Heat Stress Management Research Articles

376 Awardee Talk: Consequences of Heat Stress During Late Gestation for the Dairy Cow and Her Calf

Abstract As global temperatures continue to rise, heat stress emerges as a growing threat to animal productivity and well-being. Because of their high feed intake and metabolic heat production, dairy cows are particularly vulnerable to heat stress and the complications of that environmental insult. A significant knowledge base exists around the impact of heat stress during lactation, but more recent emphasis about impacts on the dry cow, and by extension on the developing fetus, have yielded new insights to inform management of heat stress throughout the production cycle. Heat stress at dry-off slows involution and reduces mammary cell proliferation as parturition approaches. Immune responses, both innate and acquired, are reduced with heat stress and can persist into lactation. Calves whose dams experience heat stress late in gestation have lower birthweights, poorer passive transfer and altered carbohydrate metabolism relative to calves from cooled dams. Calves from heat-stressed dams leave the herd at a higher rate before puberty compared with those from cooled dams, and thus fewer complete the first lactation. More importantly, in utero heat stress causes epigenetic changes in methylation patterns of liver and mammary tissue, and those differences are associated with yield reductions that are transferred through at least two generations, producing a drag on animal performance long after the initial in utero insult. Therefore, appropriate management of heat stress in the dry cow is critical to optimize performance of the cow and calf.

The importance of wetland margin microhabitat mosaics; the case of shorebirds and thermoregulation

Abstract Wetlands, and the species that rely upon them, are under significant threat world‐wide, with wetlands often being completely removed or drastically altered. Successful wetland management requires an understanding of the interactions between wetland species and the microhabitats they use. The use of microhabitats for thermoregulation in wetland species is poorly studied, though anthropogenic influence on wetlands can reduce the diversity of microhabitats and thus the thermoregulatory options for animals. At high ambient temperatures birds may use the water‐logged wetland margins to help with thermoregulation, and are often observed roosting in the sitting position within this microhabitat. However, whether sitting on the wet substrate helps in thermoregulation is unknown. In this study, we tested whether birds selectively use microhabitats across temperatures by conducting field observations of nine species of shorebirds. We use comparative analysis to determine whether birds roost more on wet substrate in the sitting posture, that is, ‘wet‐sitting’, at high ambient temperatures. We found substrate type across the wetland margins to be important in shorebird thermoregulation, with the time spent sitting being significantly mediated by the substrate on which the bird roosted. Individuals tended to sit on bare, wet ground much more under high ambient temperatures compared with low ambient temperatures. Vegetation on the other hand was used similarly across temperatures, and likely does not provide the same thermoregulatory benefits. By roosting on wet substrate at high ambient temperatures, birds may increase the potential for heat dissipation across the uninsulated legs, as water‐logged wetland margins are known to remain cooler than the ambient temperature or vegetated microhabitats under hot climatic conditions. Synthesis and applications. Wetland creation and management requires an understanding of the functional significance of such microhabitats, not only for foraging and breeding, but also for roosting. We demonstrate that managing wetland margins is likely important in minimising heat stress in birds, with our findings emphasising the importance of maintaining open spaces in habitat mosaics for birds to use for thermoregulation. The ability of wetland species to manage heat stress is becoming exceedingly important as they are threatened by both decreased wetland availability and increasing ambient temperatures under climate change.

Climate Warming and Occupational Heat and Hot Environment Standards in Thailand.

