Identifying the Relationships between Mortality and Heat Stress Indices across North Carolina

Exposure to extreme heat is the most common cause of weather-related fatalities in the United States. The National Weather Service employs the heat index to estimate environmental heat exposure, and many epidemiological studies use air temperature. Wet bulb globe temperature (WBGT) is increasingly utilized in occupational health and athletic safety to assess heat stress, as it incorporates not only air temperature and humidity, but also the effects of wind speed and radiation. There is, however, a notable lack of population-level research on the use of WBGT as a measure of heat stress. In this study, we identify relationships between these three measures of heat stress and mortality in North Carolina from 2005 to 2015. These relationships are compared across climatically and demographically diverse regions of the state. Notable differences are identified in the character of the relationships across these regions, with the relationships between mortality and WBGT being strongest in rural regions. To inform future heat-health safety protocols across the state, our study also identified temperature thresholds above which mortality becomes exponentially more likely for each of the three measures of heat stress investigated.