PUBLIC HEALTH ASSESSMENT
ARNOLD ENGINEERING DEVELOPMENT CENTER
(a/k/a ARNOLD AIR FORCE BASE)
ARNOLD AIR FORCE BASE STATION, COFFEE COUNTY, TENNESSEE
In this section, ATSDR evaluated environmental information to determine whether contamination poses hazards to people having access to or living near AAFB. ATSDR's public health assessments are driven by exposure to (contact with) contaminated media. In evaluating exposure pathways, ATSDR determines whether exposure to contaminated media has occurred, is occurring, or will occur through ingestion, dermal (skin) contact, or inhalation of contaminants. When exposure to contaminated media occurs, the exposure pathway is regarded as "complete." To determine whether completed pathways pose a potential health hazard, ATSDR compares contaminant concentrations to health-based comparison values (CVs). Comparison values are calculated by ATSDR toxicologists, using available scientific literature on exposure and health effects. These values, which are derived for each of the different media, reflect the estimated contaminant concentration for a given chemical that is not likely to cause health effects, given a standard daily ingestion rate and standard body weight for specified periods of time. Contaminants detected above the CVs do not automatically present a public health hazard. If contaminant concentrations are above CVs, ATSDR further analyzes exposure and the toxicology of the contaminant to determine whether a public health hazard could occur.
ATSDR reviewed available data from environmental monitoring at AAFB. Table 1 presents ATSDR's site-by-site evaluation of IRP sites. ATSDR identified and evaluated the following possible exposure pathways at AAFB: methane migration into water wells or homes; consumption of catfish and turtles; UXO and other physical hazards; consumption of contaminated groundwater; contact with soil, surface water, and sediment. The following sections present an evaluation of potential exposure pathways, which are also summarized in Table 2. To acquaint readers with terminology and methods used in this report, Appendix A provides a list of comparison values (CVs), Appendix B summarizes the methods and assumptions used to estimate exposure doses and support some of the report's conclusions, and Appendix C provides a glossary of terms.
Nature and Extent of Contamination
Coffee County Landfill is a 97-acre inactive landfill located in the northwest corner of the base on State Route 55, adjacent to Central High School. The landfill property was leased from the Air Force by the County during the period of landfill operation (January 1972 to February 1989). The following types of waste were disposed of in the landfill: household refuse, construction debris, metal salts, acids, solvents, resins, paint sludge, hospital waste, and animal carcasses. After the landfill was closed, it was covered with a layer of soil and was eventually overgrown with vegetation (CH2MHill, 1995). AAFB constructed a security fence around the site in 1993. AAFB completed a design for a clay layer cover, or "cap", for the landfill in 1996 and construction of the cap was completed in August 1998 (AAFB, 1998; Brandon, 1999). The location of this landfill is depicted in Figure 2.
In late December 1998, the area around AAFB experienced a severe ice storm. On January 7, 1999, AAFB was informed that a resident living west of the Coffee County Landfill had received severe burns during a flash fire that occurred on December 28 as he was making adjustments to the pump in his well. AAFB personnel investigated and found methane accumulation in the well house. (Methane, a colorless, odorless, flammable gas, is commonly generated as a product of decomposing organic materials in landfills.) Further methane monitoring around the landfill confirmed that landfill-generated methane was migrating; AAFB personnel believe that the ice that accumulated on top of the landfill during the ice storm impeded normal venting of methane from the landfill cap. The methane migrated horizontally from the landfill through permeable soils, confined by a clay layer in the uppermost soils. In places where penetrations through this clay layer (such as wells) occurred, methane could migrate upwards. If it then reached a confined area such as a well house, it could accumulate to potentially explosive levels.
In response, the AAFB immediately began construction of a methane venting system along the north and west sides of the landfill. The system pipes methane to a central location where it is destroyed by flaring. AAFB also initiated daily methane monitoring at residences west of the landfill and at the high school to the north of the landfill (Brandon, 1999).
As an added measure of protection, Coffee County extended the public water supply line to residences west of the landfill along the Old Tullahoma Highway (which parallels State Route 55 to the west), and AAFB and the county plugged all wells (except one where the owner did not want it done) to eliminate penetrations into the zone of methane migration. Following the completion of the landfill gas collection system (April 1999) and subsequent plugging of the private wells, AAFB discontinued methane monitoring at private residences. AAFB, however, continues routine monitoring of methane at the high school. To date, the daily sampling of the school building has not detected the presence of methane (Munda, 2000).
