Occupational Heat Research Articles

The effect of consuming a sucrose-containing sports drink on acute kidney injury risk during a four-hour simulated occupational heat stress.

Occupational heat stress increases acute kidney injury risk. Drinking a soft drink sweetened with high fructose corn syrup further elevates this acute kidney injury risk. However, the impact of sucrose, another fructose containing-sweetener, on acute kidney injury risk remains unexplored. We tested the hypothesis that drinking a sucrose-containing sports drink increases acute kidney injury risk when compared to drinking a sugar-free sports drink during four hours of simulated occupational heat stress. Ten healthy adults consumed a sucrose-containing or sugar-free sport drink ad libitum during four-hour exposures to wet bulb globe temperatures of ~28°C. 30 min of work and 30 min of rest were completed each hour. Work involved treadmill walking at a fixed rate of metabolic heat production (sucrose-containing: 6.0±1.2 W/kg, sugar-free: 5.5±0.9 W/kg, p=0.267). The product of urinary insulin-like growth factor-binding protein 7 and tissue inhibitor of metalloproteinase-2, normalized to urine specific gravity ([IGFBP7·TIMP-2]USG), provided an acute kidney injury risk index. Mean core (intestinal: n=13, rectal: n=7) temperature (sucrose-containing: 37.5±0.1°C, sugar-free: 37.5±0.3 °C; p=0.914), peak core temperature (sucrose-containing: 37.8±0.2°C, sugar-free: 37.9±0.3 °C; p=0.398), and percent changes in body mass (sucrose-containing: -0.5±0.4%, sugar-free: -0.3±0.6%; p=0.386) did not differ between groups. [IGFBP7∙TIMP-2]USG increased in both groups (time effect: p=0.0254) with no drink (p=0.675) or interaction (p=0.715) effects. Peak change [IGFBP7∙TIMP-2]USG did not differ between sucrose-containing (median 0.0116 [-0.0012, 0.1760] (ng/mL)²/1000) and sugar-free (median 0.0021 [0.0003, 0.2077] (ng/mL)²/1000; p=0.796). Sucrose-containing sports drink consumption during simulated occupational heat stress does not modify acute kidney injury risk when compared to sugar free-sport drink consumption.

Efficacy Of A Potential Wearable Cooling Technology During Simulated Occupational Heat Stress - A Pilot Study

Efficacy Of A Potential Wearable Cooling Technology During Simulated Occupational Heat Stress - A Pilot Study

Foot Cooling To Preserve Physical Work Capacity During Occupational Heat Stress -a Pilot Study

Foot Cooling To Preserve Physical Work Capacity During Occupational Heat Stress -a Pilot Study

Effect of cold beverages on whole-body heat exchange in young and older males during intermittent exercise in the heat.

To mitigate health risks associated with occupational heat stress, workers are advised to adhere to a work-rest regimen, and hydrate regularly. However, it remains unclear if beverage temperature influences whole-body heat exchange during work-rest cycles, and if responses differ in older workers who have a blunted heat loss capacity. Ten young (mean [SD]: 22 [3] years) and 10 older (60 [4] years) males performed four 15-min bouts of moderate-intensity cycling at a fixed rate of metabolic heat production (200 W·m-2), each interspersed by 15-min rest in dry heat (40°C, ~12% relative humidity). On separate days, participants consumed either ice-slurry (~0°C), standardized to provide a heat transfer capacity of 75 kJ·m-2, or an identical mass of warm fluid (37.5°C) before the first and third exercise bouts. Evaporative and dry heat exchange (direct calorimetry) and metabolic heat production (indirect calorimetry) were measured continuously to determine cumulative heat storage (summation of heat loss and heat gain) over the entire protocol. Rectal temperature was also measured continuously. Relative to warm fluid, ice-slurry ingestion reduced cumulative heat storage in young (69 [181] vs. 216 [94] kJ) and older males (90 [104] vs. 254 [140] kJ, main effect: p < 0.01), but was unaffected by age (p = 0.49). However, rectal temperature was unaffected by beverage temperature in both groups (all p ≥ 0.15). We show that cold fluid ingestion is an appropriate administrative control for both young and older males as it can mitigate increases in body heat content during moderate-intensity work-rest cycles in dry heat.

