PUBLIC HEALTH ASSESSMENT
NAVAL SURFACE WARFARE CENTER
INDIAN HEAD DIVISION (NSWC-IHDIV)
(a/k/a INDIAN HEAD NAVAL SURFACE WARFARE CENTER)
INDIAN HEAD, CHARLES COUNTY, MARYLAND
EVALUATION OF ENVIRONMENTAL CONTAMINATION, EXPOSURE PATHWAYS, AND PUBLIC HEALTH IMPLICATIONS
Based on the results of our site visit, and a review of the data and information currently available, we conclude that one exposure situation at NSWC-IHDIV currently poses a public health threat. Exposures to lead in the Navy housing are occurring at concentrations that may cause adverse health effects. In addition, two potential situations are identified in which exposures may have occurred in the past or could occur in the future to contaminant levels of health concern. A fourth situation does not pose a public heath concern because the base has taken action to reduce the chances of exposure to the chemical contaminants.
Table 1 summarizes ATSDR's public health conclusions for the exposure situations identified at NSWC-IHDIV, and a detailed discussion of each situation. Additional information describing ATSDR's public health conclusion categories is provided in Appendix C.
TABLE 1. Summary of ATSDR's Public Health Conclusions for NSWC-IHDIV.
| CONCLUSION CATEGORY | SITUATION |
| Public Health Hazard | Exposure to Residential Sources of Lead |
| Potential Health Hazards | Exposure to Mercury in Buildings 101 and
102
Fish in Mattawoman and Chicamuxen Creeks |
| No Public Health Hazard | Drinking Water Supply-Patapsco and Patuxent Aquifers |
I. Public Health Hazard: Exposure to Residential Sources of Lead
Summary: The lead in exterior and interior paints, foundation soils, and household dusts, at NSWC-IHDIV housing poses a health hazard to residents, particularly children 6 years of age and under and women of child-bearing age. Calculations using lead data from foundation soils demonstrate the potential for blood lead levels of resident children to increase above the CDC public health standard of 10 micrograms per deciliter (µg/dL). The base should take action to improve the voluntary lead screening program to ensure coordination of educational efforts, blood lead testing, reporting and tracking, and an action plan in the event that blood lead levels meet or exceed 10 µg/dL. A summary of our evaluation of this situation is provided in Table 2.
Background: NSWC-IHDIV currently maintains housing on the base (the Detached single family housing and the Riverview Village apartments). Off-base housing in the nearby towns of La Plata and Waldorf was taken out of service in 1997. Additional Detached housing at the Stump Neck Annex was taken out of service in November of 1996. The housing ranges in age from approximately 30 to 80 years and has been identified by NSWC-IHDIV as a source of residential lead exposure requiring risk reduction and abatement actions.
Lead is a public health concern in private and public housing throughout the United States, particularly in urban areas with greater numbers of older housing units. Although use of lead-based paint in housing was banned in 1977, approximately 74 percent of housing in the United States built before 1980 contains lead paint. Lead-based paint is a significant source of child lead poisoning (7).
Children can be exposed to lead from multiple sources. At the NSWC-IHDIV, those sources include lead-contaminated paint chips, household dusts, and foundation soils (soils located near the base of the buildings). In 1991-1992, the Navy Public Works Center/Norfolk sampled the interior paint, household dusts, exterior paint, and foundation soils at each of the housing locations. The data demonstrate that the interior and exterior paint (Detached housing, Riverview Village, and La Plata), household dusts (Detached housing), and foundation soils (Detached, La Plata, and Waldorf) of many these residential units are contaminated with lead at levels exceeding Housing and Urban Development (HUD) action criteria (8).
Regardless of whether the HUD lead screening criterion for any single source is exceeded in a residential setting, ingestion and inhalation of lead from multiple sources in a child's environment may result in exposures that pose a potential health hazard.
The Centers for Disease Control and Prevention (CDC) recommends that all children be screened for lead poisoning at least annually, especially children between the ages of 6 months and 6 years of age (9). Young children and fetuses are most vulnerable to lead toxicity for several reasons, including: (i) greater absorption and metabolism of lead than adults, (ii) rapidly developing nervous systems, and (iii) higher intakes of air, food, and water on a body weight basis. In addition, children age 3 and under tend to chew and mouth their hands, toys, and other objects, exposing them to lead dusts and paints (9). Blood lead levels of 10-40 micrograms per deciliter (µg/dL) may not cause distinctive symptoms of lead poisoning, but are associated with impaired central nervous system development, lower IQs, and hearing problems in children (7,9).
