficient of +1.0) between the dose-rate factor in the 

plateau region and the number of radionuclides with a dose-rate factor in that region is assumed. 

If this correlation were not taken into account, the uncertainty in the skin-dose modification 

factor would be underestimated. 

In the following sections, we develop probability distributions of the skin-depth 

modification factor (SDMF) by taking into account the two adjustments to a dose-rate factor 

(DRF) at 7 mg cm–2 and their positive correlation described above and the variability (range) in 

depths of radiosensitive tissues in different regions of the body where the nominal depth is 

assumed to be 4, 8, or 40 mg cm–2. The variability in the depths of radiosensitive tissues 

(thickness of the epidermis) is described by ICRP (1975), Charles (1986), and Whitton (1973). 

92
4.6.1.2.1 Skin-depth modification factor at nominal depth of 4 mg cm–2

In some regions of the body, such as the face, forehead, neck, shoulders, torso, and upper 

legs, radiosensitive tissues in the basal layer of skin are located at an average depth of 4 mg cm–2. 

The minimum depth in those regions is 2 mg cm–2 (ICRP 1975; Charles 1986; Whitton 1973). A 

maximum depth of 7 mg cm–2 is given by ICRP (1975) and Charles (1986), whereas Whitton 

(1973; Figs. 1 and 2) reports a maximum depth of about 10 mg cm–2. 

We first consider the contribution to the skin-depth modification factor (SDMF) that 

accounts for the dependence of the dose-rate factor in the plateau region of Fig. 4-3 on the depth 

of radiosensitive tissues. Dose-rate factors as a function of energy in Fig. 4-3 and dose-rate 

factors for specific radionuclides in Table 1 of Kocher and Eckerman (1987) indicate that a 

contribution to SDMF of 1.3 describes the increase in dose-rate factor in the plateau region when 

the depth in tissue decreases from 7 to 4 mg cm–2. By assuming that the maximum depth in 

tissue is about 10 mg cm–2, as reported by Whitton (1973), extrapolation of dose-rate factors for 

higher-energy beta emitters at depths of 4 and 8 mg cm–2 gives a minimum of the contribution to 

SDMF of 0.8. At an assumed minimum depth in tissue of 2 mg cm–2, a maximum of the 

contribution to SDMF due to the increase in dose-rate factor in the plateau region of 1.4 is 

obtained by extrapolation of dose-rate factors for high-energy beta emitters at depths of 4 and 

8 mg cm–2 in Table 1 of Kocher and Eckerman (1987). 

On the basis of estimates given above, the contribution to the skin-depth modification 

factor (SDMF) that applies to a nominal dose-rate factor for higher-energy beta emitters—i.e., to 

the dose-rate factor in the plateau region of curves in Fig. 4-3—at a depth of 7 mg cm–2 to obtain 

a nominal dose-rate factor at a depth of 4 mg cm–2 can be represented by a triangular probability 

distribution with a minimum at 0.8, mode at 1.3, and maximum at 1.4. 

Data in Table 1 of Kocher and Eckerman (1987) indicate that few radionuclides show a 

large increase in dose-rate factor as the depth of radiosensitive tissues decreases from 7 to 

4 mg cm–2; i.e., few radionuclides with a dose-rate factor below the plateau region in Fig. 4-3 at a 

depth of 7 mg cm–2 have a dose-rate factor in the plateau region at a depth of 4 mg cm–2. 

Therefore, there should be little increase in the dose-rate factor for mixtures of radionuclides in 

fallout due to an increase in the number of radionuclides that contribute significantly to the dose 

93
as the depth decreases from 7 to 4 mg cm–2 or even to 2 mg cm–2. We assume that this increase 

can be represented by a uniform probability distribution between 1.0 and 1.2. The effect of 

increasing the depth to as much as 10 mg cm–2, which could reduce the number of radionuclides 

that contribute significantly to the dose, perhaps would be somewhat less and is assumed to be 

represented by a uniform probability distribution between 0.9 and 1.0. Thus, in this case, we 

assume that the contribution to the skin-dose modification factor (SDMF) to account for a 

difference in the number of radionuclides in fallout with a dose-rate factor in the plateau region 

can be represented by a uniform probability distribution between 0.9 and 1.2. 

By combining the probability distributions of the two contributions described above and 

assuming that they are perfectly positively correlated, the skin-depth modification factor (SDMF) 

at a nominal depth of 4 mg cm–2 can be represented by a triangular probability distribution with a 

minimum at 0.7, mode at 1.3, and maximum at 1.7 (Table 4-2). The assumed correlation 

between the two contributions has only a small effect on the resulting probability distribution of 

the skin-depth modification factor compared with an assumption of no correlation. 

4.6.1.2.2 Skin-depth modification factor at nominal depth of 8 mg cm–2

In some regions of the body, such as the forearms and lower legs, radiosensitive tissues in 

the basal layer of skin are located at an average depth of 8 mg cm–2 (80 μm). Data summarized 

by ICRP (1975) indicate that the thickness of the epidermis is 50–65 m on the back of the 

forearms, 34–65 m on the front of the forearms, and 40–80 m on the lower legs. Data in 

Figs. 4 and 5 of Whitton (1973) indicate that the maximum depth of the basal layer in these 

regions is 16 mg cm–2 (160 m). The minimum depth indicated in Figs. 4 and 5 of Whitton 

(1973) is 4 mg cm–2, which is in reasonable agreement with the lowest value of 3.4 mg cm–2

(34 m) reported by ICRP (1975). 

We assume that 8 mg cm–2 is a reasonable central estimate of the depth of radiosensitive 

tissues in regions of the body where the nominal value is assumed to apply, and that the depth in 

those regions ranges from 4 to 16 mg cm–2. Using data in Table 1 of Kocher and Eckerman 

(1987) and Fig. 4-3, the approach to estimating a skin-depth modification factor (SDMF) 

described in the previous section leads to the following results at a nominal depth of 8 mg cm–2: 

94
 The contribution to the skin-depth modification factor that accounts for the variation in 

the dose-rate factor for higher-energy beta emitters in the plateau region of Fig. 4-3 as the 

depth of radiosensitive tissues ranges from 4 to 16 mg cm–2, relative to the dose-rate 

factor in the plateau region at a depth of 7 mg cm–2, can be represented by a triangular 

probability distribution with a minimum at 0.7, mode at 0.95, and maximum at 1.3. 

 The contribution to the skin-depth modification factor that accounts for the variation in 

the number of radionuclides with a dose-rate factor in the plateau region of Fig. 4-3 as the 

depth of radiosensitive tissues ranges from 4 to 16 mg cm–2, relative to the number of 

radionuclides with a dose-rate factor in the plateau region at a depth of 7 mg cm–2, can be 

represented by a uniform probability distribution between 0.8 and 1.1. 

 By combining the probability distributions of the two contributions described above, 

assuming that they are perfectly positively correlated, the skin-depth modification factor 

(SDMF) at a nominal depth of 8 mg cm–2 can be represented by a triangular probability 

distribution with a minimum at 0.5, mode at 0.9, and maximum at 1.5 (Table 4-2). 

4.6.1.2.3 Skin-depth modification factor at nominal depth of 40 mg cm–2

In some regions of the body, such as the palms of the hands and soles of the feet, 

radiosensitive tissues in the basal layer of skin are located at an average depth of 40 mg cm–2. 

The horny pads of the palms and soles can have a thickness of about 60 mg cm–2, whereas the 

thickness of the epidermis in other areas can be as low as 16 mg cm–2 (Whitton 1973; Fig. 6). 

Dermal contamination of these regions by descending or resuspended fallout may not be as 

important as contamination by other means, given that handling of contaminated soil or objects 

can transfer substantial amounts of material to the palms of the hands and the presence of soil 

particles in boots can lead to significant contamination of soles of the feet. 

We assume that 40 mg cm–2 is a reasonable central estimate of the depth of radiosensitive 

tissues in regions of the body where the nominal value is assumed to apply, and that the depth in 

those regions ranges from 16 to 60 mg cm–2. Using data in Table 1 of Kocher and Eckerman 

(1987) and Fig. 4-3, the approach to estimating a skin-depth modification factor (SDMF) 

described in Section 4.6.1.2.1 leads to the following results at a nominal depth of 40 mg cm–2: 

95
 The contribution to the skin-depth modification factor that accounts for the variation in 

the dose-rate factor for higher-energy beta emitters in the plateau region of Fig. 4-3 as the 

depth of radiosensitive tissues ranges from 16 to 60 mg cm–2, relative to the dose-rate 

factor in the plateau region at a depth of 7 mg cm–2, can be represented by a triangular 

probability distribution with a minimum at 0.3, mode at 0.5, and maximum at 0.7. 

 The contribution to the skin-depth modification factor that accounts for the variation in 

the number of radionuclides with a dose-rate factor in the plateau region of Fig. 4-3 as the 

depth of radiosensitive tissues ranges from 16 to 60 mg cm–2, relative to the number of 

radionuclides with a dose-rate factor in the plateau region at a depth of 7 mg cm–2, can be 

represented by a uniform probability distribution between 0.3 and 0.8. 

 By combining the probability distributions of the two contributions described above, 

assuming that they are perfectly positively correlated, the skin-depth modification factor 

(SDMF) at a nominal depth of 40 mg cm–2 can be represented by a triangular probability 

distribution with a minimum at 0.08, mode at 0.3, and maximum at 0.6 (Table 4-2). 

4.6.2 Dose-Rate Factors for Alpha-Emitting Radionuclides

In contrast to beta-emitting radionuclides, only a few alpha-emitting radionuclides in 

fallout from a nuclear weapon detonation are potentially important contributors to doses to skin 

from dermal contamination. Therefore, it is practical to use radionuclide-specific dose-rate 

factors for alpha emitters, rather than an approach that would be based on development of 

nominal dose-rate factors that apply to all alpha emitters in fallout combined.22

 

22 An important consideration that discourages an approach to estimating doses to skin based on 

development of nominal dose-rate factors that apply to all alpha-emitting radionuclides in fallout 

combined is the much stronger energy dependence of dose-rate factors for alpha particles at a given depth 

in tissue compared with the energy dependence for electrons. The stronger energy dependence, and the 

resulting lack of a plateau region in the dose-rate factor as a function of energy similar to the plateau 

regions indicated in Fig. 4-3, is a consequence of the much shorter ranges of alpha particles in tissue and 

similarities between those ranges and the depths of radiosensitive cells in the basal layer. As indicated by 

radionuclide-specific dose-rate factors given in Table 4-4, dose-rate factors for mixtures of alpha emitters 

in fallout generally would not be well represented by a single nominal value. 

96
The model used in this report to calculate dose-rate factors for alpha-emitting 

radionuclides on the body surface was developed by Eatough (1997). The equivalent dose23 as a 

function of depth x in tissue per unit concentration of a radionuclide on the body surface is 

calculated by numerical integration of stopping powers (energy loss per unit distance of travel) 

of emitted alpha particles. Eatough (1997) represented the calculated depth-dose distribution by 

a function containing exponential and linear terms of the form: 

])/(1[8.2)( /13e Rx

R

E xDRF Rx

skin   (4-5) 

where 

DRFskin = dose-rate factor at assumed depth of radiosensitive tissues for radionuclide 

deposited on skin (μSv s–1 per Bq cm–2);24

x = depth in tissue (mg cm–2); 

E = energy of emitted alpha particle (MeV); 

 R = range of emitted alpha particle in tissue (mg cm–2). 

The exponential term in this model is negligible at depths greater than about 1 mg cm–2. 

Equation (4-5) gives the dose-rate factor at a fixed depth x below the body surface (e.g., 

at the base of the epidermis where the basal layer begins). However, the location of 

radiosensitive tissues within the finite thickness of the basal layer is uncertain and, as described 

in Section 4.6.1.2, the thickness of the epidermis in particular regions of the body is variable. 

Eatough (1997) addressed the uncertainty in the location of radiosensitive tissues by 

assuming that they are uniformly distributed in a basal layer of thickness 0.88 mg cm–2 in all 

regions of the body. The mean dose to the basal layer for a given thickness of the epidermis then 

can be estimated by integrating eq. (4-5) over the assumed thickness of the basal layer. 

Eatough (1997) addressed the more important variability in the thickness of the epidermis 

in particular regions of the body on the basis of various measurements of epidermal thickness 

 

23 Equivalent doses are calculated by assuming a radiation weighting factor (wR) of 20 for alpha particles. 

The assumed wR is appropriate when induction of skin cancer is the health effect of concern but would be 

result in an overestimate of the biologically significant dose when deterministic effects are of concern. 

24 The dose-rate factor in this equation and in eq. (4-6) is expressed in units used by Eatough (1997). To 

convert to units of rem h–1 per μCi cm–2 used in this report, dose-rate factors calculated using these 

equations should be multiplied by 1.33 × 104

. 

97
reported in the literature. These data were used to define step-function distributions of epidermal 

thickness in particular regions of the body, which then were represented by smooth functions to 

facilitate estimation of a mean dose to the basal layer in those regions. Using this approach, 

Eatough (1997) calculated mean doses to the basal layer as  , where D(x) is given 

by eq. (4-5) and P(x) is the assumed representation of the distribution of epidermal thickness in a 

region of interest. The resulting mean dose-rate factor in the basal layer is given by: 

R

xxPxD

0 ( d)()

0 )]2()2([8.2 2 fefx R

E DRF f

skin  (4-6) 

 f = [q – (R + t)]/x0 

where t is half the thickness of the basal layer (0.44 mg cm–2), x0 and q are parameters in the 

smooth function that was fit to the step-function distributions of epidermal thickness in specific 

regions of the body, R must be greater than q – t, and q – t must be greater than 1 mg cm–2. 

Values of q and x0 in eq. (4-6) depend on the particular source of data used to define 

distributions of epidermal thickness in specific regions of the body. When the more 

comprehensive data reported by Whitton (1973) were used, the following values of these 

parameters in different regions were obtained: 

 Back of hand: q = 5, x0 = 2.4; 

 Arms and legs: q = 3.1, x0 = 2.0; 

 Trunk: q = 2.0, x0 = 1.35; 

 Face: q = 1.4, x0 = 2.1. 

On the basis of the model and parameter values described above, the mean dose to the 

basal layer generally is higher than the dose at the base of the epidermis, due to the increase in 

stopping power as an alpha particle that can penetrate through the basal layer loses energy in 

traversing that layer. 

Dose-rate factors for selected alpha-emitting radionuclides of potential importance in 

fallout from a nuclear weapon that we calculated using the model in eq. (4-6) and values of q and 

x0 listed above are given in Table 4-4. The mean alpha energy per decay of each radionuclide 

was obtained from Kocher (1980), and the range in tissue was obtained by linear interpolation of 

98
ranges in “muscle-equivalent liquid (with sucrose)” tabulated by ICRU (1993). The average 

thickness of the epidermis is about 6.6 mg cm–2 on the arms and legs, 4.7 mg cm–2 on the trunk, 

5.5 mg cm–2 on the face, and 9.3 mg cm–2 on the back of the hands. Dose-rate factors in other 

regions can be obtained on the basis of a similarity in the thickness of the epidermis. 

The model developed by Eatough (1997) and the dose-rate factors in Table 4-4 do not 

account for absorption of alpha particles by radioactive particles on the body surface. The range 

of a 6-MeV alpha particle in a fallout particle at NTS with a density of 2.7 g cm–3 is about 30 μm 

(ICRU 1993); this energy is about the same as the highest energy of alpha particles emitted by 

radionuclides listed in Table 4-4. For 239Pu, which is the most important alpha emitter in fallout, 

the energy of alpha particles is about 5.2 MeV, and the range in fallout particles at NTS is about 

20 μm. A range of 20 to 30 μm is roughly comparable to diameters of most fallout particles that 

are retained on the body surface, which are about 50 μm or less (Section 4.2.1). 

In developing a representation of the effect of shielding by fallout particles on reducing 

doses from alpha-emitting radionuclides on the body surface, the following factors were 

considered: (1) radionuclides of interest in fallout generally are assumed to be isotopes of 

refractory elements that should be preferentially distributed in the volume of particles (Hicks 

1982; Section IV.C.2.1.2 of NRC 2003); (2) alpha particles do not need to be fully absorbed in 

fallout particles for the dose to the basal layer of skin to be reduced to zero; (3) the shielding 

required to reduce the dose to zero depends on the thickness of the epidermis; and (4) particles of 

all sizes up to about 50 μm would be retained on skin. Data on ranges of alpha particles in 

fallout particles and tissue (ICRU 1993) indicate that shielding by fallout particles could be 

minimal in cases of deposition of the smallest particles in regions of the body where the 

epidermis is relatively thin, but shielding could be quite effective in reducing doses in regions 

where the epidermis is relatively thick. Rather than developing probability distributions of 

shielding factors for specific regions of the body with different thicknesses of the epidermis, 

which is difficult to justify when shapes of fallout particles are irregular and distributions of 

alpha-emitting radionuclides in fallout particles are uncertain, we define a single probability 

distribution that would apply in any region of the body. 

On the basis of the considerations described above, we assume that the effect of shielding 

by fallout particles is a reduction of dose-rate factors for alpha-emitting radionuclides given in 

99
Table 4-4 by a multiplicative factor that is represented by a log-uniform probability distribution 

with a minimum at 0.05 and maximum at 1.0. The mean and median of this distribution are 

about 0.3 and 0.2, respectively; i.e., on average, shielding by fallout particles is assumed to 

reduce doses from dermal contamination by alpha-emitting radionuclides by a factor of about 

three. The assumed effect of shielding for alpha particles is substantially greater than the effect 

of shielding for electrons discussed in Section 4.6.1.1, which is an expected result. Given the 

dependence of dose-rate factors on the thickness of the epidermis, we believe that the assumed 

probability distribution of the shielding factor should underestimate the effect of shielding by 

fallout particles in reducing doses in many regions of the body. 

When alpha particles emitted by a radionuclide are sufficiently energetic to irradiate the 

entire thickness of the basal layer, the dose-rate factor is much higher than the dose-rate factor 

for a beta-emitting radionuclide; the increase is about three orders of magnitude or more in some 

cases. The much higher dose-rate factors for alpha emitters are due to a combination of the 

much shorter range (higher stopping power) of alpha particles in tissue, the assumed radiation 

weighting factor (wR) of 20 for alpha particles, and the higher energy of emitted alpha particles 

compared with average beta energies. Thus, relatively low activity concentrations of alpha 

emitters on the body surface, compared with concentrations of beta emitters, can result in 

relatively high doses to the basal layer.25

As discussed in Section 4.6.1.2, there are regions of the body, such as the palms of the 

hands and soles of the feet, where the average thickness of the epidermis is about 40 mg cm–2. 

Alpha particles emitted by radionuclides are not sufficiently energetic to penetrate the epidermis 

in those regions. 

Uncertainties in dose-rate factors for alpha-emitting radionuclides in Table 4-4 are 

difficult to assess on the basis of available information. The sensitivity of the dose-rate factor for 

a given radionuclide to the assumed thickness of the epidermis, as indicated by comparisons of 

 

25 Since data on concentrations of plutonium in fallout are classified, we could not investigate the 

potential importance of doses to skin from dermal contamination by alpha-emitting radionuclides in 

fallout compared with doses from beta emitters. At times shortly after a detonation when concentrations 

of shorter-lived beta emitters in fallout are high, calculations performed by SAIC (personal 

communication from J. Stiver) indicated that doses from alpha emitters should be unimportant. Given the 

long half-lives of the important isotopes of plutonium, the ratio of the dose to skin from alpha emitters to 

the dose from beta emitters should increase as the time after detonation increases to several years. 

100
dose-rate factors for higher-energy alpha emitters on the arms and legs and on the trunk, suggests 

that the uncertainty is substantial. We believe that an uncertainty of a factor of three is 

reasonable. This uncertainty can be represented by a multiplicative factor in the form of a 

lognormal probability distribution with a GM at 1.0 and 90% CI of (0.33, 3).26

4.7 Efficiency of Showering 

In Section 3.5, models to estimate dose to skin from exposure to radionuclides on the 

body surface were developed that account for incomplete removal of contamination by 

showering or washing. The effect of inefficient showering is represented by two parameters that 

are assumed to describe independent processes for removal of contamination from skin. The 

first parameter, denoted by β, describes the fraction of contamination that is removed by 

exfoliation of skin cells while showering. This parameter is assumed to be the same in each 

shower, and exfoliation of skin cells by other processes (i.e., between showers) is assumed to be 

taken into account implicitly. The second parameter, denoted by γj, describes the fraction of the 

contamination that is removed by washing during the jth shower after a deposition on skin. 

Removal by washing is assumed to be less efficient in each of the first few showers, as residual 

contamination becomes more embedded in skin folds and pores. 

By assuming that an individual showers once per day, the fraction of the contamination 

on skin that is removed during the jth shower is estimated as (γj + β). The fraction of the 

contamination on skin at the time of the jth shower that remains after that shower, denoted by αj, 

then is estimated as αj = 1 – (γj + β). The parameter αj applies to the amount of contamination on 

skin at the time of the jth shower, not the amount at the time of the first shower after deposition 

on skin occurs. 

 

26 An uncertainty in data used to develop the radiation weighting factor (wR) of 20 for alpha particles is 

not taken into account in the assumed uncertainty in dose-rate factors for alpha-emitting radionuclides. 

Uncertainty in the biological effectiveness of alpha particles in inducing cancer in humans relative to 

high-energy photons is taken into account in the probability distribution of the radiation effectiveness 

factor (REF) for alpha particles that is incorporated in the computer code that calculates the probability of 

causation/assigned share (PC/AS) of a diagnosed cancer in an individual associated with a given alpha 

dose to a specific organ or tissue (Land et al. 2003; Kocher et al. 2008). 

101
Recommended values of the parameters β and αj and their uncertainties are discussed in 

the following sections. 

4.7.1 Removal of Radionuclides from Skin by Exfoliation of Skin Cells

Limited data on removal times for cells in the epidermis reported in ICRP Publication 23 

(ICRP 1975) are given in Appendix D.2.1. On the basis of those data, we assume the following 

nominal turnover times of skin cells by exfoliation: 

 Upper limbs, 20 days; 

 Lower limbs, 30 days; 

 Abdomen, 40 days; 

 Scalp, 120 days. 

The cell turnover time on the abdomen is assumed to apply in all regions of the trunk. 

By assuming that an individual showers once each day, the fraction of the activity of 

radionuclides on skin that is removed by exfoliation of skin cells in each shower, β, is 

numerically equal to the reciprocal of the turnover time for skin cells in days. As noted above, β

also takes into account exfoliation of skin cells between showers. When the same fraction 

removed is assumed to apply to the amount of contamination present on skin at the time of each 

shower, some contamination is assumed to remain on skin after all cells that were present at the 

time of deposition are removed by exfoliation. 

Given the paucity of data on ranges of turnover times for skin cells (Appendix D.2.1), 

assumptions about nominal values of the fraction of contamination removed by exfoliation of 

skin cells in each daily shower, β, and their uncertainties are largely a matter of judgment. We 

assume that the most likely value of this parameter in any region of the body is numerically 

equal to the reciprocal of the nominal turnover time for skin cells in that region given above, and 

that the variation from the most likely value should be no more than 50%. In each region of the 

body specified above, we represent the assumed uncertainty in the parameter β by a symmetrical 

triangular probability distribution with a mode at the assumed nominal value and minimum and 

maximum values that differ from the nominal value by 50%. The nominal (deterministic) values 

and assumed probability distributions of the parameter β are given in Table 4-5. 

102
4.7.2 Removal of Radionuclides from Skin by Showering

Data on the efficiency of washing in removing contamination from skin obtained from 

several studies are presented and discussed in Appendix D.2.2. Estimates of the fraction of 

contamination removed by washing in the jth shower, γj, used in modeling the effect of 

inefficient showering that were obtained from data reported by Boeniger (2006), Sharp and 

Chapman (1957), and Friedman (1958) are given in Tables D-2, D-4, and D-7, respectively. 

Additional data reported by Sharp and Chapman (1957) are summarized in Table D-5, and data 

reported by Fogh et al. (1999) are discussed in Appendix D.2.2.6. 

None of the studies reviewed in Appendix D.2.2 appear to provide definitive estimates of 

the fraction of contamination removed by washing in the jth shower, γj, for use in applying 

models developed in Section 3.5 to estimate doses to skin for military participants at atmospheric 

nuclear tests. Data on native Marshallese and military personnel who were exposed to fallout 

from Operation CASTLE, Shot BRAVO in the Pacific reported by Sharp and Chapman (1957) 

are potentially the most relevant. However, external exposure rates at the body surface, rather 

than levels of contamination on skin, were measured in that study, and the measurements, 

especially those after the first shower, probably included significant contributions from internally 

deposited radionuclides. Concerns about use of data obtained from other studies include that 

(1) particle sizes may have been substantially smaller than typical particle sizes in contamination 

on skin of military personnel, (2) methods of removal of contamination from skin, such as use of 

wipes on dry skin, may not have resembled removal by normal washing, or (3) efforts at removal 

of contamination may have been more vigorous than in a typical shower. Given the limitations 

in available data, judgment is required in estimating nominal values of γj and their uncertainties, 

especially in showers after the first (j ≥ 2) when little of the initial contamination may remain on 

skin and only a small fraction of the remaining contamination may be removed by washing. 

For purposes of estimating dose to skin of military personnel, we define two sets of 

values of the parameter γj and their uncertainties. The first set would be used when normal 

showering is assumed and no special effort was made to remove radioactive contamination. This 

set is intended to apply, for example, to military personnel on residence islands in the Pacific 

who may have been exposed routinely to previously deposited fallout that was resuspended by 

103
winds and normal human activities. The second set would be used when significant 

contamination of skin is known or strongly suspected, such as in cases of exposure to descending 

fallout on ships or on land in the Pacific, and there may have been special efforts (e.g., unusually 

vigorous scrubbing) to remove contamination by showering. Deliberate attempts at removal of 

contamination are assumed to be more efficient than normal showering. 

Two additional assumptions are used in defining removal fractions of contamination by 

washing and their uncertainties in the two cases of normal and highly efficient showering 

described above. First, since available data do not permit distinctions in values of γj beyond the 

third shower, γj is assumed to be the same for j ≥ 4. Second, we assume that there is no 

difference in removal fractions beyond the third shower in the two cases. That is, even when 

significant contamination of skin is known or strongly suspected, we assume that special efforts 

to remove contamination by showering would no longer be undertaken when most of the 

contamination has already been removed. Neither assumption has a pronounced effect on 

estimated doses to skin when, in each of the two cases, most of the contamination is assumed to 

be removed in the first three showers. 

As in representing uncertainties in removal fractions of contamination by exfoliation of 

skin cells in the previous section, uncertainties in removal fractions by washing, γj, are 

represented by symmetrical triangular probability distributions. The nominal (deterministic) 

values and assumed probability distributions for the two cases of normal showering and highly 

efficient showering in a deliberate effort to remove contamination are given in Table 4-5. In 

each of the first four showers, washing is assumed to be increasingly less efficient in removing 

contamination in either case and the uncertainty in the efficiency of showering is assumed to 

increase. We also note that since the maximum and minimum values of a triangular probability 

distribution are never sampled when Monte Carlo methods are used to propagate uncertainty, the 

removal fraction in the first shower (γ1) when showering is assumed to be highly efficient would 

always be less than 1.0. 

An important consideration in applying uncertain removal fractions by washing, γj, in 

Table 4-5 is the extent to which the removal fraction is correlated from one shower to the next. 

A strong correlation seems reasonable when it is unlikely that an individual’s showering habits 

or the ability of an individual’s skin to retain contamination would change significantly from one 

104
shower to the next. Although the correlation presumably is not perfect in reality, a full 

correlation between the removal fraction in one shower and the next (correlation coefficient of 

+1.0) could be justified on the grounds that (1) data on removal of contamination by showering 

are limited and (2) the uncertainty in the dose to skin due to uncertainty in the efficiency of 

showering in removing contamination would not be underestimated. 

