The predominant way of making steel in the United Sates is by using an electric arc furnace (EAF) to melt scrap steel, which results in the formation of a rock-like material called slag. Among its various applications, EAF slag is used in a loose or unencapsulated form as ground cover material for residential landscaping. However, the slag generated from the EAF process can contain toxic metals, which can be hazardous to human and environmental health. This report, conducted at the request of the U.S. EPA, discusses the relative hazard of key EAF slag constituents, the extent to which they may be released into the environment, and important aspects in assessing human exposures and risk. Due to uncertainties in the current evidence stream, the report was unable to make an overall characterization of risk related to unencapsulated EAF slag use in the United States and cautions against making generalizations from conclusions in published risk assessments. The report also identifies research needs to better understand factors considered to have the potential to contribute to the highest risks from the use of unencapsulated EAF slag, such as human exposure to dust particles that may be released over time from applied slag.

Contents

• The National Academies of SCIENCES • ENGINEERING • MEDICINE
• COMMITTEE ON ELECTRIC ARC FURNACE SLAG: UNDERSTANDING HUMAN HEALTH RISKS FROM UNENCAPSULATED USES
• BOARD ON ENVIRONMENTAL STUDIES AND TOXICOLOGY
• Reviewers
• Acronyms and Abbreviations
• Summary
  • CHEMICAL PROPERTIES OF SLAG
  • HUMAN EXPOSURE TO SLAG CONSTITUENTS
  • RISK FACTORS AND DATA NEEDS
  • PRIORITY RESEARCH NEEDS
• 1. Introduction
  • STEELMAKING AND ELECTRIC ARC FURNACE SLAG
  • STUDY BACKGROUND
  • COMMITTEE'S STATEMENT OF TASK AND APPROACH
  • ORGANIZATION OF THE REPORT
• 2. Electric Arc Furnace Steelmaking and Slag Formation, Composition, and Distribution
  • STEEL PRODUCTION AND SLAG FORMATION IN AN ELECTRIC ARC FURNACE
  • SLAG COMPOSITION
  • SLAG PROCESSING, DISTRIBUTION, AND USE
  • GEOGRAPHIC DISTRIBUTION OF ELECTRIC ARC FURNACE FACILITIES AND SLAG PROCESSORS
  • STATE GOVERNMENT OVERSIGHT OF SLAG USE
  • SUMMARY
• 3. Properties and Environmental Dynamics of Slag
  • MINERALOGY AND MINERALOGICAL PHASES OF SLAG SOLIDIFICATION
  • TRACE CONSTITUENTS IN SLAG
  • 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
  • SUMMARY
• 4. Human Exposure to Unencapsulated Electric Arc Furnace Slag
  • CONCEPTUAL SITE MODEL
  • AVERAGE DAILY DOSE EQUATIONS
  • BIOACCESSIBILITY AND BIOAVAILABILITY
  • KEY EXPOSURE VARIABLES FOR FURTHER EVALUATION
  • SUMMARY
• 5. Toxicity of Selected Slag Constituents
  • CHROMIUM
  • MANGANESE
  • SUMMARY
• 6. Multiple Stressors in Disadvantaged Communities Where Unencapsulated Slag May Be Used
  • CUMULATIVE EXPOSURES
  • SOCIETAL INEQUITIES AND CUMULATIVE EXPOSURES
  • DEMOGRAPHIC CONSIDERATIONS
  • SUMMARY
• 7. Synthesis 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
  • RISK FACTORS AND DATA NEEDS
  • PRIORITY RESEARCH NEEDS
• References
• Appendix A. Committee Member Biographies
• Appendix B. Open Session Agendas
• Appendix C. EAF Steel Facilities
• Appendix D. Slag Processing Facilities
• Appendix E. Slag Mineralogy
• Appendix F. Review of Past Risk Assessments of Electric Arc Furnace Slag

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.

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.

Printed in the United States of America.