Climate Change, Carbon Dioxide Emissions, and Medical Imaging Contribution

Abstract

Human activities have raised the atmosphere’s carbon dioxide (CO2) content by 50% in less than 200 years and by 10% in the last 15 years. Climate change is a great threat and presents a unique opportunity to protect cardiovascular health in the next decades. CO2 equivalent emission is the most convenient unit for measuring the greenhouse gas footprint corresponding to ecological cost. Medical imaging contributes significantly to the CO2 emissions responsible for climate change, yet current medical guidelines ignore the carbon cost. Among the common cardiac imaging techniques, CO2 emissions are lowest for transthoracic echocardiography (0.5–2 kg per exam), increase 10-fold for cardiac computed tomography angiography, and 100-fold for cardiac magnetic resonance. A conservative estimate of 10 billion medical examinations per year worldwide implies that medical imaging accounts for approximately 1% of the overall carbon footprint. In 2016, CO2 emissions from magnetic resonance imaging and computed tomography, calculated in 120 countries, accounted for 0.77% of global emissions. A significant portion of global greenhouse gas emissions is attributed to health care, which ranges from 4% in the United Kingdom to 10% in the United States. Assessment of carbon cost should be a part of the cost-benefit balance in medical imaging.

Full text

Citation: Picano, E.; Mangia, C.;
D’Andrea, A. Climate Change,
Carbon Dioxide Emissions, and
Medical Imaging Contribution. J.
Clin. Med. 2023,12, 215. https://
doi.org/10.3390/jcm12010215
Academic Editors: Sophie I.
Mavrogeni and Pierre Croisille
Received: 23 November 2022
Revised: 5 December 2022
Accepted: 23 December 2022
Published: 27 December 2022
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Journal of
Clinical Medicine
Article
Climate Change, Carbon Dioxide Emissions, and Medical
Imaging Contribution
Eugenio Picano 1, * , Cristina Mangia 2and Antonello D’Andrea 3
1Institute of Clinical Physiology, CNR, 56124 Pisa, Italy
2ISAC—Institute of Sciences of Atmosphere and Climate, CNR, 73100 Lecce, Italy
3Cardiology Division, Nocera Inferiore Hospital, Nocera Inferiore, 84014 Salerno, Italy
*Correspondence: picano@ifc.cnr.it; Tel.: +39-050-3152246; Fax: +39-050-3152374
Abstract:
Human activities have raised the atmosphere’s carbon dioxide (CO
2
) content by 50% in less
than 200 years and by 10% in the last 15 years. Climate change is a great threat and presents a unique
opportunity to protect cardiovascular health in the next decades. CO
2
equivalent emission is the
most convenient unit for measuring the greenhouse gas footprint corresponding to ecological cost.
Medical imaging contributes significantly to the CO
2
emissions responsible for climate change, yet
current medical guidelines ignore the carbon cost. Among the common cardiac imaging techniques,
CO
2
emissions are lowest for transthoracic echocardiography (0.5–2 kg per exam), increase 10-fold
for cardiac computed tomography angiography, and 100-fold for cardiac magnetic resonance. A
conservative estimate of 10 billion medical examinations per year worldwide implies that medical
imaging accounts for approximately 1% of the overall carbon footprint. In 2016, CO
2
emissions from
magnetic resonance imaging and computed tomography, calculated in 120 countries, accounted for
0.77% of global emissions. A significant portion of global greenhouse gas emissions is attributed to
health care, which ranges from 4% in the United Kingdom to 10% in the United States. Assessment of
carbon cost should be a part of the cost-benefit balance in medical imaging.
Keywords: environment; imaging; planet; sustainability
1. Introduction
In the present paper, we present an opinion piece on the environmental impact of
medical imaging, with a special focus on cardiac imaging, and the possible ways to reduce
it. We focus on cardiac imaging for three reasons. First, cardiac imaging examinations are
one of the most important applications of medical imaging (>50% of all nuclear medicine
and invasive fluoroscopy examinations) and are rising with the advent of coronary com-
puted tomography (CT) [
1
]. Second, the relevance of cardiac imaging is especially timely
since the recent European Society of Cardiology, American College of Cardiology, and
American Heart Association general cardiology guidelines established the equipoise of
five different imaging techniques for the diagnosis of chest pain but made no mention of
the environmental impact of the imaging options. This included stress with ultrasound
(US), CT, stress with magnetic resonance imaging (MRI), and nuclear techniques such as
stress with positron emission tomography (PET) and stress with single-photon emission
tomography (SPECT) [
2
,
3
]. Third, as cardiologists and imagers, we are aware that the
culture of environmental sustainability has been present in radiology culture and practice
for years [4] but ignored by mainstream cardiology culture.
