Extreme Heat and Adverse Cardiovascular Outcomes in Australia and New Zealand: What Do We Know?

Extreme heat events are a leading natural hazard risk to human health. Under all future climate change models, extreme heat events will continue to increase in frequency, duration, and intensity. Evidence from previous extreme heat events across the globe demonstrates that adverse cardiovascular events are the leading cause of morbidity and mortality, particularly amongst the elderly and those with pre-existing cardiovascular disease. However, less is understood about the adverse effects of extreme heat amongst specific cardiovascular diseases (i.e., heart failure, dysrhythmias) and demographics (sex, ethnicity, age) within Australia and New Zealand. Furthermore, although Australia has implemented regional and state heat warning systems, most personal heat-health protective advice available in public health policy documents is either insufficient, not grounded in scientific evidence, and/or does not consider clinical factors such as age or co-morbidities. Dissemination of evidence-based recommendations and enhancing community resilience to extreme heat disasters within Australia and New Zealand should be an area of critical focus to reduce the burden and negative health effects associated with extreme heat. This narrative review will focus on five key areas in relation to extreme heat events within Australia and New Zealand: 1) the potential physiological mechanisms that cause adverse cardiovascular outcomes during extreme heat events; 2) how big is the problem within Australia and New Zealand?; 3) what the heat-health response plans are; 4) research knowledge and translation; and, 5) knowledge gaps and areas for future research.

Hot weather and heat extremes: health risks.

Hot ambient conditions and associated heat stress can increase mortality and morbidity, as well as increase adverse pregnancy outcomes and negatively affect mental health. High heat stress can also reduce physical work capacity and motor-cognitive performances, with consequences for productivity, and increase the risk of occupational health problems. Almost half of the global population and more than 1 billion workers are exposed to high heat episodes and about a third of all exposed workers have negative health effects. However, excess deaths and many heat-related health risks are preventable, with appropriate heat action plans involving behavioural strategies and biophysical solutions. Extreme heat events are becoming permanent features of summer seasons worldwide, causing many excess deaths. Heat-related morbidity and mortality are projected to increase further as climate change progresses, with greater risk associated with higher degrees of global warming. Particularly in tropical regions, increased warming might mean that physiological limits related to heat tolerance (survival) will be reached regularly and more often in coming decades. Climate change is interacting with other trends, such as population growth and ageing, urbanisation, and socioeconomic development, that can either exacerbate or ameliorate heat-related hazards. Urban temperatures are further enhanced by anthropogenic heat from vehicular transport and heat waste from buildings. Although there is some evidence of adaptation to increasing temperatures in high-income countries, projections of a hotter future suggest that without investment in research and risk management actions, heat-related morbidity and mortality are likely to increase.

Reducing the health effects of hot weather and heat extremes: from personal cooling strategies to green cities.

Heat extremes (ie, heatwaves) already have a serious impact on human health, with ageing, poverty, and chronic illnesses as aggravating factors. As the global community seeks to contend with even hotter weather in the future as a consequence of global climate change, there is a pressing need to better understand the most effective prevention and response measures that can be implemented, particularly in low-resource settings. In this Series paper, we describe how a future reliance on air conditioning is unsustainable and further marginalises the communities most vulnerable to the heat. We then show that a more holistic understanding of the thermal environment at the landscape and urban, building, and individual scales supports the identification of numerous sustainable opportunities to keep people cooler. We summarise the benefits (eg, effectiveness) and limitations of each identified cooling strategy, and recommend optimal interventions for settings such as aged care homes, slums, workplaces, mass gatherings, refugee camps, and playing sport. The integration of this information into well communicated heat action plans with robust surveillance and monitoring is essential for reducing the adverse health consequences of current and future extreme heat.

Sustainable solutions to mitigate occupational heat strain - an umbrella review of physiological effects and global health perspectives.

