Health Risk Considerations for the Use of Unencapsulated Steel Slag (2023)

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HEALTH RISK CONSIDERATIONS FOR THE USE OF UNENCAPSULATED STEEL SLAG Committee on Electric Arc Furnace Slag: Understanding Human Health Risks from Unencapsulated Uses Board on Environmental Studies and Toxicology Division on Earth and Life Studies Consensus Study Report 

NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001 This activity was supported by Contract No. 68HERC19D0011 between the National Academy of Sciences and the U.S. Environmental Protection Agency. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any organization or agency that provided support for the project. International Standard Book Number-13: 978-0-309-70011-5 International Standard Book Number-10: 0-309-70011-6 Digital Object Identifier: https://doi.org/10.17226/26881 Library of Congress Catalog Number: 2023919469 This publication is available from the National Academies Press, 500 Fifth Street, NW, Keck 360, Washington, DC 20001; (800) 624-6242 or (202) 334-3313; http://www.nap.edu. Copyright 2023 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and National Academies Press and the graphical logos for each are all trademarks of the National Academy of Sciences. All rights reserved. Printed in the United States of America. Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2023. Health Risk Considerations for the Use of Unencapsulated Steel Slag. Washington, DC: The National Academies Press. https://doi.org/10.17226/26881. 

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COMMITTEE ON ELECTRIC ARC FURNACE SLAG: UNDERSTANDING HUMAN HEALTH RISKS FROM UNENCAPSULATED USES Members AARON BARCHOWSKY (Chair), University of Pittsburgh, Pittsburgh, PA MICHAEL ASCHNER, Albert Einstein College of Medicine, Bronx, NY DANIEL BAIN, University of Pittsburgh, Pittsburgh, PA SIMONE CHARLES, University of Michigan, Ann Arbor, MI ALAN CRAMB, Illinois Institute of Technology, Chicago, IL NATASHA DEJARNETT, University of Louisville, Louisville, KY (until November 21, 2022) REBECCA FRY, University of North Carolina, Chapel Hill, NC PHILIP GOODRUM, GSI Environmental Inc., Fayetteville, NY JOHN KISSEL, University of Washington, Seattle, WA DEB NIEMEIER, University of Maryland, College Park, MD PEGGY O’DAY, University of California, Merced, CA RUTH O’DONNELL, Private citizen, Waukesha, WI REBECCA PARKIN, The George Washington University, Washington, DC DAVID WALKER, Columbia University, Palisades, NY ROBERT WRIGHT, Icahn School of Medicine at Mount Sinai, New York, NY Staff RAYMOND WASSEL, Scholar and Responsible Staff Officer CLIFFORD S. DUKE, Director, Board on Environmental Studies and Toxicology KATHRYN GUYTON, Senior Program Officer (until May 2, 2023) NATALIE ARMSTRONG, Associate Program Officer (until December 20, 2022) ANTHONY DEPINTO, Associate Program Officer LESLIE BEAUCHAMP, Senior Program Assistant THOMASINA LYLES, Senior Program Assistant Sponsor U.S. ENVIRONMENTAL PROTECTION AGENCY v 

BOARD ON ENVIRONMENTAL STUDIES AND TOXICOLOGY Members FRANK W. DAVIS (Chair), University of California, Santa Barbara, CA DANA BOYD BARR, Emory University, Atlanta, GA ANN M. BARTUSKA, U.S. Department of Agriculture (retired), Washington, DC WEIHSUEH A. CHIU, Texas A&M University, College Station, TX FRANCESCA DOMINICI, Harvard University, Boston, MA MAHMUD FAROOQUE, Arizona State University, Tempe, AZ R. JEFFREY LEWIS, ExxonMobil Biomedical Sciences, Inc., Annandale, NJ MARIE LYNN MIRANDA, University of Notre Dame, Notre Dame, IN MELISSA J. PERRY, George Mason University, Fairfax, VA REZA J. RASOULPOUR, Corteva Agriscience, Indianapolis, IN JOSHUA TEWKSBURY, Smithsonian Tropical Research Institute, Panamá SACOBY M. WILSON, University of Maryland, College Park, MD TRACEY JEAN WOODRUFF, University of California, San Francisco, CA Staff CLIFFORD S. DUKE, Director RAYMOND WASSEL, Scholar KATHRYN GUYTON, Senior Program Officer NATALIE ARMSTRONG, Associate Program Officer ANTHONY DEPINTO, Associate Program Officer LAURA LLANOS, Finance Business Partner LESLIE BEAUCHAMP, Senior Program Assistant THOMASINA LYLES, Senior Program Assistant KATHERINE KANE, Program Assistant vi 

