PRELIMINARY PUBLIC HEALTH ASSESSMENT
PLYMOUTH AVENUE LANDFILL
DELAND, VOLUSIA COUNTY, FLORIDA
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
In this section, we review the environmental data collected at this landfill. Specifically, we evaluate the adequacy of the environmental data, select contaminants of concern, and list their maximum concentration and frequency of detection. We then compare the maximum concentrations found to background levels and to standard comparison values. In the data tables, we use the following comparison values:
1. EMEGs--Environmental Media Evaluation Guides--are derived from the ATSDR's Minimal Risk Levels (MRLs) and provide a measure of the toxicity of a chemical. They are the ATSDR's estimate of daily human exposure to a chemical that is likely to be without an appreciable risk of adverse effects. EMEGs are usually based on exposure for a year or longer.
2. LTHAs--Lifetime Health Advisories for Drinking Water--are the EPA's estimate of drinking water contaminant concentrations at which adverse health effects are unlikely over lifetime exposure. LTHAs provide a safety margin to protect sensitive members of the population.
3. MCLs--Maximum Contaminant Levels--are contaminant concentrations that the EPA considers protective of public health. They assume ingestion of 2 liters of water per day for 70-years. MCLs are regulatory concentrations.
4. RMEGs--Media Evaluation Guides--are derived from the EPA's reference dose. RMEGs are an estimate of daily human exposure to a chemical that is likely to be without an appreciable risk of adverse effects. They are usually based on exposure for a year or longer. RMEGS are similar to the EMEGs above.
5. SMCLs--Secondary Maximum Contaminant Levels--are the EPA's estimate of the concentration above which water is not aesthetically acceptable (primarily due to taste and/or odor). SMCLs are regulatory concentrations in Florida.
We reviewed the environmental sampling data collected at this landfill and selected the following chemicals as contaminants of concern:
| barium | iron |
| chromium (total) | nitrate |
| 1,2-dichloroethene | sulfate |
| (cis & trans isomers) | vinyl chloride |
We selected these contaminants based on the following factors:
Identification of a contaminant of concern in this section does not necessarily mean that exposure will cause adverse health effects. Identification serves to narrow the focus of this health assessment to those contaminants most important to public health. When selected as a contaminant of concern in one medium, we also reported the concentration of that contaminant in all other media. We evaluate these contaminants in subsequent sections and decide whether exposure has public health significance.
To identify industrial facilities that could contribute to the contamination near this landfill, we searched the EPA Toxic Chemical Release Inventory (TRI) data base. The EPA developed TRI from the chemical release information (air, water, and soil) provided by certain industries. The TRI data base covers releases between 1987 and 1991. We found one industrial facility in the 32720 ZIP code that includes the Plymouth Avenue Landfill. Ardmore Farms estimates it released 20,000 pounds of ammonia into the air between 1987 and 1991. Ardmore Farms is an orange juice processing facility at 1915 N. Woodland Boulevard, about 2.5 miles northeast of the landfill. Because of the distance, we do not expect that ammonia from this facility has affected the health of people living near the landfill.
In this assessment, we discuss the contamination that exists on the landfill first, separately from the contamination that occurs off the landfill.
The Environmental Protection Agency has proposed adding the three (3) sludge cells on the eastern edge of the landfill to the National Priorities List of Superfund hazardous waste sites. In this assessment we consider the entire 131-acre landfill. We define "on-site" as the landfill property boundary as shown in Figure 2 (Appendix A). We compiled data in this subsection from the files of the Volusia County DSWM (VCDSWM 1994) and Florida Department of Environmental Protection (DEP 1994). We also compiled data in this subsection from reports by Briley, Wild and Associates (BWA 1981, 1992) and the NUS Corporation (NUS 1990).
On-Site Waste Material
From June 1978 to October 1980, the landfill reportedly received 4,500 gallons per week of nitric acid process waste slurry (pH 0-1) from the nearby Brunswick Corporation. This waste contained up to 90,000 milligrams per liter (mg/L) of nitrate. The Volusia County DSWM spread the waste over an undisturbed area in the southeast corner of the landfill or deposited it into shallow trenches also in the southeast corner of the landfill (BWA 1992). Table 1, below, summarizes the contaminants-of-concern maximum concentrations in this waste.
Table 1. Maximum Concentrations in 1978 Nitric Acid Waste
|
Contaminants of Concern |
Maximum Concen- tration (mg/kg) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/kg) |
Comparison Value | |
| (mg/kg) | Source | ||||
| Barium | NA | --- | --- | None | --- |
| Chromium (total) |
1 | 1/1 | --- | None | --- |
| c+t-1,2-Di- chloroethene |
NA | --- | --- | None | ___ |
| Iron | 17,500 | 1/1 | --- | None | --- |
| Nitrate | 20,500 | 1/1 | --- | None | --- |
| Sulfate | NA | --- | --- | None | --- |
| Vinyl Chloride | NA | --- | --- | None | --- |
NA - not analyzed mg/kg - milligrams per kilogram
EMEG - Environmental Media Evaluation Guide based on the ATSDR minimal risk level.
