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PUBLIC HEALTH ASSESSMENT

SAND GRAVEL AND STONE SITE
ELKTON, MARYLAND


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

The tables in this section list the contaminants of concern in various media at the MSGS site. The listing of these contaminants does not necessarily indicate that a health threat exists. In this public health assessment, MDE and ATSDR evaluate these contaminants in subsequent sections and will indicate whether exposure to them has public health significance. Selection of these contaminants was based on the following factors:

  1. Concentrations of contaminants on and off the site.
  2. The quality of the data.
  3. Comparison of site-related concentrations with background concentrations, if available.
  4. Comparison of site-related concentrations with health-based comparison values.

The data tables that are included in this section of the report list the concentrations of the contaminants of concern in various environmental media. If available, health-based comparison values are listed for the contaminants. Comparison values are concentrations of chemicals in various media that a person could be exposed to for a long time period with the expectation that no adverse health effects would result. In some cases, comparison values are legal standards or guidelines that have been developed by regulatory agencies such as EPA.

Comparison values used for sediment samples are developed for soil exposures. No comparison values for sediment are available. Comparison values that are included in Tables 1, 2, and 4 have been developed for chemical contaminants in drinking water. These values are listed in Table 4 (surface water), even though this is not used as a source of water for local residents.

The data tables include the following acronyms for the listed comparison values:

CREG (Cancer Risk Evaluation Guide): This is the concentration of a contaminant that would be expected to result in an excess cancer risk of one-in-one million in an exposed individual.

EMEG (Environmental Media Evaluation Guide): The level of a chemical, identified by the ATSDR, that, below which, would not be expected to cause adverse health effects following long-term exposure.

MCL (Maximum Contaminant Level): Contaminant concentration in drinking water that EPA deems protective of public health (considering the availability and cost of water treatment technology) over a lifetime of exposure. MCLs are standards that must be met by public drinking water systems.

MCLG (Maximum Contaminant Level Goal): A drinking water concentration, identified by EPA, at which no adverse health effects would be expected to occur over a lifetime of exposure. This value allows for an adequate margin of safety and is not a legal standard.

PMCL (Proposed Maximum Contaminant Level): An MCL that has been proposed but not yet adopted as a legal standard.

PMCLG (Proposed Maximum Contaminant Level Goal): An MCLG that has been proposed, but not finally adopted.

RMEG (Reference Dose Media Evaluation Guide): An estimate developed for specific media, based on a reference dose established by EPA, that, below which, would be unlikely to cause adverse health effects other than cancer upon exposure.

A. ON-SITE CONTAMINATION

The data in this subsection were reported in the Phase I RI/FS and the Phase II RI/FS documentation (2,5). The Phase I site investigation focused on the EEA and was conducted during 1984/1985 by AEPCO, Inc., under a subcontract with NUS Corporation, a contractor with EPA. The Phase II investigation was conducted in 1987 by Dames and Moore, Inc., and focused on the WEA. The Phase II investigation also included sampling of some media from the EEA.

1. Air
Air monitoring was conducted in 1985 during on-site investigations of wastes, surface water, sediment, surface soil, and subsurface soil (drilling and well installation). Air monitoring was conducted of the breathing zone (a height of 5 ft.) and directly above samples or sources (within one-half inch of the material). The monitoring instrument measured the concentration of total airborne organic vapors, but could not identify the individual chemicals in the air. Organic vapors are given off by volatile organic chemicals that are exposed to the air.

Organic vapor concentrations in the breathing zones were at concentrations similar to background levels (0.1 to 0.4 parts per million (ppm)) that were measured upwind and at a reasonable distance from suspected sources (2). The highest vapor readings recorded over contaminated media included levels of 50-100 ppm for the eastern portion of pond PO2, 10-15 ppm at the southern edge of pond PO1, and 15 ppm at a seep in the eastern wooded area. The limited air monitoring that has been conducted at the site does not allow for the assessment of potential public health hazards from exposure to airborne contaminants. A data gap exists with respect to the identification and measurement of specific contaminants in air.

A total of 144 radioactivity measurements were also made on the site during the Phase I investigations, and all were within the natural background levels (2).

2. Groundwater
Monitoring wells have been installed on the MSGS site in order to sample groundwater from a number of different groundwater units. A groundwater unit consists of permeable rock or soil and groundwater that it contains. A total of 4 different groundwater units have been identified at the site, 3 of which are found in the Potomac Group (unconsolidated sediments of sand, gravel, silt, and clay). The uppermost groundwater unit is confined to the EEA and is referred to as the upper sand unit. The groundwater in this unit is perched above a less permeable layer of silt and clay. Groundwater from this unit flows from seeps located west, southwest, and southeast of the EEA. Much of the water from these seeps reenters the ground and flows into another groundwater unit referred to as the middle sand unit. Groundwater in the middle sand unit generally flows to the south. A partially confined system below the middle sand unit is referred to as the lower sand unit. The deepest groundwater system underlying the site is the bedrock groundwater unit. Water in the two deepest groundwater units appears to flow towards the south or south-southwest. Most of the residential wells near the site appear to be screened in the lower sand unit or bedrock.

Although groundwater in the different units is partially separated by less permeable layers of silt and clay, water can move between the different units.

Phase I Investigation
The Phase I groundwater investigation was conducted in 1985 and focused on shallow groundwater in the EEA. Sampling for the Phase II investigation was conducted in 1987 and 1988. The Phase II investigation focused on shallow groundwater in the WEA and deeper groundwater units throughout the site. Figure 3 shows the location of shallow and deep monitoring wells that were established on the site during Phases I and II.

A total of 27 groundwater monitoring wells were installed as part of the Phase I investigation: 21 shallow wells in the upper sand unit (16 to 32 ft.), 4 wells in the lower sand unit (70 to 85 ft.), and 1 bedrock well (126 ft.) (2). All of the groundwater samples were analyzed for VOCs and metals, and a total of 8 samples (5 shallow wells and 3 deep wells) were analyzed for semivolatile compounds. Samples from shallow wells installed near the 3 ponds in the EEA showed the greatest contamination by VOCs (Table 1). VOCs that were identified and exceeded comparison values by a large margin included benzene, 2-butanone, chlorobenzene, chloroethane, 2-hexanone, toluene, 1,1,1-trichloroethane, and vinyl chloride. Eight VOCs were found in a well located near the buried drum area, with similar contaminants found in a well placed downgradient from pond PO3.

Semivolatile organic compounds were detected in 2 of the 5 shallow wells that were tested for these compounds. Semivolatile compounds that were identified in the highest concentrations included aniline, 1,4-dichlorobenzene, and 2-methylphenol. Metals that exceeded comparison values in shallow well samples included cadmium (1 well) and chromium (2 wells).

Low concentrations of a total of 8 different VOCs were identified in 4 of the 5 deep wells that were tested during Phase I. None of the VOCs exceeded applicable comparison values. Only 1 semivolatile organic compound, di(2-ethylhexyl)phthalate (DEHP), was identified in a monitoring well at a concentration above the comparison value. Metals were reported to be within the normal background range in samples from the 5 deep monitoring wells. No contaminants were detected in the 1 bedrock well sampled during the Phase I investigation.

Phase II Investigation
Sixteen new on-site monitoring wells were installed during the Phase II investigation (8 into bedrock and 8 into the middle or lower sand units). A total of 27 on-site wells were sampled during Phase II, including 7 shallow wells in the EEA that were sampled during the Phase I investigation. All Phase II water samples were analyzed for VOCs and metals. Water from wells in the WEA and 5 wells in the EEA were also analyzed for semivolatile compounds.

VOC contamination was found to be greatest in shallow wells in or near the EEA. An average of 10 different volatile contaminants were found in each of the wells in the EEA as opposed to other on-site wells which had an average of 3 VOCs per well (5). VOC concentrations were also highest in the shallow EEA wells. Cadmium was found in one well (SMW-02) at a concentration that exceeded the comparison value. The distribution of semivolatile contaminants was similar to that of VOCs; the greatest number and concentration of contaminants was found in shallow wells in the EEA. These results confirmed the findings of the Phase I sampling.