AAFB worked with TDEC and EPA officials in addressing the issue of methane migration. ATSDR agreed with EPA's assessment that AAFB is taking all necessary measures to address the problem and protect public safety (Britain, 1999).
Evaluation of Potential Public Health Hazards
Methane migration from Coffee County Landfill currently poses no apparent public health hazard. The methane extraction and monitoring and the plugging of nearby private wells that the AAFB has undertaken should ensure that methane does not pose a health threat to nearby residents or to high school students and staff. ATSDR agrees with the decision by AAFB to continue daily monitoring of the high school for the possible migration of methane, until perimeter monitoring of the landfill confirms that methane is no longer present.
Nature and Extent of Contamination
Polychlorinated biphenyls (PCBs) have been detected in fish taken from Woods Reservoir. In 1985, the state of Tennessee issued a fish advisory for Woods Reservoir because levels of PCBs in catfish were above the Food and Drug Administration's guideline of 2 parts per million (ppm). The advisory instructed people not to eat catfish caught at Woods Reservoir because of PCB contamination. The advisory remains in effect; the public is notified of the advisory by signs at the lake and also in the Tennessee Fishing Regulations pamphlet (ATSDR, 1996). In addition, ATSDR conducted public outreach and training of health professionals about the advisory in 1996 (ATSDR, 1996).
Sampling data for catfish, carp, and bass are available for approximately every other year between 1981 and 1998; other species such as crappie and sucker were sampled from time to time (ATSDR, 1996; AAFB, 1997, 1999e). In addition, AAFB sampled turtles in 1997 to determine whether there was sufficient PCB in their tissue to initiate a regular sampling program (SAIC, 1997).
PCB levels found in recent sample analyses have decreased from the levels originally found. In order to assure that the results of the sampling were scientifically consistent and to provide assurance that the decrease in PCBs detected is not an artifact of the sampling and analysis procedures, AAFB conducted a statistical study of the 1987 - 1996 data (AAFB, 1997). The conclusions of the 1997 report support the contention that decline in PCBs is an actual decrease, and not an artifact of sampling procedure. The analyses for 1998 also support a continuation of the decreasing levels of PCBs in catfish. See Table 3 for a summary of PCB levels in catfish. Levels in other species have been lower than in catfish. PCBs were only detected in two of eight snapping turtle samples, at a maximum of 0.12 ppm (SAIC, 1997).
Evaluation of Potential Public Health Hazards
Levels of PCBs in fish taken from Woods Reservoir before 1987 are unknown. However, some of the fish collected in the past have contained levels above what is considered safe for regular and frequent consumption. Because the actual levels are unknown and because it is not possible to determine actual levels of consumption prior to the first sampling analyses, past consumption of fish in Woods Reservoir is considered an indeterminate public health hazard.
In the NPDES permit issued in 1992, the Tennessee Division of Water Pollution Control certified that AAFB was in compliance with the requirement to retrofit all former sources of PCBs throughout the base (TDWPC, 1992). Elimination of sources for PCBs within AAFB have likely reduced or eliminated the introduction of additional PCBs into Woods Reservoir (AAFB, 1997). Although PCBs are relatively persistent in the environment, naturally-occurring sedimentation in the reservoir is likely covering existing PCB in bottom sediment, rendering it less accessible to bottom-feeding species of fish. Although levels of PCBs found in fish have declined in recent years, because it is thought that not all anglers follow the advisory, ATSDR evaluated whether consumption of fish from Woods Reservoir would currently pose a public health hazard. Using the 1998 sampling data, ATSDR estimated exposure dose using levels of PCBs detected in fish from the reservoir. Appendix B provides a detailed description of the exposure calculations made by ATSDR.
Based on 1998 sampling data, ATSDR found that levels of PCBs ingested by consuming approximately one 8 ounce meal per month of catfish from Woods Reservoir are not likely to cause an unacceptable increased cancer risk, but do exceed the screening level denoted by the comparison value for noncancer health effects (such as developmental and neurobehavioral effects in children). It should be noted that ATSDR used conservative assumptions in calculating exposure dose as shown in Appendix B. The conservative nature of the assumptions are designed to provide the maximum degree of protection in evaluating whether consumption of fish might be hazardous to the most sensitive populations, such as pregnant women or children. Based on this evaluation, ATSDR agrees that the advisory against consumption of catfish is useful in order to ensure that people, children and pregnant women in particular, do not consume PCBs, even at the low levels present.(1)
If, in the future, PCB levels found in catfish continue to decline, ATSDR can work with TDEC and the Air Force to further reevaluate the necessity of retaining the advisory.
