INHALATION DOSE ASSESSMENT: RISK ASSESSMENT OF AIRBORNE PARTICULATES TO WORKERS IN THE FLORIDA PHOSPHATE INDUSTRY By KWANG PYO KIM A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2005 Copyright 2005 by Kwang Pyo Kim This document is dedicated to Dr. William Emmett Bolch who passed away on December 26, 2003. ACKNOWLEDGMENTS The study could not have been accomplished without the valuable assistance of many individuals. Here, I want to acknowledge those people once more. I would like to express my deep appreciation to my advisor, Dr. Wesley E. Bolch, who not only guided and supported me as my advisor but also encouraged and challenged me throughout my academic program. I appreciate the opportunity that he has provided me to study at University of Florida and pursue my interest in health physics. I wish to express my gratitude to Dr. Chang-Yu Wu. He provided me expertise and direction to complete this study. Great appreciation should go to Dr. William Emmett Bolch, who passed away on December 26, 2003. His long experience and wide and deep knowledge in the field of environmental physics led me to successful completion of this study. My thanks also go to my committee members, Dr. David E. Hintenlang and Dr. Guenther Hochhaus, for reading this dissertation and providing many valuable comments that improved this study. This work was supported by Grant #00-05-062R and #03-05-064 from The Florida Institute of Phosphate Research (FIPR) to the University of Florida. Dr. Brian K. Birky, Research Director for Public Health, was very supportive of this research, and his guidance and advice were important for its successful completion. Many samplings were made in different plants and areas to obtain site-specific air sampling data. This activity was greatly facilitated by many individuals: Allan Pratt, Michael Messina, and Robert Sellers in CF industries, Debra Waters, Ryan Richards, iv Melody R. Foley, Tara Crews, Taylor D. Abel, Nelson Singletary, Santino Provenzano, and Flint Barnes in Mosaic Company, Martin St. John and Dennis Killebrew in PCS Phosphate, and Ron Brunk and Foster Thorpe in US Agri-Chemicals. They provided me safety training, escort, and valuable information. Wesley Nall, Tom McNally, and Robert Ammons in Health Unit in Winter Haven, Florida, conducted pre-sampling. Their efforts are greatly appreciated. Many thanks go out to all of my colleagues at the Department of Nuclear and Radiological Engineering, especially Dr. Chulhaeng Huh, Dr. Choonsik Lee, Dr. Eunyoung Han, Choonik Lee, Hosang Jin, and Heeteak Chung for their help and friendship. Yu-Mei Hsu at Departments of Environmental Engineering Sciences instructed me in the use of ion chromatography and helped its operation. I also wish to acknowledge the help of department faculty and staff in Nuclear and Radiological Engineering. I thank my and my wife’s parents and family for their support. My mother deserves to have my respect and love. She gave love, unconditional support, and encouragement for me to live right. Last, I would like to thank my wife for her understanding, patience, and love. v TABLE OF CONTENTS page U ACKNOWLEDGMENTS.................................................................................................iv T T LIST OF TABLES.............................................................................................................ix T T LIST OF FIGURES..........................................................................................................xii T T ABSTRACT.....................................................................................................................xiv T T T CHAPTER 1 INTRODUCTION...................................................................................................1 1.1 Objective......................................................................................................1 1.1.1 Source and Magnitude of Problem..................................................1 1.1.2 Review of Pertinent Literature and Related Work...........................2 1.1.3 Specific Goals..................................................................................3 1.1.4 Impact of Goals................................................................................3 1.2 Methodology................................................................................................4 1.2.1 Task 1: Particle Characterization.....................................................4 1.2.2 Task 2: Effective Dose Scaling Factors...........................................5 1.2.3 Task 3: Dose Assessment via Characterization of Particle Size Distribution......................................................................................6 1.2.4 Task 4: Particle Solubility in Lung Fluid.........................................7 1.2.5 Task 5: Risk Assessment to Workers...............................................7 2 CHARACTERIZATION OF RADIOACTIVE AEROSOLS IN FLORIDA PHOSPHATE PROCESSING FACILITIES.........................................................11 2.1 Introduction................................................................................................11 2.2 Materials and Methods...............................................................................15 2.2.1 Dose Sensitivity to Aerosol Parameters.........................................15 2.2.2 Particle Size Distribution...............................................................16 2.2.3 Particle Density, Shape and Elemental Composition....................18 2.2.4 Particle Radioactivity.....................................................................19 2.3 Results and Discussion..............................................................................20 2.3.1 Dose Sensitivity to Particle Properties...........................................20 2.3.2 Particle Size Distribution...............................................................22 2.3.3 Particle Density, Shape, and Elemental