Electric fans: A potential stay-at-home cooling strategy during the COVID-19 pandemic this summer?

A critical review of the effectiveness of electric fans as a personal cooling intervention in hot weather and heatwaves

Health agencies worldwide have historically cautioned that electric fans accelerate body-heat gain during hot weather and heatwaves (typically in air temperatures ≥35°C). However, guidance published since 2021 has suggested that fans can still cool the body in air temperatures up to 40°C by facilitating sweat evaporation, and therefore are an inexpensive yet sustainable alternative to air conditioning. In a critical analysis of the reports cited to support this claim, we found that although fan use improves sweat evaporation, these benefits are of insufficient magnitude to exert meaningful reductions in body core temperature in air temperatures exceeding 35°C. Health agencies should continue to advise against fan use in air temperatures higher than 35°C, especially for people with compromised sweating capacity (eg, adults aged 65 years or older). Improving access to ambient cooling strategies (eg, air conditioning or evaporative coolers) and minimising their economic and environmental costs through policy initiatives, efficient cooling technology, and combined use of low-cost personal interventions (eg, skin wetting or fan use) are crucial for climate adaptation.

Optimal low-cost cooling strategies for infant strollers during hot weather

The current study aimed to identity the optimal low-cost stroller cooling strategies for use in hot and moderately humid summer weather. A commercially available stroller was instrumented to assess the key parameters of the thermal environment. The cooling efficacy of eight different stroller configurations was examined in a counterbalanced order across 16 hot summer days (air temperature (Ta) = 33.3 ± 4.1 °C; relative humidity = 36.7 ± 15%; black globe temperature = 43.9 ± 4.6 °C). Compared with a standard-practice stroller configuration, combining a moist muslin draping with a battery-operated clip-on fan provided optimal in-stroller cooling, reducing the end-trial air temperature by 4.7 °C and the wet bulb globe temperature (WBGT) by 1.4 °C. In contrast, in-stroller temperatures were substantially increased by draping a dry muslin (Ta = +2.6 °C; WBGT = +0.9 °C) or flannelette (Ta = +3.7 °C; WBGT = +1.4 °C) cloth over the stroller carriage. These findings provide empirical evidence which may inform guidance aimed at protecting infants during hot weather.Practitioner summary: This study examined the efficacy of traditional and novel stroller cooling strategies for use in hot and moderately humid weather. Covering the carriage with a dry muslin cloth substantially increased stroller temperatures and should be avoided. Evaporative cooling methods reduced in-stroller temperatures. A moist muslin cloth draping combined with a fan provided optimal stroller cooling.

Indoor overheating influences self-reported symptoms and mood-state in older adults during a simulated heatwave: Effects of mid-day cooling centre use

Public health agencies recommend that older adults without home air-conditioning visit cooling centres to mitigate physiological strain from high ambient temperatures during heat waves. However, there is little evidence regarding their influence on self-reported environmental symptoms and mood-state after returning to the heat.

METHODS

Forty adults (64-79 years) underwent a daylong laboratory-based indoor overheating simulation (9-hours, heat index: 37 °C) with (cooling, n = 20) or without (control, n = 20) a 2-hour air-conditioning intervention (hours 5-6). Mean skin and core temperature areas under the curve (AUC, hours 0-9) were used to assess cumulative thermal strain. Group differences in total symptom scores and subjective heat illness (68-item environmental symptoms questionnaire) as well as total mood disturbance and energy index (40-item profile of mood states questionnaire) were evaluated at end-heating (adjusted for pre-exposure scores).

RESULTS

Cooling reduced mean skin and core temperature AUCs by 4.0 [0.1, 0.8] and 1.6 [0.4, 2.8] °C·hour compared to control (both p < 0.048). However, at end-heating neither mean skin nor core temperatures differed between groups (both p > 0.999). Total symptom scores and subjective heat illness were 0.58-fold [0.44, 0.77] and 0.56-fold [0.40, 0.78] lower in the cooling compared to control group (both p < 0.001). Mood disturbance was 0.91-fold [0.83, 0.99] lower for cooling than control (p = 0.036), although energy index was not different between groups (p = 0.141).

CONCLUSION

Cooling centres can have sustained positive effects on perceived thermal strain and mood-state in older adults after returning to the heat. However, continued vigilance and use of appropriate countermeasures to mitigate physiological strain from indoor overheating should be encouraged as body temperatures can rapidly return to pre-cooling levels.