Based on the toxicity of lead at low concentrations in the blood, the CDC recommends that children's blood lead levels fall below 10 µg/dL (9). Historically, NSWC maintained no database of past blood lead testing results which could be reviewed by ATSDR during the public health assessment. However, blood lead tests conducted by the base in 1991 demonstrated that all children (6 months to 6 years of age) living in the Detached housing units tested positive for lead, with levels ranging from 2 to 9 µg/dL (8). Although the range is below the CDC criterion, this data set represents blood lead concentrations at a single point in time several years ago and is limited to only a subset of the children living on the base in 1991. During the public health assessment, NSWC provided additional blood lead data obtained in 1997 through their
TABLE 2. Public Health Hazard Situation: Residential Lead
| PATHWAY NAME | CONTAMINANTS | EXPOSURE PATHWAYS ELEMENTS |
TIME |
COMMENTS | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
EXPOSED POPULATION |
||||
Lead-Based Paint in Detached, Riverview, Waldorf, and La Plata Navy residential housing |
Lead |
Flaking and deteriorating lead-based paint on interior and exterior surfaces of on-base and off-base Navy residential housing |
Soil, Air |
(I) Lead-contaminated household dusts (Ii) lead-contaminated painted surfaces (Ii) lead-contaminated paint chips, soils |
Inhalation (of lead-contaminated dusts) Ingestion |
Children residents (particularly ages 6 and under; approximately 65 children*) Adult residents, particularly pregnant and nursing women, and women of child-bearing age (approximately 93 women between the ages of 15 and 44 years*) |
Past Current Future |
Calculations assuming exposure to NSWC-IHDIV residential foundation soil lead concentrations demonstrate potential increases in child blood lead levels above the CDC public health standard of 10 µg/dL. NSWC-IHDIV is evaluating and modifying its current blood lead poisoning prevention program to better address the specific residential lead exposure situation at the base. |
* Population estimates based on July 1997 NSWC-IHDIV housing demographics: Waldorf and La Plata data were not provided.
voluntary blood lead screening program (10). Data from five of the 65 children living in the
Detached (one child) and Riverview (four children) housing demonstrate that these five
children have not been exposed to lead at levels of health concern. Blood lead concentrations
in these children ranged from 2 - 3 µg/dL, well below the CDC screening criterion. The U.S.
national average blood lead concentration for children ages 1-2 years and 3-5 years is 4.1 and
3.4 µg/dL, respectively (7, 11).
Since the housing inspection results indicate that the children living in NSWC-IHDIV housing are at high risk for lead exposure, historical annual screening data and limited current blood lead data are available for these children, ATSDR evaluated the potential for blood lead levels of children residing in NSWC-IHDIV housing to exceed public health criteria. We used the site-specific NSWC-IHDIV soil lead data, and an algorithm that relates potential increases in blood lead levels to concentrations of lead in soils, to estimate the potential for blood lead levels to exceed the 10 µg/dL public health criterion for children. The algorithm, soil lead data, assumptions, and calculations are provided in Appendix D.
The calculations in Appendix D demonstrate the need for regular blood lead screening for the children in residence at the NSWC-IHDIV. Calculated increases in blood lead levels ranged from 7.1 (Riverview Village apartments) to 23.5 (Detached housing) µg/dL. Adding these values to the baseline blood lead concentrations for U.S. children (noted above), one arrives at predicted blood lead levels ranging from approximately 11 to 27 µg/dL for children living in NSWC-IHDIV housing. Thus, exposures to the foundations soils at the Detached housing, Riverview Apartments, La Plata and Waldorf units, could potentially result in increases in blood lead levels which exceed the 10 µg/dL screening criterion.
These calculations may overestimate potential increases in blood lead levels by assuming regular exposure to the lead-contaminated soils; however, the evaluation addresses only one (foundation soil lead) of several potential lead exposure pathways identified for children in the NSWC-IHDIV residential setting. The value of the calculations lies in demonstrating the need for conducting regular blood lead level screenings on children living in NSWC-IHDIV housing. Although a voluntary blood lead screening program exists at NSWC-IHDIV, medical personnel interviewed during the site visit indicated that participation in the program at the NSWC-IHDIV Medical Clinic is low.
Public Health Action Plan: Exposures to Residential Sources of Lead
Actions Taken and Proposed:
The Navy Public Works Center and NSWC-IHDIV have taken several actions to address the
problem of lead in the residential setting.
Educational outreach activities have been proposed by the NSWC-IHDIV medical personnel. These outreach efforts will include letters to military personnel entering base housing, and personal contacts with personnel already living in base housing, to inform them of the availability of blood lead level screening at NSWC-IHDIV. Blood lead screening for children who are six years of age and under, and women of child-bearing age, will be encouraged. These actions, planned as part of a continuing educational effort, will be initiated in July or August of 1997 (12).
