The Unpredictable Impacts of Extreme Heat on Human Health

As the scorching summer heat shatters records in Arizona, it serves as a stark reminder of the alarming future that awaits our planet during the warmest season. The consequences of extreme heat are not exclusive to Arizona; they have captured global attention. For instance, a tragic incident occurred in Brazil, where a 23-year-old woman died of cardiorespiratory arrest at a Taylor Swift concert due to heat indexes exceeding 120 degrees. Professor Jennifer Vanos, an expert in extreme heat and its health impacts at Arizona State University, sheds light on this critical issue in her recently published paper in Nature Communications titled “A physiological approach for assessing human survivability and liveability to heat in a changing climate.”

Vanos challenges the prevailing notion that a wet-bulb temperature of 35 degrees Celsius (95 degrees Fahrenheit) is the limit for human survivability. This temperature gauge indicates the maximum combination of temperature and humidity that humans can tolerate without inevitably succumbing to heatstroke within a set duration of exposure. However, the simplified nature of this parameter neglects vital variables such as age, activity level, and vulnerability factors. The assumptions behind the current wet-bulb temperature limit, including being indoors or shaded, unclothed, sedentary, and fully heat acclimatized, do not align with the reality of human behavior during the summer season.

Vanos’s paper introduces a more comprehensive model that considers numerous factors, such as humidity, age, activity level, and sun exposure, to determine a range of safe temperatures based on various characteristics. The aim is not only to understand the conditions necessary for survival but also to enable people to live their lives comfortably. If living in a particular area requires individuals to remain completely sedentary, it becomes an undesirable place to reside. Thus, the ability to spend time outdoors without risking overheating is crucial for a fulfilling life, both presently and in the face of future climate change.

Gisel Guzman Echavarria, an ASU student, played a vital role in generating the visuals used in the paper to illustrate the research findings. Combining the expertise of climate scientists and physiologists was instrumental in comprehending the intricate relationship between heat and human health. Professor Ollie Jay, director of the Heat and Health Research Incubator at the University of Sydney, emphasizes that this interdisciplinary approach facilitates a comprehensive understanding of how climate outcomes impact individuals on both physiological and biophysical levels.

Conventionally, the wet-bulb temperature estimate of 35 degrees Celsius has been widely adopted, as seen in reports from the Intergovernmental Panel on Climate Change. However, Vanos and Jay argue that this model underestimates the true impact of heat on humans. By using a more realistic, human-based model, the severity, breadth, and immediacy of these impacts become more apparent. The findings presented in the paper provide a glimpse into a future characterized by a heightened demand for cooling infrastructure, personalized approaches to heat protection, and potential heat-induced migration.

A crucial takeaway from this research is that what might be survivable for a healthy young adult could be experienced dramatically differently by individuals with comorbidities or those taking prescription medications. By acknowledging the significant variability in individuals’ health and vulnerabilities, policymakers can make informed decisions to better protect public health and ensure the well-being of all communities.

The consequences of extreme heat extend far beyond Arizona. Professor Vanos’s groundbreaking research challenges the existing models used to assess human survivability in extreme heat and offers a more comprehensive approach that considers age, activity level, and other crucial factors. The paper emphasizes the need for a realistic understanding of the impacts of extreme heat on human health, particularly as we face the uncertain future of climate change. By embracing these findings, society can work towards implementing measures that prioritize the reduction of heat-related risks and promote the well-being of individuals in an ever-warming world.