Heatwaves and Occupational Health: Emerging Risks and Adaptive Public Health Strategies Under Climate Change—A Narrative Review

Abstract

Heatwaves, intensified by climate change and urbanization, pose increasing threats to human health, with occupational populations facing disproportionate risks due to prolonged exposure and high metabolic demands. Existing evidence remains fragmented, particularly regarding the integration of acute and chronic health effects in workplace settings. This narrative review synthesizes current knowledge on occupational heat exposure, highlighting emerging risks such as cumulative physiological strain, heat-related chronic diseases, and mental health impacts. We identify key occupational-specific pathways that amplify vulnerability beyond that of the general population. Despite growing awareness, substantial gaps persist in the implementation of effective adaptation strategies, especially in low- and middle-income countries, where regulatory, economic, and structural barriers limit intervention uptake. To address these challenges, we emphasize the need for adaptive work–rest scheduling, dynamic early warning systems, and cross-sectoral collaboration to enhance occupational heat resilience under a changing climate.

1. Introduction

Climate change, characterized prominently by global warming, has emerged as one of the most pressing challenges facing human society today [1]. In recent years, extreme heat and heatwaves have had profound global impacts, affecting regions across Asia, Europe, Africa, and the Americas [2]. The 2024 Lancet Countdown on Health and Climate Change [3] reported that in 2023, the number of days per person exposed to health-threatening heat exceeded projections by 50 days, marking a historic peak in global temperature in the past 100,000 years [4]. In China, the 2024 China Report of the Lancet Countdown on Health and Climate Change: Towards a Low-Carbon Healthy Future [5] noted that the national average temperature in 2023 reached 10.71 °C, which is 0.82 °C higher than the 1981–2010 baseline. Projections suggest that global mean temperature could increase by approximately 2.7 °C above pre-industrial levels (1850–1900 baseline) by 2100, posing severe challenges to climate adaptation capacity [6].

The increasing frequency and intensity of heatwaves [7,8] have become a major threat to public health. According to the 2021 Global Burden of Disease (GBD) study, heat-related mortality accounted for approximately 0.5% of total global deaths [9]. Beyond direct mortality, heatwaves are associated with a broad spectrum of acute, chronic, and mental health outcomes, as well as heightened infectious disease transmission risks, which are discussed in detail in Section 5 and Section 6.

Particularly vulnerable are occupational groups who work under prolonged exposure to high temperatures [10]. In 2018, the U.S. Bureau of Labor Statistics (BLS) reported 49 deaths and 3130 cases of nonfatal heat-related illnesses among workers due to environmental heat exposure [11]. Heatwaves also contribute to productivity loss in labor-intensive industries, posing further socioeconomic burdens [4,12]. Additional consequences of extreme heat include intensified urban heat islands, energy poverty [13], economic losses, health disparities, and disease outbreaks [14,15], all of which severely impact both human well-being and the environment.

Although a growing body of recent studies has advanced the understanding of the spatio-temporal dynamics [16,17], drivers [18], and population-level health impacts [19] of heatwaves at regional and global scales, existing syntheses largely focus on general populations [20,21,22] or climate metrics [23]. While numerous high-quality epidemiological studies have examined heat-related injuries, productivity loss, and economic impacts among outdoor and occupational populations at national or regional levels [24,25,26], and recent perspective and agenda-setting papers have highlighted the importance of occupational health in the context of climate change [27,28], these strands of evidence are rarely integrated across regions or across acute, chronic, and occupational health dimensions. As a result, how occupational exposure characteristics, mechanistic pathways, and systemic constraints jointly shape heat-related health risks—and why existing workplace adaptation strategies often underperform—has not been systematically synthesized within a unified, evidence-based framework.

To address these gaps, this narrative review is guided by three research questions:

• What are the primary physiological mechanisms and health impact pathways through which extreme heatwaves affect occupational populations?
• Why do existing workplace heat adaptation strategies often underperform, and what structural constraints limit their implementation?
• What integrated strategies can enhance occupational heat resilience across diverse climatic, economic, and regulatory contexts?

2. Methodology

This review was conducted as a narrative evidence synthesis supported by a structured literature search strategy. Major scientific databases including Web of Science, PubMed, and Scopus were consulted to identify peer-reviewed studies related to extreme heat, occupational exposure, and health outcomes. The search focused on publications addressing climatic trends, physiological mechanisms, occupational vulnerability, and heat adaptation strategies. Search terms included combinations of extreme heat, heatwave, occupational health, heat stress, heat stroke, occupational exposure, climate change, heat-related illness, workplace adaptation, and heat resilience. Rather than applying formal systematic review procedures, this study aimed to integrate interdisciplinary evidence to synthesize emerging concepts, mechanisms, and policy implications. The included literature was selected to provide representative coverage of epidemiological, mechanistic, and occupational health research across diverse geographic contexts. As a narrative synthesis, the review is subject to selection bias, and this limitation is acknowledged in Section 9.

