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
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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
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
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.
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Contents
Steelmaking and Electric Arc Furnace Slag
Committee’s Statement of Task and Approach
2ELECTRIC ARC FURNACE STEELMAKING AND SLAG FORMATION, COMPOSITION, AND DISTRIBUTION
Steel Production and Slag Formation in an Electric Arc Furnace
Slag Processing, Distribution, and Use
Geographic Distribution of Electric Arc Furnace Facilities and Slag Processors
State Government Oversight of Slag Use
3PROPERTIES AND ENVIRONMENTAL DYNAMICS OF SLAG
Mineralogy and Mineralogical Phases of Slag Solidification
Organic Pollutants from Plastic Materials Mixed with Scrap Steel
Weathering and Mechanical Degradation of Slag
Environmental Weathering of Slag
Mechanical Degradation of Slag
Release and Environmental Transport of Trace Slag Constituents
Leaching and Mobilization of Trace Elements by Water
4HUMAN EXPOSURE TO UNENCAPSULATED ELECTRIC ARC FURNACE SLAG
Bioaccessibility and Bioavailability
Key Exposure Variables for Further Evaluation
5TOXICITY OF SELECTED SLAG CONSTITUENTS
6MULTIPLE STRESSORS IN DISADVANTAGED COMMUNITIES WHERE UNENCAPSULATED SLAG MAY BE USED
Societal Inequities and Cumulative Exposures
7SYNTHESIS OF RISK CONSIDERATIONS FOR UNENCAPSULATED ELECTRIC ARC FURNACE SLAG USES
Previous Risk Assessments on Electric Arc Furnace Slag
Hazard Ranking of Constituents in Electric Arc Furnace Slag
FREVIEW OF PAST RISK ASSESSMENTS OF ELECTRIC ARC FURNACE SLAG
BOXES, FIGURES, AND TABLES
BOXES
S-1 Key Risk Factors and Data Needs
3-1 Potential Hazard of Slag Mineral Components: Examples
7-1 Key Risk Factors and Data Needs
FIGURES
2-2 Distribution of EAF steelmaking facilities and slag processing facilities in the United States
3-1 Gravel-size steel slag particle with a lime pocket
3-2a Concentrations of chromium (Cr) and manganese (Mn) in ferrous slags
3-2b Concentrations of arsenic (As) and lead (Pb) in ferrous slags
3-2c Concentrations of vanadium (V) and molybdenum (Mo) in ferrous slags
3-3 Comparison of the concentrations measured at an air sampling site
4-2 Conceptual framework for definitions of bioaccessibility and bioavailability
6-2 Percent non-White by census block group in Pueblo County, Colorado
6-4 Multiple stressors relative to redlining in Pueblo, Colorado
7-1 Constituent profiles for EAF slag from three sources of data
E-1a Compilation of a large number of slag analyses and different eras
TABLES
2-1 EAF Annual Steel Production Capacity in North America
2-2 EAF Actual Steel Production in the United States
2-3 Constituents of Slag from Steps in EAF Stainless Steelmaking
2-4a Selected Major Components of EAF Slags
2-4b Selected Minor Components of EAF Slags
2-5 Composition of EAF Slag from a Steel Production Facility in Seattle, WA
2-6 Number of EAF Plants and Slag Processing Facilities by State in the United States
2-7 Estimated Sales Breakdown of Steel Slag by Use, 2021
3-1 Ranges and Averages of Minor and Trace Elements of EAF Slags
3-2 Engineering Measures of Steel Slag, Limestone, and Granite
4-1 Key Exposure Variables in Exposure Assessments of Slag
7-2 Sources of Uncertainty in Applying EPA Soil RSLs to Identify and Rank Order COPCs in EAF Slag
C-1 EAF Steel Facilities in the United States
D-1 Slag Processing Facilities in the United States
E-1 Slag Minerals Grouped by Chemical Type
F-1 Toxicity Values for Hexavalent Chromium Used in Prior Risk Assessments of EAF Slag
F-2 Toxicity Values for Manganese Used in Prior Risk Assessments of EAF Slag
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 |
| 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 |
| 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 |
| 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 |