BackgroundDuring the period 2001 to 2016, the maximum temperatures in Thailand rose from 38–41oC to 42–44oC. The current occupational heat exposure standard of Thailand issued in 2006 is based on wet bulb globe temperature (WBGT) defined for three workload levels without a work–rest regimen. This study examined whether the present standard still protects most workers.MethodsThe sample comprised 168 heat acclimatized workers (90 in construction sites, 78 in foundries). Heart rate and auditory canal temperature were recorded continuously for 2 hours. Workplace WBGT, relative humidity, and wind velocity were monitored, and the participants' workloads were estimated. Heat-related symptoms and signs were collected by a questionnaire.ResultsOnly 55% of the participants worked in workplaces complying with the heat standard. Of them, 79% had auditory canal temperature ≤ 38.5oC, compared with only 58% in noncompliant workplaces. 18% and 43% of the workers in compliant and noncompliant workplaces, respectively, had symptoms from heat stress, the trend being similar across all workload levels. An increase of one degree (C) in WBGT was associated with a 1.85-fold increase (95% confidence interval: 1.44–2.48) in odds for having symptoms.ConclusionCompliance with the current occupational heat standard protects 4/5 of the workers, whereas noncompliance reduces this proportion to one half. The reasons for noncompliance include the gaps and ambiguities in the law. The law should specify work/rest schedules; outdoor work should be identified as an occupational heat hazard; and the staff should include occupational personnel to manage heat stress in establishments involving heat exposure.

Nanoemulsion seed coating for heat stress management in soybean

An experiment was conducted to access the effect of methyl cellulose nanoemulsion seed coating in soybean (JS-93-05) against heat stress. The nanoemulsion was prepared by using methyl cellulose, vitamin E and tween 80 (in the form of oil in water) with the help of high energy homogenizer. The properties of nanoemulsion were characterised by using Particle size analyzer. (PSA), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). Soybean seeds e coated with nanoemulsion @ 20ml/kg and kept in plant growth chamber where the temperature and relative humidity were maintained at 400C and 50% for a duration of 0, 3, 5, 7, 9, 11 and 13 days and simultaneously seed quality was determined. The results demonstrate that nanoemulsion coated seeds recorded higher rate of germination, speed of emergence, seedling length, vigour index and root volume compared to uncoated seeds under high temperature stress condition.

Temperature- and pH-Responsive Star Polymers as Nanocarriers with Potential for in Vivo Agrochemical Delivery.

Climate change is increasing the severity and length of heat waves. Heat stress limits crop productivity and can make plants more sensitive to other biotic and abiotic stresses. New methods for managing heat stress are needed. Herein, we have developed ∼30 nm diameter poly(acrylic acid)-block-poly(N-isopropylacrylamide) (PAA-b-PNIPAm) star polymers with varying block ratios for temperature-programmed release of a model antimicrobial agent (crystal violet, CV) at plant-relevant pH. Hyperspectral-Enhanced Dark field Microscopy was used to investigate star polymer-leaf interactions and route of entrance. The majority of loaded star polymers entered plant leaves through cuticular and epidermis penetration when applied with the adjuvant Silwet L-77. Up to 43 wt % of star polymers (20 μL at 200 mg L-1 polymer concentration) applied onto tomato (Solanum lycopersicum) leaves translocated to other plant compartments (younger and older shoots, stem, and root) over 3 days. Without Silwet L-77, the star polymers penetrated the cuticle, but mainly accumulated at the epidermis cell layer. The degree of the star polymer temperature responsiveness for CV release in vitro in the range of 20 to 40 °C depends on pH and the ratio of the PAA to PNIPAm blocks. Temperature-responsive release of CV was also observed in vivo in tomato leaves. These results underline the potential for PAA-b-PNIPAm star polymers to provide efficient and temperature-programmed delivery of cationic agrochemicals into plants for protection against heat stress.

