Climate change has been described as the defining issue of our time by the United Nations [1]. The Paris Agreement states that limiting the rise in global temperature to no more than 1.5 °C can preserve a climate suitable for human habitation [2,3]. However, current targets are not being met, with May 2024 being declared as the hottest May on record by the European Commission’s Copernicus Climate Change Service [4]. To limit climate change, every industrial sector must be scrutinized, especially those with the highest emissions.

If the health care sector were a country, it would be the fifth largest polluter on the planet [5]. In the United Kingdom, the National Health Service (NHS) accounts for 40% of public sector emissions [6], and despite fewer than 5% of hospital inpatients undergoing surgery, operating theaters contribute up to 25% of hospitals’ carbon emissions. Therefore, if the NHS is to reach its net zero by 2045 target, surgical practices must be evaluated and adapted [7,8].

To identify how improvements can be made to reduce emissions, sustainability audits should be performed. Sustainability audits assess the performance of an organization in terms of its sustainable business practices through analyzing internal and external factors [9]. Furthermore, life cycle assessments enable us to evaluate a product or service’s environmental consequences throughout its course [10]. Process mapping is a powerful tool that can help guide life cycle assessments, allowing visual representation of patient journeys in a series of consecutive events or steps [11]. Combining process mapping and life cycle assessment techniques within surgical pathways has been described by Glynou et al [12] as a way to understand and recognize opportunities for improvement through identification of carbon hotspots and has been used in reconstructive breast surgery [13].

Skin cancer is the most commonly diagnosed cancer worldwide, with an estimated 1.5 million new diagnoses in 2022 [14]. Treatment options for skin cancer include surgery, radiotherapy, photodynamic therapy, and chemotherapy [15]; however, between 2013 and 2021, surgery was performed in more than 85% of cases [16]. Due to the high rate of excisional procedures performed annually, the cumulative carbon footprint attributable to the skin cancer surgery service is likely to be high. This study aims to quantify the carbon footprint of skin cancer excisions through process mapping and performing a life cycle assessment. This will identify carbon hotspots and suggest targets to increase the sustainability of the skin cancer surgical pathway (Figure 1).

This study used process mapping and performed a life cycle assessment for patients on the skin cancer patient pathway in secondary care. Through consideration of both patient-facing and organizational steps, this study estimated the approximate carbon footprint from referral to the final dressing clinic to be 118.5 kgCO2eq. This is equivalent to driving a petrol-powered car a distance of 472.2 km or flying at 1317 km, approximately the distance from London to Bilbao, Spain [17]. All 3 phases of the pathway had significant contributions to emissions, despite the perioperative phase having the highest emissions (53.1 kgCO2eq, 44.8%).

Process mapping was first used in the manufacturing industry and has since been adopted by other industries, such as business and health care. Within health care, process mapping enables direct visualization and measurement of the delivery of complex patient pathways at each point in time [18]. Process mapping, therefore, allows inefficiencies in pathways to be identified and improved. This study found multiple inefficiencies within the skin cancer pathway, many of which, if addressed, have the potential to increase patient throughput, improve patient outcomes, and increase staff satisfaction. A recent report by Cancer Research UK found that in 7% of MDTs, decisions were deferred due to missing information or team members [19]. Our study found substantially higher rates of missing information, with an average of 2 MDTs before surgery per patient due to missing imaging, pathology, and antigen testing results and a lack of coordination between departments. This led to patients being rescheduled for discussion at the next MDT, causing an effective 7-day delay in the treatment plan and a wasted slot for discussion of other patients. Suggestions for improvement to the MDT include a streamlined protocol and standardized proforma to enable more time for discussion of more complex patients (an issue ranked as the second highest priority among the changes necessary for the skin cancer MDT) [20]. Clinical guidance from the National Institute for Health and Care Excellence (NICE) dictates that core MDT members should attend more than 50% of the total meetings annually [21]. The skin cancer MDT in this study was a hybrid meeting with histopathologists joining virtually. This enabled improved meeting attendance by all clinicians and simultaneously reduced carbon emissions from staff travel.

The skin cancer patient pathway is currently multistaged and the same for all patients regardless of varying diagnostic uncertainty on patient diagnosis and/or treatment. We propose a pathway restructure through stratification after the initial consultation. Restructuring surgical pathways and process maps via risk stratification has been used within perioperative medicine by anesthetists but has yet to be used for surgical decision-making [22]. Within the skin cancer pathway, low-risk patients with limited uncertainty could follow a simpler pathway, bypassing potentially unnecessary logistical hurdles, and only those with higher risk or uncertainty would be referred using the traditional pathway with multiple MDTs to allow collaboration between specialties. Furthermore, lesions that mimic skin cancer account for a significant proportion of all excisions. The NICE reported in 2025 that 94% of excisions were classified as noncancer or nonurgent cases [23]. This burden therefore carries a significant environmental footprint due to the cumulative volume of these removals.