There also could be a positive correlation between the fraction of contamination removed 

by showering, γj, and fraction removed by exfoliation of skin cells, β. Such a correlation would 

take into account that both removal fractions should be higher in more vigorous showers and 

lower in less vigorous showers. However, a correlation between the two removal fractions is not 

included in our analysis, on the grounds that β also is intended to take into account removal of 

contamination by exfoliation of skin cells between showers, which would be unrelated to 

exfoliation by showering, and the relative importance of exfoliation while showering and 

between showers is unknown. Although it would be reasonable to assume a partial positive 

correlation between the two removal fractions, the effect on the uncertainty in an estimate of the 

effect of inefficient showering on doses to skin should be small compared with the uncertainty 

when the two removal fractions are assumed to be uncorrelated. 

4.7.3 Calculations to Investigate Effects of Inefficient Showering

When a single shower does not remove all contamination on the body surface, the dose to 

skin after the first shower, Dsh, due to residual contamination from a single deposition event can 

be calculated using eq. (3-35) if deposition is acute (e.g., exposure to descending fallout) or 

eq. (3-37) if deposition is continuous (e.g., exposure to fallout resuspended by winds). Those 

equations have identical structures and give Dsh for a known activity concentration of 

radionuclides on skin at the time a deposition event ceased. For an acute deposition, the entire 

activity concentration on skin Cskin(T0) is assumed to be deposited at time T0 after a detonation, 

whereas for a continuous deposition, the activity concentration on skin increases from zero at 

time T0 and to a value Cskin(Tdep) at the time Tdep when deposition ceased. 

This section presents results of calculations to investigate the effect of variations in 

model parameters on Dsh and its importance relative to the dose to the time of the first shower, 

D1. A unit activity concentration of radionuclides in fallout on the body surface at the time a 

105
deposition event ceased was assumed in all calculations, and the effect of varying the following 

parameters was investigated: (1) the time after a detonation when deposition ceased (T0 for an 

acute deposition or Tdep for a continuous deposition), (2) the interval between the time deposition 

ceased and the time of the first shower (Tpost), which is referred to in these discussions as the 

time to the first shower, (3) removal fractions of radionuclides by washing in the first and 

subsequent showers (j), and (4) the removal fraction of radionuclides by exfoliation of skin cells 

(). All results were obtained using eq. (3-35) or (3-37), which apply to mixtures of 

radionuclides in fallout. The number of showers (N) was assumed to be 120. 

Results of calculations shown in Fig. 4-4 illustrate the dependence of the dose to skin 

after the first shower (Dsh) on the time after a detonation when deposition on skin ceased (T0) in 

the range from 2 hours to 4 years, the time to the first shower (ΔTpost) in the range from 1 to 

24 hours, and the efficiency of showering. All calculations assumed deposition on the trunk and 

deterministic values of removal fractions by exfoliation of skin cells (β) and by normal or highly 

efficient showering (γj) given in Table 4-5. These results indicate the following: 

 Dsh increases with increasing time after a detonation when deposition ceased (T0). This 

effect, which is most pronounced at times T0 of 6 months or less, is a consequence of the 

relatively rapid rate of decrease in the activity of all radionuclides in fallout at times 

shortly after a detonation and the increasingly slower rates of decrease at longer times. 

 When deposition on skin ceases at 2 hours after a detonation, Dsh decreases by a factor of 

about three as the time to the first shower (ΔTpost) increases from 1 to 24 hours. 

However, the dependence of Dsh on ΔTpost is less at longer times after a detonation, and 

there is very little dependence at times T0 beyond about 30 days. These effects also are a 

consequence of the dependence of the rate of decrease in the activity of all radionuclides 

in fallout on time after a detonation. 

 An assumption of highly efficient showering reduces Dsh by a factor of about 3 to 4 

compared with an assumption of normal showering; this reduction is nearly independent 

of the time after a detonation when deposition ceased (T0) and the time to the first 

shower (ΔTpost). The reduction in doses after the first shower is mainly the consequence 

of an assumption that the activity of radionuclides that remains on skin after the first 

106
three showers when normal showering is assumed is about twice the activity that remains 

when highly efficient showering is assumed. 

The dependence of the dose after the first shower, Dsh, on the removal fraction of 

radionuclides by exfoliation of skin cells (β), which is assumed to depend on the region of the 

body of interest, is illustrated in Fig. 4-5. At a time to the first shower (ΔTpost) of 6 hours, a 

decrease in β by a factor of about six, as indicated in Table 4-5, results in an increase in Dsh that 

ranges from less than a factor of two at times shortly after a detonation when deposition on skin 

ceased (T0) to a factor of about three at longer times. Removal by exfoliation is important 

compared with removal by showering only after the first few showers. 

The importance of the dose after the first shower, Dsh, relative to the dose to the time of 

the first shower, D1, is illustrated in Figs. 4-6, 4-7, and 4-8. The importance of Dsh relative to D1

depends mainly on three factors: (1) the efficiency of showering, which affects only Dsh but not 

D1; (2) the time to the first shower, ΔTpost; and (3) the time after a detonation when deposition on 

skin ceased, T0. If showering is less efficient in removing contamination from skin, the 

importance of Dsh relative to D1 increases. 

Results in Figs. 4-6 and 4-7 illustrate how the importance of the dose after the first 

shower, Dsh, relative to the dose before the first shower, D1, depends on the time to the first 

shower, ΔTpost, for times after a detonation when deposition on skin ceased, T0, of 2 hours and 

6 months, respectively. These results indicate that Dsh is small compared with D1 only if T0 is 

short; at longer times T0, Dsh is much larger than D1. These results also show that D1 depends on 

the time to the first shower, ΔTpost, for any value of T0, whereas Dsh changes significantly with an 

increase in ΔTpost only at shorter times after a detonation. For any value of T0, the importance of 

Dsh relative to D1 increases with decreasing ΔTpost. Differences in these results at times after a 

detonation when deposition on skin ceased of 2 hours and 6 months also are a consequence of 

the dependence of the rate of decrease of the activity of all radionuclides in fallout combined on 

time after a detonation. 

In equations presented in Section 3.5 and in results shown in Figs. 4-6 and 4-7, D1

represents the dose from the time deposition on skin ceased until the time of the first shower. 

This dose, which is denoted by Dpost in equations to estimate doses due to resuspension of 

previously deposited fallout by human activities in Section 3.3.2, is the only dose received before 

107
the first shower when deposition is modeled as an acute event. However, when a deposition 

event is modeled as a continuous process, an additional dose Ddep is received during the period of 

deposition, as indicated in eq. (3-36) in Section 3.5.3. Figure 4-8 shows results of calculations 

that are the same as those in Fig. 4-7, except continuous deposition onto skin for a period of 

4 hours, resulting in an additional dose Ddep before the time of the first shower, is assumed. A 

comparison of results in Figs. 4-7 and 4-8 indicates that the main effect of the additional dose 

Ddep in this case is to increase the dose to the time of the first shower, with the largest increases 

occurring at times to the first shower, ΔTpost, of about 6 h or less. The ratio of the dose after the 

first shower, Dsh, to the dose before the first shower is reduced accordingly. 

Results of example calculations of uncertainties in the dose to skin after the first shower, 

Dsh, assuming deposition on the trunk and a time to the first shower, ΔTpost, of 6 hours, are shown 

in Fig. 4-9. For a unit activity concentration of radionuclides in fallout on skin and assuming 

that the time after a detonation when deposition on skin ceased (T0) and the times of showers are 

specified without uncertainty, the uncertainty in Dsh is determined by uncertainties in removal 

fractions of radionuclides by washing (γj) and exfoliation of skin cells (β) and the uncertainty in 

the dose-rate factor. Uncertainties in Dsh increase slightly as the time T0 increases and are 

smaller for normal showering than for highly efficient showering. The latter effect is a 

consequence of the assumption indicated in Table 4-5 that the uncertainty in the fraction of the 

activity of radionuclides that remains on skin after each shower, j = 1 – (j +  is somewhat 

smaller for normal showering than for highly efficient showering. The dominant source of 

uncertainty in Dsh is the uncertainty in the fraction removed by washing, γj. 

In calculating probability distributions of Dsh using random sampling from probability 

distributions of model parameters, it is important to recognize that when probability distributions 

in Table 4-5 are assumed, the sum of sampled values of γ1 (the removal fraction by washing in 

the first shower) and β (the removal fraction by exfoliation of skin cells) could be greater than 

1.0, which would result in a negative value of the fraction of the activity of radionuclides that 

remains on the body surface after the first shower, α1 = 1 – (γ1 + β). In such cases, which would 

be most common when highly efficient showering is assumed, α1 should be set to zero. When 

probability distributions in Table 4-5 are assumed, negative values of αj would not be generated 

by random sampling for any shower after the first. 

108
4.8 Additional Discussions 

The previous sections have discussed an approach to estimating doses to skin from 

deposition of airborne radioactive fallout particles on bare skin. Deposition on skin under 

clothing also can occur by circulation of contaminated air under clothing. However, clothing 

acts as a filter that allows fewer particles to impact skin over much of the body. Filtration by 

clothing presumably depends on the type and thickness of clothing. Filtration probably is 

efficient for medium and large particles but not so efficient for very small particles. If we 

assume that clothing was worn loosely, which probably was the case in the warm environment of 

the Pacific, it would be reasonable to calculate doses to skin by ignoring filtration by clothing. 

At NTS, many veterans participated in simulated war exercises while wearing combat uniforms. 

In these cases, it is likely that only a fraction of fallout particles incident on an individual 

penetrated through clothing to impact skin. However, we are not aware of any information about 

the magnitude of such an effect. 

In addition to direct deposition on skin under clothing, a potentially important effect is 

deposition of soil particles on clothing. Many radionuclides emit electrons of sufficient energy 

to penetrate through normal clothing and reach radiosensitive tissues in the basal layer of skin. 

Doses from contamination of clothing are discussed in Section 5. Clothing is assumed to be 

completely effective in shielding alpha particles emitted by radionuclides. 

Models and parameter values described in Sections 3 and 4 are used to estimate doses to 

skin due to deposition of radionuclides in particulate material on bare skin. When using these 

models, the following considerations should be kept in mind: 

 The fraction of the mass of airborne material incident on the body surface that is 

intercepted and retained on skin, r, is expected to be less than 1.0 in most regions of the 

body. That is, the concentration of airborne material that is intercepted and retained on 

skin in most regions of the body will be less than the concentration of material that is 

deposited on the ground surface during the time exposure to airborne material occurs. 

 In special cases, such as accumulation of soil particles on the back of the neck under a 

collar, under the belt, on the shin under the edge of boots, or behind the ears, the 

109
 The amount of material assumed to be deposited on skin should not exceed a reasonable 

upper bound of possible soil loadings. Sheppard and Evenden (1994) observed soil 

loadings on skin due to direct contact of 2 to 6 mgsoil per cm2

skin when soil was moist. 

However, at concentrations above 2 mgsoil per cm2

skin, dirt is visible on skin, and it is 

likely that brushing or cleaning would take place soon after contamination. Thus, if 

information is available, it may be desirable in some cases to verify that the soil loading 

does not exceed a maximum credible value before using eq. (3-1). Since that equation is 

expressed in terms of the activity concentration of material on skin (μCi cm–2

skin), the soil 

loading must be estimated using a specific activity of particles that accumulate on skin 

(μCi mg–1

soil), a quantity that is not always available in most situations involving 

exposure of military personnel. A reasonable maximum soil loading on skin can be an 

important concern in some exposure scenarios, such as exposure by direct contact with 

contaminated soil, exposure of forward observers to all previously deposited fallout that 

was resuspended by the blast wave in a nuclear detonation at NTS, or exposure to fallout 

that was resuspended by other vigorous stressors (e.g., helicopter landing or takeoff) that 

resulted in unusually high dust loadings in air. When maximum soil loadings occur, it 

could be reasonable to assume a relatively short time before the first washing and a high 

removal efficiency in the first washing in estimating doses to skin. 

110
Table 4-1. Interception and retention fractions estimated from data obtained in 

CENIZA-ARENA volcanic ash studies in Costa Rica 

Interception and retention fraction (r)

a

Body region or area Deterministic 

valueb 

Uncertainty 

distributionc 

90% credibility 

interval (CI) Comment 

Face, shoulders, back 

and sides of torso, 

forehead, palms 

0.015 LN (0.015, 3.6) 0.002–0.12 Little or no hair 

Chest (unspecified 

amount of hair) 

0.03 LN (0.03, 3.9) 0.003–0.28 Amount of hair from 

little to abundant 

Forearms, upper legs, 

lower legs (above boot 

edge) 

0.06 LN (0.06, 3.0) 0.01–0.36 Hair-covered areas 

Scalp 0.23 LN (0.23, 2.45) 0.053–1.0 

Back of neck under 

collar, under belt, under 

boot edge, behind ears 

1.5 Г (0.04, 1.2, 5) 0.04–5.0 Special regionsd 

a

 Interception and retention fraction is unitless ratio of mass of volcanic ash per unit area deposited and 

retained on skin in defined regions of the body to time-integrated mass of volcanic ash deposited per unit 

area on the ground. Values normally are less than 1.0, except at noted in footnote d. 

b

 Point estimates of parameters recommended for use in estimating deterministic values of dose to skin 

from dermal contamination. Values are used in Section 6 to investigate importance of doses to skin from 

dermal contamination. 

c

 LN = Lognormal (median, geometric standard deviation); Г = Gamma (5th percentile, 50th percentile, 

95th percentile). 

d

 In special regions of the body, material deposited in other regions can migrate and accumulate, and 

interception and retention fraction can be greater than 1.0 (see Section 4.1.5). 

111
Table 4-2. Summary of parameter values used to estimate electron doses to skin 

from dermal contamination 

Parameter Symbol Unit Deterministic 

valuea 

Uncertainty 

distributionb 

Interception and retention fraction r = (ah/s) See Table 4-1 

Particle-size adjustment PSa unitless 

Small particlesc 1.3 LN (1.3, 1.1) 

Large particlesd 0.8 T (0.4, 0.8, 1.0) 

Unknown particle sizese 1.0 U (0.4, 1.6) 

Enhancement due to moisture EM unitless 

Pacific Proving Ground 1.15 U (0.8, 1.5) 

Nevada Test Site 0.75 U (0.5, 1.0) 

Enrichment of specific activity EF unitless 

Small particlesc 1.3 T (1.0, 1.0, 2.0) 

Large particlesd 2.5 T (1.0, 2.5, 4.0) 

Unknown particle sizese 2.0 LU (1.0, 4.0) 

Activity-weight adjustment factor AW unitless 

Small particlesc 1 T (0.7, 1.0, 1.0) 

Large particlesd 0.03 LN (0.032, 2.0) 

Unknown particle sizese 0.1 LT (0.01, 0.1, 1.0) 

Deposition velocity VD m s–1 1.0 T (0.5, 1.0, 3.0) 

Wind speed VW m s–1 

Pacific Proving Ground 5.0 U (3.0, 7.0) 

Nevada Test Site 4.0 U (2.0, 6.0) 

Dose-rate factor at depth in tissue 

of 7 mg cm–2 

DRF rem h–1 per 

Ci cm–2

3.7 T (1.6, 3.7, 6.8) 

Skin-depth modification factor SDMF unitless 

Face, forehead, neck, shoulders, 

torso, upper legs 

1.3 T (0.7, 1.3, 1.7) 

Forearms, lower legs 0.9 T (0.5, 0.9, 1.5) 

Palms of hands, soles of feet 0.3 T (0.08, 0.3, 0.6) a Point estimates of parameters recommended for use in estimating deterministic values of dose to skin from dermal 

contamination. Values are used in Section 6 to investigate importance of doses to skin from dermal contamination. 

b

 LN = Lognormal (median, geometric standard deviation); T = Triangular (minimum, mode, maximum); U = 

Uniform (minimum, maximum); LU = Log-uniform (minimum, maximum); LT = Log-triangular (minimum, mode, 

maximum). 

c

 Term “small particles” refers to size distributions in which most particles have diameters < 100 m and median 

diameter is < 50 m. Parameter values for small particles are applicable, for example, to exposures far from ground 

zero in the Pacific or to exposures in cases of resuspension by winds or other mild stresses. 

d

 Term “large particles” refers to size distributions in which most particles have diameters > 50 m and median 

diameter is > 100 m. Parameter values for large particles are applicable, for example, to exposures of forward 

observers in blast-wave region of nuclear detonations at NTS that occur within the first few minutes. 

e

 Parameter values for unknown particle sizes are not intended to be used when substantial fractions of the activity 

of radionuclides were carried by small and large particles and those fractions can be estimated (see Section 4.2.5). 

112
Table 4-3. Summary of resuspension factors (RF, m–1) used to estimate 

airborne concentrations of radionuclides due to resuspension of 

radionuclides deposited on ground surface 

Uncertainty distribution 

Resuspension scenario 

Deterministic

valuea Probability 

distributionb 

90% credibility interval 

(CI) 

Human activities 

Vehicular traffic 2  10–5 LN (2 × 10–5, 11) 4 × 10–7 to 10–3 m–1 

Helicopter take-off or landing 1  10–3 LN (10–3, 4) 10–4 to 10–2 m–1 

Walking – 0.3 m above ground 2  10–5 LN (2  10–5, 5.7) 10–6 to 3 × 10–4 m–1 

Walking – 1 m above ground 1  10–7 LN (1  10–7, 6.2) 10–8 to 2 × 10–6 m–1 

Wind-driven resuspension 

Up to about 6 months after 

deposition 

1  10–6 LN (10–6, 16) 10–8 to 10–4 m–1

Years after deposition 3  10–8 LN (3  10–8, 33) 10–10 to 10–5 m–1

Detonations at NTSc 

Forward observers in blast-wave 

region at time of detonation; 

exposure to large particles onlyd 

1  10–5 LN (10–5, 16) 10–7 to 10–3 m–1

Participants in blast-wave region 

at times after detonation; 

exposure to small particles onlye 

1  10–7 LN (10–7, 67) 10–10 to 10–4 m–1

Participants who entered 

thermal-pulse region after 

detonation; exposure to small 

particles onlyf 

1  10–-5 LN (10–5, 16) 10–7 to 10–3 m–1 

a

 Point estimates of parameters recommended for use in estimating deterministic values of dose to skin 

from dermal contamination. Values are used in Section 6 to investigate importance of doses to skin from 

dermal contamination. 

b

 LN = Lognormal (median, geometric standard deviation). 

c

 Thermal-pulse and blast-wave regions near ground zero of nuclear detonations at NTS are described in 

Section 4.3.3. 

d

 Resuspension factor is used in estimating dermal contamination due to redeposition of large particles 

that fell to Earth within a few minutes after a detonation (see Sections 3.3.4 and 4.3.3). 

e

 Resuspension factor is used in estimating dermal contamination due to redeposition of small particles at 

times after large particles fell to Earth (see Sections 3.3.4 and 4.3.3). Resuspension factor applies to 

forward observers who remained in blast-wave region for some time after detonation and to observers or 

maneuver troops who entered blast-wave within a few hours after detonation. 

f

 Participants entered thermal-pulse region only at times after large resuspended particles in that region 

fell to Earth, when only small particles remained airborne. 

113
Table 4-4. Dose-rate factors for selected alpha-emitting radionuclides 

deposited on skin in specific regions of the bodya

Radionuclideb Dose-rate factorc,d 

(rem h–1 per μCi cm–2) Radionuclideb Dose-rate factorc,d (rem h–1 per μCi cm–2) 

Arms and legs 

 235U 6.9 × 101 239,240Pu 7.4 × 102

 238U 1.1 × 101 241Am 1.3 × 103

 238Pu 1.3 × 103 242Cm 2.9 × 103

Trunk 

 235U 3.2 × 103 239,240Pu 6.7 × 103

 238U 2.5 × 103 241Am 8.2 × 103

 238Pu 8.2 × 103 242Cm 1.1 × 104

Face 

 235U 4.0 × 103 239,240Pu 6.4 × 103

 238U 3.2 × 103 241Am 7.4 × 103

 238Pu 7.4 × 103 242Cm 9.6 × 103

Back of hand 

 242Cm 4.3 × 101 Others 0 

Palm of hand, 

sole of foot 

 All alpha 

 emitters 

0 

a

 Dose is mean equivalent dose to basal layer of skin. Dose-rate factors were calculated using model 

developed by Eatough (1997) [see eq. (4-6)] and distributions of epidermal thickness in different regions 

of the body reported by Whitton (1973). 

b

 Radionuclides listed are most important alpha emitters in fallout from nuclear weapon detonations. c

 Uncertainty in calculated dose-rate factors can be described using a multiplicative factor represented by 

a lognormal probability distribution with a GM at 1.0 and 90% CI of (0.33, 3). 

d

 Values do not account for reductions in dose rate due to shielding by particles to which alpha-emitting 

radionuclides are attached. Shielding by particles could reduce dose rates from alpha particles by factor 

represented by log-uniform probability distribution between 0.05 and 1.0; this distribution has a mean at 

about 0.3 and median at about 0.2 (see Section 4.6.2). 

114
Table 4-5. Summary of values of parameters used to model effect of 

inefficient showering on doses to skin from dermal contaminationa

Uncertainty distribution 

Parameter 

Deterministic 

valueb 

Probability 

distributionc

90% credibility interval 

(CI) 

Fraction removed by 

exfoliation of skin cells 

per shower 

(β; unitless) 

Upper limbs 0.05 T (0.025, 0.05, 0.075) (0.033, 0.067) 

Lower limbs 0.033 T (0.017, 0.033, 0.050) (0.022, 0.045) 

Trunk 0.025 T (0.012, 0.025, 0.038) (0.016. 0.034) 

Scalp 0.0083 T (0.0041, 0.0083, 0.013) (0.0055, 0.012) 

Fraction removed by 

washing per shower 

(γj; unitless) 

Normal showeringd

1st shower 0.7 T (0.45, 0.7, 0.95) (0.53, 0.87) 

2nd shower 0.35 T (0.2, 0.35, 0.5) (0.25, 0.45) 

3rd shower 0.1 T (0.05, 0.1, 0.15) (0.066, 0.13) 

≥ 4th shower 0.02 T (0.005, 0.02, 0.035) (0.01, 0.03) 

Highly efficient 

showeringe

1st shower 0.85 T (0.7, 0.85, 1) (0.75, 0.95) 

2nd shower 0.6 T (0.4, 0.6, 0.8) (0.46, 0.74) 

3rd shower 0.25 T (0.1, 0.25, 0.4) (0.15, 0.35) 

≥ 4th shower 0.02 T (0.005, 0.02, 0.035) (0.01, 0.03) 

a

 Models are described in Section 3.5 and assumptions about parameters are discussed in Sections 4.7.1 

and 4.7.2. 

b

 Point estimates of parameters recommended for use in estimating deterministic values of dose to skin 

from dermal contamination. 

c

 T = triangular (minimum, mode, maximum). 

d

 Values apply when it is assumed that special efforts to remove radioactive contamination from skin 

would not be made. 

e

 Values apply when it is assumed that significant radioactive contamination of skin is known or strongly 

suspected and special efforts would be made to remove contamination while showering. 

115
1

10

100

1000

.1 1 5 10 20 30 50 70 80 90 95 99 99.9

Irazu Volcano

Personnel contamination experiments

June 15

June 16

October 6

January 7 - #1

January 7 - #2

January 15

Particle diameter (micron)

Percentage of weight of particles with diameters less than a given value

Figure 4-1. Cumulative weight distributions of volcanic ash particles in personnel 

contamination studies during eruption of Irazu Volcano in Costa Rica (Miller 1966b). 

116
10

100

1000

10000

.1 1 5 10 20 30 50 70 80 90 95 99 99.9

Fallout at NTS site, close to ground zero

Shot DIABLO - sample D4 (1.7 km from GZ)

Shot Shasta - sample S3 (4 km from GZ)

Particle diameter (micron)

Percentage of weight of particles with diameters less than a given value

Figure 4-2. Cumulative weight distributions of particles in fallout at NTS (Miller, 1969; data at 

Shot DIABLO from Table 14; data at Shot SHASTA from Table 16 and Fig. 12). 

117
Figure 4-3. Electron dose-rate factors at various depths in skin vs emitted electron energy for 

monoenergetic sources deposited uniformly on the body surface; arrows at bottom of 

figure give electron energies below which dose-rate factor at each depth is zero 

[reproduced from Kocher and Eckerman (1987)]. To convert dose-rate factor to units of 

rem h–1 per μCi cm–2 used in this report, multiply values in figure by 423. 

118
100

101

102

103

2 hours

1 day

2 days

10 days30 days

6 months

1 year

4 years

T

post

= 1 h

T

post

= 6 h

T

post

= 12 h

T

post

Dose to skin after first shower (

= 24 h

D

sh)

(arbitrary units)

Time after detonation when deposition on skin ceased

Highly efficient 

showering

Normal

showering

Figure 4-4. Dependence of dose to skin after first shower for normal and highly efficient 

showering on time after detonation when deposition on skin ceased (T0) and time to first 

shower (ΔTpost); calculations assume deposition on trunk of body. 

119
100

101

102

103

2 hours

1 day

2 days

10 days30 days

6 months

1 year

4 years

Upper Limbs

Lower Limbs

Trunk

Scalp

Dose to skin after first shower (

D

sh)

(arbitrary units)

Time after detonation when deposition on skin ceased

Highly efficient showering

Time to first shower (T

post) = 6 h

Figure 4-5. Dependence of dose to skin after first shower in different regions of body on time 

after detonation when deposition on skin ceased (T0), assuming highly efficient 

showering and time to first shower (ΔTpost) of 6 hours. 

120
100

101

102

1 612 24

D

1

 - Dose to time of first shower

D

sh

 - Dose after first shower

D

N

 - Total dose

Dose to skin

(arbitrary units)

Time to first shower (h)

Normal showering

Time after detonation when deposition ceased (T

0

) = 2 h

Figure 4-6. Dependence of dose to skin to time of first shower, dose to skin after first shower, 

and total dose on time to first shower (ΔTpost), assuming normal showering and time after 

detonation when deposition on skin ceased of 2 hours; calculations assume deposition on 

trunk of body. 

121
100

101

102

103

1 6 12 24

D

1

 - Dose to time of first shower

D

sh - Dose after first showering

D

N

 - Total dose

Dose to skin

(arbitrary units)

Time to first shower (h)

Normal showering

Time after detonation when deposition ceased (T

0

) = 6 months

Figure 4-7. Dependence of dose to skin to time of first shower, dose to skin after first shower, 

and total dose on time to first shower (ΔTpost), assuming normal showering and time after 

detonation when deposition on skin ceased of 6 months; calculations assume deposition 

on trunk of body. 

122
100

101

102

103

1 6 12 24

D

1

 +D

dep

- Dose to time of first shower

D

sh

- Dose after first shower

D

N

 + D

dep

- Total dose

Dose to skin

(arbitrary units)

Time to first shower (hours)

Normal showering

Time detonation when deposition ceased (T

0

) = 6 months

Figure 4-8. Dependence of dose to skin to time of first shower, dose to skin after first shower, 

and total dose on time to first shower (ΔTpost), assuming normal showering and time after 

detonation when deposition ceased of 6 months; calculations are same as in Fig. 4-7, 

except additional dose during continuous deposition on skin for period of 4 hours is 

included. 

123
10-1

100

101

102

103

Normal showering

Highly efficient showering

Dose to skin after first shower (

D

sh)

(arbitrary units)

Time after detonation when deposition on skin ceased 2 hours 1 day 2 days 10 days 30 days 6 months 1 year 4 years

Time to first shower (T

post )= 6 h

Figure 4-9. Uncertainties in doses to skin after first shower for normal and highly efficient 

showering and different times after a detonation when deposition on skin ceased (T0), 

assuming time to first shower of 6 hours; calculations assume deposition on trunk of 

body. 

