Occupational Heat Research Articles

Changes in surrogate markers of intestinal epithelial injury and microbial translocation in young and older men during prolonged occupational heat stress in temperate and hot conditions.

Exertional heat stress can cause damage to the intestinal epithelium and disrupt gastrointestinal barrier integrity, leading to microbial translocation (MT) linked to the development of heat stroke. This study aimed to assess age-related differences in markers of intestinal epithelial injury and MT following non-heat stress and high-heat stress exercise in healthy young and older men. Markers of intestinal epithelial injury (intestinal fatty acid-binding protein-'IFABP') and MT (soluble cluster of differentiation 14-'sCD14'; and lipopolysaccharide-binding protein-'LBP') were assessed in healthy young (18-30 y, n = 13) and older (50-70 y) men (n = 12). Blood samples were collected before, after 180min of moderate-intensity (metabolic rate: 200 W/m2) walking and following 60min recovery in either a non-heat stress [temperate: 21.9°C, 35% relative humidity (RH)] or high-heat stress (hot: 41.4°C, 35% RH) environment. There were no differences in IFABP and sCD14 between the young and older groups in the temperate condition, while LBP was greater in the older group (+ 0.66 ug/mL; + 0.08 to + 1.24 ug/mL). In the hot condition, the older group experienced greater increases in IFABP compared to the young group (+ 712pg/mL/hr; + 269 to + 1154pg/mL/hr). However, there were no clear between-group differences for sCD14 (+ 0.24 ug/mL/hr, - 0.22 to + 0.70 ug/mL/hr) or LBP (+ 0.86 ug/mL/hr, - 0.73 to + 2.46 ug/mL/hr). While older men may experience greater intestinal epithelial injury following exercise in the heat; this did not lead to a greater magnitude of microbial translocation relative to their younger counterparts.

Heat stress and adverse pregnancy outcome: Prospective cohort study.

To explore the relationship between occupational heat exposure, physiological heat strain indicators and adverse outcomes in pregnant women. Prospective cohort. Workplaces in Tamil Nadu, India. A cohort of 800 pregnant women engaged in moderate to heavy physical work in 2017-2019 and 2021-2022. Participants were recruited at between 8 and 14 weeks of gestation. Occupational heat exposure and heat strain indicators were captured each trimester. 'Heat exposed' was defined as heat stress exceeding the threshold limit value (TLV) for safe manual work (with maximum wet-bulb globe temperatures of 27.5°C for a heavy workload and 28.0°C for a moderate workload). Physiological heat strain indicators (HSIs) such as core body temperature (CBT) and urine specific gravity (USG) were measured before and after each shift. Heat-related health symptoms were captured using the modified HOTHAPS questionnaire. The main outcome measures included (1) a composite measure of any adverse pregnancy outcome (APO) during pregnancy (including miscarriage, preterm birth, low birthweight, stillbirth, intrauterine growth restriction and birth defects), (2) a composite measure of adverse outcomes at birth (3) and miscarriage. Of the 800 participants, 47.3% had high occupational heat exposure. A rise in CBT was recorded in 17.4% of exposed workers, and 29.6% of workers experienced moderate dehydration (USG ≥ 1.020). Heat-exposed women had a doubled risk of miscarriage (adjusted odds ratio, aOR 2.4; 95% confidence interval, 95% CI 1.0-5.7). High occupational heat exposure was associated with an increased risk of any adverse pregnancy and foetal outcome (aOR 2.3; 95% CI 1.4-3.8) and adverse outcome at birth (aOR 2.0; 95% CI 1.2-3.3). High occupational heat exposure is associated with HSIs and adverse pregnancy outcomes in India.

