Mandatory Reporting of Emissions to Achieve Net-Zero Health Care

Currently, HCO reporting of greenhouse-gas emissions in the United States (outside of federal systems) is voluntary. Health care systems have no universally accepted, standardized greenhouse-gas measures, reporting, or management systems, although reporting frameworks outside of health care have long existed. Ideally, HCO metrics should make use of existing international measurement standards within the framework of the Greenhouse Gas Protocol (GHG Protocol), which delineates how different sources of emissions must be accounted for.15,23 The GHG Protocol is used for virtually all international carbon-reporting frameworks, across industries.

In health care quality efforts, measurement is used for both accountability and improvement purposes. The same holds true for health care decarbonization, which can appropriately be considered an additional dimension of quality of care.16, 24, 25 Because health care–induced pollutants cause harm to patients, the health care workforce, and society more broadly, decarbonizing efforts should be viewed explicitly as a component of quality improvement. Even though these harms are indirect and external to an organization, they can and should be classified with other, more direct forms of injury to patients. Metrics can enable performance reporting and transparency for accountability purposes for both HCOs and the entire US health system. Likewise, measurement can inform local HCO improvement efforts, help to evaluate and facilitate sharing of decarbonization initiatives, and identify best practices.

Recommended Metrics

GHG Protocol Scopes for US Health Care.

The Greenhouse Gas Protocol (GHG Protocol) delineates how different sources of emissions must be accounted for. Emissions to be measured and reported include greenhouse gases emitted directly from health care facilities (scope 1), those emitted indirectly through purchased energy (scope 2), and all other indirect emissions (scope 3). Scope 3 covers 15 categories.

Calculating total greenhouse-gas emissions is essential to guide strategic management. Such an effort requires accounting for greenhouse gases emitted directly from health care facilities, such as those from on-site boilers and medical gases (referred to as scope 1 under the GHG Protocol), those emitted indirectly through purchased energy (scope 2), and all other indirect emissions (scope 3). Scope 3 covers 15 categories, including emissions from purchased goods and services, employee commuting, and waste management (Figure 1, Several HCOs, including the Veterans Affairs health system, already measure scopes 1 and 2, but accounting of emissions from scope 3 is still evolving. Each scope 3 category has its own measurement guidance published within the GHG Protocol standards; The recommended approach depends on the data available. For example, for purchased goods and services, most studies to date have relied on expenditure-based modeling, which provides national mean carbon intensities for each category of purchase but not for specific products themselves.4,5 As manufacturers and researchers publish more product-level carbon-footprint data, it will be possible to perform accounting that is more detailed, actionable, and HCO-specific than is currently possible. Few organizations in any sector currently account for all scope 3 categories; most report only on those that are most relevant or convenient. However, because approximately 80% of US health care emissions stem from scope 3, measuring relevant categories that occur upstream or downstream from health care delivery will be critical for guiding decarbonization efforts.4

On the basis of existing literature and experience, as well as input from National Academy of Medicine Climate Collaborative member organizations representing private and public health entities (see the Supplementary Appendix, available with the full text of this article at NEJM.org), we recommend HCO greenhouse absolute-gas emissions as the best single measure to implement first.4,18,26 We recognize that reporting of some scope 3 categories may need to be phased in over time, given the underdeveloped state of manufacturer data and HCO data-collection infrastructure for certain categories and the complexity of the health care supply chain as compared with sectors that have relatively fewer and simpler inputs (eg, steel production). Table 1 shows additional priority measures.

Mandatory reporting of emissions is only an enabling first step in implementing decarbonisation. Additional health care–specific metrics are needed to define and set benchmarks of progress and to serve as key decarbonization performance indicators. Normalization factors that reflect clinical activity must also be considered. At the highest level, this can include factors such as occupied bed-days for a hospital and patient encounters for outpatient clinics or specific types of clinical services provided.26 Combining these measures with existing measures of health system performance (eg, quality and efficiency of care, costs, equity, and care outcomes) can help to ensure that decarbonization outcomes are patient-centered.16 Some structural indicators are also important to evaluate, such as the adoption of a climate action plan by HCOs; the appointment of executive leadership responsible for climate change accounting, mitigation, and adaptation performance; and HCO governance that includes board-level oversight, reporting, and stewardship accountability.

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