Risk Of Heat Stress Research Articles

Integrating AI and Environmental Analytics for Enhanced Productivity and Safety

In the modern workplace, managing outdoor work schedules has become increasingly challenging due to unpredictable weather conditions. This paper presents an innovative solution that combines real-time weather forecasts with Artificial Intelligence (AI) to create adaptive work schedules. By integrating data from reliable weather sources and analyzing it using machine learning models, we can predict the optimal times for outdoor work, reducing health risks and enhancing productivity. Additionally, we explore the use of the Wet Bulb Globe Temperature (WBGT) index to assess the risk of heat stress and adjust work hours accordingly. Our approach incorporates a dynamic scheduling algorithm that considers factors such as legal work hour limits and the intensity of physical labor. The result is a flexible, AI-powered system that not only ensures worker safety in the face of heat stress but also helps organizations navigate the complexities of climate impact on workforce management. Through this study, our goal is to demonstrate how technology can be leveraged to support a safer and more efficient working environment.

Thermophysiological and Perceptual Responses of Amateur Healthcare Workers: Impacts of Ambient Condition, Inner-Garment Insulation and Personal Cooling Strategy

While personal protective equipment (PPE) protects healthcare workers from viruses, it also increases the risk of heat stress. In this study, the effects of environmental heat stress, the insulation of the PPE inner-garment layer, and the personal cooling strategy on the physiological and perceptual responses of PPE-clad young college students were evaluated. Three levels of wet bulb globe temperatures (WBGT = 15 °C, 28 °C, and 32 °C) and two types of inner garments (0.37 clo and 0.75 clo) were chosen for this study. In an uncompensable heat stress environment (WBGT = 32 °C), the effects of two commercially available personal cooling systems, including a ventilation cooling system (VCS) and an ice pack cooling system (ICS) on the heat strain mitigation of PPE-clad participants were also assessed. At WBGT = 15 °C with 0.75 clo inner garments, mean skin temperatures were stabilized at 31.2 °C, Hskin was 60-65%, and HR was about 75.5 bpm, indicating that the working scenario was on the cooler side. At WBGT = 28 °C, Tskin plateaued at approximately 34.7 °C, and the participants reported "hot" thermal sensations. The insulation reduction in inner garments from 0.75 clo to 0.37 clo did not significantly improve the physiological thermal comfort of the participants. At WBGT = 32 °C, Tskin was maintained at 35.2-35.7 °C, Hskin was nearly 90% RH, Tcore exceeded 37.1 °C, and the mean HR was 91.9 bpm. These conditions indicated that such a working scenario was uncompensable, and personal cooling to mitigate heat stress was required. Relative to that in NCS (no cooling), the mean skin temperatures in ICS and VCS were reduced by 0.61 °C and 0.22 °C, respectively, and the heart rates were decreased by 10.7 and 8.5 bpm, respectively. Perceptual responses in ICS and VCS improved significantly throughout the entire field trials, with VCS outperforming ICS in the individual cooling effect.

Increased moist heat stress risk across China under warming climate

Heatwaves have afflicted human health, ecosystem, and socioeconomy and are expected to intensify under warming climate. However, few efforts have been directed to moist heat stress (MHS) considering relative humidity and wind speed, and moist heat stress risk (MHSR) considering exposure and vulnerability. Here we showed MHS and MHSR variations across China during 1998–2100 using China Meteorological Administration Land Data Assimilation System datasets, the 6th Coupled Model Intercomparison Project (CMIP6) merged datasets, Gross Domestic Product, population and leaf area index. We detected increased MHS across China under different Shared Socioeconomic Pathways (SSPs). Specifically, the historical MHS occurred mostly during mid-July to mid-August. We found increasing trends of 0.08%/year, 0.249%/year, and 0.669%/year in the MHS-affected areas under SSP126, SSP245, and SSP585, respectively. Furthermore, we observed the highest increasing rate of MHSR in Northwest and Southwest China, while the MHSR across Northeast and North China under SSP126 shifted from increasing to decreasing trends. Noteworthy is that the increasing trend of MHSR under SSP585 is 1.5–2.6 times larger than that under SSP245, especially in North and South China. This study highlights spatiotemporal evolutions of MHS and MHSR and mitigation to moisture heat stress in a warming climate.

