Assessing 7-year heat-stress exposures and adaptation strategies for children using a real-time monitoring network in Taiwan.

Wet-bulb globe temperature (WBGT) serves as a suitable heat-stress indicator not only for outdoor workers but also for the general public. However, studies on WBGT exposure among the general population are scarce. This research represents the first attempt to assess WBGT exposure of school-aged children. Utilizing a real-time monitoring network in Taiwan, WBGT exposure of school-aged children (7-15 years) were estimated during May to October from 2016 to 2022. Important determinants and spatiotemporal variability of WBGT levels were explored, with hot spots and peak hours of WBGT identified. Macro- and micro-scale adaptation strategies applicable at schools were also evaluated for their effectiveness in reducing heat stress for students. Results showed that the mean daily maximum WBGT (WBGTmax) was 33.1 ± 3.8 °C at 20 stations across Taiwan but could reach/exceed 36 °C (threshold of the dangerous category) at certain hot spots for 42.3-52.0 % of days between May and October. Local geographic features sometimes outweigh the latitude in explaining the spatial variations. Contrary to temperature, WBGT peaked during 10 am to noon rather than from noon to 1:59 pm in most schools, due to clouds blocking solar radiation in the afternoon. This finding has significant implications for scheduling outdoor physical classes/activities to reduce children's heat-health risks. Setting up on-site WBGT monitoring on surfaces that children mostly encounter at schools or utilizing data from nearby weather stations could provide a near real-time heat-health warning. Moreover, providing shades outdoors, relocating outdoor classes indoors, and using air-conditioning would reduce WBGT by 2.1-5.8, 3.7-7.3, and 2.5-5.9 °C, respectively; and would significantly decrease the percentages of WBGT ≥34 °C, which is associated with increased heat-related emergency visits among children in Taiwan. The methodology applied serves as a useful reference for assessing WBGT exposure and adaptation strategies, providing the scientific foundation for heat-health adaptation measures.

Preferences for drinking water temperature in mice vary with ambient temperature.

Temperature detection and temperature preference are critical for the maintenance of thermal homeostasis and protection from noxious temperature. Methods to measure the time spent on plates of different temperatures such as the two-plate test and thermal-gradient test are generally used to evaluate temperature preference. In this study, we established a temperature preference test that assesses water drinking behavior by modifying the two-bottle taste preference test. We found that mice in a common-temperature environment of 23 °C avoid drinking water more than 40 °C. While mice in a common-temperature environment preferred 10 °C and 30 °C water equally, mice in a hot environment at 35 °C preferred to 10 °C water compared to 30 °C water. Moreover, mice in a cold environment of 10 °C did not avoid drinking 40 °C water compared to 10 °C water. From these results, the temperature preference test that we developed could be used to evaluate temperature preference owing to the ambient temperature changes.

Early-age heat exposure improved growth performance and heat tolerance in broilers.

A total of 440 one-day-old healthy male Arbor Acres broilers were equally assigned to a control group (CTL) and an early-age high-temperature exposure (EHT) group (4 replicates per group, 55 chickens per replicate). At d 3, the broilers in CTL group were reared in the normal temperature 33 ± 1°C, while the broilers in EHT group were exposed to 36 ± 1°C for 24 h. At d 43, all broilers were treated with an acute high temperature 35 ± 1°C for 5 h. The results showed that average daily gain in EHT group was decreased at d 3, but average daily gain in EHT group was increased at d 36 to 42 (P < 0.05). Plasma GLU level in EHT group was lower in broilers at d 7 or facing subsequently high temperature for 5 h (P < 0.05). The relative expression of myogenic differentiation (MyoD) gene in pectoralis major and myogenic factor 5 (Myf5) gene in biceps femoris were significantly improved at d 42 after early-age heat exposure (P < 0.05). Broilers in EHT group have a higher temperature tolerance with a lower mortality than control broilers (P < 0.05). Broilers in EHT group have a lower rectal temperature and a higher comb and ear temperature when facing subsequently acute high temperature than control broilers (P < 0.05). In addition, our study demonstrated that early-age heat exposure significantly decreased the mortality and increased the heat tolerance of broilers when facing an acute short-term heat exposures. Early-age heat exposure increased the process of myogenesis via up-regulating the MyoD and Myf5 gene expression in skeletal muscle, which accelerated average daily gain.

