Considerations and opportunities for applying sustainable cooling strategies in heat-vulnerable settings
Aged care homes
Occupants usually have medical conditions and take multiple medications that can collectively reduce heat resilience.1 Behavioural adaptive capacity is often reduced in older adults, particularly if they have less mobility or neurodegenerative diseases such as dementia, and clothing is often chosen according to cultural norms rather than for optimal heat loss. Given the large variability in vulnerability factors among those living in aged care homes, lowering indoor temperatures should be prioritised (panel 2).68 Interventions at the individual level are also considered most important by care managers for heat stress reduction.92
Panel 2
Recommended sustainable cooling strategies during heat extremes and hot weather for heat vulnerable settings
Aged care homes
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Installing rooftop sprinklers, outdoor sunshades protecting common rooms, and heat-reflective window glass, using evaporative coolers, and ensuring adequate natural ventilation, should be prioritised to reduce indoor temperatures68
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Application of ice towels, reducing clothing coverage, and wearing a cotton t-shirt saturated with water56 will provide effective body cooling
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Fans should only be used with parallel self-dousing at air temperatures above 38°C61 due to lower sweat rates with advanced age48,69
Slums
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Substituting construction materials of slum dwellings, such as corrugated iron, with better insulated walls and roofs will reduce oppressively hot indoor daytime temperatures70
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Water that is not sufficiently clean to drink can be applied to the skin with a sponge (as opposed to spray) for self-dousing—evaporation of this water reduces the need to sweat54 and could ultimately blunt thirst
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Other individual level heat coping strategies during the hottest times of the day can include cold water foot immersion, wearing a water-saturated t-shirt, seeking shade in well ventilated areas, doing higher intensity activities at cooler hours, and reducing clothing coverage
Workplaces
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Electric fans can improve manual work performance in most hot conditions,71 but they impair wind-sensitive task performance, and in workplaces containing particulates or gases they might cause eye or respiratory problems; the development of user-controlled chairs with built-in low-energy fans might provide a safer alternative72
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Extra breaks should be given in relatively cool areas with access to water for drinking and self-dousing; indoors, well ventilated rooms can be used, whereas outdoors, temporary rest stations can be created with portable parasols and sun tents;73 work shifts can be adjusted to avoid the hottest hours, or midday so-called siestas in cooler environments can be taken to avoid peak temperatures74
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Hydration monitoring via urine colour and volume can be used, as it is simple and effective75
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Industries with scarce supplies of clean water access (eg, agriculture), should provide workers with methods for carrying water (eg, backpacks containing water bladders),73 periodically bring water to employees, or establish water caches around the work area and access to clean lavatory facilities76
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Very cold water and iced drinks have small and transient cooling effect during work65 and are less palatable resulting in less consumption; water temperature for workers should ideally be maintained at about 10°C77
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Where whole-body protection (eg, against chemicals) is not required, ventilation patches in clothing can be used in less exposed areas, such as the groin, underarms, inside the elbows, and behind the knees; outdoor workers should wear long, loose-fitting, lightweight, breathable clothing, light in colour or with reflective fabrics
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For jobs requiring fully encapsulated protective clothing, phase-change materials or cooling systems with compressed cool air can be used but are expensive and carry a greater environmental impact78
Schools
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In playgrounds, shading ground materials and structures with trees and sails improves children's thermal comfort79 and decreases surface temperatures;80 adequate wind flow through appropriate landscape design supports sweat evaporation and evapotranspiration from grass and trees81
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In classrooms, body cooling can be achieved by reducing radiant influx and improving convective airflow with fans; active hydration policies (eg, allowing water bottles on desks throughout the day); water spray bottles for self-dousing can be effective but potentially impractical
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Flexibility in school uniform dress codes (eg, taking off ties, opening shirts) should be allowed
Mass gatherings
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Education from religious and community leaders is needed to improve compliance with protective behaviours during these events
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Access to sufficient drinking water and shaded cooling areas should be prioritised for all mass gatherings in hot weather82
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Adequate availability of heat prevention information (including signs with symptoms of heat illness, prevention, and treatment guidelines) should be provided
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Outdoor misting fans can be used83
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Scoring systems can also be helpful to predict the medical staff required for mass events84(Continues on next page)(Panel 2 continued from previous page)
Refugee camps
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Breathable tents
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Information on hygienic water and food preparation practices to prevent food and water-borne diseases
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Female medical aid workers should be available to check on female refugees85
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When non-potable, but otherwise safe, water is present, self-dousing can reduce sweating requirements, thereby slowing dehydration54
Sport
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Playing surfaces can be used that minimise heat retention and emitted radiation,86 whereas playing areas can be built and oriented to permit sufficient natural ventilation and include easily accessible shelters that provide shade
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Precooling (before exercise) with cold water and crushed ice ingestion or immersion can reduce core temperature;87 however, body temperature then rises quickly when exercise commences, so any benefits of precooling are transient88
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Precooling and percooling (during exercise) with ice vests, cold water ingestion, and the application of cooling packs, especially to the neck, can improve exercise performance 89
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For sports with short but frequent breaks (eg, tennis), application of ice towels reduces physiological heat strain57
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For sports with near-continuous play separated by a prolonged midpoint break (eg, Association Football), self-dousing the skin or clothing, or misting fans reduce physiological heat strain;90 extending halftime breaks, even if participants remain in the heat, reduces body temperature far more effectively than adding shorter (1–3 min) so-called quarter-time breaks90
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A 70 kg moderately fit person working at 50% of their maximum capacity at 35°C must exercise 1–1·5 h to reach this dehydration threshold; ad libitum water ingestion replaces about 50% of sweat losses during exercise in the heat,91 so this time is approximately doubled if water is readily available at all times
Slums
Construction materials of slum dwellings such as corrugated iron substantially contribute to oppressively hot indoor daytime temperatures (panel 2).70 Poor water quality and sanitation remains commonplace in slums; therefore, heat can secondarily increase the risk of waterborne diseases,70 particularly given that the leading recommendation advocated by public health authorities is to drink water during heat extremes and hot weather. If point-of-use decontamination methods, such as filtering through charcoal, do not clean water sufficiently for drinking, water might still be treated to be safe enough to be applied to the skin.
