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PUBLIC HEALTH ASSESSMENT

USA DEFENSE DEPOT MEMPHIS
MEMPHIS, SHELBY COUNTY, TENNESSEE

ENVIRONMENTAL CONTAMINATION
AND ENVIRONMENTAL EXPOSURE PATHWAYS

Introduction

This section examines each of the environmental routes (water, sediment, air, soil, foodchain) to determine whether contamination is present, and if people in the community are exposed to (or in contact with) the contamination. If people are exposed to contamination in any of the media, we will evaluate whether there is enough contamination to pose a threat. This analysis will follow the pattern depicted in Figure 1 to systematically evaluate each of the environmental routes.

Each section contains a summary box numbered to match the routes as shown in Figure 1.

Evaluation of Possible Water Routes

People can be exposed to contaminated water by drinking it, bathing or swimming in it, or in some cases, breathing vapors from water (for instance, steam from a hot shower). There are two main water pathways to consider. These pathways are:

  • groundwater, that is, water from wells, either private wells or public water supply wells,
  • surface water, that is, ponds, lakes, creeks. The sediment on the bottom and along the edges of these water bodies will be considered along with surface water, since any exposure to contaminated sediments would occur in the vicinity of the surface water.

Groundwater

Groundwater is actually underground water. People use this water from either private wells or municipal well systems.

Currently there are no known private wells in use within one mile of DDMT (2). Municipal water supplies have been available to the homes and businesses in the vicinity of DDMT for domestic use since the 1940's to early 1950's (12).

The shallow groundwater aquifer under DDMT is contaminated (2,4). Memphis Light, Gas and Water Division (MLG&W) obtains water from the Memphis Sand Aquifer, not the overlying shallow aquifer. The primary contaminants are volatile organic compounds (VOCs) (mainly cleaners and solvents), metals, petroleum products and pesticides. The following sections will describe the levels of contamination and the possibility of exposure.

The shallow aquifer groundwater has not been used by DDMT (9). Domestic water supplies for the facility have always been obtained from municipal sources. As stated above the municipal water supply comes from the deeper aquifer, the Memphis Sand Aquifer. MLG&W has in place a monitoring and treatment program for the water supply. MLG&W does monitor for the types of chemicals that are possible contaminants from DDMT. Additionally, MLG&W has in place plans to treat the water supply, if necessary, to keep these chemicals from reaching the public (5).

Remedial plans for DDMT include a program of pumping the contamination for the shallow aquifer and treating the water to further limit the possibility that contamination reaches the water supply (4). These factors greatly limit the possibility that people have been exposed to contaminated groundwater from DDMT.

- Past Groundwater Effects

The only location where contaminated groundwater is suspected to have moved offsite is immediately to the west of Dunn Field (2). The following describes the primary contaminants that might be of concern, if they were present at high enough concentrations, and if people drank them regularly for extended periods of time.

According to DDMT disposal records in the 1990 environmental investigation and the 1995 Draft Final RI\FS Work Plan (1,2), with the exception of the chemical agent destruction, very little waste disposal activity occurred before 1954. Material disposed before 1954, listed in the 1990 environmental study, includes food waste, construction material, and "combustible material", presumably not hazardous chemicals, since such chemicals are specifically listed as such in the records. The materials listed as disposed prior to 1954 do not appear to represent a chemical contamination hazard to groundwater. This date is important in that municipal water has been provided since 1953 for the area immediately west of Dunn Field (8). Prior to 1953, water would have been obtained from private wells.

According to the 1990 environmental study (2) and the 1995 draft final work plan for Dunn Field (1), groundwater movement from Dunn Field is to the west. However, since municipal water has been provided to the area west of Dunn Field since 1953 (8), it is unlikely that neighbors to DDMT were exposed to a hazard from contaminated groundwater.

DDMT records show that mustard agent was destroyed and disposed at Dunn Field in 1946. According to available information, the mustard was treated in a bleach slurry and essentially "deactivated" (10). Mustard agent that is buried without being treated will break down into a number of less toxic chemicals, such as thiodiglycol and hydrochloric acid. The primary problem that would result from exposure to these chemicals (at high enough levels) is skin irritation. The neutralizing process can break the compound into a number of less toxic compounds, including mustard sulfone (bis (2-chloroethyl) sulfone) and half-mustard (2-chloroethyl, 2-hydroxy ethyl sulfide) (11,13) and decreases the amount of the natural breakdown chemicals that will be produced.

