Formation and Enhanced Toxicity As a Function
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IODINATED X-RAY CONTRAST MEDIA (ICM) AS PRECURSORS TO DISINFECTION BYPRODUCT (DBP) FORMATION AND ENHANCED TOXICITY AS A FUNCTION OF pH AND CHLORINATED OXIDANTS A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfilment Of the Requirements for the Degree Master of Science Alexis Helen Killinger May, 2016 IODINATED X-RAY CONTRAST MEDIA (ICM) AS PRECURSORS TO DISINFECTION BYPRODUCT (DBP) FORMATION AND ENHANCED TOXICITY AS A FUNCTION OF pH AND CHLORINATED OXIDANTS Alexis Helen Killinger Thesis Approved: Accepted: ______________________________ ______________________________ Advisor Interim Dean of the College Dr. Stephen Duirk Dr. Eric J. Amis ______________________________ ______________________________ Faculty Reader Dean of the Graduate School Dr. Teresa Cutright Dr. Chand K. Midha ______________________________ ______________________________ Faculty Reader Date Dr. Lan Zhang ______________________________ Department Chair Dr. Wieslaw Binienda ii ABSTRACT The objective of this study was to investigate the formation of iodinated disinfection by-products (iodo-DBPs) and mammalian cell cyto/genotoxicity in the presence of iodinated x-ray contrast media (ICM), chlorinated oxidants, and natural organic matter (NOM). The ICM chosen as the source of iodide for these experiments were iopamidol and iohexol. The experiments were conducted with aqueous chlorine or monochloramine as the chlorinated oxidant. The experiments were conducted at pH 6.5 - 9.0. The NOM concentration was constant [DOC] = 5.57 mg/L. Chloroform formation in the presence of iopamidol, a regulated DBP, was highest at pH 9.0 with aqueous chlorine (up to 4014 nM) and pH 6.5 with monochloramine (up to 56 nM). Additionally, dichloroiodomethane followed a similar trend in the presence of iopamidol with concentrations in the chlorine experiments forming up to 650 nM and the monochloramine experiments forming up to 52 nM. Trichloroacetic acid (TCAA) formation generally decreased as pH increased; however, iopamidol significantly contributes to TCAA formation at pH 7.5 disrupting the normally observed TCAA formation trend in the presence of NOM. Toxicity of the iopamidol transformation in the presence of chlorinated oxidants and NOM was also investigated. The cytotoxicity index (CTI) values were highest for chlorine (i.e., 21.0) and monochloramine (i.e., 16.5) when compared to control experiments without iopamidol. Genotoxicity index (GTI) values were highest for chlorine (i.e., 7.1) and monochloramine (i.e., 3.5) when compared to control experiments. Iohexol DBP experiments resulted in an enhanced formation of iii chloroform, while very little dichloroiodomethane formed, and the TCAA formation observed was comparable to the chlorinated source water controls. With iohexol as the iodide source, the CTI and GIT values were highest with aqueous chlorine at 21.6 and 3.8, respectively, when compared to control experiments without iohexol present. Iopamidol acts as a precursor to DBP formation, while also enhancing mammalian cell cytotoxicity and genotoxicity after chlorine or chloramine disinfection. While iohexol formed regulated and unregulated DBPs, it also enhanced mammalian cell cytotoxicity and genotoxicity, though to a lesser extent than iopamidol. iv ACKNOWLEDGEMENTS I would like to express my sincere appreciations to my advisor, Dr. Stephen Duirk, for his support, guidance, and advice throughout my master’s studies. I would also like to thank Dr. Teresa Cutright for her teachings and direction over the past few years. Thank you to my committee, as well, for their support and advice: Dr. Stephen Duirk, Dr. Teresa Cutright, and Dr. Lan Zhang. Additionally, thank you to all of my laboratory associates, and friends, for all of the lessons and collaboration during this research: Elizabeth Crafton, Edward Machek, and Nana Ackerson. Finally, my deepest gratitude is felt for my parents, Dave and Cathy Killinger, my sister, Sydney Killinger, and my boyfriend, Sean Edwards, for all of their unconditional love, support, and advice. v TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................. ix LIST OF FIGURES ......................................................................................................... xiv CHAPTER I INTRODUCTION ............................................................................................................ 1 1.1 Background ............................................................................................................... 1 1.2 Problem Statement .................................................................................................... 4 1.3 Specific Objectives .................................................................................................... 5 II LITERATURE REVIEW ................................................................................................ 7 2.1 Iodinated X-Ray Contrast Media .............................................................................. 7 2.2 Occurrence of ICM in Water and Wastewater .......................................................... 8 2.3 Disinfection and Disinfection By-Products (DBPs)................................................ 10 2.3.1 Chemical Oxidants Used in Drinking Water Treatment .................................. 10 2.3.2 Disinfection By-Product (DBP) Formation with Natural Organic Matter (NOM) ....................................................................................................................... 11 2.3.3 Aqueous Chlorine Disinfection and DBP Formation with Micropollutants .... 13 2.3.4 Chloramine Disinfection and DBP Formation ................................................. 15 2.4 ICM Transformation and Iodo-DBP Formation...................................................... 17 2.4.1 ICM Transformation ......................................................................................... 17 2.4.2 Microbial Transformation of ICM .................................................................... 17 2.4.3 Chemical Transformation of ICM .................................................................... 18 vi 2.5 Toxicity of DBPs ..................................................................................................... 20 2.5.1 TOX Toxicity ................................................................................................... 22 III MATERIALS AND METHODS ................................................................................. 25 3.1 Chemicals and Reagents.......................................................................................... 25 3.2 Source Water Characterization................................................................................ 26 3.3 Experimental Methods ............................................................................................ 31 3.3.1 Disinfection By-Product Experiments with Source Water ............................... 31 3.3.2 Cytotoxicity and Genotoxicity Experiments with Source Water ..................... 34 3.3.3 Disinfection By-Product Analytical Methods .................................................. 37 3.4 Analysis of DBPs .................................................................................................... 39 IV RESULTS AND DISCUSSION .................................................................................. 56 4.1 Introduction ............................................................................................................. 56 4.2 DBP Formation in the Presence of ICM and Chlorinated Oxidants ....................... 57 4.2.1 DBP Formation in the presence of Aqueous Chlorine and Iopamidol ............. 57 4.2.2 Akron Kinetics Experiments in the presence of Aqueous Chlorine and Iopamidol ................................................................................................................... 63 4.2.3 DBP Formation in the presence of Monochloramine and Iopamidol ............... 69 4.2.4 Akron Kinetics Experiments in the presence of Monochloramine and Iopamidol ................................................................................................................... 74 4.2.5 DBP Formation in the presence of Aqueous Chlorine and Iohexol ................. 79 4.3 Chronic Cytotoxicity and Acute Genotoxicity Analysis for ICM in the Presence of Chlorinated Oxidants and Akron Source Water ............................................................ 83 4.3.1 Cyto/Genotoxicity of Iopamidol in the presence of Chlorinated Oxidants ...... 84 4.3.2 Cyto/Genotoxicity of Iohexol in the presence of Aqueous Chlorine ............... 95 V CONCLUSIONS AND RECOMMENDATIONS ..................................................... 104 5.1 Introduction ........................................................................................................... 104 vii 5.2 Conclusions ........................................................................................................... 104 5.3 Recommendations ................................................................................................. 106 BIBLIOGRAPHY ........................................................................................................... 107 APPENDIX ..................................................................................................................... 124 viii LIST OF TABLES Table Page 3.1: Source water characteristics for Akron water ...........................................................