2. Climate Changes and Carbon Dioxide
The global influence of the environment profoundly affects cardiovascular risk, in-
cidence, prevalence, and severity [
5
]. Environmental stimuli include social stress, diet,
smoking, chemical contaminants, noise, sleep disturbances, ionizing radiation, air pollution,
and climate change [6].
J. Clin. Med. 2023,12, 215. https://doi.org/10.3390/jcm12010215 https://www.mdpi.com/journal/jcm

J. Clin. Med. 2023,12, 215 2 of 9
Global warming is altering the earth’s global landscape and ocean temperatures. To
date, an increase of 1.09
◦
C has been observed in recent years compared to pre-industrial
levels. Each of the last four decades has been progressively warmer than any previous
decade since 1850. Consequently, temperature variability, heat waves, forest fires, desert
storms, and extreme cold events have become more frequent in many parts of the world,
and the number of deaths increases significantly with the repetition of extreme events [
7
].
The Lancet Countdown on Health and Climate Change reported the effects of extreme
temperatures on health and disease, including cardiovascular diseases. A 2021 global
analysis estimated that more than 5 million deaths per year are associated with non-optimal
temperatures [
8
]. By modifying weather patterns and the consequent emission scenarios,
global warming leads to worsening air pollution, which in turn influences climate change.
Although they are distinct phenomena occurring at different spatiotemporal scales, the
two environmental crises are considered two sides of the same coin [
9
,
10
]. These trends are
expected to worsen in the coming years in the absence of effective countermeasures [11].
It is widely accepted that climate change is caused by high levels of greenhouse gas
(GHG) emissions, such as carbon dioxide (CO
2
), methane, nitrous oxide, etc., due to human
activity [
11
]. From 2010–2019 the average annual global GHG emissions were at their
highest levels in human history. Human activities have raised the atmosphere’s CO
2
content by 50% in less than 200 years and by 10% in the last 15 years [
12
]. As strongly
recommended by the Intergovernmental Panel on Climate Change, urgent and deep GHG
emissions reductions across all sectors are necessary in order to limit global warming to
1.5 ◦C [13].
Climate change is a great threat and presents a unique opportunity to protect cardiovas-
cular health in the next decades [
14
]. In the framework of an integrative, multilevel strategy,
cardiologists are essential to better understand the mechanistic link between climate change
and cardiovascular disease, to promote multilevel (from the government to individuals)
mitigation strategy, identify vulnerable subgroups for more effective treatment of cardio-
vascular complications [15], and adopt carbon-neutral imaging prescription strategies.
CO
2
is not strictly a pollutant but a prototype of GHG and an index of the impact of
human activities on climate change. CO
2
is different from an air pollutant since it is present
in clean air (at a low concentration of 0.04%), essential for a normal life, emitted in human
breath, and not a trigger of acute cardiovascular events. However, it is considered an air
pollutant by law for its direct effect on the climate system and indirect effects on health. The
new landmark climate law passed by the US Senate in August 2022 amends the Clean Air
Act, the country’s air-quality legislation, to define the CO
2
produced by burning fossil fuels
as an “air pollutant”. With the new law, Congress has unequivocally told federal agencies to
tackle CO
2
[
16
]. The Supreme Court ruled, with a 5–4 decision, in 2007 that CO
2
can be
regulated as a pollutant under the Clean Air Act. The Clean Air Act defines “air pollutant”
as “any air pollution agent or combination of such agents, including any physical [or]
chemical
. . .
substance or matter which is emitted into or otherwise enters the ambient
air” and “may reasonably be anticipated to endanger public health or welfare.” In its 2007
decision, the Supreme Court correctly recognized that carbon is a “chemical substance or
matter” that is “emitted into” the air and “endangers public health” by contributing to
rising global temperatures.
With a new conservative majority, the Supreme Court ruled 6–3 on 30 June 2022, that
the Clean Air Act does not give the U.S. Environmental Protection Agency widespread
power to regulate CO
2
emissions. The prevailing opinion reported by Judges of the
Supreme Court in 2022 is as follows, “Now, what is a pollutant? A pollutant is a subject that
is harmful to human beings or to animals or plants. CO
2
is not a pollutant. CO
2
is not harmful
to ordinary things, human beings, or to animals, or plants. It’s actually needed for plant growth.
