Introduction

The swift industrial and economic growth experienced globally since the Industrial Revolution has been linked to a significant rise in the production of greenhouse gas (GHG), resulting in global warming. This global warming is triggering such drastic climate change (CC) that many consider it a threat to our very existence [1].

CC denotes enduring changes in temperature and weather patterns [2]. In October 2021, the World Health Organization (WHO) [3] recognized CC as “the foremost health challenge confronting humanity”. Since 1900, annual global mean temperatures have increased by 1.1°C, mainly in the past 50 years [4]. By the end of this century, expected warming is expected to reach up to 2.5°C to 2.9°C [5]. The international community must limit the increase in temperature to 1.5°C to prevent disastrous health consequences [6]. Since the Earth functions as an interconnected system, a rise in temperature marks just the start of alterations in one area that can trigger changes in all others. CC is linked to a rise in extreme weather phenomena, such as severe droughts, water shortages, intense wildfires, rising ocean levels, flooding, melting ice caps, devastating storms, and diminishing biodiversity. Human actions have been the primary cause of CC, mainly resulting from the combustion of fossil fuels such as coal, oil, and gas. The pressing need to address the effects of CC is commonly referred to as the climate crisis [7]. GHGs must be cut in half by 2030, and net-zero carbon dioxide (CO₂) emissions must be reached by 2050 in order to minimize temperature rise [8, 9]. The costs of doing nothing will be much outweighed by the economic advantages of achieving net-zero GHG emissions [10]. GHGs are substances that produce the greenhouse effect, a phenomenon where heat from the sun is trapped in Earth’s atmosphere and unable to escape into space. CO₂ is one of these gases; human activity is responsible for more than 64% of global warming [11]. Because CO₂ can linger in the atmosphere for decades without dissipating, its effects on the ecosystem and human health are long-lasting. The majority of gases that cause CC are referred to as short-lived climate pollutants (SLCPs) because, in contrast to CO₂, they do not remain in the atmosphere for very long. However, they have a greater warming impact than CO₂, which seriously harms the ecosystem. One of these gases, ozone, affects the climate more significantly than previously believed. It remains in the atmosphere for twelve years. Compared to CO₂, its warming effect is 81.2 times stronger over a 20-year period and 28 times stronger over a 100-year period [12].

Light outdoor exercise carries a moderate risk of heat stress, with an annual rise of 27.7% compared to 2000 [13], and reduces labor productivity [14, 15] in addition to endangering workers’ health [16]. Up to 512 billion potential work hours were lost in 2023 as a result of heat exposure, which is 49% more than the average from 1990 to 1999. Of these, 63% were lost in the agricultural sector [13]. Nighttime temperatures brought on by CC are linked to both quantity and quality of sleep disturbances [17].

Methodology

A systematic literature search in PubMed MeSH and Google scholar searches were done. Full-text articles published in English and articles providing an English abstract were reviewed. The following terms were used: “climate change, global warming” OR “climatic change” OR “atmospheric change” OR “meteorological change” AND “health map” OR “emerging disease” OR “reemerging disease” OR “communicable disease” OR “non-communicable disease” OR “infectious disease” OR “endemic disease” OR “epidemic disease”. We also manually examined the reference lists to identify additional relevant studies.

Vulnerable groups

Children and the elderly: Heatwaves pose a serious health risk, particularly to the elderly, small children, and those with underlying chronic renal, respiratory, or cardiovascular conditions [18]. Due to their susceptibility to environmental stressors and undeveloped biological defenses for immunological protection, DNA repair, and detoxification, children under the age of five suffer greatly [19]. Malnutrition in children is predicted to rise by 20% by 2050, impacting an extra 25 million kids. This will seriously impede efforts to reduce malnutrition among children [20]. However, compared to 1990–2000, heat-related mortality among adults over 65 has increased by 85%, above the predicted 38% increase in the absence of temperature changes. These deaths are expected to spike by 370% by 2041–2060 and 683% by 2081–2100 if temperatures rise by 2°C [21].