Enlightenment from mitigation of human-perceived heat stress risk in Southwest China during the period 1961–2019

With the effects of climate change, people are increasingly facing human-perceived heat stress (HPHS), which describes the combined effects of high temperature, high humidity, and low surface wind speed. HPHS has a significant impact on industrial and agricultural production, people's lifestyles, and public health. However, the characteristics of HPHS with respect to changes and influencing factors have not been fully investigated using dynamic classification of urban, suburban, and rural stations based on absolute and relative thresholds of seven HPHS indices in Southwest China. The results of this study revealed that, first, during the period 1961–2019, the normal annual and seasonal HPHS values and extreme HPHS days increased significantly, while the extreme HPHS values for the seven HPHS indices decreased. Second, based on the absolute and relative thresholds, the frequency and intensity of the impact of urbanization differed in four regions, and in Yunnan and Guizhou in particular. Different HPHS indices and different dynamic station classification methods result in different estimations of the effects of urbanization on annual and seasonal changes in the regional climate. Therefore, choosing an appropriate dynamic station classification method and considering the applicability of different indices in different seasons in different regions is very important. Third, the Granger causality test shows that the percentage of stations with Granger causality between landscape composition indices and seven extreme HPHS is the highest among all influencing factors. At the same time, boosted regression tree detection also showed that the landscape composition indices had the highest contribution percentage to the seven extreme HPHS. Therefore, rational planning of land-use patterns, especially in relation to urban forest land, grassland, wetland, and water bodies (including vertical landscape composition, configuration planning, and building density and layout) has implications for the realization of the United Nations Sustainable Development Goals (SDGs), in particular SDG 11, Sustainable Cities and Communities.

Relationship between Reticulorumen Parameters Measured in Real Time and Methane Emission and Heat Stress Risk in Dairy Cows.

The objective of this study was to investigate a connection between CH4 emissions and reticulorumen pH and temperature. During the experiment, we registered the following parameters: reticulorumen pH (pH), reticulorumen temperature (RR temp.), reticulorumen temperature without drinking cycles, ambient temperature, ambient relative humidity, cow activity, heat index, temperature-humidity index (THI), and methane emissions (CH4). The experimental animals were divided into two groups based on the reticulorumen pH: 1. pH < 6.22 and 2. pH 6.22-6.42. We found that cows assigned to the second pH class had higher (46.18%) average values for methane emissions (p < 0.01). For the other indicators, higher average values were detected in cows of the first pH class, RR temperature (2.80%), relative humidity (20.96%), temperature-humidity index (2.47%) (p < 0.01), and temperature (3.93%) (p < 0.05), which were higher compared to cows of the second pH class. Reticulorumen pH was highly negatively correlated with THI and temperature (r = -0.667 to 0.717, p < 0.001) and somewhat negatively with heat index, relative humidity, and RR temperature (r = -0.536, p < 0.001; r = -0.471 to 0.456, p < 0.01). Cows with a higher risk of heat stress had a higher risk of lower reticulorumen pH.

A Multi-Segmented Human Bioheat Model for Asymmetric High Temperature Environments.

In workplaces such as steel, power grids, and construction, firefighters and other workers often encounter non-uniform high-temperature environments, which significantly increase the risk of local heat stress and local heat discomfort for the workers. In this paper, a multi-segment human bioheat model is developed to predict the human thermal response in asymmetric high-temperature environments by considering the sensitivity of the modeling to angular changes in skin temperature and the effects of high temperatures on human thermoregulatory and physiological responses simultaneously. The extended model for asymmetric high-temperature environments is validated with the current model results and experimental data. The result shows that the extended model predicts the human skin temperature more accurately. Under non-uniform high-temperature conditions, the local skin temperature predictions are highly consistent with the experimental data, with a maximum difference of 2 °C. In summary, the proposed model can accurately predict the temperature of the human core and skin layers. It has the potential to estimate human physiological and thermoregulatory responses under uniform and non-uniform high-temperature environments, providing technical support for local heat stress and local thermal discomfort protection.