BACKGROUND: Climate change is set to exacerbate occupational heat strain, the combined effect of environmental and internal heat stress on the body, threatening human health and wellbeing. Therefore, identifying effective, affordable, feasible and sustainable solutions to mitigate the negative effects on worker health and productivity, is an increasingly urgent need. OBJECTIVES: To systematically identify and evaluate methods that mitigate occupational heat strain in order to provide scientific-based guidance for practitioners. METHODS: An umbrella review was conducted in biomedical databases employing the following eligibility criteria: 1) ambient temperatures > 28 °C or hypohydrated participants, 2) healthy adults, 3) reported psychophysiological (thermal comfort, heart rate or core temperature) and/or performance (physical or cognitive) outcomes, 4) written in English, and 5) published before November 6, 2019. A second search for original research articles was performed to identify interventions of relevance but lacking systematic reviews. All identified interventions were independently evaluated by all co-authors on four point scales for effectiveness, cost, feasibility and environmental impact. RESULTS: Following screening, 36 systematic reviews fulfilled the inclusion criteria. The most effective solutions at mitigating occupational heat strain were wearing specialized cooling garments, (physiological) heat acclimation, improving aerobic fitness, cold water immersion, and applying ventilation. Although air-conditioning and cooling garments in ideal settings provide best scores for effectiveness, the limited applicability in certain industrial settings, high economic cost and high environmental impact are drawbacks for these solutions. However, (physiological) acclimatization, planned breaks, shading and optimized clothing properties are attractive alternative solutions when economic and ecological sustainability aspects are included in the overall evaluation. DISCUSSION: Choosing the most effective solution or combinations of methods to mitigate occupational heat strain will be scenario-specific. However, this paper provides a framework for integrating effectiveness, cost, feasibility (indoors and outdoor) and ecologic sustainability to provide occupational health and safety professionals with evidence-based guidelines.

Ad libitum water consumption off-sets the thermal and cardiovascular strain exacerbated by dehydration during a 3-h simulated heatwave.

PURPOSE: To assess whether ad libitum water ingestion of different temperatures is sufficient to prevent dehydration-related exacerbations of thermal and cardiovascular strain, during exposure to conditions representative of a heatwave. METHODS: Twelve participants (mean ± SD; 25 ± 4 years) exercised for 180 min at 3 METs in 40.1 ± 0.6 °C, 40.4 ± 2.1%RH four times: (i) consuming 20 °C water ad libitum (AL20); (ii) consuming 4 °C water ad libitum (AL4); (iii) replacing no fluids (NOFR); (iv) replacing sweat losses (FULLFR). Fluid consumption (FC), dehydration (%DEH), rectal temperature (Tre), rate-pressure product (RPP), forearm blood flow (FBF), mean skin temperature (Tsk), and local sweat rate (LSR) were measured/determined. RESULTS: FC was greater in AL20 (1.30 ± 0.41 L) than AL4 (1.03 ± 0.32 L; P = 0.003). %DEH was lower (P < 0.001) in AL20 (0.11 ± 0.76%), AL4 (0.43 ± 0.64%), and FULLFR (0.01 ± 0.12%) compared to NOFR (1.93 ± 0.28%). %DEH was lower in AL20 than AL4 (P = 0.003). In NOFR, end-trial changes in Tre were greater (P < 0.001) (1.05 ± 0.27 °C) compared to all other trials, but similar among AL20 (0.72 ± 0.30 °C), AL4 (0.76 ± 0.25 °C) and FULLFR (0.74 ± 0.35 °C). End-trial RPP was higher (P < 0.001) in NOFR (12,389 ± 1578 mmHg·bpm) compared to all other trials, but similar among FULLFR (11,067 ± 1292 mmHg·bpm), AL20 (11,214 ± 2078 mmHg·bpm) and AL4 (11,089 ± 1795 mmHg·bpm). No differences in Tsk or LSR were observed among trials, but FBF was lower in NOFR compared to FULLFR (2.84 ± 0.69 vs. 3.52 ± 0.96 ml/100 ml/min; P = 0.029). CONCLUSION: 4 °C or 20 °C ad libitum water ingestion prevented dehydration levels that exacerbate thermal/cardiovascular strain, despite blunted fluid intake with 4 °C water. Higher core temperatures with NOFR are attributed to impaired internal heat distribution secondary to a lower FBF.

