III. ASSESSMENT OF POTENTIAL HEALTH EFFECTS FROM DU IN THE GULF THEATER, 1990-1991
For DU which enters the body, initial estimates of the radiation dose were derived from "worst case," computer-modeled scenarios in which an Abrams "Heavy Armor" model was struck and its DU armor panels penetrated by a 120mm DU round. The results of one round were doubled to represent the number of penetrations that posed a "worst case" exposure in the Gulf (several M1A1s were hit twice by DU rounds, but no penetrations of their DU armor occurred). Such a "DU-on-DU" penetration would produce levels of DU aerosolization and spalling (spattering of liquified metal) exceeding those that actually occurred during the Gulf War, and therefore result in higher estimates of crew intakes of DU than occurred.
Soldiers involved in such a hypothetical scenario, and who did not retain any DU fragments, would receive an effective dose equivalent of approximately 0.96 rem (see Section III.B.1.c). This radiation dose is less than one-fifth the annual occupational limit, and is well below the level known to cause adverse health effects in people.
Health effects assessments for 13 identified exposure events (shown in Table 1) are being prepared that describe the activities of the participants, specify the sources of potential DU exposure, and estimate the dose from inhalation, ingestion and wound contamination, as appropriate for each exposure category. These assessments also review the current understanding of health effects associated with DU, and provide descriptions of the health risks in plain language. Most of those studies are currently in progress and will be published in about one year. In the meantime, the circumstances of some of the more significant exposure incidents are described (Tab G) so veterans involved in these activities will be able to recognize and understand events that may have exposed them to DU. The veterans can then obtain information about possible health effects, and be advised as to what medical services are available to them.
A. Overview of Participants in Exposure Scenarios
As Table 1 shows, Gulf War personnel were exposed to DU in a number of ways. Some US combat vehicles were mistakenly destroyed or damaged by US tanks using DU sabot rounds. Personnel worked inside US vehicles contaminated with DU fragments and particles. Several accidental tank fires and an ammunition explosion and fire at Camp Doha, Kuwait in July 1991, resulted in DU rounds being burned, oxidized, or fragmented, which created potential exposure hazards to troops operating in the vicinity. Other troops entered Iraqi armor disabled by DU. Determining the medical consequences of these exposures, if any, requires a systematic, scientifically sound evaluation.
The first step in assessing the health risks from DU was to identify the potential exposures that took place, and then determine the essential facts of each event. This required an aggressive, thorough, and focused investigation that relied on hundreds of eyewitness interviews and thousands of pages of official and unofficial documents, records, reports, memos, and personal diaries and photographs. Information developed during this process was analyzed and synthesized to produce a detailed picture of events of concern.
The exposure scenarios observed during ODS/DS and in months following, were categorized into three levels based on the activities of the soldiers involved, and the resulting potential for direct contact with DU. These three exposure levels provided a prioritized approach to describing and evaluating the potential exposures that occurred:
Level I - Soldiers in or near combat vehicles at the time these vehicles were struck by DU penetrators, or who entered vehicles immediately after they were struck by DU munitions. These soldiers could have been struck by DU fragments, inhaled DU aerosols, ingested DU residues, or had DU particles land on open wounds, burns, or other breaks in their skin.
Level II - Soldiers and a small number of DoD civilian employees who worked in and around vehicles containing DU fragments and particles (mostly friendly fire wrecks). These soldiers may have inhaled DU residues stirred up (resuspended) during their activities on or inside the vehicles, transferred DU from hand to mouth, thus ingesting it, or spread contamination on their clothing. Soldiers who were involved in cleaning up DU residues remaining on Camp Dohas North Compound after the July 11, 1991, explosion and fires are also included in this group.
Level III - An "all others" group whose exposures were largely incidental and very brief. This group includes individuals who entered DU-contaminated Iraqi equipment, troops downwind from burning Iraqi or US equipment struck by DU rounds, or personnel downwind from burning DU ammunition, such as occurred at Doha during the July 11 fire. While these individuals could have inhaled airborne DU particles, the possibility of receiving an intake high enough to cause health effects is extremely remote.