Gender inequalities

Women may be twice as likely as men to die from heat-related causes. Food insecurity and mortality rates are significantly greater in low-income households [22]. When food is scarce, women and girls tend to eat last and skip meals. In addition to impeding women’s access to maternity and reproductive health care, CC affects pregnancy outcomes by altering temperature, nutritional status, and infectious illness risk [23].

Migration

One significant mechanism for the quick spread of infectious diseases is the movement of impacted workers from endemic contaminated areas as a result of the CC disasters to other virgin areas. Furthermore, it was discovered that untreated and undertreated liver disorders were present in the immigrant population [24]. There are currently 281 million foreign migrants among the more than 1 billion people on the move [25]. “Environmental migrants” are individuals or groups who are compelled to relocate either temporarily or permanently, either domestically or internationally, as a result of unfavorable environmental changes [26]. About 25% of all chronic HBV infections in the region are caused by people who migrate from endemic countries to the European Union/European Economic Area (EU/EEA) [27].

Region-specific effect

People around the world are unequally affected by CC [28]. Africa, South and Central America, and Asia experienced the highest number of days of health-threatening temperatures attributable to CC. Africa experienced the biggest increase in a heat-related mortality rate since 2000–2005. Recently, Europe had the highest rate of heat-related mortality 2017–2022 [17, 28, 29].

Given the reality of CC, its impact on the development of liver disease is increasingly recognized. It is important to understand the potential impact of CC on our patients and consider what we can do to impact the resultant climate crisis.

Impact of CC on liver diseases

Globally, liver diseases are responsible for 2 million deaths annually; however, the number is still growing [30]. CC potentially influences all determinants of liver disease and consequently contributes to the anticipated increase in the global burden of liver disease [31]. CC can affect health directly or indirectly (Figure 1).

Display full size

Figure 1. Climate and air quality interactions and direct and indirect effects on health. Reprinted from [32]. © 2017, The Author(s). Distributed under the terms of the Creative Commons CC BY license.

The physiological effects of excessive heat are more likely to affect those with chronic illnesses [33].

Extreme heat physiologically results in hepatic cell necrosis, ischemia, acute liver damage, and, in severe cases, acute liver failure [34].

Mental health is said to be negatively impacted by the climate issue. Alcohol-related viral hepatitis may develop as a result of substance abuse, which has been linked to anxiety and stress [35]. The three most prevalent causes of liver disease are viral hepatitis, alcohol-related liver disease, and metabolic dysfunction-associated steatotic liver disease (MASLD), all of which are vulnerable to the effects of CC. Although the precise processes are yet unknown, air pollution is linked to the development of cirrhosis, chronic liver damage, and steatotic liver disease [36]. Additionally, a possible connection between rising ambient temperatures and biliary tract disease admissions has been found; however, the underlying processes are yet unknown [37].

Conversely, energy use, medical waste, and transportation emissions from healthcare systems—including liver units—contribute significantly to CC [38]. Unused medications at home are estimated to constitute 2 out of 3 prescription medications costs $2–5 billion in the United States alone [39].

The quantity of CO₂ we emit as a result of our activities is known as our carbon footprint. The carbon footprint of the healthcare industry contributes significantly to global CO₂ emissions—more than 4.4% [40, 41]. About 45% of emissions in endoscopy services are related to staff and patient transportation, and 32% are caused by the manufacture and disposal of medical equipment [42]. 1–2% of all urban waste is made up of healthcare waste (HCW) [43], of which 15% is deemed hazardous. The globe would be headed toward a potentially disastrous 2.7°C warming if the existing policies and practices are maintained [44]. Therefore, efforts to lower GHG emissions are crucial to safeguard people's health, survival, and well-being in every nation and provide immediate and long-term health advantages [45].