According to the ATSDR Mustard "Gas" Toxicological Profile (13), mustard agent is not soluble in water. For this reason, any mustard agent that remained would not be likely to move offsite in the groundwater. Also, the principal breakdown products of mustard agent tend to deteriorate within a matter of weeks, so they would not likely be health threats. Consequently, the mustard agent destroyed at Dunn Field was not a threat to public health in the past.

- Present-Day Groundwater Effects

Allen Well Field is the source of the municipal water supply for the area around DDMT. This facility is located about 1/2 mile west of DDMT. These wells produce water from the Memphis Sand Aquifer. (Appendix B provides more details on the groundwater aquifers in the vicinity of DDMT.) To date, contamination related to DDMT has not been found in MLG&W wells. Contamination appears to be under DDMT and in limited areas immediately outside the base (2). Table 1 lists the contaminants found in groundwater under Dunn Field. DDMT is developing a plan, with oversight by EPA and TDEC, to pump and treat contaminated water from this shallow aquifer. This interim measure will decrease by half the migration of the contaminant plume (2).

The municipal water supply is tested for contaminants (primarily metals and VOCs) and treated, if necessary, according to EPA drinking water standard requirements (5,8). At this time, there have been no hazardous chemicals from DDMT detected which present a danger. As long as people use the readily available municipal water supplies, the groundwater contamination from DDMT is not a threat to human health.

Surface Water

Contamination of water in the DDMT drainage ditches would be caused when rainwater runoff from paved areas or areas with contaminated surface soil enters the ditches. However, hazardous waste buried below the surface at Dunn Field, is not likely to contaminate surface water or cause contamination to accumulate in the drainage ditches. According to the Remedial Investigation (RI) (17), the water table under the DDMT is about 40 feet below land surface. Rainwater that soaks into the ground (and does not run off) will infiltrate through the subsurface to the watertable, 40 feet below the surface. For this reason, it is not likely that this water could enter the overlying drainage ditches.

- DDMT Golf Course Ponds

Surface water bodies within the boundaries of DDMT are the Golf Course Pond and Lake Danielson. Surface water from both of these ponds were sampled in the 1980's and were found to be contaminated, primarily by pesticides and metals, with some polynuclear aromatic hydrocarbons (PAHs). The main source of the pesticides is suspected to be chemicals used to maintain the golf course and pesticides stored in a shed adjacent to the Golf Course Pond. Some of the metal and PAH contamination is probably the result of runoff from paved areas and roads within DDMT. (Both PAHs and metals can be components of the paving material used in roads, and can also come from vehicle exhaust). In 1986, both ponds were closed to all recreational activities. Even though the present surface water contamination levels are low, both have remained closed (2). There is no information of significant exposures to contaminants prior to their closing, and no indication that public health has been affected. For these reasons, it is not anticipated that the contamination of these two water bodies poses a threat to public health.

- Drainage Ditches

Other surface water pathways that need to be evaluated are the ditches that drain from the site. These ditches are also possible routes for contamination to reach the waters and sediment of Cane and Nonconnah Creeks. According to RI information, several ditches or streams drain from DDMT to Cane or Nonconnah Creeks. These are shown in Figure 6 (1).

An open, concrete-lined channel runs north from Dunn Field into Cane Creek. Two unlined ditches run west from Dunn Field through the Rozelle Street area. During a February 1995 site visit by ATSDR, these were both observed to contain relatively small volumes of water. Tarrant Branch runs west from the main facility, eventually entering Nonconnah Creek to the south. Drainage ditches run from the Golf Course Pond and Lake Danielson south, entering Nonconnah Creek. An unnamed ditch runs east from the Main Installation to the storm sewer system. Each of the ditches except Tarrant Branch are dry for at least part of the year (2).

Since there is little chance that people would drink water from the drainage ditches in any significant quantity, the only possible exposure concern would be dermal exposure (contact with the skin). There are few studies on dermal exposures of people to low levels of these chemicals. However, in general, this is much less likely to be a health problem than exposure by drinking the contaminated water. This is because these chemicals are not as easily absorbed into the body through the skin as they would be if they are taken in by drinking water.

Because the most likely exposure would be from walking beside or wading in the ditches, the most likely contact with the chemicals would be a person's feet and possibly hands. These are the parts of the body that are the least able to absorb contaminants (18). Also, it is important to remember that for exposure to a low level of contamination to be a problem, the exposure has to occur frequently (generally daily) over a long period of time (many years) (18).