Examining Management and Employees' Perceptions of Occupational Heat Exposure and the Effectiveness of a Heat Stress Prevention Intervention on Safety and Well-Being among Natural Gas Construction Workers: A Qualitative Field-Based Study.

Numerous risk factors have been identified as significantly influencing outdoor workers' risk for heat stress and heat-related conditions, impacting their health, well-being, and productivity. However, the specific effects of these factors on construction workers' safety, health, and well-being remain under-researched. With climate change increasing temperatures, assessing heat stress among construction workers is imperative. To identify the barriers and facilitators influencing the safety of natural gas construction workers and evaluate an implemented heat stress intervention. In the summer of 2023, two semi-structured interviews and six focus groups were conducted with twenty-one stakeholders at a Texas natural gas construction site. Key facilitators include employee preparedness, use of employer-provided resources, hydration logs, and real-time communication tools. Contrarily, the barriers include daily work schedules, access to dehydrating beverages, and generational differences with the non-implementation of mandatory rest breaks. The heat stress program was perceived as effective, surpassing recommended guidelines. To advance construction workers' safety, health, and well-being, both employee involvement and employer management are needed, along with no-cost accessible resources. Additionally, implementing a required routine rest break and comprehensive heat stress education, particularly for older workers, will significantly promote safety and safe work practices in hot environments. Note: in this study, the terms 'worker' and 'employee' are used interchangeably.

Occupational heat stress and its health impacts- an overview of research status and need for further research in Southeast Asia with special emphasis on mitigation strategies in North East India.

The Intergovernmental Panel on Climate Change, IPCC predicts that hot seasons will get even hotter due to global climate change. There exists a critical dependence of human metabolic processes on temperature. Changes in thermal balance therefore, have an adverse effect on health because they raise body temperature, cause excessive sweating, and accelerate the rate of dehydration. Different nations and professional groups use different techniques to measure heat strain. This paper aims to review previous research conducted in the area of heat strain due to heat exposure among workers in Southeast Asia and also to profile mitigation strategies in North East India. Studies conducted between the years 2011 to 2023 in the evaluation of the health impacts of occupational heat stress were searched systematically using several sources of databases like PubMed, Google Scholar, Science Direct, Web of Science, Scopus, etc. It was noted that a greater proportion of previous research on evaluating physiological effects was carried out in controlled environments as opposed to real-world field settings. While such studies give us valuable insights into the relationship, applying the same methodology in the workplace may not be feasible. In India, very few research has been carried out on workplace heat stress, and even fewer have been done in North East India using physiological indicators. North East India is also affected by global climate change leading top more hotter days than before. The region of Northeast India, particularly Guwahati (Assam), has recently seen extreme heat waves during the sweltering summer months. With less literature available in this geographical location, studies with actual field-based settings are much needed to understand the occupational health impacts in this region. This review can formulate a suitable methodology for assessing the health impacts in working environment. This can also help the local health professionals to recognize the heat strain parameters that are acceptable worldwide, and use as pertinent indicators to scrutinize worker's health and develop preventive agendas as climate change advances.

The Occupational Heat Exposure-related Symptoms Prevalence and Associated Factors Among Hospitality Industry Kitchen Workers in Ethiopia: Wet Bulb Globe Temperature