Temperature of water ingested before exercise alters the onset of physiological heat loss responses.

This study sought to determine whether the temperature of water ingested before exercise alters the onset threshold and subsequent thermosensitivity of local vasomotor and sudomotor responses after exercise begins. Twenty men [24 (SD 4) yr of age, 75.8 (SD 8.1) kg body mass, 52.3 (SD 7.7) ml·min-1·kg-1 peak O2 consumption (V̇o2peak)] ingested 1.5°C, 37°C, or 50°C water (3.2 ml/kg), rested for 5 min, and then cycled at 50% V̇o2peak for 15 min at 23.0 (SD 0.9) °C and 32 (SD 10) % relative humidity. Mean body temperature (Tb), local sweat rate (LSR), and skin blood flow (SBF) were measured. In a subset of eight men [25 (SD 5) yr of age, 78.6 (SD 8.3) kg body mass, 48.9 (SD 11.1) ml·min-1·kg-1 V̇o2peak], blood pressure was measured and cutaneous vascular conductance (CVC) was determined. The change in Tb was greater at the onset of LSR measurement with ingestion of 1.5°C than 50°C water [ΔTb = 0.19 (SD 0.15) vs. 0.11 (SD 0.12) °C, P = 0.04], but not 37°C water [ΔTb = 0.14 (SD 0.14) °C, P = 0.23], but did not differ between trials for SBF measurement [ΔTb = 0.18 (SD 0.15) °C, 0.11 (SD 0.13) °C, and 0.09 (SD 0.09) °C with 1.5°C, 37°C, and 50°C water, respectively, P = 0.07]. Conversely, the thermosensitivity of LSR and SBF was not different [LSR = 1.11 (SD 0.75), 1.11 (SD 0.75), and 1.34 (SD 1.11) mg·min-1·cm-2·°C-1 with 1.5°C, 37°C, and 50°C ingested water, respectively ( P = 0.46); SBF = 717 (SD 882), 517 (SD 606), and 857 (SD 904) %baseline arbitrary units (AU)/°C with 1.5°C, 37°C, and 50°C ingested water, respectively ( P = 0.95)]. After 15 min of exercise, LSR and SBF were greater with ingestion of 50°C than 1.5°C water [LSR = 0.40 (SD 0.17) vs. 0.31 (SD 0.19) mg·min-1·cm-2 ( P = 0.02); SBF = 407 (SD 149) vs. 279 (SD 117) %baseline AU ( P < 0.001)], but not 37°C water [LSR = 0.50 (SD 0.22) mg·min-1·cm-2; SBF = 324 (SD 169) %baseline AU]. CVC was statistically unaffected [275 (SD 81), 340 (SD 114), and 384 (SD 160) %baseline CVC with 1.5°C, 37°C, and 50°C ingested water, respectively, P = 0.30]. Collectively, these results support the concept that visceral thermoreceptors modify the central drive for thermoeffector responses.

Who's the boss: determining the control pathways of cardiovascular and cellular immune responses to acute stress.

Acute stress responses are known to include increases in heart rate and blood pressure, as well as increases in the number of circulating immune cells, all of which are governed by the autonomic nervous system. This laboratory practical measures cardiovascular and circulating immune cell responses to a passive (cold pressor) and active (mental arithmetic) acute stress task in student participants. The results allow them to examine the different patterns of autonomic response they elicit (approximated by heart rate and blood pressure responses), and knowledge of these responses can then be used to infer the governing autonomic aspect of the increases in circulating immune cells from the results. This activity can be either adapted from teacher-led methods to inquiry, asking students to design the details of the acute stress tasks, or developed by asking students to design a follow-up experiment that could be used to provide direct evidence for their conclusions. Data collected provide a platform for teaching data analysis and interpretation, as well as critical thinking.