RMEG - Media Evaluation Guide based on EPA reference dose.
Source: Russell 1978
On-Site Surface Soil
There have been no surface soil samples (0-3 inches deep). We do not recommend the Volusia County DSWM collect any on-site surface soil samples since it is unlikely that cover soil is contaminated. In 1990, the NUS Corporation, under contract with the EPA, did collect one background surface soil sample (0-6 inches deep) from the northwest corner of the site (Figure 3, Appendix A). They found 0.034 milligrams per kilogram (mg/kg) of toluene, a component of gasoline. Toluene in this surface soil sample is likely due to runoff from nearby Grand Avenue. They did not find any significant concentrations of metals, other organic chemicals, or pesticides in this background sample (NUS 1990). Table 2, below, summarizes the contaminants-of-concern maximum concentrations in the on-site surface soil (0-3 inches deep).
Table 2. Maximum Concentrations in On-Site Surface Soil (0-3 inches deep)
|
Contaminants of Concern |
Maximum Concen- tration (mg/kg) |
Total # positive-------- Total # samples |
Back- ground* Concen- tration (mg/kg) |
Comparison Value | |
| (mg/kg) | Source | ||||
| Barium | NA | --- | <10 | 50,000 | RMEG |
| Chromium (total) |
NA | --- | 3.3 | 4,000 | RMEG |
| c+t-1,2-Di- chloroethene |
NA | --- | <0.005 | 10,000 | RMEG |
| Iron | NA | --- | 690 | None | None |
| Nitrate | NA | --- | 2.1 | 106 | RMEG |
| Sulfate | NA | --- | NA | --- | --- |
| Vinyl Chloride | NA | --- | <0.011 | 10 | EMEG |
* - EPA background surface soil sample 0-6 inches deep
NA - not analyzed mg/kg - milligrams per kilogram
EMEG - Environmental Media Evaluation Guide based on the ATSDR minimal risk level.
RMEG - Media Evaluation Guide based on EPA reference dose.
Source: NUS 1990
On-Site Subsurface Soil (1-75 feet deep)
In 1989, NUS collected three subsurface soil samples (four to 5 feet deep) in and around the disposal cells on the east side of the site (Figure 3, Appendix A). They analyzed these samples for metals, volatile organic chemicals, nonvolatile organic chemicals, pesticides, nitrate, and cyanide. They found elevated concentrations of chromium, iron, and nitrate in the samples from the disposal cells (NUS 1990). We consider sample PL-SB-01 as representative of background subsurface soil quality.
In 1991, Briley, Wild and Associates, consultants for the Volusia County DSWM, collected 212 subsurface soil samples. They collected these samples (1 to 75 feet deep) from 22 spots near the disposal cells (Figure 4, Appendix A). They analyzed these samples for nitrate and sulfate and found elevated concentrations around the southern most disposal cell (BWA 1992).
Table 3, below, summarizes the contaminants-of-concern maximum concentrations in on-site subsurface soils (1 to 75 feet deep). For this public health assessment, these samples are adequate to characterize the subsurface soil quality. This is especially true for nitrate on the east side of the landfill.
Table 3. Maximum Concentrations in On-Site Subsurface Soil (1 to 75 feet deep)
| Contaminants of Concern |
Maximum Concen- tration (mg/kg) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/kg) |
Comparison Value | |
| (mg/kg) | Source | ||||
| Barium | <40 | 0/3 | <5 | 50,000 | RMEG |
| Chromium (total) |
58 | 0/3 | <1 | 4,000 | RMEG |
| c+t-1,2-Di- chloroethene |
<0.006 | 0/3 | <0.005 | 10,000 | RMEG |
| Iron | 5,900 | 3/3 | 510 | None | --- |
| Nitrate | 180 | 83/215 | 4.2 | 106 | RMEG |
| Sulfate | 19,200 | 7/7 | NA | None | --- |
| Vinyl Chloride | <0.012 | 0/3 | <0.011 | 10 | EMEG |
On-Site Surface Water
In 1987 and 1988, the Volusia County DSWM sampled and analyzed water from the large depression in the center of the landfill. They and found elevated concentrations of iron (maximum 13.9 mg/L). There is no other water body on or near the site with which to compare surface water concentrations. For this public health assessment, two samples are adequate to characterize the on-site surface water quality. Table 4, below, summarizes the contaminants-of-concern maximum concentrations in on-site surface water.
