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2
A Vision for Exposure Science
in the 21st Century
Understanding the contact between a stressor and a receptor is at the heart
of exposure science--and the starting point for the committee's expanded vision
for exposure science in the 21st century. Federal, state, and municipal agency
use of the concept of exposure to control environmental risks has contributed to
major improvements in environmental protection in the United States and else-
where. For example, the concept of exposure was instrumental in efforts to con-
trol secondhand tobacco smoke, a major source of exposure, but a minor con-
tributor to emissions or ambient air pollution where measurement and regulation
had focused previously.
New challenges and new scientific advances, documented in Chapters 4
and 5, impel us to an expanded vision of exposure science. Understanding ag-
gregate or cumulative exposures in their full environmental context will require
new approaches to exposure assessment--moving both inward and outward
from the core point of contact.
We modify the exposome concept described in Chapter 1 in this broader
vision of exposure science:
Vision: exposure science extends from the point of contact between
stressor and receptor inward into the organism and outward to the general envi-
ronment, including the ecosphere.
We suggest the term "eco-exposome" to encapsulate the concept of this
expanded vision.
In light of the new concept, we foresee, among other developments, the
evolution of a universal exposure-tracking framework that allows the creation of
an exposure narrative and the prediction of virtually all biologically relevant
human and ecologic exposures with sensitivity, specificity, and wide coverage.
42
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A Vision for Exposure Science in the 21st Century 43
To retain its value, the principal goal of exposure science must continue to be
the prevention and mitigation of adverse exposures to protect human and eco-
system health with a focus on the routes by which environmental stressors reach
humans and ecosystems.
Given that vision, exposure science can maintain and augment its rele-
vance to the everyday lives of citizens as they seek measures to protect their
health and the health of the ecosystems on which they depend. Exposure science
also will continue to contribute to understanding of exposures in numerous set-
tings--outdoors, indoors, and in the occupational environment--and of how
those exposures internalize in an organism.
Implicit in the eco-exposome concept is the recognition that humans live
in and are part of an ecosphere and that human exposures are intimately linked
to exposures flowing through ecosystems. Efforts to understand ecosystem ex-
posures will improve our knowledge of how exposures affect human populations
and individuals. Narrating the flow and pulse of exposures through the eco-
sphere, of which humans are part, also promotes a more thorough investigation
of the potential sources of exposure and how these sources can be controlled to
protect public and ecosystem health. Because the life courses of humans and
ecosystems are dynamic, the eco-exposome will have to evolve scientifically to
define what constitutes a biologically relevant exposure.
The committee's vision is premised on scientific developments of the last
decade. Advances in local sensor systems, remote sensing, analytic methods,
molecular technologies, computational modeling systems, and bioinformatics
have provided opportunities to develop systems approaches that can be inte-
grated into exposure science. There is now an unprecedented opportunity to con-
sider exposures from source to dose, on multiple levels of integration within the
ecosphere (including time, space, and biologic scales), to multiple stressors, and
scaled from molecular systems to individuals, populations, and ecosystems.
Many of the scientific innovations have been in fields outside traditional
exposure science, and achieving the vision will require higher levels of transdis-
ciplinary and interagency cooperation than have occurred in the field of expo-
sure science in the past. In addition, collaborative approaches will be needed to
engage communities and stakeholders from problem formulation through data
collection to development of responsive solutions and to improve communica-
tion among and participation by stakeholders. Such engagement strategies in
field studies can lead to more comprehensive application of exposure-science
tools to health and environmental protection, including issues of environmental
justice.
In this report, the committee presents a roadmap of how technologic inno-
vations and strategic collaborations can advance exposure science in the 21st
century. The committee believes that exposure science needs to deliver knowl-
edge that is effective, timely, and relevant to current and future environmental-
health challenges. To do so, exposure science needs to continue to build capac-
ity to
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44 Exposure Science in the 21st Century: A Vision and A Strategy
Assess and mitigate exposures quickly in the face of emerging envi-
ronmental-health threats and natural and human-caused disasters.
Predict and anticipate human and ecologic exposures related to exist-
ing and emerging threats.
Customize solutions that are scaled to identified problems.
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.
