Exposure Science in the 21st Century A Vision and a Strategy (2012) / Chapter Skim
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3 Applications of Exposure Science
3 Applications of Exposure Science
Pages 50-89
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From page 50... ...
EPIDEMIOLOGY Exposure assessment is a major component of environmental epidemiology; it is equal in importance to outcome assessment. Historically, the main focus of many environmental epidemiology studies has been on single chemical, biologic, and physical stressors (for example, individual pesticides, air pollutants, ionizing radiation, or water contaminants)
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From page 51... ...
Items in gray, related to health outcomes and their determinants other than environmental exposures, are included to place exposure assessment in context but are outside the charge of this committee. Boxes represent measurable quantities, and ovals denote hypothetical intermediate variables that can be assessed only indirectly.
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From page 52... ...
. Box 3-1 illustrates some of the complexities of exposure assessment for the National Children's Study, with longitudinal measurements of a broad array of environmental and personal (external and internal)
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From page 53... ...
. The development of the exposure assessment component of the NCS study highlights the challenges for exposure science to meet the demands for exposure information across time scales for large populations.
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Dur ing the early years, considerable quantities of radionuclides were released into the environment, notably iodine-131, which tends to accumulate in the thyroid gland of exposed people and can lead to thyroid cancers and other thyroid abnormalities. To address concerns of the downwind population, two projects were launched by the Centers for Disease Control and Prevention: the Hanford Environmental Dose Reconstruction (HEDR)
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From page 55... ...
That is a longterm goal that will require new approaches for conducting research, including capitalizing on future advances in individualized medicine and understanding the effects of changes in lifestyle and human behaviors. Exposure assessment is usually constrained by cost or other feasibility considerations.
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From page 56... ...
The availability of various population-wide outcome databases -- such as databases of mortality, hospitalization, and cancer incidence -- is unfortunately not matched by population-wide exposure databases. The availability of a national dose registry for radiation workers in Canada, however, has made it possible to use record-linkage techniques to conduct large-scale studies of dose response relationships for cancer (Zablotska et al.
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From page 57... ...
may provide unique opportunities to build large-scale databases that, when combined with biomarkers of exposure assayed from routinely collected biospecimens and systematically collected exposure information (from clinic visits or questionnaires) , could form the basis of longterm cohort studies.
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. As described in Chapter 2, that report envisioned a process for screening chemicals in commerce for hazard potential with rapid toxicitypathway screens informed by and with priorities set through screening-level exposure assessments.
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Although these studies might be expected initially to focus on individual stressors, they would evolve with advances in exposure technologies to identify and characterize combinations of stressors. There are also opportunities for epidemiology and toxicology to be more closely tied to the process of exposure assessment.
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. Although exposure assessment is often described as perhaps the most challenging component of risk assessment, prior National Research Council reports on risk assessment have made limited recommendations for improving the quality of exposure data or the utility of exposure assessment for quantitative risk assessment.
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From page 61... ...
The 2009 National Research Council report Science and Decisions: Advancing Risk Assessment, which focused on improving human-health risk assessment but also considered ecologic risk assessment, contains several recommendations related to exposure assessment. It describes major challenges that risk assessment is facing and concludes that regulatory risk assessment has become bogged down and that many assessments take a decade or longer to complete.
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From page 62... ...
Exposure assessments may therefore need to collect information about exposure to a variety of chemical and nonchemical stressors that may interact to influence health risk. Improve stakeholder involvement and make the process more accessible to the general public.
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Further discoveries of the chemical in agricultural wells spurred extensive investigations of perchlorate uptake into food by the Food and Drug Administration and by independent scientists, and the result ing information was used in exposure assessments by the California Envi ronmental Protection Agency and others to derive risk based standards. De velopment of a more sensitive analytic method for detecting perchlorate in water supplies ultimately drove the cleanup of numerous industrial and mili tary sites and the creation of a National Research Council committee that reviewed the U.S.
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From page 64... ...
. For agents on which there are population exposure data, exposure disparities can be tracked by evaluating the distribution of the exposure concentrations
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. Progress toward that goal will be seen in a reduction in the skewness of the population exposure data or through followup assessment in targeted populations.
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From page 66... ...