BackgroundOccupational heat stress caused by excessive environmental heat gain disrupts thermoregulatory mechanisms and harm workers' health and productivity. Kitchens are known for their thermal risks; however, research on heat stress in kitchen is limited. This study aimed to bridge this knowledge gap by assessing, the prevalence of heat-stress-related symptoms, and associated factors among kitchen workers in Gondar City, Ethiopia. MethodsThis institutional-based cross-sectional study (April to June 2023) evaluated heat stress among hospitality kitchen workers in Ethiopia. Heat exposure was measured using hygrometers. A simple random sample of 605 participants completed a survey and data was exported to Statistical Package for Social Science version 26. To assess strength and direction an adjusted odds ratio with 95% confidence interval (CI) was employed. A p-value of less than 0.05 was utilized to identify significant associations. ResultsOver the last 6 months 67.1% (95% CI: 63.0, 71.1), of the participants reported heat-stress symptoms. Multivariable analysis revealed that age ≥40 years [AOR: 2.28; 95% CI (1.08, 4.82)], high workload [AOR: 1.89; 95% CI (1.04, 3.49)], poor heat mitigation practice [AOR: 2.39; 95% CI (1.58, 3.59), wood fuel [AOR: 2.60; 95% CI (1.54, 4.40)], improper ventilation [AOR: 3.28; 95% CI (1.56, 6.87)], and higher heat index value [AOR: 2.15; 95% CI (1.35, 3.42)] were factors significatly associated with heat stress related symptoms. ConclusionThis study identified a high prevalence of heat–stress-related symptoms among kitchen workers. Mitigation strategies include improved ventilation, cooling, advanced building designs, and heat reduction technologies. Future research should utilize standard heat-stress assessment tools.

Creatinine clearance is maintained in a range of wet-bulb globe temperatures and work-rest ratios during simulated occupational heat stress.

We tested the hypothesis that compliance with the National Institute for Occupational Safety and Health (NIOSH) heat stress recommendations will prevent reductions in glomerular filtration rate (GFR) across a range of wet-bulb globe temperatures (WBGTs) and work-rest ratios at a fixed work intensity. We also tested the hypothesis that noncompliance would result in a reduction in GFR compared with a work-rest matched compliant trial. Twelve healthy adults completed five trials (four NIOSH compliant and one noncompliant) that consisted of 4 h of exposure to a range of WBGTs. Subjects walked on a treadmill (heat production: approximately 430 W) and work-rest ratios (work/h: 60, 45, 30, and 15 min) were prescribed as a function of WBGT (24°C, 26.5°C, 28.5°C, 30°C, and 36°C), and subjects drank a sport drink ad libitum. Peak core temperature (TC) and percentage change in body weight (%ΔBW) were measured. Creatinine clearance measured pre- and postexposure provided a primary marker of GFR. Peak TC did not differ among NIOSH-compliant trials (P = 0.065) but differed between compliant versus noncompliant trials (P < 0.001). %ΔBW did not differ among NIOSH-compliant trials (P = 0.131) or between compliant versus noncompliant trials (P = 0.185). Creatinine clearance did not change or differ among compliant trials (P ≥ 0.079). Creatinine clearance did not change or differ between compliant versus noncompliant trials (P ≥ 0.661). Compliance with the NIOSH recommendations maintained GFR. Surprisingly, despite a greater heat strain in a noncompliant trial, GFR was maintained highlighting the potential relative importance of hydration.NEW & NOTEWORTHY We highlight that glomerular filtration rate (GFR) is maintained during simulated occupational heat stress across a range of total work, work-rest ratios, and wet-bulb globe temperatures with ad libitum consumption of an electrolyte and sugar-containing sports drink. Compared with a work-rest matched compliant trial, noncompliance resulted in augmented heat strain but did not induce a reduction in GFR likely due to an increased relative fluid intake and robust fluid conservatory responses.

Occupational heat exposure and its impact on kidney health among cashew workers.