Management of Heat Stress in Tomato Seedlings under Arid and Semi-Arid Regions: A Review

The production of protected cultivation of vegetables could be considered a sustainable solution in arid and semi-arid regions. These regions already suffer from the raising temperature due to the global warming, which represents a great challenge facing our universe nowadays. Hence, the production of vegetables under greenhouse system during the high temperatures may be considered a serious problem in these arid zones due to heat stress. In greenhouses, the production of tomato seedlings should avoid the high temperature stress in particular in arid and semi-arid in summer. The heat stress may cause a lot of troubles for the tomato seedlings in greenhouses in summer starting with the photosynthetic rate, and the metabolism processes in seedlings and in turn the growth and development of these seedlings. Although studies have recognized heat stress on tomato seedlings, research has yet to systematically investigate the effect of heat stress on tomato seedlings in greenhouse in summer under arid and semi-arid regions particularly in developed countries, which their greenhouses have not any climate controllers. Therefore, the management of tomato seedlings may need to address the production problems caused by heat stress in greenhouse conditions particularly in arid and semi-arid zones

Effects of air-perfused rucksack on physiological and perceptual strain during low-intensity exercise in a hot environment

ABSTRACT The upcoming Tokyo Olympic and Paralympic Games may be held amid extremely high wet-bulb globe temperature conditions. Many studies have focused on countermeasures to prevent the reduction in exercise performance in the heat. However, cooling strategies for managing heat stress of staff and spectators remain poorly understood. The present study investigated the effects of a lightweight fan cooling device, namely a commercially available air-perfused rucksack, on physiological and perceptual responses during low-intensity exercise in a hot environment. Ten males walked (5.5 km/h, 2.0% gradient) for 60 min in hot conditions (35°C, 50% relative humidity). All participants performed two trials with and without the air-perfused rucksack, respectively. Air was blown onto the upper back and neck via two fans attached on either side of the rucksack. Rectal temperature, neck skin temperature, heart rate, and physiological strain index were significantly lower during walking (P < 0.05) with the rucksack. Additionally, the ratings of perceived exertion, thermal sensation, and thermal comfort were significantly lower (P < 0.05) with the rucksack. These data suggest that the air-perfused rucksack may be effective for managing heat stress of staff and spectators at the Tokyo Olympic and Paralympic Games. Abbreviations CON: control trial; ES: effect sizes; FAN: fan cooling trial; HR: heart rate; mTsk: mean skin temperature; pre: pre-exercise; PSI: physiological strain index; RPE: rating of perceived exertion; SD: standard deviation; TC: thermal comfort; Tneck: neck skin temperature; Tre: rectal temperature; TS: thermal sensation

Heat Stress Effects in Fruit Crops

Heat stress is one of the most ominous abiotic factors which limit the productivity and quality thereby resulting in to huge economic losses. High temperature affects the morphological, anatomical and physiological and biochemical changes in plant system. The success in overcoming heat stress is limited owing to poor knowledge of heat stress during critical stages of fruit crops. There is urgent need to improve heat stress tolerance by using traditional breeding and transgenic approach. In this paper, we have discuss the effect of heat stress and possible management techniques viz., selection of fruit crops, cultivars, rootstocks, canopy management, irrigation, nutrient management, mulching, growth regulator and use of bagging and film spray etc. which can be used to alleviate heat stress in fruit crops.

Managing Heat Stress In Dairy Facilities

Heat stress can have a dramatic impact on milk production and reproduction on commercial dairies. The impact of heat stress can be minimized by improving water availability, providing shade in the housing areas and holding pen, reducing walking distance, reducing time in the holding pen, improving holding pen ventilation, adding holding pen cooling and exit lane cooling, improving ventilation in cow housing areas (freestalls), cooling close-up cows (3 weeks prior to calving), cooling fresh cows and early lactation cows, and cooling mid and late lactation cows. Dairy cattle can be cooled by providing a cooler environment (cooling the air) or by soaking the cows and evaporating water off her skin surface (cooling the cow). Using evaporative cooling to cool the air works in climates with low relative humidity. Evaporating water off the skin surface of the cow to cool the cow will be beneficial in all climates.