Based on levels of PCBs detected in snapping turtles, consumption of turtles is not expected to pose a health hazard. PCBs were detected in only two of eight turtles, and the maximum level detected (120 ppb) is well below levels that would pose a health hazard based on eating one meal per month (which is a conservative estimate of the likely frequency of consumption of turtle).
ATSDR agrees that continued public information and education is important in assuring that the community understands the nature and extent of the PCB contamination in fish at Woods Reservoir as well as the relative risk of consumption of low levels of PCBs versus the benefits of consumption of fish, a good source of low-fat protein.
Nature and Extent of Hazards
Two former artillery ranges are located on base, one north of the runways and one south of the AEDC industrial area. (Both of these areas are outside of the AEDC fence (See Figure 2). The ranges were used as training areas during World War II. The UXO that might be found in these former ranges include: mortar rounds, grenades, mines and small arms ammunition. Although no formal records have been kept and no ordnance surveys have been performed, these areas are potential locations for UXO (King, 1999a). Again, although no formal records on UXO are maintained at AAFB, there have been no incidents of injuries reported in the years following World War II, of injuries resulting from encounters with UXO. Occasional encounters by hunters or construction crews have been reported with the suspected UXO being collected and disposed of by AAFB emergency personnel (Munda, 1999b).
In addition, physical hazards such as remnants of abandoned structures, open manholes, and abandoned wells are present at Camp Forrest (Flatt, 1999).
Currently the AAFB procedure for notifying visitors is as follows: All personnel
employed at AAFB and visitors requesting access receive a detailed safety briefing
that includes UXO information. Figure 4 depicts the AAFB "Unexploded Ordnance
(UXO) Hazards Card" provided for visitors to these areas. Before they receive
their license, all hunters are briefed on the AAFB UXO hazard by the game warden.
This information is also presented in the annual TWRA pamphlet (Wildfeuer, 2000).
Evaluation of Potential UXO-related Public Health Hazards
There have been no recorded incidents of injuries resulting from encounters with UXO at AAFB in the fifty-five years since the end of World War II, when the firing ranges were in use. Although live UXO is always to be considered dangerous and is to be avoided when possible, the U.S. Army Corps of Engineers (USACE) have conducted nationwide studies into the hazards presented by UXO. The findings of this work are that there have been no recorded cases where people have been hurt or killed upon simply encountering UXO. There is a long history of people safely using areas cleared of UXO (QuantiTech, 1997, Wilcox, 1997). In these studies, it was found that accidents that have occurred have been either the result of trespassers removing UXO from the facility and tampering with the item, or the result of active disturbance such as a worker digging into buried UXO (QuantiTech, 1997, Wilcox, 1997). The USACE did not find documentation of accidental detonations occurring in cases where the item was not actively disturbed in the above manners. As a result of the findings of these investigations by USACE, it appears that it is not likely that incidental contact with UXO items, such as walking over buried items, or unknowingly stepping on such items located on the surface, will result in detonations (Wilson, 1997; QuantiTech, 1997). Even with this being the case, it is obviously prudent for visitors to AAFB to be provided with information concerning avoiding contact with any UXO items found within the former AAFB firing ranges, as well as instructions for procedures to be followed if UXO items are encountered.
Military UXO removal programs, such as those of the U.S. Army Corps of Engineers Center of Expertise for Ordnance and Explosives outline a clear and specific protocol including institutional controls, surveys and removals for former military facilities opened to non-military use (DOD 1999). The protocol, outlined below, is based on the types of uses intended. The purpose of the protocol is to ensure that all future users are aware of the potential for encounter with UXO, as well and understanding the potential for harm from any such encounters.
Finally, the USACE and all government organizations involved in the location
and removal of UXO agree that no removal, no matter how exhaustive and resource
intensive, can totally remove the possibility that some UXO may remain. Adherence
to the protocol as specified provides for the best possible assurance that former
military facilities can be used.
USACE UXO Clearance Standards
|The following are USACE suggestions for surveys and clearance, based on intended future use. The institutional and access controls suggested by the USACE are specific and rigorous.|
|Limited public access (e.g., park, nature preserve)
When the area is intended for to be used for limited public access, such as a park or nature preserve or for livestock grazing, with no construction or excavation envisaged.
- Local authorities should periodically review tax plats to ensure owners are notified and aware of the potential for UXO encounters.
- Provide deed notices, covenants and restrictions.