Individual liver diseases

MASLD and CC

The frequency of MASLD has alarmingly increased from 25.5% before 2005 to 37.8% in recent years, with current estimates at 32.4% [84, 85]. Recent evidence reveals that environmental factors play a crucial but underexplored contribution to the pathophysiology of MASLD. MASLD epidemic and the acceleration of the climate crisis go hand in hand, in addition to undernutrition and obesity [86]. Food insecurity in vulnerable locations worsens as a result of CC’s rising impacts on agriculture, society, and the economy [87]. This is expected to induce obesity and contribute to excessive consumption of refined foods, which could raise the global burden of liver disease related to MASLD [88, 89]. A key component of managing liver disease, particularly in people with MASLD, is optimal diet. However, people with cirrhosis frequently suffer from malnutrition, which is particularly prevalent in those who are food insecure [90]. Sedentary behavior is a significant risk factor for MASLD [91]. Provocation of oxidative stress and stimulation of inflammatory responses impair hepatic metabolism and increase hepatic triglycerides and cholesterol, thereby fostering MASLD [92]. Microcystins (a hepatotoxic by-product of blue-green algae, which are increasing due to CC, and which can contaminate drinking water and swimming sites) can lead to progressive MASLD [93] (Figure 2).

Display full size

Figure 2. How excessive heat exacerbates metabolic dysfunction-associated steatotic liver disease (MASLD).

A solid argument that ambient temperature variability (TV) functions as a harmful environmental driver of MASLD was recently presented by Wang et al. [94] in a nationwide investigation in 2026, showing nonlinear exposure-response correlations. A U-shaped relationship for TV, where both low and high unpredictability independently increased susceptibility, and a reverse J-shaped curve for long-term temperature exposure, where extreme cold conferred the highest MASLD risk. They were able to place these national findings in China into a larger international perspective by integrating global burden of disease (GBD) data, providing supportive but not causal evidence that comparable patterns may develop across varied climatic zones. They propose that TV could be an independent risk factor for MASLD, especially in areas where extreme and frequent temperature changes are expected [95]. They emphasize that when assessing environmental factors that contribute to liver illness, it is important to take into account both the absolute temperature and its variability. Mechanistically, exposure to cold can cause hepatic de novo lipogenesis [96], whereas television interferes with circadian metabolic cycles, aggravating oxidative stress and inflammation [97, 98]. Due to increased oxidative stress and hepatic inflammation brought on by exercise in unfavorable settings, people with high levels of physical activity were more susceptible to MASLD in extreme weather conditions [99]. The dangers of obesity and MASLD were exacerbated by low TV exposure, which was more strongly linked to MASLD in the obese, whereas high TV exposure was more harmful to normal-weight people [100]. Incorporating environmental variables into MASLD prevention initiatives may help reduce the increasing burden of chronic liver disease by improving early identification and informing tailored therapies meant to mitigate the negative health impacts of CC. They highlight the dual problem of climate adaptation: worldwide initiatives to reduce rising temperatures must coexist with region-specific methods (such as cold mitigation in temperate zones). The growing MASLD pandemic amid CC may be lessened by including temperature resilience into public health systems.

Strategic goals and objectives

Creative solutions to minimize waste-related costs and negative environmental impacts while preserving patient care and scientific advances are a priority. The utmost target to be emphasized is primary prevention and early diagnosis [29, 109]. Ninety per cent of liver disease is potentially preventable in Western populations [110] (Figure 3).

Display full size

Figure 3. Health care systems, including liver units, contribute significantly to climate change.

A strategy to prevent alcoholic liver disease and reduce hospital admissions is an example of reducing GHG. Recent reports have shown a 4% decrease in alcohol-related hospital admissions, causing a positive environmental impact [111].

In order to lower costs and enhance results in the final year of life, Hudson and his colleagues [112] (2018) advise broader implementation of day-case models of care. They discovered that compared to patients receiving unplanned treatment, a specialized paracentesis service, patients with liver cirrhosis who visited a day case service had nearly 17 fewer hospital bed days.

To develop criteria for patient follow-up and encourage remote contact and use of noninvasive testing is important to decrease GHG emissions.

