C.  Level II Exposures

Once the crews and other injured personnel had been evacuated from the friendly-fire scene, Battle Damage Assessment Teams (BDAT), Explosive Ordnance Disposal (EOD), Radiation Control (RADCON), and salvage and/or maintenance teams converged on the damaged equipment. They removed munitions, personal weapons, and sensitive or salvageable equipment; surveyed the damage and surrounding area; and prepared damaged vehicles for transport to a salvage depot in Saudi Arabia. At the salvage depot, soldiers from the 144^th Service and Supply Company, unaware of the potential DU exposure, often worked inside the wrecked vehicles to salvage or prepare them for burial or shipment to the US. (Tab G., Section B. 5 discusses low-level waste disposal practices.)

Figure O-5.  RADCON personnel atop M1A1 tank hulk

EOD and RADCON personnel also played key roles in responding to the post-war Camp Doha motor pool fire, which on July 11, 1991, destroyed three M1A1 tanks loaded with DU rounds and several hundred DU rounds stored nearby. Cleanup efforts in Camp Doha's motor pool area (the North Compound) also exposed several hundred soldiers to residual DU contamination in the vicinity of the burned tanks and ammunition conexes. (Tab I describes the Doha fire and cleanup.) The DU exposures at Doha involved inhalation and/or ingestion routes of entry. (Tab G more completely discusses Level II activities and practices.)

DU contaminated a total of 31 combat vehicles (16 Abrams and 15 Bradleys) in the Gulf during 1990-1991. In addition to the 20 occupied combat vehicles hit by DU friendly fire (6 Abrams and 14 Bradleys), tank-fired DU rounds also struck 1 unoccupied Bradley. US tanks intentionally fired DU rounds into 3 unoccupied, immobilized Abrams to prevent their capture. Tank fires, causing some onboard DU rounds to "cook off," were responsible for contaminating the final 7 Abrams, including the 3 Doha tanks mentioned above. Whether contaminated by impacting DU rounds, or DU rounds that caught fire and exploded, these 31 vehicles all required essentially the same decontamination.

Personnel entering DU-contaminated equipment may have stirred up DU residues on the inside surfaces of the vehicles and this resuspended residue could have been inhaled. Personnel outside the vehicles could have inhaled DU resuspended from the outside surfaces or the surrounding soil. Personnel could have also inadvertently ingested DU from their hands or lips, or they could have nicked, scratched, or otherwise injured themselves and thereby contaminated wounds. Personnel in the different functional groups involved (BDAT, EOD, RADCON, LARs, Unit Maintenance, and 144^th Service and Supply Company) all experienced essentially the same types of conditions–vehicles and equipment contaminated with DU inside and out. Therefore, this assessment was performed as a single evaluation with adjustments as necessary for time spent in the vehicles, etc.

Of the three exposure routes (inhalation, ingestion, and wound contamination), inhalation and ingestion are the primary exposure pathways for Level II and III personnel. The inhalation exposure from resuspended DU residues inside or outside vehicles depends on the air concentration of the resuspended DU and the time the person spends in the resuspended DU. The inhalation exposure from smoke depends on DU concentration and the time spent in the smoke. Ingestion mainly comes from touching a DU-contaminated surface and then inadvertently touching the mouth; the amount ingested is usually a fraction of the amount on the hands. Wound contamination, as discussed in Section 3.3 of this appendix, was not evaluated further.

To make its assessments and avoid the uncertainty of modeling, USACHPPM reviewed data obtained during tests conducted under circumstances similar to the Gulf to identify useful data to estimate:

• the DU soil contamination as a function of the distance from a vehicle hit by DU munitions;
• the airborne concentrations of DU inside a re-entered vehicle struck by DU munitions;
• the outside airborne DU concentrations as a function of the distance from a vehicle struck by DU munitions; and
• the outside airborne DU concentrations as a function of the distance from a fire in a vehicle loaded with DU munitions.

USACHPPM then used data from these developmental tests^[587] to prepare a range of probable air concentrations and surface DU contamination levels that were derived from penetrations of the DU armor plate on an Abrams Heavy M1A1 main battle tank, which did not occur in the Gulf War. Air samplers, placed on test project personnel who entered the test area, provided air concentrations for the resuspended DU the workers encountered. The workers' activities included walking on and around the tank, entering the tank, and activities inside the tank. USACHPPM concluded that these activities represented Level II activities in the Gulf and that the DU air concentrations represented those encountered by Level II personnel. Samples collected by wiping the interior and exterior surfaces of the tank with paper (called wipe samples) provided surface DU contamination levels for estimating ingestion. Table O-2 lists the air concentrations and surface contamination levels USACHPPM used for the Level II estimates.

