Extreme Heat Exposure Research Articles

Linking climate change to urban planning through vulnerability assessment: The case of two cities at the Mexico-US border

There is increasing evidence that climate change impacts have been particularly critical in the case of heat waves during the last years. Many cities around the globe have been affected by heat waves and their cascading effects, threatening public health and urban life and disrupting services and infrastructure. Unfortunately, cities in developing countries are not paying attention to heatwaves' impacts. This is the case in Mexico. Although there are studies on extreme heat exposure, there are no vulnerability assessments. The central research question of our study is the analysis of social vulnerability to extreme temperature and heatwaves in two Mexican cities at the U.S.- Mexico border, Tijuana, and Mexicali. Our results show that urban planning and state and municipal development policies in both cities have neglected the impact of heat waves despite their increasing frequency, intensity, and duration in the last two decades. The results also show significant differences in exposure, sensitivity, and adaptive capacity to extreme temperatures within each city. Areas with higher vulnerability in both cities are informal settlements and low-income neighborhoods. This information can support local governments in making sound use of scarce resources to create efficient responses to current impacts and future risks of climate change.

The effects of heatwave on cognitive impairment among older adults: Exploring the combined effects of air pollution and green space

The association between heatwaves and cognitive impairment in older adults, especially the joint effect of air pollution and green space on this association, remains unknown. The present cohort study used data from waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) from 2008 to 2018. Heatwaves were defined as having daily maximum temperature ≥ 92.5th, 95th and 97.5th percentile that continued at least two, three and four days, measured as the one-year heatwave days prior to the participants' incident cognitive impairment. Data on the annual average air pollutant concentrations of fine particulate matter (PM2.5) and ozone (O3) as well as green space exposure (according to the Normalized Difference Vegetation Index (NDVI)) were collected. Time-varying Cox proportional hazards models were constructed to examine the independent effect of heatwaves on cognitive impairment and the combined effect of heatwaves, air pollution, and green space on cognitive impairment. Potential multiplicative interactions were examined by adding a product term of air pollutants and NDVI with heatwaves in the models. The relative excess risk due to interaction (RERI) was calculated to reflect additive interactions. We found that heatwave exposure was associated with higher risks of cognitive impairment, with hazard ratios (HRs) and 95 % confidence intervals (CIs) ranging from 1.035 (95 % CI: 1.016–1.055) to 1.058 (95 % CI: 1.040–1.075). We observed a positive interaction of PM2.5 concentrations, O3 concentrations, lack of green space, and heatwave exposure on a multiplicative scale (HRs for product terms >1). Furthermore, we found a synergistic interaction of PM2.5 concentrations, O3, lack of green space, and heatwave exposure on an additive scale, with RERIs >0. These results suggest that extreme heat exposure may be a potential risk factor for cognitive impairment in older adults. Additionally, coexposure to air pollution and lack of green space exacerbated the adverse effects of heatwaves on cognitive function.

Spatio-temporal interpolation and delineation of extreme heat events in California between 2017 and 2021

Robust spatio-temporal delineation of extreme climate events and accurate identification of areas that are impacted by an event is a prerequisite for identifying population-level and health-related risks. In prior research, attributes such as temperature and humidity have often been linearly assigned to the population of the study unit from the closest weather station. This could result in inaccurate event delineation and biased assessment of extreme heat exposure. We have developed a spatio-temporal model to dynamically delineate boundaries for Extreme Heat Events (EHE) across space and over time, using a relative measure of Apparent Temperature (AT). Our surface interpolation approach offers a higher spatio-temporal resolution compared to the standard nearest-station (NS) assignment method. We show that the proposed approach can provide at least 80.8 percent improvement in identification of areas and populations impacted by EHEs. This improvement in average adjusts the misclassification of about one million Californians per day of an extreme event, who would be either unidentified or misidentified under EHEs between 2017 and 2021.

