Project Summary (2020-2025)

Environmentally persistent free radicals (EPFRs), while increasingly appreciated for their importance in particulate matter (PM), remain understudied. They are an important contaminant at many Superfund sites and are a unique component of the NIEHS’s portfolio. Nearly 30 percent of Superfund sites employ some type of thermal treatment (TT) and thus produce EPFRs. The Louisiana State University Superfund Research Program (LSU SRP) has repeatedly shown that EPFRs form and persist on PM generated by combustion and TT of chlorinated hydrocarbons and other hazardous substances and are present in contaminated Superfund soils and airborne PM near industrialized Superfund sites. TT remediation processes result in the production of EPFRs that adversely affect respiratory and cardiovascular health of those living near Superfund and hazardous waste TT sites. The Materials Core (MC) is a research service core tasked with providing material and analytical support for the biomedical research (BMR) and environmental science and engineering (ESE) projects. Within the program, researchers have developed model systems that allow for the studies of EPFRs using a bottom-up approach (i.e., starting with simple, EPFR-only samples, proceeding through more complex, multicomponent EPFRs up to actual field-collected EPFRs with variable composition). EPFR generation and characterization, according to requested specification and compositional design, is unique to the MC. Laboratory-made samples, with composition control, are a logical choice for systematic research studies. The MC continues to generate EPFR particle systems containing other transition metals (Fe, Cu, Ni, and Zn, as MexOy) and chlorinated benzenes, phenols, and chlorinated biphenyls because they are present in soils at wood-treating Superfund sites and catalyze pollutant formation (i.e., dioxins). A new particle generation system expands the MC’s studies to complex EPFRs stabilized on iron, the most common transition metal in PM present in many combustion byproducts from TT. This new, two-stage combustion reactor developed in the MC allows for synthesis of complex EPFRs — with combustion-driven composition and controlled EPFR content — which is being supplied to the following projects:

• Activation, Sensing, and Prevention of Formation EPFRs in Thermal Treatment of Superfund Wastes
• Combustion-Generated EPFRs: Assessing Cardiovascular Risks of Exposure
• Environmentally Persistent Free Radicals Alter Pulmonary Immunologic Homeostasis
• Microstructural Pathway of EPFR Formation and Their Decay Mechanisms

Additionally, the MC is assisting the "Hazardous Waste Thermal Treatment and Community Exposure to Environmentally Persistent Free Radicals" project by providing specialized analytical capabilities and/or new techniques and methodologies in relation to particle collection, characterization, and human exposure assessment. This work is also being done in collaboration with the Community Engagement Core (CEC) and the research translation component of the Administrative Core to discuss potential chemical hazards and exposures with communities. Through the "Hazardous Waste Thermal Treatment and Community Exposure to Environmentally Persistent Free Radicals" project and the CEC, the MC is working with communities and stakeholders to identify, quantify, and address environmental health hazards related to the vicinity of Superfund sites and Superfund materials remediation/TT.