Projecting future labor losses due to heat stress in China under climate change scenarios

Climate change is expected to increase occupational heat stress, which will lead to diminished work performance and labor losses worldwide. However, sub-regional analyses remain insufficient, especially for countries with a heterogeneous spatial distribution of working populations, industries and climates. Here, we projected heat-induced labor losses in China, by considering local climate simulations, working population characteristics and developing an exposure–response function suitable for Chinese workers. We showed that the annual heat-induced work hours lost (WHL), compared to the baseline of 21.3 billion hours, will increase by 121.1% (111.2%–131.1%), 10.8% (8.3%–15.3%), and −17.8% (−15.3%–−20.3%) by the end of the century under RCP(Representative Concentration Pathways)8.5, RCP4.5, and RCP2.6, respectively. We observed an approximately linear upward trend of WHL under RCP8.5, despite the decrease in future working population. Notably, WHL will be most prominent in the southern, eastern and central regions, with Guangdong and Henan accounting for a quarter of national total losses; this is largely due to their higher temperature exposure, larger population size, and higher shares of vulnerable population in total employment. In addition, limiting global warming to 1.5 °C would yield substantial gains. Compared to RCP2.6, RCP4.5, and RCP8.5, all provinces can avoid an average of 11.8%, 33.7%, and 53.9% of annual WHL if the 1.5 °C target is achieved, which is equivalent to avoiding 0.1%, 0.6%, and 1.4% of annual GDP losses in China, respectively. This study revealed climate change will exacerbate future labor losses, and adverse impacts can be minimized by adopting stringent mitigation policies coupled with effective adaptation measures. Policymakers in each province should tailor occupation health protection measures to their circumstances.

Associations of occupational heat exposure and stomach cancer in a population-based case-control study

Associations of occupational heat exposure and stomach cancer in a population-based case-control study

Impact of occupational heat exposure on blood lipids among petrochemical workers: An analysis of 9-year longitudinal data

Impact of occupational heat exposure on blood lipids among petrochemical workers: An analysis of 9-year longitudinal data

Considerations for occupational heat exposure: A scoping review

The ability to regulate core body temperature is a critical factor in avoiding occupational heart stress in demanding environments. Heat-related illness in an occupational setting is complex and multifactorial and includes environment (intrinsic and extrinsic), the occupational clothing requirements and physiological factors. Much of this research began in the gold mines in South Africa after several miners died due to heat related illness. Similar research was conducted during World War Two and was crucial for the creation of acclimatization techniques and strategies for acquiring thermal tolerance. Techniques such as fatigue recovery and body cooling are still used today to prevent heat related illness in individuals with occupations that have frequent exposure to heat and high physical loads. These individuals are at greater risk of heat related illness as extended exposure to a hot or humid environment in combination with strenuous physical activity can overwhelm the body’s homeostatic cooling mechanisms. In addition, individuals from special populations with chronic or acute health impacts such as diabetes mellitus, also have a greater risk for the aforementioned. Currently, there are several heat prevention strategies, including training and education, regulation and monitoring, in place to protect workers from heat related illness and casualty. These strategies, along with future considerations and the impact of climate change will be highlighted in this review.

Consuming A Sugar-containing Sports Drink Does Not Modify Kidney Injury Risk When Adhering To Occupational Heat Stress Recommendations

Consuming A Sugar-containing Sports Drink Does Not Modify Kidney Injury Risk When Adhering To Occupational Heat Stress Recommendations

Assessment of Occupational Heat Stress in A Selected Indonesian Steel Mill

Introduction: Workers in the Indonesian steel manufacturing industry are subject to many heat stress risk factors, ranging from the equatorial climate to physically demanding work tasks which may result in heat- related illnesses and reduced worker productivity. Hence, a study was conducted at Steel Mill X to assess the level of heat stress among its workers, determine the association of related factors and to provide meaningful recommendations. Methods: This study uses a descriptive cross-sectional method to assess workers’ heat risk level and its association with individual, occupational and heat stress symptoms. An online questionnaire was used to collect primary data yet WBGT monitoring data were provided by Steel Mill X as secondary data. Results: The heat stress risk level score ranged from 48 to 140 (M=89.8, SD=±31.0). 122 workers were in the very high-risk category (75.8%). Occupational factors which had a statistically significant association with heat stress risk category includes: work area, length of exposure, air movement, hot surfaces, confined space, clothing factors and WBGT; while heat stress-related symptoms which were associated include headache, fatigue, profuse sweating, extreme thirst and increased body temperature. The absence of significant association between individual factors and heat stress risk category eliminates it as a confounding factor, suggesting occupational factors was the main variable. Conclusion: Control measures such as improving the supply of drinking water and maintenance of cooling systems should be implemented as soon as possible to prevent heat stress among workers.

