Climate change and cancer

Abstract

No one questions the importance of investments to prevent and treat cancer. Nearly 10 million people worldwide will die from cancer this year alone.1 In high-income nations, more people will die of cancer than of any other cause2 and, globally, cancer is the second leading cause of death.3 Over the past 100 years, many cancers have been transformed from death sentences into frequently preventable and potentially curable diseases through the identification and control of cancer risk factors, improvement in early detection, and the development of effective cancer therapies.4, 5 In fact, differences in risk factor exposures and access to care largely explain global patterns in cancer incidence and mortality.6 The prospects for further progress in cancer prevention and control in this century are bright but face an easily overlooked threat from climate change, which can impact both exposure to cancer risk factors and access to cancer care. Climate change is already increasing cancer risk through increased exposure to carcinogens after extreme weather events such as hurricanes and wildfires. In addition to increasing cancer risk, climate change is also impacting cancer survival. Extreme weather events can impede patients' access to cancer care and the ability of cancer treatment facilities to deliver care.7 For these reasons, cancer treatment facilities should ensure that their disaster preparedness plans can withstand climate threats and should evaluate and mitigate their own contributions to greenhouse gas emissions. Fortunately, many actions that address climate change also reduce carcinogen releases or exposures. Climate change creates conditions favorable to the greater production of and exposure to known carcinogens. Extreme weather events are already increasing the amount of carcinogens in communities. Hurricane Harvey's unprecedented precipitation, which human-induced climate change made 3.5 times more likely to occur,8 inundated chemical plants, oil refineries, and Superfund sites that contained vast amounts of carcinogens, which were released into the Houston community.9 The half-life of some of these carcinogens, such as dioxin, is up to 50 years.10 Climate change has also fueled longer wildfire seasons11, 12 and promoted more frequent and larger fires.13-15 Wildfires release immense amounts of air pollutants known to cause cancer, such as particulate matter.16 These pollutants can also travel great distances17 and can degrade air quality for months.18 During the unprecedented wildfires in northern California in 2018, air pollution in the San Francisco Bay Area was among the worst in the world,19 and the smoke stretched across the continent to New England.20 There are also projections of the future impact of climate change on cancer risk. For example, climate change may also increase dietary exposure to aflatoxin,21 another potent carcinogen22 produced by fungi that can contaminate staple food crops. Climate change can disrupt access to and receipt of care throughout the cancer care continuum. Successful prevention, diagnosis, and treatment of cancer can require multiple visits to medical facilities. This makes patients with cancer especially vulnerable to the effects of natural disasters on access to care.23 As climate change is altering the frequency, intensity, and behavior of extreme weather events, it is exacerbating the vulnerability of communities to natural disasters by making it harder to prepare and respond to increasingly unpredictable and severe weather.24 Consider hurricanes, for instance. Atmospheric warming is decreasing the translational speed and increasing the water capacity of hurricanes,25, 26 which increases the probability of catastrophic rainfall when storms stall over populated areas. Hurricane Harvey in 2017, for example, deposited more rainfall on Houston than any other US hurricane on record.27 For patients with cancer, the effects of hurricanes on access to cancer care can mean the difference between life and death. A recent study showed that patients with non–small cell lung cancer were more likely to die if their radiation therapy was interrupted by a hurricane.28 Extreme weather events can interfere with cancer care even when they strike far from where care is delivered. Hurricane Maria in 2018, for example, shuttered a factory in Puerto Rico that was responsible for the bulk of small-volume intravenous fluid bags for the continental United States. This led to national shortages of intravenous fluids and difficulties with intravenous medication administration in many cancer treatment facilities.29 Extreme weather events can disable transportation, communication systems, and power systems. (Maria incapacitated radiation oncology services on the island as well).30 Disruptions to health care access and delivery are especially concerning for patients with cancer because delays in cancer diagnosis and treatment initiation and interruption of cancer treatment can worsen cancer prognosis.23 Extreme weather events also threaten the laboratory and clinic infrastructure dedicated to cancer care in the United States. Many cancer treatment facilities have begun to make themselves more resilient to the threats of extreme weather and climate change. For example, the new Memorial Sloan Kettering Cancer Center building in New York City, built in the wake of Hurricane Sandy in 2012, has had extensive review of plans to provide resilience to future flooding events. Such actions are not only necessary to maintain operations, they are increasingly required by local building codes and federal policies. In September 2016, the Federal Register posted the final rule on emergency preparedness requirements for Medicare and Medicaid participating providers and suppliers.31 As of 2019, the National Cancer Institute (NCI) recognizes 71 cancer centers,32 and the American College of Surgeons' Commission on Cancer (CoC) provides accreditation to more than 1500 cancer care programs in the United States.33 Whether these facilities are actively engaged in preparing for the impacts of climate change on the delivery of health care is currently unknown. To improve preparedness and transparency, the Centers for Medicare and Medicaid Services could provide information about how the emergency preparedness requirement is being enforced, as well as the consequences for noncompliance. In addition, the NCI and the CoC could include compliance with the Centers for Medicare and Medicaid Services Emergency Preparedness Rule as a requirement for accreditation and require that facilities have their emergency preparedness plan easily accessible to patients. The cancer care continuum involves multiple interactions with the health care system, from prevention, screening, and diagnosis through cancer treatment and survivorship. The health care system is the second most energy-intensive industry in the United States according to the Energy Information Administration34 and, in 2013, the carbon emissions from the US health care sector alone exceeded the carbon emissions in the entire United Kingdom.35 Minimizing the carbon footprint of health care can contribute to broader efforts to reduce carbon pollution and promote better outcomes for patients across the cancer care continuum.36 The largest contributors to the carbon footprint of the US health care system are the hospital and pharmaceutical industry