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Strategies and tactics to reduce the impact of healthcare on climate change: systematic review. OBJECTIVE: To review the international literature and assess the ways healthcare systems are mitigating and can mitigate their carbon footprint, which is currently estimated to be more than 4.4% of global emissions. DESIGN: Systematic review of empirical studies and grey literature to examine how healthcare services and institutions are limiting their greenhouse gas (GHG) emissions. DATA SOURCES: Eight databases and authoritative reports were searched from inception dates to November 2023. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Teams of investigators screened relevant publications against the inclusion criteria (eg, in English; discussed impact of healthcare systems on climate change), applying four quality appraisal tools, and results are reported in accordance with PRISMA (preferred reporting items for systematic reviews and meta-analyses). RESULTS: Of 33 737 publications identified, 32 998 (97.8%) were excluded after title and abstract screening; 536 (72.5%) of the remaining publications were excluded after full text review. Two additional papers were identified, screened, and included through backward citation tracking. The 205 included studies applied empirical (n=88, 42.9%), review (n=60, 29.3%), narrative descriptive (n=53, 25.9%), and multiple (n=4, 2.0%) methods. More than half of the publications (51.5%) addressed the macro level of the healthcare system. Nine themes were identified using inductive analysis: changing clinical and surgical practices (n=107); enacting policies and governance (n=97); managing physical waste (n=83); changing organisational behaviour (n=76); actions of individuals and groups (eg, advocacy, community involvement; n=74); minimising travel and transportation (n=70); using tools for measuring GHG emissions (n=70); reducing emissions related to infrastructure (n=63); and decarbonising the supply chain (n=48). CONCLUSIONS: Publications presented various strategies and tactics to reduce GHG emissions. These included changing clinical and surgical practices; using policies such as benchmarking and reporting at a facility level, and financial levers to reduce emissions from procurement; reducing physical waste; changing organisational culture through workforce training; supporting education on the benefits of decarbonisation; and involving patients in care planning. Numerous tools and frameworks were presented for measuring GHG emissions, but implementation and evaluation of the sustainability of initiatives were largely missing. At the macro level, decarbonisation approaches focused on energy grid emissions, infrastructure efficiency, and reducing supply chain emissions, including those from agriculture and supply of food products. Decarbonisation mechanisms at the micro and meso system levels ranged from reducing low value care, to choosing lower GHG options (eg, anaesthetic gases, rescue inhalers), to reducing travel. Based on these strategies and tactics, this study provides a framework to support the decarbonisation of healthcare systems. SYSTEMATIC REVIEW REGISTRATION: PROSPERO: CRD42022383719.

The direct and indirect human health impacts of climate change have been well documented over the past two decades. The 2015 Paris Agreement and subsequent research have painstakingly established the association between planetary and human health.1 2 3 4 However, until recently, less attention has been directed towards the impact healthcare systems have on climate change. This issue is gaining momentum, spurred on by the implementation of the Paris Agreement and the introduction of the UK National Health Service (NHS) net zero carbon strategy.5 6

d human health.1 2 3 4 However, until recently, less attention has been directed towards the impact healthcare systems have on climate change. This issue is gaining momentum, spurred on by the implementation of the Paris Agreement and the introduction of the UK National Health Service (NHS) net zero carbon strategy.5 6 In essence, healthcare systems occupy a special place; although they are on the frontlines in dealing with climate induced demand for healthcare, they are also major emitters.7 8 Healthcare systems must therefore address a predicament: maintenance of high quality care with the resilience and capacity to respond to escalating climate induced demands; and mitigation of their own, substantial contributions to the climate crisis. The action required to manage the complexities of the environmental and societal costs of delivering health services is not trivial. Healthcare systems, notably hospital facilities, are energy intensive, high consumption organisations that produce considerable quantities of waste.8 9 10 11 Although there is an irrefutable duty of care to patients and a fundamental commitment to do no harm at the point of delivery, healthcare systems have until recently remained largely unrecognised contributors to the climate crisis.12 However, healthcare systems are well positioned as environmental stewards to get their own house in order and promote benefits—lowering the collective carbon footprint while simultaneously improving long term health by reducing low value care.

recently remained largely unrecognised contributors to the climate crisis.12 However, healthcare systems are well positioned as environmental stewards to get their own house in order and promote benefits—lowering the collective carbon footprint while simultaneously improving long term health by reducing low value care. That said, healthcare systems currently lag behind other service sectors in reducing carbon emissions.6 13 To be compliant with the Paris Agreement and contribute to the Intergovernmental Panel on Climate Change’s target of limiting global warming to 1.5°C above preindustrial levels, healthcare must play its part, aiming for net zero carbon emissions by 2050.13 14 15 There is a need to act in a swift and decisive manner because humanity has a limited window to achieve significant progress in reducing carbon emissions or irreversible changes will exceed the boundaries of the planet.16

strial levels, healthcare must play its part, aiming for net zero carbon emissions by 2050.13 14 15 There is a need to act in a swift and decisive manner because humanity has a limited window to achieve significant progress in reducing carbon emissions or irreversible changes will exceed the boundaries of the planet.16 Most estimates place average global emissions from healthcare at about 4.4%, with a country range of 4-8.5%.15 As confronting as these numbers are, it is possible they will get worse before they get better.17 More frequent large scale events stimulated by climate change (eg, bushfires, floods, cyclones, heatwaves, and other weather sequelae) will require more carbon inducing care, placing additional, often overwhelming loads on overstretched healthcare systems grappling to contend with the current high burden of chronic diseases, non-communicable diseases (such as cardiovascular diseases), communicable diseases, constant introduction of new interventions and technologies as we discover new ways to manage disease, and ageing populations.10 11 18 19 With slow progress on reduction strategies, increased demand on healthcare systems in turn generates further environmental impacts in a vicious cycle (fig 1). Positive feedback loop reflecting current association between the healthcare system and climate change. GHG=greenhouse gas

Most estimates place average global emissions from healthcare at about 4.4%, with a country range of 4-8.5%.15 As confronting as these numbers are, it is possible they will get worse before they get better.17 More frequent large scale events stimulated by climate change (eg, bushfires, floods, cyclones, heatwaves, and other weather sequelae) will require more carbon inducing care, placing additional, often overwhelming loads on overstretched healthcare systems grappling to contend with the current high burden of chronic diseases, non-communicable diseases (such as cardiovascular diseases), communicable diseases, constant introduction of new interventions and technologies as we discover new ways to manage disease, and ageing populations.10 11 18 19 With slow progress on reduction strategies, increased demand on healthcare systems in turn generates further environmental impacts in a vicious cycle (fig 1). Positive feedback loop reflecting current association between the healthcare system and climate change. GHG=greenhouse gas Against that backdrop, we sought to examine the quality and quantity of global evidence on ways in which healthcare systems contribute to climate change and the proposed and implemented ways of reducing the effects of healthcare systems on the climate. Table 1 presents our key terms. Glossary of terms

In this review, we assessed the quality and quantity of evidence on ways in which healthcare systems contribute to climate change and the approaches, models, and tools available to decarbonise healthcare systems. The review was prospectively registered on PROSPERO (CRD42022383719) and reported in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines (supplementary materials 1 and 2).35 The search strategy was designed by the review team in conjunction with a research librarian, and run across eight electronic databases. Seven of these databases were searched from their respective inception dates to November 2023: Business Source Premier, CINAHL, Cochrane Reviews, Embase, Health Business (EBSCO), Medline, and Web of Science. Scopus was searched from 1990 to November 2023. Supplementary material 3 gives more details on the search terms.

