The National Health Service (NHS) in England, as part of its net zero commitment by 2045, is increasingly focused on identifying carbon hotspots within its operations. Secondary and tertiary care are known to account for a significant portion of healthcare emissions, yet previous assessments have often relied on expenditure-based models. A recent study, presented in The Lancet Regional Health – Europe, pioneers the use of routine administrative data to estimate carbon emissions by clinical speciality, shedding light on the variation and intensity of emissions across the healthcare spectrum. The findings offer a foundation for more targeted and efficient sustainability interventions.
Understanding Emission Distribution in Hospital Care
The analysis covered over 17 million hospital admissions and nearly 102 million outpatient attendances across England during 2022/23. Outpatient activity contributed to 45% of measured carbon emissions, while admitted patient care accounted for 55%. Emergency admissions were the largest single contributor within inpatient care, responsible for 82% of emissions in that category. Among clinical specialities, general internal medicine, trauma and orthopaedics, and general surgery emerged as the highest emitters. Interestingly, some specialities, such as geriatric medicine and adult mental illness, had disproportionately high emissions relative to their activity levels, primarily due to long hospital stays or intensive resource use.
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Carbon emissions were calculated using a range of factors, including type of intervention, theatre time, bed occupancy, patient travel and emergency department visits. For outpatient care, a simpler model distinguished between in-person and virtual appointments. These detailed emissions profiles reveal not only which specialities contribute the most to the NHS’s carbon footprint, but also the underlying reasons, whether high procedural volume, intensive bed usage or reliance on energy-intensive equipment.
Speciality-Level and Activity-Specific Hotspots
This granular approach showed that certain activities—though not always dominant in volume—carry a significant carbon cost. Endoscopy, despite being conducted outside the operating theatre, was one of the highest-emitting procedures, highlighting its complexity and resource intensity. Similarly, dialysis and radiotherapy featured prominently due to their energy consumption and treatment frequency. Surgical procedures contributed to 4% of overall emissions, with hotspots in anaesthetic gases, single-use consumables and theatre energy use. The study also highlighted the challenges in assessing carbon from pharmaceuticals and diagnostics, as data limitations prevented accurate estimation of these emissions, despite their known environmental impact.
The limitations of existing data sources like Hospital Episode Statistics (HES) restricted insight into outpatient activity types and pharmacy-related emissions. However, within the available framework, carbon emissions were successfully attributed by speciality and activity, offering a clearer path to speciality-specific decarbonisation strategies. This aligns with the NHS’s broader goals of improving patient outcomes while reducing environmental impact.
Implications for Policy and Practice
The methodology employed demonstrates that administrative data can be leveraged to inform sustainability decisions at both operational and clinical levels. Specialities with high emissions per patient, such as geriatric and acute internal medicine, may benefit from improved discharge practices and pathway optimisation to reduce bed days. Moreover, integrating sustainability into clinical decision-making, such as through the use of virtual consultations or consolidating patient appointments, could substantially reduce travel-related emissions—particularly significant in outpatient care.
While some areas, such as critical care, appear less flexible due to clinical complexity, targeted measures like enhanced recovery protocols and avoidance of unnecessary admissions could still yield carbon savings. Tools and guidance developed for specific specialities, such as the bladder cancer care pathway in urology, serve as models for how more detailed procedure-level assessments could unlock further emissions reductions.
The study marks a critical step in aligning clinical care with environmental sustainability goals within the NHS. By mapping carbon emissions to specific specialities and activities, it provides a practical framework to identify priorities for intervention. While data gaps remain—especially around pharmaceuticals, diagnostics and outpatient care granularity—ongoing improvements in data collection and methodology will enable more precise and effective carbon reduction strategies. Ultimately, integrating carbon considerations into routine clinical and operational decisions is essential to achieving the NHS’s net zero ambitions without compromising care quality.
Source: The Lancet Regional Health – Europe
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