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.

Table of Contents

Front Matter Summary 1 Introduction 2 Electric Arc Furnace Steelmaking and Slag Formation, Composition, and Distribution 3 Properties and Environmental Dynamics of Slag 4 Human Exposure to Unencapsulated Electric Arc Furnace Slag 5 Toxicity of Selected Slag Constituents 6 Multiple Stressors in Disadvantaged Communities Where Unencapsulated Slag May Be Used 7 Synthesis of Risk Considerations for Unencapsulated Electric Arc Furnace Slag Uses 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