SchoolHEAT: Racial and Ethnic Inequity in School Temperature.

Exposure to high environmental temperature is detrimental to health through multiple pathways. This paper describes disparities in school-based high-temperature exposure at metropolitan schools in the United States. Using school location and sociodemographic data from the National Center for Education Statistics, neighborhood data from the US Census Bureau, and land surface temperature (LST) data from the Aqua Earth-observing satellite mission, we find that for every 10% more Black or Hispanic residents in the neighborhood, schools have LST 0.25 °C and 0.38 °C hotter, respectively. When the Black or Hispanic student population is greater than the neighborhood population, LST is an additional 0.20 °C and 0.40 °C for each 10% increase in students over neighborhood population, respectively. Black and Hispanic students are overrepresented in the hottest schools, making up 58.7% of students in the hottest 20% of schools, compared to only 30.0% of students in the coolest 20% of schools.

From Public Forecasts to Occupational Heat Safety Management: Evaluating the Effectiveness of the National Weather Service's Operational Heat Risk Forecasts.

Heat poses a major environmental risk to occupational safety, necessitating timely insights into associated risks to safeguard workers. In June 2022, the National Weather Service (NWS) initiated operational wet bulb globe temperature (WBGT) forecasts, offering valuable information for heat risk management. This study evaluates the effectiveness of NWS WBGT forecasts, aiming to identify potential areas of caution and improvements for their application for occupational safety management. To this end, the study examines 1.3 million hourly historical NWS WBGT forecast data, comparing it with observed data from 252 weather stations across the US during the summer of 2023. The results offer key insights, revealing that: (1) the accuracy of NWS WBGT forecasts is influenced more by the times of interest than by the forecast horizons; (2) NWS WBGT forecast accuracy varies across different climates in the US, with air temperature bias being the most influential factor in this inaccuracy; and (3) while NWS WBGT forecasts accurately identify the lowest heat risks (i.e. no heat risk), their performance decreases at higher risk levels, emphasizing the importance of careful interpretation in safety management. These insights offer guidance for more cautious interpretations of NWS WBGT forecasts and lay the foundation for future studies on leveraging operational weather forecasting services in effective heat mitigation strategies.

A case of erythema ab igne with histopathological features resembling keratosis lichenoides chronica.

This case describes a pediatric patient with a history of ichthyosis vulgaris and global anhidrosis who was diagnosed with erythema ab igne (EAI), a rare dermatosis resulting from chronic heat exposure. After developing progressive, reticulated brown patches on his extremities and abdomen, extensive diagnostic investigations were conducted to rule out autoimmune, vascular, and genetic etiologies. Bloodwork was unrevealing and biopsies showed histologic features closely resembling keratosis lichenoides chronica. Ultimately, after discovering the patient had prolonged exposure to a space heater, the diagnosis of EAI was made. This case underscores the diagnostic challenges in pediatric EAI cases and emphasizes the importance of careful history taking as part of a comprehensive evaluation.

Effect of vitamin C and hawthorn beverage formula on blood pressure and oxidative stress in heat-exposed workers: a cluster-randomized controlled trial.