Rising temperatures increase workers' risk of heat-related illnesses due to heat stress (HS). Chronic Kidney Disease of unknown etiology (CKDu) is rising in non-agricultural workers in hot climates. Dehydration, heat stress, and physical exertion can damage cashew workers' kidney health. In 2020-2021, 262 cashew workers in Cuddalore, Tamil Nadu were assessed for Wet Bulb Globe Temperature (WBGT), and job-specific American Conference of Governmental Industrial Hygienists standard was used to evaluate workload. "High heat-exposed" meant heat stress exceeded the Threshold Limit Value for safe manual work (27.5°C for heavy and 28°C for moderate physical activity). Heat Strain Indicators (HSIs) such as Tympanic Temperature (Ttemp), Sweat Rate (SwR), Urine Specific Gravity (USG), and urine dipstick parameters were measured in all workers, however serum creatinine was measured only in 100 workers. Glomerular Filtration Rate(eGFR) was calculated using theCKD-EPIequation. A standardized questionnaire assessed heat-related health symptoms. Over 65% of workers experienced wet bulb globe temperature exposures exceeding the threshold limit value (Avg.- wet bulb globe temperature 30.4°C ± 1.8°C). Ninety-five percent of heat-exposed workers experienced at least one of the physiological heat strain indicators. The risk of urogenital symptoms was 7.7 times greater among high-heat-exposed workers (95% CI 3.4-17.1), which corroborates well with the measured post shift urine specific gravity (37%). Despite controlling for relevant confounders (age & gender), high-heat-exposed workers had 3.5-fold higher odds of eGFR < 90ml/min/1.73m2 compared to less-exposed workers (95% CI 1.1-10.6). Persistent heat stress promotes heat-related disorders in cashew workers and lowers eGFR. This needs further investigation to determine its longer term effects on kidney function. Workplace cooling solutions that reduce heat stress are critically needed to protect thekidneys and ensureoccupational health.

Validation of formulae predicting stroke volume from arterial pressure: with particular emphasis on upright individuals in hot ambient conditions.

During heatwaves, it is important to monitor workers' cardiovascular health since 35% of those working in hot environments experience symptoms of heat strain. Wearable technology has been popularized for monitoring heart rate (HR) during recreational activities, but it can also be used to monitor occupational heat strain based on core and skin temperatures and HR. To our knowledge, no devices estimate the cardiovascular strain directly based on stroke volume (SV) or cardiac output (CO). In addition to the hardware, there are limitations regarding the lack of suitable algorithms that would provide such an index based on relevant physiological responses. The validation of the formulae already existing in literature was the principle aim of the present study. We monitored the cardiovascular responses of our participants to a supine and 60° head-up tilt at the same time each day. During the test, we measured blood pressure derived by finger photoplethysmography, which also provided beat-by-beat measures of SV and CO. Afterwards, we compared the SV derived from the photoplethysmography with the one calculated with the different equations that already exist in literature. The evaluation of the formulae was based on comparing the error of prediction. This residual analysis compared the sum of the squared residuals generated by each formula using the same data set. Our findings suggest that estimating SV with existing formulae is feasible, showing a good correlation and a relatively small bias. Thus, simply measuring workers' blood pressure during breaks could estimate their cardiac strain.

Climate change and heat stress resilient outdoor workers: findings from systematic literature review

PurposeGlobal warming has led to an increase in the number and intensity of extreme heat events, posing a significant threat to the health and safety of workers, especially those working outdoors, as they often have limited access to cooling strategies. The present systematic literature review (a) summarizes the current knowledge on the impacts of climate change on outdoor workers, (b) provides historical background on this issue, (c) explores factors that reduce and increase thermal stress resilience, (d) discusses the heat mitigation strategies, and (e) provides an overview of existing policy and legal frameworks on occupational heat exposure among outdoor workers.Materials and methodsIn this systematic review, we searched scientific databases including Scopus (N = 855), Web of Science (N = 828), and PubMed (N = 202). Additionally, we identified relevant studies on climate change and heat-stress control measures through Google Scholar (N = 116) using specific search terms. In total, we monitored 2001 articles pertaining to worker populations (men = 2921; women = 627) in various outdoor climate conditions across 14 countries. After full-text assessment, 55 studies were selected for inclusion, and finally, 29 eligible papers were included for data extraction.ResultsFailure to implement effective control strategies for outdoor workers will result in decreased resilience to thermal stress. The findings underscore a lack of awareness regarding certain adaptation strategies and interventions aimed at preventing and enhancing resilience to the impact of climate change on heat stress prevalence among workers in outdoor tropical and subtropical environments. However, attractive alternative solutions from the aspects of economic and ecological sustainability in the overall assessment of heat stress resilience can be referred to acclimatization, shading, optimized clothing properties and planned breaks.ConclusionThe integration of climate change adaptation strategies into occupational health programs can enhance occupational heat resilience among outdoor workers. Conducting cost-benefit evaluations of health and safety measures for thermal stress adaptation strategies among outdoor workers is crucial for professionals and policymakers in low- and middle-income tropical and subtropical countries. In this respect, complementary measures targeting hydration, work-rest regimes, ventilated garments, self-pacing, and mechanization can be adopted to protect outdoor workers. Risk management strategies, adaptive measures, heat risk awareness, practical interventions, training programs, and protective policies should be implemented in hot-dry and hot-humid climates to boost the tolerance and resilience of outdoor workers.