Seven of these databases were searched from their respective inception dates to November 2023: Business Source Premier, CINAHL, Cochrane Reviews, Embase, Health Business (EBSCO), Medline, and Web of Science. Scopus was searched from 1990 to November 2023. Supplementary material 3 gives more details on the search terms. Publications were eligible if they were full text articles in peer reviewed journals. All study designs (eg, case studies, reviews) were included. Reports from authoritative international agencies (eg, World Health Organization, World Bank, United Nations, and Organisation for Economic Co-operation and Development) or government reports at a federal or national level were also eligible if assessed to be of suitable quality. A primary focus on the effects of human healthcare systems on climate change was required. Articles were excluded if they were not available in English, were not published as full papers, or did not have a primary focus on healthcare systems’ effects on or contribution to climate change. Supplementary material 4 presents full inclusion and exclusion criteria.

ealthcare systems on climate change was required. Articles were excluded if they were not available in English, were not published as full papers, or did not have a primary focus on healthcare systems’ effects on or contribution to climate change. Supplementary material 4 presents full inclusion and exclusion criteria. Records identified in the database search were imported into Rayyan, a screening software tool,36 and duplicates removed. For inter-rater reliability, pilot screening of titles and abstracts was conducted on a set of 200 randomly selected publications and any resulting discrepancies were resolved by the group. In our original review protocol, it was planned that six investigators would screen records in pairs. However, given the large volume of literature identified in the search, 15 investigators screened records in pairs. The full set of titles and abstracts retrieved from searches were then independently double screened for inclusion by investigators working in teams of two or three (EL, LE, EM, GD, CLS, AC, KB-C, SW, GF, RP, LP, HRA, SS, CR, AP). The full texts of the remaining publications were then duplicate screened against the inclusion criteria to ensure consistency in the final set of included texts. Supplementary material 5 presents reasons for exclusion during the full text review. Regular meetings took place to resolve any disagreements by consensus at each step of the process, with JB available as arbiter.

uplicate screened against the inclusion criteria to ensure consistency in the final set of included texts. Supplementary material 5 presents reasons for exclusion during the full text review. Regular meetings took place to resolve any disagreements by consensus at each step of the process, with JB available as arbiter. Data extraction and quality appraisal were conducted independently by investigators, and verified during synthesis processes. Four quality appraisal tools were applied to assess the quality of included publications: Joanna Briggs Institute critical appraisal checklist for systematic reviews and research synthesis37; Mixed-Methods Appraisal Tool (MMAT)38; Scale for the quality Assessment of Narrative Reviews (SANRA)39; and Authority, Accuracy, Coverage, Objectivity, Date, Significance (AACODS) tool for evaluation and critical appraisal of grey literature.40 After initial appraisal, the quality of each article was assigned to one of four categories: critically low, low, moderate, high. Articles determined to be of critically low quality were excluded from analysis; supplementary materials 6-10 provide further details.

evaluation and critical appraisal of grey literature.40 After initial appraisal, the quality of each article was assigned to one of four categories: critically low, low, moderate, high. Articles determined to be of critically low quality were excluded from analysis; supplementary materials 6-10 provide further details. A purpose built data extraction workbook was developed in Microsoft Excel. Data extraction variables included publication details (author, title, year, country of publication), healthcare system level (micro, meso, macro), healthcare system sector (eg, primary care, surgery, mental health), and measurement of climate impact (eg, carbon footprint). A thematic analysis of the extracted data was performed using an inductive approach to identify themes emerging from the literature.41 One reviewer (SW) first familiarised themselves with all extracted data, and then created a set of six initial broad themes and 24 subthemes using inductive thematic analysis.41 A subgroup of five reviewers (CLS, KBC, GD, SW, EL) discussed and revised the initial coding of themes to 12 themes. The whole authorship team conducted a review of these broad themes for content and accuracy, and the final nine themes were then reviewed by the senior author (JB). Once the nine broad themes had been developed, a subgroup of reviewers (CLS, KBC, GD, SW, EL, EM) met to code the data within each broad theme into appropriate subthemes, again using an inductive thematic analysis. Two broad categories were also developed to frame the themes as avenues of enacting change (overarching strategies), or specific approaches for reducing GHG emissions in healthcare systems (decarbonisation tactics). The whole authorship team reviewed and approved all categories and subthemes, which were finalised by the senior author (JB). Supplementary materials 11-13 provide details.

ues of enacting change (overarching strategies), or specific approaches for reducing GHG emissions in healthcare systems (decarbonisation tactics). The whole authorship team reviewed and approved all categories and subthemes, which were finalised by the senior author (JB). Supplementary materials 11-13 provide details. This research did not focus on any specific patient population. Although no patients were directly involved in setting the research question or conducting the review, we ensure we have healthcare consumers’ input, expertise and advice on the progress of our research at the intersection of climate change, health, and healthcare, which feeds into and shapes all our work in this area. Healthcare consumers are an integral part of our results dissemination strategy.

Data extraction and quality appraisal were conducted independently by investigators, and verified during synthesis processes. Four quality appraisal tools were applied to assess the quality of included publications: Joanna Briggs Institute critical appraisal checklist for systematic reviews and research synthesis37; Mixed-Methods Appraisal Tool (MMAT)38; Scale for the quality Assessment of Narrative Reviews (SANRA)39; and Authority, Accuracy, Coverage, Objectivity, Date, Significance (AACODS) tool for evaluation and critical appraisal of grey literature.40 After initial appraisal, the quality of each article was assigned to one of four categories: critically low, low, moderate, high. Articles determined to be of critically low quality were excluded from analysis; supplementary materials 6-10 provide further details.

This research did not focus on any specific patient population. Although no patients were directly involved in setting the research question or conducting the review, we ensure we have healthcare consumers’ input, expertise and advice on the progress of our research at the intersection of climate change, health, and healthcare, which feeds into and shapes all our work in this area. Healthcare consumers are an integral part of our results dissemination strategy.

Electronic database searches identified 33 737 publications, 15 793 of which were duplicates, leaving 17 944 publications for title and abstract screening; 739 studies met the inclusion criteria for full text screening. Of these, 28 were excluded because they could not be retrieved, leaving 711 texts to be screened (fig 2). Two additional papers were identified, screened, and included through backward citation tracking. Preferred reporting items for systematic reviews and meta-analyses (PRISMA) diagram Most of the articles in this review were appraised as high (n=112, 54.6%) or moderate (n=80, 39.0%) quality. Only 13 articles (6.3%) were identified as lower quality but were included because they provided valuable information for the review. Seven studies were considered ineligible based on critically low quality appraisal ratings (supplementary materials 6-10). After full text screening and quality appraisal, 205 publications were included (fig 2). Included publications were categorised by study design (table 2): empirical studies; reviews including narrative, scoping, and systematic; non-empirical “narrative descriptive” publications (eg, case studies, reports); and those applying multiple methods. Studies were also categorised based on the level of the healthcare system to which they pertained: micro, meso, or macro (table 2; see table 1 for full definitions). Overview of key characteristics of included publications (n=205) If applicable, publications were categorised into more than one category; therefore, the healthcare system level total does not add up to 100%.

Included publications were categorised by study design (table 2): empirical studies; reviews including narrative, scoping, and systematic; non-empirical “narrative descriptive” publications (eg, case studies, reports); and those applying multiple methods. Studies were also categorised based on the level of the healthcare system to which they pertained: micro, meso, or macro (table 2; see table 1 for full definitions). Overview of key characteristics of included publications (n=205) If applicable, publications were categorised into more than one category; therefore, the healthcare system level total does not add up to 100%. High income countries were over-represented in the included publications (n=101, 69.2%, excluding reviews). The most commonly discussed country was the United States (n=27, 13.2%), followed by the UK (n=21, 10.2%), Australia (n=17, 8.3%), and Canada (n=14, 6.8%). Figure 3 depicts the study setting by country. Many publications (n=30, 14.6%) focused on the macro level without discussing a specific country or region.6 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 Setting of included empirical publications by country. Some publications refer to more than one country. Countries were counted for all empirical publications Most included records were published in recent years (fig 4), with 85.4% (n=175) from 2019 onwards, indicating the growing interest in this topic. Included publications by year

Setting of included empirical publications by country. Some publications refer to more than one country. Countries were counted for all empirical publications Most included records were published in recent years (fig 4), with 85.4% (n=175) from 2019 onwards, indicating the growing interest in this topic. Included publications by year A wide range of healthcare related topics were discussed, including surgery (n=36)24 27 51 54 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102; internal medicine specialties (ie, renal services, gynaecological services; n=18)23 57 75 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117; digital health (n=15)59 66 71 118 119 120 121 122 123 124 125 126 127 128 129; primary care (n=15)53 56 63 75 130 131 132 133 134 135 136 137 138 139 140; hospitals (n=14)82 92 141 142 143 144 145 146 147 148 149 150 151 152; supply chains (eg, procurement; n=10)42 44 153 154 155 156 157 158 159 160; oncology (n=8)48 58 161 162 163 164 165 166; pharmaceuticals (n=7)45 47 167 168 169 170 171; diagnostics (n=6)52 172 173 174 175 176; chronic condition treatment (n=5)28 61 177 178 179; workforce (n=5)180 181 182 183 184; pathology services (n=5)75 174 185 186 187; dentistry (n=4)60 188 189 190; critical care (n=3)90 191 192; clinical trials (n=2)67 193; emergency medical services (n=2)26 194; mental health services (n=2)195 196; outpatient care (n=2)197 198; screening (n=2)199 200; travel related to doctors’ medical education (n=1)201; and palliative care (n=1).202 Fifty papers examined the system as a whole, taking a macro perspective.6 7 11 19 25 43 46 49 50 55 62 64 65 68 69 70 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236

doctors’ medical education (n=1)201; and palliative care (n=1).202 Fifty papers examined the system as a whole, taking a macro perspective.6 7 11 19 25 43 46 49 50 55 62 64 65 68 69 70 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 Twenty nine (14.1%) publications specifically used terminology that refers to GHG emissions according to three emission scopes defined by the Greenhouse Gas Protocol237 (direct emissions, indirect emissions from energy use, indirect supply chain emissions).7 27 44 45 47 48 50 55 65 68 69 81 85 125 142 152 166 172 184 193 197 200 202 207 209 219 224 229 232 Table 3 presents definitions of the three scopes. Three scopes of carbon footprint Source: Definitions derived from Greenhouse Gas Protocol.237