BACKGROUND AND OBJECTIVES: There is no evidence on antioxidant-rich diets in preventing hypertension in heat-exposed workers. We aimed to evaluate the effects of formula supplemented with vitamin C (Vit C) and hawthorn beverage on reducing blood pressure (BP) and oxidative stress levels in heat-exposed workers. METHODS AND STUDY DESIGN: In the 40-day cluster-randomized controlled trial, four heat-exposed shift-teams were enrolled and randomly assigned to the intervention and control groups. The intervention group was given one Vit C tablet (130 mg) and a 500 mL hawthorn beverage containing 278.7 mg flavonoids daily whereas the control group was given 500 mL of slightly salted water daily; both groups were provided education on a healthy diet. BP and creatinine-corrected urinary 8-isoprostane-prostaglandin F2α (8-iso-PGF2α/Cr) concentrations were assessed at baseline, Day 17 (only BP) and Day 41, respectively. RESULTS: Compared with the control group, the systolic BP (SBP), diastolic BP (DBP), and log10-transformed 8-iso-PGF2α/Cr in the inter-vention group decreased by 7.41 mmHg, 7.93 mmHg and 0.232, respectively, from baseline to day 41 (all p<0.05). When comparing BP levels at baseline, DBP in the intervention group was reduced by 5.46 mmHg when compared to control (p<0.05) among participants with lower baseline BP; SBP and DBP experienced reductions of 9.74 and 9.22 mmHg among participants with higher baseline BP (both p<0.05). CONCLUSIONS: Supplementation of Vit C and flavonoids rich hawthorn beverage to heat-exposed workers prevented elevated BP caused by heat exposure which may be attributed to its oxidative stress inhibition effects.

p38MAPK/HSPB1 is involved in the regulatory effects of selenomethionine on the apoptosis, viability and testosterone secretion of sheep Leydig cells exposed to heat.

Testosterone derived from testicular Leydig cells (LCs) is important for male sheep, and the testis is susceptible to external temperature. The present study aimed to explore the alleviating effect of selenomethionine (Se-Met) on heat-induced injury in Hu sheep LCs. Isolated LCs were exposed to heat (41.5°C, heat exposure, HE) or not (37°C, nonheat exposure, NE), and cells in NE and HE were treated with 0 (C) or 8 µmol/L (S) Se-Met for 6 h. Cell viability, testosterone level, and the expression of GPX1, HSD3B, apoptosis-related genes and p38 mitogen-activated protein kinase (p38MAPK)/heat shock protein beta-1 (HSPB1) pathway were examined. The results showed that Se-Met increased GPX1 expression (NE-S vs. NE-C: 2.28-fold; HE-S vs. HE-C: 2.36-fold, p < 0.05) and alleviated heat-induced decrease in cell viability (HE-S vs. HE-C: 1.41-fold; HE-C vs. NE-C: 0.61-fold, p < 0.01), although the viability was still lower than that in the NE-C cells (HE-S vs. NE-C: 0.85-fold) and Se-Met-treated cells (HE-S vs. NE-S: 0.81-fold). Se-Met relieved heat-induced decrease in testosterone level (HE-S vs. HE-C: 1.84-fold, p < 0.05) and HSD3B expression (HE-S vs. HE-C: 1.67-fold, p < 0.05). Se-Met alleviated heat-induced increase in Bcl2-associated protein X (BAX) expression (HE-C vs. HE-S: 2.4-fold, p < 0.05), and decrease in B-cell lymphoma-2 (BCL2) expression (HE-S vs. HE-C: 2.62-fold, p < 0.05), resulting in increased BCL2/BAX ratio in the HE-S cells (HE-S vs. HE-C: 5.24-fold, p < 0.05). Furthermore, Se-Met alleviated heat-induced activation of p-p38MAPK/p38MAPK (HE-C vs. HE-S: 1.79-fold, p < 0.05) and p-HSPB1/HSPB1 (HE-C vs. HE-S: 2.72-fold, p < 0.05). In conclusion, p38MAPK/HSPB1 might be involved in Se-Met-mediated alleviation of heat-induced cell apoptosis, cell viability and testosterone secretion impairments in sheep LCs.

Associations between PM2.5, ambient heat exposure and congenital hydronephrosis in southeastern China.

