Grant: CIHR Fellowship

Current predictions of human survivability due to heat stress with climate change rely on an oversimplified model of how the human body thermoregulates, especially under conditions with different humidity levels. It is likely that our ability to cope with extreme heat is limited to more modest levels of global warming than previously forecasted with this simplistic model, and thus the heat-health impacts of future climate change are underestimated. My project is designed to: (1) evaluate the conditions under which true human physiological heat strain deviates from the existing model created by climate scientists; and (2) determine the potential modifying effects of biological sex, age, and prescription drug use on the same outcomes. Participants will include children, younger healthy adults, older healthy adults, and older adults on beta-blockers, a commonly prescribed drug for high blood pressure. Under careful medical supervision, participants will be exposed to four different 3-hour exposures to environmental conditions that are equivalent to the theoretical wet-bulb temperature threshold for survival of 35°C, but with different humidity levels: (i) very humid, (ii) humid, (iii) dry, (iv) and very dry. Physiological heat strain will be comprehensively assessed during each condition using measures of core temperature, heart rate, blood pressure and whole-body sweat loss. The proposed project will lead to the development of a new model for predicting future heat-health impacts with different climate change scenarios following various future carbon emission pathways. This information will be essential for policymakers to understand the future impacts of different present-day regional and global climate mitigation policies and actions and the impacts on human health.