Strategies to Protect the Health of Deployed U.S. Forces Detecting, Characterizing, and Documenting Exposures (2000) / Chapter Skim
Currently Skimming:
2 Characterizing Exposures
2 Characterizing Exposures
Pages 26-49
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 26... ...
The following topics are addressed in the sections below: the need for exposure characterization; strategies for assessing exposure to harmful agents; the collection of environmental samples; the use of modeling, simulation, and decision trees; and needs, capabilities, and opportunities for the future. The final section contains key findings and recommendations for characterizing exposures.
|
From page 27... ...
If the unit has a high probability of being exposed, all members of the unit would be assumed to be at risk. If tracking and exposure information on individuals could be temporarily stored and then, at a later date, retrieved for historical purposes, this could alleviate the near-term problem of data overload and enable DoD to analyze the effects of low-level exposures to CB agents and other toxic agents on a given individual.
|
From page 28... ...
Strategies for Characterizing Exposures Strategies for characterizing exposures can be defined in terms of time scales real-time, prospective, or retrospective. Real-time sampling strategies are used for determining exposures of deployed personnel (in various settings)
|
From page 29... ...
Thus, exposure information should not be provided as single values but should be accompanied by some measure of reliability. In some cases, some uncertainties and variabilities can be resolved using decision trees and event trees (see Appendix A)
|
From page 30... ...
These assessments will require that DoD continue to modify its strategies for collecting exposure information. A growing body of evidence in the public health field indicates that determining total exposure would greatly facilitate the identification, assessment, and management of health risks.
|
From page 31... ...
Using Statistics Environmental monitoring protocols can be an essential component of research studies on health effects or exposure trends. These studies typically include statistical sampling methods, and in some cases, monitoring is stratified using probabilistic sampling methods (the type of stratification depends on the objectives of the study)
|
From page 32... ...
The NHEXAS studies include multimedia exposure assessments. Using Monitoring Data with Exposure Models Tracking exposures requires integrating monitoring data and timeactivity data in a structured, time-dependent fashion.
|
From page 33... ...
When environmental samples are used to characterize exposure, the accuracy of the characterization depends on the types of samples collected. No monitoring strategy can completely eliminate uncertainties about agent concentrations and provide a sufficient number of samples to characterize precise exposure variabilities among deployed troops.
|
From page 34... ...
monitors could have been used in some of the tents where kerosene space heaters, which emit excess amounts of particulate matter, nitrous oxide, sulfur dioxide, carbon monoxide, and hydrocarbons, were used during the Persian Gulf deployment. Instead, postdeployment studies with simulants were conducted (U.S.
|
From page 35... ...
Emerging sampling strategies are relying more on biomarkers; and less invasive biomarkers, such as urine, saliva, or hair, might eventually be used for monitoring exposures to a large number of harmful chemicals. Urinary Biomarkers have worked very well for measuring the presence of metals, tobacco smoke, and some other pollutants.
|
From page 36... ...
MODELING, SIMULATIONS, AND DECISION ANALYSES Modeling, simulations, and decision analysis can greatly improve interpretations of information obtained from CB detection equipment by providing a systematic and iterative process for assessing the value of improved or new information. To date, only limited modeling has been used to interpret chemical agent detection, and it is unclear how much DoD intends to use modeling, simulations, and decision analysis methods in deployment settings to identify and interpret information obtained from CB detection equipment.
|
From page 37... ...
Based on the time spent in each sampled location, the average exposure received by the individual or group at a given location can be calculated directly. The ratio of this partial exposure component to the cumulative exposure calculated for that individual or group can then be compared with the estimates based on the integrated samplers to assess the magnitude of error.
|
From page 38... ...
The calculated TWA can be compared with the integrated personal exposure measurement using an analysis of covariance procedure to assess the agreement between the estimated and measured exposure and to estimate the average pollutant concentrations in nonmeasured locations and their importance from the value and relative significance of the regression coefficients (Quackenboss et al., 1986; Spengler et al., 1985~. Models of Daily Intake An alternative to exposure modeling frequently used for chemicals with long-term cumulative health effects (e.g., carcinogens)
|
From page 39... ...
Total exposure assessments includes measurements, or estimates, of contact with contaminants of concern through inhalation, ingestion, and dermal contact. The estimates of total exposure for deployed forces from this combination of data will probably be much higher than estimates based on either occupational or ambient pollutant concentrations (Bertollini et al., 1995; Corn, 1971; Moschandreas, 1981; NRC, 1981b, 1985a, 1985b, l991b; Ott, 1995; Pirkle et al., 1995; Quackenboss et al., 1991; Sexton et al., 1992, 1995a, 1995b; Sexton and Ryan, 1988; Spengler et al., 1981, 1985; Wallace, 1992; WHO, 1982a, 1982b, 1983, 1989~.
|
From page 40... ...
It also involves strategies for interpreting trends from measurements collected near the detection limit of the equipment and methods for using exposure data for only a fraction of the exposed population. Continuous monitoring (with data loggers)
|
From page 41... ...
For instance, one could compare the personal exposure sampling results with exposure estimates based on the indirect method of combining area sampling with personal time budgets. Aerosol and Particulate Matter Potential health impacts of exposure to particulate matter are related to particle size.
|
From page 42... ...
The availability of modeling and simulation for retrospective exposure assessments is very limited. Some biomarkers could be used for short-term retrospective estimates.
|
From page 43... ...
FINDINGS AND RECOMMENDATIONS Finding. To date, exposure assessments for both civilian and military populations have focused primarily on exposures to contaminants in a specific medium (e.g., air, water, soil, food)
|
From page 44... ...
should devote more resources to designing and employing both statistical sampling and sample stratification methods. Two useful examples of probability-based statistical sampling are the National Human Exposure Assessment Studies (NHEXAS)
|
From page 45... ...
Recommendation. The Department of Defense should rank the threat levels of all known harmful agents and exposure pathways based on the dimensions of harm (e.g., health consequences, the number of personnel affected, the time to consequences)
|
From page 46... ...
However, this is rarely the case. Total exposure assessments that include time and activity patterns and microenvironmental data have revealed that an exposure assessment is most valuable when it provides a comprehensive view of exposure pathways and identifies major sources of variability and uncertainty.
|
From page 47... ...
This concept is illustrated in Figure 2-1, which shows that an exposure characterization is based on both concentration information and time histories of the exposed population. The standard approach to assessing exposure is to use the model equations proposed by Duan (1982~.
|
From page 48... ...
The magnitude and relative contribution of each exposure route and environmental pathway must be considered in an assessment of total human exposure to a potentially harmful agent to determine the best approach for reducing exposure. Exposure assessments of deployed forces would require that the following steps be taken: .
|
From page 49... ...
CHARACTERIZING EXPOSURES All Many Q z Few None Cation /Minor Casualty Minutes Hours Months Years Time to effect FIGURE 2-2 The dimensions-of-harm scale. 49 /1 Consequence ~ Cancer cluster — J / eKM~ .§ /~R could be based on an index of hazard, such as the dimensions of harm developed for the Deployment Toxicology Research and Development Master Plan (Figure 2-2)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.