124
5. DOSES TO SKIN FROM CONTAMINATED CLOTHING 

In addition to direct deposition of fallout or resuspended materials onto bare skin or skin 

under clothing, a potentially important source of exposure of skin is radioactive material that is 

deposited and retained on clothing. Many radionuclides emit electrons of sufficient energy to 

penetrate through normal clothing and reach radiosensitive tissues in the basal layer of skin. 

However, on the basis of data on the thickness of clothing discussed in Section 5.3 and data on 

ranges of alpha particles in matter (ICRU 1993), alpha particles emitted by radioactive materials 

deposited on clothing are not sufficiently energetic to penetrate through clothing and the 

epidermis and deliver a dose to the basal layer of skin. 

In cases of contamination of clothing, doses to skin can be calculated using eq. (3-1), 

except the activity concentration and dose-rate factor are specific to deposition on clothing: 

  (5-1) clothing DRFtCtD clothing  

where 

tD )( 

 = dose rate to skin at time t (rem h–1); 

Cclothing(t) = activity concentration of radionuclides on clothing at time t 

 (μCi cm–2

clothing); 

DRFclothing = dose-rate factor for electrons emitted by radionuclides deposited on 

clothing at assumed depth of radiosensitive tissues (rem h–1 per 

 μCi cm–2

clothing). 

The following sections discuss available information on soil loading and deposition of airborne 

particles on clothing. 

5.1 Soil Loading on Clothing 

Black (1962) measured the accumulation of dirt on clothing, bare skin, and skin under 

clothing of military personnel who wore full combat fatigues and while crawling under simulated 

combat conditions on bare dry soil or dry grass. Accumulation of dirt on clothing was a factor of 

10 to 125 higher than on skin under clothing or near clothing (on the wrist and around the neck). 

125
Measured accumulations of soil on clothing were 13 mg cm–2 at the knees, 8 mg cm–2 at the 

elbows, 5 mg cm–2 on the back and under the belt in front, 1 mg cm–2 on the chest and under the 

belt in back, and 0.5 mg cm–2 at the armpits, inside of the elbow, at the side of the neck, and 

around the ankles. Soil loading increased if clothing was moist. The maximum soil loading on 

clothing that did not appear to be “caked” was 5 mg cm–2. 

Data summarized above suggest that a maximum credible soil loading on clothing might 

be about 10 mg cm–2. However, the soil loading can vary greatly from one area of the body to 

another. In addition, soil loadings in some scenarios (e.g., digging trenches or installing 

equipment in the field) could be substantially less than values measured by Black (1962) under 

conditions of combat crawling, which involves extensive contact with the ground surface. 

Therefore, judgment generally would be required in selecting an appropriate soil loading. 

5.2 Deposition and Retention of Airborne Particles on Clothing

Contamination of clothing by deposition and retention of airborne particles can be a 

significant pathway for exposure of skin. As discussed by Black (1962), Marshallese were 

exposed to descending fallout from Shot BRAVO at Operation CASTLE and experienced severe 

burns from electrons (beta particles) on areas of bare skin and areas of skin covered by clothing. 

Although burns in areas of bare skin were more severe than burns in areas covered by clothing, 

especially in folds of skin where radionuclides accumulated, it is nonetheless important to 

consider contamination of clothing and potential doses to skin from this exposure pathway. 

In the volcanic ash studies in Costa Rica, only one contamination factor (ah) for clothing 

(a value of 385 cm2

 on a blouse) was reported (Table 2-2). Since the surface area of clothing for 

which this ah was measured was not indicated, an interception and retention fraction (r) cannot 

be estimated. Studies of military personnel who crawled through dirt or grassy areas described 

by Black (1962) probably are not relevant to determining deposition and retention of airborne 

radioactive material onto clothing. 

Fogh et al. (1999) measured deposition velocities for particles of diameter 0.5, 2.5 and 

8 m on bare skin and clothing in an indoor environment. This experiment is not directly 

relevant to exposure to fallout from nuclear weapons testing because most fallout particles were 

126
larger than 10 m and deposition occurred in an outdoor environment subject to winds or other 

air currents. Nevertheless, data obtained by Fogh et al. (1999) indicate that deposition velocities 

onto clothing are smaller than deposition velocities onto bare skin. Under that condition, for a 

given concentration of a contaminant in air, clothing would be less contaminated than bare skin. 

Deposition and retention on clothing probably depend on the texture of clothing materials 

and whether clothing is moist. Accumulation of fallout particles in pockets or wrinkles on 

clothing presumably can be significant. Deposition of small particles also could be enhanced by 

the presence of static electricity on clothing. 

Given the lack of information on interception and retention of airborne particles on 

clothing, judgment is required to develop a probability distribution to represent the uncertainty in 

this parameter. For example, it seems unlikely that interception and retention on clothing would 

be higher than on bare forearms, where deposition is enhanced by the presence of hair. Thus, an 

average interception and retention fraction, r, for clothing probably is less than 0.06, and the 

maximum value on portions of clothing with no folds probably is less than 0.4 (Table 4-1). 

However, available data do not permit an evaluation of whether interception and retention of 

particles on clothing is higher or lower than interception and retention on skin of the face. In the 

absence of data, we assume that a reasonable representation of the uncertainty in the interception 

and retention fraction for clothing is the probability distribution of r for the chest specified in 

Table 4-1 [lognormal distribution with a GM of 0.03 and GSD of 3.9; 90% CI of (0.003, 0.28)]. 

This distribution is broad and includes values both higher and lower than the average 

interception and retention fraction for skin of the face or forearms. 

Given an estimate of the interception and retention fraction, r, the effective interception 

and retention fraction, ARf, can be calculated in accordance with eq. (3-4) using estimates of the 

particle-size adjustment factor (PSa), enhancement due to moisture (EM), specific-activity 

enrichment factor (EF), and activity-weight adjustment factor (AW) obtained from Table 4-2 that 

apply to the assumed particle-size distribution in a given exposure scenario. Then, except for a 

modification of the dose-rate factor discussed in the following section, models presented in 

Section 3 can be used to estimate dose to skin. 

127
5.3 Modification of Dose-Rate Factors Due to Shielding by Clothing

When radionuclides are deposited on clothing, the dose to skin is reduced compared with 

the dose from exposure to radionuclides on bare skin, due to the shielding provided by the layer 

of clothing. Estimates of doses from contamination of clothing should account for this shielding. 

A dose-rate factor for radionuclides on clothing can be estimated using the dose-rate factor for 

radionuclides on bare skin modified by a factor to account for shielding by clothing: 

DRFclothing  DRFskin CMF (5-2) 

where 

DRFclothing = dose-rate factor for electrons emitted by radionuclides on clothing (rem h–1

per μCi cm–2

clothing); 

DRFskin = dose-rate factor for electrons emitted by radionuclides on bare skin 

(rem h–1 per μCi cm–2

skin); 

CMF = modifying factor to account for reduction in dose rate due to shielding by 

layer of clothing (unitless). 

The two dose-rate factors are values that apply at the same depth of radiosensitive tissues. The 

modifying factor CMF affects the dose to skin in the same way as the skin-depth modification 

factor (SDMF) introduced in Section 4.6.1 [eq. (4-4)] and discussed in Section 4.6.1.2, except 

CMF is always less than 1.0. 

Barss (2000; Table 13) and Barss and Weitz (2006; Table 4) give modifying factors to 

represent the shielding provided by light clothing that apply to exposure to mixtures of 

radionuclides in fallout on the ground surface. The depth of radiosensitive tissues was assumed 

to be 7 mg cm–2, and light clothing was assumed to be 0.7 mm thick with a density of 0.4 g cm–3, 

which is equivalent to a thickness of tissue of 28 mg cm–2 (Barss 2000). Modifying factors for 

light clothing were calculated as a function of height above ground and time after a detonation. 

Modifying factors at a height of 1 cm are the best approximation of modifying factors that apply 

to contamination on clothing. The modifying factor for light clothing at a height of 1 cm ranges 

from 0.4 to 0.6, depending on time after detonation. Higher values occur at times within one 

day, and lower values occur at times of one week or later. 

128
For a 0.7-mm layer of clothing with an equivalent thickness of tissue of 28 mg cm–2, the 

total depth of radiosensitive tissues at an average depth of 7 mg cm–2 below the body surface is 

35 mg cm–2. Thus, in regions of the body other than the palms of the hands or soles of the feet, 

the modifying factor for clothing (CMF) should be similar to the skin-depth modification factor 

(SDMF) in eq. (4-4) that applies at a nominal depth of 40 mg cm–2 when radionuclides are 

deposited on bare skin. This SDMF, which is discussed in Section 4.6.1.2.3, is represented by a 

triangular probability distribution with a minimum at 0.1, mode at 0.3, and maximum at 0.6 

(Table 4-2). The assumed probability distribution encompasses the modifying factors reported 

by Barss (2000) and Barss and Weitz (2006) that apply at 1 cm above ground, which range from 

0.4 to 0.6. The assumed range of CMF is sufficiently broad that it should be applicable in 

regions of the body where the nominal depth of radiosensitive tissues is 4 mg cm–2 (face, 

forehead, neck, shoulders, torso, and upper legs) or 8 mg cm–2 (arms or lower legs). 

129
6. EVALUATION OF IMPORTANCE OF DOSES TO SKIN 

FROM DERMAL CONTAMINATION 

External exposure of skin to beta-emitting radionuclides on the ground surface is an 

important exposure pathway for many military participants. Thus, one way to evaluate the 

potential importance of doses to skin from dermal contamination is to compare them with doses 

from exposure to beta emitters on the ground surface. In this section, we investigate conditions 

under which the dose to skin from dermal contamination could be at least a substantial fraction 

of the dose from beta emitters on the ground. The general approach is to estimate ratios of doses 

from dermal contamination to doses from ground-surface exposure in defined scenarios. 

In this assessment, comparisons of electron doses to skin from dermal contamination and 

exposure to a contaminated ground surface in different scenarios are based on estimated 

inventories of radionuclides in fallout at 2 days and 4 years after a nuclear detonation involving 

fission of 235U. A total of 82 radionuclides were taken into account in dose estimates at 2 days 

and 27 in dose estimates at 4 years (Trabalka and Kocher 2007). 

The dose rate to skin from a single beta emitter that is assumed to be uniformly deposited 

on the ground surface is calculated as: 

 (6-1) gs gs gs  DRFCD

where 

DRFgs = dose-rate factor at height of 1 m above ground for radionuclide on the ground 

surface (rem h–1 per μCi cm–2

ground) 

Cgs = activity concentration of radionuclide on the ground surface (μCi cm–2

ground

per fission). 

The dose rate from all radionuclides in fallout combined is calculated on the basis of an 

estimated activity concentration of each radionuclide on the ground surface per fission of 235U.27 

The activity of each radionuclide per fission was obtained by multiplying its fission yield 

 

27 Only relative activities of radionuclides are important in evaluating the relative importance of doses 

from dermal contamination and ground-surface exposure.

130
(number of atoms per fission) given by England and Rider (1994) by its activity per atom 

adjusted by a factor to account for decay and buildup of any radioactive decay products at 2 days 

and 4 years after detonation. Trabalka and Kocher (2007) summarize the assumed activities of 

radionuclides per fission at 2 days and 4 years after detonation. Dose-rate factors for exposure to 

beta emitters on the ground surface were obtained from Eckerman and Ryman (1993). 

Equation (6-1) is integrated over the duration of exposure to a contaminated ground 

surface (Tground) to obtain doses to skin per fission. The duration of exposure to radionuclides 

on the ground surface can be different from the duration of exposure to radionuclides deposited 

on skin. For example, an exposed individual can leave an area where the ground surface is 

contaminated, but contamination of skin will continue for an additional period of time, until the 

next shower. 

Doses to skin from dermal contamination are estimated for each radionuclide using 

equations presented in Sections 3.2 and 3.3 for descending fallout and resuspension of material 

from the ground surface, respectively. Total doses are obtained by summing the dose from each 

radionuclide. Calculated doses to skin do not account for effects of fractionation or differences 

in radionuclide inventories depending on the fission mode (e.g., fission of 238U or 239Pu 

compared with the assumed fission of 235U). However, the importance of dermal contamination 

should not be significantly affected by assumptions regarding fractionation or fission mode. 

Scenarios of dermal contamination that were compared with ground-surface exposure in 

this analysis include exposure due to (1) descending fallout, (2) resuspension by vehicular traffic, 

(3) wind-driven resuspension, and (4) resuspension of old fallout by the thermal pulse or blast 

wave produced in a nuclear detonation. In all resuspension scenarios, exposure was assumed to 

occur at 2 days or 4 years after a detonation. The only parameters in the calculations that differ 

at the two times are the resuspension factor for wind-driven resuspension and the relative 

activities of different radionuclides. In each scenario, we estimated doses to skin of the face and 

arms, which are regions of body where deposition of airborne particles on bare skin most likely 

occurs. Doses to the arms generally are higher than doses to the face, due to the greater retention 

of depositing material on hairy portions of the forearms. 

None of the calculations for the different scenarios discussed in this section take into 

account the effect of inefficient showering in increasing doses from dermal contamination; i.e., 

131
all contamination on skin is assumed to be removed at the time of the first shower after 

deposition on skin occurred. Neglect of inefficient showering results in underestimates of the 

importance of doses from dermal contamination relative to doses from exposure to electrons 

emitted by radionuclides on the ground surface. The importance of inefficient showering is 

illustrated by calculations presented in Section 4.7.3 and Appendix E. 

Two scenarios for exposure to descending fallout were considered. In both scenarios, 

contamination of skin was modeled as an acute event, as described in Section 3.2. In one 

scenario, we assumed that, due to the proximity to ground zero, exposure to descending fallout at 

NTS involved an unknown mixture of large and small particles.28 We also assumed that 

exposure to fallout deposited on the ground surface occurred over a period of 4 hours, and that an 

individual showered at 12 hours after deposition on skin occurred. In the second scenario, we 

assumed that exposure occurred far from ground zero in the Pacific and, thus, that exposure to 

descending fallout involved small particles only. We also assumed that exposure to fallout 

deposited on the ground surface occurred over a period of 8 hours, and that an individual 

showered at 12 hours after deposition on skin occurred. 

A single scenario involving resuspension of radioactive material by vehicular traffic at 

NTS and exposure while marching behind vehicles was analyzed. We assumed that dust 

generated by vehicles at the height of the face or arms contained only small particles. We also 

assumed that exposure in a contaminated area occurred over a period of 4 hours, and that 

showering occurred at 8 hours after leaving that area. 

Exposure to radioactive material resuspended by winds at NTS or in the Pacific was 

considered. This type of scenario involves exposure to small particles under normal conditions. 

We assumed that the duration of outdoor activities in a contaminated area was 8 hours, and that 

showering occurred at 4 hours after leaving that area. 

Two scenarios of exposure to old fallout that was resuspended by a nuclear detonation at 

NTS were considered. The first scenario involved exposure of forward observers who were 

located in the blast-wave region near ground zero at the time of a detonation. Dermal 

 

28 Such a distribution of particle sizes could occur close to ground zero if, for example, exposure to 

descending fallout occurred at locations away from the centerline of the fallout plume, where the fraction 

of the activity of radionuclides that was carried by smaller particles should be larger.

132
contamination was assumed to be due to the combined effects of the initial shower of large 

resuspended fallout particles, which occurred essentially at the time of detonation, and deposition 

of smaller resuspended particles, which occurred during the remainder of the time that forward 

observers spent in the blast-wave region. The second scenario involved exposure of maneuver 

troops who entered the thermal-pulse or blast-wave region some tens of minutes after detonation 

(i.e., after large resuspended particles had redeposited on the ground) and were exposed to small 

particles in the lingering dust cloud; separate results are presented for exposure of maneuver 

troops in the two regions. We assumed that forward observers and maneuver troops spent 

2 hours in a contaminated area, and that showering occurred at 12 and 10 hours after deposition 

onto skin ceased, respectively. 

In all scenarios described above, values of model parameters were chosen to represent the 

specified conditions of exposure. For example, the average wind speed was assumed to be 

4 m s–1 at NTS and 5 m s–1 in the Pacific; this difference results in higher doses due to 

resuspension by winds in the Pacific. Values of the particle-size adjustment factor (PSa), 

specific-activity enrichment factor (EF), and activity-weight adjustment factor (AW) were chosen 

on the basis of the assumed particle sizes of resuspended material (large, small, or unknown 

mixture), and values of the adjustment factor to account for moisture on skin (EM) were chosen 

to represent conditions at NTS or in the Pacific. Point estimates of dose were obtained by 

performing calculations using the deterministic values of parameters in Tables 4-1, 4-2 and 4-3. 

All parameter values are summarized by exposure scenario in Appendix C, Tables C-1 to C-6. 

A comparison of doses to skin from dermal contamination with doses from exposure to a 

contaminated ground surface is presented in Table 6-1 for exposures that took place shortly after 

a detonation and in Table 6-2 for exposures that took place years after a detonation. These 

comparisons indicate that the dose from dermal contamination could be at least a significant 

fraction of the dose from ground-surface exposure in the following scenarios: 

1. Exposure to descending fallout at NTS or in the Pacific; 

2. Exposure to fallout that was resuspended by vehicular traffic at any time after a 

detonation at NTS (this scenario was not analyzed in the Pacific); 

3. Exposure to material that was resuspended by winds at times shortly after a 

detonation at NTS or in the Pacific; 

133
4. Exposure of maneuver troops at NTS who entered the thermal-pulse region at some 

time (e.g., tens of minutes) after a detonation, without regard for the age of previously 

deposited fallout. 

The importance of doses from dermal contamination relative to doses from ground-surface 

exposure in these scenarios would increase substantially if the effect of inefficient showering 

were taken into account, as illustrated in Section 4.7.3. 

Doses from dermal contamination are unimportant in the calculations for the other 

exposure scenarios considered in this evaluation. In resuspension scenarios, doses from dermal 

contamination are unimportant compared with doses from ground-surface exposure when the 

fraction of the activity of radionuclides on the ground that is resuspended is very small. 

Exposure to large particles only also results in low doses from dermal contamination relative to 

doses from ground-surface exposure because large particles are not easily retained on skin and 

the activity-weight adjustment factor (AW) is low. 

In scenarios involving wind-driven resuspension, the duration of exposure was assumed 

to be 8 hours, followed by a period of 4 hours until an exposed individual was assumed to 

remove contamination from skin by showering. In the Pacific, however, exposure often occurred 

over a period of weeks or months. In such cases, doses between successive daily showers would 

need to be summed to obtain a total dose. 

Results in Tables 6-1 and 6-2 were obtained using deterministic estimates of parameter 

values and, therefore, are based on nominal point estimates of dose to the skin for each pathway. 

An uncertainty analysis was not performed in this comparison exercise. However, we believe 

that such an analysis would show that the dose to skin from dermal contamination could increase 

greatly in importance relative to the dose from ground-surface exposure in many scenarios when 

upper credibility limits (95th percentiles) of estimated doses are compared. For example, in some 

resuspension scenarios, the 95th percentile of the resuspension factor is two orders of magnitude 

higher than the median estimate (Table 4-3). Since this uncertainty is much larger than the 

uncertainty in estimating the dose from ground-surface exposure, the dose from dermal 

contamination relative to the dose from ground-surface exposure at the 95th percentile would be 

at least a factor of 100 higher. 

134
In summary, calculations presented in this section indicate that, in some types of 

exposure scenarios, electron doses to skin from dermal contamination are significant, and 

sometimes dominant, compared with electron doses to skin from exposure to radionuclides on 

the ground surface. Since electrons doses to skin from radionuclides on the ground are much 

higher than doses from photons (Barss 2000), we can conclude that electron doses to skin from 

dermal contamination can be an important contributor to the total dose to skin from all exposure 

pathways. Results of our comparative analysis and judgments about an upper credibility limit of 

these doses indicate that electron doses to skin from dermal contamination should be estimated in 

most exposure scenarios. 

135
Table 6-1. Estimated doses to skin from external exposure to beta-emitting radionuclides on 

ground surface and doses to skin from dermal contamination in selected scenarios for 

exposure to airborne particles – Exposure at times shortly after a detonationa 

Exposure scenario 

Dose from groundsurface exposureb

(rem per fission) 

Dose from dermal 

contamination 

(rem per fission) 

Ratio of doses 

(dermal/ground)

Descending fallout

NTS, near ground zero

Face 6.1 × 10–11 9.5 × 10–12 0.16 

Arms 6.1 × 10–11 2.6 × 10–11 0.43 

Pacific, far from ground zero

Face 1.1 × 10–10 1.2 × 10–10 1.1 

Arms 1.1 × 10–10 3.4 × 10–10 3.1 

Resuspension by vehicular traffic (marching behind vehicles)

NTS, near ground zero

Face 6.1 × 10–11 1.9 × 10–11 0.31 

Arms 6.1 × 10–11 5.2 × 10–11 0.85 

Resuspension by winds

NTS, near ground zero

Face 1.1 × 10–10 5.9 × 10–12 0.054 

Arms 1.1 × 10–10 1.6 × 10–11 0.15 

Pacific, far from ground zero

Face 1.1 × 10–10 1.1 × 10–11 0.10 

Arms 1.1 × 10–10 3.1 × 10–11 0.29 

Resuspension by nuclear detonation at NTS – forward observers

Face 3.3 × 10–11 5.3 × 10–14 0.0016 

Arms 3.3 × 10–11 1.5 × 10–13 0.0045 

Resuspension by nuclear detonation at NTS – maneuver troops in blast-wave region

Face 3.3 × 10–11 5.2 × 10–14 0.0016 

Arms 3.3 × 10–11 1.4 × 10–13 0.0044 

Resuspension by nuclear detonation at NTS – maneuver troops in thermal-pulse region

Face 3.3 × 10–11 5.2 × 10–12 0.16 

Arms 3.3 × 10–11 1.4 × 10–11 0.44 

a

 Exposure is assumed to occur at 2 days after a detonation.

b

 Doses from exposure to radionuclides on ground surface are scenario-dependent, due to differences in 

assumed duration of exposure.

136
Table 6-2. Estimated doses to skin from external exposure to beta–emitting radionuclides on 

ground surface and doses to skin from dermal contamination in selected scenarios for 

exposure to airborne particles – Exposure at long times after a detonationa 

Exposure scenario 

Dose from groundsurface exposureb

(rem per fission) 

Dose from dermal 

contamination 

(rem per fission) 

Ratio of doses 

(dermal/ground)

Resuspension by vehicular traffic (marching behind vehicles) 

NTS, near ground zero

Face 6.7 × 10–15 2.2 × 10–15 0.32 

Arms 6.7 × 10–15 6.0 × 10–15 0.90 

Resuspension by winds 

NTS, near ground zero

Face 1.2 × 10–14 2.1 × 10–17 0.0017 

Arms 1.2 × 10–14 5.8 × 10–17 0.0047 

Pacific, far from ground zero

Face 1.2 × 10–14 4.0 × 10–17 0.0032 

Arms 1.2 × 10–14 1.1 × 10–16 0.0089 

Resuspension by nuclear detonation at NTS – forward observers 

Face 3.8 × 10–15 6.1 × 10–18 0.0016 

Arms 3.8 × 10–15 1.7 × 10–17 0.0045 

Resuspension by nuclear detonation at NTS – maneuver troops in blast-wave region 

Face 3.8 × 10–15 6.0 × 10–18 0.0016 

Arms 3.8 × 10–15 1.7 × 10–17 0.0044 

Resuspension by nuclear detonation at NTS – maneuver troops in thermal-pulse region

Face 3.8 × 10–15 6.0 × 10–16 0.16 

Arms 3.8 × 10–15 1.7 × 10–15 0.44 

a

 Exposure is assumed to occur at 4 years after a detonation.

b

 Doses from exposure to radionuclides on ground surface are scenario-dependent, due to differences in 

assumed duration of exposure.

137
7. SUMMARY AND CONCLUSIONS

Many military personnel who participated in the atmospheric nuclear-weapons testing 

program were subjected to contamination of skin and clothing by radioactive particles, and such 

contamination could have been an important contributor to external doses to skin. The primary 

purpose of this report is to present an approach to estimating doses to radiosensitive tissues in the 

basal layer of skin from dermal contamination by deposition of particles in descending fallout 

from a nuclear weapons detonation or deposition of radioactive material that was resuspended 

from the ground surface or other surfaces (e.g., weather deck of a ship) by various human 

activities or the wind. This report also considers doses to skin when clothing is contaminated or 

when dermal contamination occurs as a result of direct contact with a contaminated ground 

surface or object. The main concern of this report is estimation of doses to skin from exposure to 

electrons (beta particles) emitted by radionuclides on the body surface. Estimation of doses from 

dermal contamination by radionuclides that emit alpha particles also is considered. Deposition 

of descending fallout or resuspended radioactive material is expected to produce uniform 

contamination on relatively large areas of the body surface. However, levels of contamination of 

skin are expected to vary in different regions of the body. Doses to skin from exposure to 

individual “hot” particles are not treated in this report. 

This report makes four contributions to the development of a methodology to estimate 

doses to skin from dermal contamination. The first is a summarization of relevant experimental 

data on dermal contamination, including data on soil loadings on skin in different regions of the 

body under various conditions, data on deposition and retention of volcanic ash particles on skin 

under field conditions, and data obtained in wind-tunnel studies and in indoor environments. 

The second contribution is the development of models to estimate contamination of skin by 

deposition of descending or resuspended fallout or by contact with contaminated ground or other 

surfaces. Once activity concentrations of radionuclides on skin are estimated for an exposure 

scenario of interest, doses to skin are estimated using published dose-rate factors (dose rates to 

skin per unit activity concentration) for beta-emitting radionuclides or dose-rate factors for 

alpha-emitting radionuclides that we calculated on the basis of a published model for alpha 

dosimetry in the basal layer of skin. The third contribution is the development of models to take 

into account the effect of incomplete removal of radionuclides from skin by showering in 

138
increasing doses from dermal contamination. On the basis of available data on efficiencies of 

removal of contamination from skin by washing and turnover times of skin cells by exfoliation, 

these models represent the fraction of contamination remaining on skin after the first shower 

following a deposition and after subsequent daily showers. The fourth contribution is the 

development of probability distributions to represent uncertainties in parameters in models to 

estimate activity concentrations of radionuclides that are deposited and retained on skin in 

various scenarios, uncertainties in parameters in models to estimate the effect of inefficient 

showering, and uncertainties in dose-rate factors for beta-emitting radionuclides. 

Modeling of skin contamination by direct contact with contaminated soil or other 

materials relies on relevant data on soil loading on skin and clothing. Any calculated or assumed 

dermal soil loading in scenarios involving contact transfer of contaminated material should not 

exceed 2 mgsoil per cm2

skin and in most cases should be less than 1 mgsoil per cm2skin. Soil loading 

on clothing can be as high as 13 mg cm–2, but loadings higher than 5 mg cm–2 appear as “caked” 

soil and are less likely to occur and to remain on clothing for long periods after accumulation. 

Modeling of skin contamination by deposition of descending fallout is based on estimates 

of the fraction of incident material that is intercepted and retained in various regions of the body. 

Interception and retention fractions are derived mainly on the basis of measured accumulations 

of ash particles on the ground surface and in different regions of the body of human subjects 

while engaged in outdoor activities following eruption of the Irazu Volcano in Costa Rica. 