Reviewers This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We thank the following individuals for their review of this report: HUGH BARTON, Independent Consultant DEBORAH BENNETT, University of California, Davis SUSAN BRANTLEY, Pennsylvania State University THURE CERLING, University of Utah EDMUND CROUCH, Green Toxicology LLC DAVID DORMAN, North Carolina State University HERMAN GIBB, Gibb & O’Leary Epidemiology Consulting KURUNTHACHALAM KANNAN, New York State Department of Health JOHN YZENAS JR., J. Yzenas Consulting, LLC Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report, nor did they see the final draft before its release. The review of this report was overseen by DAVID L. EATON (NAM), University of Washington, and CORALE L. BRIERLEY (NAE), Brierley Consultancy LLC. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies. vii 



Contents ACRONYMS AND ABBREVIATIONS ................................................................................................ xiii SUMMARY ................................................................................................................................................. 1 1 INTRODUCTION ................................................................................................................................ 7 Steelmaking and Electric Arc Furnace Slag, 7 Study Background, 7 Committee’s Statement of Task and Approach, 8 Organization of the Report, 9 2 ELECTRIC ARC FURNACE STEELMAKING AND SLAG FORMATION, COMPOSITION, AND DISTRIBUTION........................................................................................ 11 Steel Production and Slag Formation in an Electric Arc Furnace, 11 Slag Composition, 14 Slag Processing, Distribution, and Use, 16 Geographic Distribution of Electric Arc Furnace Facilities and Slag Processors, 17 State Government Oversight of Slag Use, 20 Summary, 21 3 PROPERTIES AND ENVIRONMENTAL DYNAMICS OF SLAG ............................................ 23 Mineralogy and Mineralogical Phases of Slag Solidification, 23 Trace Constituents in Slag, 26 Organic Pollutants from Plastic Materials Mixed with Scrap Steel, 29 Weathering and Mechanical Degradation of Slag, 32 Environmental Weathering of Slag, 33 Mechanical Degradation of Slag, 34 Release and Environmental Transport of Trace Slag Constituents, 36 Leaching and Mobilization of Trace Elements by Water, 39 Summary, 43 4 HUMAN EXPOSURE TO UNENCAPSULATED ELECTRIC ARC FURNACE SLAG ......... 45 Conceptual Site Model, 45 Average Daily Dose Equations, 47 Bioaccessibility and Bioavailability, 49 Key Exposure Variables for Further Evaluation, 50 Summary, 52 5 TOXICITY OF SELECTED SLAG CONSTITUENTS ................................................................. 53 Chromium, 54 Manganese, 58 Summary, 65 6 MULTIPLE STRESSORS IN DISADVANTAGED COMMUNITIES WHERE UNENCAPSULATED SLAG MAY BE USED ............................................................................... 67 Cumulative Exposures, 67 ix 

x Contents Societal Inequities and Cumulative Exposures, 67 Demographic Considerations, 70 Summary, 71 7 SYNTHESIS OF RISK CONSIDERATIONS FOR UNENCAPSULATED ELECTRIC ARC FURNACE SLAG USES .......................................................................................................... 76 Previous Risk Assessments on Electric Arc Furnace Slag, 76 Hazard Ranking of Constituents in Electric Arc Furnace Slag, 78 Risk Factors and Data Needs, 83 Priority Research Needs, 86 REFERENCES .......................................................................................................................................... 88 APPENDIXES A COMMITTEE MEMBER BIOGRAPHIES .................................................................................. 109 B OPEN SESSION AGENDAS........................................................................................................... 114 C EAF STEEL FACILITIES .............................................................................................................. 117 D SLAG PROCESSING FACILITIES .............................................................................................. 121 E SLAG MINERALOGY .................................................................................................................... 125 F REVIEW OF PAST RISK ASSESSMENTS OF ELECTRIC ARC FURNACE SLAG .......... 131 BOXES, FIGURES, AND TABLES BOXES S-1 Key Risk Factors and Data Needs, 3 1-1 Statement of Task, 9 3-1 Potential Hazard of Slag Mineral Components: Examples, 24 7-1 Key Risk Factors and Data Needs, 84 FIGURES S-1 Illustrative example of a conceptual site model for human exposure to chemicals of potential concern released from slag applied in residential settings, 2 2-1 A schematic of the EAF, 11 2-2 Distribution of EAF steelmaking facilities and slag processing facilities in the United States, 19 3-1 Gravel-size steel slag particle with a lime pocket, 25 3-2a Concentrations of chromium (Cr) and manganese (Mn) in ferrous slags, 27 3-2b Concentrations of arsenic (As) and lead (Pb) in ferrous slags, 27 