To date, 13 categories of possible DU exposure have been identified and classified within the three levels as shown in Table 1.
Substantial research has been conducted to determine the detailed exposure scenarios for participants in the 13 categories; and to perform assessments of the dose and health risk using a quantitative risk assessment process. The activities of many of the Level I, II, and III participants have been reviewed to develop the exposure scenarios. The US Armys Center for Health Promotion and Preventive Medicine (CHPPM) has reviewed existing test data on DU exposures and releases, and is developing dose estimates (chemical and radiological) for Level I exposures. Level I exposures are being addressed first, because these veterans probably received the highest exposures. Results of preliminary dose and risk assessments are reported below.
B. Level I Exposures (Friendly Fire)
Eight friendly fire incidents involving US M1A1s destroying or damaging occupied US-crewed vehicles with DU munitions occurred during the Gulf War. These incidents (distinct from non-DU friendly fire incidents or cases where friendly vehicles were evacuated and then deliberately destroyed to prevent their capture) resulted in the contamination of six M1/M1A1 tanks and 15 Bradley Fighting Vehicles. Another M1A1 was hit by a large shaped-charge round, believed to be a Hellfire missile fired from an Apache helicopter, that ignited an on-board fire. This incident is described in the "Tank Fires" Section (Tab J). Darkness and low visibility caused by heavy rains, sandstorms, etc., were major contributing factors in all of these incidents.
Figure 6. M1A1 Lost to Friendly Fire
In most cases, owing to battlefield confusion, soldiers manning the targeted vehicles initially believed that the Iraqis had fired the shots that penetrated their armor. The distinctive radioactive trace that DU leaves on the entrance and exit holes allowed a team of battle damage assessment experts to determine (after the fact) which vehicles had been hit by DU sabot rounds fired from Abrams tanks. After-action investigations and word-of-mouth reporting among the units involved generally resulted in the affected soldiers learning that they had been victims of friendly fire. Not all of these soldiers, however, were aware of the potential health effects associated with DU. Therefore, the investigation into the exposures resulting from friendly fire incidents is being accompanied by an effort to identify, locate, and contact all surviving soldiers who were in or on vehicles at the time they were penetrated by DU rounds.
As the spear-point of the ground campaign, US armored crews were often forced to make very rapid "friend or foe" decisions, where failure to engage could allow enemy gunners to take a first, fatal shot. Inevitably, given the swirling meeting engagements and close-in fights that erupted between friendly and enemy units, tragic misidentifications occurred. A total of 21 US combat vehicles (6 Abrams tanks and 15 Bradley Fighting Vehicles) were struck by 120mm DU sabot rounds fired from US M1A1 tanks. Some of these vehicles were struck once, others several times. Based on typical manning configurations for the Abrams tanks (four crew members) and Bradleys (five to nine crew members depending on configuration), as well as information gathered from veterans, an estimated 113 soldiers were on board these combat vehicles at the time they were struck by DU penetrators. Table 3 lists the individual systems struck by DU and their estimated manning (see Tab H for a description of each friendly fire incident). Reports have suggested that at least one vehicle was struck initially by enemy fire, evacuated, and subsequently struck by a DU round. If these reports are verified, the numbers reported in Table 3 may decrease.
Table 3. Summary of US Vehicles Hit by DU Tank Rounds
|Estimated Soldiers Onboard
|A-24, A-31, & A-22
|B-21, B-26, B-33, D-21 & D-26
|B-66, B-22, A-14, A-31 & A-33
|C-11, C-22 & C-23
|HQ-55 & HQ-54
Level I soldiers, injured or not, were in or around combat vehicles at the time they were struck by DU sabots, or immediately afterward. Besides the embedded fragments from wounds, these individuals may have inhaled DU aerosols generated by fires or by the impact of the DU projectile penetrating the target. The friendly fire incident summaries in Tab H describe the circumstances under which Level I soldiers were mistakenly targeted by US tank crews.