All of us are exhaling CO
2
right now. So, if it’s a pollutant, we’re all polluting” [
17
]. These
opinions may be legally valid but are less convincing from a logical, pathophysiological,
and medical viewpoint. The CO
2
increase endangers humans, animals, plants, and the
planet. The Climate law passed in August 2022 determined that CO2, for all practical and

J. Clin. Med. 2023,12, 215 3 of 9
legal purposes, must be treated as an air pollutant, and this approach is more reasonable
for physicians.
3. The Environmental Footprint of Imaging Examinations
Marwick and Buonocore evaluated the environmental impact of different cardiac
imaging techniques: stress-US, stress-MRI, and stress-SPECT [
18
]. The impact of MRI and
SPECT on human health followed a clear gradient. MRI was associated with the greatest
environmental damage. SPECT showed intermediate damage between 4 and 11% of the
MRI impact, and US showed the least damage by far, quantified at 0.5–2.0% of the MRI
damage. The basis of these differences is largely due to energy consumption, which leads
to an estimated CO
2
emission of 2 to 3 kg per stress-US (approximately 2.2 kg in Italy and
2.9 kg in the USA in 2013) and up to 200–300 kg per stress-MRI study (229 kg in Italy and
302 kg in the USA), as estimated by Braga et al. [
19
]. With an abdominal scan, the relative
inter-imaging differences are similar to those observed for a cardiac stress study, although
absolute values are lower. When both the production and use phases are considered,
Martin et al. estimated the carbon cost of an abdominal imaging examination at 1.15 kg
CO
2
/examination with a US scan, 6.61 kg CO
2
/examination for a CT scan, and 19.72 kg
CO2/examination with an MRI scan [20].
Similar values were reported by Mc Allister et al., with mean CO
2
emissions/examinations
estimated at 0.5 kg for US, 9.2 kg for CT, and 17.5 kg/scan for MRI [
21
]. The carbon cost
changed with the operating mode, the technology employed, the average scan time, the
region under investigation, and several other variables, including the utilization rate [
22
].
In particular, for any given MRI machine and type of scan, the energy cost accounted
for 98% of the carbon cost, according to Marwick and Buonocore [
18
], and it was heavily
dependent on the utilization rate. With a modern MRI machine, the average energy cost
per exam was estimated at 22.4 kg CO
2
by Esmaeili et al., with a wide range of values
from as low as 48.1 kW/h per patient, with a utilization rate of 90% (262 hospital patients
per month), to an almost 10-fold higher value of 399.8 kW/h with a utilization rate of
10% (29 patients per month) [
23
]. Therefore, any estimate of the absolute carbon cost per
exam is subject to many assumptions and local conditions, from energy cost to utilization
rate. However, the relative carbon cost is remarkably similar, and there is converging
evidence that MRI has the greatest, CT has an intermediate, and the US has the smallest
environmental impact (Figure 1).
Healthcare CO
2
emissions are an important part of global emissions. The healthcare
carbon footprint contributes significantly to the total national carbon footprint [
24
–
27
],
ranging from 10% in the United States in 2016 [
25
] to an estimated 4% in the United
Kingdom [
26
]. Medical imaging contributes significantly to healthcare’s share of emis-
sions, although the exact contribution is subject to a wide range of assumptions [
27
,
28
].
Kouropoulos [
29
] determined that 0.77% of global emissions in 120 countries were caused
by CT and MRI imaging. The study did not include in its estimate emissions from nuclear
medicine, invasive fluoroscopy, chest x-rays, and US, which total billions of examinations
per year (Figure 2). This estimate is expected to grow by 30% from 2018 to 2030, in line
with the expected growth of the global diagnostic imaging market from 2019 to 2024, with
an annual growth rate of 5.5%.
The healthcare sector potentially has a key role in climate change mitigation efforts.
The environmental footprint is also a cost that, while not immediately taken by the payer
as a direct cost, is covered by society as a long-term, downstream, externalized cost all
citizens will pay collectively [30].

J. Clin. Med. 2023,12, 215 4 of 9
Figure 1.
The relative carbon cost (CO
2
emissions/examination) for an abdominal scan with US
(absolute cost 0.5 kg), CT (absolute cost 9.2 kg), and MRI (absolute cost 17.5 kg). From the original
data of McAlister et al. [21].
