We are exposed every day to agents that have the potential to affect our health—through the personal products we use, the water we drink, the food we eat, the soil and surfaces we touch, and the air we breathe. Exposure science addresses the intensity and duration of contact of humans or other organisms with those agents (defined as chemical, physical, or biologic stressors)1 and their fate in living systems. Exposure assessment, an application of this field of science, has been instrumental in helping to forecast, prevent, and mitigate exposures that lead to adverse human health or ecologic outcomes; to identify populations that have high exposures; to assess and manage human health and ecosystem risks; and to protect vulnerable and susceptible populations.
Exposure science has applications in public health and ecosystem protection, and in commercial, military, and policy contexts. It is central to tracking chemicals and other stressors that are introduced into global commerce and the environment at increasing rates, often with little information on their hazard potential. Exposure science is increasingly used in homeland security and in the protection of deployed soldiers. Rapid detection of potentially harmful radiation or hazardous chemicals is essential for protecting troops and the general public. The ability to detect chemical contaminants in drinking water at low but biologically relevant concentrations quickly can help to identify emerging health threats, and monitoring of harmful algal blooms and airborne pollen can help to identify health-relevant effects of a changing climate. With regard to policy and regulatory decisions, exposure information is critical in budget-constrained times for assessing the value of proposed public-health actions.
Exposure science has a long history, having evolved from such disciplines as industrial hygiene, radiation protection, and environmental toxicology into a theoretical and practical science that includes development of mathematical models and other tools for examining how individuals and populations come into contact with environmental stressors. Exposure science has played a fundamental role in the development and application of many fields related to
_______________________
1Examples include chemical (toluene), biologic (Mycobacterium tuberculosis), and physical (noise) stressors.
environmental health, including toxicology, epidemiology, and risk assessment. For example, exposure information is critical in the design and interpretation of toxicology studies and is needed in epidemiology studies to compare outcomes in populations that have different exposure levels. Collection of better exposure data can provide more precise information regarding risk estimates and lead to improved public-health and ecosystem protection. For example, exposure science can improve characterization of populationwide exposure distributions, aggregate and cumulative exposures, and high-risk populations. Advancing and promoting exposure science will allow it to have a more effective role in toxicology, epidemiology, and risk assessment and to meet growing needs in environmental regulation, urban and ecosystem planning, and disaster management.
The committee identified emerging needs for exposure information. A central example is the knowledge gap resulting from the introduction of thousands of new chemicals into the market each year. Another example is the increasing need to address health effects of low-level exposures to chemical, biologic, and physical stressors over years or decades. Market demands also require the identification and control of exposures resulting from the manufacture, distribution, and sale of products. Societal demands for exposure data 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, and the global environment.
Recently, a number of activities have highlighted new opportunities for exposure science. For example, increasing collection and evaluation of biomarker data through the Centers for Disease Control and Prevention National Health and Nutrition Examination Survey and other government efforts offer a potential for improving the evaluation of source—exposure and exposure—disease relationships. The development of the “exposome”, which conceptualizes that the totality of environmental exposures (including such factors as diet, stress, drug use, and infection) throughout a person’s life can be identified, offers an intriguing direction for exposure science. And the publication of two recent National Research Council reports—Toxicity Testing in the 21st Century: A Vision and a Strategy (2007) and Science and Decisions: Advancing Risk Assessment (2009)—have substantially advanced conceptual and experimental approaches in companion fields of toxicology and risk assessment while presenting tremendous opportunities for the growth and development of exposure science.
The above activities have been made possible largely by advances in tools and technologies—sensor systems, analytic methods, molecular technologies, computational tools, and bioinformatics—over the last decade, which are providing the potential for exposure data to be more accurate and more comprehensive than was possible in the past. The scientific and technologic advances also provide the potential for the development of an integrated systems approach to exposure science that is more fully coordinated with other fields of environmental health; can address scientific, regulatory, and societal challenges better; can provide exposure information to a larger swath of the population; and can
embrace both human health and ecosystem protection. The availability of the massive quantities of individualized exposure data that will be generated might create ethical challenges and raise issues of privacy protection.