Exploring the impact of temporal heat stress on skeletal muscle hypertrophy in bovine myocytes

The primary aim of this investigation was to explore the impact of different temporal stress conditions on the regulators associated with skeletal muscle hypertrophy in bovine myocytes. Bovine satellite cells (BSCs) were extracted from three-month-old Holstein bull calves and subjected to myogenic differentiation under three thermal treatments: 38 °C (control; CON), 39.5 °C (moderate heat stress; MHS), and 41 °C (extreme heat stress; EHS) for a duration of 3 or 48 h. Exposure to EHS resulted in elevated (P < 0.01) expression levels of heat shock protein (HSP)20, HSP27, HSP70, and HSP90, along with increased (P < 0.01) protein levels. Moreover, cells exposed to MHS and EHS exhibited enhanced (P < 0.01) gene expression of myoblast determination protein 1 (MyoD), while myogenin (MyoG) was overexpressed (P < 0.01) in cells exposed to EHS. These findings suggest that heat exposure can potentially induce myogenic differentiation through the modulation of myogenic regulatory factors. Furthermore, our investigations revealed that exposure to EHS upregulated (P < 0.01) myosin heavy chain (MHC) I expression, whereas MHC IIA (P < 0.01) and IIX (P < 0.01) expression were increased; P < 0.01) under MHS conditions. These observations suggest that the temperature of the muscle may alter the proportion of muscle fiber types. Additionally, our data indicated that EHS activated (P < 0.01) the expression of insulin-like growth factor 1 (IGF-1) and triggered the activation of the Akt/mTOR/S6KB1 pathway, a known anabolic pathway associated with cellular protein synthesis. Consequently, these altered signaling pathways contributed to enhanced protein synthesis and increased myotube size. Overall, the results obtained from our current study revealed that extreme heat exposure (41 °C) may promote skeletal muscle hypertrophy by regulating myogenic regulatory factors and IGF-1-mediated mTOR pathway in bovine myocytes.

Cumulative exposure to extreme heat and trajectories of cognitive decline among older adults in the USA

BackgroundThe projected increase in extreme heat days is a growing public health concern. While exposure to extreme heat has been shown to negatively affect mortality and physical health, very little...

Aging Increases Enterocyte Damage during a 3-Hour Exposure to Very Hot and Dry Heat: A Preliminary Study.

Profound heat stress can damage the gastrointestinal barrier, leading to microbial translocation from the gut and subsequent systemic inflammation. Despite the greater vulnerability of older people to heat wave-related morbidity and mortality, it is unknown if age modulates gastrointestinal barrier damage and inflammation during heat stress. Therefore, the aim of this study was to determine if aging impacted enterocyte damage and systemic inflammatory responses to a 3-h exposure to very hot and dry (47 °C, 15% humidity) heat with accompanying activities of daily living (intermittent activity at 3 METS). Data from 16 young (age 21 to 39 years) and 16 older (age 65 to 76 years) humans were used to address this aim. In each group, log-transformed plasma concentrations of intestinal fatty acid binding protein (I-FABPlog), interleukin-8 (IL-8log), and tissue factor (TFlog) were assessed as indices of enterocyte damage, systemic inflammation, and blood coagulation, respectively, before and after the 3-h heat exposure. In the younger cohort, I-FABPlog concentration did not increase from pre to post heat exposure (p = 0.264, d = 0.20), although it was elevated in the older group (p = 0.014, d = 0.67). The magnitude of the increase in I-FABPlog was greater in the older participants (p = 0.084, d = 0.55). Across all participants, there was no correlation between the change in core temperature and the change in IFABPlog. There was no change in IL-8log in the younger group (p = 0.193, d = 0.23) following heat exposure, but we observed a decrease in IL-8log in the older group (p = 0.047, d = 0.48). TFlog decreased in the younger group (p = 0.071, d = 0.41), but did not change in the older group (p = 0.193, d = 0.15). Our data indicate that I-FABPlog concentration (an index of enterocyte damage) is increased in older humans during a 3-h extreme heat exposure. Future studies should determine whether this marker reflects increased gastrointestinal barrier permeability in older individuals during heat exposure.