Recommendations:
Because children at the NSWC-IHDIV can be exposed to lead from many sources, and the potential increase in blood lead levels from exposures to lead in only one of the possible exposures pathways exceeds the 10 µg/dL blood lead screening criterion, ATSDR recommends that the revised Lead Poisoning Prevention Plan for NSWC-IHDIV include the following components:
A. Mercury in Buildings 101 and 102
Summary: Spills of elemental mercury impacted general use (non-laboratory) areas of Buildings 101 and 102, potentially placing civilian employees in these buildings at risk of mercury exposure. Based on historical mercury vapor data and limited medical monitoring data, ATSDR has tentatively concluded that past mercury exposures may have occurred in Buildings 101 and 102 at levels of health concern. However, the potential past exposure for workers between 1981 and 1991 does not place these individuals at an increased risk for reproductive problems, nor is it likely to shorten their expected life spans. Any neurologic effects associated with chronic low-level exposure to the mercury vapor would have ended after exposure stopped and would not be evident today. ATSDR cannot eliminate the possibility, however, that the pre-1981 employees of these buildings were exposed at higher levels since no environmental or medical monitoring records are available for review. A summary of our evaluation of this situation is provided in Table 3.
Background: Buildings 101 and 102 were built in the early 1900s for propellant density and sensitivity testing: these tests incorporate the use of elemental mercury (13). Mercury spills and routine historical releases of mercury to building drains have been documented, affecting both laboratory and general use areas of the buildings (13). In the case of Building 102, for example, over 25 years elapsed between major mercury spills in the first floor laboratory in the early 1960s and the discovery of elemental mercury dripping from the first floor sub-flooring onto the basement coffee mess area (14, 15). Similarly, elemental mercury and elevated mercury vapors were discovered in a basement office area of Building 101 six years after mercury use had ceased in that building (16, 17). Both buildings are currently secured from entry and are included in the NSWC-IHDIV environmental program for future investigation and clean-up.
Based on the potential long history of uncontrolled mercury releases, the large volumes of mercury employed in these buildings, and the documented mercury contamination in general use areas of each building, ATSDR identified and evaluated three exposure situations with potential public health implications.
A.1. Past Exposure to Mercury in Buildings 101 and 102
NSWC-IHDIV instituted a medical monitoring program for mercury in 1983 and an industrial hygiene (air sampling) program for mercury in 1982. The spills of mercury in Buildings 101 and 102 represent uncontrolled sources of possible mercury exposure to workers who participated in the industrial hygiene and medical monitoring programs, but also to those people who worked in these buildings whose job did not involve use of mercury. In theory, these workers are not expected to be exposed to the hazardous substances in the workplace and are not typically included in the industrial hygiene and medical monitoring programs: this was the case at the NSWC-IHDIV for non-laboratory workers in Buildings 101 and 102. Therefore, outside of the
TABLE 3. Potential Public Health Hazard Situation: Mercury in Buildings 101 and 102
| PATHWAY NAME | CONTAMINANTS | EXPOSURE PATHWAYS ELEMENTS |
TIME |
COMMENTS | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
POTENTIALLY EXPOSED POPULATION |
||||
Past exposure to Mercury in Buildings 101 and 102 |
Mercury, as mercury vapor |
Elemental mercury spills |
Air, building materials (concrete, ceiling tiles, floorboards, drains, pipes, etc.) |
(I) Breathing (inhalation) of mercury vapor |
Inhalation |
Potentially Exposed: Past employees in Buildings 101 and 102 (estimate of employees in these buildings from 1960-1991 is approximately 78 individuals*) |
Past (approximately 1960 - 1991) |
Based on historical mercury vapor data and limited medical monitoring data, ATSDR has tentatively concluded that past mercury exposures may have occurred in these buildings at levels of health concern. This past potential exposure does not place these individuals at an increased risk for current health related effects. ATSDR cannot eliminate the possibility that pre-1981 employees of these buildings were exposed at higher levels because no environmental or medical records are available for review. |
* Estimate based on the assumption that 13-15 people worked in both buildings and stayed for a period of 4 to 5 years.
occupational exposures experienced by Building 101 and 102 personnel working with and around the mercury, all building personnel may have experienced additional exposures to uncontrolled mercury sources.
