Occupational Exposure to Heat and Wildfire Smoke in California Correctional Facilities

Objectives: To assess long term trends in outdoor heat and wildfire smoke exposure at 410 correctional facilities in California from 2000 to 2023. Methods: We used ERA5 Land data to calculate daily wet bulb globe temperature (WBGT) and identified days exceeding the NIOSH exposure limits for heat stress. Wildfire smoke exposure was estimated using the NOAA Hazard Mapping System (HMS). Temporal trends in daily heat and smoke exposure were modeled using linear regression for each facility. Results: Smoke affected days rose statewide from 4.9% (2006 to 2010) to 12.5% (2019 to 2023), with Northern California experiencing the highest burden and steepest increases. Days above 28 degrees Celsius WBGT increased from 27.3% to 29.8% statewide, with the Central Valley and desert regions showing the highest current burden and coastal areas experiencing the steepest increases. Coastal facilities show emerging heat risks, and some regions especially the Central Valley and Sierra foothills face dual exposure to both hazards. Conclusions: Correctional officers and incarcerated workers face rising environmental risks, with regional variation in exposure. Facilities with concurrent heat and smoke burdens must balance cooling and filtration needs. Resilience planning and occupational protections must evolve to meet facility and region-specific challenges.