Recognizing the challenges and the need for a prospective examination of exposure science, the U.S. Environmental Protection Agency (EPA) and the National Institute of Environmental Health Sciences (NIEHS) asked the National Research Council to develop a long-range vision and a strategy for implementing the vision over the next 20 years, including development of a unifying conceptual framework for the advancement of exposure science.2 In response to the request, the National Research Council convened the Committee on Human and Environmental Exposure Science in the 21st Century, which prepared this report.
In this summary, the committee presents a roadmap of how technologic innovations and strategic collaborations can move exposure science into the future. It begins with a discussion of a new conceptual framework for exposure science that is broadly applicable and relevant to all exposure media and routes, reflecting the current and expected needs of the field. It then describes scientific and technologic advances in exposure science. The committee next presents its vision for advancing exposure science in the 21st century. Finally, it discusses more broadly the elements needed to realize the vision, including research and tool development, transagency coordination, education, and engagement of a broad stakeholder community that includes government, industry, nongovernment organizations, and communities.
CONCEPTUAL FRAMEWORK
Exposure science can be thought of most simply as the study of stressors, receptors, and their contacts in the context of space and time. For example, ecosystems are receptors for such stressors as mercury, which may cascade from the ecosystem to populations to individuals in the ecosystem because of concentration and accumulation in the food web, which lead to exposure of humans and other species. As the stressor (mercury in this case) is absorbed into the bodies of organisms, it comes into contact with tissues and organs. It is important to recognize that exposure science applies to any level of biologic organization—ecologic, community, or individual—and, at the individual level, encompasses external exposure (outside the person or organism), internal exposure (inside the person or organism), and dose.
To illustrate the scope of exposure science and to embrace a broader view of the role that it plays in human health and ecosystem protection, the committee developed the conceptual framework shown in Figure S-1.
_______________________
2Given the committee’s statement of task, it addressed primarily exposure-science issues related to the U.S. and other developed countries.
Figure S-1 identifies and links the core elements of exposure science: sources of stressors, environmental intensity3 (such as pollutant concentrations), time—activity and behavior, contact of stressors and receptors, and outcomes of the contact. The figure shows the role of upstream human and natural factors in determining which stressors are mobilized and transported to key receptors. (Examples of those factors are choosing whether to use natural gas or diesel buses and choosing whether to pay more for gasoline and drive a car or to take a bus—the choices influence the sources and can influence behavior.) The figure indicates the role of the behavior of receptors and time in modifying contact, depending on environmental intensities that influence exposure. Figure S-1 encapsulates both external and internal environments within the “exposure” box, but indicates that exposure is measured at some boundary between source and receptor. Dose is the amount of material that passes or otherwise has influence across the boundary; comes into contact with the target system, organ, or cell; and produces an outcome. For example, a dose in one tissue, such as the blood, can serve as the exposure of another tissue that the blood perfuses.
SCIENTIFIC AND TECHNOLOGIC ADVANCES
Innovations in science and technology enable advances to be made in exposure science. Numerous state-of-the-art methods and technologies measure exposures, from external concentrations to personal exposures to internal exposures. (Selected technologies considered in relation to the conceptual framework
_______________________
3Intensity is the preferred term because some stressors, such as temperature excesses, cannot be easily measured as concentrations.
are included in Figure S-2.) For example, developments in geographic information science and technologies are leading to rapid adoption of new information from satellites via remote sensing and providing immediate access to data on potential environmental threats. Improved information on physical activity and locations of humans and other species obtained with global positioning systems and related geolocation technologies is increasingly combined with cellular-telephone technologies. Biologic monitoring and sensing increasingly offer the potential to assess internal exposures. In addition, models and information-management tools are needed to manage the massive quantities of data that will be generated and to interpret the complex interactions among receptors and environmental stressors. The convergence of those scientific methods and technologies raises the possibility that in the near future integrated sensing systems will facilitate individual-level exposure assessments in large populations of humans or other species. The various technologies are discussed below.
Tracking Sources, Concentrations, and Receptors with Geographic Information Technologies
Geographic information technologies—remote sensing, global positioning and related locational technologies, and geographic information systems (GIS)—are motivating an emphasis on spatial information in exposure science. They can be used to characterize sources and concentrations and can improve understanding of stressors and receptors when used in concert with other methods and data.
