Incorporating carbon into health care: adding carbon emissions to health technology assessments
Introduction
These and other extreme weather events have focused attention on the effects of climate change on health.
Converted to disability adjusted life years (DALYs), these emissions may cause up to 3 060 000 DALYs reduction in human health annually, due to increases in undernutrition, malaria, water and vector borne diseases, and heat stress.
Further, converted into dollar terms using the global average GDP per capita, these DALYs result in an economic cost of between US$ 32·7 and 98·2 billion.
The methods and evidence base for measuring the carbon emissions of healthcare and including them in clinical decision making to achieve this is, however, lacking.
Methods of HTA include health economic evaluations and comparative effectiveness studies, and although these economic assessments are now routine and sophisticated, presently HTA does not include environmental impacts such as carbon emissions. HTAs can be undertaken as part of an internal process by individual public or private payers, and they form a vital component of clinical and policy guidance used by leading agencies such as the US Preventive Services Taskforce and the National Institute of Health and Care Excellence in the UK. The outcomes of these HTAs, including reports to regulatory bodies such as the US Food and Drug Administration, determine the scope and nature of clinical practice, guiding the day-to-day clinical decisions of physicians in hospitals and in primary care settings. In addition to determining the costs to health-care payers, they also lock in the carbon footprint of health care. Crucially, these carbon emissions influence not only current global health outcomes, but they also irreversibly influence those of future generations for centuries to millennia. To be environmentally and economically sustainable, health-care decision makers and clinicians must now take account of carbon emissions. Yet, to date, little work has been done about how carbon emissions could be usefully integrated into the standard methods and processes of HTA so that this crucial information can be considered in health-care decision making now and in the future.
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This case is even stronger now in view of recent events. We therefore seek to build on previous research by resolving two main challenges. The first is that little quantification of the carbon emissions of medical devices, procedures, or pharmaceuticals associated with health care has been completed, meaning studies will be required to fill these gaps in knowledge. Second, there have been no published studies on how carbon costs should best be incorporated in HTAs.
This manuscript brings together key methods of environmental science and health technology assessment, in order to outline how carbon emissions from health care can be best quantified, and to find ways in which carbon emissions can then be integrated into HTA as a decision criteria or in economic evaluation, recognising that HTAs are done in several ways by different jurisdictions.
Measuring carbon emissions
The ISO 14040-44 standards in turn, form the methodological foundation for major product carbon footprinting standards and protocols.
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The basis of analysis within LCA is the functional unit, which clearly defines the functions of a product or service rather than its physical characteristics. An example of a functional unit is all anaesthesia for a total knee replacement in a hospital in St Louis, Missouri. Several LCAs have been done in health care, including calculating national carbon emissions from healthcare, comparisons of single-use and reusable items, and the impacts of patient,surgical and anaesthetic care, pathology and diagnostic imaging, pharmaceuticals, and hospitals.
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Some carbon hotspots have been identified, including anaesthesia and metered-dose inhalers.
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Figure 1Stages of life cycle assessment
Life cycle assessment methods
Using input-output tables, carbon emissions can be calculated on a per-dollar basis of goods or services purchased from a given sector (kg CO2e/US$). As an example, using the USA Carnegie Mellon EIO model, the carbon emissions from purchasing $100 (2022) of goods and services from the surgical and medical instrument manufacturing sector is approximately 18 kg CO2e. Importantly, this figure is the average emissions intensity of everything purchased from the whole sector. Given the large number of heterogenous goods and services provided from all of surgical and medical instrument manufacturing, this linear relationship between price and emissions does not hold true for individual items.
Although EIO has been used extensively for calculating carbon emissions of the health-care sector at a regional, national, or international level, the absence of relationship between price and emissions means that its use is not recommended to quantify emissions of specific health-care items or services.
Figure 2Process for turning a stainless steel tube into an unsharpened hypodermic needle
There are two types of P-LCA, attributional and consequential. Attributional P-LCA estimates what proportion of the total carbon footprint of a health-care service can be attributed to a specific clinical activity, whereas consequential P-LCA only estimates the change in emissions that occur by performing an additional clinical activity (the marginal impact). As an example, hospital X-ray machines run 24 h a day and 7 days a week so they can be used in emergencies. An attributional analysis would include this standby power when the machine is on, but is not being used for imaging. By comparison, the consequence of ordering an X-ray is not that the X-ray machine is turned on, it is operating regardless of whether an X-ray is ordered or not. The consequence of ordering an image, therefore, is the small change in power when an image is taken. These two approaches complement each other by providing information on the overall impact of a clinical activity in addition to the impact of a change in clinical behaviour. We therefore recommend both attributional and consequential LCAs be done and reported.
P-LCA enables individual interventions to be modelled at a fine level of detail, thereby identifying carbon hotspots that can be targeted for mitigation. Importantly, and similarly to health economic evaluation, P-LCA makes comparison possible between a health-care technology or intervention and an alternative (eg, standard surgery versus robotic surgery). This is essential to enable informed choices to be made between two clinical options on the basis of individual health outcomes, economic costs, and environmental impact.
Converting LCA results to carbon reference units
Using gaseous anaesthetics as an example, 1 kg desflurane is equivalent to 1790 kg CO2e, whereas 1 kg sevoflurane is equivalent to 216 kg CO2e.
An LCA does these calculations for greenhouse gas emissions from all stages of a life cycle.
Health technology assessments and carbon emissions
Next we explore how carbon emissions could be included in HTA. Carbon emissions are examples of externalities. An externality is a cost or benefit from the activity of a person or organisation that is borne by an unrelated third party, and, as such, the cost or benefit of the externality is excluded from the market transaction. For example, the market price of fossil fuels does not include the cost of morbidity and mortality resulting from forest fires caused by climate change, even though combustion of fossil fuels is the chief cause of rising atmospheric carbon dioxide concentration driving climate change.