浅谈沙特阿美项目施工现场热应激管理

浅谈沙特阿美项目施工现场热应激管理

The nature and scale of the response to climate change will determine the human health for centuries to come in China

Climate change would pose a range of threat to human health both directly and indirectly. The direct adverse effects of climate change to human health include increased frequency of heatwaves, storms, floods, forest fire and drought. The indirect effects usually mediate through impacts on environmental conditions and ecosystems (e.g., air pollution, food insecurity and under-nutrition, and changing patterns of disease), economies, and social structure (e.g., displacement, migration and conflict). To map out the impacts that climate change is having on human health, and the health consequences of the global policy response, the 2015 <italic>Lancet </italic>Commission on Health and Climate Change and the<italic> Lancet</italic> Countdown: tracking progress on health and climate change has been initiated, with strong collaboration of world-class expertise from multiple disciplines and leading academic institutions around the world. The 2018 report of the <italic>Lancet</italic> Countdown on health and climate change tracks 41 indicators across five domains: Climate change impacts, exposures, and vulnerability; adaptation, planning, and resilience for health; mitigation actions and health co-benefits; finance and economics; and public and political engagement. The report warns that a lack of progress in reducing emissions and building adaptive capacity threatens both human lives and the viability of the national health systems they depend on, with the potential to disrupt core public health infrastructure and overwhelm health services. Therefore, the nature and scale of the response to climate change will be the determining factor in shaping the health of nations for centuries to come. China is the global hotspot in both climate change mitigation and human health protection. Thus, in addition to the annual editions of the <italic>Lancet</italic> Countdown global report, scholars from Department of Earth System Science, Tsinghua University who have been involved in the series of global reports, are invited to prepare the China policy brief, to provide a unique national analysis and policy recommendations for health and climate change. The 2018 edition of China policy brief, prepared by experts from Tsinghua University and Chinese Center for Disease Control and Prevention, reviewed three indicators mostly related to China’s national conditions, i.e. change in labour capacity, exposure to ambient air pollution and coverage and strength of carbon pricing, and proposed the following policy recommendations: (1) Pay more attention to the labour capacity loss driven by climate change in the policymaking process. Curb greenhouse gas emissions and take effective adaptation measures to manage heat stress at work and avoided unaffordable heat-related economic loss. (2) Prioritize measures that both decrease greenhouse gas emissions and reduce air pollution and its related health costs, and incorporate analysis of those benefits into the climate and air pollution control policymaking process in order to fully realize short-term health co-benefits and prevent climate-change-related meteorological conditions that will worsen air pollution in the long run. (3) Ensure full operation of the national ETS and implement ambitious carbon pricing policy as soon as possible. Fully consider the health co-benefits of carbon pricing, speed up the capacity building process, apply carbon pricing broadly across China without delay, and enhance ambition gradually.

The Effect of Heat Stress on Autophagy and Apoptosis of Rumen, Abomasum, Duodenum, Liver and Kidney Cells in Calves.

Simple SummaryHeat stress causes significant negative responses in the dairy industry. The objective of this study was to assess the effect of heat stress on the autophagy and apoptosis of the rumen, abomasum, duodenum, liver and kidney in calves. The results showed that heat stress could increase the autophagy and apoptosis of the kidney, duodenum and abomasum. However, heat stress had no effect on the autophagy and apoptosis of the liver. In cows, most studies of autophagy and apoptosis have only focused on mammary remodeling. Our results provide new knowledge regarding autophagy and autophagy in calf heat stress management.The objective of this study was to assess the effect of heat stress on the autophagy and apoptosis of the rumen, abomasum, duodenum, liver and kidney in calves. Two groups of Holstein male calves were selected with similar birth weights and health conditions. Heat stress (HT): Six calves (birth weight 42.2 ± 2.3) were raised from July 15 to August 19. Cooling (CL): Six calves (birth weight 41.5 ± 3.1 kg) were raised from April 10 to May 15. All the calves were euthanized following captive bolt gun stunning at 35 d of age. The expression of protein 1 light chain 3-Ⅱ (LC3-Ⅱ) and caspase3 in the rumen, abomasum, duodenum, liver and kidney were determined by western blotting. In addition, other possible relevant serum biochemical parameters were evaluated. Significant differences were observed in alkaline phosphatase (ALP), albumin (ALB) and glucose (Glu). The results showed that heat stress could increase the autophagy and apoptosis of the kidney, duodenum and abomasum. However, heat stress had no effect on the autophagy and apoptosis of the liver. Additionally, the expression of caspase-3 in the rumen in HT was significantly lower than that in CL. In conclusion, the effects of heat stress on autophagy and apoptosis are organ-specific. The results provide knowledge regarding autophagy and autophagy in calf heat stress management.