• Remote sensing involves the capture, retrieval, analysis, and display of information on subsurface, surface, and atmospheric conditions that is collected by using satellite, aircraft, or other technologies. Remote sensing is an important method for improving our capacity to assess human and ecologic exposures as it provides global information on the earth’s surface, water, and atmosphere, and it can provide exposure estimates in regions where available ground observation systems are sparse. For example, data collected with remote sensing over “Ground Zero” was used initially to assess the potential asbestos hazards related to the dust that settled over lower Manhattan after the collapse of the World Trade Center towers. Remote sensing of vegetation combined with GIS has been used to assess potential exposure of wildlife to pesticides and metals.
• Global positioning system (GPS) and geolocation technologies—which are now embedded into many cellular telephones, vehicle navigation systems, and other instruments—provide a means of tracking the geographic position of a person or other species. Geolocation technologies have been used extensively in exposure-assessment studies, are important for providing accurate information on the location of an individual or species in space and time, and offer precise
FIGURE S-2 Selected scientific and technologic advances for measuring and monitoring considered in relation to the conceptual framework shown in Figure S-1.
exposure estimates. When geolocation data (with information on air or water quality) are used with activity measurements readily available through portable accelerometers, additional information can be inferred about potential uptake of stressors.
• GIS allows storage and integration of data from different sources (for example, exposure information and health characteristics of populations) by geographic location. It also provides quantitative information on the topologic relationship between an exposure source and a receptor, which allows researchers to characterize proximity to roadways, factories, water bodies, and other land uses. For example, GIS used with modeling data has provided information on exposure exceedances of threatened and endangered species associated with environmental contaminants. Web-based GIS increasingly serves as a tool for educating and empowering communities to understand and manage environmental exposures.
The increasing use of geographic information technologies (for example, through cellular telephones, GPS, or Web-based systems), many of which are operated by the private sector, raises important issues about privacy protection and the use of the resulting data by exposure-science researchers for improving public health.
Ubiquitous Sensing
Over the last 20 years, there have been substantial advances in personal environmental-monitoring technologies. The advances have been made possible
in part by cellular telephones, which are carried routinely by billions of people throughout the world and may be equipped with motion, audio, visual, and location sensors that can be manipulated with cellular or wireless networks. Pollution-monitoring devices can be integrated into the telephones (for example, for measuring particulate matter and volatile organic chemicals). In this context, cellular telephones, supporting software, and expanding networks (cellular and WiFi) can be used to form “ubiquitous” sensing networks to collect personal exposure information on millions of people and large ecosystems. People can then act as “citizen—scientists”, collecting their own exposure data to inform themselves about what they might be exposed to, and this can lead to more comprehensive application of exposure-science tools for health and environmental protection. However, validation of ubiquitous sensing networks to ensure the accuracy and precision of the data collected is an important consideration.
Developing ubiquitous monitoring for personal exposure assessment will depend on rapid advances in sensor technologies. Despite recent advances, personal sensors still have only modest capacity to obtain highly selective, multistressor measurements. There is a need for a wearable sensor that is capable of monitoring multiple analytes in real time. Such a device would allow more rapid identification of “highly exposed” people to help to identify sources and means of reducing exposures. Recent advances in nanoscience and in nanotechnology offer an unprecedented opportunity to develop very small, integrated sensors that can overcome current limitations.
With regard specifically to environmental exposure, advances in electronic miniaturization of sensors and data management are motivating the development of environmental sensor networks that can provide long-term real-time exposure-monitoring data on our ecosystem. Much of the interest in network sensors has been motivated by national-security concerns, including concerns about monitoring drinking-water or air quality.
Biomonitoring for Assessing Internal Exposures
With advances in genomic techniques and informatics, exposure science is moving from collection of external exposure information on a small number of stressors, locations, times, and individuals to a more systematic assemblage of internal exposures to multiple stressors in individuals in human populations and multiple species in our environment.
The committee considered three broad topics in biomonitoring: measures of internal exposure, biosignatures of exposure, and measurement of biochemical modifiers of internal exposure.