- Use local ordinances to control development and use appropriate government agency for clearance, permits, etc.
- Use the Memorandum of Agreement with USACE and state/local governments to ensure above actions are done.
In summary, although there is a reasonable likelihood that UXO items might still exist within the former firing ranges, it is unlikely that UXO items will detonate unless disturbed and handled without caution. In accordance with current AAFB policy, the public does have limited access to areas where UXO items might possibly be encountered. Because of continuing public access, ATSDR believes it would be prudent for AAFB to determine a reasonable program for mitigating the potential for harmful UXO encounters. In view of the findings of the USACE investigation cited above (Wilson, 1997; QuantiTech, 1997), AAFB should continue to develop and implement its program to educate visitors to the hazard presented in disturbing any such UXO items, and to educate the visitors concerning the appropriate procedures to avoid such disturbance. The following is an example of additional information that can be provided to visitors to the former firing range areas.
UXO SAFETY AND REPORTING
|It is important to understand how to react responsibly
in the presence of UXO.
|If you encounter UXO:
- Location (coordinates, street/grid names)
- Individuals present (names, organizations)
- Ordnance condition (buried, partially buried, exposed)
- Type of ordnance (rocket, grenade, projectile)
- Estimated size of ordnance (length, width, height)
- Distinctive features of ordnance (shape, color, markings)
- Nearby structures (landmarks, names, types, distance from ordnance).
(Excerpted and modified from: DOD, 1999)
To further decrease the likelihood of a UXO-related accident, AAFB should continue to target the educational effort to reach the specific audience most likely to collect or otherwise actively disturb UXO discovered within the former firing ranges, i.e. individuals who might be tempted to "collect" UXO items, or any one who might be involved in digging or excavation activities. Institutional controls such as controlled access and warning signage should be adequate to prevent access by uninformed visitors to areas where UXO might be encountered.
The USACE has expertise to assist in these determinations and could work with AAFB in developing these programs.
Evaluation of Potential Physical Hazards
Currently, the TWRA map of the AAFB Wildlife Management Area contains a warning concerning physical hazards at Camp Forrest. AAFB is working with TWRA to draft new language concerning UXO to be included in the next version of this map. In addition, AAFB is having signs made to post on the roads leading into the two former impact areas, warning of possible UXO (King, 1999b). These and further warnings such as flyers describing the physical hazards, and waiver forms delivered to all visitors at check-in points will further reduce the potential for injury. Additionally, information provided on the nature of physical hazards would appreciably reduce the likelihood of injury to uninformed visitors.
Summary of UXO and Physical Hazards Evaluation
In summary, ATSDR considers UXO and Camp Forrest physical hazards to be an indeterminate public health hazard for the present and future because there is an indeterminable potential for injury as it is not known how well-informed recreational users of AAFB are of these hazards. ATSDR concurs with AAFB's plans to increase notification efforts, and recommends that further efforts be made to ensure that all recreational users, particularly parents of children visitors, are notified of potential hazards.
Nature and Extent of Groundwater Contamination
Four groundwater contaminant plumes have been identified. These are: 1) the Coffee County Landfill plume, on the western boundary of the base; 2) the Camp Forrest plume, located in the eastern portion of the base; 3) the Northwest plume, located in the northwestern portion of AAFB; and 4) the Model Shop plume, located in the northern portion of AAFB. The following sections describe these contaminant plumes. Table 4 summarizes information from the four groundwater plumes.
Coffee County Landfill (Site 3, SWMU 5)
Groundwater contamination at the Coffee County Landfill was identified in 1988 sampling and further delineated in sampling from 1988-1992. In addition to the methane discussed in preceding sections, principal contaminants found in the shallow, intermediate, and/or deep aquifers under the landfill included tetrachloroethene (PCE), trichloroethene (TCE), methylene chloride, and benzene (see Figures 5 and 6). Although only low levels of contamination were found to have migrated across the Old State Route 55 based on monitoring well sampling, AAFB, as a precautionary measure, extended municipal water lines in 1992 to 11 residential properties located along the west side of State Route 55 across from the landfill (CH2MHill, 1995). AAFB constructed a pilot groundwater treatment unit in 1994 and updated it to increase production in 1997 (AAFB, 1998). Tests in the shallow and intermediate aquifers subsequent to the expansion of the treatment process indicated that the treatment unit was drawing sufficient water toward itself to locally override the regional northwest flow of groundwater. This flow reversal will help to prevent off-site migration of contaminated groundwater (Brandon, 1999).
