PUBLIC HEALTH ASSESSMENT
U.S. ARMY MATERIALS TECHNOLOGY LABORATORY
WATERTOWN, MIDDLESEX COUNTY, MASSACHUSETTS
This section presents the three exposure situations we have determined pose no apparent publichealth hazards and lists the information we used to make definite conclusions about them. Wealso describe one situation we have determined does not pose a public health hazard.
ATSDR's public health assessments are exposure, or contact, driven. Chemical contaminantsdisposed or released into the environment at MTL, and other former Watertown Arsenalproperties, have the potential to cause adverse health effects. However, a release does not alwaysresult in exposure. People can only be exposed to a chemical if they come in contact with it. Exposure may occur by breathing, eating, or drinking a substance containing the contaminant orby skin (dermal) contact with a substance containing the contaminant.
The type and severity of health effects that occur in an individual from contact with acontaminant depend on the exposure concentration (how much), the frequency and/or duration ofexposure (how long), the route or pathway of exposure (breathing, eating, drinking, or skincontact), and the multiplicity of exposure (combination of contaminants). Once exposure occurs,characteristics such as age, sex, nutritional status, genetics, life style, and health status of theexposed individual influence how the individual absorbs, distributes, metabolizes, and excretesthe contaminant. Together these factors and characteristics determine the health effects that mayoccur as a result of exposure to a contaminant.
ATSDR concluded that three exposure situations present no apparent public health hazard (Table 1).
Subsurface Contamination - The general public is not likely to be exposed to residualcontamination at the FUDS parcel. The Army has completed their contaminant characterizationof soils on the FUDS property and will be remediating small areas of soil. Until remediation iscomplete, areas with surface soil contamination are temporarily fenced. (9) In unremediatedareas where soil contamination poses no current threat, we recommend that procedures be implemented to ensure that future property owners know of potential hazards and avoidinadvertent exposure to residual contamination. We requested and the Army collected additionalradiological sampling in sanitary sewers on the FUDS parcel. (10) After review of the recentsanitary sewer sampling (Summer 1996), ATSDR ruled out utility worker exposure toradiological contamination as a potential health hazard.
Fish in the Charles River - In response to ATSDR's request (11,12,13,14), the MassachusettsDepartment of Environmental Protection (MDEP) sampled fish from the Lower Charles Riverincluding the area near the Arsenal and detected high enough levels of polychlorinated biphenyls(PCBs) in carp for the Massachusetts Department of Public Health (MDPH) to issue a fishconsumption advisory for the Lower Charles River between Hemlock Gorge Dam and theMuseum of Science. (15) If the advisory is followed, this exposure situation poses no apparentpublic health hazard.
Past Air Releases of Depleted Uranium -Although depleted Uranium (DU) was periodicallyburned at the Arsenal in the past, the amount of DU released to air was unlikely to be at levelsconsidered harmful to residents of the surrounding community. There were few, if any,community members living close enough to the Arsenal to have been exposed to airborne DU inthe past. Very conservative assumptions were used in the radiation dose estimates. We assumedburning occurred 8 hours a day, 365 days per year, for a maximum of 20 years. Based on theseassumptions, the lifetime cancer risk was less than the risk of cancer expected from backgroundlevels of radiation. The MDPH review of cancer incidence for Watertown (16) showed noobserved increase in cancer rates plausibly associated with depleted uranium radiationexposure.