• Measures of internal exposure to stressors are closer to the target site of action for biologic effects than are external measures of exposure and so improve the correlation of exposure with effects. Analytic methods enable the detection of low concentrations of multiple stressors. The measurement of thou-
sands of small organic molecules in biologic samples with metabolomics is now being applied to biomonitoring of chemicals in humans and in wildlife. Such approaches are not limited to a chemical or class of chemicals selected in advance but rather provide broader, agnostic assessment that can identify exposures and potentially improve surveillance and elucidate emerging stressors. Proteomics and adductomics expand the types of internal measures of exposure that can be analyzed, including the analysis of compounds in the blood that have short half-lives, such as oxidants in cigarette smoke and acrylamide. Rapidly evolving sensor platforms linked to physiologically based pharmacokinetic (PBPK)4 models are expected to enable field measurements of chemical samples in blood, urine, or saliva from human and nonhuman populations and rapid interpretation of the concentrations in the samples. However, inferring the sources and routes of these internal exposures remains a research challenge.
• Biosignatures of exposure reflect the net biologic effect of internal exposure to stressors that act on specific biologic pathways. For example, oxidative modifications of DNA or protein can be used to represent the net internal exposure to oxidants and antioxidants. Biosignatures provide better assessment of exposure-disease correlations, but they are still limited in their ability to target reduction in any specific compound or source.
• Measurement of biochemical modifiers of internal exposure can be used qualitatively to identify populations that are expected to have greater internal exposures to a given stressor (for example, because of differences in metabolism or higher absorption) or quantitatively by inclusion in PBPK-pharmacodynamic models used for exposure assessment and prediction of doses. Transcriptomics, proteomics, and to a smaller extent metabolomics offer the ability to measure the status of key biologic processes that affect the pharmacokinetics (that is the absorption, distribution, metabolism, or elimination) of chemical stressors.
With regard to ecologic exposure assessment, the use of molecular techniques as biomarkers to assess ecologic exposure to stressors is limited in that most of these techniques cannot be linked quantitatively to the level of exposure and are not highly selective. There is a need to develop rapid-response, quantitative exposure-assessment tools that can provide useful information for exposure assessment in ecologic risk assessments.
Models and Information-Management Tools
Models and information-management tools are critical for interpreting and managing the quantities of data being generated with the expanding technologies. For example, satellite imaging and personal monitoring techniques are
_______________________
4A mathematical modeling technique for predicting the absorption, distribution, metabolism, and excretion of a compound in humans or other animal species.
generating enormous quantities of spatiotemporal data and information on people’s movements and activities, and biologic assays are capable of monitoring millions of genetic variants, metabolites, or gene-expression or epigenetic changes in thousands of subjects. The ability of models to provide a repository for exposure information, to help in interpreting data and observations, and to provide tools for predicting trends will continue to be a cornerstone of exposure science.
Many types of models will continue to be important in exposure science—for example, activity-based models for tracking the history of individuals or populations and process-based models for tracking the movement of stressors from source to receptor—but there is a growing need for structure—activity models that can classify chemicals with regard to exposure and potential health effects.
The key to the future of exposure models is how they incorporate the increasing number of observations that are being collected. Although observations alone are important, it is their analysis, through application of models, that elucidates the value of the measurements. It is also important to quantify the uncertainty in the exposure estimates provided by models. However, to fully address environmental health concerns, exposure models need to be systematically integrated into source to dose modeling systems.
Informatics encompasses tools for managing, exploring, and integrating massive amounts of information from diverse sources and in widely different formats. Informatics relies on model algorithms, databases and information systems, and Web technologies. Although it is highly developed in biology and medicine, its application in exposure science is in its infancy; informatics offers great promise for improving the linkages of exposure science to related environmental-health fields.
A number of informatics efforts are under way. For example, ExpoCast Database, developed as part of EPA’s Expocast program to advance the characterization of exposure to address the new toxicity-testing paradigm, is designed to house measurements from human exposure studies and to support standardized reporting of observational exposure information. Recently, a pilot Environment-Wide Association Study was conducted in which exposure—biomarker and disease-status data were systematically interpreted in a manner analogous to that in a Genome-Wide Association Study.5 In addition, the exposure field has developed and designed an exposure ontology6 to facilitate centralization and integration of exposure data with data in other fields of environmental health, including toxicology, epidemiology, and disease surveillance.
_______________________
5Genome-Wide Association Studies are epidemiologic studies that examine the associations between particular genetic variants and specific disease outcomes.