In 1990, TDEC sampled private wells west of the landfill. All compounds detected were below ATSDR comparison values (TDEC, 1990). In 1998, AAFB sampled private wells at residences west of the landfill along the Old Tullahoma Highway. No landfill-related contaminants were detected in any of the wells (AAFB, 1999d). See Figures 5 and 6 for the boundaries of the Coffee County Landfill plume in the shallow and intermediate aquifers.
Camp Forrest Plume (Site 6, SWMU 8)
IRP Site 6 is the location of a former water treatment plant that served Camp Forrest. The concrete tanks of the abandoned plant were used as a disposal site for AEDC wastes from 1953 through 1980. Wastes included acids, chlorinated solvents, explosives, and rocket fuels, which were generally burned, ignited, or reacted. In 1980, the water treatment plant structures were demolished and filled with soil (AAFB, 1998).
Sampling in 1992 and 1994-1995 found groundwater contamination migrating toward the base's southern boundary. Principal groundwater contaminants include methylene chloride, trichlorofluoromethane (TCFM), 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethene (DCE), and benzene. An interim corrective measure, which included removal and treatment of contaminated water and capping of the site, was implemented in 1995, and a groundwater treatment unit was established in 1996. A security fence was also constructed around the site (AAFB, 1998).
Sampling was conducted in 1998 to further characterize the groundwater plume and test off-site wells and surface water (CH2MHill, 1998). The sampling results indicated that, in the intermediate and deep aquifers, the plume had migrated south/southeast along a bedrock fracture system (see Figure 7). The path of the plume roughly follows Spring Creek. In addition to monitoring well sampling, surface water and off-site private wells were also sampled. TCFM, 1,1-DCE, and PCE were detected in Spring Creek and nearby seeps and springs. These results indicated that contaminated groundwater is discharging into Spring Creek. Sixteen residential wells were tested; TCFM was found in three of these wells at a maximum concentration of 23.1 parts per billion (ppb) (well below levels of health concern). In November and December 1998, two additional residential wells were sampled; TCFM (30.29 ppb) and 2-butanone (12.74 ppb, estimated value) were detected in one. Both values are well below levels of health concern (RMEGs for children - 3,000 and 6,000 ppb, respectively). 2-Butanone is a component of the adhesives used on water well casing, and is often a residual from well installation (ATSDR, 1992). Because the well was newly installed, the presence of 2-butanone was deemed likely to be a byproduct of the adhesive used in well installation, and was not considered to be site related (CH2MHill, 1998; Dobson, 1999). Although the levels of TCFM are not considered to be a health concern, residents in the area of the plume are being connected to the Estill Springs water supply as a precautionary measure (Brandon, 1999).
Northwest Plume (Sites 1 and 22)
A plume of groundwater contamination has been identified moving northwest from the AEDC industrial area. IRP Sites 1 (a landfill and leach pit) and 22 (the AEDC Main Test Area) have contributed to this plume (CH2MHill, 1995; Brandon, 1999; Flatt, 1999). This contamination was identified as early as 1984. Principal contaminants include PCE, TCE, and other VOCs. Interim corrective measures put in place included groundwater treatment at Site 1 (installed in 1994), capping the Site 1 Landfill (completed in 1997), and groundwater treatment at Site 22 (installed in 1997) (AAFB, 1998). RCRA Field Investigation (RFI) sampling conducted in 1994 indicated that the plume had not migrated off site (CH2MHill, 1995).
In 1988, AAFB sampled 20 private water supply wells west of the base for organic compounds, with a method detection limit of 0.5 ppb. Chemicals were detected in only one well: TCE (3.82 ppb), 1,1,1-TCA (0.57 ppb), PCE (0.81 ppb), and TCFM (3.6 ppb). (All of these values are below levels of health concern.) AAFB installed a filter at this residence and continued periodic sampling for 5 years. Concentrations of TCE and TCFM at the well head declined over the sampling period, and all compounds were below the method detection limit for 1992-1993, except for one detection of chloroform at 4 ppb (below CV). AAFB then suspended the sampling program and turned over responsibility for maintenance of the filtration system to the resident (AAFB, undated). In 1992, AAFB sampled another private well west of the base, used for irrigation and drinking water, for organic compounds; TCE was detected at the detection level of 10 ppb. This value is above EPA's maximum contaminant level (MCL) of 5 ppb. In 1993, this well was resampled with no compounds detected above the detection level of 10 ppb (AAFB, 1993a,b). Based on a subsequent RCRA report (CH2M Hill, 1995), the Air Force did not believe that the contaminants were migrating from AAFB. As a result, the well owner was put in contact with the county water department but no further action was undertaken until further sampling was conducted (AAFB, 1993b).