Some instances of determination of compensation, such as "presumptive disability policies" for some classes of veterans intended to give the veterans the "benefit of the doubt", require no individual exposure assessment; the mere fact of having developed a particular disease deemed potentially service-connected and having had the potential for exposure is sufficient. The need for presumptions often arises because of a lack of exposure data (IOM 2008)
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From page 67... ...
ENVIRONMENTAL PLANNING Exposure assessment has contributed to urban and environmental planning, informing our understanding of how different patterns of land use can change the magnitudes of emissions and exposures of humans and ecosystems. Exposure science is increasingly used in health impact assessments.2 Box 3-7 illustrates the application of exposure science to health impact assessment in San Francisco.
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SFDPH identified several im portant environmental impacts (air and noise pollution and traffic collisions) and proposed mitigations.
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However, active travel involves other exposures and potential health risks, including air pollution, accidents, and noise (de Nazelle et al.
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Salutogenic exposures also illustrate the link between healthy ecosystems and human health. Ecosystem Planning Although exposure assessments can include a diverse suite of ecologic receptors (for example, fish, aquatic plants, amphibians, birds)
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, exposure assessments also consider the hierarchic context of the process or problem, work collaboratively across ecologic boundaries, use diverse data from research and monitoring efforts, and, to some extent, recognize that humans are part of the ecosystem. However, one piece of ecosystem planning and management that is largely absent from current exposure assessments is the emphasis on adaptive management, whereby managers and planners treat management as a learning process (an experiment)
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From page 72... ...
However, Lake Tahoe presents a good case study of the ecologic and potential economic impacts of multiple stressor exposures. Within the last 40 years, scientists have documented a steady decline in lake clarity and an increase in primary production (Jassby et al.
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. Thus, it is possible that exposure to multiple stressors that have facilitated the establishment of largemouth bass in Lake Tahoe can result in large increases in MeHg expo sure of both native and nonnative species and affect the ecologic resources of the region.
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FIGURE 3-2 Exposure to Multiple Stressors in Lake Tahoe.
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From page 75... ...
Exposure assessments are intended as a means of reducing personnel injuries and as a form of preventive surveillance as information on exposures can be used by physicians at a later time to treat exposed individuals if they develop symptoms. In such situations, there is a need to provide information on the personal protective equipment required and to enforce administrative controls to guard sites.
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From page 76... ...
Epidemiology Exposure science should aim to provide epidemiologists with novel tools to improve exposure assessment, particularly comprehensive assessment of cumulative exposures to the ensemble of relevant stressors. That will require use of new remote-sensing and other high-volume techniques for measuring the external environment and new omics technologies for the internal environment.
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From page 77... ...
. Training of emergency and law-enforcement agency personnel regarding potential expo sures and potential hazards to health is important, including rapid exposure characterization to minimize additional injuries to workers and the public.
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From page 78... ...
Environmental Planning Exposure science should be an increasingly integral component of environmental planning because of its ability to inform decisions during urban projects that may affect public health (for example, through exposure to increased air-pollutant emissions or potential increases in exposure to green space) and because of its ability to recognize the complex interactions among humans and ecosystems that are critical for protecting human and ecosystem health.
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From page 79... ...
2011. Green Spaces in Healthy Places: Objective Data Demonstrates an Association between Green ness and Momentary Measures of Physical Activity in Children.
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2008. Challenges of exposure assessment for health studies in the aftermath of chemical incidents and disasters.
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Prepared for North Lake Tahoe Resort Association, Tahoe City, CA, by Dean Runyan Associates, Portland, OR [online]
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2010. Mercury flux to sediments of Lake Tahoe, California-Nevada.
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2012. Differ ential tolerance of native and non-native fish exposed to ultraviolet radiation and fluoranthene in Lake Tahoe (CA/NV)
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1996. Determining long-term water quality in the presence of climate variability: Lake Tahoe (USA)
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2007. Assessment of inhalation exposures and potential health risks to the general population that resulted from the collapse of the World Trade Center towers.
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2005. Exposure assessment in the National Children's Study: Introduction.
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2005. Exposure assessment implications for the design and implementation of the National Children's Study.
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1996. Hanford Environmental Dose Reconstruction Project -- an overview.
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From page 89... ...
2005. Effects of environmental agents on the attainment of puberty: Considerations when assessing exposure to environmental chemicals in the National Children's Study.
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