Blue Water Navy Vietnam Veterans and Agent Orange Exposure (2011) / Chapter Skim
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5 EXPOSURE ROUTES AND MECHANISMS
5 EXPOSURE ROUTES AND MECHANISMS
Pages 87-108
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From page 87... ...
The committee considered the environmental fate and transport of Agent orange–associated TCDD from aerial and riverbank spraying in combination with activities of Navy personnel and ground troops, as described in Chapter 4, as its starting point for its assessment of exposure opportunity. In the most general terms, environmental distribution 87
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From page 88... ...
It should be noted that there are Blue Water Navy personnel who qualify as Brown Water Navy personnel as a result of their ships' locations or activities but have not yet been so designated by the Department of Veterans Affairs (VA) , although they may be in the future.
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From page 89... ...
to include exposure pathways relevant to Blue Water Navy personnel (for example, shipboard treated water and accidental contact from coastal spraying)
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From page 90... ...
In the sections below, the committee examines the environmental pathways that could result in exposure of ground troops, Brown Water Navy personnel, and Blue Water Navy personnel to Agent Orange– associated TCDD from two major herbicide sources: aerial spraying and riverbank spraying. The committee discusses plausible pathways of exposure to TCDD in each environmental medium (air, soil and plants, freshwater, freshwater sediment, fish and other foods, and marine waters)
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From page 91... ...
Blu Wtr = Blue Water Navy personnel, Br Wtr = Brown Water Navy personnel, and Gr = ground troops.
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From page 92... ...
Inhalation and dermal routes of exposure are considered, as well as ingestion, which is a plausible exposure route when aerosols and particles that enter the mouth are swallowed. Inhalation Ground troops and Brown Water Navy personnel There is some information on ground troops and Brown Water Navy personnel on which to base conclusions regarding inhalation exposure plausibility (IOM, 2003, 2008)
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From page 93... ...
Therefore, although the extant information, based on modeling efforts, reveals variability in the extent of area over which troops and personnel may have plausibly inhaled Agent Orange–associated TCDD, common sense dictates that inhalation exposure of ground troops and Brown Water Navy personnel to Agent Orange spray drift or volatilized TCDD is plausible. 1 Blue Water Navy personnel The VA has determined that Blue Water Navy personnel do not have a presumption of exposure; this implies that their opportunity for herbicide exposure by aerial drift from spraying of herbicides in Vietnam was considered to be insignificant.
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From page 94... ...
The committee considers inhalation exposure via aerial dumping of herbicides to have been very rare. Ingestion Ground troops and Brown Water Navy personnel Ground troops and Brown Water Navy personnel might be expected to have some potential for ingestion of aerosols via inhalation followed by mucociliary transport and swallowing.
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From page 95... ...
indicate that some ground troops may have been in an area that could receive herbicide drift. Therefore, the committee concludes that some ground troops had the potential for direct dermal contact with herbicide-spray drift and could not rule out this pathway for Brown Water Navy personnel.
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From page 96... ...
Therefore, the committee determined that it is plausible that ground troops and Brown Water Navy personnel would have some opportunity for inhalation exposure to TCDD after aerial herbicide spraying and Agent Orange deposition on plant surfaces and soils. Blue Water Navy personnel Although volatilization of TCDD from plant surfaces and soil is possible and could result in the atmospheric transport of the chemical, the committee believes that -- given the potential for photodegradation, dust washout in rain, and dispersal over long distances -- it is unlikely that Blue Water Navy personnel would be exposed to Agent Orange– associated TCDD via this mechanism and route of exposure.
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From page 97... ...
Blue Water Navy personnel The committee could not identify a plausible exposure pathway for ingestion of contaminated soil by Blue Water Navy personnel who were aboard ships at sea. Dermal Ground troops and Brown Water Navy personnel Direct contact of ground troops and Brown Water Navy personnel with contaminated soil and sprayed foliage is possible.
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From page 98... ...
Blue Water Navy personnel Blue Water Navy personnel would not be expected to come into direct or indirect contact with contaminated Vietnamese soils or foliage while aboard ships at sea. Therefore, the committee concluded that there is no potential for exposure to Agent Orange–associated TCDD for Blue Water Navy personnel via this exposure pathway and route.
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From page 99... ...
Thus, exposure of the two populations to Agent Orange– associated TCDD via ingestion of freshwater is plausible. Blue Water Navy personnel Blue Water Navy ships generated their own potable water from marine water (discussed later)
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From page 100... ...
Dermal Ground troops and Brown Water Navy personnel As in the case of exposure to contaminated surface waters, ground troops and Brown Water Navy personnel may have had the opportunity for direct contact with contaminated sediments when walking along riverbanks, wading across streams, or engaged in other activities in inland waters, such as swimming. Because sediments can be transported for some distance in water with a strong current, it is possible that military personnel were exposed to TCDD-contaminated sediments even when they were not near sprayed areas.
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From page 101... ...
. Ingestion Ground troops and Brown Water Navy personnel The opportunity for exposure to TCDD-contaminated food varied considerably among military personnel stationed in Vietnam.
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From page 102... ...
Blue Water Navy personnel on ships that docked in Vietnam to take on food, including Vietnamese food, would meet the criteria for a presumption of herbicide exposure if they stated they went ashore while the ship was docked. The committee heard conflicting reports on whether fishing from Blue Water Navy ships occurred.
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From page 103... ...
Although no specific information on Brown Water Navy personnel was available, they might have been exposed to Agent Orange–associated TCDD in marine waters if they were operating near the mouth of a river that was contaminated or if their ship moved from brown water to blue water and they were in contact with the water. Blue Water Navy personnel The committee was told that personnel on larger ships operating off the coast did not engage in marine swimming, but it was within the discretion of the commanding officer of each ship to permit it.
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From page 104... ...
The issue of distillation of marine water is important because of the finding by the committee that prepared the 2008 Veterans and Agent Orange update (IOM, 2008) that Blue Water Navy veterans could have been exposed to TCDD via contaminated potable water.
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From page 105... ...
Questions about the engineering systems used to produce potable water on Blue Water Navy ships and their effect on concentrations or enrichment of Agent Orange–associated TCDD increase the uncertainty in the importance of this exposure route. CONCLUSIONS The committee identified several plausible exposure pathways and routes of exposure to Agent Orange–associated TCDD in the three populations, including Blue Water Navy personnel (see Figure 5-1)
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From page 106... ...
2009. Assessing exposure to allied ground troops in the Vietnam War: A comparison of AgDRIFT and Exposure Opportunity Index models.
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From page 107... ...
2008. Further definition of Vietnam "Blue Water" versus "Brown Water" service for the purpose of determining Agent Orange exposure.
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