3. Global and National Trends in the Prevalence of Heatwaves

Since the 1950s, many regions worldwide have experienced notable increases in the duration, intensity, and especially the frequency of heatwaves [29]. Observational records and reanalysis datasets consistently indicate an acceleration of extreme heat events since the mid-1990s, with large-scale heatwaves and associated wildfires reported across Asia, the Americas, Australia, Europe, and Africa between 1995 and 2023 [30,31]. These events reflect a broad intensification of heat exposure at regional and continental scales, although reported metrics and thresholds vary across studies and climatic contexts.

At the international level, several landmark heatwave events illustrate the escalating severity of extreme heat. The 2003 European heatwave resulted in an estimated 70,000 excess deaths across the continent [32]. The 2010 Russian heatwave caused approximately 55,000 excess deaths and was accompanied by devastating wildfires [33]. In 2021, the Pacific Northwest heat dome event in the United States and Canada shattered temperature records, with Lytton, British Columbia, recording 49.6 °C, and was associated with an estimated 1400 excess deaths across the affected region [34]. In the United States, the Bureau of Labor Statistics has documented a long-term upward trend in occupational heat-related fatalities, with outdoor workers in agriculture, construction, and transportation sectors disproportionately affected [35,36].

In China, both the frequency and severity of heatwaves have shown a marked upward trend over recent decades. According to the Fourth National Climate Change Assessment Report: Part I [37], the number of extreme heat days increased significantly between 1961 and 2019, with the average number of warm days rising by approximately 5.7 days per decade. Consistent with these findings, The China Blue Book on Climate Change (2024) [38] reported that the national annual mean surface temperature increased by 0.30 °C per decade between 1961 and 2023, exceeding the contemporaneous global average warming rate. Reports from Meteorological Monthly further document a sustained rise in the frequency of extreme heat events across multiple regions of China [39].

Beyond climatic indicators, recent assessments have highlighted the growing health and economic burden associated with intensifying heatwaves. The 2024 China Lancet Countdown Report on Health and Climate Change [5] estimated that heatwave-related mortality in 2023 increased by 1.9-fold compared with previous years. Potential work-hour losses rose by 24%, and heat-related productivity declines were associated with an estimated economic loss of USD 28.34 billion, equivalent to approximately 1.65% of national GDP. Among the working-age population, direct economic losses attributable to heatwave-related mortality reached USD 61.3 million, representing a 23.1% increase compared with 2022.

Taken together, these findings indicate a sustained escalation of heatwave exposure and associated societal impacts at both global and national scales. This section synthesizes reported trends and burden estimates to contextualize occupational heat risk, rather than providing de novo quantitative modeling of exposure thresholds or population-specific heat strain. Detailed assessment of occupational heat stress metrics and health implications is addressed in subsequent sections.

4. Research Focuses on Heatwaves

4.1. Definition of Heatwaves

Due to the diverse geographical features, climatic conditions, and varying levels of population adaptability across regions, a uniform global definition of heatwaves remains elusive [40]. Generally, heatwaves are described as periods of consecutive days during which the daily maximum temperature meets or exceeds a specified threshold [41]. However, this threshold and duration vary substantially across regions. Current definitions of heatwaves typically consider three key parameters [42]: (1) Temperature metrics, such as daily maximum, minimum, or apparent temperature; (2) Thresholds, including absolute thresholds (e.g., ≥35 °C) or relative thresholds (e.g., the 95th percentile of historical temperatures) [43]. (3) Duration, usually ranging from three to five consecutive days.

Xu et al. emphasized that the selection of appropriate threshold temperatures is essential for heatwave identification and the development of early warning systems [42]. However, there remains no global consensus on the ideal temperature threshold, and most countries adopt region-specific criteria tailored to their climatic and public health contexts. Such heterogeneity in definitions complicates cross-study comparisons of heat-related health and occupational risk estimates.

4.2. Determinants and Drivers of Heatwaves

Since the 1950s, the increasing frequency, intensity, and duration of heatwaves has been predominantly attributed to anthropogenic influence [44]. According to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6), human activities have been the dominant driver of extreme temperature changes at global and continental scales since the mid-20th century [45]. Under high-emissions scenarios, the annual number of heatwave days in certain regions may reach 50 days by the 2090s. To improve analytical clarity, this review distinguishes between synoptic-scale climatic drivers (e.g., large-scale atmospheric circulation and background warming trends) and local-scale modifiers (e.g., urban form, land-use characteristics, and workplace microenvironments), emphasizing that heterogeneous occupational heat exposure arises from the interaction between large-scale meteorological forcing and localized environmental and occupational conditions.