6Ontologies, specifications of the terms and their logical relationships used in a particular field, are used to improve search capabilities and allow mapping of relationships among different databases and informatics systems.
A VISION FOR EXPOSURE SCIENCE IN THE 21st CENTURY
New challenges and new scientific advances impel us to an expanded vision of exposure science. The vision is intended to move the field from its historical origins—where it has typically addressed discrete exposures with a focus on either external or internal environments and a focus on either effects of sources or effects on biologic systems, one stressor at a time—to an integrated approach that considers exposures from source to dose, on multiple levels of integration (including time, space, and biologic scale), to multiple stressors, and scaled from molecular systems to individuals, populations, and ecosystems.
The vision, the “eco-exposome”, is defined as the extension of exposure science from the point of contact between stressor and receptor inward into the organism and outward to the general environment, including the ecosphere. Adoption and validation of the eco-exposome concept should lead to the development of a universal exposure-tracking framework that allows the creation of an exposure narrative, the prediction of biologically relevant human and ecologic exposures, and the generation of improved exposure information for making informed decisions on human and ecosystem health protection. The vision is premised on the scientific developments of the last decade.
To advance this broader vision, exposure science needs to deliver knowledge that is effective, timely, and relevant to current and future environmental-health challenges. To do so, exposure science needs to continue to build capacity to
• Assess and mitigate exposures quickly in the face of emerging environmental-health threats and natural and human-caused disasters. For example, this requires expanding techniques for rapid measurement of single and multiple stressors on diverse geographic, temporal, and biologic scales. That includes developing more portable instruments and new techniques in biologic and environmental monitoring to enable faster identification of chemical, biologic, and physical stressors that are affecting humans or ecosystems.
• Predict and anticipate human and ecologic exposures related to existing and emerging threats. Development of models or modeling systems will enable us to anticipate exposures and characterize exposures that had not been previously considered. For example, predictive tools will enable development of exposure information on thousands of chemicals that are now in widespread use and enable informed safety assessments of existing and new applications for them. In addition, strategic use of such diverse information as structural properties of chemicals, nontargeted environmental surveillance, biomonitoring, and modeling tools are needed for identification and quantification of relevant exposures that may pose a threat to ecosystems or human health.
• Customize solutions that are scaled to identified problems. As stated in Science and Decisions: Advancing Risk Assessment (2009), the first step in a risk assessment should involve defining the scope of the assessment in the con-
text of the decision that needs to be made. Adaptive exposure assessments could facilitate that approach by tailoring the level of detail to the problem that needs to be addressed. Such an assessment may take various forms, including very narrowly focused studies, assessments that evaluate exposures to multiple stressors to facilitate cumulative risk assessment, or assessments that focus on vulnerable or susceptible populations.
• Engage stakeholders associated with the development, review, and use of exposure-science information, including regulatory and health agencies and groups that might be disproportionately affected by exposures—that is, engage broader audiences in ways that contribute to problem formulation, monitoring and data collection, access to data, and development of decision-making tools. Ultimately, the scientific results derived from the research will empower individuals, communities, and agencies to prevent and reduce exposures and to address environmental disparities.
For the committee’s vision to be realized in light of resource constraints, priorities need to be set among research and resource needs that focus on the problems or issues that are critically important for addressing human and ecologic health. For example, screening-level exposure information may be adequate to address some questions, targeted data may be useful for others, and extensive data may be required in some circumstances. Health-protective default assumptions can provide incentives for data generation and can allow timely decisions despite inevitable data gaps.
REALIZING THE VISION
The demand for exposure information, coupled with the development of tools and approaches for collecting and analyzing such data, has created an opportunity to transform exposure science to advance human and ecosystem health. The transformation will require an investment of resources and a substantial shift in how exposure-science research is conducted and its results implemented. In the near term exposure science needs to develop strategies to expand exposure information rapidly to improve our understanding of where, when, and how exposures occur and their health significance. Data generated and collected should be used to evaluate and improve models for use in generating hypotheses and developing policies. New exposure infrastructure (for example, sensor networks, environmental monitoring, activity tracking, and data storage and distribution systems) will help to identify the largest knowledge gaps and reveal where gathering more exposure information would contribute the most to reducing uncertainty.