The committee recognizes the complex interdependence of human and
ecologic systems and adopts an integrated definition of environmental health. In
the context of the vision statement, exposure science addresses chemical, physi-
cal, and biologic stressors and associated behavioral and societal factors that
affect human and ecologic health, including protection of vulnerable populations
and susceptible individuals.
The following sections elaborate on core elements of the vision. Later
chapters provide specific components of the roadmap for realizing the vision of
exposure science in the 21st century.
Assess and Mitigate
Assessing and mitigating exposures effectively require techniques for
rapid measurement of single and multiple stressors on diverse geographic, tem-
poral, and biologic scales and an enhanced infrastructure for rapid deployment
of resources to address imminent threats, such as the Deepwater Horizon oil
spill, Hurricane Katrina, and the tragedy of 9/11. In those three cases, there was
a need to evaluate the status of the environment and the exposure of populations
via a variety of pathways (such as air, water, soil, and food) while anticipating
potential health effects. In the immediate aftermath of Hurricane Katrina, for
example, there was an urgent need to evaluate drinking-water safety; a wide
array of potential microbiologic and chemical contaminants in sediment, soil,
and fish; and air-quality threats posed by mold, endotoxins, and other contami-
nants in indoor and outdoor environments. It is important that such assessments
be handled quickly and effectively to inform and protect first responders,
cleanup workers, and affected populations and to respond to stakeholder con-
cerns about the potential for short-term and long-term health effects.
The use of more portable instruments and new techniques in biologic and
environmental monitoring will enable faster identification of chemical, biologic,
or physical stressors that are affecting humans or ecosystems. Testing of stress-
ors of potential concern in targeted studies would allow rapid responses and
deployment of exposure-mitigation measures.
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A Vision for Exposure Science in the 21st Century 45
Predict and Anticipate
Enhancing our predictive capabilities through the development of models
or modeling systems will enable us to anticipate exposures and characterize ex-
posures that had not been previously considered. For example, modeling will
improve our ability to reconstruct external exposures on the basis of the increas-
ing number of internal markers of exposures that are being collected. In addi-
tion, exposure models and controlled simulation studies will enable sustainable
innovation in developing benign nanomaterials and less toxic chemical alterna-
tives. Predictive tools will also allow us to develop exposure information on
thousands of chemicals that are now in widespread use and will enable informed
safety assessments of existing and new applications for these chemicals. Finally,
predictive tools will allow us to forecast, prevent, and mitigate the potential ef-
fects of major societal problems, such as climate change, security threats, and
urbanization. Innovative and expedient exposure-assessment approaches that
strategically use diverse information such as structural properties of chemicals,
nontargeted environmental surveillance, biomonitoring, and modeling and re-
lated data-integration tools are needed for the identification and quantification of
relevant exposures that may pose a threat to ecosystems or human health.
Using such tools, especially in parallel with pathway-based toxicity
screening, in the evaluation of new and emerging environmental stressors can
help to ensure that substances in the marketplace are safer. The tools are likely
to require broader access to data that now are commonly proprietary, including
manufacturing, import, sales, and use data and chemical properties. New data-
generation requirements also may be needed; for example, systematic toxicity
screening and screening-level exposure assessments would provide a more ro-
bust basis for modeling. Exposure-based predictive screening could identify and
predict introduction of chemicals that pose potentially serious environmental or
health concerns. For example, thoughtful application of predictive tools would
have prevented hasty promotion of methyl tertiary butyl ether as a replacement
for lead in gasoline, which resulted in widespread contamination of groundwa-
ter, or universal application of polybrominated diphenyl ethers as flame retar-
dants, which are now ubiquitous in trace amounts in human breast milk (Gold-
stein 2010; LaKind and Birnbaum 2010). Such prevention strategies could re-
duce the risk of disease in exposed populations, substantially reduce future
mitigation costs occasioned by widespread environmental contamination, and
encourage benign design and green-chemistry approaches to product develop-
ment and waste disposal. Given that it will take many years to develop compre-
hensive toxicologic assessments for chemicals in commerce, exposure monitor-
ing can help to ensure against unintended health and environmental conse-
quences.