sectors.34, 37 Within hospitals, operating rooms, which consume large amounts of energy for ventilation, are a major emissions source, as are anesthetic gases commonly used in surgery, which can be thousands of times more potent than carbon dioxide.38 Recent analysis has found that the pharmaceutical industry is 50% more carbon-intensive than the automotive industry.39 Given the heavy reliance of cancer care on surgeries, radiology services, and pharmaceuticals, cancer care may be responsible for an outsized contribution to health care's overall carbon footprint. To date, no studies have estimated the carbon footprint of cancer care. Some emission sources specific to cancer care are listed in Table 1. Cancer prevention and early detection usually occur in primary care settings, whereas diagnosis, staging, and treatment (surgery, systemic therapy, and radiotherapy) commonly occur in more specialized facilities. Medical devices are indispensable for effective cancer screening, diagnosis, treatment, rehabilitation, and palliative care. The energy expenditure associated with operating cancer treatment facilities and medical devices, as well as the manufacturing, packaging, and shipment of devices and pharmaceuticals, contributes significantly to greenhouse gas emissions in cancer care. The sources of cancer care's carbon footprint are also where opportunities for greenhouse gas emission reductions can be found: operating room ventilation can be optimized based on occupancy and demand, anesthetic gases can be captured or at a minimum prioritized based upon their warming potentials, and more energy-efficient computed tomography and magnetic resonance imaging machines can be acquired. But much more can be done at cancer treatment facilities. In addition, the health care system purchases significant amounts of food and can decrease its environmental impact by seeking low-carbon food manufacture, shipment, and waste options.35 The transportation of patients and staff to specialized cancer treatment facilities adds to the environmental impact of the health care system. In addition to industry-focused and health care system–focused approaches to reducing emissions, some efforts to decentralize cancer care might be beneficial to both patients and the environment. Although this might not be feasible for all cancer treatment modalities—centralization of cancer surgery has been shown to have superior results for some cancer sites40-42—relying on telehealth for some follow-up appointments43 and identifying radiotherapy strategies that minimize the number of visits44 not only might reduce the environmental impact associated with traveling to receive treatment but also might improve patients' access to cancer care, as many studies have shown that greater travel distance is associated with reduced compliance with treatment guidelines.45, 46 Vehicle emissions are also a major contributor to climate change.47 Cancer care providers can support policies and other efforts that promote shifting from driving to public transit and active models of travel, such as walking and cycling. These measures would not only reduce transport-related greenhouse gas emissions48 but, by increasing physical activity, can also decrease cancer risk49, 50 and improve cancer survival.51, 52 Some cancer treatment facilities have begun to consider their own carbon footprint and started a process to achieve carbon neutrality. However, the proportion of health care institutions reporting environmental sustainability activities lags behind other economic sectors,53 and it is not clear how many institutions involved in cancer care delivery currently assess the climate or broader environmental impact of their activities. Encouraging carbon footprint measurement and public reporting, possibly through the NCI's and CoC's accreditation processes, would help identify opportunities for decreasing the environmental impact of the health care system and work as an incentive for the implementation of sustainability efforts. Because many anthropogenic drivers of climate change are also carcinogens,54 climate mitigation efforts have health co-benefits, and especially benefits to cancer prevention and outcomes. All stakeholders concerned with the prevention and treatment of cancer have much at stake with climate change and a heavy dependence on fossil fuels, which accounts for nearly 80% of all the carbon pollution.55 Therefore, providers involved in cancer care delivery have compelling reasons to be actively involved in the development of climate policies.56 For example, air pollutants directly harmful to health are emitted by combustion processes that also contribute to greenhouse gas emissions.57 More energy-efficient buildings and operating rooms can reduce greenhouse gas emissions and carcinogenic air pollution. So too can greater use of public and active transportation, which can increase physical activity, decrease cancer risk,49, 50 and improve cancer survival.51, 52 Among the many opportunities to capitalize on the health co-benefits of climate-mitigating strategies, health professionals can advocate for the inclusion of the health impact of emissions on cancer incidence and survivability in the development of new climate policies58 as well as voice opposition to attempts to dismantle existing laws protecting the environment. In the past 3 years, many attempts have been made to weaken the Clean Air Act,59 which decreased 6 of the most dangerous air pollutants, including carcinogens, by 74% while the gross domestic product grew by 275% between 1970 and 2016.60 Of note, between 2016 and 2018, for the first time after decades of progress, particulate matter air pollution worsened in the United States, possibly because of a decrease in enforcement of the Clean Air Act.61 Some dietary patterns are also detrimental to both health and the environment.62, 63 Poor diets are a leading cause of premature death,64 and the agricultural sector contributes to approximately 30% of anthropogenic greenhouse gas emissions worldwide.65, 66 Meat from ruminants has the highest environmental impact, whereas plant-based foods cause fewer adverse environmental effects per unit weight, per serving, per unit of energy, or per protein weight.67 Furthermore, the International Agency for Research on Cancer classifies the consumption of processed meats as carcinogenic to humans, and red meat consumption is associated with increased colorectal cancer risk.68 Replacing animal source foods with plant-based foods, through guidelines provided to patients and changes made in the food services provided at cancer treatment facilities, would confer both environmental and health benefits.62, 69 Although some may view these issues as beyond the scope of responsibility of the nation's cancer treatment facilities, one need look no further than their mission statements, all of which speak to eradicating cancer. Climate change and continued reliance on fossil fuels push that noble goal further from reach. However, if all those whose life work is to care for those with cancer made clear to the communities they serve that actions to combat climate change and lessen our use of fossil fuels could prevent cancers and improve cancer outcomes, we might see actions that address climate change flourish and the attainment of our mission to reduce suffering from cancer grow nearer.

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