The results of the time series revealed successful efforts to mitigate the CF by the NHS in England and Scotland (figure 4). In the nearly three decades from 1990 to 2019, the English NHS reduced its CF by roughly 25%. The four remaining countries (Japan, Canada, USA and Australia) examined in the studies considered here and the global trend showed increased CF due to healthcare (figure 4). The annual increase in the CF ranged from 0.7% (USA, 2010–2018) to 3.8% (Japan, 2011–2015) over the observed period, with the CFs of Canada (1.9%, 2009–2015), USA (2.8%, 2011–2015) and Australia (2.9%, 2013–2015) in between these extremes. The global trend showed an increase in the CF of 2.7% per year from 2000 to 2015.

Emission trends over time. CF, carbon footprint.

The emission sources were mainly reported using the scope system from the GHG protocol or the categories of expenditure, that is, the categories of final demand. The largest dataset that used the categories of final demand was provided by Pichler et al,20 who applied this to 36 countries and reported the average values. Medical retail (ie, provider of healthcare products without medical services, eg, pharmacies), hospitals and ambulatory healthcare services constituted 80% of the CF of healthcare, with medical retail contributing 33.1%, hospitals 28.6% and ambulatory healthcare services 18%. They also made a major contribution to the CF in Japan (hospitals, 25.1%; ambulatory services, 22.7%), USA in 2013 (hospital care, 36%; physician and clinical services, 12%)11 and in 2018 (hospital care, 34.9%; physician and clinical services, 12.6%; ambulatory medical services, 4.8%),13 Australia (public hospitals, 34.4%; private hospitals, 10.2%; ambulatory medical services, 15%),16 China (public hospitals, 47%; private hospitals, 4%)15 and Austria (hospitals, 32%; ambulatory services, 18%).17 Other important categories of emissions were construction and pharmaceutical products, at around 10%,11 16 20 with a higher share in China (pharmaceuticals, 18%; construction, 15%).15

An alternative approach involved categorising emissions into direct emissions, indirect emissions through electricity production, and other indirect emissions. This division along these lines could also align with the three GHG protocol scopes.

By averaging data from 43 countries, HCWH reported a distribution of 17% for scope 1 emissions, 12% for scope 2 emissions and 71% for scope 3 emissions.21 These findings, particularly the significance of scope 3 emissions, are corroborated by evidence from single-country studies.8 11 12 14 24 The scope 3 emissions were further divided into those due to travel (patient and visitor travel, and staff commutes), production of pharmaceuticals, and medical instruments and equipment, which accounted for the largest share of scope 3 emissions.

Scotland’s scope 3 travel emissions in 2004 were 18% while those of England accounted for 13% in 2015 and 9.6% in 2018.9 The share of emissions owing to pharmaceutical production ranged from 11% to 18%, and that owing to medical instruments and equipment accounted for 7%–10% of the total CF.13 14 24

The ratio of emissions by the healthcare sector to the total CF in studies focused on a single country ranged from 2.7% in China in 201215 to 9.8% in the USA in 2013.11 The three cross-national studies considered here estimated that healthcare had contributed 5.5%20 on average to the national CF in 2014 and 4.4% in 2015.22