Knowledge of exposure is key to predicting, preventing, and reducing environmental and human health risks. A robust exposure science is necessary to support policy decisions for managing potentially harmful exposures without adversely affecting economic activities, personal liberties, and the health of people. The need for exposure science extends beyond policy considerations, however, and includes societal goals related to population health, economic security, and human well-being. This chapter addresses the demands for exposure science that the committee’s proposed vision will help to meet. The committee’s vision will help transform exposure science into a more forward-looking discipline that supports universal exposure surveillance and integrated predictive systems that facilitate early detection of and even anticipate harmful exposures.
The committee’s vision (Chapter 2) arises in part from multiple and complex scientific, societal, commercial, and policy demands. The committee did not attempt to develop an exhaustive list of those demands but rather selected examples to illustrate their nature and their importance in shaping research needs for exposure science in the 21st century. This chapter builds on the concepts and terminology in Chapter 1 and the applications of exposure science in Chapter 3. It sets the stage for Chapter 5, which identifies scientific and technologic advancements needed to support the committee’s vision.
The committee broadly explored research-based and decision-based activities to identify emerging needs for exposure information. This exploration reveals that the demand for exposure information is growing. One example of this is the knowledge gap resulting from the introduction of thousands of new chemicals into the market each year. The U.S. Toxic Substances Control Act and the Green Chemistry Initiative of the California Department of Toxic Substances Control (CA DTSC 2008) demonstrate that the rate of introduction of new substances exceeds our ability to design and conduct exposure assessments of these new chemicals and their mixtures that enter the market. Other examples
of emerging demands for exposure information are EPA’s Premanufacturing Notice requirements and the European Union’s program for the Registration, Evaluation, Authorization and Restriction of Chemicals. The industries that market chemicals and the government agencies that regulate them need more and better exposure information to conduct screening and regulatory assessments.
Another example is the increasing need to address long-term health effects of low-level exposures to chemical, biologic, and physical stressors over years or decades, such as low-level radiation exposure. A dearth of exposure data contributed to uncertainty in communicating the radiation risk posed by the Fukushima incident in Japan to policy-makers and the public. Previous opportunities to reduce uncertainties through the collection of more and better exposure data have been missed, including opportunities in the aftermath of the Soviet Union’s April 1986 Chernobyl nuclear incident, which spewed radionuclides over a large swath of Europe (Normile 2011). There were few systematic or sustained applications of exposure-science techniques in the collection of radiation-exposure data at Chernobyl (UNSCEAR 2011).
Growing efforts to collect, organize, and evaluate medical-surveillance data in the absence of corresponding efforts to assemble, evaluate, and track exposure data present another example of the need for data. The paucity of exposure data has been observed repeatedly—in the followup of health effects in veterans of the Gulf War (IOM 2000), in the Centers for Disease Control and Prevention (CDC) Health Tracking Program (CDC 2011a), and in the monitoring of the health of volunteers and professionals after exposures to the 2010 Gulf Oil Spill (IOM 2010; King and Gibbons 2011).
The committee defined the complex and overlapping needs for exposure information in four broad categories: health and environmental science, market, societal, and policy and regulatory (illustrated schematically in Figure 4-1). Health and environmental sciences require reliable quantitative data on human and ecosystem exposures. Market demands require the identification and control of exposures resulting from the manufacture, distribution, and sale of products and the provision of services (for example, energy, transportation, and health care). Societal demands arise from the aspirations of individuals and communities—relying on an array of health, safety, and sustainability information—for example, to maintain local environments, personal health, the health of workers who make consumables, and the health of the global environment. Policy-makers drive the need for exposure science when they require knowledge to inform their actions—particularly the setting of policies directed at mitigating environmental risks and avoiding hazards in cost-effective ways. Policy-makers need to establish a balance among the different science (health), market, and societal demands as they establish regulations and set budgetary priorities. The remainder of this chapter explores the four categories of needs for exposure science information. The committee recognizes that many of these demands can conflict. For example, individuals and communities may have different goals
and aspirations with respect to research and policies to maintain the environment, the health of individuals, and communities. Similarly, policy makers and regulatory agencies often have different and even competing goals, and each will be interested in exposure studies that support their particular perspectives. The goal is to explore the various demands, recognizing the potential for competing and conflicting demands.
The need to protect human health has been and will continue to be an important demand for exposure information (NRC 2009a). Accurate assessment of human exposures is a critical component of environmental health research (McKone et al. 2009). Air pollution epidemiology, risk assessment, health tracking, and accountability assessments are examples of health research studies that require but often lack adequate exposure information (McKone et al. 2009). The expanding number of environmental factors that are or will be the focus of health research creates a continuing demand for exposure information. In many health studies the lack of accurate exposure information has led to the use of questionnaires and qualitative assessments in place of more robust quantitative observations.