Environmental injustice among Hispanics in Santa Clara, California: a human–environment heat vulnerability assessment

In the United States, there is a growing interest in understanding heat stress in lower-income and racially isolated neighborhoods. This study spatially identifies heat-vulnerable neighborhoods, evaluates the relationship between race/ethnicity and temperature exposure, and emphasizes differences among Hispanics by origin to capture environmental injustices in Santa Clara County (SCC), CA. The current methodology uses Landsat 8 via Google Earth Engine to measure the Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) to assess the physical environment. The human environment is evaluated using the Modified Darden-Kamel Composite Socioeconomic Index to determine the spatial variability of socioeconomic status (SES) and the Index of Dissimilarity to determine the level of segregation between Hispanics and non-Hispanic Whites and among Hispanics/Latinos. The combination of these assessments comprises a comprehensive human–environment approach for health exposure evaluation by which to define environmental injustice. Results reveal socioeconomic inequalities and an uneven residential distribution between Hispanics and non-Hispanic Whites. Low NDVI and high LST values were found in Mexican neighborhoods, implying possible environmental racism. Almost half the Mexican population lives in highly segregated neighborhoods with low and very low SES, mainly located in East San Jose, where, historically, they have been ghettoized. Mexicans, in general, could be at a higher risk of heat stress and heat mortality during heat waves. Future work should examine additional variables (e.g., housing characteristics, crime, social cohesion, and collective behaviors) to comprehensively evaluate the at-risk Mexican population.

Nest microclimate and heat stress in African Penguins Spheniscus demersus breeding on Bird Island, South Africa

Summary Low-latitude penguins naturally breed in burrows dug in guano. This affords them a buffered environment that remains cool and humid, reducing the risk of hyperthermia while on land. As a conservation strategy, several versions of artificial housing units have been trialled at various breeding sites of African Penguins (Spheniscus demersus) around South Africa, where former guano exploitation forced many penguins to breed in exposed surface nests. While some units yielded a positive effect on breeding success by providing protection against predation, none of them have effectively mitigated the risk of heat stress in penguins or their eggs. Here, we investigated the microclimate of a recent double-layered design of ceramic artificial nests and compared that to natural burrows, exposed surface nests, and commonly used cement pipe nests, in austral summer 2021 on Bird Island, South Africa. We also recorded penguin behaviour during the hottest period at each of these nest types using remote camera traps to determine the onset of heat stress (panting). Double-layered ceramic nests out-performed all other nest types, including natural burrows, by remaining cooler throughout the day, with temperatures never exceeding 36.7°C. By contrast, all other nest types had multiple episodes where temperatures exceeded 40°C. Double-layered ceramic nests also maintained constant levels of high humidity (relative humidity [RH] >70%) throughout our study, whereas low humidity levels were observed in surface nests (RH ≈ 60%) and cement nests (RH <50%) during midday heat. We observed penguins panting at temperatures of 25°C in nest boxes, and at 22°C in exposed surface nests. This suggests that heat stress in African Penguins may occur much sooner than anticipated and that they are particularly vulnerable to hyperthermia as climate change-related global warming progresses. Fortunately, we are encouraged by the capacity of double-layered ceramic nest boxes to buffer environmental extremes and maintain suitable breeding conditions.