Genetic profiling of Hsp70 gene in Murrah buffalo (Bubalus bubalis) under sub-tropical climate of India.

This study was aimed to genetic profiling of heat shock protein 70 (Hsp70) gene in Murrah buffalo investigating 50 unrelated adult animals at ICAR-Research Complex for Eastern Region, Patna (India) in winter, spring, and summer. PCR ready genomic DNA samples and season-wise total RNA samples were prepared. The PCR products of Hsp70 eluted from agarose gel were sequenced and analyzed. The first-strand cDNA was synthesized and concentration was equalized to 25 ng/μl. Expression kinetics of mRNA transcripts in different seasons was studied using Brilliant SYBR Green QPCR technique and the data retrieved was analyzed by least-squares ANOVA. DNA sequencing by primer walking revealed four allelic variants of Hsp70 gene. Alignment study revealed one substitution in 5'UTR, six substitutions in coding region, and one addition in 3'UTR. The highest percent identity and negligible phylogenetic distance were found among the alleles and reference bovine sequences. The relative mRNA expression was significantly higher in summer when THI ≥ 84 than the spring and winter; fold change increased by 4.5 times in summer than the spring whereas found nearly half in winter. These findings can be useful for heat stress management in buffaloes and help in understanding the mechanism of thermo-regulation well.

Comparing dairy farm milk yield and components, somatic cell score, and reproductive performance among United States regions using summer to winter ratios

Heat stress abatement is a challenge for dairy producers in the United States, especially in the southern states. Thus, managing heat stress is critical to maintain dairy cow performance in the summer. The ability to employ a metric to measure heat stress and evaluate abatement strategies may benefit dairy producers by providing meaningful feedback on the effectiveness of current and future management strategies with the goal of improving heat stress management. Therefore, this study aimed to explore the use of the summer to winter performance ratio metric to quantify and compare farm performance variables among regions of the United States. Monthly performance data recorded by the Dairy Herd Improvement Association from 2007 to 2016, for all US Dairy Herd Improvement Association herds processing records through Dairy Records Management Systems (Raleigh, NC), were obtained. Season dates were based on the astronomical definition of the Northern Hemisphere with summer as June 21 to September 21 and winter as December 21 to March 19. States were grouped into regions based on climate zone classification. Performance records included a total of 16,573 herds [Northeast (n = 7,955), Midwest (n = 6,555), Northern Plains (n = 305), Southeast (n = 1,370), and Southern Plains (n = 388) regions]. Herd test day performance variables energy-corrected milk, somatic cell score, milk fat and protein percentage, conception rate, heat detection rate, and pregnancy rate in summer and winter were used to calculate summer to winter ratios for each region. The MIXED procedure of SAS 9.4 (SAS Institute Inc., Cary, NC) was used to compare test day performance variables. The effects of year, mean days in milk, mean 150-d milk, mean herd size, and number of milkings per day were included as covariates in the models. Dairy cattle performance in all climate regions was negatively affected by summer heat stress, but some regions greater than others. A difference was also observed among regions when comparing summer to winter ratios for each performance parameter. This indicates that summer performance varies by climate region identified by the summer to winter ratio and demonstrates usefulness of the metric to monitor degree of heat stress based on performance.