On the basis of data obtained in the volcanic ash studies, we would expect that skin of the 

face, shoulders, and back of the torso should intercept and retain, on average, about 1.5% of the 

mass of airborne particles that impact those regions of the body. We also would expect that an 

average interception and retention fraction should be about 6% on the forearms and upper legs, 

3% on the chest, and 17% on the scalp; these higher values probably are largely a consequence 

of enhanced retention due to the presence of hair in those regions. Interception and retention 

fractions greater than 1.0 are possible in special regions of the body, such as the back of the neck 

under a collar, behind the ears, or under a belt, where material deposited on other parts of the 

body can migrate and accumulate. 

Interception and retention fractions derived from the volcanic ash studies are adjusted 

when applied to exposure conditions for military personnel that were different from those in 

139
Costa Rica. Particle size is an important determinant of retention on skin. Studies indicate that 

retention on skin decreases with increasing particle size for particle diameters greater than about 

50 m, whereas particles of diameter less than about 50 m have similar retention on skin. On 

the basis of this information, interception and retention fractions are adjusted to account for a 

difference between particle-size distributions of airborne materials to which military personnel 

were exposed in various scenarios at NTS or in the Pacific and particle-size distributions in the 

volcanic ash studies. In addition, since retention is enhanced when moisture is present on skin, 

interception and retention fractions obtained from the volcanic ash studies are adjusted 

downwards (or upwards) when exposure occurred under conditions where there was less (or 

more) humidity than in Costa Rica. 

Interception and retention fractions obtained in the volcanic ash studies and the 

adjustments to account for differences in particle-size distributions and the effect of moisture on 

skin that are used in applying those fractions to exposures of military personnel are defined with 

respect to the mass of airborne particles. Estimation of activity concentrations of radionuclides 

on skin, which is the quantity of interest in estimating dose, takes into account two other possible 

effects related to particle-size distributions in descending or resuspended fallout. First, since 

skin preferentially retains small particles, the specific activity of material retained on skin is 

enhanced compared with the specific activity of material incident on the body when 

radionuclides are preferentially distributed on the surface of particles. This adjustment is largest 

when airborne material consists mainly of large particles. Second, measurements at NTS 

showed that large particles in weapons fallout carried most of the activity at locations within a 

few miles of ground zero. Consequently, since small particles are preferentially retained on skin, 

the activity concentration of fallout deposited on skin can be much lower than the activity 

concentration on the ground surface when most fallout particles are large. This effect is taken 

into account using an adjustment factor that represents the difference between activity and 

weight particle-size distributions in fallout. 

To estimate contamination of skin due to deposition of resuspended fallout, an activity 

concentration of radionuclides in air relative to the activity concentration on the ground or other 

surface is first estimated using a resuspension factor. A flux density of resuspended material 

incident on the body (activity per unit area per unit time) is calculated using a wind speed or 

140
deposition velocity. Interception and retention fractions for descending fallout then are used to 

estimate the fraction of the activity of resuspended material incident on the body that is deposited 

and retained on skin. Contamination of skin due to deposition of resuspended material of a given 

particle size increases with increasing wind speed or deposition velocity. 

In cases of exposure to descending fallout, deposition on skin occurs during a relatively 

short time and can be modeled as an acute event. In contrast, dermal contamination by 

resuspension of nuclear weapon debris usually can be modeled as a continuous process, 

especially when deposition of resuspended fallout onto skin can take place over many hours or 

days (e.g., in cases of wind-driven resuspension on residence islands in the Pacific).29

Models to represent the effect of inefficient showering developed in this report indicate 

that this effect can be important in estimating doses to skin in many cases, even when showering 

is assumed to be more efficient in removing radioactive contamination from skin than normal 

showering. The importance of the dose received after the time of the first shower relative to the 

dose received before the first shower increases as the time after a detonation when exposure to 

descending or resuspended fallout occurred increases, due to reductions in the rate of decrease of 

the activity of all radionuclides in fallout combined with increasing time after a detonation, and 

increases as the time between deposition on skin and the first shower decreases. At times shortly 

after a detonation, when doses from dermal contamination could be relatively high, calculations 

indicate that inefficient showering may increase doses to skin by less than a factor of two, 

whereas at times long after a detonation, when doses from dermal contamination would be 

relatively low, the increase in doses due to inefficient showering could be much higher (e.g., 

about an order of magnitude, depending on the time between deposition and the first shower). 

Doses to skin from exposure to the beta-emitting radionuclides on the body surface are 

estimated using published dose-rate factors for specific radionuclides that apply at a depth below 

the body surface of 7 mg cm–2. Those dose-rate factors are applied to mixtures of radionuclides 

in fallout and are adjusted to account for different thicknesses of the epidermis in various regions 

 

29 Dermal contamination by deposition of resuspended material can be modeled as an acute event in cases 

of exposure of forward observers at NTS to large particles in fallout that was resuspended by the blast 

wave produced in a nuclear detonation, when material is immediately lofted into the air and large 

particles, which carried most of the activity, fell rapidly to Earth (see Section 3.3.4). Prolonged exposures 

of forward observers to smaller resuspended particles that may have remained airborne for times on the 

order of hours can be modeled by assuming continuous deposition.

141
of the body. Other effects that are taken into account in estimating dose-rate factors include 

reductions in doses from electrons due to shielding provided by particles to which radionuclides 

are attached or by clothing on which radionuclides are deposited and reductions in doses due to 

neglect of backscattering in air in the published dose-rate factors. 

Dose-rate factors for important alpha-emitting radionuclides in fallout were calculated in 

this report on the basis of a published dosimetry model. Although dose-rate factors for alpha 

emitters usually are much higher than dose-rate factors for beta emitters when alpha particles are 

sufficiently energetic to irradiate cells in the basal layer, alpha doses to skin of military personnel 

are not expected to be important relative to doses from electrons when it is considered that 

activities of alpha emitters in fallout are much lower than the total activity of all beta emitters. 

This report presents example calculations of doses to skin from exposure to electrons 

emitted by radionuclides on the body surface in specific exposure scenarios at NTS and in the 

Pacific. Results of these calculations indicate that, for exposure to descending fallout or 

resuspended material, electron doses to skin from dermal contamination can be a significant and 

sometimes dominant contributor to the total dose to skin from all exposure pathways. 

As in all dose reconstructions, estimation of doses to skin from dermal contamination 

requires significant judgment by an analyst. While the modeling approaches are straightforward, 

the necessary parameters are not well known. Probability distributions and point estimates of 

parameters for a number of exposure situations believed to be important (and common) are 

recommended in this report. Different assumptions about parameter values may be needed for 

other exposure situations. 

142
8. REFERENCES

Anspaugh L.R., Shinn J.H., Phelps P.L., and Kennedy N.C. Resuspension and redistribution of 

plutonium in soils. Health Phys. 29:571–582; 1975. 

Anspaugh L.R., Simon S.L., Gordeev K.I., Likhtarev I.A., Maxwell R.M., and Skinkarev, S.M. 

Movement of radionuclides in terrestrial ecosystems by physical processes. Health Phys. 

82:669–679; 2002. 

Asset G. and Pury D. Deposition of wind-borne particles on human skin. A.M.A. Archives of 

Industrial Hygiene and Occupational Medicine 9(4):273–283; 1954. 

Barrett M., Goetz J., Klemm, J., McRaney, W., and Phillips, J. Low Level Dose Screen – 

CONUS Tests, DNA-TR-85-317. Science Applications International Corporation, McLean, 

Virginia; 1986. 

Barss N.M. Methods and Applications for Dose Assessment of Beta Particle Radiation, SAIC – 

001/2024. Science Applications International Corporation, McLean, Virginia; 2000 

(January). 

Barss N.M. and Weitz R.L. Reconstruction of external dose from beta radiation sources of 

nuclear weapon origin. Health Phys. 91:379–389; 2006. 

Black R.H. Some factors influencing the beta dosage to troops. Health Phys. 8:131–141; 1962. 

Boeniger M. A comparison of surface wipe media for sampling lead on hands. J. Occ. Environ. 

Hyg. 3:428–434; 2006. 

Brouwer D.H., Kroese R., and Van Hemmen J.J. Transfer of contaminants from surface to 

hands: experimental assessment of linearity of the exposure process, adherence to skin, and 

area exposed during fixed pressure and repeated contact with surfaces contaminated with a 

powder. Appl. Occ. Environ. Hyg. 14:231–239; 1999. 

Charles M.W. The biological bases of radiological protection criteria for superficial, low 

penetrating radiation exposure. Radiation Protection Dosimetry 14(2):79–90; 1986. 

Chepil W.S. Dynamics of wind erosion: I. Nature of movement of soil by wind. Soil Sci. 

60:305–320; 1945. 

Cross W.G., Freedman N.O, and Wong P.Y. Tables of Beta-Ray Dose Distributions in Water, 

AECL 10521. Chalk River Laboratories, Chalk River, Ontario, Canada; 1992. 

Decisioneering, Inc. Crystal Ball® 2000.2 User Manual. Decisioneering, Inc., Denver, 

Colorado; 2001. 

Driver J.H, Konz J.J., and Whitmyre G.K. Soil adherence to human skin. Bull. Environ. 

Contam. Toxicol. 43:814–820; 1989. 

Eatough J.P. Alpha-particle dosimetry for the basal layer of the skin and the radon progeny 218-

Po and 214-Po. Med. Phys. Biol. 42:1899–1911; 1997. 

Eckerman K.F. and Ryman J.C. External Exposure to Radionuclides in Air, Water, and Soil, 

Federal Guidance Report No. 12, EPA-402-93-081. Office of Radiation and Indoor Air, U.S. 

Environmental Protection Agency, Washington, DC; 1993. 

143
England T.R. and Rider B.F. Evaluation and Compilation of Fission Product Yields. Appendix 

A: Set A Yields Evaluated and Compiled for Los Alamos Report LA-UR-3106 (ENDF-349). 

Los Alamos National Laboratory, Los Alamos, New Mexico; 1994. 

Environmental Protection Agency (EPA). Exposure Factors Handbook, Volume 1. Office of 

Research and Development, U.S. Environmental Protection Agency, Washington, DC; 1997 

(August). 

Fish B.-R., Boyett R.H., Clark R.H., Thompson J.L., and Wilkie W.H. Jr. Environmental 

Studies: Radiological Significance of Nuclear Rocket Debris – Progress Report July 1-

December 31, 1964, ORNL-TM-1053. Oak Ridge National Laboratory, Oak Ridge, 

Tennessee; 1964 (April). 

Fogh C.L., Byrne M.A., Andersson K.G., Bell K.F., Roed J., Goddard A.-J.H., Vollmair D.V., 

and Hotchkiss S.A.M. Quantitative Measurement of Aerosol Deposition on Skin, Hair and 

Clothing for Dosimetric Assessment – Final report, Risø-r-1075 (en). Risø National 

Laboratory, Roskilde, Denmark; 1999 (June). 

Friedman W.J. Decontamination of synthetic radioactive fallout from the intact human skin. 

Industr. Hyg. J. 19(1):15–19; 1958. 

Garger E.K., Kashpur V., Belov G., Demchuk V., Tschiersch J., Wagenpfell F., Paretzke H.G., 

Besnus F., Hollander W., Martinez-Serrano J., and Vintersved I. Measurement of 

resuspended aerosol in the Chernobyl area. I. Discussion of instrumentation and estimation of 

measurement uncertainty. Radiat. Environ. Biophys. 36:139–148; 1997a. 

Garger E.K., Hoffman F.O., and Thiessen K.M. Uncertainty of the long-term resuspension 

factor. Atmos. Environ. 31(11):1647–1656; 1997b. 

Garger E.K., Paretzke H.G., and Tschiersch J. Measurement of resuspended aerosol in the 

Chernobyl area. III. Size distribution and dry deposition velocity of radioactive particles 

during anthropogenic enhanced resuspension. Radiat. Environ. Biophys. 37:201–208; 1998. 

Garland J.A. Resuspension of Particulate Material from Grass, Experimental Programme 1979–

1980, AERE-R 10106. Her Majesty’s Stationary Office (HMSO), London; 1982. 

Garland J.A., Pattenden N.J., and Playford K. Resuspension following Chernobyl. Pages 9–33 

in Modelling of Resuspension, Seasonality and Losses During Food Processing, First Report 

of the VAMP Terrestrial Working Group, IAEA-TECDOC-647. International Atomic 

Energy Agency, Vienna, Austria; 1992 (May). 

Glasstone S. and Dolan, P.J. (Eds). The Effects of Nuclear Weapons, 3rd edition. U.S. 

Department Defense and U.S. Department of Energy, Washington, DC; 1977. 

Harvey J.R. Alpha radiation, an external radiation hazard? Health Phys. 21:866–869; 1971. 

Healy J.W. A Proposed Interim Standard for Plutonium in Soils, LA-5483-MS. Los Alamos 

National Laboratory, Los Alamos, New Mexico; 1974. 

Hicks H.G. Calculation of the concentration of any radionuclide deposited on the ground by 

offsite fallout from a nuclear detonation. Health Phys. 42(5):585–600; 1982. 

144
International Commission on Radiation Units and Measurements (ICRU). Stopping Powers and 

Ranges for Protons and Alpha Particles, ICRU Report 49. International Commission on 

Radiation Units and Measurements, Bethesda, Maryland; 1993. 

International Commission on Radiological Protection (ICRP). Report of the Task Group on 

Reference Man, ICRP Publication 23. Pergamon Press, Oxford, UK; 1975. 

International Commission on Radiological Protection (ICRP). Recommendations of the 

International Commission on Radiological Protection, ICRP Publication 26. Ann ICRP 1(3); 

1977. 

International Commission on Radiological Protection (ICRP). Human Respiratory Tract Model 

for Radiological Protection, ICRP Publication 66. Ann. ICRP 24(1–3); 1994. 

Kocher D.C. A Radionuclide Decay Data Base—Index and Summary Tables, NUREG/CR1413, ORNL/NUREG-70. Oak Ridge National Laboratory, Oak Ridge, Tennessee; 1980. 

Kocher D.C., Apostoaei A.I., Henshaw R.W., Hoffman F.O., Schubauer-Berigan M.K., 

Stancescu D.O., Thomas B.A., Trabalka J.R., Gilbert E.S., and Land C.E. Interactive 

RadioEpidemiological Program (IREP): A web-based tool for estimating probability of 

causation/assigned share of radiogenic cancers. Health Phys. 95(1):119–147; 2008. 

Kocher D.C. and Eckerman K.F. Electron dose-rate conversion factors for external exposure of 

the skin from uniformly deposited activity on the body surface. Health Phys. 53(2):135–141; 

1987. 

Kocher D.C., Trabalka J., and Apostoaei A.I. Derivation of Effective Resuspension Factors in 

Scenarios for Inhalation Exposure Involving Resuspension of Previously Deposited Fallout 

by Nuclear Detonations at Nevada Test Site, DTRA-TR-09-15. Defense Threat Reduction 

Agency, Fort Belvoir, Virginia; 2009. 

Kochendorfer D.B. and Ulberg J.C. Human Exposure to Particulate Debris from Aerospace 

Nuclear Applications, USNRDL-TR-67-59. U.S. Naval Radiological Defense Laboratory, 

San Francisco, California; 1967. 

Land C., Gilbert E., Smith J.M., Hoffman F.O., Apostoaei I., Thoman B., and Kocher D.C. 

Report of the NCI-CDC Working Group to Revise the 1985 NIH Radioepidemiological 

Tables, NIH Publication No. 03-6387. U.S. Department of Health and Human Services, 

Washington D.C.; 2003. 

Landahl H.P. UCTL Informal report 9-4-1-23. University of Chicago Toxicity Laboratory, 

Medical Division, Chemical Warefare Services, U.S. Army; 1944 (December) (as cited by 

Asset and Pury 1954). 

Lee S.Y. and Tamura T. Distribution and characterization of radionuclides in soils from the 

Nevada Test Site. J. Environ. Qual. 10(2):234–239; 1981. 

Miller C.F. The Contamination Behavior of Fallout-like Particles Ejected by Volcano Irazu. 

Stanford Research Institute, Menlo Park California; 1966a (April). 

Miller C.F. Operation CENIZA-ARENA. The Retention of Fallout Particles from Volcan Irazu 

(Costa Rica) by Plants and People, Part One. Stanford Research Institute, Menlo Park, 

California; 1966b (January). 

145
Miller C.F. Operation CENIZA-ARENA. The Retention of Fallout Particles from Volcan Irazu 

(Costa Rica) by Plants and People, Part Two. Stanford Research Institute, Menlo Park, 

California; 1966c (December). 

Miller C.F. Operation CENIZA-ARENA. The Retention of Fallout Particles from Volcan Irazu 

(Costa Rica) by Plants and People, Part Three. Stanford Research Institute, Menlo Park, 

California; 1967 (December). 

Miller C.F. Some Properties of Radioactive Fallout: Tower Detonations Diablo and Shasta, URS 

757-3. URS Research Company, Burlingame, California; 1969 (August). 

Nair S.K., Miller, C.W., Thiessen K.M., Garger E.K., and Hoffman F.O. Modeling the 

resuspension of radionuclides in Ukrainian regions impacted by the Chernobyl accident. 

Health Phys. 72(1):77–85; 1997. 

NRC (National Research Council). A Review of the Dose Reconstruction Program of the 

Defense Threat Reduction Agency. The National Academies Press, Washington, DC; 2003. 

Sehmel G.A. Deposition and resuspension. Pages 533–583 in Randerson D. (ed), Atmospheric 

Science and Power Production, DOE/TIC-27601. U.S. Department of Energy, Washington, 

DC; 1984. 

Sehmel G.A. and Hodgson W.H. Predicted dry deposition velocities. Pages 399–419 in 

Engelmann R.J. and Sehmel G.A. (coordinators), Atmosphere-Surface Exchange of Gaseous 

Pollutants, Conf-740921. U.S. Energy Research and Development Administration, 

Washington, DC; 1976. 

Sharp R. and Chapman W.H. OPERATION CASTLE – Project 4.1 Addendum, WT-938. Naval 

Medical Research Institute, Bethesda, Maryland; 1957. 

Sheppard S.C. and Evenden W.G. Ecosystem processes. Contaminant enrichment and 

properties of soil adhering to skin. J. Environ. Qual. 23:604–613; 1994. 

Trabalka J.R. and Kocher D.C. Bounding Analysis of Effects of Fractionation of Radionuclides 

in Fallout on Estimation of Doses to Atomic Veterans, DTRA-TR-07-5. Defense Threat 

Reduction Agency, Fort Belvoir, Virginia; 2007 (May). 

Turner J.E. Atoms, Radiation and Radiation Protection, Second Edition. John Wiley & Sons, 

New York; 1995. 

Whitton J.T. New values for epidermal thickness and their importance. Health Phys. 24:1–8; 

1973. 

146
APPENDIX A 

ADDITIONAL DATA USED IN ESTIMATING DOSES TO SKIN 

FROM DERMAL CONTAMINATION 

147
148

A.1 Data on Soil Loading on Skin and Clothing 

This section summarizes data obtained in studies of accumulation and retention of soil 

particles on skin during various activities. These data provide estimates of the mass of soil 

retained per unit area of skin that can be used in estimating dermal contamination by processes 

other than deposition of descending or resuspended fallout (Section 3.4). An estimate of the 

specific activity of contaminated soil (μCi mg–1

soil) then can be used to estimate an activity 

concentration on skin (μCi cm–2

skin). 

Various studies in which accumulation of soil on skin of human subjects was estimated 

are summarized in Table A-1. Measurements of soil loading on skin (mgsoil cm–2

skin) obtained 

from those studies are given in Table A-2. 

Estimates of average soil loadings on skin and clothing of military personnel who 

performed combat crawling through areas with bare soil and dry clipped grass are provided in 

Table A-3, and information on the variability of measured soil loadings in the same study are 

provided in Tables A-4 and A-5. 
Radiation Doses to Skin 

from Dermal Contamination 

149 

Table A-1. Summary of studies to estimate soil loading on skin resulting from various activities 

Activity Month Duration (h) Na Males Females Age Conditions 

Indoor Tae Kwon Do Feb. 1.5 7 6 1 8–42 Carpeted floor All i

unifo

Greenhouse Workers Mar. 5.25 2 1 1 37–39 Plant watering, spraying, soil blending, 

sterilization 

Long no g

Indoor Kids No. 1 Jan. 2 4 3 1 6–13 Playing on carpeted floor 3 of 

sock

Indoor Kids No. 2 Feb. 2 6 4 2 3–13 Playing on carpeted floor 5 of 

sock

Outdoor 

Daycare Kids No. 1a Aug. 3.5 6 5 1 1–6.5 Indoors: linoleum surface; outdoors: 

grass, bare earth, barked area 

4 of shoe

Day Daycare Kids No. 1b Aug. 4 6 5 1 1–6.5 Indoors: linoleum surface; outdoors: 

grass, bare earth, barked area 

4 of shoe

Daycare Kids No. 2c Sept. 8 5 4 1 1–4 Indoors, low napped carpeting, linoleum 

surfaces 

4 of bare

Daycare Kids No. 3 Nov. 8 4 3 1 1–4.5 Indoors: linoleum surface, outside: grass, 

bare earth, barked area 

All land 

Soccer No. 1 Nov. 0.67 8 8 0 13–15 Half grass-half bare earth 6 of 

shor

Soccer No. 2 Mar. 1.5 8 0 8 24–34 All-weather field (sand-ground tires) All i

sock

Soccer No. 3 Nov. 1.5 7 0 7 24–34 All-weather field (sand-ground tires) All i

sock

Groundskeepers No. 1 Mar. 1.5 2 1 1 29–52 Campus grounds, urban horticulture 

center, arboretum 

All i

Groundskeepers No. 2 Mar. 4.25 5 3 2 22–37 Campus grounds, urban horticulture 

center, arboretum 

All i

Groundskeepers No. 3 Mar. 8 7 5 2 30–62 Campus grounds, urban horticulture 

center, arboretum 

All i

Groundskeepers No. 4 Aug. 4.25 7 4 3 22–38 Campus grounds, urban horticulture 

center, arboretum 

5 of of gl

Groundskeepers No. 5 Aug. 8 8 6 2 19–64 Campus grounds, urban horticulture 

center, arboretum 

5 of of gl

Landscape/Rockery June 9 4 3 1 27–43 Digging (manual and mechanical), rock 

moving 

All lboot

Irrigation Installers Oct. 3 6 6 0 23-41 Landscaping, surface restoration All i

sleev

Table is continued on following page. 
Radiation Doses to Skin 

from Dermal Contamination 

150 

Table A-1. Summary of studies to estimate soil loading on skin resulting from various activities (EPA 

Activity Month Duration (h) Na Males Females Age Conditions 

Gardeners No. 1 Aug. 4 8 1 7 16–35 Weeding, pruning, digging a trench 6 of 

sleevglov

Gardeners No. 2 Aug. 4 7 2 5 26–52 Weeding, pruning, digging a trench, 

picking fruit, cleaning 

3 of sleev

Rugby No. 1 Mar. 1.75 8 8 0 20–22 Mixed grass-bare wet field All i

sock 

Rugby No. 2 July 2 8 8 0 23–33 Grass field (80% of time) and all-weather 

field (mix of gravel, sand, and clay) (20% of time) 

All iof 8 

Rugby No. 3 Sept 2.75 7 7 0 24–30 Compacted , mixed grass and bare earth 

field 

All ssleev

Archeologists July 11.5 7 3 4 16–35 Digging with trowel, screening dirt, 

sorting 

6 of shoe

Construction Workers Sept. 8 8 8 0 21–30 Mixed bare earth and concrete surfaces, 

dust and debris 

5 of and 

Utility Workers No. 1 July 9.5 5 5 0 24–45 Cleaning, fixing mains, excavation 

(backhoe and shovel) 

All lglov

Utility Workers No. 2 Aug. 9.5 6 6 0 23–44 Cleaning, fixing mains, excavation 

(backhoe and shovel) 

All lboot

Equip. Operators No. 1 Aug. 8 4 4 0 21–54 Earth scraping with heavy machinery, 

dusty conditions 

All lboot

Equip. Operators No. 2 Aug. 8 4 4 0 21–54 Earth scraping with heavy machinery, 

dusty conditions 

All lboot

Farmers No. 1 May 2 4 2 2 39–44 Manual weeding, mechanical cultivation All i

shirt

Farmers No. 2 July 2 6 4 2 18–43 Manual weeding, mechanical cultivation 2 of 

sleev

Reed gatherers Aug. 2 4 0 4 42–67 Tidal flats 2 of 

all w

Kids-in mud No. 1 Sept 0.17 6 5 1 9–14 Lake shoreline All i

Kids in mud No. 2 Sept. 0.33 6 5 1 9–14 Lake shoreline All i

a Number of subjects. 
Table A-2. Estimates of soil loading on skin in different body regions 

resulting from various activities (EPA 1997) 

Soil loading (mg cm–2) 

Geometric mean (geometric standard deviation) 

Activity Na Hands Arms Legs Face Feet 

Indoor 

Tae Kwon Do 7 0.0063 

(1.9) 

0.0019 

(4.1) 

0.0020 

(2.0) 

0.0022 

(2.1) 

Greenhouse Workers 2 0.043 0.0064 0.0015 0.0050 

Indoor Kids No. 1 4 0.0073 

(1.9) 

0.0042 

(1.9) 

0.0041 

(2.3) 

0.012 

(1.4) 

Indoor Kids No. 2 6 0.014 

(1.5) 

0.0041 

(2.0) 

0.0031 

(1.5) 

0.0091 

(1.7) 

Daycare Kids No. 1a 6 0.11 

(1.9) 

0.026 

(1.9) 

0.030 

(1.7) 

0.079 

(2.4) 

Daycare Kids No. 1b 6 0.15 

(2.1) 

0.031 

(1.8) 

0.023 

(1.2) 

0.13 

(1.4) 

Daycare Kids No. 2 5 0.073 

(1.6) 

0.023 

(1.4) 

0.011 

(1.4) 

0.044 

(1.3) 

Daycare Kids No. 3 4 0.036 

(1.3) 

0.012 

(1.2) 

0.014 

(3.0) 

0.0053 

(5.1) 

Outdoor 

Soccer No. 1 8 0.11 

(1.8) 

0.011 

(2.0) 

0.031 

(3.8) 

0.012 

(1.5) 

Soccer No. 2 8 0.035 

(3.9) 

0.0043 

(2.2) 

0.014 

(5.3) 

0.016 

(1.5) 

Soccer No. 3 7 0.019 

(1.5) 

0.0029 

(2.2) 

0.0081 

(1.6) 

0.012 

(1.6) 

Groundskeepers No. 1 2 0.15 0.005 0.0021 0.018 

Groundskeepers No. 2 5 0.098 

(2.1) 

0.0021 

(2.6) 

0.0010 

(1.5) 

0.010 

(2.0) 

Groundskeepers No. 3 7 0.030 

(2.3) 

0.0022 

(1.9) 

0.0009 

(1.8) 

0.0044 

(2.6) 

0.0040 

Groundskeepers No. 4 7 0.045 

(1.9) 

0.014 

(1.8) 

0.0008 

(1.9) 

0.0026 

(1.6) 

0.018 

-- 

Groundskeepers No. 5 8 0.032 

(1.7) 

0.022 

(2.8) 

0.0010 

(1.4) 

0.0039 

(2.1) 

Landscape/Rockery 4 0.072 

(2.1) 

0.030 

(2.1) 

0.0057 

(1.9) 

Irrigation Installers 6 0.19 

(1.6) 

0.018 

(3.2) 

0.0054 

(1.8) 

0.0063 

(1.3) 

Table is continued on following page.