The effect of afforestation on moist heat stress in Loess Plateau, China

Study regionLoess Plateau (LP), China Study focusThis study aimed to research whether and to what degree afforestation contributes to the variations in moist heat stress in the study area. Here, wet bulb, temperature (Tw) was used to quantify the moist heat stress. Subsequently, The Weather Research and Forecasting model (WRF) is applied to simulate the modulation of climate change related to afforestation during 2001–2015. Based on the analysis of energy fluxes, we identified the biogeophysical mechanism of afforestation impact on moist heat stress. New hydrological insights for the regionSince the operation of the “Grain-to-Green” program, LP has experienced widespread afforestation which perturbs energy and water fluxes, affecting regional climate regimes. The forest expansion increases relative humidity but cools the regional temperature. As a significant combined climate factor, the average moist heat stress decreases with the magnitude of − 0.1∼− 0.3 °C in central LP. While the decrease rate of Tw is slower than near-surface temperature. It is worth noting that, an increased signal occurs in the maximum Tw (almost 0.2 °C in eastern and northeastern LP), which might expose humans to the risk of moist heat stress. By the mechanistic analysis, the research shows that the near-surface temperature and sensible heat flux are dominant driving factors for the change of Tw. Furthermore, the subsidence of the planetary boundary layer enhances moist heat stress. Overall, afforestation’s effects on land surface-atmosphere interaction are non-negligible and the moist heat stress should be accounted for in climate change adaptation strategies.

Application of machine-learned metadata-driven model for dairy barn ventilation simulation

As US dairy operations consolidate to meet an increasing demand for dairy products, dairy producers have begun to seek more economically efficient dairy-barn designs and ventilation systems to combat the pernicious effects of heat stress. The metabolic changes that heat stress induces not only put the animals at risk of serious illness but also diminish the herd’s productivity. Lactation, being a metabolic process, generates a great deal of body heat thereby increasing the risk of heat stress during warm weather, and that risk increases when the animals commingle in an enclosed space. For this reason, predicting heat stress and estimating its severity have taken on special importance. Recently, producers and barn builders have contended with the conditions that promote heat stress by implementing closed mechanical ventilation systems. However, if a proposed ventilation system’s performance was not accurately predicted, the system would not work effectively or efficiently. The traditional ways of assessing ventilation performance, which involved either hand-held sensors or stationery sensing monitors, tended to be time-consuming and the larger the barn the more labor-intensive. Additionally, the complex microenvironmental system that exists inside a dairy barn is further complicated by the myriad moving elements, both animals and operational machines. Given these complicating parameters, researchers have lately turned to computation fluid dynamics (CFD) when analyzing such environments because, once properly validated, CFD can accurately predict the heat and mass transfer occurring at any location inside a computer-generated model of a dairy barn. However, operating CFD correctly requires not only an extensive background knowledge and a significant amount of hands-on experience, but also high-end hardware, which is often unavailable to dairy operators and non-CFD--experts. This study proposed CFD-ML, a machine-learning (ML) based “simulator,” as a means to achieving computational predictions that are accurate enough to use as a basis for dairy-barn design. A convolutional neural network (CNN), a representative ML model, allows complex mapping between input barn geometry and the velocity and temperature fields occurring in the barn, resulting in faster prediction time and simpler usage processes. As a result, the CFD-ML model can achieve outcomes comparable to those obtained using CFD, with R2 values greater than 0.85, in far less computing time required by CFD. This finding should provide a foundation that could facilitate future CFD-ML advances in dairy science research as well as the development of a user-friendly Graphical User Interface (GUI) that bypasses the complex CFD procedures.

The relationship between on-farm environmental conditions inside and outside cow sheds during the summer in England: can Temperature Humidity Index be predicted from outside conditions?