Twenty nine (14.1%) publications specifically used terminology that refers to GHG emissions according to three emission scopes defined by the Greenhouse Gas Protocol237 (direct emissions, indirect emissions from energy use, indirect supply chain emissions).7 27 44 45 47 48 50 55 65 68 69 81 85 125 142 152 166 172 184 193 197 200 202 207 209 219 224 229 232 Table 3 presents definitions of the three scopes. Three scopes of carbon footprint Source: Definitions derived from Greenhouse Gas Protocol.237 Forty eight publications developed or applied specific models or tools to measure healthcare emissions; some publications used several models or tools (table 4). Models included life cycle assessment (LCA; n=27),60 76 84 104 107 111 119 122 128 130 141 142 155 162 173 174 175 179 186 190 193 200 209 212 213 223 231 economic input-output LCA (n=2),197 212 LCA multiregion input-output models (n=1),25 environmentally extended input-output models (n=6),7 11 24 77 213 232 environmentally extended multiregional input-output model (n=4),43 44 231 232 and the Bilan Carbone model (n=1).166 Tools used in the literature included carbon calculators (n=6),52 101 115 121 165 176 Carbon Trust recommendations (n=1),26 the Eyefficiency tool (n=1),89 the Pollard model (n=1),188 the Ringelmann smoke chart (n=1),157 and the US Environmental Protection Agency’s waste reduction model (n=1).144 Other studies (n=16) used publicly available datasets (eg, UK Department of Business, Energy, and Industrial Strategy conversion factor data; environmental impact data provided by the German Federal Environment Agency), or previously published literature to quantify GHG emissions in their facilities.74 83 94 99 110 113 123 126 129 148 161 162 163 168 178 202

able datasets (eg, UK Department of Business, Energy, and Industrial Strategy conversion factor data; environmental impact data provided by the German Federal Environment Agency), or previously published literature to quantify GHG emissions in their facilities.74 83 94 99 110 113 123 126 129 148 161 162 163 168 178 202 Tools for measuring healthcare emissions from empirical studies Models are general method used to measure GHG emissions at a certain level, whereas tools were developed to measure emissions using one or more models. GHG=greenhouse gas; US EPA=United States Environmental Protection Agency. Some publications used several models. From the thematic analysis, nine themes emerged across the included publications, which were then grouped into one of two categories: overarching strategies (table 5) or decarbonisation tactics (table 6). The most frequently discussed overarching strategy was the need for effective policies and governance surrounding healthcare sustainability (n=97) and the most common decarbonisation tactic was changing clinical and surgical practices (n=107). Papers discussing numerous themes or subthemes were included in several categories. Publications in the overarching strategies category, grouped into themes Overarching strategies definition: mechanisms for healthcare system improvement relating to climate change. GHG=greenhouse gas. Publications in the decarbonisation tactics category, grouped into themes Decarbonisation tactics definition: tactics for reducing greenhouse gas emissions within healthcare systems. GHG=greenhouse gas.

Publications in the overarching strategies category, grouped into themes Overarching strategies definition: mechanisms for healthcare system improvement relating to climate change. GHG=greenhouse gas. Publications in the decarbonisation tactics category, grouped into themes Decarbonisation tactics definition: tactics for reducing greenhouse gas emissions within healthcare systems. GHG=greenhouse gas. The need for policies and incentives to promote, guide, monitor, or evaluate changes at the country, state, and facility level was discussed in 97 publications6 7 11 19 23 25 42 43 44 45 46 47 48 49 50 51 55 56 57 58 59 61 63 64 65 67 68 69 70 71 73 76 79 88 89 95 96 103 104 105 109 111 112 114 115 117 120 123 124 125 127 128 130 133 136 138 142 143 151 152 154 159 162 166 168 170 171 173 179 180 184 188 191 192 193 200 201 203 205 206 207 208 209 210 212 213 216 217 218 219 220 221 224 231 232 233 234; 39.2% of the publications discussing this theme were empirical studies. The most common strategy focused on priority setting and leadership from national and international bodies (n=51), such as integrating sustainability into policy or setting long term sustainability goals across organisations.6 7 11 19 43 46 50 51 56 57 59 63 64 65 67 70 76 79 95 96 104 105 109 111 114 115 120 125 127 128 130 133 138 143 152 154 166 170 184 188 206 209 210 216 217 218 220 221 231 232 234 This was followed by publications (n=27) that suggested mandating evaluations, benchmarking, and reporting of the carbon footprint for healthcare organisations to strengthen the evidence base for future decision making.6 7 23 45 55 58 61 68 70 73 88 124 136 142 151 159 168 173 179 205 207 208 212 213 216 219 221 An equal number of publications (n=21 each) highlighted using financial policy and incentives for sustainable healthcare processes6 42 43 44 48 49 70 73 89 96 123 133 138 143 162 171 180 200 221 224 233 and the need for a multisectoral approach to mitigate the carbon footprint of healthcare,7 23 56 69 73 89 96 103 112 117 162 191 192 201 203 205 210 217 220 221 233 such as collaborations between large healthcare organisations. Fifteen publications recommended setting targeted emissions reductions.7 11 19 25 45 46 47 58 70 71 89 136 193 218 219

ctoral approach to mitigate the carbon footprint of healthcare,7 23 56 69 73 89 96 103 112 117 162 191 192 201 203 205 210 217 220 221 233 such as collaborations between large healthcare organisations. Fifteen publications recommended setting targeted emissions reductions.7 11 19 25 45 46 47 58 70 71 89 136 193 218 219 Organisational change to develop a future ready workforce was dealt with in 76 publications.24 25 27 46 48 49 50 57 58 63 65 68 69 70 71 73 75 77 79 80 81 83 86 91 93 99 102 103 105 110 112 114 116 127 130 133 135 136 137 138 142 143 150 151 152 154 165 166 171 172 174 178 179 180 181 182 185 187 191 192 195 196 199 202 205 206 207 210 212 216 220 221 228 233 234 235 Roughly 30.3% of the publications discussing this theme were empirical studies. Ongoing education and training within healthcare organisations and tertiary institutions was identified in 59 publications as a way of ensuring the workforce is aware of and equipped for sustainability challenges.24 25 48 49 50 57 63 65 68 69 73 75 77 79 81 83 86 91 99 102 103 110 112 114 116 127 130 133 135 137 138 142 143 150 151 152 165 166 171 172 174 178 179 180 185 187 192 195 196 202 205 206 207 210 212 220 228 233 235 Publications discussing organisational leadership focused on implementing multidisciplinary teams, “green champions,” and other organisational role models to manage sustainability at different levels of the healthcare system and empower employee decision making (n=26).27 46 58 63 70 71 77 80 93 105 127 133 135 136 152 154 165 181 182 185 191 196 199 216 221 234

