Carbon emissions from clinical activities by speciality in secondary and tertiary care in England: an exploratory cross-sectional analysis of routine administrative data.

Background: The National Health Service (NHS) in England has committed to achieving net zero carbon emissions by 2045. A key early step in this journey is to understand where opportunities to decarbonise healthcare exist. The aim of this paper is to explore the potential to use available activity and emissions intensity data to investigate the carbon emissions of different specialty-level clinical activities in secondary and tertiary care in the NHS in England. Methods: This was an exploratory, cross-sectional analysis of routine administrative data from secondary and tertiary care in the NHS in England. We included data for all patients admitted to hospital (including outpatient attendances, but excluding emergency attendances without subsequent admission) in England during the financial year 2022/23. The Hospital Episodes Statistics dataset and Theatre Productivity Data Collection were used. Carbon emissions factors were taken from published sources and linked to activity volumes to quantify the carbon emissions at a clinical activity level. Findings: Data for 17,024,278 hospital admissions and 101,973,593 outpatient attendances were analysed. Outpatient attendances accounted for 45% of the measured carbon emissions. Of the remaining 55% relating to admitted patient care, emergency admissions accounted for 45% (82% of admitted patient care), in-patient elective activity 7% and day case activity 3%. The top 20 clinical specialties accounted for 79% of the carbon emissions, with general internal medicine, trauma and orthopaedics and general surgery the three highest carbon emitting specialties. Interpretation: These data provide insight into the carbon emissions of specific elements of secondary and tertiary care activity in England. Such activity-level (and even more granular procedure-level and patient pathway-level) analysis is needed to inform carbon hotspot identification, intervention development and implementation to reduce the carbon emissions of care. As more granular data become available (e.g., on pharmaceutical use), such estimates will become more comprehensive. Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.