Another critical factor is the urban heat island (UHI) effect [46]. Rapid urbanization exacerbates UHI intensity, and studies suggest that the combined effect of UHI and heatwaves exceeds the additive effect of each phenomenon independently [47,48]. In addition to urbanization, factors such as humidity levels, apparent temperature, and vegetation coverage also modulate the health impact of heatwaves in urban settings [49]. From an occupational health perspective, these local-scale factors function as exposure amplifiers that translate regional heat anomalies into uneven workplace-level thermal burdens.

Moreover, heatwaves often co-occur with other compound extreme climate events, amplifying their overall impact. For example, research by Meng et al. [50] indicates that elevated humidity during humid heatwaves lowers the threshold temperature for heat-related health risks. Additionally, compound drought–heatwave (CDHW) events are increasingly associated with severe wildfires worldwide, causing substantial ecological and economic consequences [51].

5. Health Impacts and Physiological Mechanisms of Heatwaves

It should be noted that long-term epidemiological data specific to occupational populations exposed to sustained heat remain scarce. Much of the evidence presented in this section is derived from general population studies and extrapolated to occupational contexts. Where occupationally specific data are available, they are explicitly identified. This limitation should be considered when interpreting the findings below.

Health impacts of heatwaves have traditionally been described using population-level ambient temperature indicators. However, occupational settings involve distinct exposure patterns characterized by elevated metabolic heat production, prolonged exposure duration, restricted recovery, and constrained heat dissipation due to personal protective equipment or work environments [52,53,54]. Therefore, although many physiological responses overlap with those observed in the general population, workplace heat exposure produces unique exposure–response relationships, cumulative strain patterns, and occupation-specific health risks. The following sections distinguish between general population evidence and occupationally specific mechanisms where applicable.

5.1. Acute Heat-Related Illnesses

At the population level, ambient temperature is a primary determinant of heat-related health outcomes [55]; however, in occupational settings, total heat load is jointly determined by environmental heat, metabolic heat production from physical work, exposure duration, and limitations in heat dissipation [26,54]. The human body regulates its core temperature and manages environmental and metabolic heat load mainly through four heat exchange mechanisms: conduction, convection, evaporation, and radiation. These mechanisms maintain thermal homeostasis under normal conditions. However, when heat load exceeds an individual’s thermoregulatory capacity, acute heat-related illnesses such as heat cramps, heat exhaustion, and heat stroke may develop—conditions that occur across populations but are disproportionately observed among outdoor and manual workers exposed to repetitive daily heat strain and sustained physical workloads [56].

Heat cramps typically occur during or after intense physical activity and are primarily caused by excessive loss of fluids and sodium through sweating. They often serve as an early warning sign of impending heat exhaustion. Clinically, heat cramps manifest as painful muscle spasms, but vital signs generally remain stable. Heat exhaustion is the most common form of heat-related illness, usually triggered by a combination of high ambient temperature and dehydration. Neurological symptoms include sudden headache, weakness, dizziness, syncope, chills, irritability, and impaired coordination [57]. The most severe and life-threatening heat-related illness is heat stroke, characterized by complex pathophysiological processes including systemic inflammatory responses, oxidative stress, cell death, and coagulation dysfunction [58]. In occupational environments, repeated heat exposure across work shifts, incomplete physiological recovery, and cumulative dehydration may accelerate progression from heat exhaustion to heat stroke [59]. Furthermore, in heat stroke patients, heat accumulation and blood redistribution result in reduced intestinal blood flow and increased permeability of the intestinal epithelial tight junctions. This facilitates translocation of toxic gut microbiota into the systemic circulation, triggering a cascade of detrimental systemic effect [60].

Despite substantial advances, current evidence has established that heat stroke is characterized by a systemic inflammatory response, oxidative stress, endothelial injury, coagulation dysfunction, and gut barrier disruption leading to endotoxemia [61,62]. These processes are interconnected rather than isolated, forming a multi-organ injury cascade driven by thermoregulatory failure [63,64]. In workers exposed to recurrent heat stress, this cascade may be initiated at lower environmental thresholds due to accumulated physiological strain and repeated subclinical injury. However, existing research remains fragmented across clinical, molecular, and occupational contexts, with limited integration of early biomarkers and individual susceptibility profiles [65], particularly among working populations exposed to repetitive heat stress.

5.2. Chronic Diseases

Population-based studies have identified heatwaves as significant risk factors for chronic diseases; however, occupational heat exposure represents a distinct and often more intense risk profile characterized by prolonged exposure duration, physical workload, and recurrent dehydration [36]. Workers with pre-existing conditions including diabetes, cardiovascular diseases, kidney disorders, and obesity, as well as those taking certain medications such as diuretics, anticholinergic drugs, or stimulants, are at heightened risk for heat-related health issues [66]. Exposure to high temperatures during heatwaves increases the risk of acute coronary syndrome (ACS) [67], and may interact synergistically with particulate matter in ambient or occupational settings, significantly impacting cardiovascular mortality [68].