ership focused on implementing multidisciplinary teams, “green champions,” and other organisational role models to manage sustainability at different levels of the healthcare system and empower employee decision making (n=26).27 46 58 63 70 71 77 80 93 105 127 133 135 136 152 154 165 181 182 185 191 196 199 216 221 234 The literature outlined several important roles for individuals and groups in reducing healthcare’s carbon footprint (n=74)7 19 28 43 48 49 50 51 53 56 57 58 59 61 63 64 65 66 67 69 71 73 81 85 86 88 89 90 91 96 98 102 103 107 108 112 114 116 117 127 130 133 134 135 137 139 142 143 151 160 162 168 171 177 180 181 183 184 192 195 196 210 212 215 216 218 219 220 221 226 229 232 233 236; 20.3% of the publications discussing this theme were empirical studies. Promoting change through advocacy, lobbying, and open support of sustainability initiatives was the focus of 45 publications,7 48 49 50 51 53 58 61 64 65 66 67 71 81 85 86 88 89 90 96 98 103 107 114 116 117 127 133 134 135 139 142 151 171 180 181 183 184 192 195 196 216 218 232 233 including the need for community involvement and education when enhancing the sustainability of healthcare practices (n=21).43 53 56 81 90 103 112 130 133 151 160 168 192 210 212 218 221 229 232 233 236 Several publications emphasised individual responsibility as a key factor in making change (n=15), particularly through engaging with low carbon healthcare and living an active lifestyle.57 59 63 73 81 89 91 96 103 143 160 162 192 220 233 Additionally, 15 articles identified benefits of reducing GHGs in the health system, which included financial savings and reducing disease burden.19 28 50 69 96 102 107 108 112 137 177 212 215 219 226

engaging with low carbon healthcare and living an active lifestyle.57 59 63 73 81 89 91 96 103 143 160 162 192 220 233 Additionally, 15 articles identified benefits of reducing GHGs in the health system, which included financial savings and reducing disease burden.19 28 50 69 96 102 107 108 112 137 177 212 215 219 226 The impetus to develop, use, and standardise tools for measuring and monitoring GHG emissions was a prominent theme (n=70 publications).6 7 11 19 26 43 44 45 47 48 51 58 59 61 62 66 68 69 71 73 75 77 79 84 88 96 103 104 105 107 109 112 114 124 125 137 139 142 146 148 149 154 163 164 171 177 188 192 193 194 200 205 207 208 209 211 212 216 217 218 219 221 222 224 225 227 228 230 231 234 Nearly 37.1% of the publications discussing this theme were empirical studies. Evaluative tools, along with existing models such as LCA, can be used to improve decision making on procurement and services, and was a feature of 43 publications.6 43 47 58 59 62 66 68 73 75 77 79 84 88 96 104 105 107 109 112 124 137 139 142 146 149 154 164 192 200 205 208 211 212 216 217 218 224 225 227 230 231 234 Developing tools to measure GHG emissions and monitor the movement of materials was discussed in 25 publications.7 11 19 26 43 44 69 103 124 125 146 171 177 188 193 194 207 209 211 219 221 222 225 227 228 Several publications (n=17) emphasised the need for standardised platforms for reporting and comparing the sustainability of products or processes to enable healthcare organisations to make informed decisions about their current practices.7 26 45 47 48 51 61 71 107 114 148 154 163 177 207 211 219

19 221 222 225 227 228 Several publications (n=17) emphasised the need for standardised platforms for reporting and comparing the sustainability of products or processes to enable healthcare organisations to make informed decisions about their current practices.7 26 45 47 48 51 61 71 107 114 148 154 163 177 207 211 219 Changing clinical and surgical practices as a solution for reducing healthcare’s carbon footprint was advocated in 107 publications6 7 11 23 24 25 27 28 42 43 48 50 51 52 54 55 57 61 63 66 68 69 71 73 74 75 77 78 79 81 82 83 84 85 86 87 90 91 93 94 96 97 98 99 100 101 102 103 106 107 108 109 112 113 114 116 120 126 128 129 130 133 135 138 139 142 143 148 149 151 152 159 161 163 165 166 167 168 169 170 171 173 174 175 177 178 179 183 185 186 189 190 191 192 196 205 212 214 217 224 227 229 230 232 233 234 236; 37.4% of the publications discussing this theme were empirical studies. This solution included replacing high GHG practices with lower GHG options (n=80),11 23 27 28 43 48 54 57 61 63 68 71 73 74 75 77 78 79 81 82 83 84 85 86 87 90 91 93 94 96 97 98 100 102 103 106 107 112 113 114 120 126 128 129 133 135 138 139 148 149 152 159 161 163 165 166 167 168 170 171 173 174 177 178 179 183 189 190 192 196 214 217 224 227 229 230 232 233 234 236 such as choosing anaesthetic gas types and systems with lower carbon footprints.54 71 73 81 83 85 86 96 100 229 This advocation was also seen in primary care settings (n=6).63 130 133 135 138 139 As a way of minimising healthcare usage, and thus reducing healthcare’s carbon footprint, 41 publications reinforced the need to assess clinical practices for low value care.6 7 24 28 42 51 52 55 66 68 69 75 77 79 93 97 99 101 109 116 130 142 149 151 152 169 174 175 177 179 185 186 190 191 192 205 212 214 224 229 233 This included identifying and reducing unnecessary processes or procedures, minimising drug overprescription, or encouraging a preventative care approach to reduce the need for health services. Reducing water usage during procedures, disinfection and sterilisations, laundry, recycling water, and practising water efficiency were also suggested in six publications.23 25 50 108 143 189

rocedures, minimising drug overprescription, or encouraging a preventative care approach to reduce the need for health services. Reducing water usage during procedures, disinfection and sterilisations, laundry, recycling water, and practising water efficiency were also suggested in six publications.23 25 50 108 143 189 Dealing with waste was a focus of 83 publications11 25 43 47 48 49 50 51 54 55 57 60 61 63 67 72 73 77 78 80 81 82 84 85 86 88 89 91 93 95 96 97 98 100 101 102 104 105 107 110 112 114 116 135 138 142 143 144 149 150 151 152 153 154 155 157 159 160 169 171 177 183 189 190 191 192 198 199 206 210 211 217 218 219 222 223 224 228 229 232 233 234 236; 32.5% of the publications discussing this theme were empirical studies. This theme included waste minimisation methods (n=71),11 25 43 47 48 49 50 51 54 55 57 60 61 63 67 72 73 77 78 80 82 84 85 88 91 95 96 97 98 100 101 102 104 105 107 110 112 116 135 138 142 143 144 149 151 152 154 155 159 160 169 171 177 183 189 190 191 192 198 206 211 217 218 219 222 224 228 229 232 233 234 such as reducing, reusing, and recycling medical equipment, and using reusable alternatives over disposable items. Several publications highlighted the need for effective segregation and disposal of waste (n=29),50 57 73 77 80 81 82 86 88 89 93 95 107 114 143 144 150 151 153 157 160 177 183 199 206 210 223 232 236 including choosing disposal methods such as incineration that help minimise carbon emissions.

es over disposable items. Several publications highlighted the need for effective segregation and disposal of waste (n=29),50 57 73 77 80 81 82 86 88 89 93 95 107 114 143 144 150 151 153 157 160 177 183 199 206 210 223 232 236 including choosing disposal methods such as incineration that help minimise carbon emissions. Patient or clinical travel and transportation was emphasised as an important and addressable source of carbon emissions in 70 publications.6 7 24 43 47 48 51 55 59 61 63 69 71 73 74 79 84 85 86 93 94 95 96 105 109 114 117 119 120 121 122 124 125 126 127 128 131 132 135 137 140 142 148 152 156 161 163 165 166 171 172 174 176 188 190 191 192 193 195 196 197 201 202 217 224 226 228 229 232 233 Some 42.9% of the publications discussing this theme were empirical studies. Using carbon efficient models of care was seen as a method to reduce emissions (n=41), for example, telemedicine or home based treatment options.6 24 43 47 48 51 59 63 71 73 74 79 84 94 95 96 105 109 119 121 122 124 125 126 128 132 135 148 161 163 165 171 172 176 188 191 195 196 217 228 229 A further 25 publications discussed alternative forms of transportation (eg, car sharing, buses, trains, and active travel such as cycling) for patients and clinicians.7 47 55 69 79 105 114 121 131 137 140 142 152 161 166 174 176 190 192 197 202 224 226 232 233 Streamlining medical services, such as emergency service coordination, redesigning schedules for clinicians to enhance ride share and closing sites with lower use, was discussed in 14 publications.61 79 86 93 127 131 132 148 156 161 166 176 188 193 Several papers (n=13) also highlighted reducing professionals’ travel (eg, clinicians, researchers, industry partners) for conferences and education as a decarbonisation method.43 47 51 63 85 117 120 171 191 195 201 224 228

lower use, was discussed in 14 publications.61 79 86 93 127 131 132 148 156 161 166 176 188 193 Several papers (n=13) also highlighted reducing professionals’ travel (eg, clinicians, researchers, industry partners) for conferences and education as a decarbonisation method.43 47 51 63 85 117 120 171 191 195 201 224 228 This theme had the most implementation evaluations. These studies often highlighted reductions in carbon emissions resulting from teleconferencing or telemedicine,122 163 176 and they also tended to be of high quality.