Figure 2.
The contribution of healthcare and medical imaging to overall carbon emissions on a
planetary scale.
4. Opportunity to Change
The pervasive effects of air pollution and climate change on human health and car-
diovascular disease open new challenges but also unprecedented opportunities for cardio-
vascular disease prevention, diagnosis, and treatment. Greening may affect all phases of
medical imaging, from engineering to production to medical end-users. These actions may
act efficiently to mitigate the environmental footprint of imaging, thus, targeting more than
lowering CO
2
emissions [
31
]. For instance, gadolinium-based contrast media for MRI are
dispersed in water and may lead to drinking water contamination [
32
]. The production of
costly and toxic radioactive waste with nuclear medicine can be effectively minimized with
the development of radiation-free diagnostic methods, as has happened in the last 30 years
with stress-US progressively replacing nuclear cardiology for cost and radiation exposure
concerns [33].

J. Clin. Med. 2023,12, 215 5 of 9
The challenge for the imaging community is to keep high diagnostic standards while
reducing the carbon cost of our activities in a proactive role that is in concert with the
industry and patients [34].
Prescribers and practitioners “must urgently consider the role of imaging in climate change
and mitigate imaging’s harmful environmental impact”, as recently stated in a 2021 call to
action from the President of the American College of Radiology [
35
]. When the diagnostic
information provided by different imaging techniques is similar, low-carbon testing is
preferential over high-carbon testing. Inappropriate testing represents about 50% of current
testing volumes and should be avoided [
36
], especially imaging techniques associated with
high carbon emissions.
There are some data on CO
2
emissions/examinations for US, CT, and MRI and some
relatively old data on SPECT. However, the carbon footprint information is completely
missing for stress-PET, which is widely used in cardiac stress testing with a rising utilization
rate due to lower radiation exposure than stress-SPECT. It would be important to have
more detailed and specific data according to the technology used, operating mode (rest or
stress), use of contrast (for echo or MRI), and drugs employed during the study to generate
an exhaustive catalog of carbon costs to be associated with each imaging procedure. This
information will increase the awareness of doctors and patients and make carbon-neutral
choices easier.
For instance, magnetic resonance will greatly benefit from industrial developments
shifting the focus from machines with high-intensity magnetic fields (3 Tesla or even 6 Tesla)
requiring high energy consumption to an energy-sparing strategy, leading to the diffusion
of new technologies aimed at obtaining the same image quality with lower intensity fields
and much less energy expenditure [37].
5. The Road to Environmental Sustainability in Medical Imaging
Clinicians need simple rules to address the complex issue of environmental impact. We
need more awareness, information, and data to drive a change in time-honored prescription
patterns, feeding legitimate vested interests. There is an opportunity to follow in the
footsteps of social marketing and scientific society campaigns, such as Choosing Wisely and
Image Gently, to reduce the unacceptable rate of inappropriate imaging examinations and
unjustified or unoptimized radiological examinations. These campaigns targeted patients
and doctors, reducing inappropriate testing and dramatically lowering of the radiation
dose per exam through the combined effort of industry, scientists, clinicians, and patient
organizations [
38
,
39
]. Any effort toward environmental sustainability will focus on three
stakeholders: doctors, industry, and patients.
A recent survey in Italy documented that 93% of doctors believe that the emissions of
CO
2
per examination should become an important factor in decision-making for cardiac
imaging [
40
]. The industry is also important due to its efforts in creating modern and
improved medical imaging devices with less carbon cost but no loss in resolution [
41
].
The third stakeholder is the patient. A survey in the United Kingdom showed that 92%
of patients believe sustainability in healthcare operations is important [
42
]. Ideally, the
informed consent paperwork should include the radiologic exposure in multiples of chest
X-rays and the carbon cost in kg of CO
2
emissions compared to standard activities familiar
to the patient, such as driving a car for a certain number of kilometers. Using the updated
estimates from Mc Allister et al., an abdominal US scan (0.5 kg of CO
2
emissions) corre-
sponds to driving a modern car for 4 km, a CT (9.2 kg of CO
2
emissions) for 76 km, and
a resting MRI (17.5 kg of CO
2
emissions) for 145 km [
21
]. This is a way to inform and
explain to patients and doctors what they often ignore regarding the environmental impact
of medical and, specifically, imaging procedures.