The number and concentrations of contaminants in the middle sand unit wells were generally considerably lower than in the upper sand unit wells in the EEA. The most and highest concentration of contaminants in groundwater from the middle sand unit was found in one monitoring well (DMW-07) that is east of pond P01. A total of 12 organic contaminants were found in this well in 1988, as compared to 5 organic contaminants in a Phase I sample from this well. Contaminants that were found in concentrations above comparison values include 1,1-dichloroethene, vinyl chloride, and trichloroethylene.

Four wells in the middle sand unit were sampled in the WEA and several organic compounds were found at low concentrations (below comparison values). Vinyl chloride in one of these wells was detected at a concentration above the comparison value (Table 2). The semivolatile compound DEHP was detected in 3 of these 4 wells. The highest estimated concentration was 10 parts per billion (ppb); the comparison value is 4 ppb. DEHP is found in many plastic materials and is a common environmental and laboratory contaminant. Some of the low concentrations of DEHP found in groundwater samples may be due to laboratory contamination (i.e., from water samples contacting plastic materials).

Four wells sampled groundwater in the lower sand unit. Low levels (below comparison values) of several organic chemicals were found in these wells. Toluene was the one contaminant found in all 4 of the wells. Concentrations of the metals chromium and lead exceeded comparison values in 1 well in the WEA (94 ppb chromium and 126 ppb lead in D&M 06) and of barium and lead in another well in the EEA (2,120 ppb barium and 221 ppb lead in D&M 09). The presence of these metals cannot be attributed to contamination because of structural problems related to both of the monitoring wells. One well (D&M 06) had structural problems that caused grout contamination of water and the other well was vandalized, and as a result, could not be properly sampled. Elevated levels of lead and cadmium were not found in new wells that were subsequently installed near wells D&M 06 and D&M 09. Also, concentrations of these metals were not elevated in other deep wells.

Low concentrations of VOCs were found in some of the 6 bedrock wells that were sampled in the WEA. The contaminant found in the highest concentration was toluene at 120 ppb. The detection of VOCs in these bedrock wells is significant in that it indicates that contaminants have migrated from their source in the EEA to the deepest aquifer in the WEA.

Organic contaminants that were the most widespread in groundwater included the common solvents methylene chloride, acetone, and toluene. Low concentrations of acetone and methylene chloride (1 to 16 ppb) were found in a number of laboratory blanks in both 1987 and 1988, suggesting that low concentrations in monitoring well samples may be due to laboratory contamination. Toluene was found in 20 of the 27 wells in which VOCs were detected during the Phase II investigation, including low concentrations in 2 wells (D&M 10 and D&M 11) that are upgradient (northern border of the EEA) of known sources of contamination. Toluene was not found in any of the off-site residential wells that were tested.

3. Sediments
The sediment sampling that was conducted during the Phase I investigation (October 1984) consisted of grab samples from a total of 29 sampling stations (24 on-site stations) (see Table 3). The highest levels of contaminants were found in sediments from the 3 ponds in the EEA. A sample from pond PO3 had the highest levels of the heavy metals cadmium, chromium, and lead. High concentrations of VOCs (especially xylenes, toluene, and chlorobenzene) were found in sediments sampled from the 3 ponds. VOCs were also found in sediments from several on-site streams and seeps.

The highest concentrations of semivolatile on-site contaminants were also found in the sediments sampled from the 3 former waste lagoons. A number of the highest contaminant concentrations were found in a sample taken from pond PO2. High level contaminants included DEHP, 1,4-dichlorobenzene, and 2-methylphenol. Table 3 lists contaminant concentrations in ppm detected in Phase I samples. The comparison values listed in this table were developed for children exposed to contaminants in soils and are included in the table, even though sediment exposure would be expected to be less frequent than soil.

As part of the Phase II RI/FS, 9 on-site sediment samples were collected (October/November 1987): 6 from surface water draining the WEA, and 3 from surface water draining the EEA. Four of the WEA sediment samples were from isolated ponds and 2 were from dry intermittent drainage ditches. Another of the sediment samples was from the swamp adjacent to Lower Haul Road, and 2 were taken from the western tributary of Mill Creek (receives runoff from both the EEA and WEA). The metal concentrations were within background levels and below comparison values. Low concentrations of acetone (10 - 43 ppb) and methylene chloride (15 - 47 ppb) were found in all 9 samples; however, these are suspected of being laboratory contaminants because of the low concentrations and the fact that they were found in blank samples. Two semivolatile compounds (4-methylphenol and DEHP) were found at low concentrations (less than 1 ppm) in 3 of the samples.

4. Soils
During the Phase I RI/FS in 1984, a total of 49 soil samples were collected from 23 sampling stations. At most stations, soils were sampled from 2 levels: 6 inches and approximately 3 feet below the surface. Soil samples were analyzed for metals and VOCs, but not for semivolatile organic compounds. Contaminant levels were reported as estimates and were low (below health-based comparison values). Because contaminant levels are estimates and are very low, they are not reproduced in a table, as are contaminants in other media. Only one of the sampling stations was in the Western Excavated Area (WEA).

Acetone and methylene chloride were found in samples taken near ponds PO1 and PO2. Acetone and toluene were found in soils in the swampy area just north of Lower Haul Road. The highest concentration estimates in soil samples taken in the EEA were 450 ppb for acetone and 140 ppb for methylene chloride. Trace amounts of other VOCs were also detected in these samples. The one sample taken in the WEA had estimated concentrations of 2,700 ppb acetone and 770 ppb of methylene chloride in a sample taken from a depth of 3 ft. The lowest health-based comparison values (based on exposure to a child) for these 2 chemicals are 200,000 ppb and 120,000 ppb for acetone and methylene chloride, respectively. At many of the sites sampled, contaminants were detected in both the shallow and deeper soil samples. Metal levels in the soils were within background levels and were lower than comparison values.

During the Phase II RI/FS, 38 shallow boreholes (about 8 feet deep) were drilled in the WEA and 15 in the EEA. Soil samples were collected for analysis from 3 different depths: 6-18 inches, 3-5 feet, and 5-8 feet. Chemical analyses for metals and VOCs were performed on a total of 114 soil samples from the WEA and 45 samples from the EEA. In addition, 23 soil samples were analyzed for semivolatile compounds. Also, a total of 400 surface soil samples were collected in the WEA and analyzed in the field with an organic vapor detector. An organic vapor detector can be used to detect the presence of organic vapors, but does not identify individual compounds. This served as a quick means for detecting any VOC contamination in surface soils.

No elevated organic vapor levels were detected in the field screening analysis of 400 WEA surface soil samples, except for a few samples in wooded areas in which the elevated readings were attributed to plant materials such as sassafras and pine tree roots (5). Acetone and methylene chloride were detected at low concentrations in many of the individual samples that were analyzed in the laboratory. These compounds were also detected in laboratory and field blanks and their presence in the samples probably indicates laboratory contamination. There was no evidence of contamination with metals or semivolatile organic compounds in any of the on-site soils, nor was there evidence of VOC contamination in the screening analysis of WEA surface soils.

During the Phase I investigation, soil samples were collected at a depth of 6 inches. Although this sampling strategy was considered adequate at the time, the results may or may not provide a good indication of the surface soil contaminants to which people may have been exposed. In assessing the potential human health hazard from soil exposure, it is important to test the top few inches of soil because this is what people are most likely to be exposed to. Surface soils (0-3 inches deep) in the WEA were characterized during the Phase II investigation for the presence of VOCs; however, the soils were not tested for metals or semivolatile compounds. The lack of surface soil (i.e., 0-3 inches) analysis represents a potential data gap for this site. For the WEA, where there is no history of waste disposal or visual evidence of surface contamination, it is unlikely that surface soil contamination would differ significantly from what was seen in subsurface soils (i.e., at 6" below the surface).

5. Surface Water
During the Phase I investigation, surface water grab samples were collected at 26 on-site stations. High levels of some metals (Table 4) were detected in samples collected from pond PO1. Some of the metal concentrations (including arsenic, cadmium, chromium, and lead) exceed comparison values by a large margin. Elevated metal concentrations were also detected in samples from the following areas: a seep that is downgradient from PO1, samples from pond PO2, samples from 2 streams in the Sedge Meadow area, and a sample from a creek downstream from the Old Sedimentation Pond. These concentrations all exceed health-based comparison values. Comparison values for contaminants listed in Table 4 were developed for drinking water sources. These values are included in the table even though on-site surface water is not used as a drinking water source.