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46 Exposure Science in the 21st Century: A Vision and A Strategy
Customize Solutions
As stated in a 2009 National Research Council report (NRC 2009), the
first step in a risk assessment should involve defining the scope of the assess-
ment in the context 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. Health-protective default values
for exposure can be used in the absence of alternative information to expedite
decision-making and to encourage generation of more chemical-specific data
that are needed for risk assessment.
For example, a tiered approach that is customized according to expected
future land uses and standardized health-protective default assumptions is incor-
porated into EPA's supplemental soil screening guidance (SSG) (EPA 2002).
The SSG is a tool used to standardize and speed the assessment and cleanup of
contaminated soil at sites on the National Priorities List (Superfund). The origi-
nal 1996 EPA SSG (EPA 1996) focused exclusively on residential land use and
did not incorporate alternative scenarios, such as future commercial or industrial
land use (which would require less thorough cleanup), risks to workers, dermal
exposure pathways, or inhalation from indoor vapor intrusion. The 2002 revi-
sions allowed greater customization of the solutions according to the populations
that would probably be exposed (for example, children and workers), anticipated
exposure pathways, and future use of the land. The SSG is designed to be used
only as a first-tier approach to evaluating a site, and more detailed and fully cus-
tomized exposure assessments should be done if the SSG indicates a potential
concern. This example illustrates that it is possible for agencies to develop stan-
dardized approaches to exposure assessment that can allow rapid assessment and
conservation of resources while incorporating an increasingly customized and
site-specific approach where needed.
Engage Stakeholders
Engaging broader audiences, including involving scientists in the concerns
and needs of the public, will make the field more responsive and can improve
problem formulation, monitoring and collection of data, access to data, and de-
velopment of decision-making tools. Ultimately, the scientific results derived
from the research will empower individuals, communities, and agencies in pre-
venting and reducing exposures and in addressing environmental disparities.
Engaging stakeholders will also mean moving beyond the science of inquiry to
the science of engagement and the science of application (Boyer 1996). (Addi-
tional discussion on engaging the community to respond to health concerns is
addressed in Chapter 6.)
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A Vision for Exposure Science in the 21st Century 47
Exposure science has played and will continue to play an important role in
providing scientific data for use in assessing whether socially disadvantaged
groups suffer disproportionate adverse exposures. Disadvantaged groups often
have less access than other groups to beneficial or health-promoting exposures
(such as access to parks and green spaces), an important consideration for popu-
lation health (Sister et al. 2010; WHO 2010). And known interactions between
psychosocial stressors and environmental exposures need to be considered and
quantified for exposure science to be responsive (Shankardass et al. 2009).
Any effort to identify and quantify exposures in a way that fully addresses
environmental disparities and that is capable of capturing the complex interac-
tions between stressors in communities will need to use current measurement
strategies and deploy new tools in exposure science broadly. Widespread im-
plementation of biomonitoring of many chemicals in varied populations (on the
basis of internal markers of exposure) will be useful in identifying exposure
distributions and disparities. Key however is the need for exposure information
to be accessible to community members and for them to have input in decisions
involving exposure prevention or intervention. The committee maintains that it
will be critically important to use such approaches as coupling of biomonitoring
with collection of relevant environmental exposure data, source data, and health
data to allow interpretation of the implications of exposures to facilitate preven-
tion and intervention.
Participatory sensing techniques, which allow people to collect data on
their own activities and on their communities, can be enabled for specific pollut-
ants and exposure routes. However, people who are to be active in such pro-
grams need training, in both how to collect such data, and in its utility and limi-
tations. Additionally the results need to be quality-assured and validated by
trained professionals. For example, ubiquitous sensing technologies, such as
those of smart cellular telephones, can facilitate collection of data on time
activity relationships that can provide information to support the need for meas-
urements of pollutant exposures in many poorly characterized microenviron-
ments. The development of user-friendly and less expensive monitoring equip-
ment can 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 when setting priorities for
exposure-control options. The collection and interpretation of such data raises
many scientific questions and underscores the efforts needed to validate meas-
urements and to determine how to integrate the information into models that
support effective stakeholder engagement and decision-making.