Estimation of Heat Stress and Maximum Acceptable Work Time Based on Physiological and Environmental Response in Hot-Dry Climate: A Case Study in Traditional Bakers.

Background:Heat stress is common among workers in hot-dry areas. To take preventive strategies for the protection of workers against heat stress, it is important to choose a suitable index that can accurately explain environmental parameters relative to physiological responses. Objective:To evaluate heat stress and maximum acceptable work time (MAWT) based on physiological and environmental response in hot-dry climate among traditional bakers.Methods:The current study was carried out on 30 traditional bakers of 3 different bread baking systems in Ahvaz, Iran. Environmental and physiological parameters were measured simultaneously for a work shift. The work-rest time was also determined based on the relative heart rate (RHR) and the wet-bulb globe temperature (WBGT) index.Results:The average WBGT index was estimated to be higher than the standard limit for all baking stations. Despite the higher-than-the-recommended-limit WBGT index, there was no significant relationship between the WBGT index and physiological parameters. The results indicated a significant (p<0.05) difference between the percentages of work-rest time estimated using the WBGT and RHR index.Conclusion:Based on the results of environmental and physiological monitoring of this study as well as the limitations of the use of the WBGT index, it seems that using WBGT as a standard index would not suit heat stress management in hot-dry climates. A revision of this standard to adapt to hot climatic conditions should be in order.

Assembling a thermal rhythmanalysis: Energetic flows, heat stress and polyrhythmic interactions in the context of climate change

Rhythmanalysis, as developed by Lefebvre and Regulier, has provided theoretical and methodological inspiration for a growing diversity of work in geography. We focus on the energetic liveliness and agency of rhythm to engage with heat as an energetic form and heat stress as a threat to bodily health that is becoming intensified with climate change. We deploy the analytical vocabulary of rhythmanalysis to conceptualize and empirically trace how heterogeneous, polyrhythmic interactions play out in space and time as energetic-thermal flows are variously exchanged, accumulated and dispersed within and around human bodies. At the empirical site of an ‘open-cut’ mine in northern Australia, where labour is physically intense, intrinsically hazardous and thermally at the threshold of embodied capacities to function, we develop a distinctive interdisciplinary analysis of rhythms of the thermal environment; rhythmic patterns in the choreography of labour and production; and corporeal rhythms in working bodies. Combining thermal physiology, ethnography and environmental monitoring methods to reveal these interacting rhythms, we identify how polyrhythmic thermal entanglements produce and shape the management of heat stress, and their significance for movements between ‘eurhythmic’ and ‘ arrhythmic ’ conditions. The case study pushes these terms to their limits, so we propose 'dysrhythmic' as a new adjective for the rhythmanalytic lexicon that enables greater analytical traction on the components of polyrhythmic assemblages. Beyond the specific problem of managing heat stress, we argue there is much insight to be gained from bringing rhythmanalysis into geographical engagements with the temporalities of adaptation in a changing global climate.

Institutional logics of processing safety in production: The case of heat stress management in a megaproject in Australia

Despite evidence that a safe and healthy workforce is essential to construction project productivity, the resources and time committed to safety are often perceived as counterproductive. This study explores the multiple institutional logics underpinning the duality between safety and productivity in the construction industry. Specifically, it explores the tensions between safety and production through an institutional lens by untangling the institutional logics of processing safety in production. A theory of protection, production and reconciling logics is developed and refined through an in-depth case study of heat stress management in a mega-project in Australia. Ethnographic data were collected over a six-day working week on site, interpreted using institutional analysis and conceptualized with a grounded theory approach. The results confirmed the co-existence of the three logics in the power dynamics between employers, unions, regulators and workers. It is found that the production and the protection logic leads to paradoxical effect of their desired goals, and a reconciling logic emerges in the bottom-up initiatives which aims for community building and leads to improvement in both safety and productivity. However, the reconciling logic was found incomplete and handicapped due to the lack of involvement at senior management level and the production side of the project organization.