Occupational Risks of Agricultural Workers Exposed to Heat: Literature Review

Proposal: The aim of this study is to conduct a literature review on the occupational hazards of agricultural workers exposed to heat while carrying out their activities. Theoretical Framework: Heat exposure poses a serious occupational risk for agricultural workers, increasing the incidence of dehydration, heat exhaustion, and sunstroke. Method: The methodology adopted for this research involves a literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) methodology. Data collection was carried out through a bibliographic survey from the period 2005 to 2024 in the Pubmed, Web of Science, and Scopus databases. The search used keywords such as "risks," "workers," "agriculture," and "heat." Results and Discussion: The results revealed the selection of 109 articles, and after reading the abstracts, those that did not align with the research proposal were excluded. After filtering, 07 articles remained, whose topics showed affinity with the research. The literature points to a growing trend of studies addressing thermal discomfort as an occupational hazard, prevalent in open and semi-open environments. Specific studies for certain agricultural operations, such as groups of workers dealing with grain dryers and furnaces, are scarce and have limited conclusions. Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practical aspects in the field of occupational heat exposure for agricultural workers. These implications can encompass various sectors of post-harvest grain processing. Originality/Value: This study contributes to the literature by gathering information published in different databases on occupational heat exposure. The significance and value of this research are highlighted by a limited number of works in the literature, stressing the need for further research in the field. Based on this premise, more studies on agricultural work in heat-prone environments and consequent thermal discomfort should be encouraged to stimulate discussions on actions to eliminate the risks involved in these operations.

Farmworker-Relevant Heat Exposure in Different Crop and Shade Conditions

ABSTRACT Objectives Agricultural workers are at risk of heat-related illness, which is preventable. Few field studies have compared farmworker-relevant heat exposure in different conditions. We examined heat exposure over time in different potential shade and work locations to inform future occupational heat prevention approaches. Methods We assessed heat exposure in Eastern Washington State (WA) cherry and grape fields in August 2022. QUESTemp° monitors recorded Wet Bulb Globe Temperature (WBGT) and Black Globe Temperature (BGT) every 10 min from approximately 07:00–14:00 for three days in the center of crop rows (mid-row), under portable shade structures (shade), and in open field (open) locations. Linear mixed effects regression (LMER) models compared WBGT and BGT among field locations. Hourly time-weighted average WBGT and comparisons with occupational exposure limits (OELs) were computed for different hypothetical work-rest cycles during the hottest sampling hours, assuming different worker effort levels, rest locations (mid-row versus shade), and acclimatization statuses. Results Across all crops and locations during the study period, the mean/SD air temperature was 31°C (88°F)/3.9°C (6.9°F), with a maximum temperature of 39°C (102°F) and a mean/SD relative humidity of 30%/9.6%. LMER models suggested no significant difference in mid-row versus open WBGT but significantly lower WBGT in shade versus open locations for both cherries (main effect −5.14: 95% confidence interval [CI] −6.97,−3.32) and grapes (−6.20: 95%CI −7.73,−4.67), though this difference diminished over the course of the day. BGT was significantly higher in the mid-row than the shade (cherries main effect 14.33: 95%CI 9.52,19.13 and grapes 17.10: 95%CI 13.44,20.75). During the hottest sampling hour, the exceedances of OELs were reduced with assumptions of increased shaded break lengths, reduced effort level, and acclimatization. Conclusions Shade canopies, but not the crops studied, provided significant reductions in heat exposure. We observed increased protection from heat assuming longer shaded breaks and reduced effort levels. Results highlight the need for additional field research on the effectiveness, feasibility, and acceptability of different shade types and work-rest cycles to guide employer optimization of best practices for worker protections, including acclimatization before high heat, sufficient shaded rest time, reduced effort levels as the day warms, and avoiding work in peak heat.