Choosing Wisely could be a model to reach the ambitious goal of better environmental
sustainability of medical imaging in the next decade. In the meantime, some simple rules
driven by the available data and common sense can help in everyday practice for a green
transition without lowering the current standard of health care in cardiac imaging:

J. Clin. Med. 2023,12, 215 6 of 9
1.
As prescribers or practitioners, we need to know what our carbon impact is (the exact
environmental cost of each imaging examination);
2.
There is no right or wrong absolute value of carbon cost, but certainly, the wrong
value is the one we ignore;
3. Through its effects on climate change, carbon is a cost taken up by society;
4.
Through its effects on climate change, carbon is a health risk taken up by the entire
population, including those unexposed to testing;
5. Like radiation, carbon cost should always be justified;
6. Like radiation, carbon cost should always be optimized;
7.
Like radiation, the responsibility for inappropriate carbon costs should be that of both
the prescriber and the practitioner;
8.
If we include carbon cost in our imaging cost-benefit balance, the industry will start
on the road to achieving the same image quality with less carbon cost;
9.
Carbon is important in all fields of the economy, from housing to energy and trans-
portation, and also in medicine to preserve the current standard of care and environ-
mental integrity for future generations;
10.
Prescribing an imaging test is a medical and social act [43].
The cost-benefit assessment should include immediate cost, radiation risk, and carbon
cost (Figure 3).
Figure 3.
The cost-benefit assessment in medical imaging (first row) includes the medical benefit
(such as diagnostic accuracy) balanced with the acute risks, such as the occurrence of myocardial
infarction during stress. Over the last two decades, a more comprehensive assessment was introduced.
Integrating on the cost side is the economic cost (second row), the radiological risk linearly related to
the long-term risk of cancer (third row), and now, the environmental or carbon cost related to the
detrimental effect on the planet (last row).
It is unrealistic to achieve the goal of sustainability without, or even against, the
medical imaging community. Conversely, the cardiology and cardiac imaging community
cannot remain neutral in this debate. Environmental sustainability in cardiology and
cardiac imaging is essential in the quest for sustainability in healthcare [44].
6. Conclusions
Human health is one of the earliest biosensors of climate change, and cardiovascular
disease increases in frequency and severity with climate change. Doctors are fearful of
climate change, but also a part of the problem since healthcare contributes significantly
to the overall carbon footprint [
45
]. Cardiac imaging immensely improved the quality of
cardiology care, but it is also a recognized source of population damage through radiation

J. Clin. Med. 2023,12, 215 7 of 9
exposure and environmental damage through CO
2
emissions. The cardiology and cardiac
imaging communities can have a proactive role in the decarbonization of imaging, in
teamwork with industry and patients, and as gatekeepers to improve imaging quality and
cost-effectiveness. The Choosing Wisely campaign celebrated its 10th birthday in 2022
and has taught patients and doctors that overuse is an equity issue and that avoiding
overuse can protect patient safety [
46
]. The Green Heart initiative will eventually push
Choosing Wisely’s gratifying experience of promoting appropriateness in imaging further
to include the economic and radiological cost and the carbon cost of medical imaging in
decision-making. Avoiding medical imaging overuse can also protect planet safety [47].
Author Contributions: Conceptualization, E.P., C.M. and A.D.; writing—original draft preparation,
E.P.; writing—review and editing, C.M. and A.D. All authors have read and agreed to the published
version of the manuscript.
Funding: The research received no external funding.
Institutional Review Board Statement:
The study was conducted according to the guidelines of
the Declaration of Helsinki and approved by the institutional ethics committees as a part of the SE
2030 study (291/294/295-Comitato Etico Lazio-1, 8 March 2021; Clinical trials. Gov Identifier NCT
050.81115).
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the study.
Data Availability Statement:
The data presented in this study are available on request from the
corresponding author. The data are not publicly available due to privacy law.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Picano, E.; Vañó, E.; Rehani, M.M.; Cuocolo, A.; Mont, L.; Bodi, V.; Bar, O.; Maccia, C.; Pierard, L.; Sicari, R.; et al. The appropriate
and justified use of medical radiation in cardiovascular imaging: A position document of the ESC Associations of cardiovascular
imaging, Percutaneous cardiovascular interventions, and electrophysiology. Eur. Heart J. 2014,35, 665–672. [CrossRef]
2.