Sixteen drainage ditch samples were collected for the 1990 RI (2). These samples were collected onsite, from each of the ditches that drained from DDMT to offsite. The contaminants found in these samples are listed in Table 2. With the exception of the pesticides DDT and DDE, the VOC bis(2-ethylhexyl)phthalate (DEHP), and the PAHs fluoranthene and pyrene, levels were lower than EPA drinking water standards. For the contaminants found in these ditches, dermal exposure is therefore not a public health concern.

DDT and DDE do not enter the body through the skin very easily, so that exposure to these chemicals in the small amounts present in the southern onsite drainage ditches is not likely to be a public health problem (19). DEHP is not easily absorbed through the skin, particularly in small amounts, such as are present in these onsite ditches (20). The amount of DEHP present also does not present a public health threat.

If enough fluoranthene and pyrene are present, dermal exposure can result in a noticeable skin irritation. However, neither chemical is believed to cause cancer or other long-term problems (16). These contaminants are not present at levels that would be considered health threats. Based on the low levels present, and the limited possibility of contact, is not likely that these PAHs present a health threat.

There is currently no information available on contamination in the ditches on western side of Dunn Field. Surface water contamination is not likely to be a problem in ditches draining Dunn Field since, for the most part, the contamination is buried below the surface, and is not likely to affect rainwater runoff. Also, any rainwater soaking into Dunn Field would percolate downward to the water table, which is about 40 feet below ground surface in the DDMT area. It is highly improbable that rainwater percolating into Dunn Field could move laterally off Dunn Field to get into the drainage ditches. The ditches themselves will be "recharged" by groundwater within 10 to 20 feet of their streambanks and would not be affected by groundwater contaminants under Dunn Field.

Additionally, VOCs and metals are the contaminants buried at Dunn Field. VOCs were found at elevated levels in the groundwater samples. Several metals were also detected at elevated levels. Table 1 shows these contaminants. In general, if VOCs had been present at one time in surface soil, they do not remain in surface soils for any length of time and therefore would not be present to be carried in rainwater runoff into the ditches. Also, VOCs are not easily absorbed through the skin in amounts large enough to be a problem, particularly when amounts are as low as could possibly be present in the drainage ditches (23,24,25,26,27,28,29).

The metals found in the groundwater samples at Dunn Field are also not generally a problem in terms of contact with the skin. This is especially true when these metals are in water and are present in such small amounts (30,31,32,33,34).

In summary, it is unlikely that hazardous waste buried in Dunn Field is carried offsite by rainfall runoff. It is not likely that surface water would be contaminated as much as groundwater.

The actual contamination of surface water in the ditches has not been determined. Additional ditch water sampling planned for DDMT will provide information on any contaminants present. However, using the assumptions made above, it is unlikely that skin contact with the ditch water (or sediment) is harmful.

- Nonconnah and Cane Creeks

No information is available on the possible contamination of Nonconnah Creek or Cane Creek. However, considering the relatively low levels of contamination found in surface water onsite, and the dilution that would occur when the contaminants reached these creeks, there is very little chance that public health could be affected by contaminants from DDMT in these creeks. Additional sampling of the drainage ditches will provide some information on the likely levels of contamination that might reach these creeks.

Figure 6
FIGURE 6 -- DDMT Surface Drainage

Table 1: Water Analysis for DDMT Drainage Ditches. (2)
Sample Location Sample Number Chemical Concentration ug/l *ATSDR Comparison Value
North boundary Dunn Field SW-1 None detected

North boundary Dunn Field SW-16 None detected

West boundary of DDMT SW-2 VOCs\SVOCs
Methylene chloride
Acetone
1.0
5.0
5 MCL
1000 RMEG
Pesticides
Endosulfan 0.16 20 EMEG
Metals
Barium
Chromium
Copper
Zinc
76.0
20.0
23.0
29.0
700 MCL
100 MCL
1300 MCL
2000 LTHA
West boundary of DDMT SW-14 VOCs\SVOCs

