Introduction About Human-Health-Perspectives-On-Climate-Change

Global climate change has become one of the most visible environmental concerns of the 21st century. From images of polar bears and melting ice in Alaska to drought and broken farmland in Africa, images of the ecological effects of climate change have become part of our joint consciousness and inspire concern and discussion about what climate change will ultimately mean to our planet. But rarely are the effects of climate change expressed, visually or otherwise, in terms of the actual and potential cost in human lives and suffering. To date, most climate change research has focused on environmental effects, not health effects. It is clear that climate change threatens human health, but the science and knowledge base about how this happens needs to be improved. One purpose of this document is to identify research gaps to increase understanding of climate change and health. Expanding our understanding of the often indirect, long-term, and complex consequences of climate change for human health is a high priority and challenging research task. Particularly in the developed world, there is a greater perception of the ecological and environmental impacts of climate change than of the impacts on human health. This may be partly due to the fact that images linking climate change and some already evident wildlife and landscape impacts are prevalent, and thus, concern is heightened.

However, there is no doubt that climate change is currently affecting public health through myriad environmental consequences, such as sea level rise, flooding and droughts as a result of changes in rainfall, heat waves, changes in the intensity of hurricanes and storms, and deterioration in air quality, which is projected to continue in the near future. Including just four diseases (cardiovascular disease, malnutrition, diarrhea and malaria), as well as flooding, the World Health Organization (WHO) estimates that 166,000 deaths and nearly 5.5 million disability-adjusted life years (DALYs, a measure of the overall burden of disease) were attributable to climate change in 2000.6 To date, most analyses on climate change and health have focused on diseases that primarily affect people in the developing world, and are, therefore, considered less relevant to more developed countries. However, as the recent pandemic of the H1N1 virus has shown us, diseases do not respect international boundaries. Climate change may be a driver for disease migration, but even so, such diseases do not represent the wide range of possible, or even likely, human health impacts of climate change, nor do they reflect the potential co-benefits of mitigation and adaptation to climate change, some of which may have the greatest impact on the developed world.

For more than 170 years, scientists have been studying the complex relationships among weather, climate, and human health. Since the first attempt at a scientific consensus on climate change nearly four decades ago, 8 scientists have been investigating whether climate is indeed changing as a result of human activity. However, the complex relationships among climate change, the environment, and human health do not represent high priorities for scientific research in the United States, and there are abundant gaps in our understanding of these relationships. Such gaps impair our ability to identify optimal strategies for mitigation and adaptation that will prevent disease and death in current human populations as well as protect the environment and health of future generations. The purpose of this report is to identify key research areas that require further exploration and understanding, and to identify the scientific capabilities that will be needed to adequately address problems that arise in connection with climate, the environment, and human health. The goal is to inform federal agencies with human health or related research missions as they confront these difficult challenges. Research results generated from the needs agenda outlined here will go a long way in informing health decision making and addressing the challenges outlined in the National Research Council report.

Leaders including the Director, National Institute of Environmental Health Sciences (NIEHS); Chief Scientist in the Office of Science Advisor, U.S. Environmental Protection Agency (EPA); Senior Scientist for Coastal Ecology, National Oceanic and Atmospheric Administration (NOAA); and Director, National Center for Environmental Health, Centers for Disease Control and Prevention (CDC), initiated the development of this white paper in February 2009. The Interagency Working Group on Climate Change and Health (IWGCH) was established with representation and participation from a variety of federal agencies, institutions, and other organizations with environmental health or public health mandates. (Participating groups are listed on the Working Group page, page iii of this document). The first activity of this ad hoc group was to review and distill the state of the science on the effects of climate change on human health from the many excellent reviews of climate change already published by groups including the Intergovernmental Panel on Climate Change, the World Health Organization, the U.S. Global Change Research Program, the National Research Council, and others. Most of these reports take a more comprehensive view of the issue of climate change; However, those portions that relate directly to human health impacts provide an important baseline from which this working group can proceed to identify research gaps and needs in this area.