Elevated concentrations (exceeding comparison values) of volatile organic compounds (VOCs) were found in the 3 ponds in the EEA, especially in pond PO1, in which the highest concentrations of 7 of the VOCs listed in Table 1 were found. Elevated VOC concentrations were also found in a seep downgradient from pond PO1. Semivolatile compounds were detected in the Sedge Meadow, downgradient from pond PO3.

A total of 7 surface water samples were collected during the Phase II investigation (October/November 1987). Four of the samples were from drainages in the WEA and 3 were from the Western tributary to Mill Creek, which receives runoff from the EEA. Low concentrations of methylene chloride (3 to 6 ppb) were found in all of the samples; however, this finding is probably due to laboratory contamination. Methylene chloride was found in laboratory blanks at levels of 1 to 5 ppb (8).

B. OFF-SITE CONTAMINATION

1. Air
No monitoring of airborne contaminants was performed off site. Based on local residents' past complaints of strong odors, it is clear that detectable concentrations of site contaminants have at times been present in off-site air (2). This conclusion is supported by past reports of site inspectors, indicating that they encountered strong on-site odors that resulted in eye, nose, and throat irritation (1). Based on the site history, levels of site contaminants in the air were likely most elevated during warm weather months in the mid-1970s. This is when there were open lagoons of liquid waste on the site.

2. Groundwater
A total of 12 off-site drinking water wells, serving residences and businesses, were sampled during the Phase I RI/FS. The sampled wells encircle the site (see Figure 4). Most of the wells were in the lower sand and bedrock groundwater units, with 2 wells in the middle sand unit. The iron content of the wells ranged up to 21,500 ppb, with manganese levels ranging up to 258 ppb. These levels are not considered to be indicative of contamination because the groundwater in the area is iron rich. A low concentration (7 ppb) of the solvent 1,1,1-trichloroethane was detected in a well located west of the site (RW-10; depth=65 ft.). During an earlier sampling episode, a low level (5.4 ppb) of the solvent tetrachloroethylene was detected in a sample from a residential bedrock well (RW-13; depth=250 ft.) north of the site. Tetrachloroethylene was also found in the laboratory blank and the well is north of the site, upgradient of the direction of groundwater flow, making it unlikely that the finding is indicative of contamination (2).

A total of 9 off-site wells were sampled in 1987 during the Phase II investigation, including 3 wells that were sampled during Phase I (not including RW-10 or RW-13). Most of the wells sampled in 1987 were located east and southeast of the site, adjacent to Route 40. Two of the sampled wells had relatively low concentrations of methylene chloride (11 and 23 ppb in wells OSW-01 and OSW-04, respectively); however, this is likely due to laboratory contamination (5). As noted previously, methylene chloride is a common laboratory contaminant and was found in blank samples. These wells are also a considerable distance from the site (Figure 4) and are not in the direction of groundwater flow (i.e., south), making it less likely that the finding of methylene chloride is site-related.

Information for 4 quarterly sampling events was provided in December 1993. The data from those sampling events indicate that contaminants are confined, primarily, to the upper sand unit. Chloroform and acetone were found in the middle sand unit. One sample of the lower bedrock water contained one VOC. Actual levels and all constituents found were not provided.

RW10 continues to contain low levels of VOCs. Levels were described as being in the low ppb range, but actual constituents and levels were not provided. (The resident is supplied bottled water).

3. Sediments
A total of 5 off-site sediment samples were collected during the Phase I investigation. All of the samples were analyzed for VOCs and metals, and 1 sample (at a station closest to the site) was analyzed for semivolatile compounds. In most cases, sediment and surface water samples were collected from the same sampling stations. Low concentrations of 7 VOCs were found in sediment collected from a station in Mill Creek, just outside of the site boundary. Methylene chloride and chlorobenzene were detected in sediment taken from Mill Creek, about 2 miles downstream from the site, and in another sample collected farther downstream (about 3.5 miles) in Elk Creek (2). None of the sediment contaminants exceed comparison values for soil. These samples were collected a considerable distance downstream from the site, making the origin of the contaminants uncertain. No sediment samples were collected from the 2 mile section of Mill Creek immediately downstream from the site. It is not clear why this section of the creek was not sampled since there would be a greater chance of finding contaminants in this section of the creek as opposed to areas farther downstream, that were sampled. Therefore, a data gap exists with respect to the characterization of contamination of sediments in this section of the creek. No samples of off-site sediments were collected during the Phase II investigation.

4. Soils
No off-site soils were sampled during either the Phase I or Phase II investigations. The Old Sediment Pond at the southeastern corner of the site (Figure 3) should work as a trap for most surface soils that migrate from areas of contamination during periods of heavy rainfall. If there is contamination in off-site soils it would most likely be found in the floodplain along Mill Creek. It is possible that contaminated soils and sediments would be carried from the site during periods of heavy rain and deposited along the creek (assuming that the creek occasionally overflows its banks). Although this lack of off-site soil data does represent a data gap, it is unlikely that high levels of contaminants would be found in off-site soils. Only low contaminant levels have been found in on-site sediments that have been sampled outside of the EEA and in the Mill Creek station just outside of the site boundary.

5. Surface Water
Biological assessments of Mill Creek were conducted by investigators from the State of Maryland, DNR, in 1974, 1975, and 1976. The investigators indicated that the creek was severely polluted up to at least 1 mile downstream from the site (1). A biological assessment of the creek was also conducted in 1988, in which identical methods were used to sample the same stations that were sampled during the earlier studies conducted in the 1970s (7). This survey indicated unpolluted conditions at the 2 off-site stations that were sampled.

A total of 8 off-site surface water stations were sampled during the Phase I RI/FS. Sampling stations included the following: 1 station in the eastern tributary of Mill Creek upstream of the site, 2 stations just below the confluence of the eastern and western tributaries of Mill Creek, 1 station in Mill Creek about 2 miles downstream from the site, and 3 stations in larger surface water bodies a considerable distance downstream from the site (1 in Little Elk Creek and 2 in Big Elk Creek). Samples were analyzed for metals and VOCs, but not for semivolatile compounds. It is unlikely that elevated levels of semivolatile compounds would have been found in these samples based on the fact that only very low levels of a few of these contaminants were found in on-site surface water samples taken from areas outside of the area of highest contamination. No VOCs were found in any of the off-site water samples, and metal levels were below applicable comparison values (2). No surface water was sampled from a section of Mill Creek extending about 2 miles downstream from the site boundary. No samples of off-site surface water were collected during the Phase II RI/FS.

Table 1.

SHALLOW GROUNDWATER CONTAMINANTS (1985) (2)
SUBSTANCE CONCENTRATION
RANGE
(ppb)
COMPARISON
VALUE
(ppb)

INORGANIC COMPOUNDS  
cadmium < 4.2 - 11 2 (EMEG)
chromium < 4.1 - 255 50 (RMEG)
     
VOLATILE ORGANIC COMPOUNDS  
acetone <10 - 68,650 1000 (RMEG)
benzene < 5 - 1,670 1.2 (CREG)
2-butanone < 10 - 65,900 170 (PMCLG)
chlorobenzene* < 5 - 14,200 200 (RMEG)
chloroethane < 10 - 5,360 NA
1,1-dichloroethane < 5 - 1,850 1000 (RMEG)
1,2-dichloroethane < 5 - 234 0.4 (CREG)
1,1-dichloroethylene < 5 - 552 0.06 (CREG)
ethylbenzene* < 5 - 846 700 (PMCLG)
2-hexanone* < 10 - 190,000 NA
methylene chloride* < 5 - 3,600 4.7 (CREG)
tetrachloroethylene* < 5 - 144 5 (MCL)
toluene* < 5 - 38,320 1000 (MCLG)
trans-1,2-dichloroethylene < 5 - 362 100 (MCLG)
1,1,1-trichloroethane < 5 - 13,850 200 (MCL)
trichloroethylene < 5 - 215 5 (MCL)
vinyl chloride < 10 - 1,070 0.02 (CREG)
xylenes* < 5 - 3,030 10,000 (PMCLG)
     
SEMIVOLATILE ORGANIC COMPOUNDS  
aniline ND - 260 6.3 (CREG)
1,4-dichlorobenzene ND - 240 75 (MCL)
2-methylphenol ND - 210 500 (RMEG)

*These contaminants were also identified in sampling that was conducted during the Phase II RI/FS (1987 and 1988)


TABLE 2.