Age alters the thermoregulatory responses to extreme heat exposure with accompanying activities of daily living.

Older adults are at greater risk for heat-related morbidity and mortality, due in part to age-related reductions in heat dissipating capabilities. Previous studies investigating the impact of age on responses to heat stress used approaches that lack activities of daily living and therefore may not accurately depict the thermal/physiological strain that would occur during actual heatwaves. We sought to compare the responses of young (18-39 yr) and older (≥65 yr) adults exposed to two extreme heat simulations. Healthy young (n = 20) and older (n = 20) participants underwent two 3-h extreme heat exposures on different days: 1) DRY (47°C and 15% humidity) and 2) HUMID (41°C and 40% humidity). To mimic heat generation comparable with activities of daily living, participants performed 5-min bouts of light physical activity dispersed throughout the heat exposure. Measurements included core and skin temperatures, heart rate, blood pressure, local and whole body sweat rate, forearm blood flow, and perceptual responses. Δ core temperature (Young: 0.68 ± 0.27°C vs. Older: 1.37 ± 0.42°C; P < 0.001) and ending core temperature (Young: 37.81 ± 0.26°C vs. Older: 38.15 ± 0.43°C; P = 0.005) were greater in the older cohort during the DRY condition. Δ core temperature (Young: 0.58 ± 0.25°C vs. Older: 1.02 ± 0.32°C; P < 0.001), but not ending core temperature (Young: 37.67 ± 0.34°C vs. Older: 37.83 ± 0.35°C; P = 0.151), was higher in the older cohort during the HUMID condition. We demonstrated that older adults have diminished thermoregulatory responses to heat stress with accompanying activities of daily living. These findings corroborate previous reports and confirm epidemiological data showing that older adults are at a greater risk for hyperthermia.NEW & NOTEWORTHY Using an experimental model of extreme heat exposure that incorporates brief periods of light physical activity to simulate activities of daily living, the extent of thermal strain reported herein more accurately represents what would occur during actual heatwave conditions. Despite matching metabolic heat generation and environmental conditions, we show that older adults have augmented core temperature responses, likely due to age-related reductions in heat dissipating mechanisms.

Monitoring diurnal dynamics of surface urban heat island for urban agglomerations using ECOSTRESS land surface temperature observations

Extreme heat exposure at the regional scale is warranted for special attention due to the changing global climate yet notable regional disparities in the effect of warming. NASA's latest ECOSTRESS mission generates LST images with a swath width of about 400 km and a 70-m resolution for varying times of day/night and provides a new opportunity for regional SUHI studies. Here we demonstrated the capability of ECOSTRESS data for studying spatiotemporal variations of LST and SUHI over an urban agglomeration that centers on a megacity, Xi'an, in Northwest China and includes cities of various sizes and geographical and economic settings. Our results revealed the unequal exposures of different-sized cities to SUHI effects in the diurnal cycle, with a maximum value of about 10 °C. Meanwhile, inter-city SUHI showed higher spatial variability in the late morning, midday, and early afternoon than in the evening, midnight, and early morning. Urban vegetation and percent imperviousness can regulate SUHI spatial variations in each city, and the impact varied across cities or at different diurnal times. The findings can have implications for assessing extreme heat exposure in regional cities, enlightening the urban SUHI mitigation strategies, and informing future regional sustainability.

Ambient temperature, heat stress and fetal growth: A review of placenta-mediated mechanisms

Pregnancy is increasingly considered a period of vulnerability for extreme heat exposure. Multiple lines of evidence support that heat stress is associated with placental insufficiency, poor fetal growth and decreased birth weight. In this narrative review, we first summarize evidence linking ambient temperature or experimentally-induced heat stress with fetal and placental growth outcomes in humans, ruminants and murine species. We then synthesize the literature on putative underlying biological pathways with a focus on the placenta. Reviewed mechanisms include: reduced uterine-placental blood flow, impaired supply of metabolic substrates to the fetus, activation of the maternal stress-response system, and disruption of other endocrine and immune system endpoints. Taken together, this body of evidence supports that exposure to extreme ambient heat likely has adverse consequences for placental development and function. However, research investigating placenta-mediated pathophysiological mechanisms in humans remains extremely limited.