This document does not attempt to provide a comprehensive assessment of the risks associated with climate change and health or strategic planning. Rather it seeks to build on existing knowledge from prior efforts, and advance this knowledge by changing the perspective on climate change impacts from a largely ecological and meteorological basis to one that focuses on the human health consequences of climate change, mitigation, and adaptation. Likewise, this report is intended to inform the federal government as it seeks to focus climate change research on understanding the interactions between climate, human, and environmental systems and supporting societal responses to climate change. As such, it is responsive to the recommendations of some of these reports. The working group drafted this document in consultation with subject matter experts from various agencies, seeking their review and comment throughout the process to provide a concise, credible,and comprehensive discussion.

Climate change directly affects five components of the environment: water, air, weather, oceans, and ecosystems. Changes in rain and other precipitation, changes in temperature, and the melting of summer ice caps are already occurring and will lead to changes in the availability and quality of water across much of the planet over the next 30 years. In the United States, water security, or the reliable availability of water for drinking, agriculture, manufacturing, and myriad other uses, is becoming a serious issue. This is particularly true in the western part of the country, where water scarcity has increased due to decreased mountain snowfall as temperatures rise, and in the South, where severe droughts have become more common in recent years. Water quality is also affected in many regions, especially coastal areas, due to extreme weather events such as hurricanes and flooding. These same events, often associated with sea level rise and increased storm surges, can cause enormous harm to human communities and alter complex coastal ecosystems with consequences for both water and food quality and supply.

The complex atmospheric chemistry that governs air quality is controlled by heat, humidity, the degree of ultraviolet (UV) radiation, and many other factors. Changes in any of these can directly reduce air quality, especially in urban areas, by increasing air concentrations and human exposure to a variety of toxic air pollutants, including chemicals, fungi, and aeroallergens. In many areas of the country, climate change and weather events such as drought and wildfires will reduce general air quality and increase human exposure to a variety of pollutants, resulting in increased incidence of asthma, heart disease, and other respiratory illnesses.

Some impacts on human health will result from extreme weather events that are expected to become more common in a warming climate. For example, more intense storms and flooding and an increase in wildfires can have widespread health effects as a result of the release of toxic chemicals from landfills, contamination of drinking water with raw sewage as a result of damage to water infrastructure, increased concentrations of air pollutants that are particularly harmful to vulnerable populations such as children, the elderly, and people with asthma or heart disease, and myriad other hazards associated with these events. Extreme heat directly increases the risk of injury, illness, and death, as well as indirectly contributing to mental health and stress-related illnesses.

Global climate change is clearly and profoundly affecting the oceans, which in turn affects human health. Warming ocean waters contribute to increased incidence and severity of toxic algal blooms, changes in aquatic and estuarine food webs and the quality and availability of seafood, and impacts on sentinel aquatic species16. Higher concentrations of carbon dioxide in the atmosphere increase the amount dissolved in the ocean, leading to acidification and disruption of ecosystems. Since a large proportion of the world’s population, including the United States, lives in coastal areas, and many people depend on marine proteins for daily subsistence, the consequences of disturbing delicate ocean and coastal systems will be far-reaching.

Climate changes, including increased heat in some arid and semi-arid parts of the United States, can dramatically alter existing ecosystems, presenting new challenges to agricultural production and coastal ecosystems, with consequences for food quality and availability. Changes in plant habitats can result in reduced availability of grazing land for livestock.17 Climate changes are also directly linked to many insect habitats and disease vectors, and changes in temperature can expand or reshape habitats such that organisms are introduced to new geographic areas or life cycles change, requiring increased pesticide use or use in new areas to achieve the same yields. Global warming is also causing shifts in the ranges of disease vectors that require specific environments to thrive (for example, Lyme disease),18 and increasing the risk and incidence of waterborne, vectorborne, and zoonotic (transferred from animals to humans) diseases in humans.

No existing mitigation strategy or technology can stop climate change that has already occurred. Currently, our ability to reduce the magnitude of climate change that will occur over the next 100 years is dependent on the current composition of the atmosphere as well as what we can prevent from entering and what we are able to remove from the atmosphere in the future.