Evidence of viscerally-mediated cold-defence thermoeffector responses in man.

KEY POINTS: Visceral thermoreceptors that modify thermoregulatory responses are widely accepted in animal but not human thermoregulation models. Recently, we have provided evidence of viscerally-mediated sweating alterations in humans during exercise brought about by warm and cool fluid ingestion. In the present study, we characterize the modification of shivering and whole-body thermal sensation during cold stress following the administration of a graded thermal stimuli delivered to the stomach via fluid ingestion at 52, 37, 22 and 7°C. Despite no differences in core and skin temperature, fluid ingestion at 52°C rapidly decreased shivering and sensations of cold compared to 37°C, whereas fluid ingestion at 22 and 7°C led to equivalent increases in these responses. Warm and cold fluid ingestion independently modifies cold defence thermoeffector responses, supporting the presence of visceral thermoreceptors in humans. However, the cold-defence thermoeffector response patterns differed from previously identified hot-defence thermoeffectors. ABSTRACT: Sudomotor activity is modified by both warm and cold fluid ingestion during heat stress, independently of differences in core and skin temperatures, suggesting independent viscerally-mediated modification of thermoeffectors. The present study aimed to determine whether visceral thermoreceptors modify shivering responses to cold stress. Ten males (mean ± SD: age 27 ± 5 years; height 1.73 ± 0.06 m, weight 78.4 ± 10.7 kg) underwent whole-body cooling via a water perfusion suit at 5°C, on four occasions, to induce a steady-state shivering response, at which point two aliquots of 1.5 ml kg-1 (SML) and 3.0 ml kg-1 (LRG), separated by 20 min, of water at 7, 22, 37 or 52°C were ingested. Rectal, mean skin and mean body temperature (Tb ), electromyographic activity (EMG), metabolic rate (M) and whole-body thermal sensation on a visual analogue scale (WBTS) ranging from 0 mm (very cold) to 200 mm (very hot) were all measured throughout. Tb was not different between all fluid temperatures following SML fluid ingestion (7°C: 35.7 ± 0.5°C; 22°C: 35.6 ± 0.5°C; 37°C: 35.5 ± 0.4°C; 52°C: 35.5 ± 0.4°C; P = 0.27) or LRG fluid ingestion (7°C: 35.3 ± 0.6°C; 22°C: 35.3 ± 0.5°C; 37°C: 35.2 ± 0.5°C; 52°C: 35.3 ± 0.5°C; P = 0.99). With SML fluid ingestion, greater metabolic rates and cooler thermal sensations were observed with ingestion at 7°C (M: 179 ± 55 W, WBTS: 29 ± 21 mm) compared to 52°C (M: 164 ± 34 W, WBTS: 51 ± 28 mm; all P < 0.05). With LRG ingestion, compared to shivering and thermal sensations with ingestion at 37°C (M: 215 ± 47 W, EMG: 3.9 ± 2.5% MVC, WBTS: 33 ± 2 mm), values were different (all P < 0.05) following ingestion at 7°C (M: 269 ± 77 W, EMG: 5.5 ± 0.9% MVC, WBTS: 14 ± 12 mm), 22°C (M: 270 ± 86 W, EMG: 5.6 ± 1.0% MVC, WBTS: 18 ± 19 mm) and 52°C (M: 179 ± 34 W, EMG: 3.3 ± 2.1% MVC, WBTS: 53 ± 28 mm). In conclusion, fluid ingestion at 52°C decreased shivering and the sensation of coolness, whereas fluid ingestion at 22 and 7°C increased shivering and sensations of coolness to similar levels, independently of core and skin temperature.

Warm hands, cold heart: progressive whole-body cooling increases warm thermosensitivity of human hands and feet in a dose-dependent fashion.