2-Butanone
Acetone
Benzoic acid
bis(2-ethylhexyl)phthalate
4.0
110.0
3.0
3.0
6000 RMEG
1000 RMEG
40000 RMEG
6 MCL
Metals
Barium
Chromium
Zinc
42.0
10.0
36.0
700 MCL
100 MCL
2000 LTHA
Southwest corner of golf course SW-9 VOCs\SVOCs
Methylene chloride
Acetone
bis(2-ethylhexyl)phthalate
1.0
18.0
1
2.0
5 MCL
1000 RMEG
6 MCL
Pesticides
4,4'DDT 0.16 0.1 CREG
Metals
Arsenic
Lead
Barium
Cadmium
Copper
Silver
Zinc
47
295.0
60.0
5.0
68.0
13.0
400.0
50 MCL
15 EPA Action Level
700 MCL
5 MCL
1300 MCL
50 RMEG
2000 LTHA
Southwest corner of golf course SW-12 VOCs\SVOCs
Acetone
Benzoic acid
bis(2-ethylhexyl)phthalate
N-Nitrosodiphenylamine
4.0
6.0
3.0
7.0
1000 RMEG
4000 RMEG
6 MCL
7 CREG
Pesticides
4,4'DDE
4,4'DDT
0.65
2.2
0.1 CREG
0.1 CREG
Metals
Arsenic
Lead
Barium
Cadmium
Chromium
Copper
Zinc
30.0
100.0
98.0
19.0
20.0
20.0
150.0
50 MCL
15 EPA Action Level
700 MCL
5 MCL
100 MCL
1300 MCL
2000 LTHA
Golf Course Pond drainage ditch (south boundary of DDMT) SW-10 VOCs\SVOCs
Acetone
bis(2-ethylhexyl)phthalate
Di-n-butyl phthalate
Di-n-octyl phthalate
N-Nitrosodiphenylamine
Pyrene
1.0
7.0
3.0
3.0
7.0
3.0
1000 RMEG
6 MCL
1000 RMEG
none
7 CREG
300 RMEG
Pesticides
4,4'DDE 0.14 0.1 CREG
4.4' DDT 0.27 0.1 CREG
Metals
Barium
Copper
Zinc
26.0
25.0
81.0
700 MCL
1300 MCL
2000 LTHA
Golf Course Pond drainage ditch (south boundary of DDMT) SW-11 VOCs\SVOCs
Acetone
Total Xylenes
bis(2-ethylhexyl)phthalate
Butyl benzyl phthalate
Fluoranthene
Pyrene
4.0
1.0
3.0
3.0
2.0
3.0
1000 RMEG
20000 RMEG
6 MCL
100 MCL
400 RMEG
300 RMEG
Pesticides
4,4' DDE 0.88 0.1 CREG
4,4' DDT 1.9 0.1 CREG
Metals
Lead
Barium
Copper
Zinc
50.0
55.0
30.0
110.0
15 EPA Action Level
700 MCL
1300 MCL
2000 LTHA
East boundary of Dunn Field SW-15 None Detected

*NOTE: 1. ATSDR Comparison Values are generally derived assuming long-term (many years) exposures. Infrequent and short-term exposure would not result in the same chance of harm. Comparison Values defined in Appendix C. 2. Values are for DRINKING WATER therefore more protective than for dermal contact. This is because chemicals are generally more easily absorbed into the body by ingestion than by dermal contact.

Evaluation of Possible Sediment Routes

The only sediments that might be a concern are those in the drainage ditches. However, the levels of contamination would have to be far greater than the levels found in surface water at DDMT to be a public health problem.

No sediment samples have been collected in the drainage ditches. However, sediment samples collected from the Golf Course Pond and Lake Danielson detected PAHs, VOCs, pesticides and metals. The Golf Course Pond sediments contained N-Nitrosodiphenylamine, PAHs and pesticides at concentrations that might be a concern for soil. Even for these contaminants there is no health threat from infrequent and short-term exposure. More important however, they are not a hazard since there is no opportunity for contact by people with these sediments.

As stated above, the contamination of the Golf Course Pond sediments is not a threat to public health since there is no contact by the public with these sediments. However, the contaminants in these sediments and in onsite ditch samples can give an indication of what contaminants might be found in offsite ditches which drain them.

The upcoming sample and analysis of offsite ditch sediment samples will provide information on the potential for contamination in these ditches. However, for these sediments to be a threat to public health, the levels of contamination would have to be much higher than the levels of contamination found in onsite ditch water and pond sediment samples.

Evaluation of Possible Air Routes

The normal operations , such as storage and warehousing activities, that occurred at DDMT in the past are not industrial activities which cause large amounts of air contamination. There are not currently any activities occurring at DDMT which could cause air contamination that would be a threat to public health. This determination is based on the type of activities (storage and warehousing) which are currently occurring at DDMT, and the fact that these activities are regulated by the state and EPA under RCRA. Under delegated authority of the Clean Air Act (Amended 1990), the Memphis\Shelby County Health Department is the permitting agency for air emissions at DDMT. Any such emissions would be regulated and limited to safe levels by the Clean Air Act (21). As a part of the CERCLA process, the EPA requires that air quality be protected during any remedial activities that occur at DDMT (22).