lower use, was discussed in 14 publications.61 79 86 93 127 131 132 148 156 161 166 176 188 193 Several papers (n=13) also highlighted reducing professionals’ travel (eg, clinicians, researchers, industry partners) for conferences and education as a decarbonisation method.43 47 51 63 85 117 120 171 191 195 201 224 228 This theme had the most implementation evaluations. These studies often highlighted reductions in carbon emissions resulting from teleconferencing or telemedicine,122 163 176 and they also tended to be of high quality. Sixty three papers recommended improvements to healthcare infrastructure26 27 43 47 50 55 57 58 59 61 63 69 72 73 80 81 84 88 92 93 96 97 98 108 109 112 114 117 118 135 141 142 143 145 146 147 151 152 160 161 171 174 175 184 192 193 194 195 202 206 207 210 211 212 218 221 224 226 228 229 232 234 235; 33.3% of the publications discussing this theme were empirical studies. Improving the energy efficiency of healthcare facilities such as hospitals was a feature of 40 publications.47 50 55 57 61 63 69 72 73 80 81 92 93 97 98 109 112 135 141 142 143 146 147 152 160 171 192 193 194 207 210 211 212 218 221 224 229 232 234 235 For example, consideration of design features such as insulation and passive shading options can help reduce reliance on electrical heating and cooling, and therefore reduce GHG emissions. Thirty four publications advocated for using energy conservation measures—such as turning off appliances when not in use—to help minimise carbon emissions at a facility level.26 27 43 57 58 59 61 63 73 84 88 96 97 108 114 117 118 135 143 145 151 152 161 174 175 184 194 195 202 206 221 226 228 229

reduce GHG emissions. Thirty four publications advocated for using energy conservation measures—such as turning off appliances when not in use—to help minimise carbon emissions at a facility level.26 27 43 57 58 59 61 63 73 84 88 96 97 108 114 117 118 135 143 145 151 152 161 174 175 184 194 195 202 206 221 226 228 229 Forty eight papers proposed decarbonising the supply chains as a way of reducing GHG emissions.7 25 26 42 43 44 47 50 54 55 56 59 65 73 84 85 87 89 98 104 105 110 112 114 127 136 139 142 143 151 152 158 171 175 183 193 194 197 204 210 212 215 218 224 229 232 234 235 Roughly 39.6% of the publications discussing this theme were empirical studies. Numerous publications (n=43) focused on ways to reduce the carbon footprint by deploying sustainable production and procurement mechanisms within supply chains, such as using sustainable or local sources of food supply, or using supply chains with low emissions.7 25 42 43 44 47 50 54 55 56 59 65 73 84 85 98 104 105 110 112 114 127 136 139 142 143 151 152 158 171 175 183 193 197 210 212 215 218 224 229 232 234 235 Decarbonising the sources of energy for healthcare by using renewable sources rather than fossil fuel sources and monitoring energy grid consumption was noted in 10 publications.7 26 50 87 89 158 194 204 212 232

Electronic database searches identified 33 737 publications, 15 793 of which were duplicates, leaving 17 944 publications for title and abstract screening; 739 studies met the inclusion criteria for full text screening. Of these, 28 were excluded because they could not be retrieved, leaving 711 texts to be screened (fig 2). Two additional papers were identified, screened, and included through backward citation tracking. Preferred reporting items for systematic reviews and meta-analyses (PRISMA) diagram Most of the articles in this review were appraised as high (n=112, 54.6%) or moderate (n=80, 39.0%) quality. Only 13 articles (6.3%) were identified as lower quality but were included because they provided valuable information for the review. Seven studies were considered ineligible based on critically low quality appraisal ratings (supplementary materials 6-10). After full text screening and quality appraisal, 205 publications were included (fig 2).

able datasets (eg, UK Department of Business, Energy, and Industrial Strategy conversion factor data; environmental impact data provided by the German Federal Environment Agency), or previously published literature to quantify GHG emissions in their facilities.74 83 94 99 110 113 123 126 129 148 161 162 163 168 178 202 Tools for measuring healthcare emissions from empirical studies Models are general method used to measure GHG emissions at a certain level, whereas tools were developed to measure emissions using one or more models. GHG=greenhouse gas; US EPA=United States Environmental Protection Agency. Some publications used several models.

Included publications were categorised by study design (table 2): empirical studies; reviews including narrative, scoping, and systematic; non-empirical “narrative descriptive” publications (eg, case studies, reports); and those applying multiple methods. Studies were also categorised based on the level of the healthcare system to which they pertained: micro, meso, or macro (table 2; see table 1 for full definitions). Overview of key characteristics of included publications (n=205) If applicable, publications were categorised into more than one category; therefore, the healthcare system level total does not add up to 100%.

High income countries were over-represented in the included publications (n=101, 69.2%, excluding reviews). The most commonly discussed country was the United States (n=27, 13.2%), followed by the UK (n=21, 10.2%), Australia (n=17, 8.3%), and Canada (n=14, 6.8%). Figure 3 depicts the study setting by country. Many publications (n=30, 14.6%) focused on the macro level without discussing a specific country or region.6 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 Setting of included empirical publications by country. Some publications refer to more than one country. Countries were counted for all empirical publications

A wide range of healthcare related topics were discussed, including surgery (n=36)24 27 51 54 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102; internal medicine specialties (ie, renal services, gynaecological services; n=18)23 57 75 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117; digital health (n=15)59 66 71 118 119 120 121 122 123 124 125 126 127 128 129; primary care (n=15)53 56 63 75 130 131 132 133 134 135 136 137 138 139 140; hospitals (n=14)82 92 141 142 143 144 145 146 147 148 149 150 151 152; supply chains (eg, procurement; n=10)42 44 153 154 155 156 157 158 159 160; oncology (n=8)48 58 161 162 163 164 165 166; pharmaceuticals (n=7)45 47 167 168 169 170 171; diagnostics (n=6)52 172 173 174 175 176; chronic condition treatment (n=5)28 61 177 178 179; workforce (n=5)180 181 182 183 184; pathology services (n=5)75 174 185 186 187; dentistry (n=4)60 188 189 190; critical care (n=3)90 191 192; clinical trials (n=2)67 193; emergency medical services (n=2)26 194; mental health services (n=2)195 196; outpatient care (n=2)197 198; screening (n=2)199 200; travel related to doctors’ medical education (n=1)201; and palliative care (n=1).202 Fifty papers examined the system as a whole, taking a macro perspective.6 7 11 19 25 43 46 49 50 55 62 64 65 68 69 70 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236

Twenty nine (14.1%) publications specifically used terminology that refers to GHG emissions according to three emission scopes defined by the Greenhouse Gas Protocol237 (direct emissions, indirect emissions from energy use, indirect supply chain emissions).7 27 44 45 47 48 50 55 65 68 69 81 85 125 142 152 166 172 184 193 197 200 202 207 209 219 224 229 232 Table 3 presents definitions of the three scopes. Three scopes of carbon footprint Source: Definitions derived from Greenhouse Gas Protocol.237

Forty eight publications developed or applied specific models or tools to measure healthcare emissions; some publications used several models or tools (table 4). Models included life cycle assessment (LCA; n=27),60 76 84 104 107 111 119 122 128 130 141 142 155 162 173 174 175 179 186 190 193 200 209 212 213 223 231 economic input-output LCA (n=2),197 212 LCA multiregion input-output models (n=1),25 environmentally extended input-output models (n=6),7 11 24 77 213 232 environmentally extended multiregional input-output model (n=4),43 44 231 232 and the Bilan Carbone model (n=1).166 Tools used in the literature included carbon calculators (n=6),52 101 115 121 165 176 Carbon Trust recommendations (n=1),26 the Eyefficiency tool (n=1),89 the Pollard model (n=1),188 the Ringelmann smoke chart (n=1),157 and the US Environmental Protection Agency’s waste reduction model (n=1).144 Other studies (n=16) used publicly available datasets (eg, UK Department of Business, Energy, and Industrial Strategy conversion factor data; environmental impact data provided by the German Federal Environment Agency), or previously published literature to quantify GHG emissions in their facilities.74 83 94 99 110 113 123 126 129 148 161 162 163 168 178 202 Tools for measuring healthcare emissions from empirical studies Models are general method used to measure GHG emissions at a certain level, whereas tools were developed to measure emissions using one or more models. GHG=greenhouse gas; US EPA=United States Environmental Protection Agency. Some publications used several models.