NEW FINDINGS: What is the central question of this study? Investigations on inhibitory/facilitatory modulation of vision, touch and pain show that conditioning stimuli outside the receptive field of testing stimuli modulate the central processing of visual, touch and painful stimuli. We asked whether contextual modulation also exists in human temperature integration. What is the main finding and its importance? Progressive decreases in whole-body mean skin temperature (the conditioning stimulus) significantly increased local thermosensitivity to skin warming but not cooling (the testing stimuli) in a dose-dependent fashion. In resembling the central mechanisms underlying endogenous analgesia, our findings point to the existence of an endogenous thermosensory system in humans that could modulate local skin thermal sensitivity to facilitate thermal behaviour. Although inhibitory/facilitatory central modulation of vision and pain has been investigated, contextual modulation of skin temperature integration has not been explored. Hence, we tested whether progressive decreases in whole-body mean skin temperature (Tsk ; a large conditioning stimulus) alter the magnitude estimation of local warming and cooling stimuli applied to hairy and glabrous skin. On four separate occasions, eight men (27 ± 5 years old) underwent a 30 min whole-body cooling protocol (water-perfused suit; temperature, 5°C), during which a quantitative thermosensory test, consisting of reporting the perceived magnitude of warming and cooling stimuli (±8°C from 30°C baseline) applied to the hand (palm/dorsum) and foot (sole/dorsum), was performed before cooling and every 10 min thereafter. The cooling protocol resulted in large progressive reductions in Tsk [10 min, -3.36°C (95% confidence interval -2.62 to -4.10); 20 min, -5.21°C (-4.47 to -5.95); and 30 min, -6.32°C (-5.58 to -7.05); P < 0.001], with minimal changes (∼0.08°C) in rectal temperature. While thermosensitivity to local skin cooling remained unchanged (P = 0.831), sensitivity to skin warming increased significantly at each level of Tsk for all skin regions [10 min, +4.9% (-1.1 to +11.0); 20 min, +6.1% (+0.1-12.2); and 30 min, +7.9% (+1.9-13.9); P = 0.009]. Linear regression indicated a 1.2% °C-1 increase in warm thermosensitivity with whole-body skin cooling. Overall, large decreases in Tsk significantly facilitated warm but not cold sensory processing of local thermal stimuli, in a dose-dependent fashion. In highlighting a novel feature of human temperature integration, these findings point to the existence of an endogenous thermosensory system that could modulate local skin thermal sensitivity in relationship to whole-body thermal states.

Occupational heat strain in outdoor workers: A comprehensive review and meta-analysis.

The present comprehensive review (i) summarizes the current knowledge on the impacts of occupational heat stress on outdoor workers, (ii) provides a historical background on this issue, (iii) presents a meta-analysis of published data, (iv) explores inter-individual and intra-individual factors, (v) discusses the available heat mitigation strategies, (vi) estimates physical work capacity, labour productivity, and metabolic rate for the year 2030, and (vii) provides an overview of existing policy and legal frameworks on occupational heat exposure. Meta-analytic findings from 38 field studies that involved monitoring 2,409 outdoor workers across 41 jobs in 21 countries suggest that occupational heat stress increases the core (r = 0.44) and skin (r = 0.44) temperatures, as well as the heart rate (r = 0.38) and urine specific gravity (r = 0.13) of outdoor workers (all p < 0.05). Moreover, it diminishes the capacity of outdoor workers for manual labour (r = -0.82; p < 0.001) and is responsible for more than two thirds of the reduction in their metabolic rate. Importantly, our analysis shows that physical work capacity is projected to be highly affected by the ongoing anthropogenic global warming. Nevertheless, the metabolic rate and, therefore, labour productivity are projected to remain at levels higher than the workers' physical work capacity, indicating that people will continue to work more intensely than they should to meet their financial obligations for food and shelter. In this respect, complementary measures targeting self-pacing, hydration, work-rest regimes, ventilated garments, and mechanization can be adopted to protect outdoor workers.

Electric fan use for cooling during hot weather: a biophysical modelling study.

