Resources to inform the 2026 Colorado Climate Preparedness Roadmap: Compound hazards and associated public health implications

Changing environmental conditions are increasing the frequency and severity of extreme weather and environmental hazards, including heat waves, wildfires, drought, reduced water quality, and degraded air quality from ozone (O3) and fine particulate matter pollution (AghaKouchak et al., 2020; Bolinger et al., 2024; Colorado Health Institute, 2023a; Fann et al., 2015; IPCC, 2023a; Nagamoto et al., 2024; Nolte et al., 2018, 2021; Zscheischler et al., 2020). Strong scientific evidence indicates that climate change will increase risks to public health and safety throughout the 21st century, particularly through compound climate events (AghaKouchak et al., 2020; Cascio, 2018; Childs et al., 2022; Ebi, 2025; IPCC, 2023a, 2023b; Ma et al., 2024; Marlier et al., 2026; National Academy of Medicine, 2025; Reid et al., 2016; Reid & Maestas, 2019; Simpson et al., 2023; van den Hurk et al., 2023; Volckens, 2024; Zscheischler et al., 2018, 2020). Compound hazards, which are co-occurring or sequential hazards such as heat waves occurring alongside drought, wildfire, and poor air quality from smoke, can amplify public health risks beyond the effects of individual hazards alone (Marlier et al., 2026; Zscheischler et al., 2020).  

In Colorado, compound climate events with clear implications for public health are already evident (see “Core definitions” section for additional context on compound climate events). Recent statewide assessments have documented increasing heat waves, drought, and wildfires linked to rising temperatures, while emerging data show that climate change is reversing decades of air quality improvements through increased O3 and fine particulate matter pollution due to wildfire, and increased aerosolized topsoil (i.e., dust) due to drought (Bolinger et al., 2024; Childs et al., 2022; Fann et al., 2015; Ghanbari et al., 2023; Larsen et al., 2022; Nolte et al., 2018, 2021; Volckens, 2024). These environmental shifts are associated with increases in eye and kidney-health related concerns, heat-related illness, exacerbations of asthma and other respiratory conditions, increased risk of infectious disease, cardiovascular stress, and mental health impacts, with disparities in risk for children, older adults, outdoor workers, and communities with existing health and economic vulnerabilities (Baraghoshi et al., 2023; Butler-Dawson et al., 2026; Cascio, 2018; Cleland et al., 2022; Colorado Health Institute, 2023a; Grover et al., 2024; Lee et al., 2023; Ma et al., 2024; Macaluso et al., 2024; Marlier et al., 2026; National Academy of Medicine, 2025; Patnaik et al., 2024; Peters et al., 2019; Reid et al., 2016; Reid & Maestas, 2019).  

The state is actively pursuing strategies to mitigate the risks of these compound climate events on the public, including expanding climate and health surveillance, strengthening early-warning systems and public communication around smoke and air quality, and developing integrated policy agendas that link climate mitigation, adaptation, and health equity (CDPHE, 2025; Colorado Health Institute, 2023b; Zemaitis & Bailey, 2024). For example, state and partner organizations have articulated cross-sector goals to prepare for health impacts related to extreme heat, wildfires, flooding, drought, declines in water quality, and poor air quality, including updating workplace safety protocols, enhancing community-based resilience, adapting clinical care assessments to include climate-related stressors, and improving access to mental and behavioral health services following climate-related disasters (Colorado Health Institute, 2023b; CDPHE, 2025; Zemaitis & Bailey, 2024). To better prepare for current risks and make informed decisions, more information is needed, including methods to analyze historical and projected conditions in near real time, characterize interactions among compound hazards, and translate climate and air quality science into actionable guidance for public health agencies, health care systems, and communities across Colorado (Ebi, 2025; Marlier et al., 2026; National Academy of Medicine, 2025; Simpson et al., 2023; Zscheischler et al., 2018). 

For this report, we focus on extreme heat and outdoor air quality (ozone [O3] and fine particulate matter [PM2.5]) as the main compound hazards causing compound climate events, given that 1) the state of Colorado has experienced poor air quality for some time, 2) these climate events are affecting large population numbers, and 3) there is capacity to consider and respond to these climate-driven events.