Objectives: This research aims to analyze how exposure to fine particulate matter (PM2.5) and ambient heat during pregnancy increases the risk of congenital hydronephrosis (CH) in newborns. Methods: A case-control study was conducted to investigate the relationship between exposure to PM2.5 and ambient heat during pregnancy and the occurrence of CH in newborns. The study, which was conducted from 2015 to 2020, included 409 infants with CH as the case group and 409 infants without any abnormalities as the control group. Using spatial remote sensing technology, the exposure of each pregnant mother to PM2.5 concentration was meticulously mapped. Additionally, data on the ambient temperature of exposure for each participant were also collected. A logistics regression model was used to calculate the influence of exposure to PM2.5 and ambient heat on the occurrence of CH. Stratified analysis and interaction analysis were used to study the interaction between ambient heat exposure and PM2.5 on the occurrence of CH. Results: At the 6th week of gestation, exposure to PM2.5 may increase the risk of CH. For every 10 µg/m3 increase in PM2.5 exposure, the risk of CH increased by 2% (95%CI = 0.98, 1.05) at a p-value of >0.05, indicating that there was no significant relationship between the results. Exposure to intense heat at 6th and 7th weeks of gestation increased the risk of CH. Specifically, for every 1°C increase in heat exposure, the risk of CH in offspring increased by 21% (95%CI = 1.04, 1.41) during the 6th week and 13% during the 7th week (95%CI = 1.02, 1.24). At 5th and 6th weeks of gestation, the relative excess risk due to interaction (RERI) was greater than 0 at the 50th percentile (22.58°C), 75th percentile (27.25°C), and 90th percentile (29.13°C) of daily maximum temperature (Tmax) distribution, indicating that the risk of CH was higher when exposed to both ambient heat and PM2.5 at the same time compared to exposure to a single risk factor. Conclusion: Exposure to higher levels of PM2.5 and ambient heat during pregnancy increases the risk of CH in infants. There was a positive interaction between exposure to intense heat and high concentration of PM2.5 on the occurrence of CH.

A longitudinal assessment of heat exposure and biomarkers of kidney function on heat shock protein 70 and antibodies among agricultural workers.

BACKGROUND: Exposure to extreme heat impacts millions of people worldwide and outdoor workers are among the populations most affected by hot temperatures. Heat stress induces several biological responses in humans, including the production of heat shock proteins (HSP) and antibodies against HSP (anti-HSP) which may play a central role in the body's cellular response to a hot environment. OBJECTIVE: This longitudinal study investigated the impact of elevated temperatures and humidity on the presence of HSP70 and anti-HSP70 and examined relationships with markers of kidney function in an at-risk workforce under conditions of extreme heat and exertion in Guatemala. METHODS: We collected ambient temperature and relative humidity data as well as biomarkers and clinical data from 40 sugarcane workers at the start and the end of a 6-month harvest. We used generalized mixed-effects models to estimate temperature effects on HSP70 and anti-HSP70 levels. In addition, we examined trends between HSP70 and anti-HSP70 levels and markers of kidney function across the harvest. RESULTS: At the end of the harvest, temperatures were higher, and workers had, on average, higher levels of HSP70 and anti-HSP70 compared to the beginning of the season. We observed significant increasing trends with temperature indices, heat index, and HSP70 levels. Maximum temperature was associated with HSP70 increments after controlling for age, systolic and diastolic blood pressure (ß: 0.21, 95% Confidence Interval: 0.09, 0.33). Kidney function decline across the harvest was associated with both higher levels of anti-HSP70 levels at the end of the harvest as well as greater increases in anti-HSP70 levels across the harvest. CONCLUSIONS: These results suggest that workplace heat exposure may increase the production of HSP70 and anti-HSP70 levels and that there may be a relationship between increasing anti-HSP70 antibodies and the development of renal injury. HSP70 holds promise as a biomarker of heat stress in exposed populations.

The impact of increasing ambient temperature on allergic rhinitis: A systematic review and meta-analysis of observational studies.

