UC Irvine

Given the increasing size, frequency, and severity of wildfires in California, there is a growing need to understand their health impacts, particularly on understudied outcomes. Among the various components of wildfire smoke, fine particulate matter (PM2.5) poses the greatest concern for public health. However, existing studies on wildfire PM2.5 are limited and often rely on crude exposure assessment. Moreover, there is a significant health equity issue in disadvantaged communities with lower socioeconomic status, where minority populations are disproportionately burdened by wildfire smoke exposure. Understanding the specific vulnerabilities and communication needs of these populations is essential for targeted intervention.This work examined the associations of wildfire PM2.5 exposure with pregnancy and mental health outcomes based on exposure data with fine spatiotemporal resolution to address current research gaps. Furthermore, a community-based survey was conducted in Eastern Coachella Valley (ECV), California, to understand factors influencing wildfire risk perception and preferred risk communication strategies among socioeconomically disadvantaged populations. The first chapter examined the relationship between wildfire PM2.5 and pregnancy outcomes, including preterm birth (PTB) and preterm premature rupture of membranes (PPROM), based on birth certificate data from 2017 to 2020 in California. Hourly concentrations of wildfire PM2.5 at a 1 km × 1 km resolution were derived from a two-stage machine learning model integrating the Community Multiscale Air Quality model outputs with other spatiotemporal information. Maternal exposure to wildfire PM2.5 during the entire pregnancy and the first two trimesters was significantly associated with PTB and PPROM. The associations were higher among individuals who were Asian or Black, underweight, started their pregnancies in the warm season, had female infants, or were exposed to higher levels of non-wildfire air pollution. In addition, approximately 6.90% of PTB cases can be attributed to higher exposure to wildfire PM2.5 during pregnancy. The second chapter quantified the exposure-response relationship between wildfire PM2.5 and depression-related medical encounters. The individual-level electronic health records were obtained from the University of California, Los Angeles, Health System from 2017 to 2020. Daily average and maximum concentrations of wildfire PM2.5 were obtained and further aggregated at the level of zip code tabulation areas. Based on a time-stratified case-crossover design, daily average and maximum wildfire PM2.5 concentrations were significantly associated with all-type medical encounters and emergency room visits related to depression during wildfire periods. Significantly higher associations were observed in the cold season and among individuals living in areas with higher background air pollution levels. In the third chapter, an in-person survey was conducted among 115 participants in four unincorporated communities in ECV from February to April 2023. Higher safety awareness, more participation in community or social groups, and poorer health were associated with increased wildfire risk perception. Short messages were preferred for wildfire alerts, and television was the most favored information channel. Social media was the most preferred channel among young adults. Elderly individuals and those lacking a high school education were more likely to seek information from doctors than other groups. Agricultural workers relied more on mobile phone texts and personal observations than those in other occupations. By examining both pregnancy and mental health outcomes, this study offers new insights into the adverse health effects associated with wildfire PM2.5 exposure. It also identifies critical gaps in wildfire preparedness and risk communication in disadvantaged communities, highlighting the need to leverage social networks and implement tailored communication strategies to enhance the resilience of socially vulnerable populations.