Understanding and assessing demographic (in)equity resulting from extreme heat and direct sunlight exposure due to lack of tree canopies in Norfolk, VA using agent-based modeling

Prolonged exposure to extreme heat and direct sunlight can result in illness and death. In urban areas of dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat, harmful environmental exposures to extreme heat and direct sunlight for residents can occur on a daily basis during certain parts of the year. Tree canopies provide shade and help to cool the environment, making mature trees with large canopies a simple and effective way to reduce urban heat and avoid direct sunlight. We develop a demographically representative agent-based model to understand the extent to which different demographics of residents in Norfolk, VA are (in)equitably shaded from direct sunlight and extreme heat conditions during a walk on a clear summer day. In the model each agent represents a different resident of Norfolk, VA. We use the model to assess the extent to which the city’s tree planting plan will be effective in remediating any existing inequities. Our results show that inequitable conditions exist for residents at (1) different education levels, (2) different income levels, and (3) living in different census tracts. Norfolk’s Tree Planting Program effectively reduces the distance residents of all demographics walk in extreme heat and are exposed to direct sunlight. However, residents of the city at lower income levels still experience statistically significantly more extreme heat and direct sunlight exposure due to a lack of tree canopies in summer months than those at higher income levels.

Hyperlocal Observations Reveal Persistent Extreme Urban Heat in Southeast Florida

Abstract Cities around the world are experiencing the effects of climate change via increasing extreme heat worsened by urbanization. Within cities, there are disparities in extreme heat exposure that are apparent in various surface and remotely sensed observations, as well as in the health impacts. There are, however, large data gaps in our ability to quantify the heat experienced by people in their daily lives across urban areas. In this paper, we use hyperlocal observations to measure heat around Miami–Dade County, Florida. Temperature and humidity measurements were collected at sites throughout the county between 2018 and 2021 with low-cost sensors. By comparing these hyperlocal observations with a National Weather Service (NWS) site at the Miami International Airport (MIA), we show that maximum temperatures are on average 6°F (3.3°C) higher and maximum heat index values are 11°F (6.1°C) higher at sites in the county than at MIA. These measurements show that many sites frequently record a heat index above the local threshold value for heat advisory. This is in contrast with the fact that few forecast advisories are issued, and there are correspondingly few exceedances of the threshold at MIA. We use these results to motivate a discussion about the issues of this particular threshold for Miami–Dade County. We highlight the need for data that are closer to residents’ lived experience to assess the impacts of heat and help inform local and regional decision-making, particularly where heat exposure may be underappreciated as a potential public health hazard.

The relationship between extreme ambient temperature and small for gestational age: A cohort study of 1,436,480 singleton term births in China

Studies have shown that exposure to extreme ambient temperature can contribute to adverse pregnancy outcomes, however, results across studies have been inconsistent. We aimed to evaluate the relationships between trimester-specific extreme temperature exposures and fetal growth restriction indicated by small for gestational age (SGA) in term pregnancies, and to assess whether and to what extent this relationship varies between different geographic regions. We linked 1,436,480 singleton term newborns (2014–2016) in Hubei Province, China, with a sub-district-level temperature exposures estimated by a generalized additive spatio-temporal model. Mixed-effects logistic regression models were employed to estimate the effects of extreme cold (temperature ≤5th percentile) and heat exposures (temperature >95th percentile) on term SGA in three different geographic regions, while adjusting for the effects of maternal age, infant sex, the frequency of health checks, parity, educational level, season of birth, area-level income, and PM2.5 exposure. We also stratified our analyses by infant sex, maternal age, urban‒rural type, income categories and PM2.5 exposure for robustness analyses. We found that both cold (OR:1.32, 95% CI: 1.25–1.39) and heat (OR:1.17, 95% CI: 1.13–1.22) exposures during the third trimester significantly increased the risk of SGA in the East region. Only extreme heat exposure (OR:1.29, 95% CI: 1.21–1.37) during the third trimester was significantly related to SGA in the Middle region. Our findings suggest that extreme ambient temperature exposure during pregnancy can lead to fetal growth restriction. Governments and public health institutions should pay more attention to environmental stresses during gestation, especially in the late stage of the pregnancy.