Table O-2 DU air concentration and surface contamination levels^[588]

The assessments focused on inhalation and ingestion during the re-entry of DU-contaminated vehicles, and inhalation and ingestion during activities around and near contaminated vehicles.^[589] Based on its review of the test data, USACHPPM concluded that a DU round penetrating DU armor produced 83 percent insoluble DU oxides (Type S) and 17 percent moderately soluble DU oxides (Type M), while DU involved in a fire produced oxides with a higher fraction of insoluble forms – 93 percent Type S and 7 percent Type M, and that these percentages properly represented the materials inside vehicles that were reentered.^[590]

USACHPPM recognized that Level II personnel experienced variable contamination levels, entry times, and exposure times that were only known in general. Therefore, USACHPPM elected to develop chemical intake and radiation dose factors based on one hour of exposure in a vehicle. This approach provided a set of nominal factors that could then be multiplied by the exposure time and number of vehicles entered to produce estimates for Level II intakes and radiation doses.

The inhalation estimates assume that the DU residue contained 7 percent Type M and 93 percent Type S material (characteristic of amounts inside a tank after a fire).

The ingestion estimates assume:^[591]

• the greatest DU contamination level (4,815 dpm/100 cm²) observed during Test 5A exists on the interior surfaces of the vehicle;
• the DU residue contained 17 percent Type M and 83 percent Type S material (characteristic of amounts inside a tank after penetration) to provide a conservative estimate of kidney concentration;
• DU surface contamination transfers to the mouth at a rate of 0.0001 m² per hour recommended by the Nuclear Regulatory Commission.^[592]

Table O-3 contains these factors for the estimated DU intake, the estimated amount transferred to the kidney (called kidney amount), the estimated kidney concentration (total uranium though the kidney divided by the kidney mass), and the estimated radiation dose (CEDE) for each hour of exposure. Table O-3 displays the factors for the contributions from soluble and insoluble DU for inhalation and for ingestion, as well as the totals for each route of exposure and for an individual. The kidney transfer factor represents the total amount of the initial DU intake that gets to the kidney. For inhalation, the kidney transfer factor was taken from the mathematical models used for estimating the kidney concentration. For ingestion, USACHPPM used the ICRP recommended factors for transfer of uranium from the intestines to the blood of 2 percent for soluble DU and 0.2 percent for insoluble DU and assumed that all of the DU that enters the blood gets to the kidney. They calculated the kidney content by multiplying each intake rate by the appropriate kidney transfer factor and then summing the results. For example, the kidney amount for inhaled, soluble DU would be:

= (intake rate, inhaled soluble DU) X (kidney transfer factor, inhaled soluble DU)

= (0.002 milligram in one hour of exposure) X (0.0642) = 0.00013 milligram in one hour of exposure transferred to the kidney.

Table O-3. Estimated chemical and radiation factors for one hour of exposure^[593]

Similarly, the DU kidney amount for inhaled insoluble DU, ingested soluble DU, and ingested insoluble DU were calculated using the corresponding intake rate and kidney transfer factors. To compare DU kidney concentrations with the 3 microgram of uranium per gram of kidney tissue guideline, USACHPPM calculated the kidney concentration in micrograms (�g) of uranium per gram of kidney tissue by multiplying the kidney amount by 1,000 to convert from milligrams to micrograms and then dividing by the nominal kidney mass of 310 grams according to the following equation.

For example, the kidney concentration from inhaled, soluble DU is 0.00042 microgram (�g) of uranium per gram of kidney tissue as calculated from:

= 0.00042 microgram (�g) of DU per gram of kidney tissue.