The following are activities related to air contamination that occurred in the past that have caused community concerns.

PCP Diptank Operation

A possible past air contamination issue at DDMT that requires evaluation is the pallet-dipping operations at DDMT. The dip tanks were located near the center of the Main Installation, about 1,200 feet from the nearest DDMT boundary (See Figure 4). From the 1960's until 1985, pallets were dipped in the preservative pentachlorophenol (PCP), in an enclosed diptank building, and stacked outside to dry. This operation ceased in 1985. In 1986, under the direction of EPA, PCP-contaminated soil was removed (2).

No air samples were collected during the time the diptank was in operation. However, there is no evidence in DDMT occupational health records that worker health problems occurred from exposure to PCP. Although this is not clear-cut evidence that no worker exposures occurred, it provides some support that such exposures did not result in an obvious worker health problem. As such it is not likely that enough air contamination from PCP occurred to be a problem for neighbors. Also, since the diptank operation was located relatively distant from DDMT boundaries, it is unlikely that neighbors would have been exposed to harmful amounts of PCP through air emissions.

Finally, it is known that PCP is not likely to become airborne in significant amounts from contaminated soil, even if it is disturbed, as would occur during excavation. It is therefore not likely to have been a public health problem during soil removals (35).

Sandblasting Facility

Another site that was evaluated is the sandblasting area, located in the area of Building 1088, about 300 feet from the western boundary of the Main Installation (See Figure 4). Paint with metallic components was stripped from various types of machinery in this building. Operations were upgraded in the late 1980's to reduce the possibility of airborne transport of metals from this source. No air monitoring records are available for metal in the area of these operations. However, a soil analysis would provide evidence on whether metals in dust had been carried by air currents to the neighborhood surrounding the sandblasting buildings. Sampling of surface soils in the area would provide information on whether metal concentrations (in the soil) are higher than normal. ATSDR has asked that soil samples be collected and analyzed as a part of the ongoing RI activities.

Mustard Agent Destruction

An issue that has caused some community concern is the report that mustard agent had been buried at DDMT following World War II. Documents from the post-war period suggest that several thousand pounds of mustard were destroyed and buried in 1946 (10,36). This material was from twenty-nine 500-pound aerial bombs captured from Germany during the war. The mustard was drained into bleach slurry pits, neutralized (by the bleach solution) and buried (37). The method used to decontaminate these weapons is generally considered a safe and effective means of neutralizing mustard (38). (The bleaching agent and resulting breakdown products can cause skin irritation if exposures to high enough levels occur.) Any remaining mustard agent would have most likely deteriorated in the time since its burial. In the event that any residual amounts of mustard did not deteriorate in the last 49 years, there is little possibility for air contamination from these burial sites, as long as the required procedures are followed during any digging (38). In view of these facts, air contamination from the 1946 mustard agent burial should not be considered a hazard to public health.

Chemical Agent Identification Kits

In a related issue, DDMT records reveal the disposal of about six chemical agent identification kits. These kits were used for training military personnel in detection of various chemical warfare agents. Although the specific type of kit discarded is unknown, these kits can contain test tube-sized vials of diluted chemical agents, including mustard agent, phosgene, lewisite and chloropicrin (39).(1) It should be emphasized that the amounts believed to be present in these kits is small and, if released, would not be a threat over an area as large as Dunn Field.

However, there is concern that remedial activities such as well drilling or excavation may uncover and damage these kits, causing a release. Based on the small amounts present in these kits and the fact that they are in a dilute form, we have concluded that the potential harm would be restricted to the personnel involved in the drilling or excavation activity. The health of the community would not be affected by excavation of these kits.

Federal law requires that any activity involving the removal, transport or disposal of chemical agents be coordinated with the U.S. Army Chemical Demilitarization Program (USACDP) and the National Center for Environmental Health (NCEH) of the Centers for Disease Control and Prevention (CDC). These two organizations develop safety procedures for chemical agent removal. Safety programs include plans for; drilling and excavation that minimize the possibility of an accident, monitoring during activities to detect any leaks that occur, limiting the spread of any contaminants that might leak, and emergency response and emergency medical procedures, if needed. DDMT is working with these agencies to insure that safety procedures are used that are protective of the health for both workers and the surrounding community (41,42).