Because the mercury contamination was located primarily in wooden sub-flooring, ceiling tiles, and drain pipes, the primary route of potential exposure would have been inhalation of mercury vapors. Thus, our evaluation focused on whether past exposures to mercury vapor in these buildings are of potential health concern, particularly for those employees who were not participants in an occupational mercury monitoring program. Since these workers did not participate in a medical monitoring program, and their work areas were not included in the industrial hygiene environmental surveys, no information or data are available for review by ATSDR and NSWC-IHDIV for these employees. However, inferences about the potential for exposure to mercury vapor at concentrations of health concern can be drawn from the existing indoor air mercury vapor level data and the results of the occupational medical monitoring program for mercury.
The worker populations were divided into two groups for evaluation and discussion: (i) workers in Buildings 101 and 102 between 1981 and 1991, and (ii) workers in these buildings between 1960 and 1980. These groups were defined by the availability of environmental monitoring data from the buildings, availability of medical records for the workers, and estimates of the current ages of the employees. Environmental and medical records are available for 1981 through 1991, but pre-1981 records are extremely limited or not available. The 1960 cut-off date was established by calculating the current ages of past workers if they had been anywhere between 20 and 40 years of age during their employment in these buildings: these individuals would now be approximately 60 to 80 years of age.
Air Data Evaluation: ATSDR reviewed air monitoring data sets for Buildings 101 and 102 from 1978 through 1995. These data sets were typically generated by the base during the conduct of industrial hygiene surveys to evaluate the potential for occupational mercury exposure. In a few cases, the air data were collected in response to the discovery of previously spilled elemental mercury dripping from ceilings into general use areas of the buildings. The complete information on how the air sampling was conducted is not available for each data set; however, the bulk of the data were generated using direct read mercury vapor instrumentation (i.e. Bacharach Model MV-2 and Jerome Model 411).
The central nervous system is sensitive to exposures of inhaled metallic mercury vapor (18). To draw conclusions about the potential for worker exposure at levels of health concern, the mercury vapor data sets for NSWC-IHDIV were compared with a mercury vapor value of 0.03 milligrams per cubic meter (mg/m3). This concentration is at the low end of the range of concentrations at which chronic mercury vapor exposure may result in subtle health effects on the central nervous system (18).
Indoor Air Monitoring Data - Building 101: Indoor air mercury monitoring data from Building 101 is available for 1978 and 1983, 1990 through 1991, and 1995. These time intervals correspond to distinct periods of building use. During the years when mercury was used in the Building 101 laboratories (1978 and 1983 data), indoor mercury vapor concentrations ranged from 0.0019 to 0.015 mg/m3 (19, 20, 21). These data were collected from laboratory areas of the building: no data were found for the general use areas of the building where mercury vapors from uncontrolled releases may also have existed.
Between January 1990 and January 1991, the NSWC-IHDIV conducted extensive weekly air monitoring for mercury vapor in response to the discovery of beaded mercury on pipe insulation and elevated mercury concentrations in basement areas of the building (22). The entire building, including general use areas, was screened for mercury vapors. Although mercury use ceased in Building 101 in 1984 (16), mercury vapor levels persisted up to a maximum value of 0.021 mg/m3 in 1990-1991 (22). These data represent the mercury vapor concentrations to which these workers, who were not participants in a medical monitoring program, may have been exposed. Thus, during the time period between 1983 and 1991 when workers occupied Building 101, the data indicate that mercury vapor concentrations probably did not exceed the 0.03 mg/m3 concentration at which health effects may be observed due to chronic exposure (18).
A survey of the building in 1995 found mercury vapor concentrations ranging from 0.001 - 0.037 mg/m3 (23). This rise in concentrations likely resulted from lack of ventilation because the building was closed in 1994. Although the maximum mercury vapor value detected exceeds 0.03 mg/m3, the building is currently unoccupied and there is no route exists for worker exposure to these vapors.
Indoor Air Monitoring - Building 102: Building 102 air monitoring data are available for two time periods: 1978 -1983 and 1987 -1989. In 1978 -1983, mercury vapor levels ranged from 0 to 0.04 mg/m3, surging up to 0.08 mg/m3 when mercury was cleaned from laboratory instrumentation with acid: the median mercury vapor value was 0.005 mg/m3 (14, 19, 20, 24). These mercury vapor readings were collected from laboratory and office areas: no general use areas appear to have been monitored. The workers who conducted the laboratory activities using mercury would have been participants in a medical monitoring program and over-exposures to mercury should have been revealed in the course of physical exams and biological testing. Other building employees would not have been expected to be exposed to these sources and levels of mercury.