The pathophysiology underlying heat-related cardiovascular and respiratory diseases shares common thermoregulatory responses across populations; however, in occupational environments, sustained metabolic heat production, repeated dehydration cycles, and concurrent exposure to pollutants may amplify cardiovascular strain [36]. Increased skin blood flow and sweating elevate respiratory rate and heart rate, while dehydration, increased blood viscosity, and elevated blood pressure collectively impose additional stress on the heart and lungs [69]. Research by Richard et al. [70] in regions such as Central America, India, and Sri Lanka demonstrated that sugarcane workers often experience dehydration during shifts, accompanied by asymptomatic increases in serum creatinine and mild or absent proteinuria. Kidney biopsies revealed chronic interstitial nephritis with variable glomerulosclerosis, suggesting that prolonged exposure to heatwaves is a probable risk factor for chronic kidney disease development [71,72,73]. These findings support a workplace-specific pathway involving recurrent subclinical acute kidney injury, dehydration-driven vasopressin activation, and cumulative renal damage under repetitive occupational heat exposure.

Moreover, heatwaves are risk factors for diabetes. Sun et al. [74] investigated workers in automobile manufacturing under high and non-high temperature conditions, finding higher prevalence rates of hypertension and hyperglycemia in the high-temperature group (26.2% and 3.8%, respectively) compared to controls (11.4% and 1.8%). Several mechanisms may explain this association: autonomic dysfunction and endothelial impairment in diabetic patients may increase heat sensitivity and reduce heat acclimatization [75,76]; additionally, redistribution of blood flow between skin and visceral beds driven by core temperature changes can impair glucose tolerance, while heat exposure may enhance insulin absorption and disrupt glycemic control [77].

While epidemiological evidence has established associations between heat exposure and chronic diseases, mechanistic studies integrating occupational exposure metrics, cumulative workload, and individual susceptibility remain comparatively limited, highlighting priorities for future occupational health research.

5.3. Mental Health Issues

Heatwaves affect mental health across populations; however, occupational groups may face additional risks due to physical fatigue, sleep disruption from shift schedules, productivity pressure, and increased accident risk under cognitive strain [78,79,80]. Evidence indicates [79] that when ambient temperatures exceed 26.7 °C, hospital admission rates for affective disorders, neuroses, stress-related and somatoform disorders, and developmental disorders rise by 7.3%, 9.1%, 9.7%, and 64%, respectively, compared to non-heatwave periods.

Animal studies have confirmed that heat-related illnesses increase dementia risk, but the underlying mechanisms affecting cognitive health warrant further exploration [81]. High temperatures may cause hyperthermia resulting in physical and psychological fatigue; heat-induced dehydration can impair cognition and mood. Seasonal affective disorder incidence may rise during heatwaves, potentially increasing violence, aggression, and disrupting circadian rhythms and sleep pattern [82]. Several psychotropic medications, including antipsychotics, anticholinergics, antidepressants, sedatives, and mood stabilizers, can impair thermoregulation by affecting parasympathetic pathways, reducing sweating, or increasing heat production [79]. Evidence on occupation-specific mental health outcomes during heat exposure remains limited, particularly regarding cumulative workload, decision fatigue, and safety-critical performance, representing an important future research direction.

5.4. Infectious Disease Risks

Heatwaves may indirectly increase infectious disease risks at the population level [83]; in occupational contexts, altered work–rest cycles, increased outdoor exposure, and reduced use of protective measures under extreme heat may further modify transmission dynamics [66]. During the 2022 summer heatwaves, COVID-19 case numbers surged globally—for example, new cases in Campania, Italy, increased by 181.2%; France saw a 114.5% increase; regions in Asia, South America, North America, and Oceania experienced an average increase of 121.5%; and Africa, including Tunisia and Ethiopia, reported an average increase of 298.4% [84]. However, the relationship between ambient temperature and SARS-CoV-2 transmission is complex and likely indirect. Laboratory and epidemiological studies have consistently shown that high temperatures and ultraviolet radiation reduce viral stability and aerosol survival [85,86], suggesting a direct inhibitory effect of heat on viral transmission. The observed case surges during heatwaves are more plausibly explained by behavioral adaptations: heat-avoidance behaviors such as seeking indoor cooling in air-conditioned public spaces, shopping malls, or healthcare facilities may increase interpersonal contact and indoor congregation, thereby facilitating transmission despite reduced viral viability [84,87]. For outdoor workers, heatwave-related behavioral changes—including increased use of shared cooling facilities, altered break schedules, and potential relaxation of protective measures due to thermal discomfort—may similarly modify infection risk, although occupation-specific evidence remains limited.