Heat stress is a growing problem in dairy cows, and interest is developing in calculating heat stress risk (Temperature Humidity Index – THI) without using specific farm data and in forecasting THI changes a few days in advance. Previous workers have shown that calculating THI values inside cattle sheds using data from local Meteorological Stations is not sufficiently accurate. Weather forecasting is becoming more local and can forecast on-farm temperature and humidity. This work looked at how well THI inside a cow shed could be predicted from data collected outside the cow shed on British farms. Six farms were monitored from 1 May 2021 to 30 Sept 2021 using bespoke data monitors that uploaded the data to the cloud in real time through the cellular network. Calculated THI values for inside and outside the cow shed were highly correlated (P < 0.001), and a regression predicting THI inside the shed from the THI outside the shed was highly significant (P < 0.001). However, farm-specific regressions had significantly different regression intercepts. Including calving pattern type (autumn or all year round) and calendar month separately or together improved the regression. The 95% confidence interval (CI) of the prediction was 10.8 THI units for the simple one-component model (THIoutside) and 7.8 for the three-component model (THIoutside, calendar month, calving pattern type). Farm-specific regressions had the lowest CI values suggesting there are farm-specific factors affecting THI that had not been captured. As a predictive model, the simple single component regression would be the most applicable but the relatively high CI means that predictions will not be that accurate with the risk of heat stress either under- or overemphasised on different farms. With one THI unit equating to approximately a 200 ml drop in milk yield in heat-stressed cows, such errors will be of biological and commercial significance. This in part may be due to the THI equation only considering temperature and humidity and ignoring solar radiation, shade, wind and animal factors such as milk yield, stage of pregnancy, weight and genetic variability. Further work is underway to develop an index that quantifies how the cow is responding to the combined heat-loading factors which may improve the prediction of heat stress.

Climate‐driven thermal opportunities and risks for leaf miners in aspen canopies

AbstractIn tree canopies, incoming solar radiation interacts with leaves and branches to generate temperature differences within and among leaves, presenting thermal opportunities and risks for leaf‐dwelling ectotherms. Although leaf biophysics and insect thermal ecology are well understood, few studies have examined them together in single systems. We examined temperature variability in aspen canopies, Populus tremuloides, and its consequences for a common herbivore, the leaf‐mining caterpillar Phyllocnistis populiella. We shaded leaves in the field and measured effects on leaf temperature and larval growth and survival. We also estimated larval thermal performance curves for feeding and growth and measured upper lethal temperatures. Sunlit leaves directly facing the incoming rays reached the highest temperatures, typically 3–8°C above ambient air temperature. Irradiance‐driven increases in temperature, however, were transient enough that they did not alter observed growth rates of leaf miners. Incubator and ramping experiments suggested that larval performance peaks between 25 and 32°C and declines to zero between 35 and 40°C, depending on the duration of temperature exposure. Upper lethal temperatures during 1‐h heat shocks were 42–43°C. When larvae were active in early spring, temperatures generally were low enough to depress rates of feeding and growth below their maxima, and only rarely did estimated mine temperatures rise beyond optimal temperatures. Observed leaf or mine temperatures never approached larval upper lethal temperatures. At this site during our experiments, larvae thus appeared to have a significant thermal safety margin; the more pressing problem was inadequate heat. Detailed information on mine temperatures and larval performance curves, however, allowed us to leverage long‐term data sets on air temperature to estimate potential future shifts in performance and longer‐term risks to larvae from lethally high temperatures. This analysis suggests that, in the past 20 years, larval performance has often been limited by cold and that the risk of heat stress has been low. Future warming will raise mean rates of feeding and growth but also the risk of exposure to injuriously or lethally high temperatures.

Effect of distance and daily periods on heat-stressed pigs and pre-slaughter losses in a semiarid region.

Effective planning animal transport is essential to safeguard animal welfare and reduce production losses. Environmental conditions, specifically extreme temperatures in combination with ranges of relative humidity are highlighted as one of the main risk factors for production losses during transport (e.g., fatalities). The majority of research evaluating both welfare and production impacts of pig transport have been primarily undertaken in Europe and North America, which cover a relatively limited range of distinct climates (e.g., temperate, sub-arctic, etc.). As a result, research on pig transport in semi-arid conditions is lacking. In this study, we evaluated the effects of bothdistance (short, 30km; and long, 170km) and transport daily periods (morning, (05:00-11:00); afternoon (12:00-17:00); and night, (23:00-04:00)) on the preslaughter losses and heat stress of pigs in commercial transport in a semiarid region. Across 19 journeys of standard slaughter-weight pig loads (124.0 ± 2.8kg), 684 focal animals (36 per journey) were evaluated. For each journey, the load's thermal profile (THIadj and enthalpy) and physiological responses of individualpigs were recorded. On arrival at designatedslaughterhouses, the percentage pig of non-ambulatory non-injured (NANI), non-ambulatory injured (NAI), death on arrival (DOA), and total losses were recorded. Short journeys in the afternoon were shown to be more detrimental to the thermal comfort of pigs, with higher rectal temperatures recorded.The highest percentage of total losses and DOA occurred in afternoon journeys, irrespective of distance,followed by the morning, with the lowest losses observed in pigs transported at night. Additionally, total losses and DOA were further exacerbated by journey distance, with higher rates observed in short journeys. Higher percentage averages of NANI and NAI were observed in shorter journeys, but daily periods effects were only observed for NANI. These results further demonstrate the welfare and production loss risks associated with journey distance and time of day (representing varying environmental conditions) during road transport of pigs, whilst providing novel data in semiarid conditions. Carefuland effective planning for pig transportationis essential to minimize heat stress and production losses. Consideration of the thermal environment on the day of travel, as well as providing flexibility to adjust travel times (e.g., early morning or evening), should help to mitigate risks of heat stress and production losses during pig transport.