1. Soldiers in Vehicle On Impact
a. Summary of Activities
Armor crewmen and the "dismount" infantry transported in M2/M3 Bradley Armored Fighting Vehicles supplied the offensive striking power for Operation Desert Storm. US armored and mechanized infantry units counted on the speed, mobility, and firepower of their Abrams and Bradleys to maintain a rapid rate of advance while engaging and neutralizing enemy formations standing between Coalition troops and their objectives.
b. Hazard Identification
Table 4 shows possible combinations of personnel location, form of contamination, and route of exposure for Level I vehicle occupants. Additional details of the scenarios and assessments will be contained in the CHPPM exposure and health risk assessment report when published. Occupants of the vehicles were subjected to wounds from flying fragments, inhalation of airborne soluble and insoluble DU, ingestion of soluble and insoluble DU residues by hand-to-mouth transfer, and contamination of wounds by contact with contaminated clothing and vehicle interiors.
Table 4. Potential Hazards to Occupants of Struck Vehicles.
|Route of Exposure
|Inside or Outside the Vehicle
|Metal Fragment Oxides
Figure 7. Bradley Fighting Vehicle
Depleted uranium strikes on the exterior of an Abrams differ from those on Bradleys. The Abramss thicker armorreinforced at the turret and flanks by DU panels inserted between regular steel armoroffers much greater resistance to the impacting DU round than does the thinner, lighter weight aluminum-alloy skin of the Bradley. This results in a commensurate increase in DU aerosolization and fragmentation created at the point of penetration (and exit) and in the interior of the tank. The Bradley, in contrast, is less vulnerable to interior contamination because DU penetrators typically performed a "through-and-through" penetration of the Bradleys relatively thin armor, forming little aerosolization. During one incident, two DU rounds penetrated and flew through one Bradley and struck a second BFV standing twenty feet away. The range of likely exposures from a DU strike, therefore, can span a broad spectrum. Each incident needs to be carefully analyzed to draw any inferences about an individuals potential exposure. To develop data for an upper bound (worst-case) exposure which could result in the highest levels of contamination, the US Army Center for Health Promotion and Preventive Medicine (CHPPM) calculated the results from a DU sabot round penetrating the DU-protected portion of an Abrams. It should be noted that no such "DU on DU" penetrations occurred during the Gulf War. In several cases, however, Abrams tanks were hit more than once by DU rounds that penetrated non-DU portions of their armor. For this reason, the results from CHPPMs assessment of a single DU round penetrating an Abrams DU armor were doubled.
c. Assessment of Health Effects
Soldiers in or on vehicles struck by DU munitions were possibly exposed through four routes: direct wounding, inhalation, ingestion, and contamination of wounds. Wounded soldiers who retained fragments of DU are among the 33 veterans currently being evaluated in the DU Follow-up Program (described in Section IV.C). Additional details of this assessment are discussed in Tab N.
To estimate the intake, the amount of DU taken into the body by inhalation, ingestion, and wound contamination must be established. CHPPM considered available test data from fires and DU impacts with tanks and other combat vehicles. In addition, computer-modeling results were used to show the effects of a DU round penetrating DU armor. Since several M1A1s were struck by more than one DU round during the Gulf war, the results for a single DU round striking DU armor were established, then doubled to provide a high bound or "worst case" estimate. As noted, this "worst case" estimate exceeds known exposures in the Gulf, since no penetrations of DU armor by DU rounds occurred during the Gulf War. In addition, most of the combat vehicles struck by friendly fire DU rounds were Bradleys. DU penetrations of Bradleys produce much less aerosol, since the Bradleys relatively thin aluminum alloy armor offers significantly less resistance to a DU sabot than the Abrams thicker steel and DU armor. Therefore, the data for single and multiple penetrations of an Abrams Heavy Armor tank considerably overstates the likely exposures for occupants of lightly armored vehicles, i.e. Bradleys.