For example, more exposure data needs to be collected to populate emerging exposure databases (for example EPA’s ExpoCast Database) and to develop tools to systematically mine various sources of exposure information, so as to bridge the gap between exposure science and other environmental-health disci-
plines. New and improved surveillance systems can be designed to increase our knowledge of environmental stressors and provide information for estimation and characterization of exposures. Targeted exposure studies will be essential for gathering detailed information on hot spots or places of highest potential impact to vulnerable and susceptible populations. Surveillance programs together with targeted exposure-measurement programs will help build a predictive exposure network that can address environmental-health questions.
Research Needs
To implement its vision, the committee identified research needs that call for further development of existing and emerging methods and approaches, validation of methods and their enhancement for application on different scales and in broader circumstances, and improved linkages to research in other sectors of the environmental-health sciences. The research needs are organized into several broad categories addressed below, and they are organized by priority within each category on the basis of the time that will be required for their development and implementation: short term denotes less than 5 years, intermediate term 5-10 years, and long term 10-20 years.
Providing effective responses to immediate or short-term public-health or ecologic risks requires research on observational methods, data management, and models:
Short term
• Identify, improve, and test instruments that can provide real-time tracking of biologic, chemical, and physical stressors to monitor community and occupational exposures to multiple stressors during natural, accidental, or terrorist events or during combat and acts of war.
• Explore, evaluate, and promote the types of targeted population-based exposure studies that can provide information needed to infer the time course of internal and external exposures to high-priority chemicals.
Intermediate term
• Develop informatics technologies (software and hardware) that can transform exposure and environmental databases that address different levels of integration (time scales, geographic scales, and population types) into formats that can be easily and routinely linked with populationwide outcome databases (for humans and ecosystems) and linked to source-to-dose modeling platforms to facilitate rapid discovery of new hazards and to enhance preparedness and timely response.
• Identify, test, and deploy extant remote sensing, personal monitoring techniques, and source to dose model-integration tools that can quantify multiple routes of exposure (inhalation, ingestion, and dermal uptake) and obtain results that can, for example, be integrated with emerging methods (such as —omics technologies)7 for tracking internal exposures.
Long term
• Enhance tracking of human exposures to pathogens on the basis of a holistic ecosystem perspective from source through receptor.
Supporting research on health and ecologic effects that addresses past, current, and emerging outcomes:
Short term
• Coordinate research with human-health and ecologic-health scientists to identify, collect, and evaluate data that capture internal and external markers of exposure in a format that improves the analysis and modeling of exposure-response relationships and links to high-throughput toxicity testing.
• Explore options for using data obtained on individuals and populations through market-based and product-use research to improve exposure information used in epidemiologic studies and in risk assessments.
Intermediate term
• Develop methods for addressing data and model uncertainty and evaluate model performance to achieve parsimony in describing and predicting the complex pathways that link sources and stressors to outcomes.
• Improve integration of information on human behavior and activities for predicting, mitigating, and preventing adverse exposures.
Long term
• Adapt hybrid designs for field studies to combine individual-level and group-level measurements for single and multiple routes of exposure to provide exposure data of greater resolution in space and time.
Addressing demands for exposure information among communities, governments, and industries with research that is focused, solution-based, and responsive to a broad array of audiences:
_______________________
7Technologies used to identify and quantify all members of particular cellular constituents, for example, proteins (proteomics), metabolites (metabolomics), or lipids (lipomics).
Short term
• Develop methods to test consumer products and chemicals in premarketing controlled studies to identify stressors that have a high potential for exposure combined with a potential for toxicity to humans or ecologic receptors.
• Develop and evaluate cost-effective, standardized, non-targeted, and ubiquitous methods for obtaining exposure information to assess trends, disparities among populations (human and ecologic), geographic hot spots, cumulative exposures, and predictors of vulnerability.
Intermediate term
• Apply adaptive environmental-management approaches to understand the linkages between adverse exposures in humans and ecosystems better.
• Implement strategies to engage communities, particularly vulnerable or hot-spot communities, in a collaborative process to identify, evaluate, and mitigate exposures.
Long term
• Expand research in ways to use exposure science to more effectively regulate environmental risks in natural and human systems, including the built environment.