Heatwaves can affect the physiology of vectors, facilitating pathogen transmission [88,89,90]. Warmer and wetter conditions associated with heatwave periods can also expand mosquito breeding habitats and increase vector populations, elevating the risk of dengue, malaria, and other mosquito-borne illnesses, particularly among outdoor workers with prolonged environmental exposure [91]. Heatwaves also influence tick distribution and activity, thereby impacting the transmission of Lyme disease, tick-borne encephalitis virus, Crimean-Congo hemorrhagic fever virus, Mediterranean spotted fever, and related illnesses [92].

6. Occupational Health Risks from Heatwaves

The health impacts of heatwaves are not evenly distributed among populations, varying by age [93], sex [94], pre-existing chronic disease status [95] and socioeconomic factors. Occupational populations are particularly vulnerable due to heavy workloads, evolving work organization patterns, emerging employment structures, intense physical labor, outdoor exposure, and additional heat sources at workplaces, leading to greater heat exposure intensity and duration [96].

Heat exposure in workers can cause heat stress, impair work capacity, induce acute and chronic heat-related illnesses, and reduce productivity [26,97]. High-intensity physical labor in hot environments increases the risk of exertional heat stroke, with emergency department visit rates rising by a median of 75% for each 1 °C increase above 22 °C [98]. For workers exposed to hazardous chemicals, extreme heat enhances chemical absorption via increased ventilation and peripheral vasodilation, raising the incidence of occupational toxic exposures [99]. Extreme temperatures also reduce occupational performance and general functioning, increasing the risk of accidents and injuries [100]. Sun et al. [101] reported that prolonged heat exposure leads to neurasthenia in workers. Compared to local workers, migrant workers generally have higher occupational injury rates due to longer working hours, poorer conditions, and limited safety training [102]. The combined effects of high environmental temperature or humidity, high metabolic heat from labor-intensive work, and the use of protective clothing exacerbate the risk of heat-related illnesses among occupational groups [96,97].

Traditional high-risk sectors such as agriculture, construction, military, firefighting, mining, and manufacturing remain central to occupational heat research [66]; however, emerging forms of work—including platform-based logistics, temporary labor, and indoor high-heat industrial processes—are increasingly reshaping exposure patterns. Factors influencing occupational heat vulnerability include ambient temperature, personal protective equipment, work shifts, physical exertion, and heavy equipment use. Despite the high heat vulnerability of workers, current research on occupational heat vulnerability and health impacts is limited to few occupations and largely focused on developed countries [11,103,104], with insufficient attention to workers in low- and middle-income countries [105]. Furthermore, other factors affecting labor productivity, such as work experience, sex, age, alcohol consumption, and wages, remain underexplored [106].

Occupational heat risks are increasingly shaped by dynamic changes in labor structures, technologies, and exposure environments rather than by linear increases in ambient temperature alone. The rapid expansion of platform-based and informal employment has introduced new categories of heat-exposed workers, including delivery riders, logistics personnel, and temporary construction laborers [36,107,108,109], who often operate outside traditional occupational health protection systems. At the same time, industrial automation and enclosed production environments may reduce physical workload while simultaneously increasing heat accumulation due to limited ventilation and high radiant heat sources [110,111]. The widespread use of vapor-impermeable personal protective equipment, particularly in chemical, medical, and emergency response settings [112], has created novel exposure regimes in which metabolic heat and environmental heat interact non-linearly. Demographic shifts, including workforce aging and increased participation of migrant and precarious workers [113], further alter vulnerability profiles and adaptive capacity. These evolving exposure patterns suggest that occupational heat risks are not static but emerge through the intersection of climatic change, labor organization, technological transformation, and social inequities.

Despite growing recognition of occupational heat risks, the implementation of preventive measures in real-world workplaces remains inconsistent. In many heat-exposed industries, productivity pressures [114], piece-rate payment systems [115], and informal employment arrangements [116,117] discourage workers from taking adequate rest breaks or reporting heat-related symptoms. Migrant and temporary workers [118,119,120] often face additional barriers, including limited access to occupational health services, insufficient safety training, and weak bargaining power to demand protective measures.

At the policy level, heat exposure standards in many countries remain advisory rather than mandatory, and enforcement capacity varies substantially across regions and sectors [66,121]. Small- and medium-sized enterprises [115] may lack financial incentives or technical capacity to invest in engineering controls, physiological monitoring, or adaptive work-rest scheduling. These structural constraints shape occupational heat vulnerability and underscore the need for governance-integrated adaptation strategies discussed in Section 7.

7. Quantitative Assessment and Prediction of Heatwaves

7.1. Calculation and Occupational Monitoring of Heatwaves

Numerous indices have been developed to characterize heatwaves at the climatic scale, typically based on combinations of land surface temperature, air temperature, and duration thresholds [122,123]. While these indices are effective for identifying extreme heat events, they are not intended to directly represent human thermal strain.