Evaluation of Environmental Heat Exposure, Heat-related Symptoms, and Acute Physiological Changes among Farmers in Pasir Puteh and Bachok, Kelantan

Prolonged or intense exposure to heat can lead to a range of health effects. This study evaluated environmental heat exposure, heat-related symptoms, and acute physiological changes among 39 farmers in Kelantan, Malaysia. During the end of the monsoon season in February to Mac 2019, wet bulb globe temperature (WBGT) was collected in the farm environment to assess heat exposure. Blood pressure, heart rate, and body core temperature were measured pre-, mid and post-shift to measure the physiological response of farmers towards environmental heat. Sociodemographic, occupational information and heat-related symptoms that subjects had experienced were gathered using a questionnaire. The WBGT outdoor showed a high risk for heat stress and strain (&gt; 28.0 oC) based on the American Conference of Governmental Industrial Hygiene (ACGIH) threshold limit values (TLVs). More than half (50%) of farmers reported heat-related symptoms including fatigue, lethargy, dizziness, rashes, and cramps. Significant physiological changes including heart rate, body temperature, and systolic blood pressure occurred across the work shift (p &lt;0.05). However, no significant association (p&gt;0.05) was found between the Acute Health Symptoms score (AHSS) with associated factors, thus no statistical model was further developed. In conclusion, farmers experienced significant psychological changes across the work shift. Preventive and control measures for heat stress are needed to reduce the risk of heat strain.

Effects of the moisture barrier and thermal liner components on the heat strain and thermal protective performance of firefighter turnout systems

An ideal firefighter turnout system should be capable of releasing body heat to prevent heat stress, indicated by THL (total heat loss) and Ref (evaporative resistance) indexes, while maintaining high thermal protective performance (TPP). Our study found no correlations between THL and Ref, or between Ref and TPP. The results showed that, when tested in the mild condition as in the standard THL test method, turnout systems with bi-component moisture barriers exhibited an advantage in THL that did not translate to more thermally stressful hot environments. A physiological manikin was used to understand the effect of turnout clothing systems on heat strain in different environmental conditions and the value of utilizing Ref or THL to predict heat strain performance. We found no difference in heat strain performance between composites with one-layer and two-layer spunlace thermal liners in mild or hot conditions. It showed that both THL and Ref had their limitations: THL only predicted thermal burden in mild environments, while Ref was only correlated in hot conditions. Thus, the exclusive reliance on either index could increase the risk of heat stress, and we recommend incorporating the Ref heat strain index, along with THL, as dual metrics for certifying the heat strain performance of turnout suits in the NFPA 1971 standard.