Pollen Germination and Tube Growth in Northern Highbush Blueberry are Inhibited by Extreme Heat

The increasing intensity and frequency of extreme heat events threaten crop productivity globally. Certain phases of plant reproduction necessary for fertilization are highly sensitive to extreme heat, particularly during pollen development, germination, and tube elongation. However, few studies have assessed the effects of extreme heat on pollen performance in perennial crop plants. To understand how northern highbush blueberry pollen responds to high temperatures, we quantified pollen germination and pollen tube growth in vitro using four commercially relevant cultivars (Bluecrop, Elliott, Jersey, and Liberty) in climate-controlled chambers. We also tested recovery from high heat in ‘Bluecrop’ to determine whether pollen tubes can still germinate and grow after short bursts of extreme heat. We found the highest proportion of germinated pollen tetrads and the greatest pollen tube growth at 20 and 30 °C, and the lowest levels at 10 and 40 °C, with nearly complete inhibition at 40 °C. Exposure to between 30 and 40 °C revealed significant reduction in pollen germination and tube growth above 35 °C across all cultivars and assessment times. Exposure to 37.5 °C for only 4 hours resulted in substantial reductions in pollen germination and pollen tube growth, even after pollen was moved to optimal conditions of 25 °C. Extreme heat exposure, even for a short duration, significantly limits blueberry pollen germination and tube development. This is expected to have cascading effects on fruit set and crop yield. The nonreversibility of the effects on pollen highlights the need to prevent fields reaching damaging temperatures by developing crop monitoring and management strategies to protect crops during bloom.

Awareness and interventions to reduce dehydration in pregnant, postpartum women, and newborns in rural Kenya.

Extreme heat exposure is associated with adverse outcomes in pregnancy and has the potential to impact maternal, neonatal and child health for a lifetime. In an extremely hot climate, pregnant women face an increased risk of premature birth, stillbirth, low birth weight, congenital anomalies and pre-eclampsia. In low- and middle-income countries (LMICs), socio-demographic and behavioural practices may negatively affect body hydration during high temperatures. The possible causes and consequences of dehydration in the heat are poorly understood and have been little discussed in the literature.Living in a hot climate poses various challenges, including dehydration, where biological mechanisms and insufficient access to water can lead to dehydration in women and children, with consequences for the health of both mothers and children, particularly in relation to breastfeeding habits. During pregnancy, increased metabolic and cardiovascular demands interact with heat exhaustion and reduced availability of fresh water, which can affect the child's growth and development. In this opinion piece, we emphasise the possible causes and impacts of dehydration in extreme heat on the health and well-being of mothers and children. We encourage more research, focused on biology and epidemiology, related to raising awareness and implementing adaptations to reduce the risk of dehydration in pregnant, postpartum women and newborns in the context of climate change-related heat exposure.

Cardiorespiratory and autonomic adjustments to exercise with healthy ageing: considerations with extreme heat exposure and hydration.

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Physiological responses of adults with coronary artery disease during extreme heat exposure