In occupational settings, heat risk assessment requires metrics that integrate environmental conditions with physiological load. The Wet Bulb Globe Temperature (WBGT) index remains one of the most widely adopted standards for occupational heat stress assessment [124,125], owing to its operational simplicity and regulatory acceptance. However, WBGT does not explicitly account for inter-individual variability in metabolic rate, clothing insulation, or acclimatization status [126,127]. To address these limitations, correction factors and complementary approaches—such as Predicted Heat Strain (PHS) models, physiological monitoring (e.g., heart rate, core temperature), and thermophysiological simulations—have been increasingly applied in high-risk occupational environments [128]. These methods shift the focus from ambient heat exposure to human-centered thermal strain, which is particularly relevant for physically demanding work under extreme heat.

Although WBGT has been theoretically linked to human heat balance under specific assumptions, its applicability is highly conditional. Empirical and modeling studies indicate that WBGT implicitly assumes a fixed level of skin moisture and metabolic load, and may underestimate heat strain under conditions of high humidity, elevated metabolic intensity, strong solar radiation, or vapor-impermeable protective clothing [129,130,131]. Taken together, these constraints suggest that reliance on a single WBGT threshold may be insufficient for occupational settings characterized by heterogeneous tasks and protective requirements, reinforcing the need for task-specific and context-aware heat stress assessment.

7.2. Heatwave Detection and Forecasting

Accurate identification and forecasting of heatwaves are critical for mitigating health risks, particularly among vulnerable occupational groups. Both data availability and analytical methodology play central roles in heatwave prediction and early warning.

At the climatic scale, high-resolution temperature and humidity datasets have been widely used to construct heatwave indices and project future exposure scenarios. For example, several studies have modeled population-level heatwave exposure across major global cities by integrating climate projections with demographic data [16]. While such approaches are effective for identifying extreme heat events, they are not designed to directly capture individual-level heat strain or occupational workload. In contrast, physiologically based models such as the Predicted Heat Strain (PHS) model have been applied in occupational settings to estimate core temperature and dehydration risk, although their accuracy depends on detailed input parameters that are often unavailable in large-scale surveillance [128].

A range of statistical models has been employed to quantify temperature–health associations. Distributed Lag Non-linear Models (DLNMs) are particularly useful for characterizing delayed and non-linear effects of heat exposure on health outcomes [132], but their performance is sensitive to lag structure selection and may be unstable under sparse extreme-event data. Generalized Additive Models (GAMs) offer flexible estimation of exposure–response relationships with good interpretability [133], yet they assume additive effects and may inadequately represent complex interactions among environmental and physiological factors. Extreme value approaches, such as stationary and non-stationary Generalized Extreme Value (GEV) models, have been applied to estimate heatwave return periods and thresholds [134], although their applicability is primarily limited to extreme-event characterization rather than short-term health risk prediction.

In recent years, machine learning [135] and deep learning models have gained attention for their ability to model complex, non-linear relationships between heat exposure and health outcomes. Algorithms such as decision trees, random forests, and gradient boosting machines can improve predictive performance and handle multicollinearity [136,137]; however, they often sacrifice interpretability and may exhibit reduced generalizability when trained on location- or occupation-specific data. Deep learning architectures, including Recurrent Neural Networks (RNNs) [138], Long Short-Term Memory (LSTM) [139] and Convolutional Neural Networks (CNNs) [140,141] have shown promise in capturing temporal patterns and high-dimensional inputs, but their black-box nature and high data requirements limit their practical deployment in occupational health decision-making.

Bayesian approaches provide an alternative framework by explicitly accounting for uncertainty and heterogeneity across populations and datasets [142]. For example, Bayesian Model Averaging and hierarchical models have been used to estimate heat-related mortality risks [143,144] while incorporating model uncertainty. Nevertheless, these methods are computationally intensive and may be challenging to implement in real-time heat warning systems.

Taken together, existing heatwave detection and forecasting approaches vary substantially in their assumptions, data requirements, and interpretability. No single model is universally applicable across climatic, occupational, and physiological contexts, underscoring the need for context-specific modeling strategies that balance predictive accuracy with practical usability in occupational heat risk management. In parallel, a synthesis of epidemiological evidence on heat-related health outcomes in occupational populations is provided in

Table 1. Summary of Heat-Related Health Impacts on Occupational Populations.