151 
Table A-2. Estimates of soil loading on skin in different body regions 

resulting from various activities (EPA 1997) (continued) 

Soil loading (mg cm–2) 

Geometric mean (geometric standard deviation) 

Activity Na Hands Arms Legs Face Feet 

Gardeners No. 1 8 0.20 

(1.9) 

0.050 

(2.1) 

0.072 

-- 

0.058 

(1.6) 

0.17 

-- 

Gardeners No. 2 7 0.18 

(3.4) 

0.054 

(2.9) 

0.022 

(2.0) 

0.047 

(1.6) 

0.26 

-- 

Rugby No. 1 8 0.40 

(1.7) 

0.27 

(1.6) 

0.36 

(1.7) 

0.059 

(2.7) 

Rugby No. 2 8 0.14 

(1.4) 

0.11 

(1.6) 

0.15 

(1.6) 

0.046 

(1.4) 

Rugby No. 3 7 0.049 

(1.7) 

0.031 

(1.3) 

0.057 

(1.2) 

0.020 

(1.5) 

Archeologists 7 0.14 

(1.3) 

0.041 

(1.9) 

0.028 

(4.1) 

0.050 

(1.8) 

0.24 

(1.4) 

Construction Workers 8 0.24 

(1.5) 

0.098 

(1.5) 

0.066 

(1.4) 

0.029 

(1.6) 

Utility Workers No. 1 5 0.32 

(1.7) 

0.20 

(2.7) 

0.10 

(1.5) 

Utility Workers No. 2 6 0.27 

(2.1) 

0.30 

(1.8) 

0.10 

(1.5) 

Equip. Operators No. 1 4 0.26 

(2.5) 

0.089 

(1.6) 

0.10 

(1.4) 

Equip. Operators No. 2 4 0.32 

(1.6) 

0.27 

(1.4) 

0.23 

(1.7) 

Farmers No. 1 4 0.41 

(1.6) 

0.059 

(3.2) 

0.0058 

(2.7) 

0.018 

(1.4) 

Farmers No. 2 6 0.47 

(1.4) 

0.13 

(2.2) 

0.037 

(3.9) 

0.041 

(3.0) 

Reed gatherers 4 0.66 

(1.8) 

0.036 

(2.1) 

0.16 

(9.2) 

0.63 

(7.1) 

Kids-in mud No. 1 6 35 

(2.3) 

11 

(6.1) 

36 

(2.0) 

24 

(3.6) 

Kids in mud No. 2 6 58 

(2.3) 

11 

(3.8) 

9.5 

(2.3) 

6.7 

(12.4) 

a

 Number of subjects. 

152 
Table A-3. Average soil loading on skin and clothing of fully 

equipped military personnel while performing combat 

crawling in different environments (Black 1962) 

Mass loading (mg cm–2) 

Bare soil Clipped dry grass 

Location Skin Clothes Skin Clothes 

Neck, side 0.05 0.6 0.04 0.6 

Neck, back 0.05 4 0.04 0.9 

Wrist 0.1 1 0.1 2 

Inside elbow 0.04 0.5 0.02 0.4 

Below armpit 0.02 0.5 0.01 0.5 

Chest 0.03 1 0.04 1 

Back 0.04 5 0.02 1 

Belt, front 0.03 5 0.03 2 

Belt, back 0.01 1 0.01 0.6 

Groin 0.04 5 0.02 2 

Ankle 0.01 0.5 0.01 0.4 

Knee ---- 13 ---- 5 

Elbow ---- 8 ---- 1 

Geometric mean 0.031 1.4a 0.024 0.9a 

a

 Mass loadings on elbow and knee were not used in estimating 

geometric mean of loading on clothing, because elbows and knees 

support the body during combat crawling and, thus, clothing in those 

areas is more heavily loaded with soil than clothing in other areas. 

153 
Table A-4. Variability of soil loading on skin (mg cm–2) of fully equipped military personnel 

while performing combat crawling in different environments (Black 1962) 

Bare soil 

250 fta 

Bare soil 

500 fta 

Clipped grass 

250 fta 

Clipped grass 

500 fta 

Median GSD Median GSD Median GSD Median GSD 

Neck, side 0.062 4.0 0.034 2.0 0.023 3.0 0.081 2.1 

Neck, back 0.062 1.9 0.052 2.1 0.024 5.0 0.13 4.6 

Wrist, left 0.124 2.4 0.124 2.4 0.065 1.5 0.20 3.4 

Wrist, right 0.078 3.0 0.093 2.3 0.065 2.3 0.30 5.0 

Inside elbow, left 0.055 2.6 0.023 1.7 0.016 2.3 0.037 2.4 

Inside elbow, right 0.055 2.4 0.029 2.8 0.014 2.2 0.063 4.4 

Below armpit, left 0.022 2.5 0.012 1.6 0.009 1.7 0.025 4.4 

Below armpit, right 0.023 2.1 0.010 1.5 0.008 2.3 0.024 3.4 

Chest 0.033 1.8 0.023 1.8 0.023 2.1 0.095 4.0 

Back 0.046 2.3 0.037 2.5 0.016 3.3 0.031 3.2 

Belt, front 0.039 3.3 0.018 2.6 0.022 3.4 0.179 16.6 

Belt, back 0.013 1.9 0.009 2.3 0.005 3.2 0.016 2.9 

Groin, left 0.034 2.5 0.049 1.6 0.016 2.8 0.069 6.0 

Groin. Right 0.034 1.9 0.055 2.1 0.020 2.9 0.066 5.2 

Ankle, left 0.015 1.8 0.007 1.6 0.006 2.6 0.019 3.3 

Ankle, right 0.015 2.3 0.010 1.5 0.005 1.5 0.017 3.7 

a

 Type of terrain and length of combat crawling. 

154 
Table A-5. Variability of soil loading on clothing (mg cm–2) of fully equipped military 

personnel while performing combat crawling in different environments (Black 1962) 

Bare soil 

250 fta 

Bare soil 

500 fta 

Clipped grass 

250 fta 

Clipped grass 

500 fta 

Central GSD Central GSD Central GSD Central GSD 

Neck, side NAb NA 0.64 3.01 0.51 2.19 0.90 2.53 

Neck, back NA NA 3.45 3.21 0.68 2.53 1.53 2.44 

Wrist, left NA NA 0.68 4.28 1.53 2.07 1.96 2.93 

Wrist, right NA NA 0.72 4.27 1.53 1.84 2.09 1.51 

Inside elbow, left NA NA 0.81 2.19 0.24 4.22 0.68 1.55 

Inside elbow, right NA NA 0.36 3.69 0.34 2.13 0.73 1.70 

Below armpit, left NA NA 0.30 3.64 0.40 2.01 0.52 1.93 

Below armpit, right NA NA 0.57 1.59 0.45 1.79 0.81 1.75 

Chest NA NA 1.08 1.64 1.08 2.85 1.84 2.36 

Back NA NA NA NA 0.68 2.93 NA NA 

Belt, front NA NA 3.26 3.39 1.93 4.03 1.92 3.42 

Belt, back NA NA 1.15 3.29 0.43 2.68 0.86 1.99 

Groin, left NA NA 3.87 1.50 1.62 3.38 2.11 1.65 

Groin. Right NA NA NA NA 2.05 2.39 2.05 1.42 

Ankle, left NA NA 0.86 1.79 0.48 2.19 0.73 3.04 

Ankle, right NA NA 0.68 2.19 0.30 2.76 NA NA 

a

 Type of terrain and length of combat crawling. 

b

 NA – not available; data could not be read from copy of graphs from Black (1962). 

155 
156 

A.2 Surface Area of Skin 

To estimate interception and retention fractions (r) of particles incident on the body 

surface using results of the volcanic ash studies in Costa Rica, estimates of the surface area of the 

region of skin on which dermal contamination was assessed are needed [Section 3.2, eq. (3-3)]. 

This section provides data on the surface area of the total body and specific body regions. 

ICRP Publication 23 (ICRP 1975) recommends a reference total surface area of the body 

of 18,000 cm2

 for adult males and 16,000 cm2 for adult females. Rough estimates of the surface 

area in other regions of the body can be obtained by applying the “rule of nines.” According to 

this rule, the head and neck represent 9% of the total surface area, upper limbs represent 9% 

each, lower limbs 18% each, and the front and the back of the trunk 18% each. The perineum 

and the outstretched palm and fingers each represent 1% of the total body area. 

Studies to estimate the surface area of skin are reviewed in EPA’s Exposure Factors 

Handbook (EPA 1997). EPA’s findings indicate a total surface area of 19,400 cm2

 for adult 

males and 16,900 cm2

 for adult females. Data on population-averaged surface areas in different 

regions of the body for adults are provided in Table A-6, and percentages of the total surface area 

for these regions are provided in Table A-7. 

The surface area of the whole body can be customized for a given individual using that 

individual’s height and weight: 

 (A-1) 1 2

0 aa  wHaSA

where 

SA = surface area of total body (m2) 

H = height (cm), 

w = weight (kg), and 

a0, a1, a2 = empirical coefficients. 

Values of the coefficients a0, a1, and a2 recommended by various investigators are given in 

Table A-8. Once the surface area of the total body is estimated, the surface area of various 

regions of the body can be estimated using the percentages in Table A-7. 
Radiation Doses to Skin 

from Dermal Contamination 

Table A-6. Surface area of various body regions (m2) in adults (EPA 1997) 

Males Females 

N Mean a SDb Min. Max. Na Mean SDb Min. 

Head 32 0.118 0.0160 0.090 0.161 57 0.110 0.00625 0.0953 Trunk incl. neck 

32 0.569 0.104 0.306 0.893 57 0.542 0.0712 0.437 

Upper extremities 

48 0.319 0.0461 0.169 0.429 57 0.276 0.0241 0.215 

 Arms 32 0.228 0.0374 0.109 0.292 13 0.210 0.0129 0.193  Upper arms 6 0.143 0.0143 0.122 0.156 - - - -  Forearms 6 0.114 0.0127 0.0945 0.136 - - - -  Hands 32 0.084 0.0127 0.0596 0.113 12 0.0746 0.00510 0.0639 Lower extremities 

48 0.636 0.0994 0.283 0.868 57 0.626 0.0675 0.492 

 Legs 32 0.505 0.0885 0.221 0.656 13 0.488 0.0515 0.423  Thighs 32 0.198 0.1470 0.128 0.403 13 0.258 0.0333 0.258  Lower legs 32 0.207 0.0379 0.093 0.296 13 0.194 0.0240 0.165  Feet 32 0.112 0.0177 0.0611 0.156 13 0.0975 0.00903 0.0834 TOTAL 1.94c 0.00374 1.66d 2.28d 1.69c 0.00374 1.45d 

a Number of observations. b Standard deviation. c Median. d 5th and 95th percentiles. 

157 
Radiation Doses to Skin 

from Dermal Contamination 

158 

Table A-7. Percent of total body surface area in various body regions in adults (EPA 1997

Males Females 

N Mean a SDb Min. Max. Na Mean SDb Min. 

Head 32 7.8 1.0 6.1 10.6 57 7.1 0.6 5.6 Trunk (incl. neck) 

32 35.9 2.1 30.5 41.4 57 34.8 1.9 32.8 

Upper extremities 

48 18.8 1.1 16.4 21.0 57 17.9 0.9 15.6 

 Arms 32 14.1 0.9 12.5 15.5 13 14.0 0.6 12.4  Upper arms 6 7.4 0.5 6.7 8.1 - - - -  Forearms 6 5.9 0.3 5.4 6.3 - - - -  Hands 32 5.2 0.5 4.6 7.0 12 5.1 0.3 4.4 Lower extremities 

48 37.5 1.9 33.3 41.2 57 40.3 1.6 36.0 

 Legs 32 31.2 1.6 26.1 33.4 13 32.4 1.6 29.8  Thighs 32 18.4 1.2 15.2 20.2 13 19.5 1.1 18.0  Lower legs 32 12.8 1.0 11.0 15.8 13 12.8 1.0 11.4  Feet 32 7.0 0.5 6.0 7.9 13 6.5 0.3 6.0 

a Number of observations. b Standard of deviation. 
Table A-8. Coefficients in empirical model to estimate surface area of total body 

based on individual’s height and weighta

Study No. of 

persons

a0 a1 a2

SA Reference 

Man (cm2

)

b 

All ages 

 DuBois and DuBois (1916) 9 0.00718 0.725 0.425 18,100 

 Boyd (1935) 231 0.0179 0.500 0.484 18,200 

 Haycock et al. (1978) 81 0.0243 0.396 0.538 18,300 

 Gehan and George (1970) 401 0.0235 0.422 0.515 18,300 

Adults of age  20 

 Gehan and George (1970) 30 0.0155 0.545 0.463 18,100 

a

 Coefficients are used in eq. (A-1). 

b

 Surface area of total body for ICRP’s Reference Man (ICRP 1975) of weight 70 kg and height 170 cm 

estimated using eq. (A-1) and coefficients in this table. 

159 
A.3 Resuspension Factors 

This section presents a summary of measured resuspension factors that are relevant to 

estimation of doses to skin from dermal contamination and contamination of clothing following 

resuspension of radionuclides from the ground surface. Resuspension factors associated with 

mechanical stresses are summarized in Table A-9, and resuspension factors associated with 

winds are summarized in Table A-10. All data in these tables were obtained at sites where 

nuclear weapons were tested. 

160 
Table A-9. Summary of resuspension factors associated with mechanical stresses 

at sites where nuclear weapons were testeda

Location Source 

material Resuspension stressb Resuspension factor (m–1) 

Maralinga, 

Australiac 

Fallout Road survey at 1–2 days 

Cab of landrover, 5th hour 

Cab of landrover, 18th hourd

 

1  10–8 – 2  10–6

6.4  10–5

2.5  10–5

Uranium Dust stirred, height of 0.3 m 1  10–3 

Plutonium Vehicle dust, height of 0.3 me 

Pedestrian dust, height of 0.3 m 

3  10–4 – 7  10–4

1.5  10–6 – 3  10–4

Nevada Test Sitef

 Plutonium Extensive vehicular traffic 7  10–5

Monte Bello 

Islands, Australiac 

Fallout Road survey from back of 

landrover 

4th day 

7th dayg

At tail board 

7th day 

8  10–7 – 3  10–5

6  10–7 – 4  10–6

1.6  10–5 – 3.1  10–5 

Australian desert, 

“Totem”, 1953c 

Fallout Walking survey 

Vehicle survey, at tailboard 

3  10–7

2  10–6

a

 Data obtained from summary of measurements given in Table 12.9 of Sehmel (1984), except as noted. 

b

 Reported times are times after detonation that produced fallout for which resuspension factor was 

measured. 

c

 Measurements reported by Stewart (1967). 

d

 Time after detonation of 8 hours reported by Sehmel (1984) appears to be erroneous. e

 Lower bound of resuspension factor is value given by Stewart (1967); value reported by Sehmel (1984) 

is 3 × 10–7 m–1. f

 Measurement reported by Langham (1971). 

g

 Lower bound of resuspension factor is value given by Stewart (1967); value reported by Sehmel (1984) 

is 7 × 10–7 m–1. 

161 
Table A-10. Summary of resuspension factors associated with winds 

at sites where nuclear weapons were testeda

Location Source 

material Wind conditions Resuspension factor (m–1) 

Maralinga, 

Australiab 

Uranium Wind speed < 5 m s-1

Height of 0.3 m 

Height of 0.6 m 

3  10–4

1  10–5

Monte Bello 

Islands, Australia; 

hurricane trialsb 

Fallout Wind speed < 5 m s-1

16-m source, lightly 

vegetated sand and rockc

Near tower shotd 

Near road, no disturbance 

1  10–6 – 8  10–5

1  10–8 – 1  10–6

1  10–8 – 1.5  10–6 

Nevada Test Site, 

GMXe

Plutonium Wind speed not specified 

Near center 

Near edge 

3  10–10

2  10–9

Nevada Test Sitef Plutonium Wind speed not specified 

Dusty rural air 7  10–6 

Nevada Test Siteg 181W Wind speed not specified 10–7 – 6  10–5 

a

 Data obtained from summary of measurements given in Table 12.7 of Sehmel (1984), except as noted. 

b

 Measurements reported by Stewart (1967). 

c

 Upper bound of resuspension factor is value given by Stewart (1967); value reported by Sehmel (1984) 

is 1 × 10–5 m–1. d

 Upper bound of resuspension factor is value given by Stewart (1967); value reported by Sehmel (1984) 

is 2 × 10–7 m–1. e

 Measurements reported by Anspaugh (1975). 

f

 Measurements reported by Langham (1971). 

g

 Measurements reported by Anspaugh (1970).

162 
A.4 References 

Anspaugh L.R., Phelps P.L., Holladay G., and Hamby K.O. Distribution and redistribution of 

airborne particulates from the Schooner cratering event. Pages 428–446 in Proceedings of 

the Fifth Annual Health Physics Society Midyear Topical Symposium, Volume 2. Health 

Physics Society, McLean, Virginia; 1970. 

Anspaugh L.R., Shinn J.H., Phelps, P.L., and Kennedy N.C. Resuspension and redistribution of 

plutonium in soils. Health Phys. 29:571–582; 1975. 

Black R.H. Some factors influencing the beta dosage to troops. Health Phys. 8:131–141; 1962. 

Boyd E. The Growth of the Surface Area of the Human Body. University of Minnesota Press, 

Minneapolis, Minnesota; 1935. 

Dubois D. and Dubois E.F. A formula to estimate the approximate surface area if height and 

weight are known. Arch. Intern. Med. 17:863–871; 1916. 

Environmental Protection Agency (EPA). Dermal. Chapter 6 in Exposure Factors Handbook, 

Volume 1. Office of Research and Development, U.S. Environmental Protection Agency, 

Washington, DC; 1997 (August). 

Gehan E. and George G.I. Estimation of human body surface area from height and weight. 

Cancer Chemother. Rep. 54:225–235; 1970. 

Haycock G.B., Schwartz G.J., and Wisotsky D.H. Geometric method for measuring body 

surface are: A height-weight formula validated in infants, children and adults. J. Ped. 

93(1):301–308; 1978. 

International Commission on Radiological Protection (ICRP). Report of the Task Group on 

Reference Man, ICRP Publication 23. Pergamon Press, Oxford, UK; 1975. 

Langham, W.H. Plutonium distribution as a problem in environmental science. Page 9 in 

Fowler, E.B., Henderson, R.W., and Milligan, M.F. (Eds.), Proceedings of Environmental 

Plutonium Symposium, LA-4756, Los Alamos Scientific Laboratory, Los Alamos, New 

Mexico; 1971. 

Sehmel G.A. Deposition and resuspension. Pages 533–583 in Randerson D. (ed), Atmospheric 

Science and Power Production, DOE/TIC-27601. U.S. Department of Energy, Washington, 

DC; 1984. 

Stewart, K. The resuspension of particulate material from surfaces. Pages 63–74 in Fish, B.-R. 

(ed.), Surface Contamination. Pergamon Press, New York; 1967. 

163 
APPENDIX B 

ALTERNATIVE APPROACH TO ESTIMATING DOSES 

TO SKIN FROM DERMAL CONTAMINATION 

BY RESUSPENDED MATERIAL 

164 
Section 3.3 presents an approach to estimating doses to skin from dermal contamination 

by resuspended material that uses a differential equation in which the rate of change of the 

activity concentration on skin is calculated as the rate at which radioactive material is deposited 

on skin per unit area minus the rate at which the deposited material is lost from skin. 

Analysts at SAIC30 developed an alternative approach to estimating doses to skin from 

dermal contamination that could be more easily implemented using Mathcad computer 

software.31 The alternative approach uses an integral equation rather than a differential equation. 

This appendix describes SAIC’s alternative approach. The particular approach presented below 

applies to deposition on skin of material resuspended by winds. As discussed in Section 3.3.3, 

the approach can be adapted to apply to resuspension by human activities by using a deposition 

velocity (VD) instead of the wind speed (VW). As indicated by the following derivation, SAIC’s 

alternative approach leads to the same equation for the total dose during and after deposition 

onto skin as was obtained in Section 3.3.2.2. 

In the integral-equation approach used by SAIC, the activity concentration of 

resuspended radionuclides that are deposited and retained on skin during an infinitesimal time 

interval (t, t+dt) is calculated as , where is the total activity 

concentration of all radionuclides in fallout on the ground surface at time T0 after a detonation 

when deposition of resuspended material onto skin begins, RF is the resuspension factor, VW is 

the wind speed, and ARf is the effective interception and retention fraction described in 

Section 3.2. The activity of radionuclides on skin during this time interval is assumed to decay 

with time as 

–x

, where  ≥ t and x is a constant. 

( )d 0

0

fW tARVRFTC xgs   0 Cgs

Contamination of skin by deposition of resuspended material is assumed to start at time 

T0, continue for a period Tdep, and cease at time Tdep. After deposition ceases, skin is assumed 

to remain contaminated for an additional post-deposition period Tpost until the next shower. 

Skin is assumed to be irradiated continuously for a period Tex = Tdep + Tpost, during which the 

dose rate can vary with time. Exposure is assumed to cease at time Tex = Tdep + Tpost.

 

30 Klemm J., personal communication (2004); Raine D., personal communication (December 2004). 

31 http://www.mathcad.com.

165 
The dose from decay of radioactive material deposited on skin is obtained by integrating 

the dose rate from the time of deposition (t) until the time of decontamination (Tex). Doses from 

all depositions that occur from the time deposition begins (T0) to the time deposition ceases (Tdep) 

are summed (i.e., integrated) to obtain a total dose: 

D   ARVRFTC DRF t (B-1) 

Tdep ex

T

T

t skin

x

fW

x

gs τ τdd 0

-

0

0

    

Equation (B-1) can be integrated to obtain: 

















  

 

 

 









 













 

)1(

)2(

0

0

)1(-)1(-

0

0

)1(-

0

0

-

0

0

0

0

0

0

0

)2x()1(

1

d

)1(

d

)1(

τ

ττ dd

x

ex

T

T

T

T

x

fW skin

x

gs

T

T

x

ex

x

fW skin

x

gs

T

T

T

t

x

fW skin

x

gs

T

T

T

t

x

fW skin

x

gs

Tt

t

x

DRFARVRFTC

t

x

Tt DRFARVRFTC

t

x

DRFARVRFTC

DRFARVRFTCD t

dep

dep

dep

dep

ex

dep ex

 (B-2) 

The resulting equation for the total dose is: 

 )2(

0

)1(

0

)2(

0

0

)()2(

)2)(1(

 





 

 

x x

dep ex

x

dep

fW skin

x

gs

T TTTTx

xx

DRFARVRFTC

D

 (B-3) 

The solution in eq. (B-3) represents the total dose received from the time deposition onto 

skin begins until contamination is assumed to be removed by showering. When the wind 

velocity, VW, is substituted for the deposition velocity, VD, and the units conversion factor of 0.36 

discussed following eq. (3-8) in Section 3.3.2.2, which is derived on the basis of assumed units 

for each parameter, is taken into account, this equation is identical to eq. (3-27) that was derived 

in Section 3.3.2.2 using a differential-equation approach. 

If decontamination (e.g., by showering) takes places at the time deposition ceases (i.e., 

Tdep = Tex), the solution represents the dose during the period of deposition. This solution, which 

is given in eq. (B-4) below, is to the same as eq. (3-19) in Section 3.3.2.2: 

166 
 )2(

0

)1(

0

)2(

0

0

)2()1(

)2)(1(

 





 

 

x x

dep

x

dep

fW skin

x

gs

dep

Tx TTTx

xx

DRFARVRFTC

D (B-4) 

Thus, the differential-equation approach presented in this report and the integral-equation 

approach used by SAIC produce identical results. A potential advantage of our approach is that 

it provides estimates of the activity concentration of radionuclides on skin as a function of time 

during the deposition period and after deposition ceases, and it provides separate estimates of 

doses to skin during the deposition period and after deposition ceases until decontamination. 

167 
APPENDIX C 

PARAMETER VALUES USED TO EVALUATE IMPORTANCE OF 

DOSES TO SKIN FROM DERMAL CONTAMINATION 

168 
Calculations summarized in Section 6 of the main report investigate conditions under 

which dermal contamination by beta-emitting radionuclides should be considered important in 

estimating the total dose to skin. That investigation involves a comparison of doses to skin from 

dermal contamination with doses from exposure to beta emitters on the ground surface in various 

exposure scenarios. If the dose to skin from dermal contamination in a given scenario is at least 

a substantial fraction of the dose from beta emitters on the ground surface, we consider that 

dermal contamination is an important contributor to the total dose to skin in that scenario. The 

evaluation in Section 6 does not take into account the potential importance of incomplete 

removal of radionuclides from skin by showering, which results in increases in dose from dermal 

contamination but does not affect doses from ground-surface exposure. 

Tables C-1 to C-6 provide point (deterministic) estimates of parameter values that were 

used in calculations to evaluate the importance of doses to skin from dermal contamination 

relative to doses from exposure to a contaminated ground surface in various scenarios in which 

dermal contamination results from descending fallout (Table C-1), resuspension by vehicular 

traffic (Table C-2), wind-driven resuspension (Tables C-3 and C-4), and resuspension by the 

blast wave or thermal pulse produced in a nuclear detonation (Tables C-5 and C-6). Calculations 

assume exposure at 2 days or 4 years after a detonation. Only in the scenario for wind-driven 

resuspension is there a difference in parameter values at the two times; all other time-dependent 

effects involve differences in the particular radionuclides that contribute significantly to doses 

from dermal contamination and ground-surface exposure. Calculations also assume exposure at 

locations near to and far from ground zero to investigate the effect of particle size. 

169 
Table C-1. Parameter values used to estimate doses to skin from 

exposure to descending fallouta

 

NTS, close to ground 

zero 

Pacific, far from 

ground zero 

Parameter name Symbol Units Face Arms Face Arms 

Interception and retention 

fraction 

r unitless 0.015 0.06 0.015 0.06 

Particle-size adjustment factor PSa unitless 1 1 1.3 1.3 

Enhancement due to moisture EM unitless 0.75 0.75 1.15 1.15 

Enrichment of specific activity EF unitless 2.0 2.0 1.3 1.3 

Activity-weight adjustment 

factor 

AW unitless 0.1 0.1 1 1 

Skin-depth modification factor SDMF unitless 1.3 0.9 1.3 0.9 

Time to first shower Tpost h 12 12 12 12 

Duration of exposure to 

radionuclides on ground surface 

Tground h 4 4 8 8 

a

 Deposition on skin is assumed to be acute event that occurs instantaneously. 

170 
Table C-2. Parameter values used to estimate doses to skin from exposure to 

radionuclides resuspended by vehicular traffica

NTS, close to 

ground zero 

Parameter name Symbol Units Face Arms 

Interception and retention fraction r unitless 0.015 0.06 

Particle-size adjustment factor PSa unitless 1.3 1.3 

Enhancement due to moisture EM unitless 0.75 0.75 

Enrichment of specific activity EF unitless 1.3 1.3 

Activity-weight adjustment factor AW unitless 1 1 

Skin-depth modification factor SDMF unitless 1.3 0.9 

Resuspension factor RF m–1 2  10–5 2  10–5

Deposition velocity VD m s–1 1 1 

Duration of deposition onto skin Tdep h 4 4 

Time to first shower Tpost h 8 8 

Duration of exposure to 

radionuclides on ground surface 

ground h 4 4 

a

 Exposure is assumed to occur while marching behind vehicles; parameter values 

apply at any time after a detonation. 

171 
Table C-3. Parameter values used to estimate doses to skin from exposure to radionuclides 

resuspended by winds at times shortly after detonationa

NTS, close to 

ground zero 

Pacific, far from 

ground zero 

Parameter name Symbol Units Face Arms Face Arms 

Interception and retention 

fraction 

r unitless 0.015 0.06 0.015 0.06 

Particle-size adjustment factor PSa unitless 1.3 1.3 1.3 1.3 

Enhancement due to moisture EM unitless 0.75 0.75 1.15 1.15 

Enrichment of specific activity EF unitless 1.3 1.3 1.3 1.3 

Activity-weight adjustment 

factor 

AW unitless 1 1 1 1 

Skin-depth modification factor SDMF unitless 1.3 0.9 1.3 0.9 

Resuspension factor RF m–1 1  10–6 1  10–6 1  10–6 1  10–6

Wind velocity VW m s–1 4 4 5 5 

Duration of deposition onto skin Tdep h 8 8 8 8 

Time to first shower Tpost h 4 4 4 4 

Duration of exposure to 

radionuclides on ground surface 

Tground h 8 8 8 8 

a

 Exposure is assumed to occur within a few days after a detonation. 