From the thematic analysis, nine themes emerged across the included publications, which were then grouped into one of two categories: overarching strategies (table 5) or decarbonisation tactics (table 6). The most frequently discussed overarching strategy was the need for effective policies and governance surrounding healthcare sustainability (n=97) and the most common decarbonisation tactic was changing clinical and surgical practices (n=107). Papers discussing numerous themes or subthemes were included in several categories. Publications in the overarching strategies category, grouped into themes Overarching strategies definition: mechanisms for healthcare system improvement relating to climate change. GHG=greenhouse gas. Publications in the decarbonisation tactics category, grouped into themes Decarbonisation tactics definition: tactics for reducing greenhouse gas emissions within healthcare systems. GHG=greenhouse gas.

The need for policies and incentives to promote, guide, monitor, or evaluate changes at the country, state, and facility level was discussed in 97 publications6 7 11 19 23 25 42 43 44 45 46 47 48 49 50 51 55 56 57 58 59 61 63 64 65 67 68 69 70 71 73 76 79 88 89 95 96 103 104 105 109 111 112 114 115 117 120 123 124 125 127 128 130 133 136 138 142 143 151 152 154 159 162 166 168 170 171 173 179 180 184 188 191 192 193 200 201 203 205 206 207 208 209 210 212 213 216 217 218 219 220 221 224 231 232 233 234; 39.2% of the publications discussing this theme were empirical studies. The most common strategy focused on priority setting and leadership from national and international bodies (n=51), such as integrating sustainability into policy or setting long term sustainability goals across organisations.6 7 11 19 43 46 50 51 56 57 59 63 64 65 67 70 76 79 95 96 104 105 109 111 114 115 120 125 127 128 130 133 138 143 152 154 166 170 184 188 206 209 210 216 217 218 220 221 231 232 234 This was followed by publications (n=27) that suggested mandating evaluations, benchmarking, and reporting of the carbon footprint for healthcare organisations to strengthen the evidence base for future decision making.6 7 23 45 55 58 61 68 70 73 88 124 136 142 151 159 168 173 179 205 207 208 212 213 216 219 221 An equal number of publications (n=21 each) highlighted using financial policy and incentives for sustainable healthcare processes6 42 43 44 48 49 70 73 89 96 123 133 138 143 162 171 180 200 221 224 233 and the need for a multisectoral approach to mitigate the carbon footprint of healthcare,7 23 56 69 73 89 96 103 112 117 162 191 192 201 203 205 210 217 220 221 233 such as collaborations between large healthcare organisations. Fifteen publications recommended setting targeted emissions reductions.7 11 19 25 45 46 47 58 70 71 89 136 193 218 219

Organisational change to develop a future ready workforce was dealt with in 76 publications.24 25 27 46 48 49 50 57 58 63 65 68 69 70 71 73 75 77 79 80 81 83 86 91 93 99 102 103 105 110 112 114 116 127 130 133 135 136 137 138 142 143 150 151 152 154 165 166 171 172 174 178 179 180 181 182 185 187 191 192 195 196 199 202 205 206 207 210 212 216 220 221 228 233 234 235 Roughly 30.3% of the publications discussing this theme were empirical studies. Ongoing education and training within healthcare organisations and tertiary institutions was identified in 59 publications as a way of ensuring the workforce is aware of and equipped for sustainability challenges.24 25 48 49 50 57 63 65 68 69 73 75 77 79 81 83 86 91 99 102 103 110 112 114 116 127 130 133 135 137 138 142 143 150 151 152 165 166 171 172 174 178 179 180 185 187 192 195 196 202 205 206 207 210 212 220 228 233 235 Publications discussing organisational leadership focused on implementing multidisciplinary teams, “green champions,” and other organisational role models to manage sustainability at different levels of the healthcare system and empower employee decision making (n=26).27 46 58 63 70 71 77 80 93 105 127 133 135 136 152 154 165 181 182 185 191 196 199 216 221 234

The literature outlined several important roles for individuals and groups in reducing healthcare’s carbon footprint (n=74)7 19 28 43 48 49 50 51 53 56 57 58 59 61 63 64 65 66 67 69 71 73 81 85 86 88 89 90 91 96 98 102 103 107 108 112 114 116 117 127 130 133 134 135 137 139 142 143 151 160 162 168 171 177 180 181 183 184 192 195 196 210 212 215 216 218 219 220 221 226 229 232 233 236; 20.3% of the publications discussing this theme were empirical studies. Promoting change through advocacy, lobbying, and open support of sustainability initiatives was the focus of 45 publications,7 48 49 50 51 53 58 61 64 65 66 67 71 81 85 86 88 89 90 96 98 103 107 114 116 117 127 133 134 135 139 142 151 171 180 181 183 184 192 195 196 216 218 232 233 including the need for community involvement and education when enhancing the sustainability of healthcare practices (n=21).43 53 56 81 90 103 112 130 133 151 160 168 192 210 212 218 221 229 232 233 236 Several publications emphasised individual responsibility as a key factor in making change (n=15), particularly through engaging with low carbon healthcare and living an active lifestyle.57 59 63 73 81 89 91 96 103 143 160 162 192 220 233 Additionally, 15 articles identified benefits of reducing GHGs in the health system, which included financial savings and reducing disease burden.19 28 50 69 96 102 107 108 112 137 177 212 215 219 226

The impetus to develop, use, and standardise tools for measuring and monitoring GHG emissions was a prominent theme (n=70 publications).6 7 11 19 26 43 44 45 47 48 51 58 59 61 62 66 68 69 71 73 75 77 79 84 88 96 103 104 105 107 109 112 114 124 125 137 139 142 146 148 149 154 163 164 171 177 188 192 193 194 200 205 207 208 209 211 212 216 217 218 219 221 222 224 225 227 228 230 231 234 Nearly 37.1% of the publications discussing this theme were empirical studies. Evaluative tools, along with existing models such as LCA, can be used to improve decision making on procurement and services, and was a feature of 43 publications.6 43 47 58 59 62 66 68 73 75 77 79 84 88 96 104 105 107 109 112 124 137 139 142 146 149 154 164 192 200 205 208 211 212 216 217 218 224 225 227 230 231 234 Developing tools to measure GHG emissions and monitor the movement of materials was discussed in 25 publications.7 11 19 26 43 44 69 103 124 125 146 171 177 188 193 194 207 209 211 219 221 222 225 227 228 Several publications (n=17) emphasised the need for standardised platforms for reporting and comparing the sustainability of products or processes to enable healthcare organisations to make informed decisions about their current practices.7 26 45 47 48 51 61 71 107 114 148 154 163 177 207 211 219

Changing clinical and surgical practices as a solution for reducing healthcare’s carbon footprint was advocated in 107 publications6 7 11 23 24 25 27 28 42 43 48 50 51 52 54 55 57 61 63 66 68 69 71 73 74 75 77 78 79 81 82 83 84 85 86 87 90 91 93 94 96 97 98 99 100 101 102 103 106 107 108 109 112 113 114 116 120 126 128 129 130 133 135 138 139 142 143 148 149 151 152 159 161 163 165 166 167 168 169 170 171 173 174 175 177 178 179 183 185 186 189 190 191 192 196 205 212 214 217 224 227 229 230 232 233 234 236; 37.4% of the publications discussing this theme were empirical studies. This solution included replacing high GHG practices with lower GHG options (n=80),11 23 27 28 43 48 54 57 61 63 68 71 73 74 75 77 78 79 81 82 83 84 85 86 87 90 91 93 94 96 97 98 100 102 103 106 107 112 113 114 120 126 128 129 133 135 138 139 148 149 152 159 161 163 165 166 167 168 170 171 173 174 177 178 179 183 189 190 192 196 214 217 224 227 229 230 232 233 234 236 such as choosing anaesthetic gas types and systems with lower carbon footprints.54 71 73 81 83 85 86 96 100 229 This advocation was also seen in primary care settings (n=6).63 130 133 135 138 139 As a way of minimising healthcare usage, and thus reducing healthcare’s carbon footprint, 41 publications reinforced the need to assess clinical practices for low value care.6 7 24 28 42 51 52 55 66 68 69 75 77 79 93 97 99 101 109 116 130 142 149 151 152 169 174 175 177 179 185 186 190 191 192 205 212 214 224 229 233 This included identifying and reducing unnecessary processes or procedures, minimising drug overprescription, or encouraging a preventative care approach to reduce the need for health services. Reducing water usage during procedures, disinfection and sterilisations, laundry, recycling water, and practising water efficiency were also suggested in six publications.23 25 50 108 143 189