|PATHWAY NAME||CONTAMINANT||EXPOSURE PATHWAY ELEMENTS||TIME||COMMENTS|
|SOURCE||ENVIRONMENTAL MEDIA||POINT OF EXPOSURE||ROUTE OF EXPOSURE||POTENTIALLY EXPOSED POPULATION|
|Subsurface Contamination||Metals, PCBsa PAHsb and TPHc in subsurface soils||FUDS property now the site of the Arsenal Mall||Soil, groundwater, building rubble and associated sanitary and storm sewers||Soil and debris||Contact with contaminated soil and debris||Construction or Utility Workers||Future||No one is currently beingexposed to residualcontamination, which is buriedand, in some areas, paved overon the FUDS parcel. (5,7) However, because the Army nolonger controls the property,current or future landownerscould further develop the land,possibly leading to exposure ofutility or construction workerswho might unearth contaminatedmaterials.|
|Subsurface Contamination||Radiologic (U,Th,Ra)d contamination associated with buried remnants and sewer systems of formerArsenal buildings||FUDS property now the site of the Arsenal Mall||Sanitary and storm sewers||Sewer pipes||Inhalation, ingestion and photon radiation||Public Works Employees||Present|
|Surveys determined radiationhazards to public worksemployees did not exist in thesewer systems associated withthe FUDS parcel.|
|Fish in Charles River||PCBs||MTL, FUDS, and many other sources of industrial and urban discharge||Carp from the Charles River between Hemlock Gorge Dam and the Museum of Science||Eating possibly contaminated fish||Ingestion||People who eat contaminated fish||Past|
|The Charles River iscontaminated with metals,pesticides and PAHs, bothupstream and downstream ofMTL. (17,18) People reportedlyfish in this urban stretch of theriver. Recent sampling done bythe MDEP (15) showed that carphad high enough levels of PCBsfor MDOH to issue a fishconsumption advisory.|
|Past Air Releases of Deplete Uranium||Radiologic (U,Th,Ra)d contamination associated with burning DU at GSA property and in Building 43||Past burning in Building 43 incinerator and on GSA property||Air||Air||Inhalation, and ingestion||Residents||Past||There were few, if any,community members livingclose enough to the Arsenal tohave been exposed to airborneDU in the past. Veryconservative assumptions wereused in the radiation doseestimates. The lifetime cancerrisk was less than the risk ofcancer expected frombackground levels of radiation.|
The general public is not likely to be exposed to residual contamination at the FUDS parcel. The Army has completed their contaminant characterization of soils on the FUDS property andwill be remediating areas where soil levels exceed MDEP standards. Until remediation iscomplete, areas with surface soil contamination are temporarily fenced. (9) In unremediatedareas where soil or debris (e.g., building rubble, unconnected piping) contamination poses nocurrent threat, we recommend that procedures be implemented to ensure that future propertyowners know of potential hazards and avoid inadvertent exposure to residual contamination. Recent additional radiation surveys (Summer 1996) in the sanitary sewer system along ArsenalStreet and Greenough Boulevard in areas where there were connections with former Arsenalbuildings 34, 41 and 421 showed that utility workers who enter these confined spaces would notbe exposed to radiation at hazardous levels. (19)
Figure 3 depicts the portion of the former Watertown Arsenal (FUDS parcel) which is now theArsenal Marketplace. Subsurface soil, debris, and groundwater beneath the property arecontaminated. We are concerned that future development of the FUDS parcel could unearthresidual contamination, possibly leading to worker exposure, particularly radiologicalcontamination associated with remnants of former Arsenal buildings 34, 41 and 421.
Subsurface Contamination: The Army has conducted a preliminary assessment (7), an initial siteinvestigation (5) and a phase II site investigation at the property (12) which provides informationabout the extent of contamination there. Although groundwater at the site is contaminated withvolatile organic compounds and metals, no one is using the water for domestic purposes soexposure is not a concern. Subsurface soils are contaminated with polyaromatic hydrocarbons(PAHs), polychlorinated biphenyls (PCBs), metals and total petroleum hydrocarbons at levels ofpossible health concern. However, this contamination is well below ground surface, where itdoes not pose a health threat at this time. Extensive landfilling and regrading activity was doneduring redevelopment; consequently, little surface soil contamination has been detected. A fencesurrounds an area where arsenic levels in surface soil exceed the Massachusetts Department ofEnvironmental Protection (MDEP) guideline of 40 ppm. The Army conducted followupsampling and performed an Imminent Hazard Evaluation for the site. Although the arseniccontamination in the park is not an imminent hazard, the Army, working with MDEP, EPA andlocal officials, is implementing measures to prevent exposures to the limited area where arseniclevels are elevated. (20,21,22,23) PCBs exceeded MDEP standards in subsurface soils south ofthe mall area. The area is approximately 50'x50'. The Army is working to better define the areaof contamination, but hopes to complete characterization and remediation by the Spring of 1997.(9) No one is currently being exposed.