Effect of voluntary electric fan use on autonomic and perceptual responses to lower leg passive heating in humans

This study investigated the efficacy of voluntary fan utilization on autonomic thermoeffector responses and thermal perceptions during passive heating by lower leg immersion (42 °C) in a 27 °C ambient temperature, 50% relative humidity. Fourteen young healthy adults (8 females) were recruited for this study where they underwent two trials with (Fan) and without an electric fan (No fan) during 50 min of passive heat stress. The skin temperature on forearm and abdomen was lower in Fan than in No fan (all p < 0.02), and the local skin temperature on the chest, and mean skin temperature were significantly lower in Fan than in No fan in the final 20 min (mean value of mean skin temperature: 34.77(0.15) °C vs 35.11(0.12) °C, respectively, all p < 0.03), whilst the rectal temperature was not different between trials (37.11(0.23) °C vs 37.08(0.27) °C, p = 0.78). The sensitivity of local sweat rate (LSR) with the increase of mean body temperature on the chest and forearm was significantly lower in Fan than No fan trials (all p < 0.02). The sum value of thermal sensation was lower and wetness was higher in Fan than in No fan in the final 25 min (thermal sensation: 7.50 (1.25) vs 5.00 (3.06), wetness: -6.57 (2.31) vs -5.21 (2.46), all p<0.03) whilst thermal discomfort did not differ significantly between trials (p = 0.12). The voluntary use of an electric fan attenuates the autonomic thermoeffector response, such as sweating, and influences thermal sensation and wetness but did not affect core temperature and thermal discomfort during lower leg immersion.

The Intersection of the COVID-19 Pandemic and the 2021 Heat Dome in Canadian Digital News Media: A Content Analysis

During the 2021 Heat Dome, 619 people in British Columbia died due to the heat. This public health disaster was made worse by the ongoing COVID-19 pandemic. Few studies have explored the intersection of heat with COVID-19, and none in Canada. Considering that climate change is expected to increase the frequency of extreme heat events, it is important to improve our understanding of intersecting public health crises. Thus, this study aimed to explore media-based public health communication in Canada during the COVID-19 pandemic and the 2021 Heat Dome. A qualitative content analysis was conducted on a subset of media articles (n = 520) related to the COVID-19 pandemic which were identified through a previous media analysis on the 2021 Heat Dome (n = 2909). Many of the articles provided conflicting health messages that may have confused the public about which health protective actions to take. The articles also showed how the COVID-19 pandemic may have exacerbated the health impacts of the 2021 Heat Dome, as pandemic-related public health measures may have deterred people away from protecting themselves from heat. This study, which provides novel insight into the prioritization of public health messaging when an extreme heat event occurs concurrently with a pandemic, supports the need for consistent heat health guidance.

Temperature-Humidity-Dependent Wind Effects on Physiological Heat Strain of Moderately Exercising Individuals Reproduced by the Universal Thermal Climate Index (UTCI)

Increasing wind speed alleviates physiological heat strain; however, health policies have advised against using ventilators or fans under heat wave conditions with air temperatures above the typical skin temperature of 35 °C. Recent research, mostly with sedentary participants, suggests mitigating the effects of wind at even higher temperatures, depending on the humidity level. Our study aimed at exploring and quantifying whether such results are transferable to moderate exercise levels, and whether the Universal Thermal Climate Index (UTCI) reproduces those effects. We measured heart rates, core and skin temperatures, and sweat rates in 198 laboratory experiments completed by five young, semi-nude, heat-acclimated, moderately exercising males walking the treadmill at 4 km/h on the level for three hours under widely varying temperature-humidity combinations and two wind conditions. We quantified the cooling effect of increasing the wind speed from 0.3 to 2 m/s by fitting generalized additive models predicting the physiological heat stress responses depending on ambient temperature, humidity, and wind speed. We then compared the observed wind effects to the assessment performed by the UTCI. Increasing the wind speed lowered the physiological heat strain for air temperatures below 35 °C, but also for higher temperatures with humidity levels above 2 kPa water vapor pressure concerning heart rate and core temperature, and 3 kPa concerning skin temperature and sweat rate, respectively. The UTCI assessment of wind effects correlated positively with the observed changes in physiological responses, showing the closest agreement (r = 0.9) for skin temperature and sweat rate, where wind is known for elevating the relevant convective and evaporative heat transfer. These results demonstrate the potential of the UTCI for adequately assessing sustainable strategies for heat stress mitigation involving fans or ventilators, depending on temperature and humidity, for moderately exercising individuals.

Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices

Increasing air movement can alleviate or exacerbate occupational heat strain, but the impact is not well defined across a wide range of hot environments, with different clothing levels. Therefore, we combined a large empirical study with a physical model of human heat transfer to determine the climates where increased air movement (with electric fans) provides effective body cooling. The model allowed us to generate practical advice using a high-resolution matrix of temperature and humidity. The empirical study involved a total of 300 1-h work trials in a variety of environments (35, 40, 45, and 50 °C, with 20 up to 80% relative humidity) with and without simulated wind (3.5 vs 0.2 m∙s^-1), and wearing either minimal clothing or a full body work coverall. Our data provides compelling evidence that the impact of fans is strongly determined by air temperature and humidity. When air temperature is ≥ 35 °C, fans are ineffective and potentially harmful when relative humidity is below 50%. Our simulated data also show the climates where high wind/fans are beneficial or harmful, considering heat acclimation, age, and wind speed. Using unified weather indices, the impact of air movement is well captured by the universal thermal climate index, but not by wet-bulb globe temperature and aspirated wet-bulb temperature. Overall, the data from this study can inform new guidance for major public and occupational health agencies, potentially maintaining health and productivity in a warming climate.