In the fall of 1998, AAFB sampled 40 private water supply wells, 13 springs, and 12 surface water locations off site to the west and northwest of the base. Results indicated that a plume was traveling unpredictably along bedrock fractures (see Figure 8). VOCs were detected in two private wells. In the private well with the 1992 TCE detection, PCE was found at 6.97 ppb (above the MCL of 5.0). PCE was also detected in this well at an estimated concentration of 2.16 ppb (below the MCL). AAFB provided the resident with bottled water until a carbon filtration system was installed to treat drinking water. The other private well contained TCE at 8.32 ppb, PCE at 2.6 ppb (estimated concentration), and TCFM at 2.04 ppb (estimated concentration). This well is not used for drinking water because the residence is connected to the public water supply. VOCs were also found in four springs in an area of Crumpton Creek known as Rutledge Falls and in three surface water samples from Crumpton Creek downstream of Rutledge Falls (AAFB, 1999b). See the Surface Water and Sediment section for discussion of these findings.
The airfield water supply well at AAFB is potentially in the path of this plume, but it has been sampled regularly for TCE and has never had any detections (Holt, 1999).
Model Shop Plume (Site 8, SWMU 10)
Site 8 consists of Leaching Pit No. 1, which was used from 1950 to 1972 as a disposal area for waste solvents and acids from metal cleaning activities at the base's Model Shop. Groundwater contamination was found during 1988 and 1991 sampling; the primary contaminants were PCE and other chlorinated solvents (CH2MHill, 1995). Interim control measures to divert stormwater and treat contaminated groundwater and stormwater were completed in 1993. Closure of the PCE vapor degreaser building at the site occurred in 1994 and soil remediation was conducted in 1995 (AAFB, 1998).
RFI sampling in 1994 found VOCs at high concentrations in the shallow aquifer, but not in the intermediate wells sampled at the perimeter of the site. See Figures 9 and 10 for maps of each plume. High concentrations of two VOCs (PCE and 1,1,1-TCA) indicated that they are likely present as dense non-aqueous phase liquid (in other words, a pool of undissolved solvent) at the site (CH2MHill, 1995). A groundwater treatment unit was installed at the site in 1997 (AAFB, 1998). No off-base migration of this plume has been identified. However, few monitoring wells have been installed in the intermediate and deep aquifers and migration in these zones may be unpredictable (CH2MHill, 1999). During the fall of 1999, AAFB completed sampling approximately 150 off-site private wells located in the Bradley/Brumalow Creeks Area. The area is located northeast, east, southeast, and south of the AEDC and lies almost exclusively in the Elk River drainage basin. Preliminary results indicate that toluene was detected in two private well and chloroform was detected in a third private well, but at below levels of health concern. (USGS, 1999; AAFB, 1999g). See Figures 9 and 10 for delineation of the plume in the shallow and intermediate aquifers as determined by recent sampling.
Evaluation of Potential Public Health Hazards
Based on sampling results to date and precautionary measures taken, ATSDR concluded that contaminated groundwater in the area of AAFB does not pose a public health hazard. Appendix B provides detailed analysis of potential exposure. ATSDR concluded from dose calculations that although the health-based screening levels were slightly exceeded, the low levels of contaminants present in the groundwater were not likely to be sufficient to cause adverse health impacts. ATSDR recommends continued widespread monitoring of off-site private wells and on-site drinking water supply wells because of the unpredictable nature of plume migration in fractured bedrock. The basis for ATSDR's conclusions are provided below.
Coffee County Landfill
Contaminants have not been detected above ATSDR comparison values in private wells. Many residences near the landfill have been connected to the public water supply. Groundwater treatment and monitoring are ongoing. ATSDR concludes that there are no past or current public health hazards associated with groundwater contamination at Coffee County Landfill; assuming adequate monitoring is conducted, no future public health hazard is anticipated. As an additional safety measure, wells have been plugged at residences that have been connected to the public water supply. This will prevent both the consumption of potentially contaminated water and vertical methane migration.
Camp Forrest Plume
Contaminants have not been detected above CVs in private wells. Residences in the area of the plume are currently being connected to the public water supply as a precautionary measure. ATSDR concludes that there are no past or current public health hazards associated with the Camp Forrest groundwater plume; assuming adequate monitoring is conducted, no future public health hazard is anticipated.