BACKGROUND: In hot weather, electric fans can potentially provide effective cooling for people, with lower greenhouse gas emissions and cost than air conditioning. However, international public health organisations regularly discourage fan use in temperatures higher than 35°C, despite little evidence. We aimed to determine humidity-dependent temperature thresholds at which electric fans would become detrimental in different age groups. METHODS: We used biophysical modelling to determine the upper humidity-dependent temperature thresholds at which fan use would become detrimental (ie, worsen heat stress) for healthy young adults (aged 18-40 years), healthy older adults (aged ≥65 years), and older adults taking anticholinergic medication. We also obtained hourly environmental data for the period Jan 1, 2007, to Dec 31, 2019, for 108 populous cities to determine the number of days fan use would be effective for cooling, standardised to a 31-day hot weather month. We established simplified temperature thresholds for future fan use recommendations on the basis of temperatures below which fan use would never have been detrimental between Jan 1, 2007, and Dec 31, 2019, across all prevailing levels of ambient humidity. FINDINGS: According to our model, fan use would have been beneficial on 30·0 (96·6%) of 31 hot weather days for healthy young adults and 29·4 (94·9%) of 31 hot weather days for both older adults and older adults taking anticholinergic medication between Jan 1, 2007, and Dec 31, 2019. Adherence to the current WHO recommendation of fan use below temperatures of 35°C only, fan use would have been recommended on 27·2 days (87·7%) of 31 hot weather days. According to our simplified thresholds for fan use (at temperatures <39·0°C for healthy young adults, <38·0°C for healthy older adults, and <37·0°C for older adults taking anticholinergic medication), fan use would have been recommended on 29·6 (95·5%) of 31 hot weather days in healthy young adults, 29·4 (94·8%) days in healthy older adults, and 28·8 (93·0%) days in older adults taking anticholinergic medication between Jan 1, 2007, and Dec 31, 2019. INTERPRETATION: Electric fan use, particularly for healthy young adults, would not have worsened heat stress on the majority of study days between 2007 and 2019. Our newly proposed thresholds for fan use provide simple guidelines that improve future heatwave fan use recommendations. FUNDING: None.

Aerobic fitness as a parameter of importance for labour loss in the heat.

OBJECTIVES: To derive an empirical model for the impact of aerobic fitness (maximal oxygen consumption; V̇O2max in mL∙kg-1∙min-1) on physical work capacity (PWC) in the heat. DESIGN: Prospective, repeated measures. METHODS: Total work completed during 1 h of treadmill walking at a fixed heart rate of 130 b∙min-1 was assessed in 19 young adult males across a variety of warm and hot climate types, characterised by wet-bulb globe temperatures (WBGT) ranging from 12 to 40 °C. For data presentation and obtaining initial parameter estimates for modelling, participants were grouped into low (n = 6, 74 trials), moderate (n = 8, 76 trials), and high (n = 5, 29 trials) fitness, with group mean V̇O2max 42, 52, and 64 mL∙kg-1∙min-1, respectively. For the heated conditions (WBGT 18 to 40 °C), we calculated PWC% by expressing total energy expenditure (kJ above resting) in each trial relative to that achieved in a cool reference condition (WBGT = 12 °C = 100% PWC). RESULTS: The relative reduction in energy expenditure (PWC%) caused by heat was significantly smaller by up to 16% for the fit participants compared to those with lower aerobic capacity. V̇O2max also modulated the relationship between sweat rate and body temperature changes to increasing WBGT. Including individual V̇O2max data in the PWC prediction model increased the predicting power by 4%. CONCLUSIONS: Incorporating individual V̇O2max improved the predictive power of the heat stress index WBGT for Physical Work Capacity in the heat. The largest impact of V̇O2max on PWC was observed at a WBGT between 25 and 35 °C.

Proposed framework for forecasting heat-effects on motor-cognitive performance in the Summer Olympics.