Composition...................25 vi 2.3.4 Particle Radioactivity.....................................................................28 2.4 Conclusions................................................................................................30 3 EFFECTIVE DOSE SCALING FACTORS FOR USE WITH CASCADE IMPACTOR SAMPLING DATA IN TENORM INHALATION EXPOSURES45 3.1 Introduction................................................................................................45 3.2 Materials and Methods...............................................................................48 3.2.1 Cutoff Size of the Cascade Impactor.............................................48 3.2.2 Other Particle Properties................................................................49 3.2.3 Radioactivity Distribution within a Sub-stage...............................50 3.2.4 TENORM Radionuclides...............................................................51 3.2.5 Dose Calculation............................................................................52 3.3 Results and Discussion..............................................................................54 3.3.1 Inhalation Dose Coefficients – Variation as a Function of Particle Size...................................................................................54 3.3.2 Effective Dose Scaling Factors for Uniform Distributions............57 3.3.3 Effective Dose Scaling Factors for Linear Distributions...............59 3.3.4 Applications of Effective Dose Scaling Factor to Measured Cascade Impactor Data..................................................................61 3.4 Conclusions................................................................................................63 4 EFFECTIVE DOSE SCALING FACTORS FOR USE WITH CASCADE IMPACTOR SAMPLING DATA IN EXPOSURES TO URANIUM SERIES (APPLICATION TO IMBA PROGRAM)............................................................87 4.1 Introduction................................................................................................87 4.2 Materials and Methods...............................................................................88 4.3 Results and Discussion..............................................................................89 4.3.1 Inhalation Dose Coefficients..........................................................89 4.3.2 Comparison of Inhalation Dose Coefficients from IMBA and LUDEP...........................................................................................91 4.3.3 Effective Dose Scaling Factors......................................................93 4.4 Conclusions................................................................................................94 5 INFLUENCE OF PARTICLE SIZE DISTRIBUTION ON INHALATION DOSES TO WORKERS IN THE FLORIDA PHOSPHATE INDUSTRY........108 5.1 Introduction..............................................................................................108 5.2 Materials and Methods.............................................................................109 5.2.1 Inhalation Dose Coefficients........................................................110 5.2.2 Inhalation Effective Doses to Workers........................................112 5.3 Results and Discussion............................................................................114 5.3.1 Inhalation Dose Coefficients........................................................114 5.3.2 Inhalation Effective Dose to Workers..........................................118 5.4 Conclusions..............................................................................................121 vii 6 DETERMINATION OF LUNG SOLUBILITY OF RADIONUCLIDES IN PARTICLES IN FLORIDA PHOSPHATE PROCESSING FACILITIES.........137 6.1 Introduction..............................................................................................137 6.2 Materials and Methods.............................................................................141 6.2.1 Dose Sensitivity to Radionuclide Solubility................................141 6.2.2 Tested Samples............................................................................141 6.2.3 In vitro Solubility Test................................................................142 6.2.4 Solubility of Surrounding Material..............................................143 6.2.5 Solubility of Uranium, Thorium, and Lead.................................144 6.2.6 Data Analysis...............................................................................145 6.3 Results and Discussion............................................................................147 6.3.1 Dose Sensitivity to Radionuclide Solubility................................147 6.3.2 Lung Solubility of Particles.........................................................148 6.4 Conclusions..............................................................................................151 7 RISK ASSESSMENT OF AIRBORNE PARTICULATES TO WORKERS IN THE FLORIDA PHOSPHATE INDUSTRY......................................................160 7.1 Introduction..............................................................................................160 7.2 Materials and Methods.............................................................................161 7.3 Results and Discussion............................................................................162 7.4 Conclusions..............................................................................................164 8 CONCLUSIONS AND RECOMMENDATIONS..............................................170 8.1 Conclusions..............................................................................................170 8.2 Recommendations....................................................................................174 APPENDIX A PARTICLE SAMPLING AND RADIOACTIVITY DATA USED FOR DOSE ASSESSMENT....................................................................................................175 