Radiation: Other investigations included several surface radiation surveys which were conductedafter the parcel was redeveloped. The surveys were done to address concerns about residualcontamination from past work with thorium and uranium/radium ores in some former Arsenalbuildings. The surveys measured radiation levels within background values (7) which confirmthat no surface radiation hazards exist. ATSDR was concerned that, although Buildings 34, 41and 421 were torn down during the redevelopment, foundations and subsurface structures(sewers and storm drains) remained buried on the property. Prior to demolition, radiologicalsurveys confirmed contamination of some of the piping associated with buildings 34 (machineshop) and 41 (foundry). In building 34, radiation levels as high as 40 milliroentgen per hour(mR/hr) in a pipe trench, and 20 mR/hr in a drain were detected. (7) A water and sludge samplefrom sewer connections in building 41 indicated Uranium and Radium-226 anomalies, whichwere not described in detail. (7) It is unclear if these contaminated drain lines, and perhapsothers, were removed. It is likely they are still contaminated because radiologically-contaminated sanitary sewers and storm drains connected to the foundry and machine shop on theadjacent MTL property required extensive remediation. Further, dye trace studies and sedimentsampling done in sewer lines along North Beacon Street and Arsenal Street confirmed thatradiologic contamination from the MTL facility had migrated off-post. (4) Therefore, sincesimilar industrial activities were also carried out in former Arsenal buildings 34 and 41, and, tosome degree, building 421 on the FUDS parcel, it was likely that discharge points associatedwith those razed buildings are also contaminated and we requested further sampling in existingsewers. (5,7,24,25) That sampling was conducted in July 1996 and showed that although therewas some radiologic activity, it was not at levels that would pose a health hazard for utilityworkers (19). Figures 4 and 5 show the locations of the additional sampling in the sanitary sewer connections and storm drains on the FUDS parcel.
The supplemental sanitary sewer sampling evaluation included analyses for uranium species,thorium species, and their respective decay products including radium and radon. Access pointsto the sewer system in areas once connected to these buildings were surveyed on the FUDSparcel, along Arsenal Street and Greenough Boulevard (Figure 4) as well as storm waterdischarge points along the Charles River (Figure 5).
Figure 4. Sanitary Sewer Sampling Locations - FUDS Parcel
Reference: ABB Environmental Services, Inc. Draft Sampling and Analysis Plan, Former Watertown Arsenal - FUDS Parcel, Watertown, Massachusetts. Phase II Comprehensive SiteAssessment. May 1996.
ATSDR recommended that edible fish species, representing the types that recreational fishermencatch from areas of the Lower Charles River including the area near the Arsenal, be sampled forchemical contamination. (11,12,13,14) The former Arsenal is one of a number of industrial andurban sources that have contributed pollutants to the river. (17,31) Limited surface water andsediment sampling in the section of the river bordering MTL show pesticide, metal andpolyaromatic hydrocarbon contamination. We were concerned that some of these chemicals,which are known to biomagnify in the foodchain, could concentrate to levels of health concern inedible fish tissue. (17,32) The Massachusetts Department of Environmental Protectionaddressed this public health issue by conducting fish sampling in the Lower Charles Riverincluding areas near the Arsenal. High enough levels of PCBs were detected in carp for theMassachusetts Department of Public Health (MDPH) to issue a fish consumption advisory forthe Lower Charles River between Hemlock Gorge Dam and the Museum of Science. (15)
MTL: Several studies were done to evaluate chemical contamination in sediment and surfacewater from the Charles River near MTL. Remedial investigation sampling results from 1990through 1993 show that the river is contaminated with metals, pesticides and PAHs bothupstream and downstream of MTL. (17) At EPA's request, the Army is conducting furthersediment sampling to aid in determining the need for further study, such as sampling of aquaticbiota in the river. (31)
FUDS: The FUDS parcel, which was part of the original Watertown Arsenal, also borders theriver. Thus far, none of the environmental investigations there have focused on the river. (33)The current public information program for the FUDS parcel includes providing reports andnews releases to the current owners of the property.