"Spandome" Collapse - 1988

Due to strong winds and heavy rains, a fabric structure known as a "spandome" partially collapsed on the morning of January 19, 1988. The structure was located on the western side of the Main Installation. Memphis\Shelby County emergency response teams reported the detection of airborne hazardous chemicals. The materials released were solvents, such as toluene and xylene (43). The Spandome floor was concrete, with concrete bermed perimeter. Therefore, released chemicals were contained within this concrete area.

The Memphis Fire Department states that the berm held the spilled material. Impact on the neighborhood was termed "neutral" in the Fire Department report of the spill response (43). Based on this information, the incident involving the collapse of the spandome is not believed to have had a negative impact on public health.

Evaluation of Possible Soil Routes

There are several areas within DDMT that have contaminated soil (2). However, access to these areas is controlled by warning signs, fencing, or paving. As a result, the areas containing contaminated soil are not a threat to public health. Currently, DDMT is conducting studies required by the U.S. EPA and the state to measure the contamination. Based on the results of these studies, cleanup activities will be completed to protect the public health from any harmful contaminants (44).

Evaluation of Possible Foodchain Routes

Concern has been expressed that contamination could affect food grown in home gardens in the area around Dunn Field, and possibly in the area of the ditch draining west from the Main Installation. The following factors are important in considering the possibility of food contamination:

  • only certain types of contaminants are taken up or remain in the animal or plant to be a threat to people who may eat them,
  • for the vegetables to be contaminated, the roots must be in direct contact with contaminated soil or water for a large part of the growing season,
  • the amount of contaminant in soil or water must be high enough to be taken up by plants or animals in amounts that would be harmful to people who eat them,
  • for locally grown food contamination to be a problem, people would have to have regularly and frequently eaten large amounts of contaminated vegetables for a number of years, and
  • as stated in the Surface Water section above, it is very unlikely that groundwater contaminants from Dunn Field have leached into the drainage ditches.

As described in the surface water and sediment sections above, the drainage ditches around Dunn Field are not likely to have large amounts of contamination in either water or sediment. At Dunn Field the main contaminants of interest are: mustard agent, VOCs, and metals. For the ditch draining west from the Main Installation, the main contaminants are VOC and metals.

The mustard agent was neutralized in 1946. Even if some mustard agent had survived the neutralization, the chemical composition of mustard agent is such that it is highly unlikely that the mustard would have migrated through the groundwater into the drainage ditches and even less likely that it would have been absorbed by plants or animals and passed on to people when these plants or animals were eaten (13).

The VOC solvents would not migrate through surface water and do not easily accumulate in plants or animals, so that it is unlikely that they would be a health problem to people through this route (23,24,25,26,27,28,29,45). There is little information to suggest that plants can accumulate enough metals to be a human health problem, especially at the low levels present, as indicated by the samples collected to date (Shown in Table 2)(30,31,32,33,34).

It may not be possible to make a definite statement about past contamination from this source. However, sediment samples from the drainage ditches will provide present levels that can be evaluated.

QUALITY ASSURANCE AND QUALITY CONTROL

In preparing this Public Health Assessment (PHA), ATSDR relies on the information provided in the referenced documents. The Agency assumes that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analyses and the conclusions drawn in this document are determined by the availability and reliability of the referenced information.

The environmental data presented in this public health assessment is from the 1990 report and from the follow-up RI planning documents (1,2). Generally, the methodology used in these reports is appropriate for characterizing contamination at DDMT. Additional information collection is planned for the follow-up RI. This work is scheduled to begin in the Fall of 1995. This information will be evaluated by ATSDR. Conclusions and Recommendations of this PHA will be modified if needed.

PUBLIC HEALTH IMPLICATIONS

General

ATSDR considers that a confirmed exposure pathway for people to contaminants is necessary to suggest that a public health threat exists. In order to evaluate the effect on public health of contaminants at NPL sites, ATSDR focuses on examining whether people could have been exposed to (in contact with) or are being exposed to the contaminants.

For health problems to result in the community surrounding a hazardous waste site, contaminants must exist in the environment, contaminants must be in places where people in the surrounding community might come in contact with them, and, if there is exposure, there must be enough contamination to affect the health of people.

It is very important to remember that for harm to occur, each of the conditions listed above must occur. The American Cancer Society publication Cancer Facts and Figures - 1995, dealing specifically with cancer risks, states; "Although many toxic chemicals contained in such (hazardous) wastes can be carcinogenic at high doses, most community exposures appear to involve very low or negligible dose levels. The degree of hazard (for cancers or other illness) posed depends on the amount of contaminant and the exposure, or "dose" that a person receives. When concentrations and exposures are high, a hazard may exist. Where concentrations are low and exposures are limited, hazards are often negligible" (47).