DEEP GROUNDWATER CONTAMINANTS (1985-1988) (5)
SUBSTANCE UNIT CONCENTRATION
(ppb)
YEAR COMPARISON
VALUE (ppb)
AREA

VOLATILE ORGANIC COMPOUNDS      
           
Chloroform MSU <5 - 20 1985 5.7 (CREG) WEA
1,1-dichloroethene MSU <5 - 109 1988 0.06 (CREG) EEA
1,1,1-trichloroethane MSU <5 - 11.3 1985 200 (MCL) EEA
trichloroethylene MSU <5 - 13 1988 5 (MCL) EEA
toluene LSU <5 - 120 1988 1000 (MCLG) WEA
toluene BDRK <5 - 100 1987 1000 (MCLG) EEA /GSA
           
vinyl chloride* MSU <5 - 6 1988 0.02 (CREG) EEA /WEA
           
chlorobenzene LSU <5 - 16.4 1985 200 (RMEG) GSA
           
SEMIVOLATILE ORGANIC COMPOUNDS      
           
di(2-ethylhexyl)
phthalate (DEHP)
MSU <5 - 10 1987 4 (PMCL) EEA
  BDRK 59 1988 4 (PMCL) WEA
           
INORGANIC COMPOUNDS1        
           
barium LSU <2 - 2,120 1987 700 (RMEG) EEA
chromium LSU <2 - 94 1987 50 (RMEG) WEA
lead LSU <2 - 221 1987 5 (PMCL) EEA
lead LSU <2 - 126 1987 5 (PMCL) WEA

BDRK = bedrock sand unit; DWSA = drinking water standard/ advisory; EEA = eastern excavated area; GSA = general site area; LSU = lower sand unit; MSU = middle sand unit; WEA = western excavated area

*Reported concentrations are estimates.
1Elevated metal concentrations appeared in 2 wells and were likely caused by structural problems (see text).

TABLE 3. SEDIMENT CONTAMINANTS (1985) (2)

SUBSTANCE CONCENTRATION*
RANGE
(ppm)
COMPARISON1
VALUES
(ppm)

INORGANIC COMPOUNDS  
arsenic < 0.5 - 290 15 (RMEG)
cadmium 0.010 - 457 10 (EMEG)
chromium 2 - 2,470 250 (RMEG)
lead 1.8 - 5,020 NA
mercury 0.250 - 0.46 15 (RMEG)
     
VOLATILE ORGANIC COMPOUNDS  
chlorobenzene < 0.001 - 1,700 1000 (RMEG)
ethylbenzene < 0.001 - 550 5000 (RMEG)
methylene chloride < 0.004 - 32,000 93 (CREG)
tetrachloroethylene < 0.002 - 750 500 (RMEG)
toluene < 0.001 - 3,200 1000 (RMEG)
1,1,1-trichloroethane < 0.001 - 95 NA
trichloroethylene < 0.001 - 580 NA
xylenes < 0.002 - 2,100 100,000 (RMEG)
     
SEMIVOLATILE COMPOUNDS  
di(2-ethylhexyl)phthalate < 0.005 - 1,500 NA
1,4-dichlorobenzene < 0.001 - 61 NA
2-methylnaphthalene < 0.006 - 7.4 NA
2-methylphenol < 0.004 - 9.3 2500 (RMEG)
naphthalene < 0.005 - 11 NA
     
PESTICIDES    
endosulfan 0.002 - 0.54 2.5 (RMEG)

1Comparison values have not been developed specifically for sediment. Listed values were derived assuming exposure of children to contaminants in soils.

*Concentrations are in parts per million (to convert to ppb multiply x 1000).
Values for organic compounds are considered estimates.

TABLE 4.

SURFACE WATER CONTAMINANTS (1985) (2)
SUBSTANCE CONCENTRATION
RANGE
(ppb)
COMPARISON*
VALUES
(ppb)

INORGANIC COMPOUNDS  
arsenic < 2.0 - 3,070 15 (RMEG)
cadmium < 0.2 - 1,100 2 (EMEG)
chromium < 4.0 - 5,544 50 (RMEG)
lead < 2.0 - 11,300 5 (PMCL)
mercury nd - 11 2 (MCL)
     
VOLATILE ORGANIC COMPOUNDS  
chlorobenzene < 1.4 - 19,000 200 (RMEG)
chloroform < 1.6 - 4,200 100 (EMEG)
ethylbenzene < 0.7 - 4,000 700 (PMCL)
2-hexanone nd - 16,000 NA
methylene chloride

< 3.6 - 10,000

600 (EMEG)
tetrachloroethylene < 1.8 - 5,200 5 (PMCL)
toluene < 1.0 - 59,000 1,000 (MCLG)
trans-1,2-dichloroethylene < 1.1 - 4,200 70 (PMCLG)
1,1,1-trichloroethane < 0.6 - 2,600 200 (MCL)
trichloroethylene < 1.1 - 10,000 5 (MCL)
xylenes < 1.7 - 16,000 10,000 (PMCLG)
     
SEMIVOLATILE ORGANIC COMPOUNDS  
aniline < 0.1 - 61 6 (CREG)
N,N-dimethyl formamide nd - 1,580 1000 (RMEG)
2-methylphenol < 0.06 - 136 NA
4-methylphenol < 0.05 - 420 NA
2-methyl 2,4-pentanediol nd - 308 NA
     
PESTICIDES    
aldrin < 0.05 - 14 0.3 (RMEG)

nd - not detected; NA - Not available

*Comparison values are based on drinking water exposure and are included here even though this water is not used as a drinking water source.

C. TOXIC CHEMICAL RELEASE INVENTORY (TRI)

To identify facilities that release chemicals into the environment near the MSGS site, MDE searched the 1987, 1988, and 1989 Toxic Chemical Release Inventory (TRI). TRI is a data base developed by EPA from the chemical release (to air, water, soil) information provided by certain manufacturing industries. A federal law requires that facilities of a certain size report on the releases of over 300 listed chemicals and chemical categories.

Several facilities located within an approximate 3-mile radius of the site were identified in the TRI database. The facility that is closest to the site is the Thiokol Corporation, located in the Trinco Industrial Park, about 1.5 miles east of the site. Thiokol reported annual air emissions of about 100,000 pounds of the chemical 1,1,1-trichloroethane for the three years included in the data base. This is one of the contaminants that was consistently found in on-site water and sediments. Another facility located within the Trinco Industrial Park reported relatively small releases of several different pesticides. The highest emissions were reported for the pesticide Carbaryl (about 2,500 lbs. in 1988). Smaller annual emissions of several other pesticides were reported by the same company.

Several facilities that reported TRI emissions are found about 2.5 to 3 miles from the site. One company, about 2.5 miles southeast of the site, reported air emissions of acetone and styrene in 1987 and 1988, and acetone only in 1989. Two facilities that are in Elkton (east of the site) reported emissions of xylenes (all years), methanol (all years), and vinyl acetate (1987 and 1988).

Most of the TRI emissions from plants in the site vicinity are relatively small and would not be expected to affect the health of exposed individuals. The largest reported air emission, for the chemical 1,1,1-trichloroethane, is from a facility that is fairly close to the site. This is significant because it suggests that local residents could be potentially exposed to this chemical from the site and, as a result of its release (in the air), from the Thiokol facility. It is important to note that Maryland currently has a law that limits companies' emissions of toxic air pollutants to levels that will not endanger the health of the public.

D. QUALITY ASSURANCE AND QUALITY CONTROL

The report for the Phase I Remedial Investigation/Feasibility Study does not include a discussion of a Quality Assurance/Quality Control (QA/QC) review of the data. Standard QA/QC procedures were followed during collection and analysis of environmental samples. A QA/QC review was completed for the chemical analysis that was conducted as part of the Phase II RI/FS (9). The authors of this review concluded that overall, the data quality for organic chemical analysis is good. They note, however, that a fair portion of the organic chemical data should be considered estimates. These values were noted as estimates in the data tables that are included in the Phase II report (5). It does not appear that there were deficiencies in the quality of sample collection and analysis that would cause MDE to question the conclusions that were made based on the Phase I and Phase II investigations.

