Wildfire smoke, heat and cardiovascular risk across the life course - Environmental exposures related to weather, including heat and wildfire smoke, have been related to multiple facets of health and child development. The impacts of these exposures over the life course on cardiovascular health remain largely unknown. Growing evidence indicates that exposure to heat stress and wildfire smoke may lead to adverse cardiovascular health outcomes and mortality in adults. Yet little is known about how such exposures may influence the development of cardiovascular risk factors in younger populations, when prevention strategies may have the greatest long-term health impact. Little to no research has focused on heat stress and wildfire smoke exposures over the critical transition from adolescence to early adulthood, during which adverse patterns of cardiovascular health may be established and preventative strategies may be most effective in reducing chronic disease risk over the life course. Further, such environmental exposures often co-occur, and evidence suggests that their combined impacts may heighten their individual effects, thus considering their independent and joint effects is important to fully capture their likely impacts. Lastly, evaluating the impact of personal lifestyle and neighborhood-level factors at buffering those health risks may inform intervention opportunities. In this proposal, we will investigate whether greater individual and joint exposures to heat stress and wildfire smoke over the life course are associated with cardiovascular health profiles in the MetaAir2 study, a cohort of 400 young adults. repeated carotid artery ultrasounds in childhood and early adulthood, and comprehensive evaluation of measures of cardiovascular risk (blood lipids, HbA1c, blood pressure, body composition) in young adults, we will investigate how exposure to heat stress, wildfire smoke, or their joint mixture from childhood to early adulthood may impact multiple measures of cardiovascular health and preclinical risk factors for disease. We will employ novel statistical methods to evaluate the overall combined role of personal lifestyle factors (e.g. diet, sleep health, physical activity) and neighborhood level factors (e.g. greenness, walkability) at modifying these effects, and then employ a causal inference framework to estimate the isolated, direct causal effects of modifiable factors. This work will inform targeted interventions to reduce cardiovascular health impacts of environmental exposures and protect long-term health over the life course.