Project Summary/Abstract: Materials Core 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 National Institute of Environmental Health Sciences’ portfolio. Nearly 30% of Superfund sites employ some type of thermal treatment (TT) and thus produce EPFRs. We have 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 our program we have developed such 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. We will continue 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 our studies to complex EPFRs stabilized on iron, the most common transition metal in PM present in many combustion by-products 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 will be supplied to Projects 1, 2, 4 and 5. Additionally, the MC will assist Project 3 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 the communities. Through Project 3 and the CEC, the MC will work with communities and stakeholders to identify, quantify, and address environmental health hazards related to the vicinity of Superfund sites and Superfund materials remediation/TT.