Intakes and doses for other Level II scenarios can be evaluated by multiplying the factor for one hour by the exposure time in a vehicle and the number of vehicles entered to estimate the total intake, kidney amount, kidney concentration and radiation dose. The estimates can be calculated for the total exposure, for each route of entry (inhalation or ingestion), or for the contribution from soluble and insoluble DU. For example, a member of the BDAT team who spent three hours in one vehicle would have an intake of 0.075 milligram (3 hours times 0.025 mg in one hour times one vehicle) from inhalation and 0.171 milligram (3 times 0.057 mg in one hour times one vehicle) from ingestion for a total of 0.246 milligram. That would produce kidney amounts of 0.00063 milligram (3 times 0.00021 mg) from inhalation and 0.00087 milligram (3 times 0.00029 mg) from ingestion for a total of 0.0015 milligram. The kidney concentration from that kidney content would be 0.002 microgram of DU per gram of kidney tissue (3 times 0.00067 microgram of DU per gram of kidney tissue) from inhalation and 0.0028 microgram of DU per gram of kidney tissue (3 times 0.00095 microgram of DU per gram of kidney tissue) for a total of 0.0048 microgram of DU per gram of kidney tissue. This kidney concentration is far below the 3 micrograms of uranium per gram of kidney tissue guideline and indicates that chemical effects would not be expected from this DU exposure. The corresponding radiation dose would be 0.0015 rem (3 times 0.0005 rem) from inhalation and 6 x 10^-6 rem (3 times 2 x 10^-6 rem) from ingestion for a total of 0.0015 rem. That radiation dose is much less than the guideline (0.1 rem in a year) for members of the public, indicating that no adverse radiation effects would be expected from this exposure. Readers can apply a similar process to estimate their own intakes and doses based on their own estimates of exposure time and number of vehicles entered.

Based on our interviews with Level II personnel and our analysis of their possible activities, we concluded that Level II personnel encountered some or all of the same group of contaminated vehicles consisting of 16 Abrams tanks (6 destroyed by friendly fire, 3 destroyed intentionally, 7 involved in fires) and 15 Bradleys (all involved in friendly fire incidents). Therefore, we also concluded that one person, exposed to all 31 vehicles, provided a very conservative estimate of the upper limit exposures for Level II personnel. We recognized that one person would not enter all 31 vehicles at the same time or in rapid sequence.

Generally, Level II personnel contacted one or more contaminated vehicles for periods of a few minutes to several hours. Based on interviews with many Gulf War veterans, we developed nominal exposure times ranging from one hour per vehicle for EOD personnel and LARs to three hours per vehicle for Unit Maintenance Personnel, BDAT, and 144^th Service and Supply Company personnel and gave them to USACHPPM. Table O-4 lists the exposure times for each Level II scenario.

Table O-4. Total estimated upper limit Level II DU intake and radiation dose (31 vehicles)^[594]

USACHPPM estimated intakes of total DU, soluble DU, and insoluble DU, DU kidney concentration, and radiation dose from inhalation and from ingestion for each of the Level II scenarios (Table O-4). They assumed that a member from each scenario contacted each of the 31 vehicles for the time established for the scenario. For example, this assumption means that a typical BDAT or Unit Maintenance soldier spent 3 hours in each of the 31 tanks. USACHPPM considered contact with all vehicles a very unlikely possibility in the Gulf, therefore these estimates provide a reasonable upper limit to DU intakes and doses.

USACHPPM's upper limit estimates of the chemical intakes and radiation doses (CEDE) for Level II personnel produced a total DU intake of 7.6 mg (2.3 milligrams from inhalation, 5.3 milligrams from ingestion), kidney concentration at 0.15 microgram of DU per gram of kidney tissue and radiation dose of 0.047 rem. The 2.3 milligrams of inhalation intake includes 0.2 milligram of soluble DU and 2.1 milligrams of insoluble DU. Both the total inhalation intake and its soluble portion are well below the 8 milligram and 40 milligram guidelines for kidney effects from inhalation of soluble DU.

The 5.3 milligram ingestion intake includes 0.93 milligram of soluble DU and 4.4 milligrams of insoluble DU. USACHPPM assessed the potential for kidney effects from the combined inhalation and ingestion intakes by comparing the DU kidney concentration with the 3 micrograms uranium per gram of kidney tissue guideline. They calculated a kidney concentration of not more than 0.06 microgram (�g) of DU per gram of kidney tissue from inhalation and 0.09 microgram (�g) of DU per gram of kidney tissue from ingestion for a total of 0.15 microgram (�g) of DU per gram of kidney tissue. The kidney concentration value of 0.15 microgram (�g) of DU per gram of kidney tissue is much less than the 3 micrograms (�g) of uranium per gram of kidney tissue guideline. Therefore, we conclude that these conservative results are well below the chemical toxicity guideline and that no health effects are expected from them.