Retention of Agricultural Workers Participating in a Renal Longitudinal Study

ABSTRACT Objectives The relationship between heat stress, chronic kidney diseases and acute kidney injury has been documented in cross-sectional studies with agricultural workers. However, only a few international studies have assessed renal function in agricultural workers longitudinally. Our research study, Occupational Heat Exposure and Renal Dysfunction (OHEaRD) is the first longitudinal study in the U.S. that monitored renal function in agricultural workers five times over the course of 32-months. The main objectives of this study were to evaluate the rate of retention and identify predictors associated with retention in a longitudinal study with agricultural workers. Methods In January 2020, we enrolled 119 Florida agricultural workers to observe on 5 workdays over 32 months. Retention was defined by the number of follow-up visits that a participant attended, the consistency of visit attendance, and attendance at the last visit. Participants were provided hemoglobin A1C, lipid panel, creatinine measurement, glomerular filtration rate (eGFR), blood pressure, and body mass index results and an incentive gift card were handed out to participants at each visit. Results Four enrollees did not participate on any workday, thus analysis concentrated on the remaining 115 participants. The majority of participants (64%) completed the 32-month study, 78% completed at least 4 visits, and 55% completed all 5 visits. The statistically significant predictors of higher retention among this study were being older in age (p=0.02), Mexican nationality (p=0.004), working in ferneries (p=0.009), more years working in agriculture (p=0.02), and higher total cholesterol (p=0.02). Appreciation for the health tests was associated with greater participation at the final visit (p=0.01). Conclusion Retention in longitudinal studies is crucial to better understand kidney disease among agricultural workers, an understudied population. Participants reported valuing the access to health results, indicating that implementing point-of-care health screenings and providing the health results to each participant is a good retention strategy. There was some evidence that a participant living with or being related to a fellow co-participant could impact retention as they either showed up or missed visits together, suggesting recruiting from the same household may reduce retention.

The Burdens of Occupational Heat Exposure-related Symptoms and Contributing Factors Among Workers in Sugarcane Factories in Ethiopia: Heat Stress Wet Bulb Globe Temperature Meter

BackgroundHeat stress is a harmful physical hazard in many occupational settings. However, consequences of occupational heat exposure among workers in a sugarcane factory in Ethiopia are not well characterized. This study aimed to assess the level of occupational heat exposure-related symptoms and contributing factors. MethodsIn this cross-sectional study, five workstations were selected for temperature measurement. Heat stress levels were measured using a wet-bulb globe temperature index meter. A stratified random sampling technique was used to select 1,524 participants. Heat-related symptoms were assessed using validated questionnaires. ResultsThe level of occupational heat exposure was 72.4% (95% CI: 70.2%–74.8%), while 71.6% (95% CI: 69.3%–74.9%) of participants experienced at least one symptom related to heat stress. The most common heat-related symptoms were swelling of hands and feet (78%), severe thirst (77.8%) and dry mouth (77.4%). The identified risk factors were a lack of reflective shields (AOR: 2.20, 95% CI: 1.53, 3.17), not-enclosed extreme heat sources (AOR: 1.76, 95% CI: 1.23, 2.51), a lack of access to shade (AOR: 9.62, 95% CI: 6.20, 14.92), and inappropriate protective clothing provision (AOR: 1.58, 95% CI: 1.27, 2.71). ConclusionsThe burden of occupational heat exposure and heat-induced symptoms was high. Lack of reflective shields, the absence of enclosed extreme heat sources, a lack of access to shade, and inappropriate protective clothing provision were considerable attributes of heat stress. Therefore, the use of mechanical solutions to stop heat emissions at their sources and the key factors identified were areas for future intervention.

Occupational heat stress, heat-related effects and the related social and economic loss: a scoping literature review.

