Review of the Toxicologic and Radiologic Risks to Military Personnel from Exposures to Depleted Uranium During and After Combat (2008) / Chapter Skim
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8 Evaluation of the Army's Capstone Report
8 Evaluation of the Army's Capstone Report
Pages 96-123
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From page 96... ...
EXPOSURE ASSESSMENT The Capstone Report estimated the exposure of military personnel to DU from "friendly-fire" incidents in the first Gulf War. The assessment used the results of the Capstone DU-aerosols study (Parkhurst et al.
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From page 97... ...
: an Abrams tank with conventional armor, a Bradley fighting vehicle with conventional armor, and an Abrams tank with DU armor. In addition, one shot was fired into an operational Abrams tank with DU armor that had an operating ventilation system.
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From page 98... ...
The biokinetic models used in the Capstone Report reflect scientific consensus based on years of studies of animals and on human data where possible. Capstone scientists programmed special applications of the models for the human respiratory tract, the gastrointestinal tract, and uranium systemic biokinetics.
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From page 99... ...
Level I Exposures The primary focus of modeling level I exposures was to provide estimates of DU inhalation exposure to personnel in an Abrams tank or a Bradley fighting vehicle. Modeling of the level I inhalation exposures in a vehicle is a matter of determining the aerosol source characteristics in the vehicle (DU concentration, particle size, and solubility)
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From page 100... ...
found that 105-mm penetrators striking metal targets produced uranium oxides as 75% triuranium octaoxide and 25% uranium dioxide in particles that had an aerodynamic equivalent diameter (AED) of about 2.5-3 µm and of which about 50% were in the respirable size range.
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From page 101... ...
2004a) , the peak concentrations in the Abrams tank was around 107 µg/m3, which was used in the committee's analysis as the starting point.
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From page 102... ...
For the unventilated Bradley fighting vehicle, the independent estimates are about 3 times larger than the Capstone estimates. (However, the initial quantity of DU measured in the Capstone Report for Bradley vehicles was only about one-third the initial value assumed in these independent re-estimations.)
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From page 103... ...
100 Abrams Unventilated Abrams Ventilated Bradley Unventilated 10 Bradley Ventilated 1 0 0 20 40 60 80 100 120 Time (Minutes) FIGURE 8-1 Committee-predicted mass concentrations of DU in air in vehicles after impact.
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From page 104... ...
104 Risks to Military Personnel from Exposure to Depleted Uranium TABLE 8-3 Committee's Estimated Time-Integrated Concentrations of DU in Air for Various Conditions after Impact (mg-h/m3) Start Stop Abrams Bradley Time Time Unventilated Ventilated Unventilated Ventilated Large Respirable Particles A: Exit 1 min 0 1 39.6 25.9 38.5 27.2 B: Exit 5 min 0 5 99.1 38.6 88.9 43.2 C: Exit 60 min 0 60 115.7 38.8 98.9 43.5 D: Exit 120 min 0 120 115.7 38.8 98.9 43.5 E: First responder 5 15 18.7 0.3 11.9 0.5 Small Respirable Particles A: Exit 1 min 0 1 45.0 29.0 43.8 30.5 Small Respirable Particles B: Exit 5 min 0 5 171.5 50.7 148.6 58.5 C: Exit 60 min 0 60 437.6 51.6 262.4 60.4 D: Exit 120 min 0 120 438.9 51.6 262.4 60.4 E: First responder 5 15 173.8 1.7 99.6 2.7 TABLE 8-4 DU Intakes Independently Estimated by Committee for Five Capstone Level I Exposure Scenarios Abrams Bradley Scenario Unventilated Ventilated Unventilated Ventilated Total Intake (mg)
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From page 105... ...
Hence, durations of exposure in perforated vehicles particularly need to be monitored for these personnel. The primary exposure pathways are the same for level II and level III personnel; however, the time spent by personnel in the vehicles is different.
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From page 106... ...
This value was also used as a minimum for the level I inhalation exposures described above. For military personnel involved with postbattlefield conditions, a breathing rate associated with moderate levels of activity is assumed to be 1.2 m3/h.
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From page 107... ...
They estimated that there was a 90% probability that the amount ingested would be 0.3-30 mg/h for level II and 0.26-3.8 mg/h for level III exposures (effective-dose accumulation rates of 2 × 10−5 to 2 × 10−3 and 2 × 10−5 to 3 × 10−4 rem/h, respectively)
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From page 108... ...
2005) identifies median peak renal uranium concentrations predicted for each exposure scenario in each vehicle configuration tested for level I personnel and for inhalation and hand-to-mouth ingestion for levels II and III personnel.