INTRODUCTION: Global warming appears to initiate and aggravate allergic respiratory conditions via interaction with numerous environmental factors. Temperature, commonly identified as a factor in climate change, is important in this process. Allergic rhinitis, a common respiratory allergy, is on the rise and affects approximately 500 million individuals worldwide. The increasing ambient temperature requires evaluation regarding its influence on allergic rhinitis, taking into account regional climate zones. METHODS: A detailed search of PubMed, EMBASE, Scopus, Web of Science, MEDLINE, and CINAHL Plus databases, was conducted, encompassing observational studies published from 1991 to 2023. Original studies examining the relationship between increasing temperature and allergic rhinitis were assessed for eligibility followed by a risk of bias assessment. Random effects meta-analysis was utilized to measure the association between a 1 °C increase in temperature and allergic rhinitis-related outcomes. RESULTS: 20 studies were included in the qualitative synthesis, with nine of them subsequently selected for the quantitative synthesis. 20 included studies were rated as Level 4 evidence according to the Oxford Centre for Evidence-Based Medicine, and the majority of these reported good-quality evidence based on the Newcastle-Ottawa Quality Rating Scale. Using the Risk of Bias In Non-Randomized Studies of Exposure tool, the majority of studies exhibit a high risk of bias. Every 1 °C increase in temperature significantly raised the risk of allergic rhinitis-related outcomes by 29 % (RR = 1.26, 95 % CI: 1.11 to 1.50). Conversely, every 1 °C rise in temperature showed no significant increase in the odds of allergic rhinitis-related outcomes by 7 % (OR = 1.07, 95 % CI: 0.95 to 1.21). Subsequent subgroup analysis identified climate zone as an influential factor influencing this association. CONCLUSION: It is inconclusive to definitively suggest a harmful effect of increasing temperature exposure on allergic rhinitis, due overall very low certainty of evidence. Further original research with better methodological quality is required.

Dynamic molecular choreography induced by acute heat exposure in human males: a longitudinal multi-omics profiling study.

Introduction: Extreme heat events caused by occupational exposure and heat waves are becoming more common. However, the molecular changes underlying the response to heat exposure in humans remain to be elucidated. Methods: This study used longitudinal multi-omics profiling to assess the impact of acute heat exposure (50°C for 30 min) in 24 subjects from a mine rescue team. Intravenous blood samples were collected before acute heat exposure (baseline) and at 5 min, 30 min, 1 h, and 24 h after acute heat exposure (recovery). In-depth multi-omics profiling was performed on each sample, including plasma proteomics (untargeted) and metabolomics (untargeted). Results: After data curation and annotation, the final dataset contained 2,473 analytes, including 478 proteins and 1995 metabolites. Time-series analysis unveiled an orchestrated molecular choreography of changes involving the immune response, coagulation, acid-base balance, oxidative stress, cytoskeleton, and energy metabolism. Further analysis through protein-protein interactions and network analysis revealed potential regulators of acute heat exposure. Moreover, novel blood-based analytes that predicted change in cardiopulmonary function after acute heat exposure were identified. Conclusion: This study provided a comprehensive investigation of the dynamic molecular changes that underlie the complex physiological processes that occur in human males who undergo heat exposure. Our findings will help health impact assessment of extreme high temperature and inspire future mechanistic and clinical studies.

Impacts of heat exposure in utero on long-term health and social outcomes: a systematic review.

BACKGROUND: Climate change, particularly global warming, is amongst the greatest threats to human health. While short-term effects of heat exposure in pregnancy, such as preterm birth, are well documented, long-term effects have received less attention. This review aims to systematically assess evidence on the long-term impacts on the foetus of heat exposure in utero. METHODS: A search was conducted in August 2019 and updated in April 2023 in MEDLINE(PubMed). We included studies on the relationship of environmental heat exposure during pregnancy and any long-term outcomes. Risk of bias was assessed using tools developed by the Joanna-Briggs Institute, and the evidence was appraised using the GRADE approach. Synthesis without Meta-Analysis (SWiM) guidelines were used. RESULTS: Eighteen thousand six hundred twenty one records were screened, with 29 studies included across six outcome groups. Studies were mostly conducted in high-income countries (n = 16/25), in cooler climates. All studies were observational, with 17 cohort, 5 case-control and 8 cross-sectional studies. The timeline of the data is from 1913 to 2019, and individuals ranged in age from neonates to adults, and the elderly. Increasing heat exposure during pregnancy was associated with decreased earnings and lower educational attainment (n = 4/6), as well as worsened cardiovascular (n = 3/6), respiratory (n = 3/3), psychiatric (n = 7/12) and anthropometric (n = 2/2) outcomes, possibly culminating in increased overall mortality (n = 2/3). The effect on female infants was greater than on males in 8 of 9 studies differentiating by sex. The quality of evidence was low in respiratory and longevity outcome groups to very low in all others. CONCLUSIONS: Increasing heat exposure was associated with a multitude of detrimental outcomes across diverse body systems. The biological pathways involved are yet to be elucidated, but could include epigenetic and developmental perturbations, through interactions with the placenta and inflammation. This highlights the need for further research into the long-term effects of heat exposure, biological pathways, and possible adaptation strategies in studies, particularly in neglected regions. Heat exposure in-utero has the potential to compound existing health and social inequalities. Poor study design of the included studies constrains the conclusions of this review, with heterogenous exposure measures and outcomes rendering comparisons across contexts/studies difficult. TRIAL REGISTRATION: PROSPERO CRD 42019140136.