While there is consistent evidence on the effects of heat on workers' health and safety, the evidence on the resulting social and economic impacts is still limited. A scoping literature review was carried out to update the knowledge about social and economic impacts related to workplace heat exposure. The literature search was conducted in two bibliographic databases (Web of Science and PubMed), to select publications from 2010 to April 2022. A total of 89 studies were included in the qualitative synthesis (32 field studies, 8 studies estimating healthcare-related costs, and 49 economic studies). Overall, consistent evidence of the socioeconomic impacts of heat exposure in the workplace emerges. Actual productivity losses at the global level are nearly 10% and are expected to increase up to 30-40% under the worst climate change scenario by the end of the century. Vulnerable regions are mainly low-latitude and low- and middle-income countries with a greater proportion of outdoor workers but include also areas from developed countries such as southern Europe. The most affected sectors are agriculture and construction. There is limited evidence regarding the role of cooling measures and changes in the work/rest schedule in mitigating heat-related productivity loss. The available evidence highlights the need for strengthening prevention efforts to enhance workers' awareness and resilience toward occupational heat exposure, particularly in low- and middle-income countries but also in some areas of developed countries where an increase in frequency and intensity of heat waves is expected under future climate change scenarios.

Distribution of upper limit of the prescriptive zone values for acclimatized and unacclimatized individuals.

Heat stress has an adverse impact on worker health and well-being, and the effects will increase with more frequent and severe heat events associated with global warming. Acclimatization to heat stress is widely considered to be a critical mitigation strategy and wet bulb globe temperature- (WBGT-) based occupational standards and guidelines contain adjustments for acclimatization. The purpose here was to 1) compare the mean values for the upper limit of the prescriptive zone (ULPZ, below which the rise in core temperature is minimal) between unacclimatized and acclimatized men and women; 2) demonstrate that the change in the occupational exposure limit (ΔOEL) due to acclimatization is independent of metabolic rate; 3) examine the relation between ΔOEL and body surface area (BSA); and 4) compare the exposure-response curves between unacclimatized and acclimatized populations. Empirically derived ULPZ data for unacclimatized participants from Pennsylvania State University (PSU) and acclimatized participants from University of South Florida (USF) were used to explore the difference between unacclimatized and acclimatized heat exposure limits. The findings provide support for a constant 3°C WBGT OEL decrease to account for unacclimatized workers. Body surface area explained part of the difference in ULPZ values between men and women. In addition, the pooled PSU and USF data provide insight into the distribution of individual values for the ULPZ among young, healthy unacclimatized and acclimatized populations in support of occupational heat stress guidelines.NEW & NOTEWORTHY Occupational exposure limit guidelines using wet bulb globe temperature (WBGT) distinguish between acclimatized and unacclimatized workers with about a 3°C difference between them. For the first time, empirical data from two laboratories provide support for acclimatization state adjustments. Using a constant difference rather than increasing differences with metabolic rate better describes the limit for unacclimatized participants. Furthermore, the lower upper limit of the prescriptive zone (ULPZ) values set forth for women do not relate to fitness level but are partly explained by their smaller body surface area (BSA). An examination of individual ULPZ values suggests that many unacclimatized individuals should be able to sustain safe work at the exposure limit for acclimatized workers.

Demystifying energy savings from dynamic temperature setpoints under weather and occupancy variability

Building temperature setpoints affect both HVAC energy consumption and occupant comfort. To reduce HVAC energy usage, researchers often investigate how system operations can be optimized under weather and occupancy variability subject to a fixed setpoint that minimizes any possible discomfort. While previous research has explored the selection of dynamic setpoints to minimize HVAC energy consumption based on outdoor temperature, they have often neglected the impact of varying occupancy rates on the setpoints. This paper aims to demystify energy savings derived from fixed and dynamic temperature setpoints under weather and occupancy variability and explores the additional energy savings that can be achieved through dynamic temperature setpoints. An exhaustive HVAC zone temperature setpoint optimizer was developed to determine dynamic setpoints with respect to weather and occupancy (i.e., setpoints that minimize HVAC energy consumption at different occupancy rates based on outdoor weather). U.S. DOE reference building energy models for small, medium, and large office buildings were simulated at 17 climate zones, 4 occupancy rates (25%, 50%, 75%, 100%) and 7 setpoints (19.5°C to 25.5°C at 1°C interval). It was found that, both fixed and dynamic setpoints benefit from the energy reduction of approximately 2-4% from the lower heat generated by the occupants at lower occupancy rates. However, at outdoor temperatures between 5°C and 32°C where occupant heat loads can swing the building between heating, free-running, and cooling modes, dynamic setpoints yield additional 2-10% energy savings, compared to fixed setpoints.