Surveys were conducted in 1987 after the discovery of elemental mercury dripping from the first floor sub-flooring onto the basement coffee mess area. These survey data were generally reported as "well below 0.05 mg/m3" (15, 25) and the survey included the room where elemental mercury was discovered and adjacent rooms in the building. Data collected in 1989 did not exceed 0.0036 mg/m3 (26). Building 102 was closed in 1989. Overall, the data do not suggest levels of mercury vapor at concentrations associated with health effects (18). However, it is important to note that the air data were collected after the dripping mercury had been noticed and cleaned from the general use area: no data are available that represent the mercury vapor concentrations to which workers were exposed to during the release of mercury to the coffee mess area.
Medical Monitoring Data- Building 101 and 102 Workers: The physical exam and biological (urine) evaluations for 4 of the approximately 20 medically monitored employees who worked in these buildings between 1981 and 1991 were provided to ATSDR. These results indicate that none of the employees in the mercury medical monitoring program, for whom records have currently been retrieved, were exposed to mercury at levels of health concern. These results suggest that other participants in the monitoring program, as well the people who did not work with mercury and may be presumed to have had lower exposures, did not experience exposure to mercury at levels of health concern between 1981 and 1991 in Building 101. However, the incomplete medical monitoring data for the occupational population, and the lack of medical monitoring data for the non-occupational population, introduces considerable uncertainty into this evaluation.
No pre-1978 air monitoring data or pre-1981 medical monitoring data have been retrieved from NSWC-IHDIV files for Buildings 101 and 102. It is reasonable to assume that indoor air mercury vapor levels in the buildings may have been higher in the past when the mercury spills were recent and vaporization rates would have been higher. This scenario would be particularly likely in the basement areas of the buildings after the installation of impervious first floor coverings over contaminated sub-flooring in both buildings (mid-1960s through the early 1970s). Thus, ATSDR cannot eliminate the possibility that pre-1981 employees of Buildings 101 and 102 were exposed to the occupational and non-occupational mercury sources at levels of health concern.
Health Implications: Available air monitoring data do not suggest that workers in Buildings 101 and 102 were exposed to chronic high levels of mercury vapor. Thus, permanent effects of mercury exposure on the central nervous system and kidneys, which occur at chronic high doses, would not be expected.
At low doses of inhaled elemental mercury, the body is generally able to metabolize and excrete the mercury in the urine, feces, saliva and sweat (27). Early signs of mercury toxicity due to chronic mercury vapor exposure may be observed as subtle neurologic effects, including fine tremors in the fingers, lips, and eyelids, effects on precision movements such as handwriting, headache, and short-term memory loss (28). These symptoms tend to disappear, however, when the exposure is stopped (27). In addition, studies on occupationally exposed workers indicate that neither reproductive problems (29), nor decreases in life span (30), are associated with mercury vapor exposure.
The biologic half-life of inhaled elemental mercury in the human body is about 60 days (27). Thus mercury may be expected to be reduced to concentrations that are not distinguishable from the background levels of mercury in the body within one year after exposure to the mercury source ends. Since exposures to the mercury ceased no later than 1989 in Building 102 and 1991 in Building 101, no building-related mercury should persist in the bodies of individuals who worked in these buildings through this time period. Accordingly, no biological testing could be performed today to reveal whether these individuals had been exposed in the past to mercury from Buildings 101 and 102.
Public Health Action Plan: Past Exposures to Mercury in Buildings 101 and 102
Conclusions:
Recommendations:
A.2. Potential for "Take Home" Mercury Contamination
The National Institute for Occupational Safety and Health (NIOSH) has examined the potential for the transport of hazardous substances from the workplace to the home. This "take home" contamination has been demonstrated to be a worldwide public health issue for workers, resulting in a wide range of contaminant-specific health effects (31). Industrial hygiene programs, including the program currently in place at the NSWC-IHDIV, are designed to prevent take home contamination by workers who work with hazardous chemicals.
Chemicals such as mercury may be transported into the home unknowingly on work clothes and shoes, or deliberately by persons who are unaware of the hazards of workplace chemicals. Mercury contamination in the home can result in exposures to children and adult residents to vapors at concentrations of health concern. For residential properties, and for populations of people who may be more sensitive to chemical exposures such as young children and women of child-bearing years, ATSDR recommends that mercury vapor concentrations in indoor air not exceed 0.0003 mg/m3 (32) in order to protect human health.
NIOSH has reviewed situations where exposure to mercury in the workplace has resulted in home contamination (32). For example, mercury vapor concentrations in the range of 0.024 - 0.3 mg/m3 were measured in the air of homes of thermometer manufacturing plant workers. Analyses of urine samples provided evidence of exposure to mercury in the home: concentrations of mercury in the urine of exposed children from these worker-contaminated homes were up to 5 times the concentrations measured in urine of unexposed children (31).