172 
Table C-4. Parameter values used to estimate doses to skin from exposure to radionuclides 

resuspended by winds at times long after detonationa

NTS, close to 

ground zero 

Pacific, far from 

ground zero 

Parameter name Symbol Units Face Arms Face Arms 

Interception and retention 

fraction 

r unitless 0.015 0.06 0.015 0.06 

Particle-size adjustment factor PSa unitless 1.3 1.3 1.3 1.3 

Enhancement due to moisture EM unitless 0.75 0.75 1.15 1.15 

Enrichment of specific activity EF unitless 1.3 1.3 1.3 1.3 

Activity-weight adjustment 

factor 

AW unitless 1 1 1 1 

Skin-depth modification factor SDMF unitless 1.3 0.9 1.3 0.9 

Resuspension factor RF m–1 3  10–8 3  10–8 3  10–8 3  10–8

Wind velocity VW m s–1 4 4 5 5 

Duration of deposition onto skin Tdep h 8 8 8 8 

Time to first shower Tpost h 4 4 4 4 

Duration of exposure to 

radionuclides on ground surface 

Tground h 8 8 8 8 

a

 Exposure is assumed to occur at times of a few years after a detonation. 

173 
Table C-5. Parameter values used to estimate doses to skin from exposure to radionuclides 

resuspended by blast wave in detonation at NTSa 

Forward observers 

(large particles only)

Forward observers 

and maneuver troops 

(small particles only)

Parameter name Symbol Units Face Arms Face Arms 

Interception and retention 

fraction 

R unitless 0.015 0.06 0.015 0.06 

Particle-size adjustment factor PSa unitless 0.8 0.8 1.3 1.3 

Enhancement due to moisture EM unitless 0.75 0.75 0.75 0.75 

Enrichment of specific activity EF unitless 2.5 2.5 1.3 1.3 

Activity-weight adjustment 

factor 

AW unitless 0.03 0.03 1 1 

Skin-depth modification factor SDMF unitless 1.3 0.9 1.3 0.9 

Resuspension factor RF m–1 1.0  10–5 1.0  10–5 1  10–7 1  10–7

Deposition velocity VD m s–1 1 1 

Height of cloud of resuspended 

material 

H m 30 30 

Duration of deposition onto skin Tdep h b b 2 2 

Time to first shower Tpost h 12 12 10 10 

Duration of exposure to 

radionuclides on ground surface 

Tground h 2 2 2 2 

a

 Parameter values apply at any time after a previous detonation. 

b

 Deposition of large particles is assumed to occur instantaneously. 

174 
Table C-6. Parameter values used to estimate doses to skin from 

exposure to radionuclides resuspended by 

thermal pulse in detonation at NTSa 

Maneuver troops 

(small particles only) 

Parameter name Symbol Units Face Arms 

Interception and retention 

fraction 

r unitless 0.015 0.06 

Particle-size adjustment factor PSa unitless 1.3 1.3 

Enhancement due to moisture EM unitless 0.75 0.75 

Enrichment of specific activity EF unitless 1.3 1.3 

Activity-weight adjustment 

factor 

AW unitless 1 1 

Skin-depth modification factor SDMF unitless 1.3 0.9 

Resuspension factor RF m–1 1  10–5 1  10–5

Deposition velocity VD m s–1 1 1 

Duration of deposition onto skin Tdep h 2 2 

Time to first shower Tpost h 10 10 

Duration of exposure to 

radionuclides on ground surface

Tground h 2 2 

a

 Parameter values apply at any time after a previous detonation. 

175 
APPENDIX D 

EFFECT OF INEFFICIENT SHOWERING ON DOSE TO 

SKIN FROM DERMAL CONTAMINATION – 

MODELING AND AVAILABLE DATA 

176 
This appendix presents information on the effect of inefficient showering on doses to skin 

from dermal contamination. Appendix D.1 presents a derivation of the model discussed in 

Section 3.5.2 to estimate dose from an acute deposition onto skin when showering does not 

remove all contamination from skin. Appendix D.2 presents and discusses data that can be used 

to estimate the fraction of the contamination on skin that is removed in the first and subsequent 

showers after an acute deposition. 

177 
D.1 Modeling of Effect of Inefficient Showering on Dose to 

Skin from Acute Dermal Contamination 

This appendix presents a derivation of eq. (3-33) in Section 3.5.2, which gives the total 

dose to skin from an acute deposition of a mixture of radionuclides in fallout, taking into account 

the effect of inefficient showering in removing contamination from skin. An acute deposition 

(e.g., fallout from a nuclear weapon detonation) occurs at time T0, the first shower occurs at time 

T1, and subsequent showers occur at times T2, T3, ..., TN. All times are specified in hours from 

the time of the detonation that produced the acute deposition on skin. Derivation of eq. (3-33) 

involves an iterative procedure in which the dose between successive showers and the total dose 

from the time of deposition to the time of a given shower is modeled. 

D.1.1 Period from T0 to T1

We first consider the dose to skin during the period from T0 (the time of an acute 

deposition on skin) to T1 (the time of the first shower). The activity concentration of 

radionuclides on skin due to an acute deposition at time T0 is estimated in accordance with 

eq. (3-2) (Section 3.2) as: 

    skin gs ARTCTC f   0 0 

Given this estimate of Cskin(T0), the concentration on skin immediately before the first shower at 

time T1 is estimated as: 

    xx

skin

before

skin TTTCTC 

1  100 

The first shower removes a fraction of the contamination on skin at time T1. This fraction 

is given by ( + ), where γ1 is the fraction removed by washing and β is the fraction removed 

by exfoliation of skin cells during the first shower. The parameter γ should be highest during the 

first shower and lower during each successive shower. The parameter β is assumed to be the 

same in all showers, and showering is assumed to be the only activity that removes a significant 

amount of contamination by exfoliation. The fraction of the contamination on skin at time T1

178 
that remains after the first shower then is  = [1 – (1 + )], and the concentration on skin 

immediately after the first shower at time T1 is estimated as: 

    xx

skin

after

skin TTTCTC  α11  100 

The dose received during the period from T0 to T1, as derived from eq. (3-6) 

(Section 3.2.2), is estimated as: 

 

   

1

1

)(

1

1

1

0

00

)1(

1

)1(

0

0

0

11



 



 



 



 



x

TT DRFTTC

x

TT DRFARTC

DTD

x x

skin

x

skin

x x

f skin

x

gs 

D.1.2 Period from T1 to T2

As derived in the previous section, the activity concentration of radionuclides on skin 

immediately after the first shower at time T1 is estimated as: 

    xx

skin

after

skin TTTCTC  α11  100 

Given this estimate of the concentration on skin immediately before the second 

shower at time T2 is estimated as: 

( ), TC 1

after

skin

   

 

  xx

skin

xxxx

skin

after xx

skin

before

skin

TTTC

TTTTTC

TTTCTC













1 200

1 21100

2 211

α

α 

The second shower removes a fraction of the contamination on skin at time T2 given by 

(2 + ), and the fraction of the contamination at that time that remains on skin after the second 

shower is  = [1 – (2 + )]. The concentration on skin immediately after the second shower at 

time T2 then is estimated as: 

    xx

skin

after

skin TC TTTC  αα 122  200 

The dose received during the period from T1 to T2 is estimated as: 

179 
 

 

  1

α

1

α

1 )(

)1(

2

)1(

1

1 00

)1(

2

)1(

1

1 1100

)1(

2

)1(

1

2 11



 



 



 

 



 



 



x

TT DRFTTC

x

TT DRFTTTTC

x

TT DRFTTCTD

x x

skin

x

skin

x x

skin

xxx

skin

x x

skin

after x

skin

 

Using the dose received during the period from T0 to T1 that was derived in the previous section, 

the dose received during the period from T0 to T2 then is estimated as: 

  

   

  

















  

 



  

 



   



 



 



1

α

1

T

1

α

1

)1(

2

)1(

1

1

)1(

1

)1(

0

00

)1(

2

)1(

1

1 00

)1(

1

)1(

0

00

2 1 2

x

TT

x

T DRFTTC

x

TT DRFTTC

x

TT DRFTTC

TDTDD

x x x x

skin

x

skin

x x

skin

x

skin

x x

skin

x

skin 

D.1.3 Period from T2 to T3

The effect of inefficient showering on the dose during the period from the second shower 

at time T2 to the third shower at time T3 can be modeled by analogy with modeling of the effect 

during the period from the first to the second shower. As derived in the previous section, the 

activity concentration of radionuclides on skin immediately after the second shower at time T2 is 

estimated as: 

    xx

skin

after

skin TC TTTC  αα 122  200 

Given this estimate of the concentration on skin immediately before the third shower 

at time T3 is estimated as: 

( ), TC 2

after

skin

   

 

  xx

skin

xxxx

skin

after xx

skin

before

skin

TTTC

TTTTTC

TTTCTC













12 300

12 32200

3 322

αα

αα 

The third shower removes a fraction of the contamination on skin at time T3 given by 

(3 + ), and the fraction of the contamination at that time that remains on skin after the third 

180 
shower is  = [1 – (3 + )]. The concentration on skin immediately after the third shower at 

time T3 then is estimated as: 

    xx

skin

after

skin TC TTTC  ααα 1233  300 

The dose received during the period from T2 to T3 is estimated as: 

 

 

  1

αα

1

αα

1 )(

)1(

3

)1(

2

12 00

)1(

3

)1(

2

12 2200

)1(

3

)1(

2

3 22



 



 



 

 



 



 



x

TT DRFTTC

x

TT DRFTTTTC

x

TT DRFTTCTD

x x

skin

x

skin

x x

skin

xxx

skin

x x

skin

after x

skin

 

Using equations derived in the previous two sections, the dose received during the period from 

T0 to T3 then is estimated as: 

  

   

 

  

















  

  

 



 

 

  

 



     



 



 



 



1

αα

1

α

1

T

1

αα

1

α

1

)(

)1(

3

)1(

2

12

)1(

2

)1(

1

1

)1(

1

)1(

0

00

)1(

3

)1(

2

12 00

)1(

2

)1(

1

1 00

)1(

1

)1(

0

00

2 1 2 3

x

TT

x

TT

x

T DRFTTC

x

TT DRFTTC

x

TT DRFTTC

x

TT DRFTTC

TDTDTDD

x x x x x x

skin

x

skin

x x

skin

x

skin

x x

skin

x

skin

x x

skin

x

skin

 

D.1.4 Period from TN–1 to TN

Finally, we consider the effect of inefficient showering on the dose during the period 

from the next-to-last shower at time TN–1 to the last shower at time TN. The activity 

concentration of radionuclides on skin is assumed to be negligible after the last shower. By 

analogy with previous derivations, the concentration on skin immediately after the next-to-last 

shower at time TN–1 is estimated as: 

    x

N

x

N N skin

after

skin TC TTTC 



  1 1  ααα 12 00  1 

181 
Given this estimate of the concentration on skin immediately before the last shower 

at time TN is estimated as: 

( ), N1

after

skin TC

   

 

  x

N

x

N skin

x

N

x

N

x

N

x

N skin

x

N

x

NN

after

N skin

before

kin

TTTC

TTTTTC

TTTCTCs

























 

1 12 00

1 12 00 11

11

ααα

ααα



 

The dose received during the period from TN–1 to TN is estimated as: 

 

 

  1

ααα

1

ααα

1 )(

)1()1(

1

1 12 00

)1()1(

1

1 12 00 11

)1()1(

1

11



 



 



  



 





 













 



x

TT DRFTTC

x

TT DRFTTTTC

x

TT DRFTTCTD

x

N

x

N

skin

x

N skin

x

N

x

N

skin

x

N

x

N

x

N skin

x

N

x

N

skin

x

NN

after

N skin



 

Using equations derived in the previous sections, the dose received during the period from T0 to 

TN (i.e., from the time of an acute deposition onto skin until the time of the last shower) then is 

estimated as: 

     

 











  

 













  

 

  







 

   



1

ααα

1

αα

1

α

1

)1()1(

1

1 12

)1(

3

)1(

2

12

)1(

2

)1(

1

1

)1(

1

)1(

x 0

00

1 2 3

x

TT

x

TT

x

TT

x

TT DRFTTC

TDTDTDTDD

x

N

x

N

N

x x

x x x x

skin skin

N N

 



Thus, the total dose, as given in eq. (3-33) (Section 3.5.2), is estimated as: 

    







 



































 

N

j

j

k

k

x

j

x

j

N skin skin

x

TT

DRFTTCD

1

1

1

)1()1(

x 1

00 α

1 

182 
D.2 Data on Removal of Skin Cells by Exfoliation and Efficiency of Washing in 

Removing Contamination from Skin

In models to represent the effect of inefficient showering on doses from dermal 

contamination developed in Section 3.5, contamination is assumed to be removed from skin by 

two processes: exfoliation of skin cells and washing (removal by soap and water). By assuming 

that exfoliation of skin cells occurs mainly as a result of scrubbing while showering, the fraction 

of the contamination that is removed per shower is represented by (β + γ), where β is the fraction 

removed by exfoliation of skin cells and γ is the fraction removed by washing. The fraction of 

the contamination that remains on skin after a shower then is estimated as α = [1 – (β + γ)]. This 

appendix presents data that can be used to estimate removal fractions of contamination from skin 

(fractions of contamination removed per shower) by the two processes. 

D.2.1 Data on Exfoliation of Skin Cells

Data on renewal times for cells in the epidermis were reviewed in ICRP Publication 23 

(ICRP 1975; Sections II.A.6.a and II.A.6.b). These data are assumed to represent turnover times 

of normal epidermal cells by exfoliation. Cell renewal times for the epidermis reported by ICRP 

(1975) include the following: 

Observed Renewal Times – 

 – Palms, 32–36 days; 

 – Upper Limbs, 17 days; 

 – Lower Limbs, 29–30 days. 

Calculated Renewal Times – 

 – Basal layer of scalp, 129 days; 

 – Abdominal skin of persons of age 0–20 y, 91 days; 

 – Abdominal skin of persons of age 21–40 y, 43 days. 

The available data for normal skin cells evidently are limited. We also note that a turnover time 

as low as 7 days is representative of skin afflicted with psoriasis (Cormack 1993). 

183 
D.2.2 Data on Efficiency of Washing in Removing Contamination from Skin

In implementing the models developed in Section 3.5, the fraction of the contamination 

on skin that is removed by washing per shower is assumed to be highest in the first shower and 

to decrease with each successive shower for the first few showers. This section discusses data 

from various studies that can be used to estimate the fractions of contamination on skin that are 

removed in the first shower and subsequent showers. Relevant studies investigated the 

efficiency of wiping, washing or showering in removing particulate material from skin. 

D.2.2.1 General Discussion of Data and Application to Modeling of Inefficient Showering

In all studies discussed in the following sections that investigated the amount (fraction) of 

contamination that was removed from skin by multiple wipes or washings, the amount removed 

in each wipe or washing was reported with respect to the amount of contamination on skin at the 

time of the first wipe or washing. Results in that form cannot be used directly in models 

developed in Section 3.5. The desired quantity for use in those models is the fraction of 

contamination on skin at the time of each shower that is removed at that time. This fraction is 

the parameter γj, where j denotes the jth shower in a succession of showers (j = 1, ..., N). In all 

showers after the first, γj does not depend on the amount of contamination on skin at the time of 

the first shower. In the following sections, results of removal studies are presented as reported, 

and those results are converted to estimates of γj that can be used in our models. 

Consider, for example, a hypothetical study in which 100 units of contamination were 

present on skin at the time of the first wipe or washing, and the amounts of contamination 

removed in three successive wipes or washings were 50, 20, and 5 units, respectively. Reported 

fractions of the initial contamination removed in each wipe or washing in this example would be 

0.50, 0.20, and 0.05. The sum of these fractions cannot exceed 1.0. Alternatively, the total 

(cumulative) amounts of contamination removed after each wipe or washing could be reported. 

In this case, these amounts, expressed as cumulative fractions of the initial contamination, would 

be 0.50, 0.70, and 0.75, where the cumulative fraction after the last wipe or washing cannot 

exceed 1.0. The corresponding fractions of contamination that was present at the time of each 

wipe or washing that was removed at that time, γj, in this example would be γ1 = 50/100 = 0.50, 

184 
γ2 = 20/50 = 0.40, and γ3 = 5/30 = 0.17. Again, these fractions are parameters that can be used in 

models developed in Section 3.5. The only constraint is that γj cannot exceed 1.0. 

D.2.2.2 Data from Study by Boeniger

Boeniger (2006) investigated the efficiency of commercially available surface-wipe 

media in removing lead dust on hands. That study involved four consecutive wipes of the palm 

of each hand for 30 s each after a simulated contamination with a mixture of lead oxide (PbO) 

dust and baby powder. All wipes were moist at the time of the first wipe, and moisture losses 

during the study were less than 10%. Low (200 g) and high (3,000 g) loadings of powder 

were applied over an area of about 1,060 cm2

. Sizes of dust particles were not reported. 

Fractions of the initial contamination that was removed by each wipe reported by 

Boeniger (2006) are given in Table D-1, and the corresponding estimates of the parameter γj

used in our models are given in Table D-2. About 52-63% of the total lead loading was removed 

from the palms with the first wipe, and up to about 75% removal was achieved after four 

successive wipes. The data on removal efficiencies of wipe media may not be representative of 

removal by showering, but they provide insight into the amount of dust that can be removed by 

wiping. Results indicate that the fraction of the initial dust loading removed by a first wipe is 

higher than the fraction removed by any subsequent wipe. The parameter γj used in our models 

also is seen to decrease in each successive wipe. 

D.2.2.3 Data from Study by Boeniger et al.

In an earlier study by Boeniger et al. (2005), about 3,000 g of lead oxide dust (PbO) was 

applied to the hands of a number of subjects, who then washed their hands once or twice, with or 

without rinse, with several commercial skin cleansers, including liquid soap and heavier 

industrial abrasive cleansers. A typical amount of lead that remained on the hands after washing 

was 400 g, or about 13% of the amount applied before washing; i.e., about 87% of the 

contamination was removed. The best-performing commercial product (Ivory Liquid Soap) 

removed about 98% of the initial lead contamination. 

185 
The study by Boeniger et al. (2005) involved rubbing of skin on the hands in one or two 

washings, which is likely to be more efficient in removing contamination than washing of skin 

on other parts of the body during normal showering. On parts of the body other than the hands, 

washing during a shower could be less efficient in removing contamination, because some areas 

are difficult to reach and showering sometimes involves mostly rinsing, with little application of 

soap or vigorous rubbing. 

D.2.2.4 Data from Study by Sharp and Chapman

Sharp and Chapman (1957) described efforts to decontaminate 82 native inhabitants of 

the Marshall Islands and some military personnel who were exposed to fallout from detonation 

of Operation CASTLE, Shot BRAVO on March 1, 1954. Sixteen of the 82 Marshallese were 

evacuated by airplane, and the others were evacuated by ship. After arriving at Kwajalein Atoll, 

all evacuees were decontaminated by showering and bathing, often repeatedly, and residual 

levels of contamination were monitored with hand-held survey meters, which measured external 

exposure rates near the body surface. 

Only the monitoring data for 15 Marshallese who were evacuated by plane and showered 

several times at Kwajalein Atoll can be used to estimate fractions of the activity of fallout 

contamination on skin that was removed by successive showers. There were no measurements 

before the fourth shower for one individual who was evacuated by plane, and the remaining 66 

individuals who were evacuated by ship showered or were hosed down with salt water several 

times before they were first monitored. Survey meter readings (mR h–1) on March 3 for the 15 

Marshallese reported by Sharp and Chapman (1957) are given in Table D-3, and the 

corresponding estimates of the parameter γj used in our models are given in Table D-4. 

Data in Table D-3 were obtained under realistic conditions of contamination by 

descending fallout and repeated showers soon after deposition on skin. However, measured 

exposure rates after each shower probably included significant contributions from internally 

deposited radionuclides. To the extent that those contributions were significant, observed 

reductions in exposure rates after successive showers should underestimate fractions of the 

contamination on skin that was removed during each shower. In addition, native Marshallese 

were clothed while showering (Sharp and Chapman 1957), which could have affected removal of 

186 
contamination and measured exposure rates. It is likely that showering while clothed also 

resulted in underestimates of removal of contamination on skin. 

Twenty-eight military personnel who were exposed to fallout from Shot BRAVO also 

were evacuated to Kwajalein, decontaminated by showering after arrival, and monitored. 

Monitoring data for those personnel are given in Table D-5. Those data probably are of limited 

use in estimating removal of contamination from skin. Exposure rates for many individuals, 

including some who did not report that they showered before evacuation, were not reduced 

substantially by showering at Kwajalein on March 2. For the eight individuals with exposure 

rates prior to the first shower on March 2 that ranged from 90 to 250 mR h–1, including four 

individuals who reported that they showered before evacuation, the exposure rate after the first 

shower ranged from 4 to 15% of the exposure rate beforehand, indicating that a single shower 

removed between 85 and 96% of the contamination, but the exposure rate for those eight 

individuals was not reduced after the second and successive showers. Given the likelihood of 

significant internal contamination of those eight individuals, the high fractional removals after 

the first shower indicated by these data probably are underestimates. 

Another potentially important consideration in interpreting monitoring data for native 

Marshallese and military personnel after Shot BRAVO is that decontamination by showering or 

washing probably involved more vigorous scrubbing than normal, in an effort to remove known 

high levels of contamination. Sharp and Chapman (1957) noted that special efforts were needed 

to adequately decontaminate the hair and head of Marshallese, that scrubbing of Marshallese 

sometimes caused tenderness and soreness on other parts of the body, and that military personnel 

were subjected to a thorough decontamination regime. Such deliberate actions probably 

removed higher fractions of contamination on skin than occurred in routine showering when high 

levels of contamination were not suspected. Higher removals of contamination than normal 

could have compensated somewhat for the likelihood that measured external exposure rates 

underestimated the extent of removal from skin, as noted above. 

D.2.2.5 Data from Study by Friedman

Friedman (1958) studied the efficiency of removal of dry soil from skin of 45 volunteers 

by various aqueous and waterless methods. Soil was labeled with 140La and was intended to 

187 
simulate radioactive fallout. The size of soil particles ranged from 1.5 m to < 47 m. Soil was 

applied on the hairless side of forearms as dust, under dry conditions, and was worked into skin 

with a rounded glass rod using moderate pressure. Only the aqueous methods are of interest in 

estimating the efficiency of showering in removing contamination. These methods included: 

(1) running tap water, with scrub; (2) soap (stearate salt) and water, scrub and flush; (3) soap, 

abrasive, water, scrub, and flush; (4) commercial powdered detergent (10% solution), tap water, 

scrub and flush; (5) complexing agent (1% citric acid), scrub and flush; and (6) chelating agent 

(1% versene), scrub and flush. 

Removal efficiencies of the aqueous methods, expressed as average cumulative fractions 

of the initially deposited soil that was removed after three successive washings reported by 

Friedman (1958) are given in Table D-6, and the corresponding estimates of the parameter γj

used in our models are given in Table D-7. All methods removed most of the contamination in 

the first washing; running tap water with scrub removed the least amount, and removal by the 

other five aqueous methods was similar. Variability in the measurements was substantially 

greater in the second and third washings than in the first. This result may indicate that removal 

by mechanical scrubbing was the most important in the first washing, and that chemical 

interactions involving the different cleansers became important in subsequent washings, when 

residual contamination was increasingly difficult to remove. 

There may be limitations in applying results of the study by Friedman (1958) to other 

exposure situations. Possible limitations include that: (1) removal efficiencies could be different 

if soil or skin was moist at the time of contamination, rather than dry; (2) study subjects 

presumably kept their forearms mostly still between the time of deposition and times of washing, 

which probably minimized the extent of inadvertent shake-off of larger soil particles, especially 

before the first washing, that might be expected during normal daily activities; and (3) deliberate 

efforts to remove contamination might have resulted in higher removal efficiencies than would 

normally occur while showering, especially in areas of the body that are difficult to reach. The 

last concern also is an issue with other studies discussed above. Given these limitations, removal 

efficiencies in most situations, especially situations where significant contamination of skin is 

not expected, could be lower than estimates reported by Friedman (1958). 

188 
D.2.2.6 Data from Study by Fogh et al.

Fogh et al. (1999) reported results of a study to estimate the efficiency of removal of 

contaminants from skin by hand washing. Study subjects were exposed to specially prepared 

airborne particles of diameter 0.5, 2.5, or 10 μm in two indoor office environments, where 

contamination of skin occurred by dry deposition. Removal efficiencies by a single hand 

washing were 0.06 and 0.19 for 0.5-μm particles and ranged from 0.29 to 0.48 for the larger 

particles, with estimates for 2.5-μm particles tending to be the highest. Since particle sizes in 

this study were substantially smaller than particle sizes in most fallout to which military 

participants were exposed, including exposures in resuspension scenarios, estimated removal 

efficiencies probably have limited relevance to estimation of the parameter γ in the first shower 

after contamination. However, if most larger fallout particles would be removed in the first 

shower, results of this study may be representative of removal efficiencies in a second shower. 

Fogh et al. (1999) also studied the efficiency of various methods of sampling 

contaminants from skin. These studies used rat skin that was exposed in a small test chamber to 

airborne particles of diameter 2.5, 4.5, or 8 μm. Results of those studies do not appear to be 

useful in estimating removal efficiencies. Methods of sampling did not resemble normal 

washing or showering, and results were not presented in a form that would allow estimation of 

the parameter γ. 

189 
Table D-1. Mean fractions of PbO initially deposited on palms of hands that 

was removed in successive 30-s wipes (Boeniger 2006) 

Fraction of initial contamination removed 

Type of wipea Contamination 

levelb 

Wipe 1 Wipe 2 Wipe 3 Wipe 4 

PW Low 0.56 0.13 0.070 0.037 

PW High 0.58 0.10 0.041 0.024 

WD Low 0.63 0.078 0.032 0.019 

WD High 0.60 0.087 0.035 0.017 

GW Low 0.57 0.085 0.035 0.027 

GW High 0.52 0.11 0.047 0.032 

a

 PW = Palintest wipes (Palintest USA, Erlanger, KY); WD = Wash’n Dry wipes (Colgate-Palmolive, 

New York); GW = Ghost Wipes (Environmental Express, Mount Pleasant, SC). 

b

 Low = Loading of PbO about 200 μg; High = Loading of PbO about 3,000 μg. Contaminated area of 

palms was about 1,060 cm2

. 

190 
Table D-2. Mean fractions of PbO deposited on palms of hands at time of each wiping that 

was removed in successive wipes (γ) estimated from data in Table D-1a

 

Fraction of contamination at time of each wiping removed (γ) Type of wipeb Contamination 

levelc

Wipe 1 Wipe 2 Wipe 3 Wipe 4 

PW Low 0.56 0.30 0.23 0.16 

PW High 0.58 0.24 0.13 0.087 

WD Low 0.63 0.21 0.11 0.072 

WD High 0.60 0.22 0.11 0.061 

GW Low 0.57 0.20 0.10 0.088 

GW High 0.52 0.24 0.13 0.10 

Average 0.58 0.23 0.13 0.094 

Minimum 0.52 0.20 0.10 0.061 

Maximum 0.63 0.30 0.23 0.16 

a

 Parameter γ is used in models developed in Section 3.5 and is calculated as described in 

Appendix D.2.2.1. 

b

 PW = Palintest wipes (Palintest USA, Erlanger, KY); WD = Wash’n Dry wipes (Colgate-Palmolive, 

New York); GW = Ghost Wipes (Environmental Express, Mount Pleasant, SC). 

c

 Low = Loading of PbO about 200 μg; High = Loading of PbO about 3,000 μg. Contaminated area of 

palms was about 1,060 cm2

. 