Knuuti, J.; Wijns, W.; Saraste, A.; Capodanno, D.; Barbato, E.; Funck-Brentano, C.; Prescott, E.; Storey, R.; Deaton, C.; Cuisset, T.;
et al. ESC Scientific Document Group 2019 ESC Guidelines for the diagnosis and management of chronic coronary syndromes.
Eur. Heart J. 2020,4, 407–477. [CrossRef] [PubMed]
3.
Gulati, M.; Levy, P.D.; Mukherjee, D.; Amsterdam, E.; Bhatt, D.L.; Birtcher, K.K.; Blankstein, R.; Boyd, J.; Bullock-Palmer, R.P.;
Conejo, T.; et al. AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline for the evaluation and diagnosis of chest pain: A
report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. J.
Am. Coll. Cardiol. 2021,78, e187–e285. [CrossRef] [PubMed]
4.
Slanetz, P.J.; Schoen, J.H.; Maturen, K.E.; Zigmund, B. Green Is Rad: Engaging Radiologists in Building More Sustainable
Radiology Practices. J. Am. Coll. Radiol. 2022,6, S1546. [CrossRef]
5. Bhatnagar, A. Environmental Determinants of Cardiovascular Disease. Circ. Res. 2017,121, 162–180. [CrossRef] [PubMed]
6.
Münzel, T.; Hahad, O.; Sørensen, M.; Lelieveld, J.; Duerr, G.D.; Nieuwenhuijsen, M.; Daiber, A. Environmental risk factors and
cardiovascular diseases: A comprehensive expert review. Cardiovasc. Res. 2022,118, 2880–2902. [CrossRef]
7. Romanello, M.; McGushin, A.; Di Napoli, C.; Drummond, P.; Hughes, N.; Jamart, L.; Kennard, H.; Lampard, P.; Rodriguez, B.S.;
Arnell, N.; et al. The 2021 report of the Lancet Countdown on health and climate change: Code red for a healthy future. Lancet
2021,398, 1619–1662. [CrossRef]
8.
Zhao, Q.; Guo, Y.; Ye, T.; Gasparrini, A.; Tong, S.; Overcenco, A.; Urban, A.; Schneider, A.; Entezari, A.; Vicedo-Cabrera, A.M.;
et al. Global, regional, and national burden of mortality associated with non-optimal ambient temperatures. Lancet Planet. Health
2021,5, e415–e425. [CrossRef] [PubMed]
9.
Von Schneidemesser, E.; Monks, P.S.; Allan, J.D.; Bruhwiler, L.; Forster, P.; Fowler, D.; Lauer, A.; Morgan, W.T.; Paasonen, P.; Righi,
M.; et al. Chemistry and the linkages between air quality and climate change. Chem. Rev. 2015,115, 3856–3897. [CrossRef]
10.
Niklas Hagelberg UN Environment l Program. Air Pollution and Climate Change. Two Sides of the Same Coin. 23 April 2019.
Available online: www.unep.org/news-and-stories/story/air-pollution-and-climate-change-two-sides-same-coin (accessed on
20 November 2022).
11.
NASA. Global Climate Change. Carbon dioxide. Latest Measurement June 2022. Carbon Dioxide|Vital Signs—Climate Change:
Vital Signs of the Planet. Available online: nasa.gov (accessed on 20 November 2022).
12.
Montzka, S. The NOAA Annual Greenhouse Gas Index (AGGI). NOAA Global Monitoring Laboratory Website. Available online:
https://gml.noaa.gov/aggi/aggi.html (accessed on 2 December 2022).

J. Clin. Med. 2023,12, 215 8 of 9
13.
Pörtner, H.-O.; Roberts, D.; Tignor, M.; Poloczanska, E.; Mintenbeck, K.; Alegría, A.; Craig, M.; Langsdorf, S.; Löschke, S.; Möller,
V.; et al. Climate Change 2022: Impacts, Adaptation and Vulnerability; IPCC Sixth Assessment Report; IPCC: Geneva, Switzerland,
2022.
14.
Watts, N.; Amann, M.; Arnell, N.; Ayeb-Karlsson, S.; Belesova, K.; Berry, H.; Bouley, T.; Boykoff, M.; Byass, P.; Cai, W.; et al. The
2018 report of the Lancet Countdown on health and climate change: Shaping the health of nations for centuries to come. Lancet
2018,392, 2479–2514. [CrossRef]
15.