Enhancing Exposure Science
Human and ecologic systems are inextricably linked. As part of the eco-
system, humans affect and are affected by interactions with the other organisms
and nonliving components of the environment. At the most fundamental level,
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48 Exposure Science in the 21st Century: A Vision and A Strategy
human health and well-being depend on the goods (for example, clean air and
water) and services (for example, groundwater recharge, carbon sequestration,
pollination, and seed dispersal) that are provided by ecosystems. Ecosystem
health protection will require an expansion of problem-solving approaches that
recognize that humans are an integral part of complex ecosystems that operate
on wide spatiotemporal scales and varying levels of biologic organization, with
consideration of exposures occurring both outside and inside exposed organ-
isms.
The better we understand the complex interactions and feedbacks among
the various human and nonhuman components of ecosystems, the better we will
understand the spatial and temporal variability in risk and magnitude of expo-
sure. Incorporating ecologic information into exposure assessments will allow us
to identify how ecosystems cause, buffer, or magnify exposures. By broadening
the view of receptors to include both ecologic and human receptors through the
eco-exposome concept, exposure science will be able to connect stressors to
changes in ecosystem function and in the ecologic goods and services on which
society depends. From an operational perspective, the first step toward that inte-
gration will occur during the problem-formulation stage, where the human
ecology linkages can be articulated explicitly. In broadening their view of recep-
tors, researchers and regulators will consider not only human health outcomes
but, when it is feasible, ecosystem attributes and their interdependences.
Major challenges in exposure science, combined with the opportunities
presented by new technologies, suggest the need for a transformation in expo-
sure science. Strategic investments in this transformation are crucial for devel-
opment of health-protective strategies in the 21st century. The investments must
address strategies for research, education and training, and outreach for the de-
velopment of collaborative and responsive frameworks for implementing these
strategies in a resource-constrained environment. Moving forward with such a
vision will provide a strong scientific basis for policy decisions that are respon-
sive to a broad array of stakeholders.
REFERENCES
Boyer, E. 1996. The scholarship of engagement. Journal of Public Service and Outreach
1(1):11-20.
EPA (U.S. Environmental Protection Agency). 1996. Soil Screening Guidance: Technical
Background Document. EPA/540/R95/128. Office of Solid Waste and Emergency
Response, U.S. Environmental Protection Agency, Washington, DC [online].
Available: http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/chemi
cals/SSG_nonrad_technical.pdf [June 19, 2012].
EPA (U.S. Environmental Protection Agency). 2002. Supplemental Guidance for Devel-
oping Soil Screening Levels for Superfund Sites. OSWER 9355.4-24. Solid Waste
and Emergency Response, U.S. Environmental Protection Agency, Washington,
DC [online]. Available: http://www.epa.gov/superfund/health/conmedia/soil/pdfs/
ssg_main.pdf [June 19, 2012].
OCR for page 49
A Vision for Exposure Science in the 21st Century 49
Goldstein, B.D. 2010. MTBE: A poster child for exposure assessment as central to effec-
tive TSCA reform. J. Expo. Sci. Environ. Epidemiol. 20(3):229-230.
LaKind, J.S., and L.S. Birnbaum. 2010. Out of the frying pan and out of the fire: The
indispensable role of exposure science in avoiding risks from replacement chemi-
cals. J. Expo. Sci. Environ. Epidemiol. 20(2):115-116.
NRC (National Research Council). 2009. Science and Decisions: Advancing Risk As-
sessment. Washington, DC: National Academies Press.
Shankardass, K., R. McConnell, M. Jerrett, J. Milam, J. Richardson, and K. Berhane.
2009. Parental stress increases the effect of traffic-related air pollution on child-
hood asthma incidence. Proc. Natl. Acad. Sci. USA 106(30):12406-12411.
Sister, C., J. Wolch, and J. Wilson. 2010. Got green? Addressing environmental justice in
park provision. GeoJournal 75(3):229-248.
WHO (World Health Organization). 2010. Environment and Health Risks: A Review of
the Influence and Effects of Social Inequalities. World Health Organization
[online]. Available: http://www.euro.who.int/__data/assets/pdf_file/0003/78069/E
93670.pdf [accessed Mar. 26, 2012].