Transagency Coordination
Exposure science is relevant to the mission of many federal agencies, and transagency collaboration for exposure science in the 21st century would accelerate progress in and transform the field. Tox21—a collaboration among EPA, the National Institutes of Health (NIH), and the Food and Drug Administration—that was established to leverage resources to advance the recommendations in the 2007 National Research Council report Toxicity Testing in the 21st Century: A Vision and a Strategy serves as a relevant model. The present committee considers that the model used in establishing Tox21 could be extended to exposure science and lead to the creation of Exposure21. Exposure21, in addition to engaging the stakeholders (government, industry, and nongovernment organizations) involved in Tox21, would need to be extended to other federal agencies—such as the U.S. Geological Survey, the Centers for Disease Control and Prevention, the National Oceanic and Atmospheric Administration, the National Science Foundation (NSF), and the National Aeronautics and Space Administration—to promote greater access to and sharing of data and resources on a broader scale. Including them would provide access to resources for transformative technology innovations, for example, in nanosensors.
Enabling Resources
As the collaborative partnerships among agencies are expanded, there will be opportunities to share research results, to demonstrate the value of exposure-science research to other agencies and decision-makers, and to generate additional resources. The committee recommends that intramural and extramural programs in EPA, NIEHS, the Department of Defense, and other agencies that advance exposure-science research be supported as the value of the research and the need for exposure information become more apparent.
Much of the human-based research in environmental-health sciences is funded by NIH. However, none of the existing study sections that review grant applications has substantial expertise in exposure science, and most study sections are organized around disease processes. In light of that and the role that an understanding of environmental exposures can play in disease prevention, a rethinking of how NIH study sections are organized that incorporates a greater focus on exposure science would allow a core group of experts to foster the objectives of exposure-science research. In addition, an increase in collaborations between agencies should be explored; for example, collaborations between EPA, NIEHS, and NSF could support integrative research between ecosystem and human-health approaches in exposure science. However, many other agencies engaged in exposure-science research could be included in the collaborations.
Because of the need to understand and prevent harmful exposures and risks in our society, EPA and NIEHS need to be able to work with the academic community to conduct exposure studies in all populations, particularly among the most vulnerable (for example, the elderly, children, and the infirm), under appropriate ethical guidelines.
The effective implementation of the committee’s vision will depend on development and cultivation of scientists, engineers, and technical experts with experience in multiple fields to educate the next generation of exposure scientists and to provide opportunities for members of other fields to cross-train in the techniques and models used to analyze and collect exposure data. Exposure scientists will need the skills to collaborate closely with other fields of expertise, including engineers, epidemiologists, molecular and system biologists, clinicians, statisticians, and social scientists. To achieve that, the committee considers that the following are needed:
• An increase in the number of academic predoctoral and postdoctoral training programs in exposure science throughout the U.S. supported by training grants. NIEHS currently funds one training grant in exposure science; additional grants are needed.
• Short-term training and certification programs in exposure science for midcareer scientists in related fields.
• Development, by federal agencies that support human and environmental exposure science, of educational programs to improve public understanding of exposure-assessment research, including ethical considerations involved in the research. The programs would need to engage members of the general public, specialists in research oversight, and specific communities that are disproportionately exposed to environmental stressors.
Participatory and Community-Based Research Programs
To engage broader audiences, including the public, the committee suggests the development of more user-friendly and less expensive monitoring equipment to allow trained people in communities to collect and upload their own data in partnership with researchers. Such partnerships would improve the value of the data collected and make more data available for purposes of priority-setting and informing policy. One approach might include implementing a system of ubiquitous sensors (for example, through the use of cellular telephones, GPS, or other technologies) in two American cities to evaluate the feasibility of such systems to develop community-based exposure data that are reliable. Potential issues of privacy protection would need to be considered.
CONCLUDING REMARKS
Exposure information is crucial for predicting, preventing, and reducing human health and ecosystem risks. Exposure science has historically been limited by the availability of methods, technologies, and resources, but recent advances present an unprecedented opportunity to develop more rapid, cost-effective, and relevant exposure assessments. Research supported by such federal agencies as EPA and NIEHS has provided valuable partnership opportunities for building capacity to develop the technologies, resources, and educational structure that will be needed to achieve the committee’s vision for exposure science in the 21st century.