Dealing with waste was a focus of 83 publications11 25 43 47 48 49 50 51 54 55 57 60 61 63 67 72 73 77 78 80 81 82 84 85 86 88 89 91 93 95 96 97 98 100 101 102 104 105 107 110 112 114 116 135 138 142 143 144 149 150 151 152 153 154 155 157 159 160 169 171 177 183 189 190 191 192 198 199 206 210 211 217 218 219 222 223 224 228 229 232 233 234 236; 32.5% of the publications discussing this theme were empirical studies. This theme included waste minimisation methods (n=71),11 25 43 47 48 49 50 51 54 55 57 60 61 63 67 72 73 77 78 80 82 84 85 88 91 95 96 97 98 100 101 102 104 105 107 110 112 116 135 138 142 143 144 149 151 152 154 155 159 160 169 171 177 183 189 190 191 192 198 206 211 217 218 219 222 224 228 229 232 233 234 such as reducing, reusing, and recycling medical equipment, and using reusable alternatives over disposable items. Several publications highlighted the need for effective segregation and disposal of waste (n=29),50 57 73 77 80 81 82 86 88 89 93 95 107 114 143 144 150 151 153 157 160 177 183 199 206 210 223 232 236 including choosing disposal methods such as incineration that help minimise carbon emissions.

Patient or clinical travel and transportation was emphasised as an important and addressable source of carbon emissions in 70 publications.6 7 24 43 47 48 51 55 59 61 63 69 71 73 74 79 84 85 86 93 94 95 96 105 109 114 117 119 120 121 122 124 125 126 127 128 131 132 135 137 140 142 148 152 156 161 163 165 166 171 172 174 176 188 190 191 192 193 195 196 197 201 202 217 224 226 228 229 232 233 Some 42.9% of the publications discussing this theme were empirical studies. Using carbon efficient models of care was seen as a method to reduce emissions (n=41), for example, telemedicine or home based treatment options.6 24 43 47 48 51 59 63 71 73 74 79 84 94 95 96 105 109 119 121 122 124 125 126 128 132 135 148 161 163 165 171 172 176 188 191 195 196 217 228 229 A further 25 publications discussed alternative forms of transportation (eg, car sharing, buses, trains, and active travel such as cycling) for patients and clinicians.7 47 55 69 79 105 114 121 131 137 140 142 152 161 166 174 176 190 192 197 202 224 226 232 233 Streamlining medical services, such as emergency service coordination, redesigning schedules for clinicians to enhance ride share and closing sites with lower use, was discussed in 14 publications.61 79 86 93 127 131 132 148 156 161 166 176 188 193 Several papers (n=13) also highlighted reducing professionals’ travel (eg, clinicians, researchers, industry partners) for conferences and education as a decarbonisation method.43 47 51 63 85 117 120 171 191 195 201 224 228

Sixty three papers recommended improvements to healthcare infrastructure26 27 43 47 50 55 57 58 59 61 63 69 72 73 80 81 84 88 92 93 96 97 98 108 109 112 114 117 118 135 141 142 143 145 146 147 151 152 160 161 171 174 175 184 192 193 194 195 202 206 207 210 211 212 218 221 224 226 228 229 232 234 235; 33.3% of the publications discussing this theme were empirical studies. Improving the energy efficiency of healthcare facilities such as hospitals was a feature of 40 publications.47 50 55 57 61 63 69 72 73 80 81 92 93 97 98 109 112 135 141 142 143 146 147 152 160 171 192 193 194 207 210 211 212 218 221 224 229 232 234 235 For example, consideration of design features such as insulation and passive shading options can help reduce reliance on electrical heating and cooling, and therefore reduce GHG emissions. Thirty four publications advocated for using energy conservation measures—such as turning off appliances when not in use—to help minimise carbon emissions at a facility level.26 27 43 57 58 59 61 63 73 84 88 96 97 108 114 117 118 135 143 145 151 152 161 174 175 184 194 195 202 206 221 226 228 229

Forty eight papers proposed decarbonising the supply chains as a way of reducing GHG emissions.7 25 26 42 43 44 47 50 54 55 56 59 65 73 84 85 87 89 98 104 105 110 112 114 127 136 139 142 143 151 152 158 171 175 183 193 194 197 204 210 212 215 218 224 229 232 234 235 Roughly 39.6% of the publications discussing this theme were empirical studies. Numerous publications (n=43) focused on ways to reduce the carbon footprint by deploying sustainable production and procurement mechanisms within supply chains, such as using sustainable or local sources of food supply, or using supply chains with low emissions.7 25 42 43 44 47 50 54 55 56 59 65 73 84 85 98 104 105 110 112 114 127 136 139 142 143 151 152 158 171 175 183 193 197 210 212 215 218 224 229 232 234 235 Decarbonising the sources of energy for healthcare by using renewable sources rather than fossil fuel sources and monitoring energy grid consumption was noted in 10 publications.7 26 50 87 89 158 194 204 212 232

From our findings we developed a rich picture of the strategies and tactics for reducing the emissions produced by healthcare systems (fig 5). This schematic figure is not an exhaustive example, but rather illustrates how these strategies and tactics to reduce emissions produced by healthcare systems are interconnected and affect flow within and outside of the healthcare system. Authorisation to proceed starts at the top, with effective policies, governance, and high level leadership. Measurement of GHGs through recognised and increasingly sophisticated tools is necessary, and now more pronounced, as is the use of tools and frameworks to report on progress, and make decisions about alternative, greener options. Tools and frameworks for use at micro, meso, and macro levels are now more widely available. Several options for individuals and groups to orchestrate change and improvement, typically targeted at organisations such as hospitals, care facilities for older people, and general practices, have been generated. Strategies and tactics for reducing healthcare system greenhouse gas (GHG) emissions according to healthcare system level: micro (eg, frontline clinician, including healthcare delivery at a clinic, department, whole hospital, or facility), meso (regional or network level, eg, health district, hospital network), macro (whole healthcare system, including national or global systems)

se gas (GHG) emissions according to healthcare system level: micro (eg, frontline clinician, including healthcare delivery at a clinic, department, whole hospital, or facility), meso (regional or network level, eg, health district, hospital network), macro (whole healthcare system, including national or global systems) On decarbonisation specifically, attention was focused on modifying medical, surgical, and other clinical practices, reducing physical waste, and minimising transportation costs or eliminating travel altogether through new clinical models such as virtual care, telehealth, or telemedicine.24 59 63 81 94 97 120 121 126 165 172 196 When enacting decarbonisation tactics that affect patient care, it is vital that lower carbon alternatives provide equal or improved patient outcomes compared with current practices and be acceptable to and supported by patients.105 Other specific activities for reducing carbon emissions and greening healthcare, directly or in those services indirectly controlled by healthcare systems, include building new or remediating existing healthcare infrastructure and reducing the carbon footprint along healthcare supply chains. Given the large contribution of supply chain emissions and the high potential for reducing emissions,238 it is surprising that supply chain decarbonisation approaches, including those related to food supply, were less frequently discussed than others. Another surprising lack of attention was discussion at the intersection of universal health coverage and healthcare system decarbonisation because reducing the need for care through primary prevention would have a direct impact on carbon emissions by lowering demand.49 140

y, were less frequently discussed than others. Another surprising lack of attention was discussion at the intersection of universal health coverage and healthcare system decarbonisation because reducing the need for care through primary prevention would have a direct impact on carbon emissions by lowering demand.49 140 Overall, a framework of useful activities to substantially reduce the carbon budget of healthcare is now available, and represented in figure 5. Although this framework provides a platform to assess these activities, determining which elements would be most effective, and under what conditions, will partly depend on the characteristics of the individual healthcare system.96 Barriers to implementing sustainable practice into healthcare systems might also exist, including patients accepting changes, cost and funding mechanisms, attitudes towards change, and workforce capacity in an already overburdened system. As these decarbonisation approaches are put into practice, any barriers and potential enablers should be explored further.