Category	Health Outcome	Key Evidence/Findings	Occupational Relevance	References
Acute Heat-Related Illnesses	Heat cramps	Caused by fluid and sodium loss during physical activity; early warning sign of heat exhaustion	Disproportionately observed among outdoor and manual workers	[56,57]
	Heat exhaustion	Most common heat illness; symptoms include headache, dizziness, syncope	Triggered by combined high ambient temperature and dehydration during work	[57]
	Heat stroke	Systemic inflammatory response, coagulation dysfunction, multi-organ injury	ED visit rates rise ~75% per 1 °C above 22 °C; repeated occupational exposure lowers onset threshold	[58,60,61,62,63,64]
Chronic Diseases	Cardiovascular disease	Increased ACS risk; synergistic effect with particulate matter	Sustained metabolic heat production amplifies cardiovascular strain	[67,68,69]
	Chronic kidney disease	Recurrent dehydration → subclinical AKI → cumulative renal damage	Documented in sugarcane workers in Central America, India, Sri Lanka	[70,71,72]
	Diabetes/Hyperglycemia	Higher prevalence in high-temperature worker groups (3.8% vs. 1.8%)	Autonomic dysfunction and impaired glucose tolerance under heat	[75,76,77]
Mental Health	Affective disorders	Hospital admissions increase 7.3% during heatwaves (>26.7 °C)	Additional risks from physical fatigue, sleep disruption, productivity pressure	[79]
	Neuroses	Hospital admissions increase 9.1% during heatwaves	Cognitive strain may impair safety-critical performance	[79]
	Developmental disorders	Hospital admissions increase 64% during heatwaves	Limited occupation-specific evidence	[79]
Infectious Diseases	Vector-borne diseases	Altered vector physiology and distribution; expanded mosquito breeding	Outdoor workers face prolonged environmental exposure	[90,92]
	COVID-19	Temporal co-occurrence with heatwave surges documented	Altered work–rest cycles and reduced protective measures	[84]
Occupational-Specific	Chemical toxicity	Enhanced absorption via increased ventilation and vasodilation	Workers exposed to hazardous chemicals at heightened risk	[99]
	Occupational injuries	Reduced performance and cognitive function	Accident risk increases under extreme temperatures	[100,101]
	Neurasthenia	Reported in workers with prolonged heat exposure	Direct occupational exposure evidence	[101]

, which summarizes acute, chronic, mental, and occupational-specific health risks associated with heat exposure. Importantly, when linked with occupational exposure thresholds (e.g., WBGT- or PHS-based criteria), these forecasting models can support operational early-warning systems that translate meteorological alerts into actionable workplace measures such as adaptive work–rest scheduling, task modification, and targeted risk communication for vulnerable worker groups.

To synthesize the multi-level evidence discussed across climatic drivers, occupational exposures, physiological responses, monitoring approaches, and adaptive strategies, Figure 1 presents an integrative framework that organizes existing knowledge across climatic, occupational, physiological, and institutional dimensions, highlighting their interconnections in occupational heat risk management.

The figure synthesizes existing evidence across climatic drivers, occupational exposure pathways, physiological mechanisms, and institutional response strategies under extreme heat conditions. It illustrates the interconnections among environmental, biological, and governance dimensions to facilitate cross-sectional integration of the topics discussed in this review. The framework is intended as an organizational structure for integrating multidisciplinary evidence rather than a novel causal model.

8. Response Measures and Resilience Building for Extreme Heat Events

A comprehensive evaluation of the effectiveness of individual resilience strategies is beyond the scope of this narrative review. The strategies discussed below are identified based on existing literature and policy recommendations; where available, supporting references are cited to justify the inclusion of each strategy.

8.1. Strengthening Urban and Regional Heatwave Response Systems

Effective heatwave preparedness requires coordinated action across emergency management, urban planning, and healthcare systems. Establishing centralized communication hubs, pre-positioning medications and supplies, and optimizing power supply reserves are essential for emergency response [145,146]. Cooling centers and water stations offer immediate relief during peak heat periods [147,148]. Urban adaptation strategies include expanding green infrastructure, using reflective materials in construction, and enforcing building codes to reduce the urban heat island effect [149,150,151]. Research institutions play a key role in developing innovative technologies and risk communication tools to mitigate the impact of extreme heat.

Integrated heat-health early warning systems (HEWS), which combine meteorological, clinical, and community-level data, are increasingly being adopted worldwide to mitigate the health risks of extreme heat. These systems, implemented in cities across Asia, Europe, and North America—including Nanjing [152], Shenzhen, Jinan and Qingdao [153] in China—utilize region-specific risk models and tiered alert mechanisms [154], often supplemented by mobile apps, satellite imagery [155], and SMS-based public notifications [156].

8.2. Enhancing Occupational Heat Resilience

Frequent and intense heatwaves threaten the health, safety, and productivity of millions of workers. To address these risks, China has implemented heat-related compensation policies that have shown positive effects on occupational heat resilience [157]. Policy recommendations include regulating work hours, mandating rest periods, and providing heat-mitigation facilities in high-risk industries [158,159]. Employers can retrofit workplaces with better ventilation and insulation systems, supply clean drinking water, and create shaded rest areas [160,161]. Innovations such as high-efficiency cooling garments [162], wearable biosensors, and smart thermoregulation devices are being developed to monitor and manage occupational heat stress [162]. These technologies increasingly enable threshold-based interventions, such as WBGT-triggered work–rest adjustments, physiological alert systems, and forecast-informed workplace heat response activation.