ATSDR believes that the historical mercury contamination situation in Buildings 101 and 102 presents a potential for past tracking of mercury from these buildings into the homes of workers. Observations which support this concern include: (i) the long history of mercury use in large quantities in both buildings; (ii) the documented spills and routine releases of mercury that resulted in contamination of the buildings; (iii) the undefined extent of mercury contamination in these buildings; (iv) the period of time between 1960 and 1980 when mercury contamination was present pre-dates the establishment of the base program for medical monitoring for mercury and environmental monitoring for worker exposure; (v) only limited medical monitoring data have been located for the 1980-91 time period; and, (vi) building common areas are generally not represented in the mercury vapor screening data sets for these buildings.
Taken together, these elements strongly suggest the opportunity for past workers in the building to come into contact with mercury contamination under conditions where it could be picked up on clothes and shoes unintentionally, or deliberately by a building employee not aware of the hazard, and tracked into the home. ATSDR's concern lies in the potential for current residents of these homes to experience on-going inhalation exposures to mercury vapors. Adults and children exposed to chronic low levels of mercury vapor may develop nervous system effects including fine tremors in the fingers, lips and eyelids, and effects on precision movements such as handwriting. Headaches and difficulties with short-term memory may also occur (28). In general, individuals with diseases of the liver, kidney, lung, and nerves are considered to be at greater risk of suffering from the toxic effects of mercury than individuals in good general health. Inhaled metallic mercury can reach the fetuses of pregnant women and can also be metabolized (changed) in the body into mercuric chloride (18) . Mercuric chloride is capable of entering the bloodstream and may be passed though mother's milk to breast-feeding infants. These pre-birth and post-birth exposures place these children at risk for nervous system development problems (18). Additional information about exposures to mercury in the environment is provided in the ATSDR Public Health Statement which is provided in Appendix E of this public health assessment.
Public Health Action Plan: "Take Home" Mercury Contamination
Conclusion:
Recommendation:
If the implementation of this recommendation is outside the appropriate scope of IHDIV-NSWC responsibilities and resources, ATSDR possesses the capability to coordinate with NSWC and perform the residential screenings in support of public health activities at the base.
A.3. Future Use of Buildings 101 and 102
No mercury clean-ups have been performed in Buildings 101 and 102. The mercury contaminated area of Building 101 was closed in response to the discovery of elevated mercury vapors and remains secured from entry and posted with a warning sign. This building is currently unoccupied. Building 102 was closed in 1989 and remains secured from entry. The extent of contamination is currently unknown but will be determined during Remedial Investigation (RI) activities. However, neither building is currently scheduled as a priority (relative to the other areas of the base that present a greater threat to public health or the environment, or impact a military construction project) for RI characterization and clean-up activities. Mercury vapors persist at detectable concentrations in areas of both buildings at concentrations as high as 0.03 mg/m3: this concentration exceeds the ATSDR Minimal Risk Level and EPA's Reference Concentration for mercury vapor. Therefore, indoor air levels of mercury in these buildings exceed acceptable levels that are protective of public health.
ATSDR was concerned that indoor air concentrations could increase in response to future building uses that disturb the mercury, including renovation activities, before completion of clean-up activities. However, during the course of the public health assessment, the NSWC Safety department determined that use of Buildings 101 and 102 will not be permitted until the mercury within the buildings has been remediated (10). Preventing use of the buildings eliminates the exposure pathway to the mercury vapors and ATSDR's public health concern.
B. Fish in Mattawoman and Chicamuxen Creeks
Summary: Concentrations of cadmium, mercury, and zinc in Mattawoman Creek fish tissue do not pose a threat to public health through ingestion. However, to protect people eating fish, sampling and analysis for lead, silver, chromium, and copper should be performed to determine if these metals are entering the food chain in Mattawoman and Chicamuxen Creeks and bioaccumulating to concentrations requiring consumption limits. A summary of our evaluation of this situation is provided in Tables 4a and 4b.
Background: Studies conducted by the U.S. Fish and Wildlife Service provide data on levels of mercury, cadmium, and zinc in selected fish and shellfish collected from Mattawoman Creek (Figure 1) between 1987 and 1991 (33, 34). Overall, the concentrations of these metals in Mattawoman Creek fish tissue ranged from below to slightly above levels documented in similar monitoring programs in Potomac River, Maryland, and U.S. studies (34). ATSDR evaluated these data using the chemical-specific Risk-Based Concentration (RBC) values for fish tissue(35). U.S. EPA's RBCs are useful data-screening tools that assume exposure to only one contaminant and hold the risk to exposed individuals at highly conservative (protective) levels. The fish data and RBC screening values are provided in Table 5.