Introduction: Extreme heat is becoming more frequent due to climate change. Different regions experience different forms of heat, such humid or dry heat, a greater risk of morbidity and mortality becomes apparent with higher temperatures. Adults with heart disease are especially vulnerable to the health risks of extreme heat. One possible reason for this greater risk is that adults with heart disease might experience greater physiological heat strain during extreme heat exposure. The objective of this study was to determine if adults with coronary artery disease (CAD) experience greater physiological strain relative to adults without CAD during hot/humid and very hot/dry heat exposures.Methods: 28 adults with stable CAD (2 females/26 males, 66±7 y, 1.96±0.17 m2) and 26 adults without CAD (non-CAD; 13 females/12 males, 69±4 y, 1.86±0.21 m2) rested for 3 hours in hot/humid (HH; 38°C/60% relative humidity; n= 22 CAD and 26 non-CAD) and very hot/dry (VHD; 45°C/15% relative humidity; n=24 CAD and 13 non-CAD) environments on separate days. Participants consumed 3 mL/kg/h of water during each exposure. Core (rectal) and skin temperatures, heart rate, and whole-body sweat loss were measured. Results: During exposure to HH, adults with CAD experienced a greater increase in core (0.58±0.28°C vs. 0.37±0.23°C, p=0.009) and mean skin (5.08±1.11°C vs. 4.06±0.76°C, p=0.0005) temperatures and sweat more (832±252 g vs. 471±244 g, p&lt;0.0001). The increase in heart rate (CAD: 9±7 bpm vs. non-CAD: 9±6 bpm, p=0.914) and percent change in body weight (CAD: +0.12±0.32% vs. non-CAD: +0.25±0.22%, p=0.106) did not differ between groups. During exposure to VHD, adults with CAD experienced a greater increase in mean skin temperature (5.79±1.06°C vs. 4.92±1.23°C, p=0.029), greater sweat loss (1239±171 g vs. 794±159 g, p&lt;0.0001), and greater percent change in body weight (-0.41±0.29% vs. -0.11±0.16%, p=0.001). The change in core temperature (CAD: 0.62±0.37°C vs. healthy: 0.48±0.21°C, p=0.092) and heart rate (CAD: 9±7 bpm vs. healthy: 13±6 bpm, p=0.196) did not differ between groups. Conclusion: During hot/humid heat exposure, adults with CAD experience greater thermal strain and fluid loss, whereas they experience greater fluid loss and dehydration during a very hot/dry heat exposure. The greater physiological heat strain experienced by adults with CAD may reflect the impact of altered cardiovascular function and/or medications on internal distribution and ultimately contribute to a greater risk of heat-related mortality. National Health and Medical Research Council This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Impact of Extreme Heat Exposure on Pregnant People and Neonates: A State of the Science Review.

The relationship between heat exposure and perinatal morbidity and mortality is of increasing concern as global temperatures rise and extreme heat events become more frequent and intense. Heat exposure can lead to a multitude of harmful outcomes for pregnant individuals and neonates, including hospitalization and death. This state of the science review explored the evidence on the associations between heat exposure and negative health outcomes during pregnancy and the neonatal period. Findings suggest that improving health care provider and patient awareness of heat-related risks and implementing specific interventions could mitigate adverse outcomes. Furthermore, public health and other policy interventions are needed to increase thermal comfort and reduce societal exposure to extreme heat and related risks. Early warning systems, medical alerts, provider and patient education, and increased access to health care and thermal comfort may improve pregnancy and early life health outcomes.

Effectiveness of travel behavior and infrastructure change to mitigate heat exposure

Urban heat exposure is an increasing health risk among urban dwellers. Many cities are considering accommodating active mobility, especially walking and biking, to reduce greenhouse gas emissions. However, promoting active mobility without proper planning and transportation infrastructure to combat extreme heat exposure may cause more heat-related morbidity and mortality, particularly in future with projected climate change. This study estimated the effectiveness of active trip heat exposure mitigation under built environment and travel behavior change. Simulations of the Phoenix metro region's 624,987 active trips were conducted using the activity-based travel model (ABM), mean radiant temperature (TMRT, net human radiation exposure), transportation network, and local climate zones. Two scenarios were designed to reduce traveler exposure: one that focuses on built environment change (making neighborhoods cooler) and the other on travel behavior (switching from shorter travel time but higher exposure routes to longer travel time but cooler routes) change. Travelers experienced TMRT heat exposure ranging from 29°C to 76°C (84°F to 168°F) without environmental or behavioral change. Active trip TMRT exposures were reduced by an average of 1.2–3.7°C when the built environment was changed from a hotter to cooler design. Behavioral changes cooled up to 10 times more trips than changes in built environment changes. The marginal benefit of cooling decreased as the number of cooled corridors transformed increased. When the most traveled 10 km of corridors were cooled, the marginal benefit affected over 1,000 trips/km. However, cooling all corridors results in marginal benefits as low as 1 trip/km. The results reveal that heavily traveled corridors should be prioritized with limited resources, and the best cooling results come from environment and travel behavior change together. The results show how to surgically invest in travel behavior and built environment change to most effectively protect active travelers.