Health Outcome Data

Health outcome data (HOD) record health effects that occur in populations. The data can provide information on the general health of the community living near a hazardous waste site. It can also provide information on patterns of specified outcomes. Some examples of health outcome databases are tumor registries, birth defects registries, and vital statistics. Since there is very limited potential for exposure resulting from activities at DDMT, extensive health outcome data would not provide useful information for this health assessment.

Currently, the Tennessee Department of Health (TDH) is looking at information from the state cancer registry. TDH is the appropriate agency to do this work, since the information available is TDH data. This work is intended to study the amounts of various cancers occurring in the census blocks that include DDMT and vicinity. Although this work may provide information about the types of cancers occurring near DDMT, it will not be possible to identify specific causes of those cancers (46).

COMMUNITY HEALTH CONCERNS

The following concerns have been identified by ATSDR through meetings, correspondence, telephone conversations and information from DDMT, EPA, state and local agency files and community members. A number of concerns were expressed in comments to the draft version of this report. They are included in summarized form. Additionally, ATSDR personnel attended a DDMT public availability session on August 10, 1993, and citizens' Restoration Advisory Board meetings on October 20, 1994, and February 16, 1995. At these sessions ATSDR personnel had the opportunity to meet with numerous members of the public to discuss health concerns of members of the community. ATSDR has also reviewed the transcripts of a DDMT public meeting held May 28, 1993 and the federal facilities agreement public hearing held December 20, 1994. These transcripts include a number of health-related concerns.

Concerns include those which relate specifically to DDMT and general health concerns that may not relate to contamination from DDMT. The order that these following concerns are addressed does not imply any priority assigned by ATSDR to the questions.

  • Drinking contaminated groundwater, especially people living west of Dunn Field.

Memphis Light, Gas and Water Division (MLG&W) has provided water for domestic use to DDMT neighbors since the 1940s and 1950s. This water comes from a deeper aquifer than that which has shown contamination from DDMT. MLG&W regularly monitors its water wells and tests for all contaminants, as required by EPA and state regulations. Although it is not possible to make definite statements about levels of contamination in groundwater in the past, MLG&W was providing water supplies to residents very early in the history of DDMT and Dunn Field. Also, DDMT records show that there was only limited disposal activity at Dunn Field prior to the time that municipal water was made available. For this reason, the period of time that residents might have been exposed to contaminants is relatively short and the amount of possible contamination would have been very small.

  • Eating vegetables grown in home gardens.

Because there is no specific information available, it is not possible to make definite statements about the past exposure to people through eating vegetables watered with contaminated water. However, it is unlikely that significant amounts of contamination have reached the areas surrounding DDMT via the drainage ditches. It is therefore not likely that the vegetables have been exposed to high enough levels of contaminants to be hazardous. Also, vegetables do not easily accumulate the types of chemicals that might have been present.

  • Contact with contamination in ditches, especially by children at play.

Since offsite samples have not been collected and analyzed, definite statements can not be made about past exposure, it is unlikely that significant amounts of contamination could have reached the drainage ditches. Also, dermal exposure or other incidental contact is not likely to present health problems for the chemicals that would be present in, at worst, very low levels in these ditches.

  • Concern over mustard agent disposed at Dunn Field.

Based on records of the disposal activity, it appears that the mustard agent destroyed and disposed at Dunn Field did not in the past and does not today represent a threat to public health. During disposal activities, the mustard agent was broken down into components that are much less hazardous than the original material. The neutralized material would not present a threat to groundwater or surface water in the area of DDMT. The bleaching agent and resulting breakdown products can cause skin irritation if exposures to high enough levels occur. Any remaining mustard agent is not likely to migrate through the groundwater to offsite since it is not mobile in water, including groundwater.

  • Public concern over the illnesses, especially cancer, in the vicinity of DDMT.

The health of the community is an important concern to ATSDR, DDMT, EPA, and State and local agencies. A primary purpose of the PHA process is to address concerns of neighbors of NPL sites.

There is no evidence that significant amounts of the contaminants from DDMT have been in places where people could come in contact with them. There is no evidence of any significant exposures to DDMT-related contaminants occurring today. And, if similar conditions (similar contaminants at similar concentrations in the environment) occurred in the past, it is not likely that serious exposures occurred in the past. For these reasons it is not likely that adverse public affects have occurred.