Sex-specific effects of environmental temperature during gestation on fluctuating asymmetry in deciduous teeth.

OBJECTIVES: External environmental heat exposure during gestation impacts the physiology of human development in utero, but evidence for these impacts has not yet been explored in dentition. We examined deciduous teeth for fluctuating asymmetry (FA), a measure of developmental instability, together with gestational environmental temperature data drawn from historical weather statistics. MATERIALS AND METHODS: We measured dental casts from the longitudinal Burlington Growth Study, representing 172 participants (ages 3-6 years) with health records. FA was calculated from crown dimensions and intercuspal distances that develop during gestation. Multiple regression separated by sex (nfemale = 81) examined the effects of mean temperatures in each trimester, controlling for birth year. RESULTS: In females, increased temperatures during the first trimester are significantly associated with an increase in FA (p = 0.03), specifically during the second and third prenatal months (p = 0.03). There is no relationship between temperature and FA for either sex in the second or third trimesters, when enamel is formed. DISCUSSION: Dental instability may be sensitive to temperature in the first trimester in females during the scaffolding of crown shape and size in the earliest stages of tooth formation. Sexual dimorphism in growth investment strategies may explain the differences in results between males and females. Using enduring dental characteristics, these results advance our understanding of the effects of temperature on fetal physiology within a discrete period.

A double-edged sword: risks and benefits of heat for human health.

Extreme heat events will become more frequent and intense across the globe. In this science and society article we summarize how heat affects our body and discuss the associated health threats, but also the potential health benefits of heat exposure. Moreover, we provide practical suggestions for sustainable and health-oriented strategies to cope with heat.

Increased risk of preterm birth due to heat exposure during pregnancy: Exploring the mechanism of fetal physiology.

BACKGROUND: Heat exposure during pregnancy can increase the risk of preterm birth (PTB) through a range of potential mechanisms including pregnancy complications, hormone secretion and infections. However, current research mainly focuses on the effect of heat exposure on pathophysiological pathways of pregnant women, but ignore that maternal heat exposure can also cause physiological changes to the fetus, which will affect the risk of PTB. OBJECTIVE: In this study, we aimed to explore the mediating role of fetal heart rate (FHR) in the relationship between maternal heat exposure and PTB incidence. METHODS: We assigned heat exposure to a multi-center birth cohort in China during 2015-2018, which included all 162,407 singleton live births with several times FHR measurements during the second and third trimesters. We examined the associations between heat exposure, FHR and PTB in the entire pregnancy, each trimester and the last gestational month. The inverse odds ratio-weighted approach applied to the Cox regression was used to identify the mediation effect of heat exposure on PTB and its clinical subtypes via FHR. FINDINGS: Exposure to heat significantly increased the risk of PTB during the third trimester and the entire pregnancy, hazard ratios and 95 % CIs were 1.266 (1.161, 1.379) and 1.328 (1.218, 1.447). Heat exposure during the third trimester and entire pregnancy increased FHR in the third trimester by 0.24 bpm and 0.14 bpm. The proportion of heat exposure mediated by FHR elevation on PTB and its subtype ranged from 3.68 % to 24.06 %, with the significant mediation effect found for both medically indicated PTB and spontaneous PTB. CONCLUSIONS: This study suggests that heat exposure during pregnancy has an important impact on fetal health, and FHR, as a surrogate marker of fetal physiology, may mediate the increased risk of PTB caused by extreme heat. Monitoring and managing physiological changes in the fetus would constitute a promising avenue to reduce adverse birth outcomes associated with maternal heat exposure.