Impact of climate change and heat stress on workers’ health and productivity: A scoping review

There are indications that heatwaves will be intensified in duration, frequency and magnitude and will pose threats to the livelihoods and health of the global working population. The purpose of this scoping review was to map evidence regarding occupational heat stress risk factors, their impact on workers’ health and productivity, and potential adaptation measures. Keywords reflecting climate change, heat stress, health, productivity and adaptation strategies were used for searches in PubMed, PubMed Central, Scopus and Web of Science. Manuscripts that focused on heat adaptation, health and productivity outcomes of heat exposure among working populations were considered eligible for this review, while reviews, preprints and papers focused on the general population were excluded. The evidence suggests that gender, age, pre-shift dehydration, piece-rate payment, poor access to sanitation facilities, use of inappropriate personal protective equipment, physically demanding work, high workload, low job control, and high temperatures are risk factors for heat-related illness, dehydration, kidney diseases and mental distress. Specific working populations including migrants, pregnant women, and children were found to be extremely vulnerable to heat stress. The review identified that frequent intake of fluids, resting under shade or in cooling facilities, changing work hours, and increased electrolyte intake were used as adaptation measures. Measures targeting adequate hydration, self-pacing, work-rest regimes, provision of shade and appropriate sanitation facilities need to be matched with improved psychosocial work conditions such as optimal work hours, job autonomy and control, and social supports to ensure safe working conditions in changing climates.

#2758 AMBIENT HEAT EXPOSURE AND ESTIMATED GLOMERULAR FILTRATION RATE TRAJECTORY: A POST-HOC ANALYSIS OF THE DAPA-CKD TRIAL

Abstract Background and Aims Higher ambient temperatures have been associated with higher rates of admission for kidney stones and acute kidney injury. Occupational heat stress is also a risk factor for impaired kidney function in several rural resource-poor settings. It is unclear if higher ambient heat exposure is associated with a faster loss of kidney function in patients with established, all-cause, chronic kidney disease (CKD). We therefore undertook a post-hoc analysis of the DAPA-CKD trial linking participant data to publicly available climate measurements. Method The DAPA-CKD trial randomized 4304 patients with proteinuric CKD (estimated glomerular filtration rate, eGFR, 25-75 mL/min/1.73 m2; urine albumin-to-creatinine ratio, ACR, 23-566 mg/mmol) to dapaglifozin or placebo in addition to standard of care. We examined the association between daily study centre-level ambient heat exposure (defined as a mean heat index, HI, >30; European Centre for Medium-Range Weather Forecasts ERA5 reanalysis dataset) and individual-level change in eGFR using both a linear-mixed effects model and a case-time series approach to address potential unmeasured individual- and centre-level confounding. Results Climate and eGFR data were available on 3915 (91%) participants across 361 centres in 21 countries. Over a median of 28 months, participants (mean age: 62 years; mean eGFR: 43mL/min/1.73 m2) were followed-up at centres where there was a median of 1 day (interquartile range: 0 to 64 days) with an HI>30. Each 30-day period of HI>30 over the study period was associated with a change in eGFR of -0.7% (95% CI: -1.0% to -0.3%), equivalent to an additional eGFR loss of between 1.2 and 4.0mL/min/1.73 m2 per year in a patient with an eGFR of 45mL/min/1.73 m2 located in a very hot versus temperate environment. Similar estimates were obtained using the case time series approach. This association persisted after adjustment for potential haemoconcentration effects on the day of testing and further analyses provided no evidence that these findings varied with baseline eGFR, albuminuria or randomised treatment arm (Figure 1), or by high- versus middle-income country study centre location. Conclusion Higher ambient heat exposure is associated with a more rapid decline in kidney function among patients with CKD. Efforts to mitigate heat exposure should be prospectively tested as part of a comprehensive strategy to slow the progression of kidney disease.

A Comprehensive Review on Hot Ambient Temperature and its Impacts on Adverse Pregnancy Outcomes.