However, many traditional heat protection strategies were originally designed for stable outdoor exposure scenarios and may be less effective under emerging occupational conditions characterized by fragmented work schedules, mobile labor platforms, enclosed high-heat indoor environments, and combined thermal and chemical exposures. Traditional approaches often rely on fixed schedules and uniform workforce assumptions, whereas emerging adaptive strategies emphasize dynamic risk thresholds, task-specific physiological monitoring, and forecast-responsive interventions. These evolving exposure regimes challenge conventional assumptions regarding fixed work–rest cycles and uniform workforce vulnerability. As occupational heat risks become increasingly dynamic and intersectional, adaptation strategies require continuous reassessment rather than static implementation.

While these interventions are technically feasible, their effectiveness depends heavily on supportive labor policies, enforcement mechanisms, and economic incentives [26]. In practice, the adoption of occupational heat protection measures is often constrained by cost considerations, fragmented regulatory responsibilities, and limited employer compliance, particularly in informal or subcontracted labor sectors. Operational implementation may require targeted resource allocation mechanisms, including municipal outreach programs, mobile cooling and hydration stations, sector-specific subsidies, and integration of heat protection into social insurance and community health services to reach informal and temporary workers. Without integrating heat protection into labor standards, social protection systems, and employer accountability frameworks, technological solutions alone may have limited impact. Effective governance therefore requires cross-sector coordination among meteorological agencies (early warning), labor regulators (workplace enforcement), and public health authorities (risk communication and surveillance), enabling operational translation from heat forecasts to workplace actions.

9. Conclusions

This narrative review was guided by three research questions concerning the physiological mechanisms through which extreme heatwaves affect occupational populations, the structural constraints limiting workplace adaptation, and the integrated strategies needed to enhance occupational heat resilience.

Regarding the first question, the review identified multiple interconnected physiological pathways through which extreme heat affects occupational populations. Acute outcomes—including heat cramps, heat exhaustion, and heat stroke—are driven by thermoregulatory failure, systemic inflammation, coagulation dysfunction, endothelial injury, and gut barrier disruption. In occupational settings, these pathways are amplified by elevated metabolic heat production, cumulative dehydration, and incomplete recovery between work shifts. Chronic disease risks, including cardiovascular disease, chronic kidney disease, and diabetes, are exacerbated through workplace-specific mechanisms such as recurrent subclinical acute kidney injury and sustained hemodynamic stress. Mental health outcomes, including increased rates of affective disorders and neuroses, are compounded by occupational factors including physical fatigue, cognitive strain, and sleep disruption.

Regarding the second question, the review identified several structural constraints that limit the effectiveness of existing workplace heat adaptation strategies. These include productivity pressures and piece-rate payment systems that discourage rest breaks; informal and platform-based employment arrangements that place workers outside traditional occupational health protection systems; advisory rather than mandatory heat exposure standards with variable enforcement; and limited financial and technical capacity among small- and medium-sized enterprises. Migrant and temporary workers face additional barriers including limited access to health services and weak bargaining power.

Regarding the third question, the review highlights the need for integrated, multi-sectoral strategies that combine dynamic early warning systems with occupational enforcement, urban adaptation (green infrastructure, reflective materials), technological innovations (cooling garments, wearable biosensors), and governance frameworks that link meteorological forecasting to actionable workplace measures. Effective resilience requires cross-sector coordination among meteorological agencies, labor regulators, and public health authorities, as well as the integration of heat protection into labor standards and social protection systems.

Future research priorities include: (1) longitudinal epidemiological studies of occupational populations exposed to recurrent extreme heat; (2) integration of early biomarkers and individual susceptibility profiles into workplace heat risk assessment; (3) evaluation of the effectiveness of emerging adaptive strategies under real-world conditions; and (4) expanded research on occupational heat risks in low- and middle-income countries and among emerging worker categories such as platform-based and informal laborers.

10. Strengths and Limitations of This Review

This review has several limitations. As a narrative evidence synthesis, it does not follow formal systematic review procedures and may be subject to selection bias. The included literature spans diverse occupational settings, climatic regions, and methodological approaches, resulting in heterogeneity that limits direct comparability across studies. In addition, mechanistic evidence linking occupational heat exposure to long-term health outcomes remains fragmented. The resilience strategies discussed in this review are identified from existing literature and policy recommendations; a systematic evaluation of their effectiveness was not undertaken and represents an important direction for future research. Despite these limitations, the integrative approach allows synthesis across climatic, physiological, and occupational domains to highlight emerging risks and research gaps.