Table 4. Maximum Concentration in On-Site Surface Water
| Contaminants of Concern |
Maximum Concen- tration (mg/L) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/L) |
Comparison Value | |
| (mg/L) | Source | ||||
| Barium | NA | --- | NA | 0.7 | RMEG |
| Chromium (total) |
0.01 | 1/1 | NA | 0.1 | LTHA |
| c+t-1,2-Di- chloroethene |
<0.001 | 0/1 | NA | 0.1 | LTHA |
| Iron | 13.9 | 1/1 | NA | 0.03 | SMCL |
| Nitrate | <0.5 | 0/1 | NA | 10 | MCL |
| Sulfate | NA | --- | NA | 400 | MCL |
| Vinyl Chloride | <0.001 | 0/1 | NA | 0.0002 | EMEG |
On-Site Sediments
In 1989, NUS collected one sediment grab sample from the large depression in the center of the landfill (Figure 3, Appendix A). They analyzed this sample for metals, volatile organic chemicals, nonvolatile organic chemicals, pesticides, nitrate, and cyanide. They found elevated concentrations of barium, chromium, iron, and nitrate (NUS 1990). There is no other water body on or near the site with which to compare sediment concentrations. For this public health assessment, one sample is adequate to characterize the on-site sediment quality. Table 5, below, summarizes the contaminants-of-concern maximum concentrations in on-site sediments.
Table 5. Maximum Concentration in On-Site Sediments
| Contaminants of Concern |
Maximum Concen- tration (mg/kg) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/kg) |
Comparison Value | |
| (mg/kg) | Source | ||||
| Barium | 330 | 1/1 | NA | 50,000 | RMEG |
| Chromium (total) |
71 | 1/1 | NA | 4,000 | RMEG |
| c+t-1,2-Di- chloroethene |
<0.011 | 0/1 | NA | 10,000 | RMEG |
| Iron | 13,000 | 0/1 | NA | None | --- |
| Nitrate | 6.7 | 1/1 | NA | 106 | RMEG |
| Sulfate | NA | --- | NA | --- | --- |
| Vinyl Chloride | <0.021 | 0/1 | NA | 10 | EMEG |
On-Site Ground Water
For this assessment we have combined ground-water quality data from the surficial and Floridan aquifers. Three hydrogeological studies have documented a connection between the two aquifers at this site (USGS 1977, BWA 1981, BWA 1992).
The Volusia County DSWM has monitored ground-water quality at this landfill since 1981. In 1983, they noticed the concentrations of nitrate in monitor wells M05 and M11 along the east landfill (Figure 5, Appendix A) boundary began to rise. The concentration of nitrate in monitor well M11 peaked at 963 mg/L in March 1984. By 1992, the nitrate concentration in these wells had fallen to between 40 and 80 mg/L (VCDSWM).
The Volusia County DSWM also found that the concentration of barium in monitor wells M05 and M11 occasionally exceeded the drinking-water standard of 2 mg/L (VCDSWM 1994).
In 1990, the NUS Corporation sampled eight existing on-site monitor wells for the EPA (Figure 3, Appendix A). They found approximately 100 mg/L of nitrate in two wells along the east landfill boundary: PL-MW-02 and PL-MW-03 (NUS 1990). Previous reports referred to monitor wells PL-MW-02 and PL-MW-03 as "M05" and "M11."
From 1989 to 1991, Briley, Wild and Associates conducted a contamination assessment for the Volusia County DSWM. This assessment focused on the extent of nitrate ground-water contamination along the eastern landfill boundary. They found nitrate contamination in the ground water under the eastern part of the site and for a short distance off site. They found the surficial and the upper 30 feet of the Floridan aquifers were contaminated with nitrate at concentrations as high as 170 mg/L (BWA 1992).
We consider monitor well M14 (also called PL-MW-01) representative of background ground-water quality. For this public health assessment, the existing data adequately characterize the on-site ground-water quality. Table 6, below, summarizes the contaminants-of-concern maximum concentrations in the on-site monitor wells.
Table 6. Maximum Concentration in On-Site Monitor Wells
| Contaminants of Concern |
Maximum Concen- tration (mg/L) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/L) |
Comparison Value | |
| (mg/L) | Source | ||||
| Barium | 2.9 | 54/72 | <0.07 | 0.7 | RMEG |
| Chromium (total) |
0.09 | 28/101 | <0.005 | 0.1 | LTHA |
| c+t-1,2-Di- chloroethene |
<0.005 | 0/7 | <0.005 | 0.1 | LTHA |
| Iron | 18.5 | 42/51 | 1 | 0.3 | SMCL |
| Nitrate | 963 | 95/107 | 0.1 | 10 | MCL |
| Sulfate | 150 | 34/36 | NA | 400 | MCL |
| Vinyl Chloride | <0.01 | 0/7 | <0.01 | 0.0002 | EMEG |
For the purposes of this evaluation, we define "off-site" as the area outside the landfill property boundary as shown in Figure 2 (Appendix A). We compiled data in this subsection from the files of the Volusia County DSWM (VCDSWM 1994) and Volusia CPHU (VCPHU 1994). We also compiled data in this subsection from reports by Briley, Wild and Associates (BWA 1992) and the NUS Corporation (NUS 1990).
