Human Health Perspective On Climate Change

Climate change threatens human health, affecting all sectors of society at the domestic and global levels. The environmental consequences of climate change, both those already observed and those that are predicted, such as sea level rise, flooding and droughts resulting from changes in precipitation, heat waves, more intense hurricanes and storms, and poor air quality, will affect human health directly and indirectly. Addressing the effects of climate change on human health is particularly challenging because both the surrounding environment and the decisions people make affect health. For example, an increase in the frequency and severity of regional heat waves – potential consequences of climate change – has the potential to harm many people. Some adverse health effects could potentially be avoided if vulnerable populations such as children and the elderly are identified and ensured access to preventive measures such as air conditioning as a result of decisions taken before heat waves occur. This is a simplified illustration; in real-life situations many other factors, including biological susceptibility, socioeconomic status, cultural competence, and the built environment, also play a role in determining vulnerability. In a world of myriad “what if” scenarios related to climate change, the uncertainty of predicting environmental change and human decisions makes it very complex to create wise health policies for the future. The need for solid science to base such policies on has become more important than ever.

This was an issue that required a deeper understanding of its complexity. With the aim of developing a white paper on relevant federal research and science needs, as well as some research on mitigation and adaptation strategies, an ad hoc Interagency Working Group on Climate Change and Health (IWGCCH) was assembled. Relevant examples of mitigation and adaptation research needs could be identified. However, a comprehensive discussion of them could not be pursued. These research and science needs broadly include basic and applied science, technological innovation and capabilities, public health infrastructure, communication, and education. The potential structure of the federal climate change and health research agenda and the use of scientific research results for applications and decision making are also considered. The purpose of this paper is to identify research critical to understanding the impact of climate change on human health so that we can mitigate and adapt to the environmental impacts of climate change in the healthiest and most efficient ways. Although the group acknowledges the global dimensions of the impacts of climate change on human health, this paper will focus primarily on the US situation.

This report is organized around 11 broad human health categories potentially affected by climate change. The categories are arranged alphabetically, and no priority—for example, probability of occurrence, severity of impacts, or depth of current knowledge—is implied. Each category is divided into sections that introduce the topic, explain its relationship to climate change, and identify basic and applied research needs for that category, as well as intersecting issues where relevant. Most investigations of climate change and health have relied on environmental and ecological effects to estimate potential human health impacts; IWGCCH deliberately chose to emphasize the need for research on human health consequences over environmental impacts for this reason: this approach highlights the direct links between climate change and federal research priorities that are often disease- or outcome-specific, and focuses on human health consequences. A holistic approach enables the exploration of climate change-related health impacts. We recognize that the health outcomes identified in this document are not exhaustive, and because so many climate change impacts are possible, some of the research needs enumerated may be speculative. As more information becomes available, new research needs may be identified and others may be rejected, but our intention is for this report to serve as a baseline discussion from which agencies can move forward.

Asthma, respiratory allergies and airway diseases—Respiratory allergies and diseases may become more prevalent due to increased exposure to pollen (due to a changed growing season), mold (due to excessive or more frequent rainfall), air pollution and aerosolized marine toxins (from increased temperatures, coastal runoff and humidity) and dust (from drought). Mitigation and adaptation can substantially reduce these risks. Research should address the relationship between climate change and the composition of the air pollutant mixture (for example, how altered pollen counts and other effects of climate change affect asthma severity) to create models to identify populations at risk. Such tools support the use of science in understanding disease risks and, as such, are an integral part of developing effective risk communications and targeting messages to vulnerable populations.

Cancer- Many of the direct effects of climate change on cancer risk, such as increases in the duration and intensity of ultraviolet (UV) radiation, are well understood; however, the potential impact of changes in climate on exposure pathways to chemicals and toxins requires further study. Science on the impact of mitigation and adaptation measures on cancer incidence should be tested so that it can create space for implementing effective strategies. Research will serve to inform the benefits of alternative fuels, new batteries and voltaic cells, as well as the harmful hazards posed by exposure to certain materials and their byproducts. A better understanding of the effects of climate change on the capacity of ocean and coastal systems to provide cancer therapeutic agents and other health-enhancing products is needed.

Heart disease and stroke – Climate change may exacerbate existing heart disease by increasing heat stress, increasing the body burden of airborne particles, and altering the distribution of zoonotic vectors that cause infectious diseases associated with heart disease. There is a need for science that addresses the cardiovascular effects of high temperatures, heat waves, extreme weather, and changes in air quality on health, and this new information should be applied to the development of health risk assessment models, early warning systems, health communication strategies targeting vulnerable populations, land use decisions, and strategies to meet climate change-related air quality goals. In some areas, cardiovascular and stroke risks resulting from climate change could be offset by reductions in air pollution due to climate change mitigation.

Foodborne disease and nutrition—Climate change may be associated with staple food shortages, malnutrition, and food contamination (from chemical contaminants, biotoxins, and pathogenic microbes in seafood and crops by pesticides). Science research needs in this area include a better understanding of how changes in agriculture and fisheries may affect food availability and nutrition, improved surveillance for disease-causing agents, and identification and mapping of complex food webs and sentinel species that may be vulnerable to climate change. This research can be used to prepare the public health and health care sectors for new diseases, changing surveillance needs, and increased incidence of disease, as well as the development of more effective outreach to affected communities.