Other Pollution Sources: Considering the historic uses of the Charles River, there are clearlyother sources polluting the river besides the former Arsenal properties. Because urban andindustrial activities within the Charles River watershed have generated both non-point and pointsources of pollution (17), ATSDR also brought the issue of suspected fish contamination to theattention of both the Massachusetts Departments of Public Health (MDPH) and EnvironmentalProtection (MDEP). (11,12,14) The state had sampled fish in sections of the Charles River 10-30 river miles either upstream or downstream of the Arsenal site (16). However, no fishsampling had been done to determine if contaminants in surface water and sediment in theWatertown area had entered the food chain. ATSDR was concerned that people were fishing inthis section of the river and anglers and their families may have been eating the fish they caught.(34)
State Actions: In November 1995, the MDEP completed fish sampling in the Lower CharlesRiver which included the Arsenal area. As a result of that sampling, in May, 1996, MDPHissued a carp fish consumption advisory for the Lower Charles River between Hemlock GorgeDam and the Museum of Science. (15) The advisory states that children under 12, pregnantwomen and nursing mothers should not eat carp. All other people are advised to limit theirconsumption of carp to two meals per month. The MDPH fish consumption advisory for theLower Charles River was communicated to the Watertown Board of Health (BOH) as well as theNewton Board of Health for the southerly side of the river. (15)
MDPH already issued a statewide fish consumption advisory for pregnant women becausemercury levels detected in fish collected from diverse Massachusetts water bodies provide aninadequate margin of safety for a developing child. (35) The MDPH has also reviewed fish datafor other portions of the Charles River and, in August 1995, issued a fish consumption advisoryfor the section of the Charles River between the Cochran Dam in South Natick and the HemlockGorge Dam in Needham / Newton.
Although depleted Uranium (DU) was burned at the Arsenal in the past, the amount of DUreleased to air was unlikely to be at levels considered harmful to residents of the surroundingcommunity. There were few, if any, community members living close enough to the Arsenal tohave been exposed to airborne DU in the past. Very conservative assumptions were used in theradiation dose estimates. We assumed burning occurred 8 hours a day, 365 days per year, for amaximum of 20 years. Based on these assumptions, the lifetime cancer risk was less than the riskof cancer expected from background levels of radiation. The MDPH review of cancer incidencefor Watertown (16) showed no observed increase in cancer rates plausibly associated withdepleted uranium radiation exposure.
Controlled incineration of depleted Uranium chips was done because of the pyrophoric propertiesof the metal. The incineration not only prevented the chips from spontaneously igniting but alsoreduced the volume of DU waste requiring disposal at Atomic Energy Commission (AEC)licensed facilities and, after 1974-1975, Nuclear Regulatory Commission licensed facilities. (37) The DU was initially burned in a remote part of Watertown (GSA site), away from residentialareas. Later, DU was incinerated in building 43 (MTL) where air releases occurred from a stacknear the east end of the building. Detailed information about DU burn activities at both the GSAsite and building 43 are provided below.
GSA site - Northeast Area
Incineration Practices: Depleted Uranium was incinerated in a fenced area at the Northeast Area,which is now the GSA site, from 1955 to 1967 (Figure 6). (7) During the time period when theburn pit was used it was in a remote area, away from residences. Procedures were implementedto prevent exposure of personnel to airborne radioactivity. These procedures are described inAppendix D-1. (37) A December 23, 1966 letter from the Arsenal (AMRA) to the AtomicEnergy Commission (AEC) reported air sampling results for Uranium oxidation procedures. Although numerical data were not provided, the letter indicates that average Uraniumconcentrations in smoke generated by oxidation were below limits set in the federal regulationsin place at that time. (7) The 1966 AEC limit for air releases in unrestricted areas was 5 x 10-12Ci/ml for Uranium-238, which is the predominant isotope in DU. This level is applicable forboth soluble and insoluble Uranium compounds and assumes constant exposure. The limit inplace at that time would result in a whole-body dose of 0.5 rem/year (500 mrem/y) to the generalpopulace and considers the potential presence of children in the group. Based on these data, airreleases of DU from the GSA site were not at levels of health concern.