Off-Site Surface Soil (0-6 inches deep)
In 1990, the NUS Corporation, under contract with the EPA, collected two surface soil samples (0-6 inches deep) 200-300 feet east of the landfill (Figure 3, Appendix A). They did not find any significant concentrations of metals, solvents, organic chemicals, or pesticides (NUS 1990). Since there is little stormwater run-off from the site, we do not recommend any additional off-site surface soil sampling. Table 7, below, summarizes the maximum concentrations of contaminants of concern in off-site surface soil (0-6 inches deep) in 1990.
Table 7. Maximum Concentrations in Off-Site Surface Soil (0-6 inches deep)
| Contaminants of Concern |
Maximum Concen- tration (mg/kg) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/kg) |
Comparison Value | |
| (mg/kg) | Source | ||||
| Barium | <9 | 0/2 | NA | 50,000 | RMEG |
| Chromium (total) |
<3 | 0/2 | NA | 4,000 | RMEG |
| c+t-1,2-Di- chloroethene |
<0.005 | 0/2 | NA | 10,000 | RMEG |
| Iron | 540 | 2/2 | NA | None | None |
| Nitrate | 2.4 | 2/2 | NA | 106 | RMEG |
| Sulfate | NA | --- | NA | --- | --- |
| Vinyl Chloride | <0.011 | 0/2 | NA | 10 | EMEG |
Off-Site Subsurface Soil (1-75 feet deep)
In 1989, the EPA collected two subsurface soil samples (four to 5 feet deep) 200-300 feet east of the landfill (Figure 3, Appendix A). They analyzed these samples for metals, volatile organic chemicals, nonvolatile organic chemicals, pesticides, nitrate, and cyanide but did not find any elevated concentrations (NUS 1990).
In 1991, Briley, Wild and Associates collected 88 subsurface soil samples (1 to 75 feet deep) from 13 locations east of the landfill (Figure 4, Appendix A). They analyzed these samples for nitrate and found elevated concentrations (maximum 11 mg/kg) in two samples (BWA 1992).
For this public health assessment, these samples are adequate to characterize the off-site subsurface soil quality. We consider sample PL-SB-01 (Figure 3, Appendix A) as representative of background subsurface soil quality. Table 8, below, summarizes the contaminants-of-concern maximum concentrations for off-site subsurface soil (1-75 feet deep).
Table 8. Maximum Concentrations in Off-Site Subsurface Soil (1-75 feet deep)
| Contaminants of Concern |
Maximum Concen- tration (mg/kg) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/kg) |
Comparison Value | |
| (mg/kg) | Source | ||||
| Barium | <3 | 0/2 | <5 | 50,000 | RMEG |
| Chromium (total) |
<2 | 0/2 | <1 | 4,000 | RMEG |
| c+t-1,2-Di- chloroethene |
<0.005 | 0/2 | <0.005 | 10,000 | RMEG |
| Iron | 250 | 2/2 | 510 | None | --- |
| Nitrate | 11 | 9/90 | 4.2 | 106 | RMEG |
| Sulfate | NA | --- | NA | --- | --- |
| Vinyl Chloride | <0.01 | 0/2 | <0.011 | 10 | EMEG |
Off-site Ground Water
In this section, we discuss the ground-water quality in the nearby private drinking-water wells and the ground-water quality in off-site monitor wells. The Volusia County DSWM and the Volusia CPHU sampled most of the nearby private drinking-water wells between 1987 and 1989 (Table 9). Between 1989 and 1992, the Volusia County DSWM installed and sampled the off-site monitor wells (Table 10). We used on-site monitor well M14 (also called PL-MW-01) as representative of background ground-water quality.
The predominate ground-water contaminant associated with this landfill is nitrate. Since 1987, the Volusia County DSWM, the Volusia CPHU, and the NUS Corporation together have sampled about 40 nearby private drinking-water wells. This includes about 20 private drinking-water wells within 0.25 mile of the landfill (Figure 6, Appendix A). They found elevated nitrate concentrations (>0.5 mg/L) in about half these wells (VCDSWM 1994, VCPHU 1994, NUS 1990). Monthly between 1987 and 1989, the Volusia County DSWM resampled six of these wells east and south of the landfill and found nitrate concentrations greater than 5 mg/L. Two had nitrate concentrations between 10 and 15 mg/L; a third had concentrations as high as 20 mg/L. Table 9, below, summarizes the contaminants-of-concern maximum concentrations for off-site private drinking-water wells.
Although over 40 nearby private drinking-water wells have been sampled, we do not know the past extent of the nitrate contamination. It is likely that before 1987, ground water nitrate concentrations were higher and contamination was more widespread. Most of the approximately 20 nearby private drinking-water wells that had less than 5 mg/L nitrate in 1987 have not been resampled. Due to the karst (cavernous) geology of the area, ground water concentrations can change rapidly. The lack of follow-up analysis for nitrate in these wells is a significant data gap. We recommend the Volusia County Department of Solid Waste Management resample these nearby private drinking-water wells and analyze for nitrate.