Demand for health and environmental science information includes the need for more and improved data on broad issues, such as direct stressor—target relationships—for example, air pollution and health and the multiple, complex, and sometimes indirect linkages among environmental exposures and ecosystems, water and land resources, and the built environment. Demands for expo-
sure information also arise from specific health or environmental issues—for example, a rise in autism, asthma, or childhood brain cancer; reproductive failure in specific wildlife populations; or deterioration of popular local habitats. There is also a need to integrate health and ecologic sciences to support a more harmonized framework for assessing the fate and effects of industrially produced and naturally occurring pollutants. Protecting human health and ecosystem integrity requires long-term and spatially and temporally resolved tracking of multiple stressors. For humans, that type of tracking has been conceptualized as the “exposome”, defined as collective exposures from conception on (Wild 2005, 2012). An analogous ecologic-science approach is the National Ecological Observatory Network (NEON)—a continental-scale research instrument proposed by the National Science Foundation (NSF) to provide a nationally networked research, communication, and informatics infrastructure for biologic systems (NEON 2011)—intended to assess the direct effects and feedbacks between environmental change and biologic processes. A similar NSF program, the Long Term Ecological Research network, has been in operation since 1980 (LTER 2012).
Environmental exposures contribute substantially to human health risks, accounting for a greater fraction of risk than genetic variation (Rappaport and Smith 2010). New analytic capabilities are needed for environmental surveillance and biomonitoring and for linking biomarkers to stressors on the basis of pharmacokinetic and pharmacodynamic models (Sohn et al. 2004; Clewell et al. 2008).
With regard to the influence of environmental exposures on health, direct cause—effect relationships are sometimes apparent, as in the cases of radiation from nuclear weapons in Japan; dioxin in Seveso, Italy; and methyl isocyanate in Bhopal, India. Such relationships can be evident even if there is a substantial lag in the development of health effects, as in the 10- to 50-year delay in development of mesothelioma from asbestos exposure.
More commonly, however, exposure—effect relationships are difficult to establish because of other variables. For example, studies of cancer risk in migrants show that environmental factors can cause large increases in risk (see Ziegler et al. 1993). The increase in risk is attributed to lifestyle differences, such as differences in air and water, food, pharmaceuticals, and many household and occupational exposures. Effective monitoring methods, such as CDC’s National Health and Nutrition Examination Survey (NHANES), directly reveal such health changes as the rise in obesity. An ability to link those changes rapidly to specific exposures—for example, endocrine-disrupting chemicals (Heindel 2003), diet, and urban patterns—requires continuing exposure assessment. The need for innovative and cost-effective means of separating and measuring specific exposures constitutes an important demand for exposure science.
Scientific advances in epigenomic research (the study of epigenetic modification at a level much larger than a single gene) have revealed long-term effects of early-life exposures on modification of DNA-methylation patterns (Jirtle and Skinner 2007). Relevant exposures and vulnerable life stages are beginning to be understood, but preliminary results illustrate the need for better exposure data for assessing long-term disease risks. That need is underscored by concern about transgenerational risks posed by fetal exposures, including those during ovarian-cell development, which can affect health outcomes in later generations (Skinner et al. 2010). These types of observations suggest the opportunity for novel approaches to translate internal markers into measures of exposure at critical life stages. To achieve this, scientists need to quantify current exposures and preserve the data in forms that permit them to be used in the future to elucidate transgenerational risks posed by particular exposures.
Increasing use of burden of disease metrics (such as disability adjusted life years [DALYs]) and comparative risk assessment covering a wide array of risk factors, including chemical exposures, diet, and lifestyle, to inform policy decisions demands better and more consistent methods of characterizing diverse exposures in large populations. The problem that arises from this demand is the need to provide measures of environmental exposures that are consistent in statistical and causal terms with measures used to characterize exposures to nonenvironmental risk factors—such as smoking, unsafe sex, and micronutrient deficiencies. Consistent measures of both environmental and nonenvironmental exposures are needed if meaningful policy comparisons are to be made.
There are growing demands for comprehensive information on global, regional, and local environmental problems. Improvements in air and water quality, mostly in developed countries, have been made possible by advances in science and technology. Those improvements will provide a foundation for addressing future demands stemming from growing populations and shrinking resources.