Experimental research in environmentally induced hyperthermic older persons: A systematic quantitative literature review mapping the available evidence.

The heat-related health burden is expected to persist and worsen in the coming years due to an aging global population and climate change. Defining the breadth and depth of our understanding of age-related changes in thermoregulation can identify underlying causes and strategies to protect vulnerable individuals from heat. We conducted the first systematic quantitative literature review to provide context to the historical experimental research of healthy older adults - compared to younger adults or unhealthy age matched cases - during exogenous heat strain, focusing on factors that influence thermoregulatory function (e.g. co-morbidities). We identified 4,455 articles, with 147 meeting eligibility criteria. Most studies were conducted in the US (39%), Canada (29%), or Japan (12%), with 71% of the 3,411 participants being male. About 71% of the studies compared younger and older adults, while 34% compared two groups of older adults with and without factors influencing thermoregulation. Key factors included age combined with another factor (23%), underlying biological mechanisms (18%), age independently (15%), influencing health conditions (15%), adaptation potential (12%), environmental conditions (9%), and therapeutic/pharmacological interventions (7%). Our results suggest that controlled experimental research should focus on the age-related changes in thermoregulation in the very old, females, those with overlooked chronic heat-sensitive health conditions (e.g. pulmonary, renal, mental disorders), the impact of multimorbidity, prolonged and cumulative effects of extreme heat, evidence-based policy of control measures (e.g. personal cooling strategies), pharmaceutical interactions, and interventions stimulating protective physiological adaptation. These controlled studies will inform the directions and use of limited resources in ecologically valid fieldwork studies.

Early Pulmonary Fibrosis-like Changes in the Setting of Heat Exposure: DNA Damage and Cell Senescence.

It is well known that extreme heat events happen frequently due to climate change. However, studies examining the direct health impacts of increased temperature and heat waves are lacking. Previous reports revealed that heatstroke induced acute lung injury and pulmonary dysfunction. This study aimed to investigate whether heat exposure induced lung fibrosis and to explore the underlying mechanisms. Male C57BL/6 mice were exposed to an ambient temperature of 39.5 ± 0.5 °C until their core temperature reached the maximum or heat exhaustion state. Lung fibrosis was observed in the lungs of heat-exposed mice, with extensive collagen deposition and the elevated expression of fibrosis molecules, including transforming growth factor-ß1 (TGF-ß1) and Fibronectin (Fn1) (p < 0.05). Moreover, epithelial-mesenchymal transition (EMT) occurred in response to heat exposure, evidenced by E-cadherin, an epithelial marker, which was downregulated, whereas markers of EMT, such as connective tissue growth factor (CTGF) and the zinc finger transcriptional repressor protein Slug, were upregulated in the heat-exposed lung tissues of mice (p < 0.05). Subsequently, cell senescence examination revealed that the levels of both senescence-associated ß-galactosidase (SA-ß-gal) staining and the cell cycle protein kinase inhibitor p21 were significantly elevated (p < 0.05). Mechanistically, the cGAS-STING signaling pathway evoked by DNA damage was activated in response to heat exposure (p < 0.05). In summary, we reported a new finding that heat exposure contributed to the development of early pulmonary fibrosis-like changes through the DNA damage-activated cGAS-STING pathway followed by cellular senescence.

Characterization of human extreme heat exposure using an outdoor thermal manikin.

Extreme heat is a current and growing global health concern. Current heat exposure models include meteorological and human factors that dictate heat stress, comfort, and risk of illness. However, radiation models simplify the human body to a cylinder, while convection ones provide conflicting predictions. To address these issues, we introduce a new method to characterize human exposure to extreme heat with unprecedented detail. We measure heat loads on 35 body surface zones using an outdoor thermal manikin ("ANDI") alongside an ultrasonic anemometer array and integral radiation measurements (IRM). We show that regardless of body orientation, IRM and ANDI agree even under high solar conditions. Further, body parts can be treated as cylinders, even in highly turbulent flow. This geometry-rooted insight yields a whole-body convection correlation that resolves prior conflicts and is valid for diverse indoor and outdoor wind flows. Results will inform decision-making around heat protection, adaptation, and mitigation.