Critical Issues For Climate Change And Health

In the process of identifying and characterizing research needs on the health effects of climate change for the 11 categories of outcomes, it became apparent that several crosscutting issues cover all aspects of the research needs. In the sections below, we briefly summarize the major areas of overlap.

1. Susceptible, vulnerable, and displaced populations

The World Health Organization defines “environment” as “all modifiable physical, chemical, and biological factors external to the human host and all related behaviors that are important for the establishment and maintenance of a healthy habitable environment.” Under this definition, it is likely that the environment can influence most human diseases and illnesses. There are certain populations that are at risk from environmental factors that affect health, and such populations present unique concerns when considering health risks from climate change.

“Susceptibility” refers to intrinsic biological factors that may increase an individual’s health risk at a given exposure level. Examples of susceptibility factors that have been shown to increase individual health risks are certain genetic variations, life stage such as childhood, and medical history such as prior history of illness. “Susceptibility” refers to human populations at higher risk due to environmental or personal factors. For example, people living in mud brick homes in earthquake zones have a higher risk of injury from building collapse than people living in structures built with modern technologies and stronger materials. Populations living in poverty, those who abuse substances, and those with mental illness have increased vulnerability to many of the environmental changes that result from climate change.

Another form of susceptibility is seen in displaced populations, who are at higher risk for a number of diseases, including diarrheal and vectorborne diseases caused by exposure to poor sanitation, as well as mental health illnesses caused by increased acute and long-term stress.

Populations with both susceptibility and vulnerability factors are called “vulnerable” populations. An example of a vulnerable population would be some members of the displaced population who evacuated to New Orleans after Hurricane Katrina. Studies have shown that within this population, older people (susceptible) who were low-income (vulnerable) were the slowest to recover from disaster. Virtually every human disease is likely to have both a susceptible and vulnerable population associated with it. A key aspect of mitigating the effects of climate change is a better understanding of the diseases and the unique risks of different exposed or affected populations so that strategies can be developed that take such risks into account and are tailored to address them.

In terms of diseases associated with climate change, several populations are particularly at risk. Children, pregnant women, and the elderly are generally more vulnerable, especially to heat and weather-related illness and death, vector-borne and zoonotic diseases, and waterborne and foodborne diseases. In addition, children and certain minority groups are more susceptible to asthma and allergies that may be exacerbated by climate change. Genetic links and markers that help identify and define susceptible populations for many climate-related diseases exist.

Poverty generally makes people more vulnerable to many of the health impacts of climate change, largely due to inadequate access to health care. Poverty also increases the risk that populations displaced by extreme weather events or environmental degradation will not be able to recover easily, and as a result, face much higher disease risk. The same is true for people who abuse drugs, those with mental illness, and others who are socially isolated for a variety of reasons. For such populations, the effects of climate change such as temperature and weather extremes, disruptions in access to public services including health care and food assistance programs, and increased stress are all exacerbated by their pre-existing conditions or circumstances. Outdoor workers and people living in coastal and riverine areas are also likely to experience increased vulnerability to climate-induced environmental changes as a result of flooding and extreme weather events.

Data to support a comprehensive understanding of which populations will be most sensitive and vulnerable to diseases affected by climate change are generally lacking at this time; however, data are available that identify vulnerable populations for certain diseases with environmental causes or triggers that are likely to change due to climate change. For example, reducing vehicle emissions may mean that populations living near freeways, who are at higher risk of heart disease, asthma, and spontaneous abortions, may see a reduction in the incidence of these effects. Expanding research on these diseases to include the effects of climate change will help identify vulnerable populations, and also help develop the strategies needed to adapt to climate change and avoid additional health risks. If these research efforts are to be effective, they must involve a broad spectrum of research scientists, from epidemiologists and clinicians to environmental engineers and community planners. Such efforts will also require a broad-based, multi-agency federal program that draws on the strengths of each agency to develop an overall comprehensive research agenda.

2. Public health and health care infrastructure

The term “public health” describes the science of preventing disease, prolonging life, and promoting health, and its application in society, communities, and groups. In contrast, “health care” focuses primarily on the treatment of disease and the protection of mental and physical well-being in individuals through services provided by physicians and other health care professionals. Together, these two fields are tasked with protecting the health of the people of the United States.

Public health agencies exist in most large cities throughout the United States, as well as at the county, state, and federal levels. Public health schools and other training and research institutions contribute to the United States’ total public health infrastructure investment, which is enormous and quite complex. The public health system will play a critical role in the prevention of human disease from climate change. As such, public health agencies should be deeply involved in the research, development, and implementation of adaptation strategies for climate change.Research is urgently needed to understand how climate change will alter our public health needs in the United States, and to develop optimal strategies to meet those needs.