Over the last 2 decades, emissions from energy use in transportation, power generation, industry, and households have steadily decreased in developed countries as a result of emission-control strategies (HEI 2010; EPA 2011a,b; NRC 2010). This has contributed to decreased ambient concentrations of particulate and gaseous air pollutants in many cities, and the effects of transported emissions from other states and countries have become important contributors to total exposures. Those changes drive new needs to monitor fluctuations in ambient air pollutants in space and time, link them to mitigation strategies, and assess health benefits of reducing human exposures. That will
require development and validation of spatiotemporal exposure models that will use data on land use, human activity, housing characteristics, atmospheric concentrations, and personal monitoring. The models need to be specific to different populations, especially populations that are particularly susceptible, such as children and people who have pulmonary and cardiovascular diseases.
Water-quality and water-quality impact assessments have changed substantially over the last several decades with a greater focus on understanding the complex interactions among human populations and water supplies. This focus has created a growing demand for water-pathway exposure assessments. The number and quantities of new chemicals and materials (such as nanomaterials) now found in waste streams far exceed our capacity to monitor them (Kim et al. 2010; Nowack 2010). An ongoing need is to evaluate and limit adverse water-quality effects on aquifers, waterways, forests, and agricultural lands. Improved data on regional and global distribution of persistent chemicals of the types monitored in air-quality studies are needed to address these critical issues. In addition, although cumulative effects of mixtures are largely unknown, there is concern that global accumulations of contaminant mixtures may result in unexpected long-term effects on human and ecologic targets and on the water resources themselves (Macdonald et al. 2000; Woodruff et al. 2011).
Global Climate Change
Global climate change is expected to bring increasingly frequent extreme weather and local environmental changes that have the potential to affect human health, ecologic health, and key resources in several direct and indirect ways (Patz et al. 2007; NRC 2009a; USGCRP 2009). The effects will include those from increased temperature, such as acute and chronic health effects; those from extreme weather, such as physical injuries and drownings, structural collapses, and declines in habitability due to mold and other kinds of contamination; and indirect effects, such as shortages of clean water and increasing concentrations of contaminants due to drought (Frumkin et al. 2008). The National Research Council report on global climate change and human health (NRC 2009a) and a U.S. Council on Environmental Quality Climate Change Adaptation Task Force report (CEQ 2010) addressed recommendations for protecting against those effects. Global climate change will bring new needs for exposure science to examine the effects of climate changes on exposures to new and altered chemical, physical, and biologic stressors. Programs to address climate change and health have been established in CDC (CDC 2011b) and the National Institute for Environmental Health Sciences (NIEHS 2011). Those programs are seeking more input from the exposure-science community; see, for example, the CDC national
conversation with its emphasis on public health and chemical exposures (Brown 2011; CDC 2011c).
The production and use of energy emit pollutants that have been linked to diseases (IIASA 2011) through exposure in the ambient environment (for example, to power-plant emissions) (NRC 2010) and in the indoor environment (for example, to cooking and heating emissions) (Smith et al. 2004). NRC (2010) reported that the quantifiable public-health costs of all energy production, distribution, and use in 2005 totaled $120 billion and were due mostly to criteria air pollutants. Of that amount, $62 billion was attributable to electricity (mainly coal) and about $56 billion to transportation; the remainder was attributable to process heat (for example, industrial boilers) and comfort control (for example, home or commercial-building heating and air-conditioning systems). There are expected to be increases in energy use, but an additional demand for exposure science will occur as a result of transitions from one energy source to another. Energy sources have different effects throughout the use chain (or fuel life cycle), from resource capture through energy production to conversion, distribution, and end use. Because the full burden of extant energy systems has not been adequately characterized (IIASA 2011), there is no appropriate baseline against which to compare the relative benefits of new systems. As world leaders consider options for changing the portfolio of future energy sources, there is growing demand for assessments of effects associated with the various options, including pollutant exposures, and a need to develop strategies to minimize the effects.
Sustainability describes both a process to ensure and a goal of ensuring long-term human well-being and ecologic health (NRC 2011). All technologies have benefits and effects, and an important aspect of long-term sustainability is that technologies achieve an overall balance. Increasing use of technology assessment can be expected to avoid strategic errors that could derail a promising technology and improve policy decisions to avoid long-term adverse effects. Life-cycle assessment of all stages of a process—including-raw material extraction, manufacturing, distribution, use, and disposal—is an accepted approach to evaluating resource consumption and resulting pollution (Guinée et al. 2010). Such analysis is critical for supporting decision-making (Guinée and Heijungs 1993) to ensure sustainability of the environment and resources and to assess health and ecologic effects. NRC (2011) recommends that the Environmental Protection Agency (EPA) develop a “sustainability toolbox” that collectively makes it possible to analyze present and future consequences of alternative decision options on the full array of social, environmental, and economic indicators.