Urban-Rural Partnership Framework to Enhance Food-Energy-Water Security in the Post-COVID-19 Era

Food, energy, and water (collectively referred to as 'FEW') security forms the key to human survival as well as socioeconomic development. However, the security of these basic resources is increasingly threatened due to growing demand. Beyond the widespread implications on public health, Coronavirus disease (COVID-19) has further raised additional challenges for FEW security, particularly for urban populations, as they mainly outsource their FEW demands from rural areas outside their physical boundaries. In light of that, this study reviews existing literature on FEW security to highlight the growing relevance of urban-rural linkages for realizing FEW security, especially against the backdrop of the COVID-19 pandemic. To achieve this, relevant research documents have been identified through Elsevier's Scopus database and other sources (by applying search equations). The authors have accordingly underlined the necessity of shifting the conventional urban-centric approach to city region-centric development planning for the post-COVID-19 era. To this end, a framework has been suggested for translating physical urban-rural linkages to a partnership enhancing a collective response. The major elements of this framework are the conceptualization of national-level policies to support urban-rural linkages. The framework can play the role of a science-policy-action interface to redesign the FEW system in city regions.

The 2021 report of the Lancet Countdown on health and climate change: code red for a healthy future

The Lancet Countdown is an international collaboration that independently monitors the health consequences of a changing climate. Publishing updated, new, and improved indicators each year, the Lancet Countdown represents the consensus of leading researchers from 43 academic institutions and UN agencies. The 44 indicators of this report expose an unabated rise in the health impacts of climate change and the current health consequences of the delayed and inconsistent response of countries around the globe—providing a clear imperative for accelerated action that puts the health of people and planet above all else.

The 2021 report coincides with the UN Framework Convention on Climate Change 26th Conference of the Parties (COP26), at which countries are facing pressure to realise the ambition of the Paris Agreement to keep the global average temperature rise to 1·5°C and to mobilise the financial resources required for all countries to have an effective climate response. These negotiations unfold in the context of the COVID-19 pandemic—a global health crisis that has claimed millions of lives, affected livelihoods and communities around the globe, and exposed deep fissures and inequities in the world’s capacity to cope with, and respond to, health emergencies. Yet, in its response to both crises, the world is faced with an unprecedented opportunity to ensure a healthy future for all.

Heat Safety in the Workplace: Modified Delphi Consensus to Establish Strategies and Resources to Protect the US Workers

The purpose of this consensus document was to develop feasible, evidence-based occupational heat safety recommendations to protect the US workers that experience heat stress. Heat safety recommendations were created to protect worker health and to avoid productivity losses associated with occupational heat stress. Recommendations were tailored to be utilized by safety managers, industrial hygienists, and the employers who bear responsibility for implementing heat safety plans. An interdisciplinary roundtable comprised of 51 experts was assembled to create a narrative review summarizing current data and gaps in knowledge within eight heat safety topics: (a) heat hygiene, (b) hydration, (c) heat acclimatization, (d) environmental monitoring, (e) physiological monitoring, (f) body cooling, (g) textiles and personal protective gear, and (h) emergency action plan implementation. The consensus-based recommendations for each topic were created using the Delphi method and evaluated based on scientific evidence, feasibility, and clarity. The current document presents 40 occupational heat safety recommendations across all eight topics. Establishing these recommendations will help organizations and employers create effective heat safety plans for their workplaces, address factors that limit the implementation of heat safety best-practices and protect worker health and productivity.

The water-energy-food nexus and COVID-19: Towards a systematization of impacts and responses

The COVID-19 pandemic offers an opportunity to examine the impacts of system-wide crises on key supply sectors such as water, energy and food. These sectors are becoming increasingly interlinked in environmental policy-making and with regard to achieving supply security. There is a pressing need for a systematization of impacts and responses beyond individual disruptions. This paper provides a holistic assessment of the implications of COVID-19 on the water-energy-food (WEF) nexus. First, it integrates the academic literature related to single cases and disruptions to provide a broader view of COVID-19 demand- and supply-side disruptions and immediate effects. Then, the major, long-term impact categories of medicalization/hygienization, (re)localization of production, and demand fluctuations are highlighted. These impacts result in priority cross-links such as irrigation, energy requirements for local food production, energy use for water and wastewater treatment, or water for energy use. Finally, sector-level insights on impacts and responses are provided, drawing from illustrative cases. The analysis of impacts of COVID-19 on the WEF nexus reflects heterogeneous experiences of short-term adaptations, and highlights the revaluation of the water-food-trade nexus. Revived debates on food sufficiency can benefit from green applications to minimize expected trade-offs. The current crisis also reveals some gaps in the WEF nexus debates with regard to the lack of risk-based perspectives and the need for a better consideration of spatial aspects in resource integration. Regarding resource-security issues in the WEF nexus, the COVID-19 stress test boosts debates concerning the adequacy of the production value chains (e.g., contingency and storage, diversification, and self-sufficiency) and the value of cross-border integration (e.g., trade, globalization, and aid).

The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises

TRANSLATIONS

For the Chinese, French, German, and Spanish translations of the abstract see Supplementary Materials section.