The preliminary results of the computer-modeling analysis of these inhalation scenarios show a total inhalation intake of DU oxide from two DU penetrations of the tanks crew compartment to be 52 milligrams (mg) maximum and 24 mg average. These intakes were converted to radiation doses of 0.96 rem maximum, and 0.46 rem average using the Lung Dose Evaluation Program (LUDEP), a lung dosimetry modeling program accepted by the ICRP.
The maximum radiation dose for Level I individuals is estimated to be 0.96 rem from two DU penetrators. For comparison, the average radiation dose to a member of the US population from background radiation is 0.3 rem per year. In other words, this maximum estimated exposure of 0.96 rem that clearly overestimates the likely doses in Gulf War participants is about the same as living in the United States for about three years and is less that one-fifth the annual dose limit for workers of 5 rems.
The chemical exposure based on the same dose scenario described above also assumes a 52 mg intake of DU particles for a 15 minute exposure. The 52 mg intake contains about 9 mg of soluble DU based on test data, indicating that up to about 17% of the airborne DU produced from impacts is soluble (ICRP Class D). For individuals who were in the vehicle when the DU penetrator did not enter the crew compartment, intakes of soluble DU are calculated to be much less, in the microgram range (14 mg).
The estimates of DU intake and resulting radiation dose were used because test data (although limited) on DU concentrations in the air and on surfaces inside an Abrams tank were available to support the analysis. Although considerable data gaps prevent a better analysis now, studies to fill those gaps are expected to be available to support analyses in the final version of this report. In addition, this modeling is undergoing scientific peer review before the report is finalized. Nonetheless, the radiation dose estimated here is less than one-fifth the annual limit for workers. A comparison of the estimated health risks from radiation with the possible chemical toxicity effects of soluble uranium oxides demonstrates that DUs heavy metal toxicity effects may be the primary concern.
2. Soldiers Entering Vehicles Immediately After Impact
a. Summary of Activities
Friendly fire incidents were usually witnessed by other US soldiers who in most cases served in the same platoon or company as the personnel in the struck combat vehicle. Typically these troops would rush to the aid of the stricken vehicles occupants to perform emergency first aid and rescue operations. The responding troops often entered damaged or destroyed vehicles moments after they had been hit, raising concerns that they may have been exposed to DU residues or oxides still airborne from impacts, or stirred up by the activities of survivors and rescuers inside and outside the vehicles.
b. Hazard Identification
The activities outlined above for people who entered immediately after impact indicate that members of this group were potentially exposed in three ways. Personnel outside the tank could be subject to DU through ingestion of DU by hand-to-mouth transfer of contamination from the outer surfaces of the vehicle. Troops who enter the struck vehicles could inhale DU aerosols from the initial impact or resuspended (stirred up) DU residues. They could also ingest DU through hand-to-mouth transfer, or have DU settle in breaks in their skin (burns, wounds, or scratches).
c. Assessment of Health Effects
The full assessment of exposure details, dose, and risk for this group requires additional work to fill data gaps on resuspension of DU, transfer from hand to mouth, and wound contamination. CHPPM is continuing to research these cases, and has identified needs for additional information from the affected veterans. Initial assessments indicate that these individuals are very likely to have received smaller exposures than those who were in the vehicles when struck.
C. Level II Exposures
Once the crews and other injured personnel had been evacuated from the scene, Explosive Ordnance Disposal (EOD) teams, Battle Damage Assessment Teams (BDAT), Radiation Control (RADCON) teams and salvage and/or maintenance personnel converged on the damaged equipment. They removed munitions, personal weapons, and sensitive or salvageable equipment, surveyed the damage and surrounding area, and prepared the damaged vehicles for transport to a salvage depot in Saudi Arabia. At the salvage depot, troops from the 144th Service and Supply Company, unaware of the potential DU hazard, often worked inside the wrecked vehicles to salvage them or prepare them for destruction and/or burial.
In addition to six Abrams and 15 Bradleys knocked out in friendly fire incidents, several other tanks were damaged or destroyed by accidental non-combat fires (see Tab J for an accounting of vehicles sustaining accidental fires). These vehicles were contaminated by "cook-offs" of their on-board DU ammunition (typically 37 rounds per tank). As such, they required essentially the same decontamination as vehicles lost to friendly fire.