Because of increasing demands for sustainability metrics, an associated demand for exposure-science surveillance and for predictive tools to support life-cycle analysis can be anticipated (see, for example, the USEtox model [USEtox.org 2009]).
Industries and investors want to limit their liability for health and environmental damages and minimize regulatory oversight, and the rapid increase in technologic applications in commerce has created market demands for exposure science that often correspond with demands for information on health and the environment. For example, industries and investors use electronic media as a means of promoting and assessing consumption of their products, considering profitability, regulations, and liability. Organizations and Web sites provide health and environmental information and product scores or rankings of a wide variety of consumer products (for example, GoodGuide 2011). Social networks provide tools for building and exchanging information about the health, environmental, and societal effects of consumer products. Organizations, activities, and tools encourage consumers to consider alternative products and behaviors that can reduce such effects. Consequently, market demands for exposure science include the need for better and more extensive insight into how human activities, including consumption habits, contribute to pollutant emissions and how the emissions contribute to human and ecologic exposures.
Growth in Consumption and Demand for Sophisticated Consumer Products
The increase in global, national, and individual purchases of consumer products places a substantial burden on environmental resources (NRC 2011) and could continue to for decades before stabilization at a sustainable level (Hertwich 2005). Many factors affect that burden, such as increased population, increased personal wealth, and reductions in the useful lifetime of consumer products. Technologic advances have fueled an expectation for improved products, and that expectation contributes to their relatively short lifetimes (for example, mobile telephones, video players, and computers). New products with enhanced properties also lead to replacement of well-functioning equivalent products (for example, more efficient light bulbs or programmable appliances replace existing light bulbs or appliances). Studies of trends in consumer products show that the stability and durability of products have important roles in exposure potential (Hertwich 2005). Stable and durable products resist degradation and contribute less to emissions during their lifetime, but their disposal can be problematic. Information on exposure potential of new products is needed for evaluation of long-term health footprints of exposures and associated risks. There is also a need for exposure data to guide policy in the development of
short-lived products and new products designed to generate premature product replacement. Consumers can play an increasing role by demanding information on the effects of products on the climate, resources, and health—including considerations about exposures across the life-cycle of products.
Exposure science provides critical input for ensuring the sustainability and safety of the food supply. With increasing population growth and internationalization of the food supply, there is expected to be an increasing demand for exposure science (Schmidhuber and Shetty 2005). Demographics of health and disease suggest that diet is a major source of environmental exposures (Ames 1983; Willett 2002), and the increasing globalization and consolidation of food-distribution networks have created a potential for rapid, widespread dissemination of contaminated products (Regattieri al. 2007). In light of economic, political, and nutritional advantages of local food production, that has led to programs to reverse trends in the globalization of the food supply. The competing trend toward globalization vs localization will demand an expansion of exposure-surveillance structures to manage and monitor the changing array of agrarian practices and their influence on environmental quality (NRC 2002). The far-reaching effects of the changes will require a critical role for exposure science to support evaluation and development of policies.
Green chemistry or, more broadly, green commerce includes the design of products and processes with a focus on sustainability with regard to resource consumption and energy use, often accompanied by an effort to limit the human and ecologic health footprint (CA DTSC 2008).1 Green commerce encounters the same challenges as other businesses as practical considerations of profitability often require use of more available resources according to supply and demand; that is, as the feedstock diminishes and prices rise, manufacturers seek alternatives. Small businesses are especially vulnerable to such variations and could benefit from publicly accessible exposure data. New approaches in exposure assessment and information dissemination are critical for decreasing the pollution footprint of products and services while allowing for adaptive responses by free enterprise.
1EPA describes green-chemistry goals as including source reduction and the prevention of chemical hazards, such as through the use of feedstocks and reagents that are less hazardous to human health and the environment, the design of syntheses and other processes to be less energy-intensive and material-intensive, the use of feedstocks derived from annually renewable resources or from abundant waste, the design of chemical products for increased and easier reuse or recycling, treatment to render chemicals less hazardous, and proper disposal of chemicals (EPA 2011a).
The health, environmental, and market demands discussed above are direct reflections of a society and the complex needs and desires of its constituents. Over the last century, there has been a dramatic rise in world population combined with an increase in urbanization, and the result has been profound changes in not only where people live but how they live. The evolution of the U.S. and world populations from primarily agrarian communities to megacities and sprawling suburbs has led to societal (and scientific) questions about effects on human health and well-being and on ecosystems. Concurrently, there have been dramatic changes in what is eaten and how, how and how often people travel, and how technologies are used for communication. Major societal demands for exposure science include the understanding and assessment of the effects of urbanization and urban land-use modifications and of changes in manufacturing, consumption, and transportation.