The role of extreme heat exposure on premature rupture of membranes in Southern California: A study from a large pregnancy cohort

BackgroundSignificant mortality and morbidity in pregnant women and their offspring are linked to premature rupture of membranes (PROM). Epidemiological evidence for heat-related PROM risk is extremely limited. We investigated associations between acute heatwave exposure and spontaneous PROM. MethodsWe conducted this retrospective cohort study among mothers in Kaiser Permanente Southern California who experienced membrane ruptures during the warm season (May-September) from 2008 to 2018. Twelve definitions of heatwaves with different cut-off percentiles (75th, 90th, 95th, and 98th) and durations (≥ 2, 3, and 4 consecutive days) were developed using the daily maximum heat index, which incorporates both daily maximum temperature and minimum relative humidity in the last gestational week. Cox proportional hazards models were fitted separately for spontaneous PROM, term PROM (TPROM), and preterm PROM (PPROM) with zip codes as the random effect and gestational week as the temporal unit. Effect modification by air pollution (i.e., PM2.5 and NO2), climate adaptation measures (i.e., green space and air conditioning [AC] penetration), sociodemographic factors, and smoking behavior was examined. ResultsIn total, we included 190,767 subjects with 16,490 (8.6%) spontaneous PROMs. We identified a 9–14% increase in PROM risks associated with less intense heatwaves. Similar patterns as PROM were found for TPROM and PPROM. The heat-related PROM risks were greater among mothers exposed to a higher level of PM2.5 during pregnancy, under 25 years old, with lower education and household income level, and who smoked. Even though climate adaptation factors were not statistically significant effect modifiers, mothers living with lower green space or lower AC penetration were at consistently higher heat-related PROM risks compared to their counterparts. ConclusionUsing a rich and high-quality clinical database, we detected harmful heat exposure for spontaneous PROM in preterm and term deliveries. Some subgroups with specific characteristics were more susceptible to heat-related PROM risk.

Examining the Optimal Placement of Cooling Centers to Serve Populations at High Risk of Extreme Heat Exposure in 81 US Cities.

Although extreme heat can impact the health of anyone, certain groups are disproportionately affected. In urban settings, cooling centers are intended to reduce heat exposure by providing air-conditioned spaces to the public. We examined the characteristics of populations living near cooling centers and how well they serve areas with high social vulnerability. We identified 1402 cooling centers in 81 US cities from publicly available sources and analyzed markers of urban heat and social vulnerability in relation to their locations. Within each city, we developed cooling center access areas, defined as the geographic area within a 0.5-mile walk from a center, and compared sociodemographic characteristics of populations living within versus outside the access areas. We analyzed results by city and geographic region to evaluate climate-relevant regional differences. Access to cooling centers differed among cities, ranging from 0.01% (Atlanta, Georgia) to 63.2% (Washington, DC) of the population living within an access area. On average, cooling centers were in areas that had higher levels of social vulnerability, as measured by the number of people living in urban heat islands, annual household income below poverty, racial and ethnic minority status, low educational attainment, and high unemployment rate. However, access areas were less inclusive of adult populations aged ≥65 years than among populations aged <65 years. Given the large percentage of individuals without access to cooling centers and the anticipated increase in frequency and severity of extreme heat events, the current distribution of centers in the urban areas that we examined may be insufficient to protect individuals from the adverse health effects of extreme heat, particularly in the absence of additional measures to reduce risk.