Workplaces
Any cooling solutions in occupational settings should not interfere with the optimal completion of work tasks or exacerbate other health risks.78,93 Workers often begin a shift dehydrated and maintain a depleted hydration status throughout the day.94 Female workers might be reluctant to hydrate, trying to avoid using a toilet altogether due to unhygienic or absence of facilities.76 Male workers older than 60 years also tend to ration drinks, worried about requirements for frequent toilet breaks. Personal protective equipment and clothing that reduces heat loss must often be worn in many workplaces. Outdoor workers also need to balance heat loss and ultraviolet protection requirements. Some jobs require fully encapsulated protective clothing (eg, asbestos removal, firefighters), therefore internal cooling systems are required. Limiting exposure time in such clothing and integrating other individual level cooling strategies is advisable (panel 2).62,78,93
Schools
In playgrounds, exposure to direct solar radiation and hot surfaces presents the greatest heat-related health risks. In classrooms, school building design requirements restrict cooling options. Individual level cooling strategies should be simple to implement without disrupting the learning environment. Opportunities for cooling by introducing flexibility in school uniform dress codes and recess times should also be considered (panel 2).
Mass gatherings
Heat exhaustion and dehydration are the most common medical presentations at mass gatherings in hot weather.82 Over the next 15 years, the Hajj pilgrimage (Mecca, Saudi Arabia), with more than 7 million annual participants, will take place during months with mean daily high temperatures of more than 40°C. Risk of heat-related illness is exacerbated by age, comorbidities such as diabetes,95 and reluctance among some people to adopt hydration and other preventative practices (eg, umbrellas) due to misconceptions about compatibility with Hajj rituals.96
Refugee camps
Similar challenges to mass gatherings present themselves at refugee camps, but with shorter time to prepare for hot weather and heat extremes, fewer trained personnel, and less resources and electricity.85,97 Women in refugee camps can be at a greater risk of heat-related illness due to segregation in insulative tents, and further restrictions to food, water, and medical care.85
Sport
Very hot, artificial, playing surfaces and local microclimates created by surrounding structures are a leading contributor to the elevated risk of heat stress of people playing sport.86 Individual level cooling strategies to mitigate risk of heat stress during hot weather can be applied before or during exercise. The effectiveness during exercise is dependent on how a particular sport is structured, and thus the opportunities to intervene. Some sports consist of short but frequent breaks (eg, tennis) during which aggressive cooling manoeuvres can be quickly applied and removed (panel 2).57 Other sports have near-continuous play separated by a prolonged midpoint break (eg, Association Football). Sweat losses of more than 2% of total bodyweight exacerbates the risk of exertional heat illness98,99 and should be avoided. On the basis of a consensus statement from the American College of Sports Medicine,100 providing facilities for fast, emergency body cooling (eg, ice baths) during hot weather events is a proven lifesaving safety feature. Allowing sports participants to progressively adapt physiologically to the heat is an effective way to reduce heat strain. For maximal adaptations to occur, daily exposures to summer weather with graded increases in exercise intensity, and if necessary, modifications to protective equipment and clothing worn, are required across the course of 1–2 weeks.101 Ultimately the suspension or cancellation of play can be mandated if the risk is deemed sufficiently high. The amount of heat stress judged as acceptable is highly dependent on the level of competition and profile of the competitor (eg, highly trained professional adult vs recreational junior). Scheduling of professional sports is strongly driven by commercial interests, including broadcasting rights. At the community level, there might be a reluctance, or insufficient flexibility, to reschedule matches due to a restricted availability of playing facilities.
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Avatar 2: I’m in. Stick around—we’ll compare heat with other weather and what that means for leaders.
Avatar 1: Hey, seriously, gracias a montón for being here today — really means a lot!
Avatar 2: Yeah, thanks so much for sticking with us! ¡Hasta luego, everybody! Catch you all next time
Avatar 1: stay cool out there and bye for now
Avatar 2 : bye bye
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