USACHPPM estimated an upper limit, 50-year committed effective dose equivalent dose of 0.047 rem from inhalation and 0.0002 rem from ingestion for a total radiation dose of 0.047 rem. That radiation dose is about one-half the 0.1 rem in a year guideline for members of the public, and much less than our 5 rem limit. Therefore, no adverse health effects from radiation would be expected from these radiation doses.

Limited testing on some Level II personnel supports these assessments. After the April 13, 1991 tank fire (see Tab J), urine uranium concentrations for seven soldiers tested on April 15, 1991 were all below minimum detection limits. Tests on members of the 144^th Service and Supply Company of the New Jersey Army National Guard, which started in 1993, also produced urine uranium concentrations considered normal.

The fire and explosion on July 11, 1991 that engulfed the 2^nd Squadron Motor Pool potentially exposed hundreds of Army personnel to inhaled and ingested DU. The explosion and fire involved 660 M829 rounds that released DU residues to the air, or contaminated grounds and equipment, posing a potential exposure for personnel during the initial fire/explosion and subsequent assessment and clean up activities.

Because the Pacific Northwest National Laboratory (PNNL) had conducted many of the DU tests during the past two decades and developed safety and health guidelines for DU munitions usage, USACHPPM requested that PNNL perform detailed reviews and analysis of data from burn tests of DU munitions to access the possible chemical and radiation exposures to personnel at Camp Doha.

PNNL's investigators approached this task by determining the pathways, assessing the intake of DU oxides in the smoke, assessing the inhalation of DU oxides by recovery personnel, determining the activities of these workers, and converting the amount of DU oxides inhaled or ingested into radiation doses. Possible pathways included inhalation of DU oxides from smoke generated by the fire, inhalation of DU oxides resuspended from contamination on surfaces, and ingestion of DU oxides from contaminated surfaces.^[595] Since detailed environmental studies of the situation at Camp Doha were not done during and after the incident, PNNL reviewed the available data and information, interviewed a number of Doha veterans, identified data gaps, and prepared reasonable estimates for many of the parameters required for calculating the dose estimates.

First, PNNL developed estimates of the mass of DU involved in the fire. PNNL found that 660 M829 rounds were involved, and concluded that these rounds formed the only source of DU exposure at Camp Doha. (Although some concerns about the contributions of DU armor to the exposures arose, battle damage assessments reported that the DU armor was undamaged and contributed no DU to the exposures [see Tab I]). There are 3,090 kilograms of DU in 660 rounds.

DU oxides produced by the fire arose from two sources -- rounds loaded in tanks and rounds stored in conex containers in the motor pool. PNNL determined that three M1A1 tanks, fully loaded with 37 rounds each (111 rounds total), burned. The remaining 549 of 660 rounds were stored in conex containers.

Tests of DU's behavior in fires showed that rounds can be ejected by the ignition of their propellant. However, battle damage assessments on the destroyed Abrams tanks revealed that their blast control panels performed very effectively. Based on this and other descriptions of the tanks, PNNL assumed that one round could have been ejected from each tank. Table O-5 (taken directly from the PNNL report) lists the estimated oxide quantities produced by all rounds in the three tanks. Observer reports concluded that much DU oxide was found near the burned tanks.

Table O-5. DU oxides produced from rounds in burned M1A1 tanks^[596]

PNNL estimated the DU oxides from the conex rounds by careful review of numerous reports and by the evaluation of quotes by eyewitnesses. Based on this data, PNNL developed a scenario for the fate of the 549 penetrators in the conex containers (summarized in Table O-6).

Combining the DU oxide produced in the burned M1A1 tanks (50.5 kilograms), the DU oxide from the rounds ejected from the three burned tanks (7.0 kilograms), and the DU oxide from the estimated 249 oxidized rounds in conexes yields a total of 465 kilograms of DU oxide from the fire.

Table O-6. Scenario for the DU rounds in conexes^[597]

PNNL has determined what happened to the estimated 465 kilograms of DU oxides produced. They concluded that significant amounts of DU were found in two areas -- near the conexes of the 2^nd Squadron motor pool and near the three burned M1A1 tanks in the washrack area at the southern end of the North Compound. PNNL assumed that the oxidized penetrators produced 249 randomly distributed oxide deposits totaling about 408 kilograms in the motor pool area (See Table O-7). PNNL also assumed that three penetrators were ejected from the burned tanks in the washrack area. From this assumption, it follows that these tanks contributed a total of about 58 kilograms of DU -- 17 kilograms from inside each of the three tanks and about 7.0 kilograms of DU ejected from the tanks and deposited in three piles of about 2.3 kilograms each.

