Purpose: To reduce exposures and cancer risks in wildland firefighters. Specific aims: 1) Expand participation across geographic areas and select exposure-reduction interventions; 2) Conduct exposure monitoring using silicone wristbands and urine; and 3) Test the effectiveness of interventions to reduce exposure and cancer risks. Relevance: Wildland firefighters are exposed to multiple carcinogens including but not limited to polycyclic aromatic hydrocarbons (PAHs), formaldehyde and benzene from combustion of vegetation, structures and vehicles. Additional information is needed on the extent of task-specific wildland and wildland-urban interface (WUI) exposures across multiple states. Silicone wristbands provide additional exposure information beyond that available through urine monitoring and have not previously been used in wildland or WUI fires. Furthermore, there is a lack of information on the effectiveness of wildland and WUI fire exposure reduction interventions selected by the fire service. Methods: Building on the existing Fire Fighter Cancer Cohort Study (FFCCS) wildland firefighter study, we will enroll an additional 300 career and volunteer wildland firefighters within and beyond the current locations in California, Colorado and Wyoming. Surveys for self-reported cancer risk and occupational exposures and blood and urine will be collected at enrollment for all new study participants, and again after 12-18 months for all ~600 total study participants. Our fire department study partners will select interventions to test during prescribed burns and campaign fires, informed by data sharing within an international research collaborative. Silicone wristbands and urine samples will be collected before and after fire exposures selected by the partner fire departments, measuring for semivolatile chemicals and urinary PAH metabolites to quantify exposures. Concurrently, the partner fire departments will test the effectiveness of the selected interventions to reduce carcinogenic exposures. Anticipated outcomes: We will identify high-exposure job tasks across geographic regions specific to wildland and WUI fires and effective exposure reduction interventions.