Only two off-site residential water supply wells had contaminants detected above CVs. Only one of these wells is used for drinking water; AAFB installed a filter at this residence in 1998. ATSDR calculated the maximum exposure dose residents using this well could have received and found that it was below levels that would pose a health hazard (see Appendix B for more information). ATSDR concludes that there are no past or current public health hazards associated with the northwest plume; assuming adequate monitoring is conducted, no future public health hazard is anticipated.
Model Shop Plume
No off-base migration of this plume has been identified. Preliminary results of private well sampling also indicate that contaminants at levels of health concern were not detected. However, contamination may migrate unpredictably in fractured bedrock. Unless the final private well sampling results suggest otherwise, ATSDR concludes that there are no past or current public health hazards associated with the model shop plume; assuming adequate monitoring is conducted, no future public health hazard is anticipated.
Nature and Extent of Contamination
Various areas of surface and subsurface soil contamination have been found on base. (See Table 1 for detailed site-by-site information.) Contaminants found above CVs include VOCs, PCBs, PAHs, pesticides, and metals. Most of the sites are within the AEDC fenced area, although some soil contamination has been found at Camp Forrest.
Evaluation of Potential Public Health Hazards
Although contaminants were detected above ATSDR CVs at some sites, generally these sites are within the AEDC fenced industrial area, and thus little or no public exposure to these areas of contamination is expected. Based on available sampling data, sporadic incidental exposure of recreational users to surface soil contamination at Camp Forrest is not expected to pose a health hazard. Thus, soil contamination at AAFB poses no apparent public health hazard.
Nature and Extent of Contamination
Some contamination has been found in on-base surface water and sediment. (See Table 1 for detailed site-by-site information.) VOCs and metals have been detected above CVs in surface water; PAHs and metals have been detected above CVs in sediment. Off-base, constituents of the Camp Forrest groundwater plume have been detected in surface water (primarily Spring Creek) and in seeps and springs. Contaminants found were TCFM (maximum 33 ppb, below CV), PCE (1.2 ppb, below CV), and 1,1-DCE (maximum 1.8 ppb, above CV) (CH2MHill, 1998). Also, constituents of the northwest groundwater plume have been found in surface water (Crumpton Creek) and springs, specifically TCE (maximum 6 ppb, above CV) and PCE (maximum 1.5 ppb, below CV) (AAFB, 1999b).
Evaluation of Potential Public Health Hazards
Sporadic contact with contamination in on-base surface water and sediment is not expected to pose a health hazard. Although levels of some contaminants in off-base surface water slightly exceed drinking water CVs for long-term and frequent consumption, surface water is not used as a primary drinking water source, and the contaminant levels found do not pose a health hazard for recreational use of these water bodies. Therefore, ATSDR concludes that contact with surface water and sediment contamination associated with AAFB does not pose a past or current public health hazard. ATSDR recommends continued monitoring to ensure that contaminants do not exceed safe levels in the future.
ATSDR identified the following community health concerns through attendance at a RAB meeting during the 1999 site visit, contact with AAFB personnel, and review of newspaper articles.
- Concern about whether methane migration from Coffee County Landfill poses, or could pose, an ongoing health hazard.
AAFB has taken aggressive action to ensure that methane at Coffee County Landfill does not pose a public health hazard. AAFB has installed a methane collection and flaring system and conducts regular monitoring at the high school, where, to date, no methane has been detected. AAFB and Coffee County connected residence to the public water supply and plugged their wells to eliminate penetrations in to the zone of methane migration. These measures should be adequate to ensure that methane migration does not pose an ongoing health hazard.
- Concern about groundwater contamination.
In addition to sampling monitoring wells, AAFB has conducted extensive off-site private well sampling and has taken mitigating measures for residences found to have contaminated wells. Past exposure to low levels of contamination by residents with contaminated wells does not pose a health hazard. Most residences with private wells are now connected to the municipal water supply, thereby limiting potential current and future exposures. Residents whose operating private wells are not scheduled to be tested by AAFB should contact the appropriate government agency (such as TDEC, Coffee County, or Franklin County) for information if they wish to have their wells sampled.
- Concern about cancer rates in the area.
In assessing the threats to the public's health, ATSDR first examined the potential exposure pathways related to a site. If ATSDR determined that a completed exposure pathway poses a public health threat, ATSDR may gather health outcome data to complement the environmental and exposure data. In evaluating available data from the AAFB site, ATSDR has not found a completed exposure pathway posing a public health hazard. Based on the data available for review, ATSDR does not believe that contaminants from the AAFB site are responsible for health problems such as cancer. However, further private well testing is necessary to verify that no exposures of health concern exist.