Khraishah, H.; Alahmad, B.; Ostergard, R.L.; AlAshqar, A.; Albaghdadi, M.; Vellanki, N.; Chowdhury, M.M.; Al-Kindi, S.G.;
Zanobetti, A.; Gasparrini, A.; et al. Climate change and cardiovascular disease: Implications for global health. Nat. Rev. Cardiol.
2022,19, 798–812. [CrossRef] [PubMed]
16. Friedman, L. Democrats designed the climate law to be a game-changer. The New York Times, 22 August 2022.
17.
Stern, M.J. Justice Alito Declares “Carbon Dioxide Is Not a Pollutant” FEB 13, 2017. Available online: Slate.com/news-and-politics
(accessed on 20 November 2022).
18.
Marwick, T.H.; Buonocore, J. Environmental impact of cardiac imaging tests for the diagnosis of coronary artery disease. Heart
2011,97, 1128–1131. [CrossRef] [PubMed]
19.
Braga, L.; Vinci, B.; Leo, C.G.; Picano, E. The true cost of cardiovascular imaging: Focusing on downstream, indirect, and
environmental costs. Cardiovasc. Ultrasound 2013,11, 10. [CrossRef] [PubMed]
20.
Martin, M.; Mohnke, A.; Lewis, G.M.; Dunnick, N.R.; Keoleian, G.; Maturen, K.E. Environmental Impacts of Abdominal Imaging:
A Pilot Investigation. J. Am. Coll. Radiol. 2018,15, 1385–1393. [CrossRef] [PubMed]
21.
McAlister, S.; McGain, F.; Petersen, M.; Story, D.; Charlesworth, K.; Ison, G.; Barratt, A. The carbon footprint of hospital diagnostic
imaging in Australia. Lancet Reg. Health West Pac. 2022,24, 100459. [CrossRef]
22.
Heye, T.; Knoerl, R.; Wehrle, T.; Mangold, D.; Cerminara, A.; Loser, M.; Plumeyer, M.; Degen, M.; Lüthy, R.; Brodbeck, D.; et al.
The Energy Consumption of Radiology: Energy- and Cost-saving Opportunities for CT and MRI Operation. Radiology
2020
,295,
593–605. [CrossRef]
23.
Esmaeili, A.; McGuire, C.; Overcash, M.; Ali, K.; Soltani, S.; Twomey, J. Environmental impact reduction as a new dimension for
quality measurement of healthcare services. Int. J. Health Care Qual. Assur. 2018,31, 910–922. [CrossRef]
24.
Pichler, P.; Jaccard, I.; Weisz, U.; Weisz, H. International comparison of health care carbon footprints. Environ. Res. Lett.
2019
,14,
064004. [CrossRef]
25.
Eckelman, M.J.; Sherman, J. Environmental Impacts of the U.S. Health Care System and Effects on Public Health. PLoS ONE
2016
,
11, e0157014. [CrossRef]
26.
Sustainable Development Unit. UK National Health Service 2016 Carbon Footprint Updatefor NHS in England; Sustainable Develop-
ment Unit: Cambridge, UK, 2015.
27.
Malik, A.; Lenzen, M.; McAlister, S.; McGain, F. The carbon footprint of Australian health care. Lancet Planet Health
2018
,2,
e27–e35. [CrossRef]
28.
Diagnostic Imaging Market Global Forecast to 2024|MarketsandMarket. Available online: www.marketsandmarkets.com/
Market-Reports/diagnostic-imaging-market-411.html (accessed on 20 November 2022).
29.
Kouropoulos, G.P. A predictive model for the estimation of carbon dioxide emissions of magnetic resonance imaging units and
computed tomography scanners. J. Urban Environ. Eng. 2018,12, 172–187. [CrossRef]
30.
Chaudhry, S.M.; Ahmed, R.; Shafiullah, M.; Duc Huynh, T.L. The impact of carbon emissions on country risk: Evidence from the
G7 economies. J. Environ. Manag. 2020,265, 110533. [CrossRef] [PubMed]
31.
Woolen, S.A.; Kim, C.J.; Hernandez, A.M.; Becker, A.; Martin, A.J.; Kuoy, E.; Pevec, W.C.; Tutton, S. Radiology Environmental
Impact: What Is Known and How Can We Improve? Acad. Radiol. 2022,15, S1076–S6332. [CrossRef] [PubMed]
32.
Brünjes, R.; Hofmann, T. Anthropogenic gadolinium in freshwater and drinking water systems. Water Res.
