Strategies to Protect the Health of Deployed U.S. Forces Detecting, Characterizing, and Documenting Exposures (2000) / Chapter Skim
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4 Environmental and Exposure Pathways
4 Environmental and Exposure Pathways
Pages 68-85
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From page 68... ...
ENVIRONMENTAL TRANSPORT, ENVIRONMENTAL PATHWAYS, AND EXPOSURE ROUTES Exposure to CB agents is defined in terms of contact between the agent and the exterior surfaces of the body. Contact points include skin 68
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From page 69... ...
Exposure assessments often rely implicitly on the assumption that exposure can be linked, by simple parameters, to ambient concentrations in air, water, and soil. However, total exposure assessments also include time and activity patterns and microenvironmental data to provide a comprehensive view of exposure pathways and identify major sources of uncertainty.
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From page 70... ...
Defining and Ranking Required Information Sources and emissions factors, transport and transformation processes, exposure scenarios and pathways, and routes of intake or uptake have all been identified as important components of an exposure assessment. The exposure characterization process can be short term (over a period of hours or days)
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From page 71... ...
However, the time of onset of health effects associated with an exposure also strongly affects the time resolution required to describe the effects of the exposure. For some warfare agents and many nonwarfare toxic chemicals, the number and duration of peak concentration must be estimated.
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From page 72... ...
This requires a combination of intelligence information on the potential use of the agents, rapid and accurate observation of delivery ordnance combined with visual observation of an aerosol cloud (if possible) , and detection of agent concentrations in plumes or on surfaces.
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From page 73... ...
Yet much of the data now collected on environmental contaminants cannot be synthesized into any understandable form because of the lack of a comprehensive framework for evaluating chemical transport, transformation, and interaction over multiple media. For a comprehensive framework, DoD would have to take the following steps: · Document and monitor geographic and time trends in exposures to chemicals and biological substances through multiple media (air, water, soil)
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From page 74... ...
Standard models for estimating the time and space distribution of CB agents to the atmosphere are Gaussian statistical solutions of the atmospheric diffusion equation (Henna et al., 1982; Pasquill, 1961; Turner, 1970~. Numerous computer programs are available and many papers have been published describing algorithms for assessing the dispersion of point, line, and volume air pollution sources.
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From page 75... ...
The behavior of chemicals and biological agents in surface waters is determined by two factors, the rate of physical transport in the water system and chemical reactivity (Schnoor, 1985~. Physical transport processes are dependent to a large extent on the type of body of water (e.g., ocean, sea, estuary, lake, river, or wetland)
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From page 76... ...
The transport of outdoor contaminants to indoor environments, and the resulting changes in contaminant concentrations, must be determined to assess potential exposures. For example, the relationship between the indoor and outdoor concentrations generally depends on the ventilation rate and the rate of removal in the building.
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From page 77... ...
Indoor environments offer some protection from agents that are present in outdoor air as aerosols or as highly reactive gases. Larger aerosols do not penetrate the building envelope as fast as gases.
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From page 78... ...
For example, most chemical warfare agents have lethal or incapacitating effects at much lower concentrations for inhalation than for dermal contact. For CB agents, the exposure medium and the exposure activity tend to be strongly associated with the potential route of intake.
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From page 79... ...
Direct Exposure Pathways Exposures to CB agents at high doses or high dose rates are often associated with a single, relatively simple pathway. For example, the highest intake of chemical warfare agents released to air will be through direct inhalation or through eye contact.
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From page 80... ...
POTENTIAL EXPOSURES, CLASSIFIED BY TIME SCALE AND PLAUSIBILITY Exposures to drugs, chemical agents, biological agents, and combinations of agents have been suggested as possible causal factors of medical symptoms among Gulf War veterans (DoD, 1994~. The number of harmful agents to which deployed forces can potentially be exposed is very large.
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From page 81... ...
The climate was characterized by temperature extremes in a sand/dust environment, and the threat of CB warfare was always present. Some of the chemical and biological exposures of concern involved Leishmaniasis, vaccines, desert sand, depleted uranium, paints and coatings, pesticides, petroleum vapors, and oil-well fires (NIH, 1994~.
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From page 82... ...
Iran-Iraq War and Gulf War threat. Direct poisoning of Persian Gulf oil fires.
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From page 83... ...
Troops were also vaccinated against expected infectious diseases, as well as against two biological warfare agents, anthrax and Botulinum toxin. Exposures to petroleum vapors, solvents, and combustion products were common during the Gulf War deployment.
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From page 84... ...
. However, mixed exposures to biological agents and chemicals or CB agent exposures combined with exposures to intense noise and stress have not yet been addressed in any substantive way.
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From page 85... ...
Interactions among these substances can be cumulative, synergistic, or antagonistic. The risk assessment community has done very little research to provide exposure assessments of the combined health impacts of even two interacting agents.
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