Cadmium was not detected in whole fish tissue samples above the detection limit (0.1 milligrams per kilogram [mg/kg]), which is well below the RBC for that metal (0.68 mg/kg). Mercury concentrations were also below the RBC (0.41 mg/kg), ranging from undetected to 0.37 mg/kg. Similarly, maximum zinc concentrations in tissue samples from six species of fish and the brackish water clam ranged from 14 to 55 mg/kg. These values are 7 to 29 times lower than the RBC for zinc (410 mg/kg).
Using available data, we conclude that the 1991 concentrations of cadmium, mercury, and zinc in Mattawoman Creek fish and shellfish do not pose a public health threat through ingestion. In each case, the concentrations of these chemicals in whole fish tissue were below the RBC screening value. Although only five (5) fish of each species were collected and analyzed, the amount of contaminant to which an individual would normally be exposed in the edible portion of the fish would be less than the whole fish concentrations reported in Table 5. Consumption of fish caught from these creeks is not a health concern.
Other chemical contaminants from the NSWC-IHDIV have also impacted the surrounding sediments: lead, silver, chromium and copper are documented to occur in Mattawoman Creek sediments at elevated concentrations relative to background and Chesapeake Bay reference sites (33). These chemicals may bioaccumulate in certain species of fish. However, because these chemicals were not included in the fish tissue analyses that have been conducted, it is not known whether they are entering the food chain in Mattawoman and Chicamuxen Creeks and bioaccumulating. The U.S. Fish and Wildlife Service has recommended that additional fish tissue analyses be performed and that the concentrations of selected chemicals in the base's discharges be reduced (33).
TABLE 4a. No Apparent Public Health Hazard Situation: Fish Consumption
| PATHWAY NAME | CONTAMINANTS | EXPOSURE PATHWAYS ELEMENTS |
TIME |
COMMENTS | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
POTENTIALLY EXPOSED POPULATION |
||||
|
Contaminated fish in Mattawoman and Chicamuxen Creeks |
Mercury, zinc, cadmium |
Releases of hazardous substances to soils and shallow groundwater at the site, and historical discharges of munitions process waste waters to the creeks |
Fish |
Eating (ingestion of ) contaminated fish |
Ingestion |
Potentially Exposed: people who eat contaminated fish from the creeks |
Future |
No apparent health hazard is posed by the metals contaminants to people eating fish caught from the creeks. Concentrations are below levels of health concern |
TABLE 4b. Potential Public Health Hazard Situation: Fish Consumption
| PATHWAY NAME | CONTAMINANTS | EXPOSURE PATHWAYS ELEMENTS |
TIME |
COMMENTS | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
POTENTIALLY EXPOSED POPULATION |
||||
|
Contaminated fish in Mattawoman and Chicamuxen Creeks |
Lead, silver, chromium, copper |
Releases of hazardous substances to soils and shallow groundwater at the site, and historical discharges of munitions process waste waters to the creeks |
Fish |
Eating (ingestion of) contaminated fish |
Ingestion |
Potentially Exposed: people who eat contaminated fish from the creeks |
|
Future sampling should also include tissue analyses for lead, silver, chromium, and copper to determine if these metals are bioaccumulating to concentrations of public health concern. |
| Species | Mercury | Cadmiume | Zinc |
| Channel Catfish | 0.068 | < 0.1 | 55 |
| Largemouth Bass | 0.370 | < 0.1 | NAf |
| Bluegill | 0.078 | < 0.1 | NA |
| Gizzard Shad | 0.034 | < 0.1 | 14 |
| Brown Bullhead | 0.072 | < 0.1 | 14 |
| White Perch | 0.072 | < 0.1 | 38 |
| Black Crappie | NDg | < 0.1 | 7.9 |
| Spot | 0.035 | < 0.1 | 18 |
| Brackish Water Clam | 0.025 | < 0.1 | 17 |
| Risk-Based Concentration (RBC) screening value |
0.41 | 0.68 | 410 |
Note: mercury, cadmium, and zinc were chosen by the U.S. Fish and Wildlife Service for analysis in tissue samples based on records of maximum discharge concentrations from NSWC-IHDIV and chemical-specific bio-concentration factors in the literature (Reference 33).
a determinations were made on whole body fish samples.
b mg/kg WW: data and RBC values are expressed in units of mg metal per kilogram wet weight of fish tissue.
c fish tissue data are summarized from References 33 and 34.
d U.S. EPA Region III Risk Based Concentration values are derived from Reference 35.
e detection limit for cadmium analysis: 0.1 mg/kg WW.
f NA: data not available.
g ND: chemical not detected.