The health care delivery infrastructure in the United States is even more diverse and complex than the public health infrastructure (although there are many overlaps between the two systems). From family doctors in small towns to complex university research hospitals in large cities, health care professionals are the primary source of medical treatment, prenatal and pediatric care, and personal health protection and promotion for people in the United States. But this infrastructure is also vulnerable to climate change in several important ways. Disasters can severely disrupt the delivery of health care, with long-term effects.29 Climate change may cause changes in the number of patients in some areas and the spectrum of diseases they experience. The type of advice given to patients with chronic conditions and the infrastructure to support them may need to be adapted to protect against climate-induced changes that may make these individuals more vulnerable. There is currently limited research to guide these types of decisions.

The public health community is in the early stages of developing modeling skills and capacity with respect to climate change, particularly for combining climate models with ecological and other health outcome models for use in projecting disease dynamics under different climate scenarios. To understand these dynamics, a sustainable monitoring infrastructure that integrates human and ecological health (terrestrial, marine, aquatic) is critical. While the public health community has developed considerable expertise in behavioral science and health education, this expertise has not yet been applied to the most serious issues related to climate change.

Sea level rise, coastal erosion, and population displacement will pose challenges to public health infrastructure that has been constructed over a period of hundreds of years. Disruption of coastal routes and ports by sea level rise will pose additional challenges to health care delivery and food distribution. It is doubtful that transportation infrastructure will be able to adapt quickly to the large population shifts that will occur in response to changes in rainfall patterns. Displaced populations will require sewer and water resources in new locations. Sea level rise may directly threaten sewer and water resources in coastal locations.

3. Capabilities and skills needed

Many existing skills used in public health and health care are well established and applicable to dealing with the health impacts of climate change, but new skills will also be needed. Skills used in some types of disease surveillance are well established. The skills and methods needed to integrate current and future surveillance activities and retrospective datasets with weather and climate information are less well established. Understanding of how to conceptualise and conduct epidemiological analysis using weather and climate as exposures is also rudimentary. Methods and skills to combine spatial epidemiology with ecological approaches are also lacking. The capacity to translate vulnerability mapping and health impact assessments (HIAs) into behaviour change and effective public health actions is desperately needed.

Greater emphasis must be placed on developing and sustaining interdisciplinary and inter-institutional collaborations, as well as ensuring that the established resources and expertise of all relevant disciplines, including climate science, modeling, environmental science, risk assessment, public health, and communication and education, are applied to these serious problems. Many additional disciplines, including ecology, social science, economics, geography, behavioral psychology, and others, will need to play important roles in climate and health decision making.

4. Communication and education

Other areas where public health professionals can make strong contributions to efforts to address the effects of climate change are communication and education. Public health educators have a strong history of promoting health and well-being by educating individuals and communities about healthy behaviors and disease prevention or management. Those same skills are critical to helping raise awareness of the potential impacts of climate change and to translate scientific research and other technical data into reliable and accessible information for the public to use in making informed decisions that will protect their health and the environment.

Recent studies show that the majority of people living in the United States now believe that climate change is a real and serious threat caused by human activity. However, research is still needed to determine how to effectively educate and organize the public to respond. This is complicated by recent research showing that different audiences within the American public respond to the issue of climate change in their own distinct ways. Research is needed that will assist climate change communicators and educators in tailoring their messages and attitudes to most appropriately and effectively reach and assimilate each individual audience.

In addition to the general public, other audiences – who have their own cultures and means of obtaining information – also require effective communication on climate change issues. Stakeholders such as natural resource managers, policy makers, infrastructure planners, health care providers, and others also need access to reliable and timely climate change information to inform their decision making.

Protecting human health is an issue that crosses institutional, scientific, and political boundaries. In the United States, no single institution at the local, regional, or federal level can fully protect public health without collaboration with other entities. Moreover, no single scientific field is capable of undertaking all aspects of the research needed to understand the human health consequences of global climate change; such an effort would require a broad-based, interdisciplinary research portfolio. And in our global society, the highly integrated activities of individuals around the world mean that no single country can be solely responsible for addressing the health impacts of global climate change. Through the process of developing this white paper, it became increasingly clear that identifying the research needs; mobilizing and creating the expertise, resources, tools, and technologies to address them; and translating these efforts into solutions that will enable human adaptation to our changing environment while protecting public health will require collaboration on an unprecedented scale. Such collaboration should build on the strengths and capabilities of the individual organizations in such a way as to maximize the group’s efforts toward these shared goals.

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