Contents xi 3-2c Concentrations of vanadium (V) and molybdenum (Mo) in ferrous slags, 28 3-3 Comparison of the concentrations measured at an air sampling site, 30 3-4 Variation of stack-gas and ambient air gas-phase percentages of PCBs, PAHs, and PBDEs with octanol–air partition coefficients, 31 4-1 Illustrative example of a CSM for human exposure to COPCs released from slag applied in residential settings, 46 4-2 Conceptual framework for definitions of bioaccessibility and bioavailability, 50 6-1 Allegheny County, Pennsylvania, percent Black by census block group and Allegheny County Community Need Index, 72 6-2 Percent non-White by census block group in Pueblo County, Colorado, 73 6-3 Medically underserved areas, historically redlined zones, and opportunity zones in Pueblo, Colorado, 74 6-4 Multiple stressors relative to redlining in Pueblo, Colorado, 75 7-1 Constituent profiles for EAF slag from three sources of data, 80 7-2 Hazard ranking results using the mean concentrations from the risk assessment data sets and EPA soil RSLs increased by a factor of 4, 82 E-1a Compilation of a large number of slag analyses and different eras, 128 E-1b CaO-MgO-SiO2 pseudo-ternary phase diagram depicting liquidus surfaces of system C-M-S-A at 20 percent Al2O3, 129 TABLES 2-1 EAF Annual Steel Production Capacity in North America, 13 2-2 EAF Actual Steel Production in the United States, 13 2-3 Constituents of Slag from Steps in EAF Stainless Steelmaking, 14 2-4a Selected Major Components of EAF Slags, 15 2-4b Selected Minor Components of EAF Slags, 15 2-5 Composition of EAF Slag from a Steel Production Facility in Seattle, WA, 16 2-6 Number of EAF Plants and Slag Processing Facilities by State in the United States, 18 2-7 Estimated Sales Breakdown of Steel Slag by Use, 2021, 20 3-1 Ranges and Averages of Minor and Trace Elements of EAF Slags, 26 3-2 Engineering Measures of Steel Slag, Limestone, and Granite, 34 3-3 Reducing and Oxidizing Elements in Slag of Potential Concern and Their Chemical Speciation in the Environment, 37 3-4 Summary of Selected Standardized Batch Leaching Test Methods Used in Studies for Evaluation of Slag Materials, 41 4-1 Key Exposure Variables in Exposure Assessments of Slag, 51 7-1 Examples of Ranges of Concentrations of Inorganic COPCs in EAF Slag as Reported in Five Risk Assessments, 77 7-2 Sources of Uncertainty in Applying EPA Soil RSLs to Identify and Rank Order COPCs in EAF Slag, 78 7-3 Correlation Matrix (Spearman rho) for Concentrations of Selected Metals in Slag (< 250 µm sieved fraction) from Different Residential Properties in Pueblo, Colorado, 81 

xii Contents 7-4 Key Variables in Assessing Possible Exposures to EAF Slag Chemicals in Soil with Plausible Alternative Values, 83 C-1 EAF Steel Facilities in the United States, 117 D-1 Slag Processing Facilities in the United States, 121 E-1 Slag Minerals Grouped by Chemical Type, 125 F-1 Toxicity Values for Hexavalent Chromium Used in Prior Risk Assessments of EAF Slag, 137 F-2 Toxicity Values for Manganese Used in Prior Risk Assessments of EAF Slag, 138 