Public Health Action Plan: Fish in Mattawoman and Chicamuxen Creeks
Conclusions:
Actions Taken or Proposed:
Recommendations:
Mattawoman Creek supports significant recreational and limited commercial fishing activity. However, Remedial Investigation studies at NSWC and RCRA Corrective Action investigations at the Stump Neck Annex do not currently include sampling activities to monitor possible future food chain contamination in Mattawoman and Chicamuxen Creeks (3, 4). Therefore, ATSDR makes the following recommendations:
Both sampling recommendations will permit NSWC-IHDIV to determine whether metals in the water and sediments are bioaccumulating in fish to concentrations requiring consumption limits to protect public health. In the event that such sampling is proposed, ATSDR requests involvement in the review of the Work Plan for those activities in order to ensure that the proposed sampling and analyses will generate the type and quality of data needed to draw conclusions about potential human health impacts.
III. No Public Health Hazard: Drinking Water Supply - Patapsco and Patuxent Aquifers
Summary: NSWC-IHDIV is implementing a wellhead protection program to ensure that the groundwater wells at the base do not serve, in the future, as conduits for the migration of shallow contaminated groundwater to the deeper aquifers. This plan is needed to ensure protection of the deep groundwater resources that serve as the drinking water supply for the base and the region. A summary of our evaluation of this situation is provided in Table 6.
Background: Past activities at the NSWC and Stump Neck Annex of NSWC-IHDIV resulted in the release of chemical contaminants to soils and shallow groundwater at IRP and RCRA sites located throughout the facility (3, 5, 3). This shallow groundwater contamination does not currently pose a public health threat: drinking water supplies for the NSWC-IHDIV and the majority of the surrounding community are obtained from the deep Patapsco and Patuxent groundwater aquifers. These aquifers are separated from the contaminated surface soils and shallow groundwater by deposits of low-permeability materials (e.g., clay, silty clays) (13). Off-base deep wells, as well the shallow wells which exist in some areas around the Stump Neck Annex, lie upgradient from the contaminated areas at the base. These off-base private wells are not threatened by the shallow groundwater contamination at the facility which flows toward, and discharges to, the river and Mattawoman and Chicamuxen creeks.
Older wells with deteriorated casings, and out-of-service wells not abandoned in accordance with current groundwater protection standards, may serve as conduits for migration of chemical contaminants to the deeper groundwater resources. This potential situation exists at NSWC-IHDIV. The majority of the wells are older, dating back to 1945 at the Stump Neck Annex and to the early 1900s on the Cornwallis Neck peninsula (5). In addition, NSWC-IHDIV is experiencing problems with lowered water tables and saline water intrusion related to increased regional water demands (3, 36, 37). Lowered water tables, saline water intrusion and the potential for chemical contamination of the deeper aquifer are inter-related phenomena. In the same way that increased groundwater pumping rates and volume will lower water tables and permit the infiltration of saline water into the freshwater aquifer, the reduction of pressure exerted by the deep aquifer in the well casings increases the possibility of downward migration of chemically contaminated shallow groundwaters.
Public Health Action Plan: Drinking Water Supply - Patapsco and Patuxent Aquifers
Conclusion
Actions Taken and Planned
Recommendations
TABLE 6. No Public Health Hazard: Drinking Water Supply
| PATHWAY NAME | CONTAMINANTS | EXPOSURE PATHWAYS ELEMENTS |
TIME |
COMMENTS | ||||
| SOURCE | ENVIRONMENTAL MEDIA |
POINT OF EXPOSURE |
ROUTE OF EXPOSURE |
POTENTIALLY EXPOSED POPULATION |
||||
|
Drinking Water Supply - Patapsco and Patuxent Aquifers |
Solvents, mercury, silver, lead, other metals, nitrate esters |
Historical releases of hazardous substances to soils and shallow groundwater at sites located throughout the base |
Soils, shallow groundwater |
NSWC-IHDIV drinking water supply system |
Water supply wells that (i) are aged (dating to early 1900s) (ii) are improperly abandoned (iii) are out of service but not abandoned, or (iv) cannot be located, potentially serving as conduits for shallow groundwater contaminant migration to the deeper supply aquifer |
Potentially Exposed: residents, employees at NSWC-IHDIV |
Future |
To date, water well sampling does not indicate contamination of the deeper aquifer by the shallow contaminated groundwaters. The on-going development and implementation of a wellhead protection program by NSWC-IHDIV should prevent possible future exposure. |
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