As noted previously, structural problems are believed to be the cause of elevated metal concentrations that were found in 2 on-site wells monitoring the lower sand unit (6). Well D&M 09 in the EEA was vandalized and could not be adequately purged (i.e., existing water pumped out) before it was sampled. In well D&M 06 in the WEA, grout was found to be clogging the well screen and as a result, analytical results were considered unreliable. Replacement wells were constructed for both of these wells.

E. PHYSICAL AND OTHER HAZARDS

No physical hazards of note were observed on-site during the November 1988 or the October 1991 site visits. Current conditions at the site have not changed. A new fence surrounding the EEA was constructed during January 1988. Vandalism of the site was apparent during the 1988 visit, including the creation of holes in the new fence. The damage to the fence would have allowed trespassers access to the site, and, as a result, the potential for exposure to contaminants. No evidence of vandalism was observed during the 1991 visit, nor have trespassing problems been reported since then.


PATHWAY ANALYSIS

Exposure pathways are analyzed in order to determine the means by which individuals (primarily local residents) may be exposed to site contaminants, either currently or in the past. An exposure pathway consists 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.

Exposure pathways can be described as completed, potential, or eliminated. In a completed exposure pathway, all elements exist and indicate that exposure to a contaminant has occurred in the past or is occurring. In potential exposure pathways, at least one of the five elements is missing. It is possible that the missing element exists (e.g., an exposed population) but has not been identified. Potential pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring now, or could occur in the future. An exposure pathway can be eliminated if an element is missing and will likely never exist.

A. COMPLETED EXPOSURE PATHWAYS

1. Private Wells
As previously noted, on-site groundwater monitoring indicates that the shallow groundwater in the EEA is highly contaminated with volatile and semivolatile organic compounds, and inorganic compounds. Groundwater contaminants in the EEA can migrate downward into lower groundwater units. Contaminants can migrate downward and enter lower units directly if there is no confining layer (e.g., clay) between them, or if there are openings between confining layers. Contaminants can also enter surface water through seeps and then reinfiltrate the ground at another point.

Groundwater at the site migrates towards the south. VOCs have been discovered in the middle sand unit downgradient (south and southeast) of the site. Low concentrations of VOCs were also discovered in samples from the lower sand and bedrock groundwater units in the WEA. These findings indicate that groundwater contaminants at the site have migrated towards the south and have moved vertically into deeper groundwater units.

No site-related completed exposure pathway through use of groundwater has been identified. However, low levels of some VOCs were identified in residential wells west and north of the site. These chemicals were also found in laboratory blanks, however, making it likely that there presence in the well samples was due to laboratory contamination. More recent sampling indicate that one residential well west of the site does contain low levels of VOCs, but that contamination is not believed to be site-related. The resident is supplied bottled water. Therefore, the resident is no longer exposed to the VOCs in well water through ingestion. However, exposure continues through inhalation of the volatilized contaminants and through skin contact with contaminants in the water.

2. Ambient Air
Although there are no records of any analyses being conducted at the site that could identify specific airborne contaminants, this is considered a completed pathway because of the recorded odor complaints from people to airborne contaminants both on and off site. Chemicals that are directly exposed to the air can evaporate and be carried from the site in the prevailing winds. As noted previously, volatile organic vapors have been detected immediately above on-site ponds. Contaminants also adhere to soil particles and can become airborne by wind action and/or disturbances of the soil.

The most likely contaminants to be found in the air near the site are volatile organic compounds. Many VOCs have been identified as site contaminants, so that some off-site migration by the air pathway would be expected. The semivolatile organic compounds would tend to adsorb more strongly to soil particles than would the volatile compounds.

It is documented that site inspectors and residents living near the site have been exposed to contaminants by the air pathway. There are records of site inspectors complaining of strong odors and eye and nose irritation during past site inspections (1). Residents living adjacent to the site also complained of strong chemical odors from the site and associated health effects (not specified) in the past (1). The highest air levels from the volatilization of surface contaminants would occur during warm weather periods. The predominant wind direction in the site area during the summer is from the south. Therefore, the people living just north of the site along Marley and Nottingham Roads are in the path of these winds (and any associated contaminants) during the summer months. MDE estimates that about 100 to 150 people live in this area, based on the number of homes and the average number of people per household (1980 census for Cecil County).

Air concentrations were likely the highest when open lagoons of chemical liquids and sludges were found at the MSGS site (during the mid-1970s). Wastes were removed from the lagoons during 1975 and 1976. One record of a local resident's complaint regarding strong odors, however, was made in 1979, after the liquid sludges were removed from the site.


TABLE 5.

COMPLETED EXPOSURE PATHWAYS
PATHWAY ENVIRONMENTAL
MEDIA
POINT OF
EXPOSURE
ROUTE OF
EXPOSURE
EXPOSED
POPULATION
TIME
Well Water (not site-related) Groundwater Tap Ingestion (past), Inhalation, Dermal Contact People using RW10 Past
Current
Future
Ambient
Air
Air On-site
and nearby
residences
Inhalation Site
trespassers,
workers,
local
residents
Past


Table 6.

POTENTIAL EXPOSURE PATHWAYS
PATHWAY ENVIRONMENTAL
MEDIUM
POINT OF
EXPOSURE
ROUTE OF
EXPOSURE
POTENTIALLY
EXPOSED
POPULATION
TIME*
Sediment Sediment On-site,
off-site in
Mill Creek
Ingestion,
Skin contact
workers,
trespassers
local
residents
Past
Present
Future
Surface soil Soil On-site Ingestion,
skin
contact
workers,
trespassers
Past
Present
Future
Surface
water
Water On-site,
off-site in Mill Crk.
Ingestion,
skin contact
Workers,
trespassers
children
Past
Present
Future
Private
wells
Groundwater Residence
Business
Ingestion,
inhalation,
skin contact
Users of
water from
private wells south
of the site
Future

*Because the site is currently secured, the potential for present and future exposures generally applies only to on-site workers

B. POTENTIAL EXPOSURE PATHWAYS

1. Exposure During Remediation
Workers could potentially be exposed to site contaminants while engaged in site remediation activities. Workers could be exposed by directly inhaling airborne contaminants, through direct contact with contaminated media, or by incidentally ingesting contaminated soil. Adequate personal protective measures should prevent exposures to unacceptable levels of contaminants.

2. Groundwater-Private Wells
Because groundwater flows to the south, wells located to the south of the site are at the greatest risk of contamination. Also, since higher levels of contaminants are found in shallow, on-site groundwater, shallower wells would be at greater risk of more severe contamination. If a residential well is contaminated, individuals could be exposed to contaminants through direct ingestion of the water and through other uses of the water, such as bathing and cooking.

There are only a few private wells supplying residences and businesses located along Route 40, Pulaski Highway, immediately south of the site. Samples from these wells were analyzed during the Phase I investigation in 1985. Selected wells are to be monitored periodically, and new data indicate that no contamination has been found in most private wells. The one exception is discussed in the Completed Exposure Pathways section.

3. Surface Soil and Sediments
Very high levels of heavy metals, VOCs, and some semivolatile organic compounds were detected in sediments from all 3 of the on-site ponds. If people have direct contact with contaminated sediment, chemicals can be absorbed through the skin. Also, hand contact with contaminated sediment could result in the incidental ingestion of contaminants as a result of hand-to-mouth activity.

The sediment sampling that was conducted in 1985 did not identify high levels of contamination in off-site sediments. The sediments in the section of Mill Creek just downstream of the site were not well characterized, however, and may have contained higher concentrations of contaminants than did the sediments farther downstream. State inspectors conducted biological surveys of Mill Creek in 1974, 1975, and 1976 and noted that the stream was degraded at a point 1 mile downstream of the site (1). If sediments in this section of the stream were contaminated, it could have served as a source of exposure to local residents, especially children.

Relatively low estimated concentrations of VOCs were also detected in soils that were sampled within the EEA and in 1 sample of soil from the WEA. It appears that in most cases the VOCs detected in the soils originated from the 3 on-site ponds. Soil contaminants were highest near the ponds, and contaminants found in soils were similar to those found in pond water and sediments. People who trespassed on the site could have been exposed to these soil contaminants by direct contact with skin and by the incidental ingestion of small amounts of soil.

