Climate change has been described as the greatest global health challenge of the 21st century. Many medical societies, including the American Medical Association, American Academy of Pediatrics, and the American College of Emergency Physicians, have warned about the health care industry’s contribution to greenhouse gas emissions and climate change’s potentially dire impacts on public health. Additionally, health care systems across the country have formed the Health Care Climate Council to help decrease their greenhouse gas emissions and establish more environmentally sustainable practices. Notably, Kaiser Permanente and Gundersen Health System in Wisconsin are already carbon neutral. As large hospital systems and our colleagues in other specialties move toward environmental sustainability, we as radiologists should consider our own practices, asking ourselves what changes we can make to limit our contribution to climate change.

What Is Global Warming? What Is Climate Change?

Although they are often used interchangeably, the terms global warming and climate change refer to distinct, but closely related phenomena. Global warming refers to the dramatic increase in average global surface temperature, which has occurred since the beginning of the industrial age. This warming is largely driven by carbon dioxide, methane, and other greenhouse gases emitted by human activities, which trap solar radiation reflected from the earth’s surface and heat the earth’s atmosphere. As a result of increased greenhouse gases emissions, average global surface temperature has increased approximately 1°C (1.8°F) since the middle of the 19th century.

Warming temperatures have led to an increase in intense, unpredictable weather events and to climate change, a term which describes long-term fluctuations in temperature, humidity, rainfall, and other meteorological patterns.

How Does Climate Change Impact Human Health?

The interactions between climate and health are complex and can be divided into direct and indirect impacts. Direct impacts are easier to measure and are related to extreme weather events, such as heatwaves, floods, droughts, and wildfires. In addition to the traumatic injuries that these events can cause to individuals, extreme weather events can disrupt supply chains and operations of health care systems. These disruptions can decrease the short-term availability and quality of health care for entire populations.

The indirect effects of climate change include longer-term phenomena: distribution of vector-borne diseases, increased food insecurity, increased intensity and duration of allergy seasons, and worsening air and water quality.

The severity of the direct and indirect impacts of climate change for an individual or population can be amplified by geographic location, age, sex, and socioeconomic status. Consequently, the health impacts of climate change are often disproportionately felt by those who are least responsible.

How Does Health Care Contribute to Climate Change?

Health care systems in the United States are estimated to generate approximately 8–10% of the country’s greenhouse gas emissions— more than is emitted by the entire United Kingdom.

Health care emissions are categorized into 3 scopes:

• Scope 1 emissions are direct emissions from health care and hospital operations, such as anesthetic gases or onsite incinerators.
• Scope 2 emissions are calculated from direct energy expenditures from health care operations.
• Scope 3 emissions are indirect emissions from the supply chain and waste treatment.

In the US, scope 3 emissions account for approximately 82% of health care-related emissions. Scope 1 and Scope 2 emissions account for 7% and 11% of emissions, respectively.

In radiology, the majority of our emissions fall into Scopes 2 and 3. Our Scope 2 emissions include the energy used by our facilities to power our scanners, PACS stations, electronic and imaging equipment in interventional suites, as well as heating, ventilation, and cooling (HVAC) systems. Our Scope 3 emissions include the energy used to produce, reuse, and dispose of scanners, procedure kits, and single-use supplies.

How Does Radiology Contribute to Climate Change?

Radiology’s greenhouse gas emissions are beginning to receive attention, and several recent studies help us understand our carbon footprint. Ultrasound generates fewer greenhouse gas emissions than CT and MRI, both in use and in production, therefore contributing less to Scope 2 and 3 emissions alike. At one hospital in Switzerland, three CT scanners and four MRI machines accounted for approximately 4% of the hospital’s total energy use. Notably, researchers found that two-thirds of energy consumption occurred in the idle state for CT, and one-third occurred in the idle state for MRI. In a more recent study of an academic interventional radiology suite, investigators estimated that 23,500 kilograms of CO2 equivalents were emitted during a single work week. This is comparable to the amount of carbon a passenger vehicle would emit over 93,825 kilometers (58,300 miles) or the amount of carbon sequestered by 389 trees over 10 years. HVAC systems and single-use disposable items were the biggest contributors to greenhouse gas emissions from the interventional radiology suite. Particularly, researchers found that 57% of HVAC energy use occurred outside of work hours, when the unit was largely unoccupied. These studies highlight the fact that much of our energy use occurs when systems are idle, providing no benefit to patient care. For radiologists, there are many instances where we can reduce our operating costs and greenhouse gas emissions with minimal impact on our practices.

How Can Radiologists Address Climate Change?

There are several opportunities for radiologists to address climate change in our practices and in the health care system at large. As a first step, we can implement simple cost-saving interventions with marginal, if any, upfront costs. Such interventions include double-sided printing, switching from fluorescent to LED lighting, and turning off those lights and other electronics, including PACS stations, when they are not in use. In interventional radiology, we can relax climate control parameters when the suite is not in use, streamline procedure packs to minimize equipment that is unlikely to be needed, and choose reusable equipment, rather than single-use supplies, when possible. In both diagnostic and interventional radiology, we can work with vendors to increase the energy efficiency of our scanners in idle and off states and to recycle the heat generated by our scanners.

More broadly, we can advocate for sustainable practices in our clinics and hospitals and with our peers and colleagues. At the regional and national level, we can join organizations like the Medical Society Consortium on Climate and Health, which educates physicians and other health care professionals about the medical system’s contribution to climate change, while offering ways to decrease our carbon footprint. Through these groups and our radiology societies like ARRS, we can advocate for broader policy changes, encouraging systemic reductions to our collective footprint and improvements in public health.

The potentially profound impacts that global warming and climate change may have on public health can only be mitigated if all parts of our society—including the health care system—reduce greenhouse gas emissions. Be it implementing more sustainable practices in our hospitals and clinics or advocating for overall change, radiologists can play a key role in helping to reduce health care’s carbon footprint and protecting the health of ourselves, our colleagues, our families, and our patients.