Other considerations about the fate of the DU oxide deposits over time included wind erosion, human and machine activity, decontamination work, and sweeping. Assumptions about the amount of activity and the time period for each were developed and used in calculating the estimates. The PNNL report, Section 3, (Appendix C of USACHPPM's September 2000 report) contains further details.

Table O-7. Deposits of DU oxides in the North Compound following the July 11-12 fire^[598]

PNNL reviewed the test reports from previous burn tests of similar DU munitions. From those tests, PNNL determined that 0.1 percent of the DU in the penetrators was likely contained in DU released to the air or otherwise unrecovered. PNNL concluded that 0.1 percent represented a conservative (higher) estimate of the fraction of DU released to the air. They calculated that the fire released 0.408 kilograms of DU from the conexes (0.1 percent of 408 kilograms) and 0.058 kilogram of DU from the tanks (0.1 percent of 58 kilograms) into the air. The remainder stayed in the oxide piles.

The DU released during the fire is the primary source of exposure for the personnel assembled in the UN Compound during and immediately following the fire. However, this release also represents a source of exposure for recovery personnel who were present at Camp Doha during the incident and remained there for the recovery. (Section IV.E.3 below discusses the calculation of the dose estimates for Level III personnel.)

Recovery personnel working in the contaminated area of the North Compound could resuspend DU aerosols, leading to their own exposure and to the exposure of those downwind of the contaminated area. PNNL analyzed air concentrations of resuspended DU assuming the following simplified sequence of events:^[599]

• from the fire on July 11^th until the start of cleanup on September 15th, resuspension resulted only from wind and light activity;
• from September 15^th, cleanup and decontamination proceeded for seven days;
• from September 22^nd to the 28^th, contract personnel swept the contaminated area; and
• from September 29^th to October 5^th, contract personnel swept the contaminated area a second time, then hosed it down.

This sequence differs in minor ways from the actual events, but was used to simplify modeling. For example, some DU and residues may have been removed in July by EOD, AMCCOM, and CECOM teams. PNNL, however, assumed all removal occurred in September, thereby erring on the side of a very conservative scenario.^[600]

PNNL estimated air concentrations for each of the periods of the recovery effort, assuming reasonable estimates for wind speed (7 meters/second), resuspension factors -- i.e., the amount of DU surface contamination that resuspends (see Table O-8) -- density of the oxides (4.5 grams/centimeter³), and average surface concentration (0.383 grams/meter²). These parameters were used in a standard air dispersion model to produce estimates of the air concentration at various distances from the North Compound. The results of those estimates are provided in Table O-8. The equivalent emission rates (reflecting the mass of material in grams that gets into the air in one second -- g/s) and the air concentrations formed the basis for evaluating inhalation exposures for recovery workers.

Table O-8. Parameters used for resuspension^[601]

About 600 personnel were possibly exposed to DU during the Doha fire and the four months following. To make its estimates, PNNL considered the workers' locations, the time of day they were exposed, the length of the exposure, and the amount of source material (DU) available in the area. In general, reports revealed that recovery efforts involved long hours and vigorous activity. Workers also spent some time in the contaminated area and some time upwind where inhalation would not occur. PNNL assumed the workers spent 25 percent of the time upwind. PNNL developed eight personnel or job categories to support the description of worker activities. Those are summarized in Table O-9.

Table O-9. Exposed personnel during July 1991 Doha accident^[602]

b. Effects on Health

PNNL used the previous data on air concentrations, surface contamination, periods of recovery activity, and worker activity to calculate the estimated radiation dose and the estimated chemical intake (as DU concentration in the kidney) for representative personnel in the eight job categories. PNNL used input parameters that were chosen based on the characteristics of DU oxides, particle size of the DU oxides, the biokinetic properties of uranium oxides, and personnel characteristics (breathing rate, nose breather or mouth breather, etc.). These were combined with recommended tissue weighting factors, inhalation dose conversion factors, and ingestion dose conversion factors to estimate intakes and doses using accepted mathematical models, namely those described in ICRP-66, ICRP-30, and ICRP-69. The results are provided in Table O-10.