The soil contamination that was detected in the 1 sample that was taken from the WEA during the Phase I investigation appears to have been an isolated case and not representative of this area of the site. Sampling of WEA subsurface soils that was conducted in 1985/1986 did not reveal any contamination and the testing of surface soils with a VOC meter did not identify any areas of surface contamination by VOCs (5). Also, there is no other evidence that wastes were disposed of in the WEA.

The soils that were sampled during the Phase I and II investigations in 1984 were taken from a depth of 6 inches or greater and may not accurately reflect the concentration of contaminants in shallower, surface soil. With respect to the WEA, it is unlikely that surface soil contamination would have been significantly greater than the levels that were measured in subsurface soils.

It is considered probable that people would have been exposed to contaminated surface soils and sediments. Site trespassers and workers would be at greatest risk for exposure by this pathway. Children who lived in the area and who were old enough to play without supervision would be the group most likely to have regularly entered the site. Also, people who rode dirt bikes and all-terrain vehicles on the site could have been exposed to soils and sediments. This group probably would have consisted primarily of males (adolescents and older) and would not be restricted to those who lived near the site.

4. Surface Water
Elevated levels of inorganic compounds, VOCs, and 1 semivolatile organic compound were identified in on-site surface waters. Individuals could be exposed to on-site surface water contaminants through direct contact. Contaminants could be absorbed through the skin following contact or accidentally ingested following contact with hands.

It is not known for certain whether or not individuals have been exposed to on-site surface water (or sediments). However, it is probable that contact with contaminated surface water has occurred because it is known that people have trespassed on the site in the past, and the proximity of residences makes it likely that children would have entered the site. Children represent the population of greatest concern because of the likelihood that they would contact water and sediments during play. It is also possible that workers may have been exposed to on-site surface waters.

Another potential pathway for exposure to contaminants in surface waters is through contact with water in Mill Creek and its tributary that drains the site. As previously noted, state inspectors reported in the mid-1970s that a section of Mill Creek downstream from the site was severely polluted (1). It is likely that contaminants in the creek were at their highest historic levels during this period. Surface water samples that were collected from Mill Creek in 1984 and 1986 did not have elevated levels of VOCs or metals. This finding is not unexpected; VOCs are the major class of contaminants at the site, and these chemicals would evaporate quickly following their entry into moving surface water.

As was noted for off-site sediment exposure, children living near the site are the group most likely to have been exposed to off-site surface water.


PUBLIC HEALTH IMPLICATIONS

Introduction

Exposure to sufficient amounts of some of the contaminants found at the MSGS site could result in adverse health effects in exposed individuals. It is difficult, however, to estimate the frequency or extent to which people may have been exposed to site-related contaminants.

For example, it was previously noted that there are records of complaints about strong odors and associated health effects (not identified) from residents living adjacent to the site. Also, state investigators noted strong odors and experienced irritation of the eyes, nose, and throat during their investigation of polluted surface waters. While it is apparent that some local residents and site investigators have been exposed to volatile airborne contaminants, the identity and concentration of these contaminants is not known, nor is the frequency of exposure.

People who entered the site and directly contacted contaminated materials (i.e., through dermal contact, inhalation, or ingestion) are the individuals with the greatest potential exposure to high concentrations of contaminants. Contaminants that have been identified in sediments and surface waters include one chemical, arsenic, that is classified by EPA as a known human carcinogen and five chemicals (cadmium, chloroform, methylene chloride, tetrachloroethylene, and aniline) that are classified as probable human carcinogens (based on studies in laboratory animals and exposed human populations). Chromium (form not specified) was also found in sediment and surface water. One form of chromium (Cr VI) is considered a human carcinogen, whereas the other major form (Cr III) is not classified as a carcinogen. Two other known human carcinogens, benzene and vinyl chloride, have been identified in on-site groundwater. Exposure to any of these known or probable human carcinogens could increase a person's risk for developing cancer. The greater the exposure to these chemicals, the greater would be the associated increase in the exposed individual's cancer risk. As noted previously, the degree to which people have been exposed to these contaminants on or off of the site is not known.

Exposure to sufficient quantities of a given site contaminant, could also result in other noncancer adverse health effects, a description of which follows for some site contaminants. Individuals exposed to site contaminants would likely be exposed to a mixture of different chemicals. There is relatively little available information on the possible health effects associated with exposure to chemical mixtures. It is possible that a person's health could be affected by exposure to a mixture of chemicals, even if exposure to the individual chemicals, by themselves, would not be expected to cause any symptoms.

For some chemicals, ATSDR has developed Minimal Risk Levels (MRLs). A MRL is an estimate of daily human exposure to a contaminant, below which non-cancer, adverse health effects are unlikely to occur. MRLs are developed for ingestion and inhalation exposure routes, and for the length of exposure, such as acute (less than 14 days), intermediate (15 to 364 days), and chronic (greater than 365 days). MRLs for specific chemicals are included in documents, called Toxicological Profiles, that have been developed by ATSDR for common environmental contaminants.

Not all of the substances listed in Tables 1 through 4 are discussed below. An emphasis has been placed on contaminants with available toxicology data and that have been found in several different media.

A. TOXICOLOGICAL EVALUATION

Metals

Arsenic-- Ingesting relatively low levels of arsenic (about 300 to 30,000 ppb in food or water) can cause irritation of the gastrointestinal system and result in symptoms such as pain, nausea, vomiting and diarrhea. Ingestion of arsenic can also have adverse effects on the blood, heart, and nervous system (10). The severity of symptoms in affected individuals tends to increase with an increase in exposure duration. Arsenic is also classified by EPA as a human carcinogen, and has been associated with lung cancer through the inhalation route and skin cancer through ingestion of arsenic-contaminated water (10). Elevated levels of arsenic have been found in on-site sediment and surface water.

Incidental ingestion by children of sediment containing the highest concentration of arsenic measured on site (290 ppm) could result in a dose that exceeds the EPA's Reference Dose for arsenic (10). The estimated exposure in this case is based on the assumption that a child ingests 200 mg of soil per day. Assuming that exposure of children to arsenic through this pathway would be infrequent, if at all, adverse effects resulting from this exposure would not be expected in this population. Site data are too limited to estimate the degree to which people may have been exposed to arsenic in on-site surface soils.

Cadmium-- Oral exposure to cadmium may result in adverse effects on the kidneys, liver, bone, the immune system and the cardiovascular system (11). Long-term inhalation of cadmium may lead to lung cancer. The major concern with respect to long-term exposure to low levels of cadmium is injury to the kidney (11). ATSDR has developed a chronic MRL for oral exposure to cadmium. Cadmium was found at elevated concentrations in on-site surface water and sediments. The high levels of cadmium that were found in on-site sediments (up to 457 ppm) could have resulted in doses to children or adults that exceed the chronic MRL through incidental ingestion (11). The population of greatest concern would be children who played on the site and accidentally ingested sediment (for example, after getting it on their hands). The likelihood for adverse health effects resulting from this exposure route is low because it is unlikely that exposure to cadmium through this route would have been a frequent occurrence.

Organic compounds

Benzene-- Benzene is a naturally occurring substance produced by volcanoes and forest fires and present in many plants and animals, and is also an industrial chemical made from coal and oil. Benzene is used to make other chemicals and products, such as pesticides and some plastics, and is a component of gasoline. People can be exposed to benzene in the workplace through common environmental sources such as tobacco smoke and automobile exhaust (12). Long-term exposure (less than five and up to 30 years) to benzene in the workplace has been found to increase the risk of leukemia in exposed workers (12). Leukemia is a type of cancer of the tissues that form the white blood cells. Human and animal studies also show that benzene can be harmful to the immune system (the system that fights infections in the body). Studies in female laboratory animals have also shown that benzene can adversely affect unborn animals (12).

Benzene has been discovered in shallow groundwater at the MSGS site at a concentration of approximately 69 ppm. Based on the available information, it is unlikely that an individual on the site would have been exposed to a sufficient quantity of benzene to result in adverse health effects.