Heat stress management in poultry farms: A comprehensive overview.

Heat stress causes significant economic losses in poultry production, especially in tropical and arid regions of the world. Several studies have investigated the effects of heat stress on the welfare and productivity of poultry. The harmful impacts of heat stress on different poultry types include decreased growth rates, appetites, feed utilization and laying and impaired meat and egg qualities. Recent studies have focused on the deleterious influences of heat stress on bird behaviour, welfare and reproduction. The primary strategies for mitigating heat stress in poultry farms have included feed supplements and management, but the results have not been consistent. This review article discusses the physiological effects of heat stress on poultry health and production and various management and nutritional approaches to cope with it.

Management of Spot Blotch and Heat Stress in Spring Wheat Through Azoxystrobin-Mediated Redox Balance

Application of foliar fungicides for the management of spot blotch of wheat in South Asia is needed when the weather is extremely conducive to disease progression. Field experiments were conducted during two consecutive years 2014–2015 and 2015–2016 to evaluate the effect of fungicides in late-sown wheat which suffers from the combined stress of terminal heat and spot blotch. Azoxystrobin (125 g a.i./ha) when applied twice (ZGS 50 and ZGS 60) and thrice (ZGS 40, 50 and 60) was comparable and gave the best control. In two sprays, the area under disease progress curve (AUDPC) was reduced to 161 compared to 763 under unprotected. Application of fungicide maintained the leaf area under greenness, chlorophyll content and normalized difference vegetative index (NDVI) up to physiological maturity. The canopy temperature (CT) was also reduced in fungicide-treated plots. The positive effect of fungicide on increased days to maturity (11.5 days) contributed significantly to thousand kernel weight (TKW) and grain yield. The fungicide appeared to balance the level of reactive oxygen species like hydroxyl radicals (OH−) and superoxide radicals (O2−), reducing membrane damage and increasing antioxidants like superoxide dismutase (SOD), catalase (CAT). The application of azoxystrobin appeared to manage the terminal heat stress through redox balance and reduced the spot blotch resulted in enhanced grain yield.

Assessment of Heat Stress Exposure among Construction Workers in the Hot Desert Climate of Saudi Arabia.

ObjectivesExcessive heat exposure poses significant risks to workers in hot climates. This study assessed the intensity and duration of heat stress exposure among workers performing residential construction in southeastern Saudi Arabia (SA) during the summer, June–September 2016. Objectives were to: identify work factors related to heat stress exposure; measure environmental heat exposure at the construction sites; assess the heat stress risk among workers using the wet bulb globe temperature (WBGT) index; and determine if temperature-humidity indices can be appropriate alternatives to WBGT for managing heat stress risk at the construction sites.MethodsWorksite walkthrough surveys and environmental monitoring were performed, indoors and outdoors, at 10 construction sites in Al-Ahsa Province. A heat stress exposure assessment was conducted according to the American Conference of Governmental Industrial Hygienists (ACGIH®) guidelines, which uses the WBGT index. WBGT measurements from two instruments were compared. Alternative heat stress indices were compared to the WBGT: the heat index (HI) and humidex (HD) index.ResultsConstruction workers were exposed to excessive heat stress, indoors and outdoors over a large part of the work day. Complying with a midday outdoor work ban (12–3 p.m.) was not effective in reducing heat stress risk. The highest intensity of exposure was outdoors from 9 a.m. to 12 p.m.; a period identified with the highest hourly mean WBGT values (31–33°C) and the least allowable working time according to ACGIH® guidelines. Comparison of the alternative indices showed that the HI is more reliable than the HD as a surrogate for the WBGT index in the climate studied.ConclusionThe extreme heat exposure represents a serious risk. The severity of heat stress and its impact are projected to increase due to climate change, emphasizing the need for immediate improvement of the current required protective measures and the development of occupational heat stress exposure guidelines in SA.