Human Exposure: We do not expect that people off site were exposed to significantconcentrations of airborne Uranium oxides. The residential areas that now border the westernedge of the GSA property, were built after burning ceased. Aerial photographs from 1968 showno housing in the site vicinity. (7) Because DU is extremely dense, particles carried in smokewould quickly settle to the ground in the general proximity of the burn pit. Conceivably, verysmall particulates could disperse at greater distances from the source. However, deposition ofthese fine particles would be widely scattered, and consequently, measurable amounts of DUwould not occur in localized areas distant from the source. Therefore, significant amounts offugitive DU particulates in smoke would not be expected to have drifted far off site. Even in theunlikely event that people off site did inhale DU particulates, exposures would have been rareand, based on available air dispersion data, the resulting dose to the lung would have beenbelow health concern.
Radiological surveys to determine the extent of contamination at the GSA property confirm thatradiologic contamination is primarily confined to surface soil in discrete, on-site areas. Nocontamination was found at the boundary of the site outside the new fence or on the southwestside of Greenough Blvd. (38) Residual soil contamination on both the GSA property andadjoining Property 20 does not pose a health threat to people who live in areas adjacent to thesite. Access to potentially contaminated areas is restricted by fences surrounding the burn pit, theGSA property boundary and the portion of Property 20 where fill was placed. (38, 39)Additionally, the fence is marked with radiation hazard signs. (38)
Contamination is not widespread. (40) Additional survey work showed that the current DU andRa-226 levels prohibit releasing the property for unrestricted use under NRC regulations andguidelines (38) as some areas exceeded the NRC standard of 35 pCi/gram. However, the MDEPmay have stricter cleanup standards so remediation plans are on hold pending completion of arisk assessment (9). Additionally, some chemical contamination was found (primarilypetroleum) and those chemicals will also be included in the risk assessment. No one is currentlyexposed to soils as the entire area is fenced. Cleanup of this area is expected in 1998. (9)
Building 43 - Foundry on MTL
Incineration Practices: The Arsenal began burning depleted Uranium in building 43, the MTLFoundry, (see Figure 7) as an additional method of incineration after the GSA property was nolonger used for that purpose. Although records could not be located that indicate when theincinerator was first used, most DU burns occurred in the 1970s and early 1980s. The NuclearRegulatory Commission approved the activity on March 28, 1980. In 1981, high efficiencyparticulate air (HEPA) filters and a scrubber were installed on the incinerator. These engineeringcontrols reduced the amount of DU released to the outside air. By the mid to late 1980s, DU wasburned infrequently, and by July 1992, DU was no longer burned at the Arsenal. (41,42)
In the past, a few uncontrolled DU fires also occurred inside the Foundry building. DU chips,that were temporarily stored in barrels, occasionally spontaneously ignited in the presence of air.The fires were contained within the barrel, inside the foundry. To prevent these types of firesfrom occurring, the DU chips were stored in oil or water. (41, 42, 43)
Human Exposure: To estimate the potential radiation dose resulting from DU released frombuilding 43, we reviewed available air sampling data. The Arsenal had limited stack monitoringdata, spanning from 1981 to 1991 (Appendix D-2). After 1980, the amounts of DU releasedfrom the stack dropped dramatically. Because the data were not complete, we made severalassumptions prior to calculating dose estimates. ATSDR estimated the maximum and minimumamounts of air flow in the crude incinerator, the maximum and minimum amounts of DU in aburn. The 1981 air data were used in the dose estimates because no earlier data could be found.(43). These data represent the greatest documented amounts of material released from the stack.(43)
We also assumed that DU burns occurred 8 hours per day, every day of the year. However, thesevalues likely overestimate the actual duration and rate of burning. Arsenal records from 1972 to1977 indicate that DU burns usually lasted about 2 hours and occurred 5 times or less a month.(44) Additional data indicated 8 burns in 1980*, 9 burns in 1981 (3.8 hour average burn time), 6burns in 1982 (4 hour average burn time), 3 burns in 1983 (5.5 hour average burn time), 3 burnsin 1984*, 1 burn in 1987*, 1 burn in 1990 (4 hour duration) and 2 burns in 1991 (1 and 4 hourduration). (45(1)) The reported volume of air handled by the system ranged from about 400 to1265 ft3 per minute. (46) From these very conservative assumptions, the total amount of DU andproducts released from the stack was estimated. The estimated totals for 1981 were between 84and 267 millicuries (mCi) of Uranium-238 and 217 to 685 mCi of Thorium-234 (a decay productof U-238).