Substantial increase of heat-induced labor and economic loss in China under rapid economic and environmental temperature growth

Exposure to heat stress causes diminished work performance and leads to economic loss. In the last two decades, China has experienced both rapid economic development and environmental warming; however, the spatiotemporal variations of association between environmental heat and labor loss have been rarely investigated behind this double impact. Here, we evaluated the variation in China's heat-induced labor productivity loss and related economic cost from 2001 to 2019 and investigated the effect of economic development and regional warming. We found that decline in labor productivity because of heat stress increased significantly (p < 0.05 for heavy-intensity work), and the corresponding economic loss also exhibited a drastic increase by 6- to 9-fold. The relative economic loss showed a slight but nonsignificant increase with an average value of 0.54% of the annual total earnings. At the sub-regional and sectoral level, adverse effects were more prominent in the southeast region, and the secondary industry sectors, such as construction and manufacturing, contributed to larger proportions of economic losses. The transformation of industrial structure made economic sectors more vulnerable to heat exposure, and increasingly preventive effects of air-conditioning use were noted on economic damage due to heat-induced productivity decline (36.0% relative economic benefits in 2019 compared to 9.7% in 2001). Our findings could provide a deep insight into heat burden on occupational health and heat adaptation strategies regionally under climate change, especially in developing areas with higher temperature and humidity environment.

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

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

Assessment of subjective well-being of healthcare workers in response to heat and personal protective equipment under controlled conditions using a standardized protocol

BackgroundDue to climate change, the increasing frequency of hot summer days and heat waves can result in occupational heat strain, especially in non-air-conditioned workplaces. Healthcare workers (HCW) engaged in patient care are particularly affected, as they are additionally exposed to physical stress. The use of personal protective equipment (PPE) can aggravate heat strain in HCW. This study aimed to examine the subjective well-being of HCW when exposed to heat and PPE under controlled conditions.MethodsThis study was designed as a randomized crossover trial. Participants performed standardized healthcare tasks in a climatic chamber for approximately 3.5 h at different indoor temperatures (22 °C and 27 °C) and varied working conditions (with or without PPE). The effects on participants’ subjective well-being, encompassing thermal, physiological and psychological stress were assessed using a customized questionnaire.ResultsHeat had a greater effect than PPE on thermal, physical and psychological stress. Conversely, PPE had a greater effect on physical demand and effort. For the majority of outcomes, combined exposure to heat and PPE resulted in the highest perceived discomfort. Furthermore, the participants reported increased sweating and other discomforts when working at elevated temperatures or with PPE.ConclusionsIn this study, heat and PPE, but particularly the combination of both factors, were identified as unfavorable working environments. Although the trials were conducted in a controlled environment, the outcomes provide valuable information about the effect of heat and PPE on HCW in a real-life setting. Furthermore, the design used in this study can be beneficial in evaluating the effect of mitigation strategies.

Impact of individual and work factors on the heat-related consequences among power plant workers in a hot region

ABSTRACT Prolonged exposure to hot environments increases the probability of heat load that may cause occupational heat strain to workers. This study investigates the impact of individual and work-related factors on the heat-related consequences among power plant workers in a hot region. This cross-sectional study was conducted in 2020. The collecting data tool was a validated self-reported 26 item questionnaire and completed in 534 individuals. We used logistic regression, Adjusted odds ratio (AOR) and maximum likelihood evaluations for data analysis. The findings indicated that age, work environment, physical work demands and drinking fluids during work hours are significant with heat exposure perception, heat-related symptoms, and work performance (P-value<0.05). Further, the male workers aged 40-49 are more prone to heat-related symptoms (AOR 1.34, 95% CI 1.18-2.13). The importance of addressing heat stress in occupational settings is necessary and informing strategies to help workers adapt to heat in hot workplaces.

Practical cooling interventions for preventing heat strain in indoor factory workers in Thailand.