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From page 109... ...
b The committee interprets "not likely to become ill" to mean may exhibit low-level transient renal effects. c The committee interprets "may become ill" to mean may experience clinical symptoms of renal dysfunction and require medical attention.
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From page 110... ...
1990 1 8.4 0.87 -- 1 7.4 0.76 -- 1 6.0 0.62 -- 1 6.0 0.62 -- a Modeled estimates. b Clinical symptoms of renal dysfunction: +++ = severe; ++ = protracted biochemical indicators of renal dysfunction; + = transient biochemical indicators of renal dysfunction; -- = no detectable effects.
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From page 111... ...
report also noted transient renal effects at renal concentrations of 1 µg/g and further noted that the trend after chronic exposure is toward greater renal effects with lower renal concentrations, possibly as low as 0.1 µg/g. Table 8-8 presents the predicted peak renal uranium concentrations for level I personnel in context with published human data, and Table 8-9 presents predicted renal uranium concentrations for level II and level III personnel from the Capstone Report.
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From page 112... ...
2005 exits in 1 h Level I: Bradley vehicle; conventional armor, no 330 3.5 REG 1 Not likely to become illc Guilmette et al. 2005 ventilation; crew exits in 1 h Level I: Abrams tank; DU armor, no ventilation; crew 280 3.0 REG 1 Not likely to become illc Guilmette et al.
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From page 113... ...
2005 responders Level I: Bradley vehicle; conventional armor, no 99 1.4 REG 0 No detectable effectsd Guilmette et al. 2005 ventilation; first responders Level I: Abrams tank; DU armor, no ventilation; crew 250 1.1 REG 0 No detectable effectsd Guilmette et al.
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From page 114... ...
2005 responders Level I: Abrams tank; DU armor, ventilation operating; 10 0.05 REG 0 No detectable effectsd Guilmette et al. 2005 crew exits in 1 min a Biochemical indicators of renal dysfunction: +++ = severe with clinical symptoms; ++ = protracted; + = transient; -- =, no detectable effects.
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From page 115... ...
With a lower REG-0 range, people in those exposure categories may exhibit transient renal effects, including excretion of albumin and low-molecular-weight proteins; time of recovery from these effects depends on excretion of the uranium. The committee agrees that for all other level I personnel exposures and for all level II and level III exposures modeled, detectable renal effects are not likely to occur.
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From page 116... ...
Lifetime Cancer-Mortality Risk Estimate Increased mortality based on organ-specific cancer risk coefficients of alpha-emitting radionuclides was used in the Capstone Report to estimate the risk of fatal cancer in selected organs. Biokinetic-model calculations of organ doses multiplied by organ-specific cancer risk factors estimate that the cancer risk posed by internally deposited DU is primarily to the lungs, which are relatively sensitive organs.
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From page 117... ...
As noted earlier in this chapter, the committee found the Capstone Report's radiation-dose estimates to be reasonable predictions. The committee's estimates of level I exposures for the unventilated Abrams tank and Bradley fighting vehicle with conventional armor and the Capstone Report's estimates agree to within a factor of about 2 (see Table 8-5)
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From page 118... ...
Hence, for the worst-case level I exposure scenario of 2 h in a twice-perforated Abrams tank with DU armor and no ventilation, the estimated median increased risk of fatal lung cancer would be 0.9% (one in 111) , which is not an insignificant cancer risk.
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From page 119... ...
Level II and Level III Risk Estimates The Capstone Report is limited in not providing estimates of fatal cancer risks for potential exposure scenarios for level II or level III personnel. Such risks are difficult to predict because they depend on the duration and level of exposure.
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From page 120... ...
Uncertainty of Chemical Carcinogenicity of Uranium The cancer risk estimates in the Capstone Report were calculated on the basis of radiation doses associated with DU exposure and did not take into account chemical genotoxic effects of DU. That is consistent with historical approaches and recent reports, such as that of the Royal Society (2001)
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From page 121... ...
The committee had difficulty in verifying the REG-0 classification range for renal effects presented in the Capstone Report; it had questions about the interpretation of some studies and the relevance of the exposure in the studies to that encountered in military settings. Human exposure data suggest that transient proteinuria and albuminuria have occurred in humans with renal uranium concentrations as low as 1 µg/g.
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From page 122... ...
On the basis of the exposures provided in the Capstone Report, the committee agrees with the radiologic-cancer risk estimates calculated in the Capstone study for the level I inhalation-exposure scenarios. The Capstone Report does not provide estimates of radiologic-cancer risks for levels II and III personnel.
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From page 123... ...
• If Gulf War level II personnel who had several hours of unprotected exposure to DU in perforated vehicles can be identified, they should receive additional health monitoring.
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