APEX: A Web-Based Tool for Assessing Long-Term Outdoor PM_2.5 Exposure-Brief Report

Long-term exposure to ambient fine particulate matter air pollution (PM_2.5) is a major risk factor for lung cancer and other chronic diseases. However, assigning individualized long-term exposure estimates, both at the point of care and in epidemiologic research, remains a methodological challenge due to limited tools for integrating residential history with air pollution data. As a result, most studies estimate exposure based only on a participant's last recorded address. Here, we describe and demonstrate the use of the Air Pollution EXposure (APEX) tool, a web-based application that provides individual annual estimates for PM_2.5 exposure from 1998 to 2024 based on a user-provided residential history. APEX can collect address histories through a user-friendly web interface to collect worldwide addresses with autocompletion and interactive map facilitating recall of partial addresses. Addresses are geocoded and linked to annual surface-level PM_2.5 estimates. APEX also supports both single-entry and batch-processing entry modes for integration in clinical and research workflows. APEX outputs annual PM_2.5 exposure values, geocoded address logs, and graphical summaries. APEX-derived exposure estimates have been used to support an epidemiologic analysis evaluating the association between PM_2.5 and lung cancer risk. APEX enables scalable, reproducible, and clinically applicable PM_2.5 exposure assessment, facilitating personalized evaluation for risk assessment and epidemiologic research for lung cancer, cardiovascular disease, and other conditions associated with air pollution.