Heat, Disparities, and Health Outcomes in San Diego County's Diverse Climate Zones

Abstract

Climate variability and change are issues of growing public health importance. Numerous studies have documented risks of extreme heat on human health in different locations around the world. Strategies to prevent heat‐related morbidity and reduce disparities are possible but require improved knowledge of health outcomes during hot days at a small‐scale level as important within‐city variability in local weather conditions, socio‐demographic composition, and access to air conditioning (AC) may exist. We analyzed hospitalization data for three unique climate regions of San Diego County alongside temperature data spanning 14 years to quantify the health impact of ambient air temperature at varying exceedance threshold levels. Within San Diego, coastal residents were more sensitive to heat than inland residents. At the coast, we detected a health impact at lower temperatures compared to inland locations for multiple disease categories including heat illness, dehydration, acute renal failure, and respiratory disease. Within the milder coastal region where access to AC is not prevalent, heat‐related morbidity was higher in the subset of zip codes where AC saturation is lowest. We detected a 14.6% increase (95% confidence interval [4.5%, 24.6%]) in hospitalizations during hot weather in comparison to colder days in coastal locations where AC is less common, while no significant impact was observed in areas with higher AC saturation. Disparities in AC ownership were associated with income, race/ethnicity, and homeownership. Given that heat waves are expected to increase with climate change, understanding health impacts of heat and the role of acclimation is critical for improving outcomes in the future.

Risk screening methods for extreme heat: Implications for equity-oriented adaptation

“…Previous work has questioned the efficacy of a 105°F heat index threshold for the state of California [ 16 , 25 ]. Given that health impacts have been shown to emerge at temperatures as low as 73°F for the coastal region of San Diego County, we used the lower bound of the heat index “extreme caution” classification, 91°F, as a mid-range, health-relevant definition for the state [ 25 ]. In contrast to the relative heat events, a single temperature threshold was used for the entire state rather than thresholds derived from local historical data.…”

“…Currently the National Weather Service alerts the public of a heat hazard when the heat index is greater than 105℉ for a minimum of two consecutive days [ 24 ]. The heat index is a measurement of the apparent temperature one would feel in the shade given the amplifying effects of humidity; it is an absolute metric that does not consider relative climatology and does not capture the fact that health impacts from different doses of heat vary among communities [ 2 , 4 , 16 , 25 ]. The heat index is not to be confused with a vulnerability index, which is a metric that integrates indicators of vulnerability.…”

“…To address the shortcomings of the heat index, many studies also measure extreme heat using a heat wave definition that spans multiple days and uses a relative, locally defined temperature threshold. However, many heat index and heat wave definitions employ extreme heat thresholds above temperatures where heat-related health impacts begin, potentially missing harmful events [ 16 , 25 , 26 ]. This study therefore includes metrics that measure absolute and relative extreme heat at thresholds shown to be relevant to heat-health risk.…”

Evaluation of Air Condition Use and Its Health Effects

“…Climate variability and change are issues of growing public health importance [1]. The increase in heat exposure level as a result of global climate change in urban areas is a health and productivity risk for millions of people.…”

“…Inhabitants in the tropical and subtropical urban areas are at higher risk due to high population density [2][3][4][5][6]. Heat is the top weather-related killer in the United States [1]. In California, the July 2006 heat wave, which was of an unprecedented magnitude and humidity was responsible for over 600 excess deaths [7] and over 1200 hospitalizations for cardiovascular and other diseases [8].…”