In 1989, the Volusia CPHU sampled and analyzed ten nearby private drinking-water wells as part of the underground petroleum storage tank program. They found low levels of 1,2-dichloroethene and vinyl chloride in the Volusia County Humane Society private drinking-water well (VCPHU 1994). Ground water sampling was inadequate, however, to determine the full area of contamination. We recommend the Volusia County Department of Solid Waste Management sample all of the nearby private drinking-water wells and analyze for vinyl chloride.
Table 9. Maximum Concentration in Off-Site Private Drinking-Water Wells
| Contaminants of Concern |
Maximum Concen- tration (mg/L) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/L) |
Comparison Value | |
| (mg/L) | Source | ||||
| Barium | <0.1 | 0/22 | <0.07 | 0.7 | RMEG |
| Chromium (total) |
<0.005 | 0/10 | <0.005 | 0.1 | LTHA |
| c+t-1,2-Di- chloroethene |
0.006 | 3/10 | <0.005 | 0.1 | LTHA |
| Iron | 0.74 | 4/10 | 1 | None | --- |
| Nitrate | 20 | 118/147 | 0.1 | 10 | MCL |
| Sulfate | 7.3 | 1/1 | NA | 400 | MCL |
| Vinyl Chloride | 0.002 | 3/10 | <0.01 | 0.0002 | EMEG |
Between 1989 and 1991, Briley, Wild and Associates installed and sampled five monitor wells east of the landfill (Figure 4, Appendix A). For these monitor wells, we have combined ground-water quality data from the surficial and Floridan aquifers. Hydrogeological studies have shown a connection between these two aquifers at this landfill (USGS 1977, BWA 1981, BWA 1992). They found elevated concentrations of nitrate, iron, and sulfate. Figure 7 (Appendix A) shows the current (1992) extent of ground water with more than 10 mg/L of nitrate. Ground water with more than 10 mg/L of nitrate extends about 200 feet east of the southeast side of the landfill (BWA 1992). We do not know how far ground water with more than 0.5 mg/L nitrate currently extends. Table 10, below, summarizes the contaminants-of-concern maximum concentrations for off-site monitor wells.
Only four off-site monitor wells and one private drinking-water well were tested for sulfate. Five samples are inadequate to characterize levels of sulfate in the off-site ground water. Sulfate concentrations in these five wells, however, were below state drinking water standards. Since the landfill stopped accepting the Brunswick Corporation sulfuric acid waste in 1980, it is likely sulfate concentrations will continue to decline. Therefore, we do not recommend additional sampling for sulfate.
Table 10. Maximum Concentration in Off-Site Monitor Wells
| Contaminants of Concern |
Maximum Concen- tration (mg/L) |
Total # positive-------- Total # samples |
Back- ground Concen- tration (mg/L) |
Comparison Value | |
| (mg/L) | Source | ||||
| Barium | 0.3 | 6/23 | <0.07 | 0.7 | RMEG |
| Chromium (total) |
0.02 | 3/23 | <0.005 | 0.1 | LTHA |
| c+t-1,2-Di- chloroethene |
NA | --- | <0.005 | 0.1 | LTHA |
| Iron | 6.4 | 7/23 | 1 | 0.3 | SMCL |
| Nitrate | 1.3 | 4/23 | 0.1 | 10 | MCL |
| Sulfate | 48 | 4/4 | NA | 400 | MCL |
| Vinyl Chloride | NA | --- | <0.01 | 0.0002 | EMEG |
C. Quality Assurance and Quality Control
In preparing this public health assessment, we relied on the environmental data provided by the Volusia County DSWM, the Volusia CPHU, the Florida DEP and the EPA. We assume these agencies followed adequate quality assurance and quality control measures concerning chain-of-custody, laboratory procedures, and data reporting. The completeness and reliability of the referenced information determine the validity of the analysis and conclusions drawn for this public health assessment. We assume the data we reviewed for this assessment are valid since the environmental samples were collected and analyzed by governmental agencies or their contractors.
In each of the preceding On- and Off-Site Contamination subsections, we evaluated the adequacy of the data to estimate exposures. We assumed that estimated data (J) and presumptive data (N) were valid. This second assumption errs on the side of public health by assuming that a contaminant exists when actually it may not exist.
The Volusia County DSWM has monitored the soil gases at the landfill borders but has not detected significant quantities of methane or other gases. Since the cover soil at this landfill is porous sand, accumulation of dangerous concentrations of gases is unlikely. The Volusia County DSWM is currently expanding its soil gas monitoring program (HRS 1994).
If the landfill were not secured, the water-filled depression in the center could be a drowning
hazard for young children. The landfill is, however, surrounded by an 8-foot chain-link fence and
supervised during the day. We did not see any other potential physical hazards during our visit.