  • Concern has been expressed that waste disposal records for DDMT are incomplete, and that materials may have been disposed at Dunn Field without records being kept.

DDMT environmental officials have provided the inventory of waste disposals which were recorded to have occurred at Dunn Field during the history of DDMT. These records are presented as being complete and comprehensive. ATSDR evaluations regarding possible exposures are necessarily based on actual, available information. ATSDR is requesting that DDMT undertake all possible efforts to locate existing records of onsite waste disposals. If RI data collection finds evidence of further contamination, ATSDR will provide an evaluation of public health impact. ATSDR will also suggest that the chemical agent disposals be appended to the DDMT waste disposal list.

  • Concern has been expressed that contaminated groundwater from under Dunn Field could be leaching onto the surface and affecting the surface water to the west of Dunn Field.

Rainwater that soaks into the ground will percolate almost straight downward until it reaches the watertable. In the area of Dunn Field the watertable is about 40 feet below the ground surface. Even though Dunn Field is at a higher elevation than the surrounding community, it is very unlikely that contaminated groundwater could move laterally above the watertable for any distance (of more than a few feet). For this reason it is very unlikely that any contaminated groundwater is leaching out onto the surface at the lower elevations.

It is also very unlikely that the drainage ditches are being recharged by contaminated groundwater, as they would only be receiving groundwater from the immediate area of their streambanks (no more than 10 to 20 feet away at the most). For buried contaminants to reach the ditches, the source of contamination would have to be within this area immediately adjacent to the ditches.

  • The request was made to include, in this PHA, a map showing the location of areas within DDMT that contained soil contamination. The concern was that these ares should be known to the public as DDMT is closed and released to other ownership.

The remedial process overseen by EPA and TDEC will ensure that no contaminants remain that would pose a threat to human health or the environment. The present status and location of soil contamination would not be as important to future owners as would be information on the final status of these areas. ATSDR will coordinate with EPA, State and local agencies, and DDMT to ensure that no potential exposures remain that could result in a threat to public health.

  • In a review of the public comment draft of this document, a community member raised several questions about the possibility of exposures at DDMT. These questions are related to four general concerns, which have been grouped as follows:
      - proximity of neighborhoods, schools and recreational areas to DDMT;

Merely being located in the area of DDMT is not a public health problem if there are no completed pathways for contamination. As stated in sections above, there is no evidence that environmental exposures have occurred through contamination of offsite air, soil or water. Specifically, current data from offsite does not support a concern that contamination is present that would be in the ditches outside the DDMT fences. Additional data are being collected by DDMT from drainage ditches offsite. These data should provide definite information on the absence or presence of significant amounts of chemicals from DDMT that might have reached offsite.

      - the possibility of contamination of surface water bodies in the general vicinity of DDMT;

As stated in sections above, it is not likely that chemicals buried in Dunn Field could have been transported by any reasonably expected natural process into the surface drainage ditches in the Dunn Field area. Samples collected from drainage ditches in other areas of DDMT do not show chemical contamination of a type or amount that would present a public health threat from the type of contact (contact to the skin and infrequent ingestion of very small amounts) that would occur in these ditches. Again, new samples being collected will address this issue and should provide a final answer.

      - the effects of eating fruit or vegetable grown in a one-mile radius of DDMT; and

There is no evidence that chemicals from DDMT have "migrated" offsite through air or water contamination in types or amounts that would cause a public health problem from being present in vegetable or fruit grown in the DDMT vicinity. There do not appear to be completed environmental pathways (air, soil, or water) through which chemicals from DDMT could have gotten into fruit or vegetables grown in the DDMT area.

      - various illnesses and ailments of people living and working in the DDMT vicinity.

As stated above, there is no evidence that significant amounts of the contaminants from DDMT have been in places where people could come in contact with them. There is no evidence of any significant exposures to DDMT-related contaminants occurring today. And, if similar conditions (similar contaminants at similar concentrations in the environment) occurred in the past, it is not likely that serious exposures occurred in the past. For these reasons it is not likely that adverse public affects have occurred.

  • What are current activities that will provide additional information on public health issues in the DDMT area.

New information is being collected by DDMT for the state and EPA as a part of the Remedial Investigation. This information will be evaluated by ATSDR. If this information provides evidence that exposures are occurring, actions will be recommended to protect public health.

The State of Tennessee is conducting an investigation that may provide information on the general nature of cancers occurring in the community. The results of this study will be available for review in the near future.

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