High workplace/ambient temperatures have been associated with Adverse Pregnancy Outcomes (APO). Millions of women working in developing nations suffer due to the rising temperatures caused by climate change. There are few pieces of research linking occupational heat stress to APO, and fresh evidence is required. We used databases including PubMed, Google Scholar, and Science Direct to search for research on high ambient/workplace temperatures and their effects. Original articles, newsletters, and book chapters were examined. The literature we analysed was categorised as follows: Heat, strain, and physical activity harming both mother and fetus. After categorising the literature, it was examined to identify the major results. We found a definite association between heat stress and APOs such as miscarriages, premature birth, stillbirth, low birthweight, and congenital abnormalities in 23 research articles. Our work provides important information for future research into the biological mechanisms that create APOs and various prevention measures. Our data suggest that temperature has long-term and short-term effects on maternal and fetal health. Though small in number, this study stressed the need for bigger cohort studies in tropical developing countries to create evidence for coordinated policies to safeguard pregnant women.

Migrants from Low-Income Countries have Higher Heat-Health Risk Profiles Compared to Native Workers in Agriculture

The present observational study was conducted to uncover potential differences in the risk of experiencing high occupational heat strain during agriculture work between migrants and their native coworkers, as well as to elucidate the factors that may contribute to such differences. The study took place over the period from 2016 through 2019 and involved monitoring 124 experienced and acclimatized individuals from high-income (HICs), upper-middle-income (UMICs), as well as lower-middle- and low-income (LMICs) countries. Baseline self-reported data for age, body stature, and body mass were collected at the start of the study. Second-by-second video recordings throughout the work shifts were captured using a video camera and were used to estimate workers’ clothing insulation, covered body surface area, and body posture, as well as to calculate their walking speed, the amount of time they spent on different activities (and their intensity) and unplanned breaks throughout their work shifts. All information derived from the video data was used to calculate the physiological heat strain experienced by the workers. The core temperature of migrant workers from LMICs (37.81 ± 0.38 °C) and UMICs (37.71 ± 0.35 °C) was estimated to be significantly higher compared to the core temperature of native workers from HICs (37.60 ± 0.29 °C) (p < 0.001). Moreover, migrant workers from LMICs faced a 52% and 80% higher risk for experiencing core body temperature above the safety threshold of 38 °C compared to migrant workers from UMICs and native workers from HICs, respectively. Our findings show that migrant workers originating from LMICs experience higher levels of occupational heat strain, as compared to migrant workers from UMICs and native workers from HICs, because they take fewer unplanned breaks during work, they work at a higher intensity, they wear more clothing, and they have a smaller body size.

Working in heat: Contrasting heat management approaches among outdoor employees and contractors

Exposure to high heat and humidity in the workplace is a critical health and safety issue. In Australia, where heat waves are occurring with more frequency and intensity the risks posed by occupational heat exposure have been acknowledged by employer groups, trade unions, and statutory government agencies. In this study we investigate the employment context in which heat stress is experienced, and whether the mode of employment affects the capacity to manage it. We examine the experience of workplace heat exposure for two groups of affected outdoor workers: contracted pieceworkers in bicycle delivery and permanently employed municipal workers in parks and road maintenance. Data was collected in Sydney during the summer of 2019 via surveys and in-person interviews with the two sets of workers. Research findings reflect the well-established nexus between outside temperature, humidity and work effort in producing heat stress. The comparative findings reveal that more secure forms of employment enable social organisation and workflow to manage heat stress and that, conversely, more contingent forms of employment such as contractual piece work can exacerbate exposure. The research demonstrates that the mode of employment has a direct bearing on the capacity to address workplace heat stress: growth in contract or ‘gig’ work may exacerbate impacts; this issue is likely to become more important with advancing climate change.

Hydration as a modulator of renal vascular control during physical work in the heat