Figure 8. RADCON Personnel Atop M1A1 Hulk.
EOD and RADCON personnel also played key roles in responding to the post-war (July 11, 1991) Camp Doha motor pool fire in which three M1A1 tanks uploaded with M829 DU sabot rounds were destroyed, as well as several hundred DU rounds stored nearby. Cleanup efforts in Camp Dohas motor pool area (the North Compound) also exposed several hundred troops to residual DU contamination in the vicinity of the burned tanks and ammunition conexes (see Tab I for a description of the Doha fire and cleanup). EOD personnel also entered DU-contaminated enemy combat vehicles with greater frequency and duration than other troops. These activities exposed the troops involved to contact with "resuspended" (stirred-up) DU particles, oxides, and residues, albeit at a much lower level than the Level 1 cases. These exposures could take the form of inhalation and/or ingestion of DU (especially during hand-to-mouth transfer). A more complete discussion of Level II activities and practices can be found at Tab G.
D. Level III Exposures
This category includes individuals who incurred relatively fleeting exposures from climbing on or entering DU-exposed US or Iraqi combat vehicles to remove equipment or "trophy hunt" for souvenirs. It also includes personnel exposed to the smoke from burning tanks containing DU rounds. Several such incidents occurred during and after the War; the most notable being the Camp Doha, Kuwait, motor pool fire. In addition to personnel who are included in the Level II categoryinvolved in cleaning up the North Compoundhundreds of additional troops may have received short-term exposure to the smoke from burning DU munitions stored in tanks or conexes. It is probable that some DU particles were entrained in the smoke that drifted over the soldiers who had evacuated to the southern tip of the base. A more complete discussion of Level III activities and practices can be found at Tab G.
E. Other Activities Under Investigation But Not Yet Categorized
The Office of the Special Assistant is often contacted by veterans who wish to report incidents that they believe could have exposed them to DU contamination. The incidents they describe are often isolated or unique events for which the available information is largely anecdotal. Each of these reports is investigated; in the following cases, however the Office of the Special Assistant cannot conclusively state, based on the available evidence, that DU exposures did or did not take place. Hence, they remain under investigation and have not been categorized. A more detailed description of these accounts is contained in Tab G after Level III Exposures.
Several veterans have reported welding DU armor panels onto the frontal turret armor of M1A1 tanks during refit operations to bring the tanks up to a higher survivability standard. Program managers, a senior metallurgist, and other personnel involved in the M1 refit program have disputed these claims, saying the panels in question were regular steel armor. Although this allegation remains under investigation, the initial assessment is that DU was not involved.
2. Reported Ammo Truck Explosion
A veteran reported seeing a US ammunition truck explode in the area of the 1st Infantry Division on the third or fourth day of the ground war. According to the veteran, a mixed load of high explosive and DU rounds exploded. Other soldiers and officers recalled an incident where a truckload of 155mm rounds or charges exploded after the trucks brakes caught fire and its driver (who apparently escaped injury), drove the truck into the desert to reduce the hazard to other soldiers. Although the available evidence suggests that DU rounds were not involved, information regarding this incident is still being sought.
3. Airmen Responding to A-10 Crash
An A-10 aircraft crashed and burned while trying to recover at King Khalid Military City (KKMC) in northern Saudi Arabia. The crash could have exposed emergency response personnel (firefighters, security policemen, rescue personnel) to smoke and DU oxides from burning 30mm DU rounds uploaded on the A-10. In addition, cleanup crews might have been exposed to DU fragments, residues, and oxides. This case is under investigation.
4. "Hot Gun" Response for A-10 Aircraft
30mm DU rounds sometimes misfired in the A-10s GAU-8 cannon. These "hangfires" would have to be cleared and removed from the gun barrel, potentially exposing ground crews to airborne DU. These incidents are still being identified and investigated by this office.
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