Di(2-ethylhexyl)phthalate (DEHP)-- DEHP is a chemical that is commonly used to make plastics more flexible. Plastics may contain from 1% to 40% DEHP by weight. Humans are primarily exposed to DEHP through foods that come into contact with packaging material that contains it. Foods contribute an average of about 0.25 mg DEHP in a person's diet (13). There are no studies on the health effects of long-term exposure of humans to DEHP. Studies in which laboratory animals (rats and mice) were orally exposed to DEHP have shown the liver to be the organ that is most sensitive to the toxic effects of this chemical following acute ( < 15 days), intermediate (15 to 364 days), or chronic ( > 364 days) exposure (13). DEHP has also produced liver cancer in rats exposed to high concentrations of the chemical in food over a two year period. DEHP has been detected in concentrations of up to 1,500 ppm in on-site sediments and 59 ppb in deep groundwater. Occasional exposure of children to 1,500 ppm DEHP in sediments (resulting in the incidental ingestion of an estimated 200 mg of sediment) would not be expected to cause adverse health effects. This exposure would also not be expected to result in a significant increase in an individual's lifetime risk of developing cancer (13).

Chlorobenzene-- Chlorobenzene is used as an industrial solvent and to make other chemicals. Workers exposed to high levels of airborne chlorobenzene have complained of a number of symptoms, including headache, sleepiness, and nausea (14). As is true with other organic solvents, chlorobenzene can cause depression of the central nervous system (brain and spinal cord). Inhalation and oral exposure of laboratory animals to chlorobenzene has produced damage to the liver and kidneys. In the species that have been tested, these organs appear to be the most sensitive to the toxic effects of chlorobenzene (14). Chlorobenzene has been found in all on-site media that have been tested, with the highest concentration found in sediment (1,700 ppm).

People entering the site could be exposed to chlorobenzene through a number of different routes, including inhalation, direct contact, or incidental ingestion. ATSDR has developed a MRL for intermediate (up to 1 year) oral exposure to chlorobenzene and EPA has developed a Reference Dose (RfD) for chronic exposure. It is unlikely that either of these levels would be exceeded by someone who came into contact with chlorobenzene on the site and incidentally ingested a small amount of contaminated sediment. There is insufficient information to estimate the amount of chlorobenzene that a person might absorb through inhalation or through the skin (14).

1,2-Dichloroethane-- 1,2-Dichloroethane (1,2-DCA) is used in industrial solvents and in the production of vinyl chloride. In the past, 1,2-DCA was also used in consumer products such as cleaning solutions, pesticides, and adhesives. Relatively little is known about the effects of long-term exposure to 1,2-DCA in humans. There is information on humans exposed for a short period to large amounts of this chemical in the air or by ingestion. In these cases, 1,2-DCA caused damage primarily to the liver, kidneys, brain, and lungs (15). Laboratory animals exposed to high concentrations of 1,2-DCA also showed toxic effects on the liver and kidneys. In another experiment, mice given daily oral doses of 1,2-DCA for 14 days showed adverse effects on their immune systems. Lifetime oral exposure of laboratory animals (rats and mice) to high concentrations of 1,2-DCA caused cancer at a number of different sites (15).

1,2-DCA has been found at a relatively low concentration (up to 234 ppb) in shallow groundwater at the MSGS site. Based on the available information, it is not expected that an individual who occasionally entered the site would have been exposed to a sufficient amount of 1,2-DCA to cause adverse health effects.

Ethylbenzene-- Ethylbenzene is a colorless liquid with a strong odor that occurs naturally in coal tar and oil. It is also found in many man-made products, including paints, inks, insecticides, and gasoline. People exposed to relatively high levels (about 1,000 ppm) of ethylbenzene in the air for short periods of time have complained of eye and throat irritation, and higher levels have caused dizziness (16). It has been shown that pure or diluted (in water) ethylbenzene can be absorbed through human skin. Eye irritation has been observed in laboratory animals at lower air concentrations (about 382 ppm). There is little available information on the effects of long-term exposure of humans to ethylbenzene. Short-term exposure of laboratory animals to high concentrations of ethylbenzene in air has caused liver and kidney damage and effects on the blood and nervous system. ATSDR has developed a MRL for intermediate length (less than 1 year) exposure to ethylbenzene in air, and EPA has developed a Reference Dose for chronic exposure to this chemical (16). Ethylbenzene has been found in on-site groundwater, surface water, and sediments, with the highest level (550 ppm) found in sediments. Adverse health effects would not be expected to result from occasional exposure of a child or adult to sediment contaminated with ethylbenzene.

Methylene Chloride-- Methylene chloride, also known as dichloromethane, is an organic solvent that is widely used as an industrial solvent and as a paint stripper. It is also found in some aerosol and pesticide products. Exposure to high levels of methylene chloride in the air (above about 500 parts methylene chloride per 1 million parts air) can irritate the eyes, nose, and throat, and cause depression of the central nervous system (17). Studies in laboratory animals have shown that frequent or lengthy exposures to methylene chloride can affect the liver and kidney. However, based on these studies and those of exposed workers, it appears unlikely that methylene chloride would cause serious liver or kidney damage in humans unless exposure is very high (17). ATSDR has developed a MRL for chronic oral exposure to methylene chloride. Exposure of laboratory mice to very high levels of methylene chloride for a lifetime caused an increase in cancers of the liver and lungs. Based on these studies, EPA has classified methylene chloride as a probable human carcinogen. Epidemiological studies of humans exposed to methylene chloride for up to 30 years in the workplace have not found evidence of increased cancer deaths (17).

Methylene chloride has been found in surface water and sediments at the MSGS site, with an estimated maximum concentration of 32,000 ppm found in sediments. Occasional exposure of a child to this level of methylene chloride in sediment (and resulting incidental ingestion of sediment) could result in a dose that exceeds the chronic MRL, which may result in non-cancer adverse health effects, and also may result in a slight increase in an individual's lifetime risk of developing cancer. The information on the site is not adequate to allow estimation of an individual's potential exposure to methylene chloride through inhalation or dermal absorption.

Tetrachloroethylene--Tetrachloroethylene (PCE) is a common chemical that is widely used for dry cleaning and as an industrial solvent. It is also found in some consumer products such as silicone lubricants, spot removers, and adhesives. PCE has caused central nervous system depression (e.g., dizziness, headache, confusion) in individuals exposed to high concentrations in air, primarily in occupational settings (18). Exposure of laboratory animals to tetrachloroethylene in the air has resulted in adverse effects on the central nervous system, liver, and kidney. Similar effects have been observed in laboratory animals following repeated oral exposures. PCE has also caused cancer (leukemia, liver, and kidney cancer) in laboratory animals following long-term oral or inhalation exposures. Based on this information, EPA has classified this chemical as a probable human carcinogen. ATSDR has developed an MRL for an intermediate length (< 1 yr) oral exposure to PCE, and EPA has developed a Reference Dose for chronic oral exposure (18). PCE has been identified in on-site sediments, surface water, and groundwater, with a maximum estimated concentration of 750 ppm found in sediment. Exposure of a child or adult to this level of PCE in sediment would not be expected to cause adverse health effects.

Toluene-- Toluene is found in crude oil and it is widely used in industry as a solvent. People can be exposed to toluene in the workplace or through consumer products such as gasoline, nail polish, adhesives, inks, and paints. As is true with most organic solvents, the major effect of toluene in humans is on the central nervous system. Short term exposure to moderate amounts of toluene can cause symptoms in people that are similar to drunkenness. Symptoms include fatigue, incoordination, dizziness, and nausea (19). Long-term exposure to low and moderate amounts of toluene has caused slight effects on the kidneys in some people, but these people were also exposed to other solvents at the same time, making it difficult to tell which chemical caused the effects. In laboratory animals, the main effect of toluene is also on the nervous system; however, exposure-related effects have been observed in the liver, kidneys, and lungs (19).

Toluene has been identified in all media that have been tested on the MSGS site, including deep groundwater. The highest level (3,200 ppm) of toluene was found in on-site sediments. ATSDR has developed a MRL for intermediate exposures (up to 1 year) to toluene in air, and EPA has developed a Reference Dose for long-term oral exposure to toluene (19). Adverse health effects would not be expected based on occasional exposure of a child or adult to the highest level of toluene found in sediments.