- Concern about lupus rates in the area.
As stated above, ATSDR has not identified any exposure pathways through which the public may be exposed to contamination at unsafe levels. However, to further address this community concern, ATSDR conducted a literature review concerning possible causes of lupus.
Systemic lupus erythematosus (SLE), commonly referred to as "lupus," is a relatively common disease, affecting between 500,000 and 750,000 people in the United States (Lahita, 1992). Ninety percent of cases are in women, usually of childbearing age, and the disease is more common in some minority populations than in whites (Hahn, 1994). Lupus is an autoimmune disease, or one in which the immune system attacks the body's own tissues, and it is multisystemic, potentially affecting any and every organ system (Lahita, 1992). Lupus results in episodes of inflammation in joints, tendons, and other connective tissues and organs (Berkow et al., 1997).
The cause of lupus is unknown, but it is currently believed that lupus probably results from interactions between susceptibility genes and the environment (Hahn, 1994). Some of the environmental factors that have been investigated are infectious agents (viruses and bacteria), drugs and chemicals, ultraviolet radiation, and diet. There is much suggestive evidence that one or more infectious agents may contribute to initiating lupus, but full proof of this hypothesis has not yet been obtained. Ultraviolet radiation can exacerbate lupus, although it is not thought to induce it (Cook and Christian, 1992).
Some drugs, such as procainamide, hydralazine, isoniazid, methyldopa, quinidine, and chlorpromazine, can induce a syndrome resembling SLE (Hess and Mongey, 1993). Drug-induced lupus differs significantly from spontaneous SLE in its clinical manifestations and the autoantibodies present (Hahn, 1994). Most patients with the drug-induced syndrome improve within a few weeks of ceasing to take the drug (Hahn, 1994). Patients with spontaneous lupus do not appear to have an increased risk from drugs implicated in drug-induced lupus (Steinberg et al., 1991). Some studies have found links between chemicals (such as hydrazine, a hair dye) or constituents of foods (such as L-canavanine, found in alfalfa sprouts) and lupus (Hess and Mongey, 1993). Researchers have noted that many of the drugs and chemicals implicated in lupus causation are aromatic amines and hydrazines, which could indicate a common mode of action (Hess and Mongey, 1993). The existence of drug-related lupus has prompted some researchers to hypothesize that drugs or chemicals could play a role in inducing "spontaneous" lupus, but this is only theorizing at this point, with little or no scientific information to support the theory (Steinberg et al., 1991). Many of these studies failed to distinguish whether the cases of lupus identified resembled drug-induced lupus or spontaneous SLE. In summary, there is little existing evidence to link low levels of hazardous chemicals in the environment with lupus.
ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of their water, soil, air, or food. Children are at greater risk than adults from certain kinds of hazardous substances emitted from waste sites and emergency events. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. They are shorter than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care.
ATSDR evaluated the likelihood for children living on base or in the neighboring communities to be exposed to AAFB contaminants at levels of health concern. When screening levels of contamination in media to which children could be exposed, ATSDR used the Environmental Media Evaluation Guidelines for children, who are considered the most sensitive segment of the population. On the basis of the available data, ATSDR did not identify any chemical contamination that would pose a hazard to children, assuming that pregnant women and children follow the advisory against consuming catfish from Woods Reservoir. (Studies have indicated that ingestion of PCBs by a pregnant woman may affect her child's development after birth.) Children may be at greater risk than adults for some of the reasons noted above. Further private well sampling is necessary to confirm that no exposure at levels of health concern has occurred; ATSDR will evaluate these data when they become available.
ATSDR identified two potential physical hazards that could possibly pose hazards to children if exposure occurred: methane migration from Coffee County Landfill (because of the proximity of a high school) and UXO in publicly accessible areas. The mitigation and monitoring that AAFB has undertaken will ensure that methane does not pose a threat to children attending the high school. ATSDR recommends that AAFB take precautions to protect children from potential UXO on the base, including educating children not to pick up suspicious objects.
1. Studies have indicated that ingestion of PCBs by a pregnant woman may affect her child's development after birth. Children should adhere to the advisory because, as compared to adults, they receive a proportionally greater dose of PCBs relative to their body weight from consuming the same amount of fish. Also, because they are still developing, children are at potentially greater risk for certain types of developmental health effects.