Occupational heat stress, exacerbated by factors such as climate change and insufficient cooling solutions, endangers the health and productivity of workers, especially in low-resource workplaces. To evaluate the effectiveness of two cooling strategies in reducing physiological strain and productivity of piece-rate workers over a 9-h work shift in a southern Thailand sawmill. In a crossover randomized control trial design, 12 (33 ± 7 y; 1.58 ± 0.05 m; 51 ± 9 kg; n = 5 females) medically screened sawmill workers were randomly allocated into three groups comprising an established phase change material vest (VEST), an on-site combination cooling oasis (OASIS) (i.e., hydration, cold towels, fans, water dousing), and no cooling (CON) across 3 consecutive workdays. Physiological strain was measured via core temperature telemetry and heart rate monitoring. Productivity was determined by counting the number of pallets of wood sorted, stacked, and stowed each day. Relative to CON, OASIS lowered core temperature by 0.25°C [95% confidence interval = 0.24, 0.25] and heart rate by 7 bpm [6, 9] bpm, compared to 0.17°C [0.17, 0.18] and 10 [9,12] bpm reductions with VEST. It was inconclusive whether productivity was statistically lower in OASIS compared to CON (mean difference [MD] = 2.5 [-0.2, 5.2]), and was not statistically different between VEST and CON (MD = 1.4 [-1.3, 4.1]). Both OASIS and VEST were effective in reducing physiological strain compared to no cooling. Their effect on productivity requires further investigation, as even small differences between interventions could lead to meaningful disparities in piece-rate worker earnings over time.

Ad Libitum Drinking Does Not Modify Renal Oxidative Stress or Inflammation During Simulated Occupational Heat Stress

Prolonged heat exposure increases acute kidney injury (AKI) risk likely due to renal oxidative stress and inflammation. However, the effect of occupational heat stress (OHS) and the modifying role of hydration on renal oxidative stress and inflammation is unknown. This study tested the hypothesis that compared to fluid restriction ad libitum drinking consistent with OHS recommendations will attenuate renal oxidative stress and inflammation during simulated OHS. In a randomized, crossover design, 13 healthy adults (5 women) completed two 2 h OHS simulations consisting of of 8 circuits of treadmill walking (10 min) and rowing (5 min) at an oxygen uptake of 1.2 L/min in a wet bulb globe temperature of 33.1±0.2°C. In the drinking trial (Drink), subjects were provided 237 mL of a non-caloric sport drink (Gatorade Zero) every 15 min and drank ad libitum. In the fluid restriction trial (NoDrink), no fluid was provided. Rectal temperature and body weight were recorded. Urine and blood samples were collected pre-, post- and 1 h post- exposure. Inflammatory (monocyte chemotactic protein-1, MCP-1) and oxidative stress (thioredoxin 1, TRX-1) markers were measured in urine and serum, and fractional excretion (FE) was calculated. AKI risk was quantified as the product of urine insulin-like growth factor-binding protein 7 and urine tissue inhibitor of metalloproteinase 2 ([IGFBP7•TIMP-2]). Data are presented as mean ± SD. Peak rectal temperature was not different between trials (Drink: 38.5±0.4°C, NoDrink: 38.6±0.4°C, p=0.346). Percent changes in body weight were lower in Drink (1.3±0.8% vs. 2.8±0.9%, p&lt;0.001). FETRX-1 was elevated at post- (0.50±0.00%) compared to pre- (0.36±0.00%, p=0.011) and 1 h post- (0.29±0.13%, p=0.011). FEMCP-1 was elevated at post- (1.25±0.18%) compared to pre- (1.02±0.17%, p=0.006) but not 1 h post- (1.27±0.03%, p&gt;0.999). FETRX-1 and FEMCP-1 did not change significantly between trials (trial x time: p³0.622). [IGFBP7•TIMP-2] was higher at 1 h post- (17.5±1.0 (ng/mL)2/1000) compared to pre- (0.2±0.1 (ng/mL)2/1000, p&lt;0.001) and post- (1.1±0.4 (ng/mL)2/1000, p&lt;0.001) but did not differ between trials (trial x time: p=0.556). Peak changes in [IGFBP7•TIMP-2] were not significantly correlated with peak changes in FETRX-1 (r=0.126, p=0.557) or FEMCP-1 (r=0.292, p=0.166) and were correlated with peak changes in serum MCP-1 (r=0.714, p&lt;0.001) but not serum TRX-1 (r=0.227, p=0.286). Two hours of simulated OHS increased renal inflammation (FEMCP-1), oxidative stress (FETRX-1), and AKI risk ([IGFBP7•TIMP-2]), while ad libitum drinking did not modify FEMCP-1, FETRX-1, or [IGFBP7•TIMP-2]. Lack of correlations between peak changes in [IGFBP7•TIMP-2] and FEMCP-1, FETRX-1, or serum TRX-1, but the strong positive correlation with peak serum MCP-1 suggests a role for systemic inflammation in OHS induced AKI risk. NCT05458843 Funding: R01OH011528. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Violation of Allowable Work Intensity does not Augment Acute Kidney Injury Risk During Simulated Occupational Heat Stress