Heat-related morbidity and mortality—Heat-related illness and deaths are likely to increase in response to climate change, but aggressive public health interventions such as heat wave response plans and health alert warning systems can reduce morbidity and mortality. Additional science should be focused on developing and expanding these tools across different geographic regions, particularly on defining environmental risk factors, identifying vulnerable populations, and developing effective risk communication and prevention strategies.

Human developmental effects—Two potential consequences of climate change will affect normal human development: malnutrition—particularly during the prenatal period and early childhood as a result of decreased food supply, and exposure to toxic pollutants and biotoxins—as a result of extreme weather events, increased pesticide use for food production, and increased harmful algal blooms in recreational areas. Research should examine the relationship between human development and adaptation to climate change, such as agricultural and fisheries changes that may affect food availability, increased pesticide use to control disease vector range expansion, and prevention of leaching from toxic waste sites in floodwaters during extreme weather events, in order to prevent detrimental developmental consequences.

Mental health and stress-related disorders—By causing or contributing to extreme weather events, climate change can result in geographic displacement of populations, property damage, loss of loved ones, and long-term stress, all of which can negatively impact mental health. Research needs include identifying key mental health impacts and vulnerable populations and developing migration monitoring networks to help ensure the availability of appropriate health care support.

Neurological diseases and disorders—Climate change, as well as efforts to mitigate and adapt to it, may increase the number of neurological diseases and disorders in humans. Research in this area should focus on identifying vulnerable populations and understanding the mechanisms and effects of human exposure to neurological hazards such as biotoxins (from harmful algae blooms), metals (found in new battery technologies and compact fluorescent lights), and pesticides (used in response to changes in agriculture), as well as the potentially serious effects of malnutrition and stress.

Vectorborne and zoonotic diseases – Disease risk may increase as a result of climate change due to associated expansions in vector ranges, shortening of pathogen incubation periods, and disruption and relocation of large human populations. Research should enhance existing pathogen/vector control infrastructure, including vector and host identification; integrate humans with terrestrial and aquatic animal health surveillance systems; incorporate ecological studies to provide better predictive models; and improve risk communication and prevention strategies.

Waterborne diseases – Increases in water temperature, rainfall frequency and severity, evaporation-transpiration rates, and changes in coastal ecosystem health may increase the incidence of water pollution with harmful pathogens and chemicals, resulting in increased human exposure. Research should focus on understanding where changes in water flow will occur, how water will interact with sewage in surface and underground water supplies as well as drinking water distribution systems, which food sources may be contaminated, and how to better predict and prevent human exposure to waterborne and ocean-related pathogens and biotoxins.

Weather-related morbidity and mortality – Increases in the incidence and intensity of extreme weather events such as hurricanes, floods, droughts, and wildfires can adversely affect people’s health during or immediately after the event. Research aimed at improving the capabilities of health care and emergency services to address disaster planning and management is needed to ensure that risks are understood and optimal strategies are identified, communicated, and implemented.

In addition to the research needs identified in the individual research categories, there are also issues relevant to preventing or averting the many potential health impacts of climate change, including identifying susceptible, vulnerable, and displaced populations; enhancing public health and health care infrastructure; developing capacity and skills in modeling and prediction; and improving risk communication and public health education. Such research will lead to more effective early warning systems and greater public awareness of the health risk to an individual or community from climate change, which should translate into more successful mitigation and adaptation strategies. For example, health communication research is needed to properly implement health warning alert systems for extreme heat events and air pollution that particularly affect people with existing conditions such as heart disease. Such a risk communication pilot project can demonstrate communication practices that are effective across multiple sectors, and contribute to a comprehensive strategy for addressing multiple health risks simultaneously.

Other tools are needed and should be applied across a number of categories to close knowledge gaps, including predictive models to improve forecasting and prevention, assessment of the vulnerability of health care and public health systems and infrastructure, and health impact assessments. Trans-disciplinary development will help ensure tools such as improved baseline monitoring that will be more widely applicable, and thus more efficient and cost-effective than currently available tools. Indeed, many of the science needs identified will require inter-disciplinary responses. For example, studying how heat waves alter ambient air pollution and the resulting combined effects of heat and pollution on human illness and mortality will require expertise in atmospheric chemistry, climate patterns, environmental health, epidemiology, medicine, and other science areas. Given the complexity of science needs and the potential overlap of research questions across disciplines, fostering trans-disciplinary collaborations between and within federal agencies would be a logical approach and should be a high priority.

Recently, the National Research Council released a report outlining how federal research and science can be improved to support decision and policy making on climate change and human health. Specifically, the report calls for a more complete inventory of the health effects of climate change, increasing the power of prediction tools, enhancing the integration of climate observation networks with health effects monitoring tools, and improving interactions between stakeholders and decision makers. IWGCCH conducted this research need assessment with these goals in mind. The next step for federal agencies will be to discuss the findings of this white paper with stakeholders, decision makers, and the public as they work to incorporate and prioritize appropriate research needs into their respective science agendas and collaborative research efforts. A coordinated federal approach will bring together the unique skills, capabilities, and missions of different agencies to maximize the potential for discovery of new information and opportunities for success in providing critical information to support responsive and effective decisions on climate change and health.

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