2020
,182, 115966.
[CrossRef]
33.
Jouni, H.; Askew, J.W.; Crusan, D.J.; Miller, T.D.; Gibbons, R.J. Temporal trends of single-photon emission computed tomography
myocardial perfusion imaging in patients without prior coronary artery disease: A 22-year experience at a tertiary academic
medical center. Am. Heart J. 2016,176, 127–133. [CrossRef]
34. Picano, E. Sustainability of medical imaging. BMJ 2004,328, 578–580. [CrossRef]
35.
Schoen, J.; McGinty, G.B.; Quirk, C. Radiology in Our Changing Climate: A Call to Action. J. Am. Coll. Radiol.
2021
,18, 1041–1043.
[CrossRef]
36.
Carpeggiani, C.; Marraccini, P.; Morales, M.A.; Prediletto, R.; Landi, P.; Picano, E. Inappropriateness of cardiovascular radiological
imaging testing; a tertiary care referral center study. PLoS ONE 2013,8, e81161. [CrossRef]
37.
Qin, C.; Murali, S.; Lee, E.; Supramaniam, V.; Hausenloy, D.J.; Obungoloch, J.; Brecher, J.; Lin, R.; Ding, H.; Akudjedu, T.N.; et al.
Sustainable low-field cardiovascular magnetic resonance in changing healthcare systems. Eur. Heart J. Cardiovasc. Imaging
2022
,
23, e246–e260. [CrossRef]
38.
Hirschfeld, J.W., Jr.; Ferrari, V.A.; Bengel, F.M.; Bergersen, L.; Chambers, C.E.; Einstein, A.J.; Eisenberg, M.J.; Fogel, M.A.; Gerber,
T.C.; Haines, D.E.; et al. ACC/HRS/NASCI/SCAI/SCCT Expert consensus document on optimal use of ionizing radiation in
cardiovascular imaging: Best practices for safety and effectiveness. J. Am. Coll. Cardiol. 2018,71, e283–e351. [CrossRef]

J. Clin. Med. 2023,12, 215 9 of 9
39.
Smith-Bindman, R.; Kwan, M.L.; Marlow, E.; Theis, M.K.; Bolch, W.; Cheng, S.Y.; Bowles, E.J.A.; Duncan, J.R.; Greenlee, R.T.;
Kushi, L.H.; et al. Trends in Use of Medical Imaging in US Health Care Systems and Ontario, Canada, 2000–2016. JAMA
2019
,
322, 843–856. [CrossRef] [PubMed]
40.
Ciampi, Q.; Antonini-Canterin, F.; Barbieri, A.; Barchitta, A.; Benedetto, F.; Cresti, A.; Miceli, S.; Monte, I.; Petrella, L.; Trocino,
G.; et al. Reshaping of Italian Echocardiographic Laboratories Activities during the Second Wave of COVID-19 Pandemic and
Expectations for the Post-Pandemic Era. J. Clin. Med. 2021,10, 3466. [CrossRef] [PubMed]
41.
Global Electronic Council. State of Sustainability Research. Medical Imaging Equipment. Prepared for Medical Equipment Proactive
Alliance; Global Electronic Council: Portland, OR, USA, 2022.
42.
NHS Sustainable Development Unit. Sustainability Survey. 1 February 2022. Available online: www.ipsos.com/en-uk/nhs-sdu-
sustainability-survey (accessed on 20 November 2022).
43.
Picano, E. Economic, ethical, and environmental sustainability of medical imaging. Eur. Heart J.
2022
, ehac716. [CrossRef]
[PubMed]
44.
Schoen, J.; Marrero-Gonzalez, A. Climate Change and Radiology. Climate Change and Radiology | American College of
Radiology. Available online: acr.org (accessed on 20 November 2022).
45.
Dzau, V.J.; Levine, R.; Barrett, G.; Witty, A. Decarbonizing the U.S. Health Sector—A Call to Action. N. Engl. J. Med.
2021
,385,
2117–2119. [CrossRef] [PubMed]
46.
Baron, R.J.; Lynch, T.J.; Rand, K. Lessons From the Choosing Wisely Campaign
'
s 10 Years of Addressing Overuse in Health Care.
JAMA Health Forum 2022,3, e221629. [CrossRef]
47. Picano, E. Air cardiology is now on air. Eur. Heart J. 2021,42, 961–962. [CrossRef]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.