Plant-based diets, as opposed to red meat and ultra-processed foods, have lower carbon footprints than a typical Western diet and are estimated to be associated with a reduction in GHG emissions by up to 84% [113] and a lower risk of MASLD [114]. Regular exercise reduces the incidence of fatty liver [115]. If one person changed a single trip per day from driving to cycling, this would reduce that individual’s carbon footprint by approximately 0.5 tons over 1 year [116].

Healthcare providers can promote and teach healthy lifestyle practices, including “planetary health diets”, as proposed by the EAT-Lancet Commission: “Food is the single strongest lever to optimize human health and environmental sustainability on earth” [117].

“Greening” operating rooms, which generate up to 30% of a hospital’s total waste and consume 3–6 times more energy per square foot than other parts of the hospital [118], with anesthesia gases making up more than 50% of the carbon footprint of surgical procedures [119].

The concept of a more sustainable future for endoscopy has been well promoted by the “Green Endoscopy Group” [120], motivated by the inconvenient observation that endoscopy is the third highest source of waste in a typical hospital [121]. A typical endoscopic treatment produces 2.1 kg of trash on average [122]. The traditional sustainability philosophy of “reduce, reuse, recycle” must be applied; cutting back on pointless procedures, which can account for up to 56% of upper GI endoscopies and between 23% and 52% of colonoscopies, can drastically reduce carbon footprints [123]. Inappropriate endoscopies produce 3,500–4,700 metric tons of CO₂ per year in Italy [124] and 30,804 metric tons of CO₂ per year throughout Europe [125]. Rationalizing the usage of specimen pots is another crucial step in lowering the carbon footprint of endoscopy, since the histological processing of tissue samples accounts for 36% of emissions [126].

ESGE suggests against the routine use of single-use devices and proposes using reusable alternatives instead of disposables. Last but not least, any waste should be recycled. In the endoscopy unit of a university hospital, these measures could collectively reduce carbon emissions by 18.4% [126].

In addition to endoscopy, alternative diagnostic techniques include intestinal ultrasound in place of colonoscopies [127]; fecal calprotectin may prevent needless endoscopic procedures if the likelihood of IBD is low, and instruments like FibroScan have less of an impact on the environment than repeated endoscopy and liver biopsies for cirrhosis and varices detection [125]. In order to minimize needless endoscopies, the Baveno VII consensus suggests estimating variceal risk using transient elastography and platelet counts [128].

Globally, the health industry is a major contributor to GHG emissions; in the US, for instance, it is responsible for 8.5% of total carbon emissions [129]. In the US healthcare system, waste is projected to cost about 25% of overall health care spending [130].

Examples of low-carbon alternatives and sustainable services in hepatology include telemedicine “virtual” consultations, which have become more popular since the start of the COVID-19 pandemic and can lead to significant carbon savings [131, 132], and outpatient, unsedated, ultrathin endoscopy, which can be performed during a routine clinic visit [133]. The downscaling of in-hospital liver care in one center resulted in lower patient satisfaction and higher liver-related mortality; thus, enthusiasm for telemedicine needs to be tempered with prudence [134]. To encourage a comprehensive and health-focused response to the dangers posed by CC, much work remains.

Limitations

Most of the studies dealing with CC and liver diseases are observational, with no confirmed causal mechanism relationship. In most cases, the data are uneven and vary from one region to another. The conclusions vary according to the included personnel characteristics and age group. Also, ethnicity affects the CC effects.

Conclusions

As an early warning system for hepatic health issues, CC may be crucial for health decision-makers. Planning solutions for CC adaptation and mitigation can make use of it. Many hepatic conditions, particularly infectious liver illnesses such as viral hepatitis, MASLD, ACLF, and HCC, could be made worse by prolonged exposure to CC. Clinicians should take into account the movement of infected patients from their endemic locations as a result of their diagnosis, as well as the knowledge that CC is a risk factor for a number of liver illnesses. Apart from increasing awareness, which ought to be the first objective, it is imperative to investigate new ways to frame the educational message and eliminate financial incentives that encourage environmental damage. Reducing and managing waste, using less and cleaner energy, offering and promoting foods that are good for the environment, and handling transportation to and from healthcare facilities are common climate solutions for healthcare systems.