Once the total amounts of radioactive materials released were estimated, ATSDR performed aprobability analysis, based on 10,000 trials, to estimate the most probable amount of materialreleased from the stack. These values were then entered into the CAP88-PC radiologicalassessment software package. (47)
CAP88-PC estimates the risk and dose from radionuclides released through the air. Its use isrequired in 40 CFR 61.93(a) [Code of Federal Regulations], in compliance with the Clean AirAct, when calculating radiation doses to the public.
The results indicate that the maximum effective dose equivalent (EDE) resulting from DUincineration was less than 200 mrem per year (mrem/y), whole body, to an individual livingwithin 200 meters of building 43 in 1981. As the distance one lived from the Arsenal increased,the effective dose decreased. The maximum calculated whole body dose was within the 500mrem/y federal limit in place in 1981. (48) Even though the current federal limit is 100 mrem/y,(49,50) we do not consider the estimated doses to be a health hazard since very protectivemargins of safety were used in setting these limits and in the dose calculations. The 100 mrem/ylimit assumes a member of the general public is exposed to these levels every day for 70 years;however, 500 mrem/y is still permitted for infrequent exposures. Moreover, the occupationalannual limit is 5000 mrem/y and no known adverse health effects have been reported at thatlevel. (49)
Cancer Risk: The CAP88-PC model also develops cancer risk estimates related to the estimatedradiological dose summed for all radionuclides entered into the model, in this case, U-238 andTh-234, the major radionuclides present in DU. The estimates are given for several organsystems and the whole body. Uranium-238, for the purposes of radiation dosimetry, isconsidered to be uniformly distributed throughout the bone. Thorium-234 is considered to beuniformly distributed over the bone surface (51). Therefore, the critical organs affected would beboth the bone surface and the red marrow within the bone interior, and the lungs which are thepoint of entry. However, lung cancer would comprise virtually all the risk from this form ofexposure. The data from our CAP88-PC calculations indicates that the exposure to the entirebody was less than 200 mrem per year. This equates to a lifetime cancer mortality risk that is 10 times less than the risk expected from 70 years of exposure to natural radiation in theenvironment. (52)
Population Exposed: Based on the modeling, maximum exposure would have been to peopleliving within 200 meters of building 43. The nearest residential areas, which are about 200meters from building 43, are on MTL and on the FUDS parcel to the east.
Figure 8 (1980) and Figure 9 (1990) show population estimates within 100, 250 and 500 metersof building 43. These estimates are based on census data, assume even distribution of thepopulation within each census subgroup, and extrapolate the percentage of the census subgroupwithin each concentric circle. These figures probably underestimate the actual number of peoplewho live closest to building 43. Condominiums and apartments, built on redeveloped former
Arsenal property, are within 200 meters east of building 43. However, these residential areaswere not built until the early 1980s, by which time air releases of depleted uranium from building43 were significantly reduced. The condominium complex is comprised of an original Arsenalbuilding (building 212) that was renovated and two newer buildings. The Arsenal Apartments,housing for the elderly, includes a five-story apartment building and several renovated formerArsenal buildings (buildings 71, 72 and 73). (7)
The three buildings on the MTL facility that were used for housing are roughly 250 meters ormore from building 43. (Figure 7) Building 111 was the Installation Commander's residence,building 117 was a four-bedroom senior officer's quarters, and building 118 comprised five two-bedroom family units. The average length of residence in any of these military housing units was2 to 3 years. (53)
Health Effects of Particulates: Inhaled particulates penetrate different regions of the respiratorytract based mainly on their size (also referred to as activity mean aerosol diameters [AMAD]). Itis the very small DU particulates released to air that are of greatest concern from an exposurestandpoint, because they can be inhaled deep into the lung (Table 2).