191 
Table D-3. Measurements of radioactive contamination of 15 native Marshallese affected by 

fallout from Operation CASTLE, Shot BRAVO in March 1954a

 

External exposure rate (mR h–1) at body surfaceb

 Individual 

identifier Before first 

shower Second reading Third reading Fourth reading 

11 200 30 12 10 

12 200 25 20 10 

13 80 70 45 40 

15 80 30 20 10 

18 200 80 40 30 

27 240 30 15 

30 200 60 35 20 

38 100 30 10 

46 200 30 25 15 

52 80 70 70 40 

56 80 50 20 15 

57 200 100 50 30 

60 200 100 30 30 

74 200 100 60 35 

77 400 20 15 7 

a

 Data obtained from Part 1, Table 5.1 of Sharp and Chapman (1957). Second, third and fourth readings 

were made after successive showers. 

b

 Measurements were made on March 3, two days after detonation of Shot BRAVO on March 1. 

192 
Table D-4. Fractional reductions in measured exposure rates at time of each shower after three 

successive showers (γ) estimated from data in Table D-3a

 

Fractional reduction of exposure rate at time of each shower (γ) Individual identifier 

First shower Second shower Third shower 

11 0.85 0.60 0.17 

12 0.88 0.20 0.50 

13 0.13 0.36 0.11 

15 0.63 0.33 0.50 

18 0.60 0.50 0.25 

27 0.88 0.50 

30 0.70 0.42 0.43 

38 0.70 0.67 

46 0.85 0.17 0.40 

52 0.13 0.00 0.43 

56 0.38 0.60 0.25 

57 0.50 0.50 0.40 

60 0.50 0.70 0.00 

74 0.50 0.40 0.42 

77 0.95 0.25 0.53 

a

 Parameter γ is used in models developed in Section 3.5 and is calculated as described in 

Appendix D.2.2.1. 

193 
Table D-5. Measurements of radioactive contamination of 28 military personnel affected by 

fallout from Operation CASTLE, Shot BRAVO in March 1954a

 

Exposure rate (mR h–1) at body surfaceb

 Individual 

identifier 

Number of 

showers or 

washings 

Before first 

shower 

After first 

shower 

Third 

reading 

Fourth 

reading 

After last 

shower 

401 11 90 5 5 5 5 

402 10 6 6 5 5 5 

403 8 5 5 5 5 

404 10 250 10 10 10 10 

405 7 5 5 5 5 4 

406c 7 5 5 5 

407c 7 5 5 5 3.5 

408 7 5 5 5 5 4 

409c 5 150 10 10 10 10 

410 5 20 10 10 10 10 

411c 5 25 10 10 10 10 

412c 5 25 15 15 15 15 

413c 5 45 15 15 15 15 

414c 5 100 15 15 15 15 

415c 5 15 10 10 10 10 

416 5 5 5 5 5 5 

417 5 25 15 15 15 15 

418c 5 100 10 10 10 8 

419 5 30 15 15 10 10 

420c 5 15 10 8 8 8 

421 5 10 5 5 5 5 

422c 5 15 5 4.5 4 4 

423 5 40 15 10 10 10 

424c 5 15 5 5 5 5 

425c 5 150 15 15 15 15 

426 5 20 5 4.5 4.5 4.5 

427 5 200 25 25 25 25 

428 5 100 10 10 10 10 

a

 Data obtained from Part 2, Table 5.1 of Sharp and Chapman (1957). 

b

 Measurements were made on March 2, one day after detonation of Shot BRAVO on March 1. c

 Individual reported showering at least once before evacuation to Kwajalein Atoll. 

194 
Table D-6. Mean cumulative fractions of initially deposited labeled soil on forearms of 

volunteers that was removed in successive washingsa

 

Method of aqueous Cumulative fraction of initial contamination removed 

decontamination First washing Second washing Third washing 

Running tap water, with scrub 0.825 0.910 0.938 

Soap (stearate salt) and water, scrub 

and flush 

0.958 0.986 0.993 

Soap, abrasive, tap water, scrub and 

flush 

0.989 0.999 

Commercial powdered detergent 

(10% solution), tap water, scrub and 

flush 

0.993 100.0 

Complexing agent (1% citric acid 

solution), scrub and flush 

0.972 0.985 0.989 

Chelating agent (1% versene 

solution), scrub and flush 

0.990 0.999 

a

 Data obtained from Fig. No. 9 of Friedman (1958) apply when no barrier crèam was used. 

195 
Table D-7. Mean fractions of labeled soil deposited on forearms at time of each washing that 

was removed in successive washings (γ) estimated from data in Table D-6a

Fraction of contamination at time of each washing Method of aqueous removed (γ) Decontamination 

First washing Second washing Third washing 

Running tap water, with scrub 0.825 0.49 0.31 

Soap (stearate salt) and water, scrub 

and flush 

0.958 0.67 0.50 

Soap, abrasive, tap water, scrub and 

flush 

0.989 0.91 

Commercial powdered detergent 

(10% solution), tap water, scrub and 

flush 

0.993 1.0 

Complexing agent (1% citric acid 

solution), scrub and flush 

0.972 0.46 0.27 

Chelating agent (1% versene 

solution), scrub and flush 

0.990 0.90 

Average 0.95 0.74 0.36 

Minimum 0.83 0.46 0.27 

Maximum 0.99 1.0 0.50 

a

 Parameter γ is used in models developed in Section 3.5 and is calculated as described in 

Appendix D.2.2.1. 

196 
D.3 References

Boeniger M. A comparison of surface wipe media for sampling lead on hands. J. Occ. Environ. 

Hyg. 3:428–434; 2006. 

Boeniger M., Esswein E., and Ashley K. Development and evaluation of a new identification 

and decontamination system for removing toxic elements, especially lead. Abstract for 

Poster 63 at International Conference on Occupational Exposures of Skin to Chemicals – 

2005. National Institute for Occupational Safety and Health, Cincinnati, OH; 2005. 

Cormack D.H. Essential Histology. J.B. Lippincott Co., Philadelphia, PA; 1993. 

Fogh C.L., Byrne M.A., Andersson K.G., Bell K.F., Roed J., Goddard A.-J.H., Vollmair D.V., 

and Hotchkiss S.A.M. Quantitative Measurement of Aerosol Deposition on Skin, Hair and 

Clothing for Dosimetric Assessment – Final report, Risø-r-1075 (en). Risø National 

Laboratory, Roskilde, Denmark; 1999 (June). 

Friedman W.J. Decontamination of synthetic radioactive fallout from the intact human skin. 

Industr. Hyg. J. 19(1):15–19; 1958. 

International Commission on Radiological Protection (ICRP). Report of the Task Group on 

Reference Man, ICRP Publication 23. Pergamon Press, Oxford, UK; 1975. 

Sharp R. and Chapman W.H. OPERATION CASTLE – Project 4.1 Addendum, WT-938. Naval 

Medical Research Institute, Bethesda, Maryland; 1957. 

197 
APPENDIX E 

EXAMPLE CALCULATIONS OF DOSES TO SKIN 

FROM DERMAL CONTAMINATION 

198 
E.1. Dermal Contamination by Descending Fallout at NTS 

This section presents example calculations of dose for a hypothetical situation involving 

deposition of radioactive material onto skin due to exposure to descending fallout at NTS. We 

assume that a calculation of dose to skin of the forearms and back of the hands is desired. This 

example is intentionally simplified by assuming exposure to 90Sr only. 

For these calculations, we assume that an individual was exposed to descending fallout 

that resulted in an activity concentration of 90Sr on the ground surface of 1 μCi m–2. The 

assumed activity concentration is typical of concentrations in areas near ground zeros of nuclear 

tests at NTS in 1990 (McArthur 1991). We assume that the uncertainty in this activity 

concentration can be represented by a lognormal probability distribution with a geometric mean 

(GM) of 1 μCi m–2 and geometric standard deviation (GSD) of 2.0; this probability distribution 

has a 90% credibility interval (CI) that ranges from about 0.5 to about 2 μCi m–2. 

The skin contamination factor, ah, for forearms and hands estimated from the volcanic 

ash studies in Costa Rica is about 115 cm2

 (Section 4.1.2), and the average surface area (s) of 

forearms and hands in adults is 1963 cm2

. These estimates give an average interception and 

retention fraction r = (ah/s) for forearms and hands of about 0.06. When uncertainties in the skin 

contamination factor and surface area of forearms and hands are taken into account, the resulting 

interception and retention fraction can be represented by a lognormal probability distribution 

with a GM of 0.06 and GSD of 3.0 (Table 4-1). 

We assume that descending fallout contained an unknown distribution of particle sizes; 

this assumption results in the highest uncertainties in parameters used to adjust the interception 

and retention fraction (r) obtained from the volcanic ash studies. On the basis of this 

assumption, the particle-size adjustment factor, PSa, is represented by a uniform probability 

distribution from 0.4 to 1.6 (mean of 1.0), the enrichment of specific activity, EF, is represented 

by a log-uniform probability distribution from 1.0 to 4.0, and the activity-weight adjustment 

factor, AW, is represented by a log-triangular probability distribution with a minimum at 0.01, 

mode at 0.1, and maximum at 1.0 (Table 4-2). 

The remaining adjustment to the interception and retention fraction (r) is the 

enhancement due to moisture, EM. By assuming that the amount of moisture on skin of an 

199 
exposed individual at NTS was less than the amount of moisture on skin of human subjects in the 

volcanic ash studies in Costa Rica, the parameter EM is represented by a uniform probability 

distribution between 0.5 and 1.0, which has a mean of 0.75 (Table 4-2). 

The dose-rate factor (DRF) for 90Sr that applies to skin on the forearms and back of the 

hands is calculated using eq. (4-4) (Section 4.6.1) and an assumption that the nominal depth of 

radiosensitive tissues in those regions is 8 mg cm–2. The calculated dose-rate factor for 90Sr at a 

depth of 7 mg cm–2 is 6.8 rem h–1 per μCi cm–2 (Kocher and Eckerman 1987). Uncertainties in 

the dose-rate factor at a depth of 7 mg cm–2 are described in Section 4.6.1.1. A small uncertainty 

of about 10% in the dose-rate factor calculated by Kocher and Eckerman (1987) is represented 

by a normal probability distribution with a 90% CI of (6.1, 7.5) rem h–1 per μCi cm–2. A 

backscatter correction for 90Sr, which accounts for the neglect of backscattering of emitted 

electrons in air in calculations by Kocher and Eckerman (1987), is represented by a triangular 

probability distribution with a minimum at 0.7, mode at 0.8, and 0.9. The assumed uncertainty in 

the backscatter correction for 90Sr is less than the uncertainty represented by the probability 

distribution developed in Section 4.6.1.1, which applies to mixtures of radionuclides in fallout 

with different maximum energies of emitted electrons. Finally, shielding of emitted electrons by 

particles deposited on skin is assumed to result in a reduction in the dose-rate factor for 90Sr 

represented by a triangular probability distribution with a minimum at 0.6, mode at 0.8, and 

maximum at 1.0. The assumed uncertainty in the shielding correction for 90Sr also is somewhat 

less than the uncertainty represented by the probability distribution for a mixture of radionuclides 

in fallout developed in Section 4.6.1.1. 

As indicated in eq. (4-4), the dose-rate factor for 90Sr at a depth of 7 mg cm–2 and its 

uncertainty that account for backscattering in air and shielding by particles is adjusted using a 

skin-depth modification factor, SDMF, to give a dose-rate factor that applies at the nominal 

depth of radiosensitive tissues of skin on the forearms and back of the hands of 8 mg cm–2. As 

described in Section 4.6.1.2.2, the uncertainty in SDMF due to the variability in the depth of 

radiosensitive tissues in regions of the body where the nominal depth is 8 mg cm–2 is represented 

by a triangular probability distribution with a minimum at 0.7, mode at 0.95, and maximum at 

1.3. The other source of uncertainty in SDMF discussed in Section 4.6.1.2.2 applies only in 

estimating a dose-rate factor for mixtures of radionuclides in fallout and is not included. 

200 
The effect of inefficient showering on the dose to skin is included in all calculations. The 

fraction of the contamination that is removed in each shower by exfoliation of skin cells (β) on 

the forearms and back of the hands is assumed to be represented by the probability distribution 

for the upper limbs given in Table 4-5. Probability distributions of removal fractions by 

showering (γj) for normal and highly efficient showering in Table 4-5 were assumed in separate 

calculations, to illustrate the effect of different assumptions about the efficiency of showering in 

removing contamination. The time between a detonation and deposition of 90Sr on skin (T0) is 

assumed to be 2 hours, the time between deposition and the first shower (ΔTpost) is assumed to be 

12 hours, and the time between successive showers after the first is assumed to be 24 hours. 

However, the dose to skin in these calculations does not depend on T0, because only a single 

radionuclide is assumed to be present and the rate of decrease of its activity is constant in time. 

Using eqs. (3-2) to (3-5) in Section 3.2 and eq. (3-32) in Section 3.5.2 with the 

probability distributions of parameter values described above, we obtained probability 

distributions of doses to skin of the forearms and back of the hands from exposure to 90Sr in 

descending fallout at NTS given in Table E-1. These results include the dose before the time of 

the first shower at 12 hours after deposition, D1, the dose after the first shower, Dsh, and the total 

dose, DN = D1 + Dsh, after 120 daily showers (N = 120). The mean dose after the first shower in 

these calculations exceeds the mean dose before the first shower by a factor of about six when 

normal efficiency of showering is assumed but by less than 20% when showering is assumed to 

be highly efficient. An assumption of highly efficient showering decreases the mean total dose 

by a factor of three compared with the mean total dose assuming normal showering.

Table E-1 also gives the probability distribution of the dose to skin from exposure to the 

assumed concentration of 90Sr in fallout deposited on the ground surface. The dose-rate factor 

for ground-surface exposure (1.86 × 10–2 rem h–1 per μCi cm–2) is obtained from Table III.3 of 

Eckerman and Ryman (1993), and the exposure time is assumed to be 12 hours. The dose from 

dermal contamination exceeds the dose from ground-surface exposure even if the first shower is 

assumed to remove all contamination. When mean doses are compared, the total dose from 

dermal contamination is higher than the total dose from ground-surface exposure by a factor of 

more than 40 when normal showering is assumed and about 13 when showering is assumed to be 

highly efficient. 

201 
Table E-1. Probabilistic estimates of electron doses to skin from dermal 

contamination by 90Sr in descending fallout at NTS and comparison 

with dose from exposure to 90Sr on ground surfacea 

Uncertainty distribution of electron dose (mrem) 

5th percentile 50th percentile Mean 95th percentile 

Normal showering 

Dose before first 

shower (D1) 

2.6 × 10–3 4.2 × 10–2 1.8 × 10–1 7.2 × 10–1

Dose after first 

shower (Dsh) 

7.0 × 10–3 1.6 × 10–1 1.0 3.5 

Total dose 

(DN = D1 + Dsh) 

1.1 × 10–2 2.1 × 10–1 1.2 4.3 

Highly efficient showering 

Dose before first 

shower (D1) 

2.6 × 10–3 4.2 × 10–2 1.8 × 10–1 7.2 × 10–1

Dose after first 

shower (Dsh) 

0.0 3.3 × 10–2 2.1 × 10–1 7.4 × 10–1

Total dose 

(DN = D1 + Dsh) 

4.9 × 10–3 8.5 × 10–2 3.9 × 10–1 1.4 

Dose from ground-surface exposure 

6.9 × 10–3 2.2 × 10–2 2.9 × 10–2 7.2 × 10–2

a

 Calculations are described in Appendix E.1.

202 
E.2. Dermal Contamination by Descending Fallout in the Pacific 

E.2.1 Introduction

This section presents an example dose reconstruction for a participant in Operation 

SANDSTONE in the Pacific who was exposed during Shots XRAY, YOKE, and ZEBRA while 

stationed at Kwajalein Atoll. The participant later developed skin cancer on his face and, thus, 

estimates of dose to skin of the face are of interest. 

This exercise provides estimates of electron dose to skin of the face due to deposition of 

descending fallout on that part of the body. Doses to skin from exposure to photons and alpha 

particles emitted by radionuclides deposited on skin and exposure to photons and electrons 

emitted by radionuclides in fallout deposited on the ground surface are not estimated. 

Probabilistic estimates of doses to skin are obtained using Monte Carlo methods of 

propagating uncertainties in the various parameters used in the calculations. Point estimates of 

doses also are obtained using deterministic (point) estimates of parameter values. Monte Carlo 

methods allow estimation of the entire range of possible doses, including the upper 95% 

credibility limit used in adjudicating claims for compensation for radiogenic diseases by military 

participants at atmospheric weapons tests. A sensitivity analysis is performed to identify 

parameter uncertainties that contribute the most to the uncertainty in estimated doses. 

E.2.2 Methods

Fallout from the three shots at Operation SANDSTONE reached Kwajalein Atoll within a 

few days after each detonation. The highest measured exposure rates (I) from fallout deposited 

on ships were 7 × 10–5 R h–1 at 150 hours after Shot XRAY, 5 × 10–4 R h–1 at 42 hours after Shot 

YOKE, and 4 × 10–5 R h–1) at 144 hours after Shot ZEBRA.32

It is assumed that the participant was outside on the main deck of a ship at Kwajalein 

Atoll for the entire period of deposition of fallout. The activity concentration of radionuclides 

that were deposited and retained on skin (Ci cm–2

skin) is estimated as a fraction of the activity 

 

32 Personal communication from N. Barss, SAIC, July 2004. 

203 
concentration that was deposited on the ship deck (Ci cm–2

ship); the latter concentration is 

derived from the measured exposure rates. Fallout is assumed to have occurred around the time 

the maximum exposure rate was measured. Doses to skin from dermal contamination by 

descending fallout are estimated for each shot and as a total dose from all three shots. All 

calculations included assumptions about the efficiency of showering. 

For comparison purposes, a second scenario is included in which it is assumed that the 

participant was outdoors, on land, at Kwajalein Atoll. The difference between the two scenarios 

is that the area of surface contamination on a ship is finite, whereas the atoll is sufficiently large 

that it essentially represents an infinite contaminated area. This difference affects the calculated 

activity concentration of radionuclides in deposited fallout corresponding to a known exposure 

rate and the uncertainty in the calculated concentration. 

The electron dose to skin of the face (rem) from dermal contamination by descending 

fallout has two components: (1) the dose from the time of deposition of radionuclides on skin 

until the time of the first shower, denoted by D1, and (2) the dose after the first shower that 

results from incomplete removal of contamination by showering, denoted by Dsh. In accordance 

with eq. (3-6) in Section 3.2.2 and eq. (3-35) in Section 3.5.2, the two components of the total 

dose are calculated as: 

   2

2

max

max

4

1

max

1

max

0

01 4

)1(

d

























 

 

  

 

 



f cmmg

x

post

x

f cmmg

Tt

t

x

DRFAR

x

Ttt

A

AD DRFARtt post

 (E-1) 

  









































 

   

N

j

j

k

k

x

j

x

j

sh f cmmg x

TT

DRFARAD

2

1

1

)1()1(

1

0 4 α

1 2 (E-2) 

where 

A0 = reference activity concentration of radionuclides on ship or ground 

surface at 1 hour after detonation (Ci cm–2

ground) – see eq. (E-3); 

tmax = time after detonation when maximum exposure rate due to fallout on 

ship was measured and deposition on skin occurred (h); 

204 
Tpost = period between acute fallout event and time of first shower (h); 

x = shot-specific exponent that accounts for effect of radioactive decay on 

time-dependence of external exposure rate (unitless); 

ARf = fraction of activity concentration of radionuclides deposited on ship or 

ground surface that is intercepted and retained on skin (unitless) –see 

eq. (E-4); 

DRF4 mg cm–2 = electron dose rate per unit activity concentration of radionuclides 

deposited on skin (rem h–1 per Ci cm–2) at nominal depth below body 

surface of 4 mg cm–2; 

Tj = time after detonation of j

th shower (h), where T1 = tmax + ΔTpost; and 

αj = 1 – (γj + β) (unitless), where γj is fraction of activity of radionuclides on 

skin that is removed by washing during the j

th shower and β is fraction of 

activity that is removed by exfoliation of skin cells during each shower 

and between successive showers. 

The total dose to skin after N showers is DN = D1 + Dsh. In this exercise, N is assumed to be 

120 days, meaning that the additional dose after 120 daily showers, which occur at a regular 

interval of 24 hours, is assumed to be negligible. 

The reference activity concentration, A0, is estimated by applying a decay correction to 

the activity concentration on a ship or ground surface at the time the highest exposure rate was 

measured: 

  x tAA



0  maxmax (E-3) 

where 

Amax = activity concentration of radionuclides on ship or ground surface at time tmax

(Ci cm–2

ground) – see eq. (E-4). 

The maximum activity concentration (Amax) on a ship or the ground surface is estimated 

using the highest measured exposure rate (I) at time tmax after a detonation and a pre-calculated 

gamma constant (), which is obtained as described by Egbert et al. (1985): 

205 
 

rf

m

kk

kI A

  / max (E-4) 

where 

I = maximum exposure rate (R h–1) at time tmax after detonation; 

km = bias correction factor (unitless) to account for tendency of instrument readings to 

overestimate actual exposure rate; 

 = calculated exposure rate at height of 1 m per unit activity concentration of 

radionuclides in fallout distributed uniformly on infinite plane surface at time tmax

after detonation (R h–1 per Ci cm–2); 

kf = bias correction factor (unitless) that applies when contaminated surface of ship or 

ground is finite; and 

kr = bias correction factor (unitless) to account for shielding provided by roughness of 

ship or ground surfaces. 

A fraction ARf of the activity of descending fallout is intercepted and retained on skin of 

the face of the exposed individual. As described in Section 3.2, this fraction is estimated as: 

f   a    AWEFEMPSrAR (E-5) 

where 

r = interception and retention fraction for skin of face (unitless) estimated from 

studies of deposition and retention of volcanic ash particles; 

PSa = adjustment factor (unitless) that represents how retention on skin depends on 

particle size of material incident on body surface and accounts for difference 

between weight particle-size distribution of fallout at location of interest and 

particle-size distribution for which interception and retention fraction (r) was 

estimated using data from volcanic ash studies; 

EM = adjustment factor (unitless) that accounts for dependence of efficiency of 

retention of deposited particles on amount of moisture on skin; 

206 
EF = specific-activity enrichment factor (μCi g–1

skin per μCi g–1surface) that accounts 

for experimental evidence indicating that specific activity of soil retained on 

skin is higher than specific activity of soil on ground when radionuclides are 

preferentially distributed on particle surfaces; 

AW = activity-weight adjustment factor (unitless) that accounts for difference between 

activity and weight particle-size distributions in fallout at location of interest. 

The dose to radiosensitive tissues of skin on the face is estimated using a dose-rate factor (DRF) 

that applies at the nominal depth of radiosensitive tissues in that region of the body surface: 

DRF DRF SDMF

cmmg cmmg 2  2  4 7 (E-6) 

where 

2 7  cmmg

DRF = dose rate per unit activity concentration of all radionuclides combined 

on skin (rem h–1 per Ci cm–2) at depth of 7 mg cm–2, which is a 

standard depth used in estimating electron doses to skin; and 

 SDMF = skin-depth modification factor (unitless) that accounts for assumption 

that radiosensitive tissues of skin on face are located at average depth of 

4 mg cm–2. 

E.2.3 Description of Parameters and Assumed Probability Distributions

The following sections describe the various parameters in the model equations and 

assumptions about probability distributions to represent their uncertainty. 

E.2.3.1 Measured Exposure Rate (I) 

The contaminated plume from each of the nuclear detonations of concern arrived at 

Kwajalein Atoll within a few days after the tests. The exposure rate from radioactive material 

that accumulated on a ship or on the ground surface increased and reached a maximum as the 

plume passed by the atoll. The maximum exposure rate is used in this exercise to estimate the 

activity concentration of radionuclides on a ship or ground surface. The highest measured 

207 
exposure rates (I) and times when those readings were taken (tmax) noted in Appendix E.2.2 are 

given in Table E-2. It is assumed that the measurements were taken in the same place where the 

exposed individual was located. 

An uncertainty of a factor of two is assigned to the maximum exposure rate (I) to account 

for the variability in instrument readings of about  30% (NRC 1985; Table C-6) and possible 

errors in reading an instrument (e.g., calibration errors, inappropriate height above ground, 

misreading of instrument). This uncertainty is represented by a log-uniform probability 

distribution with a minimum at I/2 and maximum at I×2. 

E.2.3.2 Bias in Instrument Reading (km) 

Documentation of survey instruments used during the weapons testing program indicates 

that they could have overestimated the true exposure rate by about 40% (NRC 1985). Thus, on 

average, the bias correction factor (km) is assumed to be 1.4. A small uncertainty represented by 

a triangular probability distribution with a minimum at 1.3, mode at 1.4, and maximum at 1.5 is 

assigned to this factor. 

E.2.3.3 Gamma Constant (

The gamma constant (Γ) gives the exposure rate per unit activity concentration of all 

radionuclides in fallout on the ground surface combined and is calculated by assuming an infinite 

plane source and no fractionation of radionuclides. Deterministic (point) estimates of the gamma 

constant at the time of maximum exposure rate, tmax, at each test were obtained from the FIIDOS 

computer code (Egbert et al. 1985) and are given in Table E-2. 

An uncertainty of a factor of two is assigned to each gamma constant to account for 

uncertainties in the fission mode, the degree of fractionation in fallout, and calculations of 

photon transport in air. This uncertainty is represented by a log-uniform probability distribution 

with a minimum at /2 and maximum at ×2. 

208 
E.2.3.4 Bias to Account for Finite Area of Contaminated Surface (kf) 

The reported gamma constant was calculated by assuming that the source region is an 

infinite plane. For a finite surface, such as the deck of a ship, the gamma constant is lower by a 

factor kf. Equivalently, if the same exposure rate is measured above an infinite and a finite 

surface, the activity concentration of radionuclides on the infinite surface is lower by a factor kf. 

Bias factors to account for finite sources have been estimated for different rectangular 

and circular surfaces (Apostoaei et al. 2000). If we assume that the width of ships can range 

from 10 to 50 m (30 to 160 feet), as indicated by data summarized in Table E-3, kf can vary 

between 0.2 and 0.8. On the basis of this assumption, a uniform probability distribution between 

0.2 and 0.8 is assigned to this parameter. No bias correction to account for finite source regions 

is needed when exposure occurred on land. 

E.2.3.5 Bias to Account for Surface Roughness (kr) 

The gamma constant (Γ) is calculated by assuming that a contaminated surface is a 

perfectly smooth plane. However, real surfaces have many irregularities and inherent roughness. 

The gamma constant for a rough surface is lower by a factor kr when the shielding provided by 

roughness is taken into account. 

Burson and Profio (1977) provide reduction factors (kr) for different surfaces including 

paved areas, lawns, graveled areas, and plowed fields. Surfaces on a ship are relatively smooth, 

probably similar to paved surfaces or even smoother. A reasonable range of values of kr on a 

ship is 0.8 to 1.0. However, land surfaces are more uneven, and kr may vary from 0.5 to 0.9 

(Burson and Profio 1977). Uniform probability distributions between these limits are assigned to 

this parameter in cases of exposure on ship or land. 