Acronyms and Abbreviations ADD average daily dose AI adequate intake AIST Association for Iron & Steel Technology ATSDR Agency for Toxic Substance and Disease Registry BF blast furnace BOF basic oxygen furnace C2S calcium orthosilicate, larnite or belite, 2CaO·SiO2 C3S tricalcium silicate, hatrurite or alite, 3CaO·SiO2 CEN European Committee for Standardization CFTR cystic fibrosis transmembrane conductance regulator COPC chemical of potential concern CS calcium metasilicate, wollastonite, CaO·SiO2 CSH calcium silicate hydrate, near 3CaO·2SiO2·3-4H2O CSM conceptual site model CTE central tendency exposure DRA deterministic risk assessment EAF electric arc furnace EPA U.S. Environmental Protection Agency GI gastrointestinal HBI hot briquetted iron Heat a batch of molten metal and slag made in a furnace HGF home-grown food HI hazard index HOLC Home Owners’ Loan Corporation HQ hazard quotient IARC International Agency for Research on Cancer IOM Institute of Medicine IRIS Integrated Risk Information System LADD lifetime average daily dose LEAF Leaching Environmental Assessment Framework L/S liquid/solid MLE most likely exposure MRI magnetic resonance imaging MRL minimum risk level NHANES National Health and Nutrition Examination Survey NSA National Slag Association xiii 

xiv Acronyms and Abbreviations NTP National Toxicology Program PAH polycyclic aromatic hydrocarbon PBDE polybrominated diphenyl ether PBPK physiologically based pharmacokinetic PCB polychlorinated biphenyl PCDD/F polychlorinated dibenzo-dioxin/furan PEF particulate emission factor PM particulate matter POP persistent organic pollutant PRA probabilistic risk assessment PVC polyvinyl chloride RAGS Risk Assessment Guidance for Superfund RBA relative bioavailability RfC reference concentration RfD reference dose RME reasonable maximum exposure RSL regional screening level SPLP synthetic precipitation leaching procedure TCLP toxicity characteristic leaching procedure TEQ toxic equivalent USGS United States Geological Survey Chemical Symbols Ag silver Al aluminum As arsenic B boron Ba barium Ca calcium Cd cadmium Co cobalt Cr chromium Cu copper Fe iron Hg mercury K potassium Mg magnesium Mn manganese Mo molybdenum Na sodium Nb niobium Ni nickel P phosphorus 

Acronyms and Abbreviations xv Pb lead S sulfur Sb antimony Se selenium Si silicon Sn tin Ti titanium Tl thallium V vanadium W tungsten Y yttrium Zn zinc Chemical Formulas and Ions (aq) aqueous (g) gas (l) liquid (s) solid Al3+ aluminum ion AB2O4 spinel oxide Al2O3 aluminum oxide As3+ arsenic (3+) As3+(OH)3 arsenite Ba2+ barium (2+) BaCO3 barium carbonate BaSO4 barite sulfate CaF2 calcium trifluoride (Ca,Mg)SiO3 calcium-magnesium silicate CaO calcium oxide CaCO3 calcium carbonate Ca(OH)2 calcium hydroxide CaO·SiO2 calcium metasilicate 2CaO·SiO2 calcium orthosilicate 3CaO·SiO2 tricalcium silicate 3CaO·2SiO2·3-4H2O calcium silicate hydrate CaSiO3 calcium silicate CO2 carbon dioxide Cr3+ chromium(III) Cr6+ hexavalent chromium Cr2O3 chromium oxide Cr3+(OH)3(s) chromium(III) hydroxide Fe2+ ferrous ion Fe3+ ferric ion Fe3C iron carbide FeCO3 iron(II) carbonate FeO iron(II) oxide Fe2O3 iron(III) oxide FeCr2O4 chromite 

xvi Acronyms and Abbreviations FeMn ferro manganese FeS iron sulfide (H2As5+O4)–, (HAs5+O4)2– dihydrogen arsenate, monohydrogen arsenate H2O water (Mg,Fe)2SiO4 olivine MgO magnesium oxide Mn2+ manganese (2+) Mn3+ manganese (3+) Mn4+ manganese (IV) cation Mn(CH3COO)2 manganese acetate MnCO3 manganese carbonate MnCl2 manganese chloride MnO manganese oxide MnO2 manganese dioxide Mn3O4 trimanganese tetraoxide MnOOH manganese (III) oxyhydroxide MnPO4 manganese phosphate MnS manganese (II) sulfide MnSiO3 manganese silicate MnSO4 manganese sulfate MnS2 manganese sulfide Na2O sodium oxide P2O5 phosphorus pentoxide –PO43– orthophosphate O2 dioxygen OH– hydroxide Sb3+ antimony (3+) SiO2 silicon dioxide SO3 sulfur trioxide TiO2 titanium dioxide V3+ vanadium (3+) V4+ vanadium (4+) V5+ vanadium (5+) VO2+ vanadyl cation XY(Si,Al)2O6 pyroxenes ZnO zinc oxide