Heat Stress More Negatively Impacts Cardiac Muscle Mitochondria in Female Versus Male Pigs

With continued trends toward more frequent and more severe heat events there is a greater risk of environment‐induced heat stress (HS). How persistently elevated core temperatures impacts body tissues remains largely unknown. Our preliminary evidence indicates HS may negatively impact cardiac tissue and that biological sex may play a role in HS‐mediated pathology. To further test the hypothesis that cardiac muscle mitochondria are more negatively impacted by HS in females than in males, samples were isolated from the left ventricle (LV) of the heart from 3‐month‐old castrated male and prepubertal female pigs that were exposed to thermoneutral (TN) conditions (n = 4 per sex) or HS conditions for 24 h at 37°C (HS; n = 6 per sex). Samples were analyzed for citrate synthase (CS) and cytochrome c oxidase (COX) activities, and for mitochondrial oxidative phosphorylation (P) and electron transfer (E) capacities via high resolution respirometry. Data were analyzed by mixed linear models in SAS v9.4 with treatment, sex, and treatment × sex as fixed effects. A traditional marker of mitochondrial volume density, CS activity, tended to be greater in TN males compared to HS males (P = 0.08) but was unaffected by HS in female pigs. Conversely, intrinsic (relative to CS activity) mitochondrial function, as measured by COX activity, was greater in TN females than HS females (P = 0.04) and within HS, males maintained greater intrinsic mitochondrial function than females (P = 0.02). Both integrative (relative to tissue wet weight) and intrinsic mitochondrial leak respiration were greater in HS than TN pigs (P = 0.03) but the contribution of leak to total E (flux control ratio; FCRLEAK) tended to be greater in males than females (P = 0.07). Conversely, both integrative and intrinsic maximal E (ECI+II) tended to be greater in female than male pigs (P = 0.08) indicating a greater degree of excess electron transfer capacity in females. The contribution of complex I‐supported P (PCI) to total E (FCRPCI) tended to be greater in TN compared to HS pigs regardless of sex (P = 0.09) and the contribution of maximal P to E (FCRPCI+II) was greater in TN females compared to HS females (P = 0.05). This resulted in the FCRPCI+IIbeing greater in males compared to females in the HS condition (P = 0.01), suggesting greater coupling of oxidative phosphorylation and electron transfer in cardiac mitochondria in males during 24 h of HS. These results suggest that HS may negatively impact cardiac muscle mitochondria in female pigs compared to males. Moreover, these data indicate that persistent HS has deleterious consequences for the myocardium and may represent an additional health concern caused by global climate trends. This project was supported by USDA NIFA Award #2020‐68014‐31954.

Increased heat stress risk for maize in arid-based climates as affected by climate change: threats and solutions

Heat stress in combination with drought has become the biggest concern and threat for maize yield production, especially in arid and hot regions. Accordingly, different optimal solutions should be considered in order to maintain maize production and reduce the risk of heat stress under the changing climate. In the current study, the risk of heat stress across Iranian maize agro-ecosystems was analyzed in terms of both intensity and frequency. The study areas comprised 16 provinces and 24 locations classified into five climate categories: arid and hot, arid and temperate, semi-arid and hot, semi-arid and temperate, and semi-arid and cold. The impact of heat stress on maize under a future climate was based on a 5-multi-model ensemble under two optimistic and pessimistic emission scenarios (RCP4.5 and RCP8.5, respectively) for 2040-2070 using the APSIM crop model. Simulation results illustrated that in the period of 2040-2070, intensity and the frequency of heat stress events increased by 2.37°C and 79.7%, respectively, during maize flowering time compared to the baseline. The risk of heat stress would be almost 100% in hot regions in the future climate under current management practices, mostly because of the increasing high-risk window for heat stress which will result in a yield reduction of 0.83 t ha-1. However, under optimal management practices,farmers will economically obtain acceptable yields (6.6 t ha-1). The results also indicated that the high-risk windows in the future will be lengthening from 12 to 33days in different climate types. Rising temperatures in cold regions as a result of global warming would provide better climate situations for maize growth, so that under optimistic emission scenarios and optimal management practices, farmers will be able to boost grain yield up to 9.2 t ha-1. Overall, it is concluded that farmers in hot and temperate regions need to be persuaded to choose optimal sowing dates and new maize cultivars which are well adapted to each climate to reduce heat stress risk and to shift maize production to cold regions.