In this section, we evaluated the environmental and human components of exposure pathways. Exposure pathways consist of five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population.
We eliminate exposure pathways if at least one of the five elements is missing and will never be present. We categorize exposure pathways that we can not eliminate as either completed or potential. For completed pathways, all five elements exist and exposure to a contaminant has occurred, is occurring, or will occur. At least one of the five elements is missing, but could exist in potential pathways. For potential pathways, exposure to a contaminant could have occurred, could be occurring, or could occur in the future.
A. Completed Exposure Pathways
Ground Water Pathway
The hydrogeology underlying this landfill is complex. The uppermost 70 to 80 feet is mostly sand. This sand contains the unconfined surficial aquifer. Compared to the rest of the county, the unsaturated zone under this landfill is unusually thick. Depth to the top of the surficial aquifer is between 15 and 45 feet below the land surface. Below the sands of the surficial aquifer are discontinuous layers of clay of the Hawthorne formation. Although these clays slow the downward movement of water, they readily allow for recharge of the underlying semiconfined Floridan aquifer; the surficial and Floridan aquifers under this landfill are hydraulically connected. Water travels from the land surface to the Floridan aquifer in as little as six years. Karst (cavernous) limestone of the Avon Park formation contains the Floridan aquifer (BWA 1992; NUS 1990).
Rainfall at this landfill seeps rapidly into the sand and percolates down to the top of the surficial aquifer. High porosity of these sands does not allow for significant surface water run-off. According to 1982 water level measurements, flow was to the southwest, south, and southeast. Measurements in 1986 showed flow was to the south and southeast (BWA 1988). Because of the complex topography and geology, the direction of ground-water flow in the surficial aquifer is largely undefined. The surficial aquifer serves as a source of recharge to the deeper Floridan aquifer.
Regionally, ground-water flow in the Floridan aquifer is west toward discharge to the St. Johns River and south toward discharge to Blue Springs. A 1977 U.S. Geological Survey investigation decided that ground-water flow in the Floridan aquifer under this landfill is to the east, south, and west (USGS 1977). A more recent investigation found flow in the Floridan aquifer under this landfill is predominantly to the southeast (BWA 1992).
Ingestion of contaminated ground water is a past completed exposure pathway (Table 10). Except for the Humane Society well, nitrate is the only contaminant to which we know people have been exposed. Analyses for sulfate have been inadequate. Solid or liquid waste disposed of at the landfill is a likely source of nitrate. Other possible sources of nitrate include: malfunctioning septic tanks, improper fertilizer disposal (ferneries), and improper animal waste disposal (commercial chicken farm). Although over 40 nearby private drinking-water wells have been sampled at one time or another, we do not know the past extent of the nitrate ground-water contamination. It is likely that in the past, ground-water nitrate concentrations were higher and contamination was more widespread. Between 1987 and 1989, elevated nitrate concentrations (<0.5 mg/L) were found in about 20 nearby private drinking-water wells. Although there are other possible sources of this nitrate contamination, we assume that at least some has migrated from the landfill. Ingestion is the route of exposure. Between 40 and 60 people may have been exposed in the past. More people may be exposed in the future if the appropriate agency does not clean-up the ground water.
B. Potential Exposure Pathways
Air Pathway
Inhalation of contaminated dust is a past potential exposure pathway (Table 11). Contaminated surface soil could have been the source. Air could have been the medium and nearby residents the points of exposure. Inhalation could have been the route of exposure. We categorize this exposure route as potential since there are insufficient data to confirm that either the surface soil or air was contaminated.
We eliminated incidental soil ingestion and surface water ingestion as exposure pathways. Although this landfill is open for use by the public during the day, it is fenced, access is monitored by Volusia County DSWM personnel, and there are no signs of trespass.
We eliminated inhalation of solvents released from ground water during showering and other domestic uses as an exposure pathway. This is not a significant exposure pathway at this site since the Humane Society Well was the only well with any solvents. The concentrations of solvents in the Humane Society well were low and the inhalation dose insignificant since this water was not used for showering.
Also, we eliminated inhalation of methane and other landfill gases as an exposure pathway. The Volusia County DSWM has monitored the soil gases at the landfill borders but has not detected significant quantities of methane or other gases. Since the cover soil at this landfill is porous sand, accumulation of dangerous gas concentrations is unlikely.
Table 10. Completed Exposure Pathways
| PATHWAY NAME |
EXPOSURE PATHWAY ELEMENTS | TIME | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
EXPOSED POPULATION |
||
| Ground Water |
Landfill | Ground Water | Drinking- Water Wells |
Ingestion | 40-60 Nearby Residents |
Past & Future |
| PATHWAY NAME |
EXPOSURE PATHWAY ELEMENTS | TIME | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
EXPOSED POPULATION |
||
| Contam- inated Dust |
Landfill Surface Soil |
Air | On and Off Site |
Inhalation | Unknown | Past |
In this section we discuss potential health effects on persons exposed to specific contaminants and address specific community health concerns.