1,1,1-Trichloroethane-- 1,1,1-Trichloroethane (TCA) is a chemical that is commonly used in industrial solvents and as a component of consumer products such as glues, cleaning products, and aerosol sprays. Humans exposed to high vapor concentrations of TCA have shown effects on the nervous system that resemble alcohol intoxication, including dizziness and incoordination (20). Exposure of laboratory animals to TCA caused damage to the lungs and less serious effects on the liver. Oral exposures of animals to high levels of TCA resulted in liver damage (20). 1,1,1-TCA was found in all of the media that were sampled on the site, with the highest concentration (95 ppm) found in sediment. No health-based comparison values have been developed for this chemical; therefore, adequate evaluation of possible health outcomes related to exposure cannot be made. The levels that people would be exposed to at the site are much lower than occupational exposures where adverse effects have been seen, and for that reason, exposures at the site are not expected to cause those effects (20).

Trichloroethylene-- Trichloroethylene (TCE) is used as an industrial solvent and as a component of a number of different consumer products, including paint removers, glues, and cleaning fluids. Short-term exposures to high enough concentrations of TCE can produce effects on the central nervous system that are similar to alcohol intoxication, including dizziness, sleepiness, and slowed reaction times (21). Repeated oral or inhalation exposure of laboratory animals to TCE has caused damage to the liver and kidneys. TCE has also caused an increased incidence of cancer at a number of different sites in laboratory animals following long- term oral or inhalation exposures. Studies of humans exposed to TCE in drinking water have shown a possible association with leukemia (21).

TCE has been found in all of the on-site media that have been tested, with the highest estimated level (580 ppm) found in on-site sediments. ATSDR has developed a MRL for intermediate length (< 1 yr) oral exposure to TCE. A child or adult occasionally exposed to TCE in sediment would not be expected to ingest a quantity of TCE that would exceed this MRL; therefore, no non-cancer adverse health effects are expected to result from exposure to site contaminants (21).

TCE was also detected in one private well at 7 ppb. The source of the TCE in that well water has not been determined, but it is not believed to be related to the site. The resident is now supplied with bottled water. Ingestion of water containing 7 ppb TCE for a limited period of time is not expected to result in non-cancer, adverse health effects (21); however, if the resident should resume use of the well water as a potable source, further evaluation should be considered. Likewise, exposure to TCE at 7 ppb is not expected to result in an increased risk of developing cancer (21), but because of a lack of information on TCE's carcinogenicity potential, exposure should be avoided if possible.

Vinyl chloride-- Vinyl chloride (a gas at room temperature) is used to make a plastic called polyvinyl chloride (PVC). PVC is used in the manufacture of many plastic and vinyl products. Humans occupationally exposed to relatively high levels of vinyl chloride vapors have shown damage to the liver, central nervous system, and injury to the fingers (22). Long-term occupational exposures have also been associated with cancer of the liver and possibly the brain. Vinyl chloride is classified by EPA as a human carcinogen. Exposure of laboratory animals to vinyl chloride vapor has also caused liver cancer (22).

There is no information on the effects of vinyl chloride in humans following oral exposure. Oral exposure of laboratory animals to vinyl chloride has caused liver toxicity and cancer of the liver (22). Vinyl chloride was found in shallow groundwater on the MSGS site at a maximum concentration of about 1 ppm, and in deep groundwater at a concentration of 6 ppb. Vinyl chloride can be formed by the environmental breakdown of similar chemicals (22). A person exposed to 6 ppb vinyl chloride in drinking water for a lifetime would have a slight increase in their lifetime risk for developing cancer as well as developing some non-cancerous effects.

B. HEALTH OUTCOME DATA EVALUATION

As noted previously, the Maryland Department of Health and Mental Hygiene has vital statistics (births and deaths) and birth defects data available for given time periods at the county level. In the discussion that follows, the rates for Cecil County are compared to rates for the state as a whole.

MDE believes that it is unlikely that people have been exposed to sufficient quantities of contaminants from the MSGS site to result in detectable increases in exposure-related illness. This notwithstanding, an evaluation of the available health outcome data is included in this section. A number of points should be considered when these data are evaluated with respect to the potential impact of exposure to site-related contaminants. These points include the following:

1) A plausible link between exposure to a chemical and an adverse health effect requires that the chemical be capable of causing the effect of concern, and that there was sufficient exposure (resulting in enough of the chemical being absorbed into the body) to cause the effect.

2) If exposure to site contaminants did cause serious adverse health effects in some exposed individuals, it might not be possible to detect this using the available health outcome data. For example, if exposure to contaminants from the site resulted in 2 deaths from lung cancer (as noted, we do not consider this plausible), these "extra" cases might not cause a noticeable increase in the lung cancer death rate when they are combined with all of the other lung cancer deaths for Cecil County. This is especially true if the disease of concern (such as lung cancer) is not rare.

3) A certain disease or condition (e.g., a certain type of cancer or birth defect) may occur at a greater than expected rate in Cecil County as compared to the state of Maryland as a whole due to chance alone. Also, observed differences between state and county rates may be due to differences in the two populations. For example, if the risk of a certain birth defect increases with the age of the mother, and the defect is observed to be increased in the county as compared to the state, the reason for the increase may be due to a greater proportion of older women giving birth in the county during the observed period.

It should be noted that if the public health assessment team at MDE suspected that exposure to site-related contaminants was causing disease or illness in an exposed population, MDE would recommend that a more detailed study of this population be initiated. This recommendation will also be made if a review of health outcome data that become available in the future indicates the need for a more detailed investigation.

With the above points in mind, the following health outcome data have been reviewed for Cecil County:

Birth Defects
Data for the occurrence of thirteen separate birth defects (referred to as sentinel defects) are available for Maryland at the county level for the years 1984 to 1988. During this period, the incidence rate for infants born with one or more of the 13 defects was 95.9 per 10,000 births for Cecil County (34 infants out of 3,547 total births) as compared to 63.8 per 10,000 (1,920 infants out of 300,882 births) for the State of Maryland as a whole. The two types of birth defects that occurred at a significantly higher rate among Cecil County births were spina bifida with or without hydrocephaly (14.1 per 10,000 live births for the county as opposed to 5.3 per 10,000 live births for the state) and Down Syndrome (19.7 per 10,000 live births for the county as opposed to 7.2 per 10,000 live births for the state).

The birth defect rates for spina bifida and Down Syndrome in Cecil County are based on totals of 5 and 7 cases, respectively, out of 3,547 births that occurred in the county during the 4 year period. These rates are thus based on a small number of cases. The observed elevation in the rates for these two birth defects cannot be related to the site, and may be due to chance alone.

Cancer Mortality
Age-adjusted (to 1970 U.S. population), cancer death rates per 100,000 population are available at the county level for the period of 1983 to 1987. Average annual cancer death rates were not significantly different (based on statistical analysis) for Cecil County as compared to the State of Maryland as a whole for the most common forms of cancer (see table which follows).

 

  Maryland Cecil County
  (cancer death rates per 100,000)
     
ALL 193 184
     
Bronchus/Lung 53 56
Breast 30 22
Prostate 27 26
Bladder 4 4

Cervix

3 1
Colon 20 20
Lymphoma 6 6
Esophagus 5 3
Melanoma 2 3
All Other 43 43

It can be concluded that during the period from 1983 to 1987, residents of Cecil County did not die from the cancers listed above at rates that differed significantly from the residents of the State of Maryland as a whole. As noted previously, no conclusions can be made regarding the impact of site-related contaminants on the health of exposed individuals based on our evaluation of the available health outcome data.

C. COMMUNITY HEALTH CONCERNS EVALUATION

Recent health concerns with respect to the MSGS site and other comments on this public health assessment are addressed in Appendix B. There have been opportunities for the community to express such concerns at two public meetings and during the public comment period for this public health assessment. MDE will continue regular communication with local and federal health officials to ensure that any health concerns that may be expressed to these officials by local residents are expressed.

In 1976, local residents complained of alleged health effects resulting from exposure to airborne contaminants that are believed to have originated from the site. During that year, some area residents also brought a law suit against Galaxy Chemicals Company and Maryland Sand and Gravelstone Company for damages resulting from airborne contaminant exposure. No specific description of the alleged health effects could be located.

There are no air sampling data that would allow for an estimation of the concentrations of specific contaminants to which residents may have been exposed. Because of this, it is not possible to identify the types of health effects that might be expected as a result of these exposures.

Complaints about off-site odors were voiced during a period in which liquid wastes and sludges were disposed of on site in open lagoons. Off-site odors were likely greatly diminished as a result of removal of liquid wastes from the site and the burial of sludges and drums.



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