Medical imaging departments are the greatest contributors to greenhouse gas emissions, responsible for approximately 1% of global emissions [24]. Hanneman et al [25] reported that 1 imaging department covering 5 hospital sites had comparable energy use to that of 422 single-family homes or the average greenhouse gas emissions generated by 770 gasoline-powered passenger vehicles driven for 1 year. A life cycle assessment by Thiel et al [26] found that energy consumption from clinical use of imaging equipment accounted for more than half of departmental greenhouse gas emissions. In this study, imaging and nuclear medicine contributed more than one-third of total carbon emissions across the skin cancer pathway (42.5 kgCO2eq, 35.9%). The most common form of preoperative imaging in the diagnostic period was MRI, the modality reported to have the highest carbon emission output [27]. Clinicians should be advised to use toolkits such as that proposed by Brown et al [28], whose recommendations include using and regularly updating clinical decision-making support tools to justify imaging requirements and to limit the number of unnecessary images, which increase energy use even after scanner use due to the need for data storage servers and cooling systems. Furthermore, most patients in this study had sentinel node scintigraphy as part of their procedure (37/64, 57.8%); similar pressures to reduce nuclear medicine use where possible exist. Potential strategies include further involvement of patients in the decision-making process by including the carbon cost of imaging as part of informed consent and carbon offset payments by governments or insurance companies [29].

This study is the first to calculate an approximate carbon footprint for the skin cancer patient pathway. Ang et al [30] found the mean carbon emissions for nonmelanoma skin cancer surgical procedures ranged from 29.82 to 34.31 kgCO2eq. Our study found a similar estimate of 28.1 kgCO2eq (23.7% of overall pathway emissions) for the perioperative period (after excluding nuclear medicine). This therefore shows that calculating the emissions solely during the perioperative phase, while useful, underestimates the overall contribution of these procedures. We therefore recommend that future studies in other pathways do not overlook the stages surrounding the procedure itself.

The proportion of theater waste that is potentially recyclable is estimated to be 55% by weight [31]. In this study, only 11.2% of the total weight of waste was recycled. While waste minimization, recovery, and reuse should be priorities in line with circular economy principles, recycling remains important for increasing sustainability where waste is unavoidable. Suggestions to increase recycling proposed in the Royal College of Surgeons Green Surgery Report include decontamination of infectious waste beyond that already used for surgical instruments, increased use of high-quality recyclable materials in manufacturing that are easy to disassemble, and adoption of a closed-loop recycling process enabling recycled material to be reused for the same market purpose [32]. Adoption of circular economy principles and increased recycling also bring financial benefits, which can be used to incentivize hospitals to promote sustainability [33].

In the United Kingdom, the NHS’ long-term plan and the Royal College of Physicians (RCP) have urged a radical change to the way in which outpatient consultations are conducted [34,35]. An RCP survey found that 28% of doctors said that patients could have been seen virtually, and despite this, only 35% of outpatient clinics facilitate alternatives to face-to-face appointments. In this study, there were 5 times as many virtual appointments postoperatively as preoperatively. This likely represents a decreased need to examine patients postoperatively following histopathology results. While a good starting point, we propose a change in approach to outpatient clinics to make virtual consultations postoperatively the default, with clinical justification required for in-person consultations, to reduce emissions from patient travel and decrease pressure on waiting times through increased appointment availability.

Health care has the potential to become a model for sustainability through the implementation of practices to mitigate the dangers of the climate crisis while improving public health. To do so, studies must be performed to identify ways in which health care can become more sustainable. This research often requires contact with external departments not routinely encountered within clinical practice, such as estates, procurement, and even external suppliers. This can therefore lead to data limitations due to the inherent reliance on their carbon emission data. This hybrid study used a top-down approach for estimates of carbon emissions from diagnostic investigations (imaging, nuclear medicine, and histopathology) due to a lack of the required data for bottom-up calculations. This was a key limitation of the study; hence, the main takeaways from this study should be centered on process mapping rather than a specific numerical value for the overall carbon footprint of the pathway. Furthermore, the heterogeneity of patient care meant that further breakdown of carbon contributions per pathway stage could not be provided. Future work should include bottom-up calculations for diagnostics using frameworks set out by a recent life cycle assessment by Thiel et al [26] to further dissect the carbon hot spots of the skin cancer patient pathway and other surgical pathways, alongside the design of carbon calculators whereby patients and clinicians can calculate the carbon contribution of their care. In particular, data were sparse on life cycle assessments for single-photon emission CT–CT and this should be an area of focus.

This study process mapped and performed a life cycle assessment for the skin cancer patient pathway and estimated the carbon footprint to be 118.5 kgCO2eq. Process mapping highlighted multiple inefficiencies within the pathway and key carbon hot spots. Emissions came not just from the operative period but also from the diagnostic and follow-up periods. There were many contributing factors to the carbon footprint, the greatest of which were imaging and diagnostic investigations. Proposed strategies to increase sustainability focused on pathway modification, increased efficiency of MDT meetings, justification of imaging, adoption of circular economy principles in waste management, and use of virtual consultations. Future work should focus on performing eco audits on other cancer pathways and closed-loop audits of these interventions to assess the success of these strategies in decreasing carbon emissions, improving efficiency, and increasing health care sustainability.