B EFFECTIVE DOSE SCALING FACTORS APPLICABLE TO PARTICLES IN THE FLORIDA PHOSPHATE CHEMICAL PLANTS................................195 LIST OF REFERENCES.................................................................................................201 BIOGRAPHICAL SKETCH...........................................................................................210 viii LIST OF TABLES Table page U U U U 2-1 ICRP 66 HRTM default aerosol parameters and input aerosol parameters for dose sensitivity study...............................................................................................32 2-2 Active operational systems and ventilation conditions during airborne particle sampling at the various storage areas.......................................................................33 2-3 Mass density of bulk products, settled particles, and airborne particles..................34 2-4 Composition information for dry product ingredients.............................................35 2-5 Phosphorus, silicon, and sulfur composition in different sized particles.................36 2-6 238U, 226Ra, and 210Pb radioactivity concentrations in bulk dry products, settled P P P P P P particles, and airborne particles................................................................................37 3-1 Particle size information for each impactor stage of the University of Washington Mark III cascade impactor...................................................................65 3-2 Reference physiological parameter values for reference worker.............................66 3-3 GI tract absorption factors (f ) for uranium series elements....................................67 1 B B 3-4 LUDEP decay-chain option for each radionuclide..................................................68 3-5 Inhalation effective dose scaling factors (SF ) for a uniform activity distribution..69 E B B 3-6 Inhalation effective dose scaling factors (SF ) for a linearly decreasing activity E B B distribution (AR of 2:1)............................................................................................70 3-7 Inhalation effective dose scaling factors (SF ) for a linearly decreasing activity E B B distribution (AR of 5:1)............................................................................................71 3-8 Inhalation effective dose scaling factors (SF ) for a linearly increasing activity E B B distribution (AR of 1:2)............................................................................................72 3-9 Inhalation effective dose scaling factors (SF ) for a linearly increasing activity E B B distribution (AR of 1:5)............................................................................................73 ix 3-10 Example inhalation dose assessment under the assumption of mono-size, uniform, or linearly changing radioactivity distribution per impactor stage............74 4-1 Inhalation effective dose scaling factors (SF ) for a uniform activity distribution..96 E B B 4-2 Inhalation effective dose scaling factors (SF ) for a linearly decreasing activity E B B distribution (AR of 2:1)............................................................................................97 4-3 Inhalation effective dose scaling factors (SF ) for a linearly decreasing activity E B B distribution (AR of 5:1)............................................................................................98 4-4 Inhalation effective dose scaling factors (SF ) for a linearly increasing activity E B B distribution (AR of 1:2)............................................................................................99 4-5 Inhalation effective dose scaling factors (SF ) for a linearly increasing activity E B B distribution (AR of 1:5)..........................................................................................100 6-1 Samples employed for solubility test.....................................................................153 6-2 Composition of serum ultrafiltrate simulant..........................................................154 6-3 Retention fitting data of 238U, 232Th, and 208Pb in serum ultrafiltrate as a function P P P P P P of time....................................................................................................................155 7-1 Inhalation effective dose scaling factors (SF ) applicable to particles in the E B B Florida phosphate chemical plants.........................................................................166 7-2 Dose rate and annual inhalation dose to workers in the Florida phosphate chemical plants due to particle inhalation..............................................................168 7-3 Occupancy times for workers at dry product, shipping, and storage areas in the Florida phosphate chemical plants.........................................................................169 A-1 Particle size distribution and radionuclide concentration (Granulator area)..........177 A-2 Particle size distribution and radionuclide concentration (Storage area)...............184 A-3 Particle size distribution and radionuclide concentration (Shipping area).............190 B-1 Effective dose scaling factors (SF ) applicable to particles in the Florida E B B phosphate chemical plants for uniform radioactivity distribution.........................196 B-2 Effective dose scaling factors (SF ) applicable to particles in the Florida E B B phosphate chemical plants for linearly decreasing radioactivity distribution (AR = 2:1)......................................................................................................................197 B-3 Effective dose scaling factors (SF ) applicable to particles in the Florida E B B phosphate chemical plants for linearly decreasing radioactivity distribution (AR = 5:1)......................................................................................................................198 x