Heat strain impairs performance across a broad spectrum of sport disciplines. The impeding effects of hyperthermia and dehydration are often ascribed to compromised cardiovascular and muscular functioning, but expert performance also depends on appropriately tuned sensory, motor and cognitive processes. Considering that hyperthermia has implications for central nervous system (CNS) function and fatigue, it is highly relevant to analyze how heat stress forecasted for the upcoming Olympics may influence athletes. This paper proposes and demonstrates the use of a framework combining expected weather conditions with a heat strain and motor-cognitive model to analyze the impact of heat and associated factors on discipline- and scenario-specific performances during the Tokyo 2021 games. We pinpoint that hyperthermia-induced central fatigue may affect prolonged performances and analyze how hyperthermia may impair complex motor-cognitive performance, especially when accompanied by either moderate dehydration or exposure to severe solar radiation. Interestingly, several short explosive performances may benefit from faster cross-bridge contraction velocities at higher muscle temperatures in sport disciplines with little or no negative heat-effect on CNS fatigue or motor-cognitive performance. In the analyses of scenarios and Olympic sport disciplines, we consider thermal impacts on "motor-cognitive factors" such as decision-making, maximal and fine motor-activation as well as the influence on central fatigue and pacing. From this platform, we also provide perspectives on how athletes and coaches can identify risks for their event and potentially mitigate negative motor-cognitive effects for and optimize performance in the environmental settings projected.

Health vs. wealth: Employer, employee and policy-maker perspectives on occupational heat stress across multiple European industries.

Successful implementation of cooling strategies obviously depends on identifying effective interventions, but in industrial settings, it is equally important to consider feasibility and economic viability. Many cooling interventions are available, but the decision processes affecting adoption by end-users are not well elucidated. We therefore arranged two series of meetings with stakeholders to identify knowledge gaps, receive feedback on proposed cooling interventions, and discuss factors affecting implementation of heat-health interventions. This included four meetings attended by employers, employees, and health and safety officers (n = 41), and three meetings attended primarily by policy makers (n = 74), with feedback obtained via qualitative and quantitative questionnaires and focus group discussions. On a 10-point scale, both employers and employees valued worker safety (9.1 ± 1.8; mean±SD) and health (8.5 ± 1.9) as more important than protecting company profits (6.3 ± 2.3). Of the respondents, 41% were unaware of any cooling strategies at their company and of those who were aware, only 30% thought the interventions were effective. Following presentation of proposed interventions, the respondents rated "facilitated hydration", "optimization of clothing/protective equipment", and "rescheduling of work tasks" as the top-three preferred solutions. The main barriers for adopting cooling interventions were cost, feasibility, employer perceptions, and legislation. In conclusion, preventing negative health and safety effects was deemed to be more important than preventing productivity loss. Regardless of work sector or occupation, both health and wealth were emphasized as important parameters and considered as somewhat interrelated. However, a large fraction of the European worker force lacks information on effective measures to mitigate occupational heat stress. List of abbreviations: OH-Stress: Occupational heat stress; WBGT: Wet Bulb Globe Temperature.

The HEAT-SHIELD project - Perspectives from an inter-sectoral approach to occupational heat stress.

OBJECTIVES: To provide perspectives from the HEAT-SHIELD project (www.heat-shield.eu): a multi-national, inter-sectoral, and cross-disciplinary initiative, incorporating twenty European research institutions, as well as occupational health and industrial partners, on solutions to combat negative health and productivity effects caused by working on a warmer world. METHODS: In this invited review, we focus on the theoretical and methodological advancements developed to combat occupational heat stress during the last five years of operation. RESULTS: We outline how we created climate forecast models to incorporate humidity, wind and solar radiation to the traditional temperature-based climate projections, providing the basis for timely, policy-relevant, industry-specific and individualized information. Further, we summarise the industry-specific guidelines we developed regarding technical and biophysical cooling solutions considering effectiveness, cost, sustainability, and the practical implementation potential in outdoor and indoor settings, in addition to field-testing of selected solutions with time-motion analyses and biophysical evaluations. All recommendations were adjusted following feedback from workshops with employers, employees, safety officers, and adjacent stakeholders such as local or national health policy makers. The cross-scientific approach was also used for providing policy-relevant information based on socioeconomic analyses and identification of vulnerable regions considered to be more relevant for political actions than average continental recommendations and interventions. DISCUSSION: From the HEAT-SHIELD experiences developed within European settings, we discuss how this inter-sectoral approach may be adopted or translated into actionable knowledge across continents where workers and societies are affected by escalating environmental temperatures.