The major goals of climate change mitigation strategies include alternative fuels and energy conservation, changes in land use patterns, sustainable development of the built environment, and carbon capture and storage.19 Switching from fossil fuels and other greenhouse gas emitting energy sources to clean energy alternatives and the use of carbon capture and storage technologies will slow the rate at which we release greenhouse gases into the environment. Energy conservation and modifications in energy use will also reduce emissions. Land use changes such as preventing deforestation and replanting more trees will help increase natural carbon storage.

Actions to preserve other ecosystem services, such as flood control by protecting wetlands or vector control by preserving biodiversity, can also reduce the severity of problems related to climate change. Finally, changes in building codes, transportation infrastructure, housing density, coastal development, and other urban planning strategies can reduce energy use and thereby mitigate some portion of climate change. Through these changes in human activities and practices, we should be able to limit the magnitude of changes in the planet’s climate, and thus, reduce the negative impacts on human health. Although it is possible that some mitigation strategies may exacerbate known human health stressors or bring unanticipated potential for human harm, many strategies will provide co-benefits, reducing illness and death while also reducing the negative impacts of climate change. For example, reducing harmful air pollutants generally reduces global warming, but it also leads to greater health benefits for people.

Recognizing that there is a broad set of issues related to both potential benefits and potential adverse effects on human health resulting from mitigation and adaptation strategies, IWGCCH did not attempt in this report to outline research needs for mitigation and adaptation in a comprehensive way, nor provide a comprehensive overview of mitigation and adaptation approaches. These issues and their associated research needs will have to be assessed in the context of individual options and strategies. Instead, this report focuses on some broad mitigation and adaptation options currently under development that have the potential to provide great benefits to human health and proposes research needs that can inform decisions related to them, and examples of mitigation and adaptation needs related to some health-related outcome are included in each chapter.

Adapting to or dealing with climate change will become necessary in the United States and around the world. Most adaptation strategies attempt to alter the human environment and reduce the likelihood of disease and death by helping to prevent some of the worst consequences of climate change. The primary environmental factors targeted for adaptation are water security and food security. Given the likely changes in rainfall patterns, temperatures and extreme weather events, adapting the ways we store, treat and use water will be critical to avoid changes in water security. Similarly, food sources – whether they are crops, livestock, marine or freshwater – will be under greater stress in different parts of the United States, and as a nation we need to develop adaptation strategies to ensure our food security. Access to clean water and sufficient safe food are fundamental requirements for human health, so successful adaptation methods that maintain and improve the availability of clean water and healthy food will be critical to avoiding some of the major health impacts of climate change. Adaptation strategies focused on community development and the built environment, transportation and public health infrastructure are also needed.

Through these environmental changes, adverse human health outcomes are likely to increase and, in some rare cases, decrease health outcomes. We have organized these health outcomes into 11 broad categories for discussion. In this report, we provide for each category a brief summary of what is known about the relationship between climate change; mitigation, and adaptation; effects on the risk, incidence, severity, or characteristics of specific diseases or disorders; key research needs and questions that should be addressed; and in some cases, an indication of the specific skills and capabilities that will be needed to facilitate the research. Because factors such as urgency, probability of occurrence, number of people affected, severity of impacts, and economic issues associated with each category are broad, difficult to quantify, and largely beyond the mandate of our individual agencies, we have deliberately chosen not to attempt to prioritize research needs, but rather to provide a body of knowledge to inform federal agencies and the government as a whole, as agencies and other groups set their priorities and agendas in this area. The scope of this analysis is largely limited to examining impacts on the U.S. population, which is the primary constituency of federal agencies, recognizing that most, if not all, of these issues are of global concern and consequence as well as hope that the benefits from this information can be applied to future global collaborations. Similarly, although we attempt to provide some discussion of the training, capabilities, technology, and infrastructure needs that will be necessary to address these important research questions, this is within the context and for the purpose of identifying and applying those resources that exist or are anticipated within our specific federal agencies.

Finally, the health outcome categories, although considered as individual topics, are not isolated but rather interconnected through complex systems within our planet and our own bodies. We have attempted to highlight these relationships wherever possible and when they are of major importance. We have also identified several critical issues that are important to this discussion including susceptible, vulnerable, and displaced populations; public health and health care infrastructure; required capacities and skills; and communication and education to raise awareness of the health impacts of climate change.

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