We recently demonstrated that violation of the National Institute of Occupational Safety and Health (NIOSH) heat stress recommendations by exceeding the allowable wet bulb globe temperature (WBGT) for a given moderate work intensity and work:rest ratio augmented acute kidney injury (AKI) risk. However, the role of work intensity (at a fixed work:rest ratio) on AKI risk during NIOSH compliant and non-compliant scenarios remains largely unknown. This study tested the hypothesis that violating the NIOSH recommendations by exceeding the allowable work intensity at a given WBGT and fixed work:rest ratio would augment AKI risk. Twelve healthy adults completed two NIOSH recommendation compliant trials and one noncompliant trial consisting of a 4 h exposure to a fixed WBGT and work intensity. Work-rest ratio was fixed at 30 min of walking and 30 min of rest each hour. Work intensity (i.e., Hprod) was prescribed as a function of WBGT— 412±51 W (27.3±0.3°C; high intensity compliant [Chigh]), 290±75 W (31.6±0.2°C; low intensity compliant [Clow]), and 410±61 W (31.7±0.2°C; high intensity noncompliant [NChigh]). All subjects were provided 237 mL of sport drink every 15 min and drank ad libitum. TC is presented as peak across the 4 h exposure. Urine samples were collected preexposure, and immediately and 1 h postexposure. Urinary inflammatory (monocyte chemotactic protein-1 [MCP-1]), oxidative stress (thioredoxin 1 [TRX-1]), and AKI risk (the product of insulin-like growth factor-binding protein 7 and tissue inhibitor of metalloproteinase 2 [IGFBP7·TIMP-2]) biomarkers were measured and normalized to urine flow rate. Urinary biomarkers were log transformed before statistical analysis and data are presented as mean ± SD. Peak Tc was higher during the NChigh trial (38.3±0.4°C) compared to the compliant trials (Chigh: 38.0±0.3°C; Clow: 37.8±0.4°C; p≤0.0095). Body weight change from pre- to postexposure did not differ between trials (p=0.7817). MCP-1 increased from pre- to immediately postexposure in all trials (p≤0.0031) but was not different between trials (p=0.1354). TRX-1 increased from pre- to immediately postexposure in all trials (p≤0.0085) but was not different between trials (p=0.6372). [IGFBP7·TIMP-2] increased from pre- to immediately postexposure in all trials (p=0.0454) but the increase was not different between trials (Chigh: -1.7±2.6 LOG [ng/mL2]/1000; Clow: -1.6±2.4 LOG [ng/mL2]/1000; NChigh:-1.2±2.3 LOG [ng/mL2]/1000; p=0.2076). Simulated occupational heat stress elevates AKI risk, likely due to both inflammation and oxidative stress. Violating the NIOSH recommendations by exceeding either the allowable WBGT (i.e., NChigh versus Chigh) or work intensity (i.e., NChigh versus Clow) resulted in a modest elevation in peak Tc but did not modify AKI risk and/or the urinary inflammatory and oxidative stress responses. RCT: NCT04767347; Supported By: R01OH011528. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.