tice into healthcare systems might also exist, including patients accepting changes, cost and funding mechanisms, attitudes towards change, and workforce capacity in an already overburdened system. As these decarbonisation approaches are put into practice, any barriers and potential enablers should be explored further. The included literature was mainly from high income countries. However, we found some examples of lower-middle income country healthcare systems and organisations taking the lead in advancing the overarching strategies identified, such as developing tools to measure emissions (eg, the Aga Khan Health Services (AKHS) freely available tool),44 and the decarbonisation tactics, such as reducing physical waste and emissions from waste disposal (eg, Snigdha and colleagues)158 and improving the environmental sustainability of clinical practices.111 156 199 Some of the decarbonisation tactics might be more challenging to implement in lower-middle income country healthcare systems, such as strengthening infrastructure.96

l waste and emissions from waste disposal (eg, Snigdha and colleagues)158 and improving the environmental sustainability of clinical practices.111 156 199 Some of the decarbonisation tactics might be more challenging to implement in lower-middle income country healthcare systems, such as strengthening infrastructure.96 Regardless of the setting, having an overarching set of mechanisms and approaches might be useful and highlights the need for a multipronged approach, including how we measure emissions and progress, especially given the range of measuring tools that have emerged. The actions include effective governance and supportive policies, appropriate financing, and strengthening infrastructure and service delivery.20 Collaborative, international, multisectoral leadership is needed to learn from progress elsewhere and to localise and prioritise strategies and support direct actions. Achieving a step change reduction in emissions is a socially and ethically responsible imperative. In principle, it is feasible and beneficial to roll out these strategies and tactics at scale to achieve systemic change—this is central to the mission of healthcare providers: to do no or less harm, to alleviate suffering, and to improve the health status of the population. Healthcare can set an example for other industries and sectors as responsible environmental stewards. This review suggests that healthcare systems and professionals have recognised their duty and are embracing the necessary changes, but there is a long way to go.

ing, and to improve the health status of the population. Healthcare can set an example for other industries and sectors as responsible environmental stewards. This review suggests that healthcare systems and professionals have recognised their duty and are embracing the necessary changes, but there is a long way to go. The comprehensive analysis of 18 years of studies, frameworks, and tools that assess and quantify the carbon footprint of healthcare is a key strength of the paper, as is the development of a new framework. Previous reviews did not appear to focus sufficiently on mitigation strategies or use the systematic review methodology.

prehensive analysis of 18 years of studies, frameworks, and tools that assess and quantify the carbon footprint of healthcare is a key strength of the paper, as is the development of a new framework. Previous reviews did not appear to focus sufficiently on mitigation strategies or use the systematic review methodology. Our review was limited to papers and authoritative reports written in English, and so some papers might have been missed. However, eight databases were searched, therefore the likelihood of new themes being identified is low. Most of the included literature discussed healthcare systems in high income countries, which is a well known bias. This bias can create challenges when extrapolating identified strategies to low-middle income countries. However, the included papers revealed that healthcare systems in low-middle income countries are undertaking similar strategies to high income countries. A review specifically focused on healthcare systems in low-middle income countries, and the ethical implications of climate change and decarbonisation tactics, is warranted. Inductive approaches, as in this study, allow flexibility and deeper understanding of the data, but introduce issues of inter-rater reliability and bias. Our review used 19 investigators for screening, extraction, synthesis, and interpretation to minimise bias.

climate change and decarbonisation tactics, is warranted. Inductive approaches, as in this study, allow flexibility and deeper understanding of the data, but introduce issues of inter-rater reliability and bias. Our review used 19 investigators for screening, extraction, synthesis, and interpretation to minimise bias. We reviewed the literature to generate strategies and tactics for reducing the impact of healthcare systems on climate change. Implementing these strategies should enable substantial progress towards reducing healthcare’s carbon footprint and support a greener health sector powered by renewable sources. However, healthcare systems would need to adapt these approaches to their context and needs to maximise their effects. Healthcare can lead the way in shifting to net zero by 2050, and by doing so we can reduce the burden of patients who would otherwise need more care as a consequence of a warming world. The carbon footprint of healthcare systems has been estimated at about 4.4% of global emissions, but comprehensive reviews investigating mitigation are lacking One review took a global approach when examining the environmental impact of healthcare systems; however, this study was not peer reviewed and data were limited to one year Another study discussed the sustainability of healthcare at a global level, however it was not conducted as a systematic review, and the methods used to evaluate and collate data were unclear

One review took a global approach when examining the environmental impact of healthcare systems; however, this study was not peer reviewed and data were limited to one year Another study discussed the sustainability of healthcare at a global level, however it was not conducted as a systematic review, and the methods used to evaluate and collate data were unclear This review includes 18 years of studies, frameworks, and tools assessing the carbon footprint of healthcare systems, and the steps taken to measure and reduce these impacts Overarching strategies and specific tactics, models, and tools were identified that could be used to decarbonise healthcare systems, aiming to reach net zero emissions by 2050

Overall, a framework of useful activities to substantially reduce the carbon budget of healthcare is now available, and represented in figure 5. Although this framework provides a platform to assess these activities, determining which elements would be most effective, and under what conditions, will partly depend on the characteristics of the individual healthcare system.96 Barriers to implementing sustainable practice into healthcare systems might also exist, including patients accepting changes, cost and funding mechanisms, attitudes towards change, and workforce capacity in an already overburdened system. As these decarbonisation approaches are put into practice, any barriers and potential enablers should be explored further. The included literature was mainly from high income countries. However, we found some examples of lower-middle income country healthcare systems and organisations taking the lead in advancing the overarching strategies identified, such as developing tools to measure emissions (eg, the Aga Khan Health Services (AKHS) freely available tool),44 and the decarbonisation tactics, such as reducing physical waste and emissions from waste disposal (eg, Snigdha and colleagues)158 and improving the environmental sustainability of clinical practices.111 156 199 Some of the decarbonisation tactics might be more challenging to implement in lower-middle income country healthcare systems, such as strengthening infrastructure.96

The comprehensive analysis of 18 years of studies, frameworks, and tools that assess and quantify the carbon footprint of healthcare is a key strength of the paper, as is the development of a new framework. Previous reviews did not appear to focus sufficiently on mitigation strategies or use the systematic review methodology. Our review was limited to papers and authoritative reports written in English, and so some papers might have been missed. However, eight databases were searched, therefore the likelihood of new themes being identified is low. Most of the included literature discussed healthcare systems in high income countries, which is a well known bias. This bias can create challenges when extrapolating identified strategies to low-middle income countries. However, the included papers revealed that healthcare systems in low-middle income countries are undertaking similar strategies to high income countries. A review specifically focused on healthcare systems in low-middle income countries, and the ethical implications of climate change and decarbonisation tactics, is warranted. Inductive approaches, as in this study, allow flexibility and deeper understanding of the data, but introduce issues of inter-rater reliability and bias. Our review used 19 investigators for screening, extraction, synthesis, and interpretation to minimise bias.

We reviewed the literature to generate strategies and tactics for reducing the impact of healthcare systems on climate change. Implementing these strategies should enable substantial progress towards reducing healthcare’s carbon footprint and support a greener health sector powered by renewable sources. However, healthcare systems would need to adapt these approaches to their context and needs to maximise their effects. Healthcare can lead the way in shifting to net zero by 2050, and by doing so we can reduce the burden of patients who would otherwise need more care as a consequence of a warming world. The carbon footprint of healthcare systems has been estimated at about 4.4% of global emissions, but comprehensive reviews investigating mitigation are lacking One review took a global approach when examining the environmental impact of healthcare systems; however, this study was not peer reviewed and data were limited to one year Another study discussed the sustainability of healthcare at a global level, however it was not conducted as a systematic review, and the methods used to evaluate and collate data were unclear This review includes 18 years of studies, frameworks, and tools assessing the carbon footprint of healthcare systems, and the steps taken to measure and reduce these impacts Overarching strategies and specific tactics, models, and tools were identified that could be used to decarbonise healthcare systems, aiming to reach net zero emissions by 2050

The carbon footprint of healthcare systems has been estimated at about 4.4% of global emissions, but comprehensive reviews investigating mitigation are lacking One review took a global approach when examining the environmental impact of healthcare systems; however, this study was not peer reviewed and data were limited to one year Another study discussed the sustainability of healthcare at a global level, however it was not conducted as a systematic review, and the methods used to evaluate and collate data were unclear

This review includes 18 years of studies, frameworks, and tools assessing the carbon footprint of healthcare systems, and the steps taken to measure and reduce these impacts Overarching strategies and specific tactics, models, and tools were identified that could be used to decarbonise healthcare systems, aiming to reach net zero emissions by 2050