Introduction
To evaluate health effects, the ATSDR developed a Minimal Risk Levels (MRLs) for contaminants commonly found at hazardous waste sites. An MRL is an estimate of daily human exposure to a contaminant below which non-cancer, adverse health effects are unlikely to occur. The ATSDR developed MRLs for each route of exposure, such as ingestion and inhalation, and for the length of exposure. The ATSDR categorizes length of exposure as acute (less than 14 days), intermediate (15 to 364 days), or chromic (greater than 365 days). The ATSDR presents these MRLs in Toxicological Profiles. These chemical-specific profiles provide information on health effects, environmental transport, human exposure, and regulatory status.
In this section, we use standard assumptions to estimate human exposure from ingestion of contaminated ground water. We assume the average adult ingests 2 liters of water per day and weighs 70 kilograms. Since there are no data for the concentrations of contaminants in on-site surface soil or air, we cannot evaluate the public health threat from these potential exposure pathways.
Barium
It is unlikely the concentrations of barium in the off-site ground water have caused illnesses. The various governmental agencies did not detect barium in any of the private drinking-water well samples. They detected barium in only 6 of the 23 off-site monitor well samples. The ATSDR has not established a Minimal Risk Level for barium. The estimated maximum dose from ingestion of the ground water in the monitor wells is less, however, than the lowest dose that did not cause an effect in laboratory animals (ATSDR 1992). Therefore, it is unlikely that barium in the ground water has caused any illnesses.
Chromium (total)
It is unlikely the concentrations of chromium (total) in the off-site ground water have caused illnesses. Since not all of the analyses for chromium differentiated between the different forms, we have considered the total of all of the forms. The various governmental agencies did not detect chromium in any of the private drinking-water well samples. They detected chromium in only 3 of the 23 off-site monitor well samples.
The ATSDR has not established a Minimal Risk Level for chromium. The estimated maximum dose from ingestion of ground water in the monitor wells is less, however, than the lowest dose that did not cause an effect in laboratory animals (ATSDR 1993a). Therefore, it is unlikely that chromium in the ground water has caused any illnesses.
cis and trans-1,2-Dichloroethene
It is unlikely the concentrations of 1,2-dichloroethene in the off-site ground water have caused illnesses. 1,2-Dichloroethene (total cis and trans isomers) was found in 3 out of 10 private drinking-water well samples. The estimated maximum dose from ingestion is less than both the acute and intermediate ATSDR MRLs. The ATSDR has not established a chronic MRL since scientists do not know the long-term human health effects of exposure to 1,2-dichloroethene. Scientists have not reported birth defects, reproductive effects, or cancer in humans or animals exposed to 1,2-dichloroethene (ATSDR 1990). The maximum concentration of 1,2-dichloroethene in these drinking-water wells was also less than the EPA Maximum Contaminant Level (MCL) for drinking water.
Iron
Concentrations of iron found in the ground water in both the drinking-water and off-site monitor wells are unlikely to cause illnesses. These concentrations, however, may give the water an astringent or metallic taste. In many places in Florida, natural ground water quality does not meet the secondary drinking water standard of 0.3 mg/L for iron. The EPA bases this secondary drinking water standard on iron's taste and staining threshold. There is no ATSDR toxicological profile for iron.
Nitrate
Maximum concentration of nitrate in the drinking-water wells could have caused methemoglobinemia in bottle fed infants less than six months old. These nitrate concentrations are unlikely, however, to cause any illnesses in infants older than six months, children, or adults. Methemoglobinemia is a condition where the blood is unable to transport oxygen to the tissues properly. We commonly refer to methemoglobinemia in infants as "blue baby syndrome."
When the Volusia CPHU found drinking-water wells with >10 mg/L nitrate, they advised the owner not to use this water to prepare infant formula. They also notified the Volusia CPHU medical director. Since there were no infants in these homes, we do not expect there were any cases of methemoglobinemia or "blue baby syndrome." There have been no reports of methemoglobinemia in this area.
Bacteria in the stomach, particularly of infants less than six months old, metabolize nitrate to nitrite. Nitrite reacts with hemoglobin, and markedly decreases the ability of blood to carry oxygen to the tissues. Bottle-fed infants less than six months old have a high stomach pH. Bacteria that reduce nitrate to nitrite may proliferate in the stomach at a high pH, leading to an increased formation of nitrite. Nitrite then reacts with the hemoglobin (the molecule in the blood that transports oxygen) to form methemoglobin. Methemoglobin is unable to transport oxygen resulting in methemoglobinemia (NAS 1977a).
The EPA bases its Maximum Contaminant Level (MCL) for nitrate in drinking water (10 mg/L) on epidemiological studies of infants with methemoglobinemia. There is little margin of safety in this value, however (NAS 1977a). There is no ATSDR toxicological profile for nitrate.