Impact of Climate Change on the Labor Market

Greenhouse gases have far-ranging environmental and health effects. They cause climate change by trapping heat and they also contribute to respiratory disease from smog and air pollution. Extreme weather, food supply disruptions, and increased wildfires are other effects of climate change caused by greenhouse gases. In turn, climate change has increased the risk to workers’ health and safety. Workers, especially those who work outdoors or in hot indoor environments, are also at increased risk of heat stress and other heat-related disorders, besides occupational injuries and reduced productivity at work. This article aims at contributing to this discussion by means of qualitative analysis and find out how climate change affects the labor market and its various implications on the workforce.

Earlier crop flowering caused by global warming alleviated by irrigation

Enabling crop flowering within an optimal calendar window minimises long-term risk of abiotic stress exposure, improving prospects for attaining potential yield. Here, we define the optimal flowering period (OFP) as the calendar time in which long-term risk of frost, water and heat stress are collectively minimised. Using the internationally-renowned farming systems model Agricultural Systems Production Systems sIMulator, we characterised combined effects of climate change and extreme climatic events on the OFPs of barley, durum wheat, canola, chickpeas, fababean and maize from 1910 to 2021. We generate response surfaces for irrigated and dryland conditions using a range of representative sowing times for early and late maturity genotypes. Global warming truncated crop lifecycles, shifting forward flowering of winter crops by 2–43 d in dryland environments, and by −6–19 d in environments with irrigation. Alleviation of water stress by irrigation delayed OFPs by 3–25 d or 11–30 d for early and late maturity winter crops, respectively, raising average yields of irrigated crops by 44%. Even so, irrigation was unable to completely negate the long-term yield penalty caused by the climate crisis; peak yields respectively declined by 24% and 13% for rainfed and irrigated crops over the 111 years simulation duration. We conclude with two important insights: (a) use of irrigation broadens OFPs, providing greater sowing time flexibility and likelihood of realising potential yields compared with dryland conditions and (b), the most preferable maturity durations for irrigated winter and summer crops to maximise potential yields are early-sown long-season (late) and later-sown short-season (early) maturity types, respectively.

Physiological Response to Heat Stress in Immune Phenotyped Canadian Holstein Dairy Cattle in Free-Stall and Tie-Stall Management Systems

The climate in northern latitude countries, such as Canada, are changing twice as fast as in lower latitude countries. This has resulted in an increased frequency of hot days and longer more frequent heat waves. Canadian dairy cattle are therefore at increased risk of heat stress, especially those in management systems without the infrastructure to properly cool animals. Cattle experiencing heat stress undergo numerous physiological changes. Previous research has shown dairy cattle classified as high immune responders have lower incidence of disease. Therefore, the objective of this study was to evaluate the variation in respiration rate, rectal temperature, and rumination activity in immune phenotyped dairy cattle during a natural heat stress challenge. Additionally, the relationship between physiological response and temperature humidity index was compared between free-stall and tie-stall management systems. A total of 27 immune phenotyped (nine high, nine average and nine low) lactating dairy cattle were housed in a free-stall during the summer months for a duration of 27 days. Concurrently, two groups of six (three high and three low) immune phenotyped lactating dairy cattle were housed in a tie-stall for a duration of 12 days. Rumination was measured for the duration of the study for all cattle using SCR Heatime rumination collars. Respiration was measured using EMKA respiration bands for cattle housed in the tie-stalls, and manually [once in the morning (a.m.) and once in the afternoon (p.m.)] for cattle in free-stall management. Rectal temperature was measured using a digital thermometer twice daily (a.m. and p.m.) in both free-stall and tie-stall management systems. The temperature humidity index was recorded every 15 min in both management systems for the duration of the study. The results showed that high responders had significantly lower respiration rates compared to low responders when the temperature humidity index was high in both free-stall and tie-stall management systems, but there was no difference in rectal temperature, or rumination activity between phenotypes. Temperature humidity index values in the free-stall were significantly lower than the tie-stall. These findings increase the evidence that high immune responders are more likely to be tolerant to heat stress than low immune responders.