Urbanization and Land-Use Changes
Projections of changes in urbanization and land use indicate both increased need for and more systematic means of exposure surveillance in the coming decades. The density of economic activity increases with urban population density (World Bank 2009); half the world population now lives in cities, and the UN projects that about 75% will live in cities by 2050 (UN 2008). The growth of suburban areas is especially pronounced in North America, where cities are highly energy-intensive and transportation is dominated by automobiles, but similar patterns of suburbanization are evident in many other places. Increased automobile use contributes to environmental problems—increased air pollution, storm-water runoff due to impervious surfaces, and higher intake of pollutants when roadways are near residences (Hough 1995; Frumkin et al. 2004; Jerrett et al. 2010).
There is a need for a systematic process to evaluate exposures associated with different layouts and designs of urban areas to guide planning to optimize urban and suburban structures with consideration of exposures and health (Marshall et al. 2005). The factors that have increased exposures appear to be growing as many previously poor nations undergo rapid economic transformations and higher economic growth (Wang et al. 2005). The complexity of those driving forces and the need to protect human and ecosystem health can be met with increased and more systematic exposure surveillance in the coming decades of the 21st century.
Societal Issues in Manufacturing and Transportation
Economic changes in the developing and developed worlds have altered where and how products are produced and distributed. There is an expectation
that consumer goods are to be convenient, mobile, and accessible. Rapid changes in style and capacity (for example, of telephones) lead to quick product turnover, which results in a growing waste-management challenge. The production of steel, electronics, and many consumer products is moving to Asia, leaving the large industrial regions of Europe and North America seeking “rebirth” and risking decay and abandonment. Transportation systems are facing growing demands. Web-based purchasing creates a growing need for home-delivery networks. Both tourists and business travelers are taking more and longer airline flights. Those dramatic changes in the world of manufacturing and distribution give rise to concerns and questions about how they will affect humans and the environment, motivating the acquisition of information on changing exposure patterns.
Other Societal Concerns
There are many other societal concerns that demand accurate and more comprehensive exposure information. For example exposures to biologic stressors in water supplies and food. In urban areas there are significant concerns about exposure to noise, which is often only well monitored and researched near “hot spots” such as airports and major roadways. Mixed exposures among chemical, physical, and biologic stressors are also of concern, but difficult to track and evaluate (WHO 2012).
For example, studies in the European Union reveal that excessive noise can harm human health and interfere with people’s daily activities. It can disturb sleep, cause cardiovascular and psychologic stress, reduce performance, and cause changes in behavior (WHO 2012). Addressing these health concerns requires more reliable monitoring of noise levels over a broad range of geographic areas.
Exposure science used in policy-making can provide information to support environmental protection, resource management, chemical regulation, manufacturing goals, and health, energy, climate, and economic policies. The policy and regulatory demands for exposure science are unique in their link to governments. Policy-makers need to make tradeoffs among a broad array of outcome options. For example, they use exposure information to address conflicting societal, commercial, and scientific considerations, and they use it to monitor the health and environmental benefits of regulations (NRC 2007). Policy-makers have the capacity to use exposure information to inform and motivate activities or to address the reluctance of other policy-making entities or others to take action. For example, robust exposure science is a key asset in an era of limited resources. It is particularly useful for an agency that has responsibility for promoting the health and sustainability of communities in separating
perceived effects and benefits based on anecdotal evidence from those which are large and well documented, steering limited resources away from ineffective interventions. (The exposure metric called “Intake Fraction” is an example of a tool that might be used in regulations to improve health protection, see Chapter 1 discussion.)
Policy-makers and regulators have a demand for exposure information to inform the concerned public about products and exposures, to establish emergency preparedness and response, to set priorities for research and regulation among chemicals or stressors of concern, and to allocate funding and set policies for managing knowledge-integration systems to address health and ecosystem protection. Adding to the policy demands for exposure science are the community demands for access to technologies that allows community members to work with scientists, to generate their own exposure data, and to more effectively participate in the environmental policy and regulatory processes (Brown et al. 2012).
Health and environmental, market, societal, and policy and regulatory demands are creating increased needs for exposure science in the 21st century. Meeting those needs will require a scientific framework that supports the development of technologies to collect, analyze, and integrate exposure-science data. The remainder of this report addresses the framework for building the capacity to meet the demands for exposure science in the 21st century.
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