Table O-10. Estimated chemical and internal radiation doses received by personnel during recovery work activities at Camp Doha^[603]

As shown in Table O-10, the estimated kidney concentrations are all well below the 3 �g of uranium per gram of kidney tissue guideline. The calculated radiation doses are also below the annual guideline (0.100 rem) for members of the public, even for the ECC Contractors who had the highest estimated dose. Adverse health effects are not associated with these chemical or radiation exposures.

Level III represents individuals who received relatively fleeting DU exposures from climbing on or entering US or Iraqi combat vehicles to assess damage, to remove equipment, or to look 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 fire and explosion at the Camp Doha, Kuwait motor pool. Beside the personnel involved in cleaning up the North Compound (included in Level II), hundreds of additional personnel may have received short-term exposure to the smoke from burning DU munitions stored in the tanks or conexes. The smoke drifting over the soldiers evacuated to the southern tip of the base probably contained some DU particles. A more complete discussion of Level III activities and practices can be found in Tab G. This section addresses Field Units and Camp Doha personnel in separate sections.

The routes of entry (inhalation, ingestion, and wound contamination) and scenarios for Level III cases are essentially the same as for Level II except that Level III personnel were generally not in vehicles as long as Level II personnel. These scenarios were also characterized by a broad variety of activities, entry times, and other factors. For the most part, these exposures represented one-time, fleeting exposures to smoke from burning, DU-destroyed vehicles, or entry to DU-contaminated vehicles for a variety of purposes.

As with Level II, USACHPPM estimated inhalation and ingestion intakes by first evaluating the amounts of DU contamination and DU air concentrations from resuspended DU residues inside vehicles, and DU air concentrations from burning vehicles loaded with DU munitions using data from relevant test scenarios. It calculated the DU air concentrations, contamination on inside surfaces, and contamination in the outside soil for four Gulf War scenarios:

• exposure to smoke from a burning, fully loaded Abrams tank;
• entry into a fully loaded Abrams tank after a fire;
• entry into contaminated, DU-damaged or -destroyed vehicles; and
• exposure to airborne DU downwind of a vehicle perforated by a DU round.

Air concentrations and surface contamination levels provide the basis for estimating the exposures to personnel in the Level III categories. Table O-11 lists the air concentrations and surface contamination levels derived for the Level III estimates. USACHPPM recognized that Level III personnel experienced a wide range of possible exposure scenarios involving different types of vehicles, extent of vehicle damage, and the amount of time exposed.

Table O-11. Air concentrations and surface contamination for Level III^[604]

As for Level II, USACHPPM developed chemical and radiation dose factors based on one hour of exposure to a vehicle or fire. Table O-12 lists estimates of DU intake, DU kidney amount, DU kidney concentration (total uranium through the kidney divided by the kidney mass), and radiation dose (CEDE) from inhaling the smoke 40 meters downwind from a burning Abrams tank that contains DU munitions. This scenario does not involve ingestion because the soldier does not enter the tank. Therefore the total values equal the inhalation values.

Table O-12. Estimated exposure and dose factors for one hour exposure to smoke 40 meters downwind from a burning tank^[605]

Table O-13 lists the estimated DU intake, the estimated DU kidney amount, the estimated DU kidney concentration, and the estimated radiation dose (CEDE) from inhalation and ingestion from exposure during post-fire entry of a tank containing DU munitions. This scenario involves inhalation from resuspended DU residues and ingestion of residues transferred from the contaminated surface to the hands to the mouth. As for Level II, inhalation estimates assumed material with 7 percent Type M and 93 percent Type S to provide a conservative estimate for radiation dose, and ingestion estimates assumed material with 17 percent Type M and 83 percent Type S to provide a conservative estimate for kidney concentration.

Table O-13. Estimated DU exposure and dose factors for one hour exposure from entering a DU-loaded tank following a fire^[606]

Table O-14 lists estimated DU intake, DU kidney amount, DU kidney concentration, and radiation dose from inhalation and ingestion from exposure during entry of a tank damaged from penetration by a DU munition, such as an Iraqi tank with no other DU munitions involved. This scenario involves inhalation of resuspended DU residues and ingestion of residues transferred from the contaminated surface to the hands and then to the mouth. USACHPPM assumed the DU form contained 17 percent Type M and 83 percent Type S forms of DU to provide a more conservative estimate for kidney concentration.