Occupational heat stress increases the risk of developing kidney injury (KI), which is due to the development of hyperthermia and/or hypohydration. It is speculated that this KI is caused by a relative mismatch in oxygen supply (i.e., reductions in renal perfusion) and demand (due to increased sodium reabsorption) in the renal tubules. That said, the modulatory role of hydration on renal vascular control during physical work in the heat is largely unknown. Recent observations indicate that ad lib drinking largely prevents hypohydration during simulated occupational heat stress. Thus, we tested the hypothesis that, compared to ad libitum drinking, fluid restriction induces a pro-vasoconstrictor state in the renal vasculature during physical work in the heat.On two occasions, six healthy adults (1 woman) completed 2 h of exercise in a wet bulb globe temperature of 30±0°C, conditions that are commonly experienced by U.S. outdoor workers. Exercise consisted of completing eight circuits involving treadmill walking (10 min) and rowing (5 min) at a workload eliciting an oxygen uptake of 1.2 L/min, the work intensity observed during agriculture work. In the drinking trial (Drink), subjects were provided 237 mL of sport drink every 15 min and drank ad libitum, which is compliant with workplace hydration recommendations. In the fluid restriction trial (NoDrink), no fluid was provided. Rectal temperature and body mass loss were recorded in each trial. Blood pressure and right renal segmental blood velocity (BV, Doppler ultrasound) was measured before, and following 60 and 120 min of exercise. Before and following exercise, a cold pressor test (CPT) was used to assess the renal vasoconstrictor response to sympathetic activation by immersing the subject’s foot in an agitated ice slurry for 2 min. Blood pressure and segmental BV were measured during each minute of the CPT. Segmental artery vascular resistance (VR) was calculated as mean arterial pressure divided by segmental BV. Data presented as mean ± SD.Average rectal temperature was not different between Drink (37.8±0.4°C) and NoDrink (37.9±0.4°C, p=0.517). Body mass loss was greater in NoDrink (3.1±0.7%) vs. Drink (1.8±0.8%, p=0.014). Segmental BV did not change differently between trials (interaction: p=0.651). Segmental VR did not differ between trials before (Drink: 2.7±0.6, NoDrink: 2.5±0.6 mmHg/cm/s) or after 60 (Drink: 2.8±0.7, NoDrink: 2.6±0.6 mmHg/cm/s) and 90 (Drink: 2.5±0.3, NoDrink: 2.3±0.8 mmHg/cm/s) min of exercise (interaction: p=0.988). Peak increases in segmental VR during the CPT did not differ between trials before (Drink: 0.5 ± 0.7, NoDrink: 0.9 ± 0.6 mmHg/cm/s) or after (Drink: 0.4 ± 0.7, NoDrink: 0.4 ± 0.6 mmHg/cm/s) exercise (interaction: p=0.405).These findings preliminarily indicate that fluid replacement does not modify renal vascular control during physical work in the heat. NCT: NCT05458843. Supported by: R01OH011528 This is the full abstract presented at the American Physiology Summit 2023 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.

Occupational Heat Stress and Kidney Health in Salt Pan Workers

Work in heat affects millions of workers. Although kidney function in agricultural workers is increasingly researched, nonagricultural studies are scarce. In coastal salt pans, the absence of occupational exposures to pesticides and other toxicants allows assessment of heat stress alone. Seven Indian salt pans were surveyed from 2017 to 2020. Job-specific workload was assessed. Heat stress was characterized as exceeding the wet bulb globe temperature (WBGT)-threshold limit value (TLV) for high and moderate workloads. Preshift and postshift heart rates (HRs), tympanic temperatures, and urine specific gravity (USG) were measured for 352 workers, as were sweat rates (SwR), serum creatinine (SCr), serum uric acid, and urine dipstick. Estimated glomerular filtration rate (eGFR; ml/min per 1.73 m2) was computed. Heat-strain symptoms were assessed using questionnaires. The mean WBGT was 30.5 ± 1.3 °C (summer) and 27.8 ± 1.9 °C (winter). Water intake during the workday was low, median was one Litre, and most workers (87%) exceeded the TLV for heat stress. Dehydration-related symptoms were frequent in those with high-heat stress, as were cross-shift increases in temperature (≥1°C; 15%), a high USG (≥1.020; 28%), and a high SwR (≥1 l/h; 53%). An eGFR of 60 to 89 ml/min per 1.73 m2 was observed in 41% of all workers examined, and 7% had eGFR below 60 ml/min per 1.73 m2. The odds ratio for eGFR<90 ml/min per 1.73 m2 in workers exceeding the TLV, compared to workers below this limit, adjusted for age and gender was 2.9 (95% CI: 1.3-6.4). Workplace interventions to prevent heat stress and dehydration in the salt pans and other at-risk industries are urgently required. The findings strengthen the notion that high-heat stress and limited hydration is a risk factor for kidney dysfunction.