Linking LCA to health technology assessments
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Figure 3Stages to integrate LCA with HTA
CBA=cost-benefit analysis. CEA=cost-effectiveness analysis. HTA=health technology assessment. LCA=life cycle assessment. MCDA=Multi Decision Criteria Analysis.
we recommend that the environmental impacts from the whole life cycle (cradle-to-grave) of each LCA should be calculated as a single value (eg, kg CO2e). This temporal aggregation of emissions is the way LCAs are typically performed.
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an individual LCA will need to be done for each year of the economic analysis, so that monetised emissions can be discounted alongside other economic costs and benefits. This will require that anticipated changes in technology, such an expected increased use of renewable energy, be temporally integrated into the LCA of each year. Additionally, the LCA will need to be dynamic, with environmental emissions assigned to specific years.
Fortuitously in health care, the life cycle of many items (from manufacture through use to disposal) is typically less than 5 years, and there are few long-term emissions caused by disposal because most medical equipment is inert (metal and plastic), with biodegradable items such as cotton gauzes making up only a small proportion by mass of items used clinically.
This makes dynamic modelling easier to achieve compared with other sectors such as buildings.
Impacts in kilograms of CO2e calculated from each LCA can then be included as an additional cost in decision-analytical or Markov models, to be incorporated alongside other economic costs and health outcomes. This process has the additional important benefit of identifying hotspots associated with interventions, enabling potential mitigation measures, such as quality-improvement projects or behaviour-change interventions, to be undertaken.
Carbon emissions as a decision modifier
Carbon emissions as part of MCDA
Monetising carbon emissions
the price of carbon offsetting credits from schemes such as forestry or soil sequestration or methane capture; and marginal abatement costs, which are calculated on the basis of engineering costs to reduce emissions to reach a given target.
By comparison, in Australia there is no official carbon market, with the unofficial carbon price being the cost of carbon offsets.
Different jurisdictions, therefore, have different carbon prices.
Discussion
Health services globally are starting to commit to net-zero targets for carbon emissions, although with little detail on how this will be achieved. We propose that an important method to achieve carbon neutrality will be the inclusion of carbon emissions in health technology assessments. The main challenge is that, unlike other major sectors of the economy in which extensive LCA studies have quantified emissions, to date there have been very few studies undertaken in health care.
Further, specific sectors that are arguably more complex than health care, such as agriculture that has a high degree of variability caused by local conditions and farming practices, have developed sector-specific databases.
Given that there is no technical difference in undertaking an LCA using ISO 14040 in health care compared with other sectors, a healthcare-specific database containing common items such as syringes, procedures such as MRI, or processes such as sterilisation, to enable expeditious and accurate modelling can be developed.
It is paramount, furthermore, that access to the database be free or affordable, at both the aggregate level (eg, a 10 mL syringe produces approximately 30 g CO2e) so that it could be used by clinicians, and at a database level so that LCA practitioners could perform detailed modelling. Free or low-cost access is essential so that health services with scarce resources are not perversely incentivised to avoid inclusion of carbon quantification in their decision-making processes, or repeat what others have already done, potentially at lower levels of accuracy or quality. Similar to current public sector investment in the regulation of medicines and in health technology assessments, this approach will require substantial public sector financial support or subsidies (eg, through a licence-fee system).
would be needed, with verification possible by an independent third-party agency using a uniform, evidence-based, non-proprietary framework and methods.
Once this initial start-up work has been done however, it will be relatively quick and inexpensive to quantify carbon emissions as is now routinely done in other sectors. The process should, with time, become as routine as quantifying costs is currently.
Once quantified, the second challenge is how to best include carbon emissions in health technology assessments, as decision makers have not yet had to consider environmental externalities when choosing between technologies. As we move into a carbon-constrained world, environmental impacts will become a major consideration for decision makers. Including carbon emissions in HTA will ensure their decisions will result in genuinely sustainable health care for present and future generations. This work is also vital for health equity because, without it, the greatest health impacts of climate chance will disproportionately fall on vulnerable populations and low-income countries.
The choice of whether to use carbon emissions as a decision modifier, as in an MCDA, or as a monetised cost in a CEA or CBA will probably be dependent on the funding organisation, jurisdiction, or decision makers and may be guided by purely technical considerations. The benefit of having several options is that they can be incorporated into standard health-technology assessment agency processes, even where countries differ markedly in their need for comparative effectiveness evidence. As such, we have avoided being overly prescriptive, and have chosen to offer suggestions that are flexible enough to be applicable in a range of HTA approaches and methods. We offer these suggestions as a step forward and anticipate further development by HTA practitioners within their local contexts, so that they can best establish how carbon emissions would influence their decision making.
All of these emissions can be quantified by LCA, and therefore could, in the longer term, be included in the integration between LCA and HTA. We feel, however, that carbon emissions should be the primary immediate focus, given that countries have to rapidly reduce their carbon emissions in line with the Paris Agreement, which seeks to limit global warming to within 1·5–2·0°C above preindustrial levels.
The challenge of incorporating carbon emissions into health technology assessments is considerable, but not unsurmountable. We hope this work will lay the foundation to meet this important challenge.
SM did the project administration, methods development, and wrote the original draft. RLM developed the health-technology assessment methods. RLM and AB both did the critical review of the methods. All authors reviewed and edited the manuscript and agreed to submit the manuscript for publication. All authors had final responsibility for the decision to submit for publication.