|Respiratory Deposition||Percent Deposition by Particle Size (µ)|
|Tracheal Bronchial Tree (Throat)||8||8||8|
|Pulmonary Parenchyma (Lung)||9||25||43|
*Note: The deposition does not add up to 100% because particles larger than 5 are usuallyexpelled before they enter the body and some particles never enter.
The airborne material produced from burning DU is UO2 and U3O8 which are relatively insolubleuranium oxides. These uranium oxides are class Y compounds, which have an estimated lungretention time of greater than 100 days because they are not very soluble in lung fluids. (51) Thismeans that they stay in the lungs for an extended period of time before being distributedthroughout the body. The majority of uranium oxide particulates deposited deep in the lung aresmaller than 0.3µ. Particles ranging in size from 0.3µ to 5µ also add to the lung burden, but to alesser extent. And finally, less than 10% of particles with AMAD greater than 5µ penetrate intothe deep lung region. (51) Particles deposited in the nose and throat are usually expelled fromthe upper air ways and ingested. Because these ingested particulates are uranium oxides, whichare relatively insoluble, they pass through the digestive system and are excreted fairly rapidly.
The 1981 air data used in the radiation dose estimation model is from the time period afterengineering controls reduced the amount of DU released to outside air. However, releases of fineDU particulates (less than 0.3 microns [µ]) to air during burning in 1981 and after, were mostlikely comparable to earlier years. Although the use of high efficiency particulate air (HEPA)filters on the incinerator decreased air releases of particulates greater than 0.3µ in size, fineparticulates continued to be emitted. As discussed earlier, using data representing the greatestamounts of material released from the stack and incorporating assumptions that are veryprotective of public health, the maximum estimated radiation dose was not at levels which pose apublic health hazard.
Public health issues concerning future land use of MTL and the GSA site (see Figure 1) are ofutmost importance and are being actively addressed. Procedures are implemented duringsampling and cleanup activities to protect both the general public and remediation workers frompossible hazards. Further, before the land can be transferred for reuse, all necessary cleanupactions must be completed.
The Army is conducting site investigations and cleanup at MTL and the GSA site under theguidance of the Commonwealth of Massachusetts Departments of Environmental Protection(MDEP) and Public Health (MDPH), the U.S. Environmental Protection Agency (EPA) and theNuclear Regulatory Commission (NRC). These regulatory agencies set cleanup levels that areprotective of public health considering the land reuse options that are planned. ATSDR supportsthese activities by providing technical assistance concerning public health issues as requested. We reviewed the "Human Health Radiological Risk Assessment for Massachusetts 21E Sites" forMDEP and concur that the 10 mrem dose limit proposed for cleanup at MTL is protective ofpublic health. (55) We have also reviewed documentation regarding environmental activities atthe former Arsenal properties (GSA site and FUDS parcel) and provided comments to the Armyand regulatory agencies concerning issues of public health importance. (13,10,39,56)
Residents who live next to MTL and the GSA site expressed concern about possibly beingexposed to contaminants because they see on-site workers wearing personal protective equipment(PPE) during sampling and cleanup activities. However, the use of PPE by remediation workersdoes not necessarily mean that a site is extremely hazardous; rather, PPE is a requiredprecautionary measure to protect workers from possible hazards encountered during fieldinvestigations. Other actions are taken during the course of site cleanup that prevent exposuresfrom occurring. These include restricting access in areas where residual contamination is atlevels of public health concern. Fencing and/or security measures, which effectively limit siteaccess, are in place at MTL and the GSA site. Finally, Site Health and Safety Plans, which detailproper safety measures to be followed during all site work, are developed. These plans includecontainment methods to prevent contaminated dusts, vapors, etc from moving away from the siteduring sampling and cleanup activities.