Climate Policy and Public Health: What Research Shows About Heat, Air, and Human Wellbeing

The intersection of climate policy and public health has received dramatically more research attention over the past decade as evidence has accumulated that climate change is not a distant threat to future generations but a present and worsening crisis that is already affecting health outcomes. Research on the health effects of heat, air pollution, extreme weather events, and climate-related ecosystem changes has produced findings that reframe climate action as a public health imperative as much as an environmental one. Heat is the deadliest form of extreme weather and is becoming more frequent, more intense, and longer-lasting as global temperatures rise. Research on heat and mortality finds that heat-related deaths are substantially undercounted in official statistics, which attribute deaths to heat only when there is direct evidence of hyperthermia rather than recognizing the contribution of heat to deaths from cardiovascular disease, kidney failure, and respiratory conditions. Studies using excess mortality methods, which compare observed deaths during heat events to expected deaths based on historical patterns, find that heat events kill far more people than official heat mortality statistics suggest. Vulnerable populations bear the greatest health burden from extreme heat. Older adults, who have diminished physiological capacity to regulate body temperature, account for the majority of heat deaths. People who work outdoors, including agricultural workers, construction workers, and landscapers, face intense occupational heat exposure. People without air conditioning, who disproportionately live in low-income urban neighborhoods, are exposed to indoor temperatures that can be lethal during heat waves. Research on urban heat islands, the phenomenon by which built environments retain more heat than surrounding areas, finds that urban neighborhoods with less tree canopy cover, more impervious surfaces, and lower income levels experience significantly higher temperatures during heat events. Air pollution is a documented major cause of premature death, disability, and chronic disease. Research consistently finds associations between particulate matter and ozone exposure and increased risk of cardiovascular disease, lung cancer, chronic obstructive pulmonary disease, stroke, and adverse pregnancy outcomes. Climate change affects air quality through multiple pathways: wildfires produce smoke and particulate matter over larger areas, rising temperatures increase ground-level ozone formation, and extended growing seasons increase pollen production and duration. Research on air quality trends finds that the health benefits produced by decades of Clean Air Act enforcement are being partially offset by climate-related air quality deterioration. Wildfire smoke has emerged as a significant and growing public health concern. Research on wildfire smoke exposure finds associations with respiratory and cardiovascular emergency department visits and hospitalizations, and more recent research has identified associations with adverse birth outcomes and cognitive effects in children. The geographic reach of wildfire smoke, which during major fire events can affect air quality across entire regions and even continents, means that the affected population is far larger than those living near fire-prone areas. Extreme weather events, including hurricanes, floods, droughts, and ice storms, cause direct mortality and injury but also have documented mental health effects that can persist for years after the event. Research on post-disaster mental health finds elevated rates of PTSD, depression, anxiety, and substance use disorders in affected populations, with effects that are more severe and persistent in communities with fewer resources for recovery. Climate-related disasters disproportionately affect low-income communities and communities of color, which have less political and economic power to advocate for protective infrastructure and receive adequate disaster recovery resources. Infectious disease patterns are being affected by climate change through multiple mechanisms. Range expansion of vectors including mosquitoes and ticks, driven by warming temperatures and shifting precipitation patterns, is bringing diseases including dengue, West Nile virus, and Lyme disease to regions where they were previously uncommon. Research on climate and disease vector distribution is increasingly sophisticated, using climate models and vector surveillance data to project future disease burdens under different warming scenarios. The health benefits of climate mitigation are a compelling argument for policy action. Research using health impact modeling finds that air quality improvements resulting from reduced fossil fuel combustion would prevent hundreds of thousands of premature deaths annually in the United States and millions globally. These immediate and local health benefits, realized independently of the longer-term climate stabilization benefits, can exceed the economic costs of carbon pricing and renewable energy transition under many modeling assumptions. Framing climate policy in terms of near-term, local health benefits may be more persuasive to some audiences than framing it in terms of global or long-term warming scenarios. Health equity is a dimension of climate policy that research has increasingly highlighted. The communities that contribute the least to greenhouse gas emissions tend to bear the greatest health burdens from climate change effects. Fossil fuel facilities are disproportionately located in low-income communities and communities of color, producing concentrated local pollution alongside climate-relevant emissions. Climate policy that reduces fossil fuel use improves health equity as well as environmental outcomes, while climate change that continues unabated worsens health disparities. The public health research community has become increasingly vocal about climate change as a health emergency, with major public health organizations issuing statements calling for aggressive mitigation and adaptation action. This alignment between climate science and public health science provides a basis for policy action that draws on multiple evidence streams and that connects climate action to health values that command broad public support.