209 
E.2.3.6 Radioactive Decay Exponent (x) 

The activity of all radionuclides in fallout combined decreases with time as t

–x

. Estimates 

of the exponent x are 0.545 at Shots XRAY and YOKE and 1.1 at Shot ZEBRA.33 The 

uncertainty in x is assumed to be represented by a normal probability distribution with the mean 

specified above and a standard deviation of 0.1 (NRC 2003; page 151). 

E.2.3.7 Time from Deposition on Skin Until First Shower (ΔTpost); Time Between Showers 

Accumulation of radionuclides on skin during a fallout episode presumably occurred 

continuously during passage of the plume, which normally took a few hours. Consequently, it 

probably is reasonable to assume that contamination was present on skin for at least 6 hours. 

Given the hot climate in the Marshall Islands, participants presumably showered at least once 

each day. Thus, it is reasonable to assume that participants showered within 24 hours after 

passage of the plume. Since the time from deposition on skin until the first shower is unknown, 

a uniform probability distribution between 6 and 24 hours is assumed for this parameter. 

As noted previously, the time between successive showers after the first (Tj – Tj–1, j ≥ 2) 

is assumed to be 24 hours, with no uncertainty. 

E.2.3.8 Interception and Retention Fraction (r) 

The interception and retention fraction (r) discussed in Section 4.1 is estimated on the 

basis of data on deposition and retention of volcanic ash on human subjects in Costa Rica (Miller 

1966a,b). The uncertain interception and retention fraction, r, for skin of the face is represented 

by a lognormal probability distribution with a GM of 0.015 and GSD of 3.6 [90% CI of (0.002, 

0.12); Table 4-1]. 

The interception and retention fraction, r, is calculated as (ah/sf), where ah (cm2

) is a skin 

contamination factor that is estimated from data obtained in the volcanic ash studies as the 

weight of particles deposited and retained on skin of the face divided by the weight of particles 

 

33 Personal communication from N. Barss, SAIC, July 2004.

210 
deposited per unit area on the ground surface, and sf is the surface area of the face (cm2

). The 

uncertainty in the interception and retention fraction for the face is determined almost entirely by 

the assumed uncertainty in ah (Section 4.1.3). 

E.2.3.9 Particle-Size Adjustment (PSa) 

Particle-size distributions of volcanic ash in the studies of deposition and retention on 

skin in Costa Rica had a median diameter of about 80 m, and some particles were as large as 

300 m (Miller 1966a; page 324). However, given that tests at Operation SANDSTONE took 

place sufficiently far from Kwajalein Atoll that the plumes reached the atoll only after two or 

more days, the particle-size distribution in fallout at Kwajalein can be assumed to have had a 

median diameter of 50 m or less. Since smaller particles are more efficiently retained on skin 

than larger particles, it is expected that retention on skin was enhanced in this case by a factor 

PSa that can be represented by lognormal probability distribution with a GM of 1.3 and GSD of 

1.1 (Section 4.2.1.1, Table 4-2). 

E.2.3.10 Enhancement of Retention Due to Moisture on Skin (EM) 

It is reasonable to assume that participants in the Pacific had considerable amounts of 

moisture on their skin due to the warm and humid conditions. Since the volcanic ash studies in 

Costa Rica took place under similar conditions, we assume that the enhancement of retention on 

skin due to the presence of moisture (EM) on skin in the Pacific is represented by a uniform 

probability distribution between 0.8 and 1.5 (Section 4.2.2, Table 4-2). 

E.2.3.11 Enrichment of Specific Activity (EF) 

Most fallout particles at Kwajalein Atoll from shots at Operation SANDSTONE 

presumably were small (mostly less than 100 m, with median diameters less than 50 m), and 

some radionuclides in fallout (mainly refractory elements) presumably were distributed in the 

volume of fallout particles, rather than on particle surfaces, as a result of fractionation. Thus, at 

Kwajalein Atoll, it is expected that little or no enrichment in specific activity occurred, and 

211 
minimal values of the parameter EF are assumed. The uncertainty in this parameter is 

represented by a triangular probability distribution with a minimum and mode at 1.0 and 

maximum at 2.0 (Section 4.2.3, Table 4-2). 

E.2.3.12 Activity-Weight Adjustment Factor (AW) 

At NTS, the activity particle-size distribution in fallout at locations close to ground zero 

was found to differ from the weight particle-size distribution (e.g., see Figs. 8 to 15 of Miller 

1969). For example, in a sample of fallout from Shot SHASTA, particles of diameter less than 

100 m comprised 24% of the weight, but those particles carried only 0.75% of the activity. 

Since most particles that can stick to skin have diameters less than 100 m, the activity 

concentration of fallout particles retained on skin relative to the activity concentration of fallout 

deposited on the ground surface would be smaller at NTS than indicated by values of the skin 

contamination factor (ah) that were derived from the volcanic ash studies in Costa Rica. 

However, fallout reaching Kwajalein Atoll presumably contained mostly small particles 

(< 100 m, with median particle diameters < 50 m). Thus, in contrast to exposures to fallout at 

NTS, little or no additional adjustment to account for differences between activity and weight 

particle-size distributions is needed in assessing dermal contamination at Kwajalein Atoll. In 

this exercise, the parameter AW is represented by a triangular probability distribution with a 

minimum at 0.7 and a mode and maximum at 1.0 (Section 4.2.4, Table 4-2). 

E.2.3.13 Dose-Rate Factor (DRF) at Depth of 7 mg cm–2 

Dose-rate factors (DRFs), which give dose rates to radiosensitive tissues in the basal 

layer of skin per unit activity concentration of beta-emitting radionuclides on the body surface, 

are discussed in Section 4.6.1. For mixtures of radionuclides in fallout, a nominal dose-rate 

factor that applies at a depth below the body surface of 7 mg cm–2 (70 μm) in units of rem h–1 per 

μCi cm–2

skin can be represented by a triangular probability distribution with a minimum at 1.6, 

mode at 3.7, and maximum at 6.8 (Table 4-2). This probability distribution accounts for 

uncertainties in the nominal dose-rate factor due to uncertainties in calculations of electron 

transport, shielding of electrons by fallout particles, and a backscatter correction. 

212 
E.2.3.14 Skin-Depth Modification Factor (SDMF) 

The skin-depth modification factor (SDMF) takes into account that the dose-rate factor 

(DRF) described in the previous section is estimated at a depth below the body surface of 

7 mg cm–2, whereas radiosensitive tissues in skin of the face are located at an average depth of 

about 4 mg cm–2 (Whitton 1973). The depth of radiosensitive tissues on the face can vary from 

20 to 100 μm (ICRP 1975; Charles 1986). An uncertainty in the skin-depth modification factor 

for the face that takes into account the variability in the depth of radiosensitive tissues and the 

effect of mixtures of radionuclides in fallout is discussed in Section 4.6.1.2.1. The uncertainty in 

this parameter is represented by a triangular probability distribution with a minimum at 0.7, 

mode at 1.3, and maximum at 1.7 (Table 4-2). 

E.2.3.15 Removal Fractions of Contamination from Skin (γj, β) 

In addition to the effect of radioactive decay, the activity concentration of radionuclides 

on skin is assumed to be reduced over time by showering and exfoliation of skin cells. The 

removal fraction by showering (γj) is assumed to be highest in the first shower, to decrease in the 

next three showers, and to remain constant in all showers after the fourth, whereas the removal 

fraction by exfoliation, which also accounts for removal of skin cells between showers, is 

assumed to be the same in all showers (Sections 4.7.1 and 4.7.2, Table 4-5). 

The example calculations in this appendix are concerned with estimating dose to skin of 

the face. Given that most participants shaved, as well as showered, on a daily basis, the removal 

fraction by exfoliation of skin cells (β) should be higher than values that apply in most other 

parts of the body. In this exercise, we assume that the highest value of β in Table 4-5 (the value 

for upper limbs) applies to the face. In addition, by assuming that personnel who were exposed 

to fallout at Operation SANDSTONE were aware of their exposures as they occurred, removal 

fractions by showering (γj) that apply when showering is highly efficient in removing 

contamination are assumed to be appropriate. The selected values of these parameters are given 

in Table E-2. 

213 
E.2.4 Estimated Doses to Skin at Kwajalein Atoll

Doses to skin from dermal contamination by descending fallout at Shots XRAY, YOKE 

and ZEBRA in Operation SANDSTONE were estimated for a participant on a ship stationed at 

Kwajalein Atoll. As an alternative scenario, doses to skin also were estimated for a participant 

on land at Kwajalein Atoll. 

A summary of parameter values used in this exercise is given in Table E-2. For each 

parameter, a probability distribution that is assumed to represent its uncertainty is given. This 

table also provides a deterministic (point) estimate of each parameter, which was chosen to be 

the mean of a normal or uniform distribution, the geometric mean of a lognormal or log-uniform 

distribution, or the mode of a triangular distribution. 

Probability distributions of doses to skin from dermal contamination were estimated 

using Monte Carlo methods of uncertainty propagation. Point estimates of doses also were 

obtained using deterministic parameter values. As indicated in results described below, a 

deterministic estimate of dose is substantially less than the corresponding mean of a probability 

distribution when the uncertainty in an estimated dose is large. 

Deterministic and probabilistic estimates of electron doses to skin obtained by assuming 

that a participant was stationed on a ship near Kwajalein Atoll are presented in Table E-4. The 

probability distribution of the dose to the time of the first shower from all three shots combined 

has a 50th percentile at 0.039 rem, mean at 0.10 rem, and 95th percentile at 0.41 rem; an 

uncertainty factor, defined as the ratio of the 95th and 50th percentiles, is 11, and the ratio of the 

95th and 5th percentiles is 85. The dose after the first shower has a 50th percentile at 0.015 rem, 

mean at 0.050 rem, and 95th percentile at 0.2 rem (uncertainty factor of 13). The total dose has a 

50th percentile at 0.058 rem, mean at 0.15 rem, and 95th percentile at 0.59 rem (uncertainty factor 

of 10). About two-thirds of the total dose is received before the first shower. 

The most important contributors to the uncertainty in estimated doses to skin for a 

participant on a ship were identified by performing a sensitivity analysis, which provides percent 

contributions of the variance of each parameter to the variance in the total dose. Results of a 

sensitivity analysis for exposure to fallout at Shot YOKE, which delivered the largest dose, are 

given in Table E-5. The largest contributor to the uncertainty in all three doses is the uncertainty 

214 
in the interception and retention fraction (r). As noted previously, the uncertainty in r is due 

almost entirely to the uncertainty in the skin contamination factor (ah). The second largest 

contributor to the uncertainty in the dose after the first shower is the uncertainty in the removal 

fractions by showering (γj).34 However, the uncertainty in the efficiency of showering is not an 

important contributor to the uncertainty in the total dose. 

The uncertainty in the dose to skin for a participant stationed on a ship could be reduced 

if the type of ship is specified. In such cases, a narrower probability distribution of the bias 

factor to account for the finite size of a ship (kf) could be used. However, since this parameter is 

not an important source of uncertainty in estimated doses to skin, any adjustments of the 

probability distribution for kf would have little impact on uncertainties in estimated doses. 

Doses to skin for a participant exposed on land at Kwajalein Atoll given in Table E-6 are 

about 60% of the doses on a ship given in Table E-4. This reduction is mostly a consequence of 

the effect of the finite surface area of the ship (i.e., increase in the concentration of radionuclides 

in deposited fallout corresponding to a given exposure rate). Although the effect of the finite 

area of a ship is a reduction in dose by a factor of two, on average, this effect is partly offset by 

the greater shielding on land due to ground roughness. 

In the analysis of doses due to exposure on land, the sensitivity analysis for exposures at 

Shot YOKE summarized in Table E-7 indicates that the main sources of uncertainty are similar 

to those for exposure on a ship, with one exception. As indicated in Table E-5, the uncertainty in 

the finite surface area bias (kf) has some importance in cases of exposure on a ship, but this 

parameter is not used in estimating dose on land. 

 

34 Only the removal fraction in the first shower, γ1, is assumed to be uncertain. This assumption is 

appropriate when all uncertain values of γj are assumed to be perfectly correlated and parameter 

sensitivity is calculated in Crystal Ball® by computing rank correlation coefficients between every 

assumption and the model output (Decisioneering 2001). 

215 
Table E-2. Summary of parameter values used in estimating electron doses to skin of face from 

dermal contamination by descending fallout 

Parameter Symbol Unit Deterministic 

value 

Uncertainty 

distributiona 

Peak exposure rate I R h–1 

Shot XRAY 7 × 10–5 b LU (I/2, I×2) 

Shot YOKE 5 × 10–4 b LU (I/2, I×2) 

Shot ZEBRA 4 × 10–5 b LU (I/2, I×2) 

Time of maximum exposure 

rate after detonation 

tmax h 

Shot XRAY 150b Constant 

Shot YOKE 42b Constant 

Shot ZEBRA 144b Constant 

Instrument reading bias km unitless 1.4 T (1.3, 1.4, 1.5) 

Gamma constant  R h–1 per 

Ci cm–2

Shot XRAY 0.0545 LU (/2, ×) 

Shot YOKE 0.0540 LU (/2, ×) 

Shot ZEBRA 0.0574 LU (/2, ×) 

Finite surface area bias kf unitless 

On ship 0.5 U (0.2, 0.8) 

On land 1.0 Constant 

Surface roughness bias kr unitless 

On ship 0.9 U (0.8, 1.0) 

On land 0.7 U (0.5, 0.9) 

Radioactive decay exponent x unitless 

Shot XRAY 0.545 N (0.545, 0.1) 

Shot YOKE 0.545 N (0.545, 0.1) 

Shot ZEBRA 1.1 N (1.1, 0.1) 

Time between contamination 

of skin and first shower 

ΔTpost h 15 U (6, 24) 

Interception and retention 

fraction for face 

r unitless 0.015 LN (0.015, 3.6) 

Particle-size adjustment PSa unitless 1.3 LN (1.3, 1.1) 

Enhancement due to moisture EM unitless 1.15 U (0.8, 1.5) 

Enrichment of specific activity EF unitless 1 T(1.0, 1.0, 2.0) 

Activity-weight adjustment AW unitless 1 T(0.7 ,1.0, 1.0) 

Table is continued on following page. 

216 
Table E-2. Summary of parameter values used in estimating electron doses to skin of face from 

dermal contamination by descending fallout (continued) 

Parameter Symbol Unit Deterministic 

value 

Uncertainty 

distributiona 

Dose rate factor at 7 mg cm-2 DRF rem h–1 per 

Ci cm–2 

3.7 T (1.6, 3.7, 6.8) 

Skin depth modification factor SDMF unitless 1.3 T (0.7, 1.3, 1.7) 

Fraction removed by washing 

per shower 

γ unitless 

1st shower γ1 0.85 T (0.7, 0.85, 1.0) 

2nd shower γ2 0.60 T (0.4, 0.6, 0.8) 

3rd shower γ3 0.25 T (0.1, 0.25, 0.4) 

≥ 4th shower γ4+ 0.02 T (0.005, 0.02, 0.035) 

Fraction removed by 

exfoliation of skin cells per 

showerc 

β unitless 0.05 T (0.025, 0.05, 0.07) 

a

 LU = Log-uniform (minimum, maximum); T = Triangular (minimum, mode, maximum); U = Uniform 

(minimum, maximum); N = Normal (mean, standard deviation); LN = Lognormal (median, geometric 

standard deviation). 

b

 Point estimate based on measurements after each shot. 

c

 Removal fraction for skin on upper limbs is assumed to apply to face. 

217 
Table E-3. Dimensions of typical ships of U.S. Navy (1940–1945)a 

Type of shipb Length (ft) Width (ft) 

Light aircraft carrier 

Independence Class

 (USS Independence)

622 109 

Escort carrier 

USS Bairoko CVE-115

(Commencement Bay class)

557 105 

Battleships 

South Dakota class 680 108 

Iowa class 888 108 

Light Cruiser 

Atlanta class 542 53 

Amphibious force command ships 

Mount McKinley Class (e.g., Estes AGC-12) 459 63 

Landing craft 

Landing Craft Infantry (Gunboat) – LCI(G) 160 23 

Ocean fleet tugboats 

ATF (e.g., COCOPA, MOLALA, 

TAWAKONI) 205 39 

Yard ships (YAG) 

Yard ships (YAG) 450 70 

Liberty type yard ship (YAG 39/YAG 40) 441 56 

Barges 70 35 

a

 Source: Personal communication from N. Barss, SAIC, August 24, 2004; 

see also “Ships of the U.S. Navy, 1940-1945,” available at 

http://www.ibiblio.org/hyperwar/USN/USN-ships.html. b

 List of typical vessels of the U.S. Navy. Not all such ships participated at 

Pacific nuclear weapons tests. 

218 
Table E-4. Deterministic and probabilistic estimates of electron doses to skin 

from dermal contamination by descending fallout for participants on ship 

stationed at Kwajalein Atoll during Operation SANDSTONE 

Electron dose to skin of face (rem) 

Deterministic Uncertainty distribution 

estimate 5th percentile 50th percentile Mean 95th percentile

Dose to time of first shower (D1) 

Shot XRAY 0.0032 0.00027 0.0036 0.014 0.050 

Shot YOKE 0.022 0.0020 0.025 0.083 0.37 

Shot ZEBRA 0.0017 0.00015 0.0019 0.0067 0.027 

TOTAL 0.027 0.0049 0.039 0.10 0.41

Uncertainty factor 

95th/50th 11 

95th/5th 85 

Dose after first shower (Dsh) 

Shot XRAY 0.0017 0.0 0.0016 0.0087 0.032 

Shot YOKE 0.0083 0.0 0.0088 0.038 0.16 

Shot ZEBRA 0.00063 0.0 0.00068 0.0028 0.012 

TOTAL 0.011 0.0 0.015 0.050 0.20

Uncertainty factor 

95th/50th 13 

95th/5th Not defined 

Total dose (DN = D1+Dsh)

Shot XRAY 0.0049 0.0005 0.0059 0.022 0.083 

Shot YOKE 0.030 0.0028 0.0370 0.12 0.52 

Shot ZEBRA 0.0023 0.00021 0.0028 0.0095 0.038 

TOTAL 0.037 0.0073 0.058 0.15 0.59

Uncertainty factor 

95th/50th 10 

95th/5th 80 

219 
Table E-5. Sensitivity analysis of probabilistic estimates of electron doses to skin of the face 

from dermal contamination by descending fallout from Shot YOKE for participants on ship 

stationed at Kwajalein Atoll during Operation SANDSTONE 

Contribution to uncertainty 

Parameter Dose to time of first 

shower (D1) 

Dose after first 

shower (Dsh) 

Total dose 

(DN = D1+Dsh) 

I 4.7% 3.2% 4.7% 

km 0.038% 0.019% 0.016% 

 5.2% 4.4% 5.5% 

kf 7.1% 4.5% 6.8% 

kr 0.27% 0.21% 0.29% 

x 0.016% 0.44% 0.018% 

ΔTpost 6.4% 0.0017% 3.2% 

r 66% 45% 67% 

PSa 0.39% 0.43% 0.45% 

EM 1.8% 1.1% 1.7% 

EF 1.5% 1.0% 1.5% 

AW 0.75% 0.18% 0.57% 

j 35% 3.0% 

 1.3% 0.066% 

2 7  cmmg

DRF 4.1% 2.2% 3.9% 

SDMF 1.6% 0.84% 1.5% 

220 
Table E-6. Deterministic and probabilistic estimates of electron doses to skin 

from dermal contamination by descending fallout for participants on land 

at Kwajalein Atoll during Operation SANDSTONE 

Electron dose to skin of face (rem) 

Deterministic Uncertainty distribution 

estimate 5th percentile 50th percentile Mean 95th percentile

Dose to time of first shower (D1) 

Shot XRAY 0.0021 0.00017 0.0022 0.0077 0.028 

Shot YOKE 0.014 0.0012 0.015 0.047 0.19 

Shot ZEBRA 0.0011 0.00011 0.0012 0.0039 0.015 

TOTAL 0.017 0.0033 0.024 0.058 0.22

Uncertainty factor 

95th/50th 9 

95th/5th 67 

Dose after first shower (Dsh) 

Shot XRAY 0.0011 0.0 0.0010 0.0048 0.019 

Shot YOKE 0.0053 0.0 0.0053 0.021 0.088 

Shot ZEBRA 0.00041 0.0 0.00039 0.0016 0.0070 

TOTAL 0.0068 0.0 0.09 0.028 0.11

Uncertainty factor 

95th/50th 12 

95th/5th Not defined 

Total dose (DN = D1+Dsh)

Shot XRAY 0.0031 0.00029 0.0035 0.013 0.048 

Shot YOKE 0.019 0.0018 0.023 0.068 0.27 

Shot ZEBRA 0.0015 0.00016 0.0017 0.0054 0.021 

TOTAL 0.024 0.0048 0.035 0.086 0.31

Uncertainty factor 

95th/50th 9 

95th/5th 65 

221 
Table E-7. Sensitivity analysis of probabilistic estimates of electron doses to skin of the face 

from dermal contamination by descending fallout from Shot YOKE for participants on land 

at Kwajalein Atoll during Operation SANDSTONE 

Contribution to uncertainty 

Parameter Dose to time of first 

shower (D1) 

Dose after first 

shower (Dsh) 

Total dose 

(DN = D1+Dsh) 

I 5.1% 3.5% 5.1% 

km 0.049% 0.014% 0.025% 

 5.7% 4.8% 5.9% 

kf N/A N/A N/A 

kr 1.0% 0.82% 1.0% 

x 0.010% 0.46% 0.027% 

ΔTpost 6.6% 0.0001% 3.2% 

r 71% 46% 71% 

PSa 0.37% 0.40% 0.43% 

EM 1.9% 1.1% 1.9% 

EF 1.2% 0.87% 1.2% 

AW 0.77% 0.17% 0.58% 

j 37% 3.5% 

 1.3% 0.051% 

2 7 cmmg

DRF 4.7% 2.4% 4.5% 

SDMF 1.9% 1.0% 1.8 

222 
E.3 References 

Apostoaei, A.I., Nair, S.K., Thomas, B.A., Lewis, C.J., Hoffman, F.O., and Thiessen, K.M. 

External exposure to radionuclides accumulated in the shoreline sediments with an 

application to the lower Clinch River. Health Phys. 78(6):700–710; 2000. 

Burson Z.G. and Profio A.E. Structure shielding in reactor accidents. Health Phys. 33:287–299; 

1977. 

Charles M.W. The biological bases of radiological protection criteria for superficial, low 

penetrating radiation exposure. Radiation Protection Dosimetry 14(2):79–90. 1986. 

Decisioneering, Inc. Crystal Ball® 2000.2 User Manual. Decisioneering, Inc., Denver, 

Colorado; 2001. 

Eckerman K.F. and Ryman J.C. External Exposure to Radionuclides in Air, Water, and Soil, 

Federal Guidance Report No. 12, EPA-402-93-081. Office of Radiation and Indoor Air, U.S. 

Environmental Protection Agency, Washington, DC; 1993. 

Egbert S.D., Kaul D.C., Klemm J., and Phillips J.C. FIIDOS – A Computer Code for 

Computation of Fallout Inhalation and Ingestion Dose to Organs: Computer User’s Guide, 

DNA-TR-84-375. Science Applications International Corporation, McLean, Virginia; 1985. 

International Commission on Radiological Protection (ICRP). Report of the Task Group on 

Reference Man, ICRP Publication 23. Pergamon Press, Oxford, U.K.; 1975. 

Kocher D.C. and Eckerman K.F. Electron dose-rate conversion factors for external exposure of 

the skin from uniformly deposited activity on the body surface. Health Phys. 53(2):135–141; 

1987. 

McArthur R.D. Radionuclides in Surface Soil at the Nevada Test Site, Water Resources Center 

Publication #45077, DOE/NV/10845-02. Desert Research Institute, Las Vegas, Nevada; 

1991 (August). 

Miller C.F. The Contamination Behavior of Fallout-like Particles Ejected by Volcano Irazu. 

Stanford Research Institute, Menlo Park California; 1966a (April). 

Miller C.F. Operation CENIZA-ARENA. The Retention of Fallout Particles from Volcan Irazu 

(Costa Rica) by Plants and People, Part One. Stanford Research Institute, Menlo Park, 

California; 1966b (January). 

Miller C.F. Operation CENIZA-ARENA. The Retention of Fallout Particles from Volcan Irazu 

(Costa Rica) by Plants and People, Part Two. Stanford Research Institute, Menlo Park, 

California; 1966c (December). 

Miller C.F. Operation CENIZA-ARENA. The Retention of Fallout Particles from Volcan Irazu 

(Costa Rica) by Plants and People, Part Three. Stanford Research Institute, Menlo Park, 

California; 1967 (December). 

Miller C.F. Some Properties of Radioactive Fallout: Tower Detonations Diablo and Shasta, URS 

757-3. URS Research Company; Burlingame, California; 1969 (August). 

NRC (National Research Council). A Review of the Dose Reconstruction Program of the 

Defense Threat Reduction Agency. The National Academies Press, Washington, DC; 2003. 

223 
224 

NRC (National Research Council). Review of the Methods Used to Assign Radiation Doses to 

Service Personnel at Nuclear Weapons Tests. National Academy Press, Washington, DC; 

1985. 

Whitton J.T. New values for epidermal thickness and their importance. Health Phys. 24:1–8; 

1973. 
 

 DISTRIBUTION LIST 

 DTRA-TR-09-16 

 Additional copies are available at: 

 http://www.dtra.mil/SpecialFocus/NTPR/PRandAtomic.aspx

DEPARTMENT OF DEFENSE 

Defense Technical Information Center 

8725 John J. Kingman Road, Suite 0944 

Fort Belvoir, VA 22060-6201 

ATTN: DTIC/OCA 

Defense Threat Reduction Agency 

8725 John J. Kingman Road, RD-NTSN 

Fort Belvoir, VA 22060-6201

Defense Threat Reduction Information Analysis Center 

8725 John J. Kingman Road, OP-CSUI 

Fort Belvoir, VA 22060-6201

DEPARTMENT OF VETERANS AFFAIRS 

Department of Veterans Affairs (DVA) 

Chief, Public Health & Environmental Hazards 

VA Central Office (13) 

810 Vermont Ave., NW 

Washington, DC 20420 

DEPARTMENT OF LABOR 

U. S. Department of Labor, DEEOIC 

200 Constitution Avenue NW, Room C-3321 

Washington, DC 20210 

FEDERAL AGENCY ADVISORY BOARDS

Veterans' Advisory Board on Dose Reconstruction (VBDR) 

801 North Quincy Street, Suite 600 

Arlington, VA 22203 

225
226

Veterans’ Advisory Committee on Environmental Hazards 

Department of Veterans Affairs 

Compensation & Pension Service (211) 

810 Vermont Avenue, NW 

Washington, DC 20420 

DEPARTMENT OF DEFENSE CONTRACTORS 

L-3 Communications 

11410 Isaac Newton Square North, Suite 103 

Reston, VA 20190-5005 

ATTN: Ms. Hilda Maier 

National Council on Radiation Protection and Measurements (NCRP) 

7910 Woodmont Ave., Suite 400 

Bethesda, MD 20814-3095 

ATTN: Dr. Thomas Tenforde 

Oak Ridge Associated Universities (ORAU) 

9950 W. 80Th Ave. 

Arvada, CO 80005 

ATTN: Ms. Nancy Daugherty, CHP 

Science Applications International Corporation (SAIC) 

8301 Greensboro Drive, M/S E-5-5 

McLean, VA 22102 

ATTN: Dr. Mondher Chehata 

Specialists in Energy, Nuclear & Environmental Sciences 

(SENES) Oak Ridge 

102 Donner Drive 

Oak Ridge, TN 37830 

ATTN: Dr. David C. Kocher