Sulfate
Because of the lack of sampling data, we cannot assess the public health threat of sulfate in the ground water. As noted above, the various governmental agencies only tested one drinking-water well for sulfate. One sample is inadequate to characterize levels of sulfate in the drinking-water wells. Sulfate concentrations four to five times higher than found in the off-site monitor wells could have a laxative effect (cause diarrhea) in sensitive individuals (NAS 1977b). There is no ATSDR toxicological profile for sulfate.
Vinyl Chloride
Concentrations of vinyl chloride found in the private drinking-water wells are unlikely to cause illnesses. Ground water sampling was inadequate, however, to determine the full area of contamination. The estimated maximum dose of vinyl chloride in one drinking-water well was slightly above the chronic oral ATSDR Minimal Risk Level (MRL). This MRL, however, includes a one thousand fold safety factor. The ATSDR bases this MRL on changes in liver cells of rats fed vinyl chloride in their diet daily for almost three years (ATSDR 1993b).
The Department of Health and Human Services has decided that vinyl chloride is a known carcinogen. Similarly, the International Agency for Research on Cancer and EPA have decided that vinyl chloride is carcinogenic to humans. Rats fed high levels of vinyl chloride daily for one to two years developed liver cancer (ATSDR 1993b). Concentrations in drinking-water wells near this landfill are so low, however, there is no apparent increased risk of cancer to humans.
B. Health Outcome Data Evaluation
We did not evaluate community health outcome data. Although the concentrations of nitrate in a few nearby private drinking-water wells exceeded the standard, it is unlikely a search of state-wide health outcome data would detect an effect in such a small group. Therefore, there is little justification or community demand for an evaluation of health outcome data at this time. If future environmental investigations find other contaminants or more widespread contamination, we will evaluate health outcome data as appropriate.
C. Community Health Concerns Evaluation
We have addressed each community health concern as follows:
1. In 1988, one nearby resident complained of digestive problems. This resident said that other nearby residents had (unspecified) health problems that lasted until they ceased drinking water from their wells.
"Digestive problems" cover a wide range of medical conditions. Without a medical diagnosis or a more specific description of the symptoms, it is difficult to assess this concern. Diarrhea could be considered a "digestive problem." Although the environmental data are insufficient to establish a link to this landfill, ingestion of high concentrations of sulfate is one possible cause of diarrhea. The Brunswick Corporation disposed of high sulfur content waste at the landfill. Only four off-site monitor wells and one private drinking-water well were tested for sulfate. Sulfate concentrations in these five wells, however, were below state drinking water standards. Since the landfill stopped accepting the high sulfur content Brunswick Corporation waste in 1980, it is likely sulfate concentrations will continue to decline. Therefore, we do not recommend additional sampling for sulfate.
Without further information, we cannot assess other (unspecified) health problems.
2. In 1994, one nearby resident complained that although their health has not been affected, their horses have failed to breed as expected.
In 1989, the Volusia CPHU sampled the well that both this resident and their horses use. They analyzed for gasoline related contaminants but did not find any. We suggest this resident contact a county agricultural extension agent to discuss the failure of their horses to breed. Also, we suggest this resident have their well analyzed for nitrates. The enlarged cecum and colon of horses provide a location for the microbial reduction of nitrate to nitrite (NAS 1977).
3. In 1994, one nearby resident complained that she and her husband experienced diarrhea for over six months when drinking the water from their well. She said that their physician was unable to diagnose the cause but their symptoms ceased when they switched to bottled water.
Although the environmental data are insufficient to establish a link to this landfill, ingestion of high concentrations of sulfate is one possible cause of diarrhea. The Brunswick Corporation disposed of high sulfur content waste at the landfill. Only four off-site monitor wells and one private drinking-water well were tested for sulfate. Sulfate concentrations in these five wells, however, were below state drinking water standards. Since the landfill stopped accepting the high sulfur content Brunswick Corporation waste in 1980, it is likely sulfate concentrations will continue to decline. Therefore, we do not recommend additional sampling for sulfate.
Another possible cause of diarrhea is giardia. Laboratories do not commonly analyze for this protozoan in drinking-water wells. It could have, however, traveled from the landfill to nearby drinking-water wells though the karst (cavernous) limestone. It could also have infiltrated from contaminated surface water to ground water along poorly constructed or deteriorated drinking-water wells. If nearby residents experience diarrhea again, we recommend the Volusia CPHU sample their wells and analyze for coliform bacteria and if funds are available, for giardia.
4. In 1994, one nearby resident mentioned that her husband had died of cancer (melanoma) and she had been treated successfully for breast cancer. She was unsure if the landfill caused her family's health problems.
Melanoma, a form of skin cancer, is associated with excessive sun exposure. The causes of breast cancer are less well known. None of the chemicals found at this landfill to date are associated with melanoma or breast cancer. Contaminated ground water from the landfill is not known to extend in the direction of this resident.
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