Table O-14. Estimated DU exposure and dose factors for one hour exposure from entering a DU-damaged tank or combat vehicle^[607]

Table O-15 lists DU intake, DU kidney amount, DU kidney concentration, and radiation dose from inhalation from exposure to the airborne DU puff produced during penetration of a combat vehicle by a DU munition. This scenario does not involve ingestion because the soldier does not enter the tank. Therefore the total values equal the inhalation values.

Table O-15. Estimated DU exposure and dose factors for one hour exposure downwind of a DU-penetrated vehicle^[608]

Assessing the possible health effects from these exposure scenarios for an individual soldier cannot be done without knowing the details of his or her possible exposures. Information on the number of vehicles entered, or the time spent in the vehicles, or the extent of damage to a vehicle cannot be determined easily. Yet, soldiers would like to know something about their possible health effects from DU contacts. We have chosen to provide estimates of intake, kidney concentration and radiation dose from multiple exposures that can be used by soldiers to obtain an estimate of their own situation. Table O-16 lists those values for 10 and 100 exposures. The number of exposures represent a combination of vehicles contacted and the time spent. That is, 10 could be obtained from exposure to 10 vehicles for 1 hour each, 5 vehicles for two hours each, or 20 vehicles for 30 minutes (one-half hour), or any other combination that produces 10.

Table O-16. Estimated Level III DU exposures

As shown in Table O-16, the maximum total intake of 8.2 milligrams due to 100 hours of exposure inside a tank, fully loaded with DU munitions, following a fire, leads to a DU kidney concentration far less (0.16 �g uranium per gram kidney tissue) than the 3 �g/g guideline, and a radiation dose much less (0.04 rem) than the 0.1 rem in a year limit for members of the public.

Recognizing that Level III personnel may have experienced more than one of the four test scenarios, USACHPPM developed a hypothetical, composite scenario that soldiers can use as an example for estimating their own experiences. The scenario involves a cavalry scout who contacted DU in the field:

• taking 20 minutes to pass one burning Abrams Heavy Armor tank;
• entering 7 enemy vehicles hit by DU and spending 7 minutes in each vehicle;
• entering one enemy vehicle for one hour, contaminating his uncovered hands, which he then did not wash for two days; and
• taking 10 minutes to pass at a distance of 80 meters through the smoke plumes of 3 enemy tanks struck by DU.

As shown in Table O-17, four scenarios produce a total DU intake of 0.065 mg that leads to a kidney concentration far less (0.0012 �g DU/g tissue) than 3 �g uranium/g tissue guideline, and a radiation dose far less (0.00016 rem) than the 0.1 rem in a year limit for members of the public. The intakes do not represent amounts that would produce chemical or radiation effects.

Table O-17. DU intakes for a Level III scenario -- a soldier's combined exposure to several events^[609]

DU munitions in the burning tanks and conexes located in the North Compound produced airborne concentrations of DU in the smoke and fumes that passed to the Southeast over the United Nations compound. The several hundred personnel who assembled there could have inhaled DU from the smoke. PNNL estimated the possible air concentrations and doses from two sources -- the area around the burning conexes, and the area near the washrack with the three burning tanks.^[610] Section D.3.c above discussed the details of airborne DU during the fire. PNNL calculated values for both an elevated release,^[611] and a ground-level release^[612] (see Table O-18). PNNL estimated that the highest exposure any person could experience occurred one kilometer downwind of an elevated release.

To calculate its estimates, PNNL assumed:^[613]

• the fire started at 10:20 AM, but no oxides formed for several hours (not until about 1:00 PM).
• most of the oxide formed during the first 12 hours at a uniform rate of 8 percent per hour for a total of 96 percent.
• the remaining 4 percent formed during the remainder of the scenario.

Table O-18. Time-integrated air concentrations from fire^[614]

Using these integrated air concentrations and appropriate solubility values for DU oxides [PNNL assumed 7 percent were soluble Class W oxides and 93 percent were insoluble Class Y oxides, a breathing rate of 1.688 meters³/hour, simulating "manual labor," appropriate aerosol characteristics (5 �m AMAD)]^[615] , and appropriate factors for conversion of mass of DU in body organs to radiation dose (1.74 x 10^-2 rem per milligram of DU metal in the oxides),^[616] PNNL estimated the chemical and radiation doses shown in Table O-19. These results are far less than the kidney concentrations and radiation doses associated with adverse health effects.

Table O-19. Inhalation doses received by people downwind of the Doha fire^[617]

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