EXPOSURE FACTORS FACILITY CORE: PROJECT SUMMARY/ABSTRACT The Exposure Factors Core (EFC) provides technical support to Southern California Environmental Health Sciences Center (SCEHSC) investigators and pilot project awardees to advance environmental health science research. Led by a complementary pair of environmental and spatial science investigators and in close collaboration with the SCEHSC Exposure Sciences and Biostatistics & Data Science Methods Research Programs, the EFC combines exposure assessment expertise from a wide array of disciplines necessary to fully characterize and understand exposures for population-based research. Services include advice on environmental sampling design; instrument selection and deployment; field operations and logistics; sampling protocols; social and built environment data resources; spatiotemporal modeling; remote satellite imagery; machine learning approaches to data analysis; ecological momentary assessment of real-time exposures and geographic and psychosocial contexts; assessment of ultraviolet radiation exposure; and a robust assortment of geospatial analysis platforms. There is a well-defined access and chargeback mechanism for EFC services. Equipment, consultation, and training are all available across a number of EFC subspecialties. The EFC works closely with the other SCEHSC Facility Cores to provide guidance on exposure assessment strategies and approaches for SCEHSC pilot projects, NIEHS and other funded research, and with the Community Engagement Core to support community partnerships. Effective and efficient methodologies are applied to challenging research questions. Rigor and reproducibility guide recommendations on exposure study design, instrument selection, data collection and quality control, and on analysis and modeling of exposure data. The EFC supports the SCEHSC mission by providing guidance on the latest methodologies, equipment, and exposure assessment approaches for investigators’ use.