Aluminium salt-based antiperspirant coated prosthesis liners do not suppress local sweating during moderate intensity exercise in hot and temperate conditions.

OBJECTIVE: To determine whether coating prosthesis liners with a 5% aluminium zirconium tetrachlorohydrate antiperspirant solution (AZCH) reduces local sweating on the thigh. DESIGN: Double-blinded counter-balanced crossover design METHODS: Fourteen able-bodied participants (age: 28±5 y; body mass: 73.9±7.9kg, height: 1.73±0.09m; peak oxygen consumption [VO2peak]: 50.7±9.1 mlO2⋅kg-1⋅min-1) simultaneously wore a prosthesis liner on each leg, one treated with AZCH and one untreated, for four days prior to running at 50% of VO2peak for 60min in a temperate (23.7±0.7°C and 42.2±2.6% relative humidity) or hot (34.0±1.6°C and 40.8±6.1% relative humidity) environment. Rectal temperature (Tre) and whole-body sweat rates (WBSR) were measured to characterize thermal strain. Local sweat rate (LSR) was measured bilaterally underneath the liners, continuously, and heat-activated-sweat gland density (HASGD) was measured bilaterally every 15min. RESULTS: In temperate condition, the mean change in Tre was 1.2±0.4°C and WBSR was 723±129g⋅h-1, whereas in the hot condition, change in Tre was 1.2±0.5°C and WBSR was 911±231g⋅h-1. In the temperate condition, AZCH treatment did not alter LSR (treated: 0.50±0.17 mg·cm-2min-1, untreated: 0.50±0.17 mg·cm-2min-1; P=0.87) or HASGD (treated: 54±14 glands·cm-2, untreated 55±14 glands·cm-2; P=0.38). In the hot condition, AZCH treatment paradoxically increased LSR (treated: 0.88±0.38 mg·cm-2min-1, untreated: 0.74±0.28 mg·cm-2min-1; P=0.04) but not HASGD (treated: 52±17 glands·cm-2, untreated: 48±19 glands·cm-2; P=0.77). CONCLUSION: These results indicate coating prosthesis liners with 5% AZCH is ineffective at reducing local sweating.

Prolonged facemask use in the heat worsens dyspnea without compromising motor-cognitive performance.

Background: Within the context of the COVID-19 pandemic, the WHO endorses facemask use to limit aerosol-spreading of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, concerns have been raised regarding facemask-associated dyspnea, thermal distress and self-reported impairment of cognition. Accordingly, we tested how facemask-use affects motor-cognitive performances of relevance for occupational safety. We hypothesized that mask use would affect cognitively dominated performances and thermal discomfort, but not alter whole-body thermal balance. Methods: Eight participants completed a facemask and a barefaced (control) trial, in a counterbalanced order, in 40°C and 20% humidity conditions. Motor-cognitive performance, physiological (rectal, mean skin and local facial temperatures) and perceptual (thermal comfort and dyspnea) measures were assessed at baseline and following 45 min of light work (100 W). Results: Perceived dyspnea was aggravated with prolonged facemask use (p = 0.04), resulting in 36% greater breathlessness compared to control. However, no other differences were observed in motor-cognitive performance, physiological strain, or thermal discomfort. Conclusions: Contradicting negative self-reported impacts of facemask-use, only dyspnea was aggravated in the present study, thereby reinforcing global recommendations of mask use, even in hot environments. (Funded by: European Union's Horizon 2020 research and innovation program under the grant agreement No 668786).