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
Based on the results of our site visit, and a review of the data and information currentlyavailable, we conclude that one exposure situation at NSWC-IHDIV currently poses a publichealth threat. Exposures to lead in the Navy housing are occurring at concentrations that maycause adverse health effects. In addition, two potential situations are identified in whichexposures may have occurred in the past or could occur in the future to contaminant levels ofhealth concern. A fourth situation does not pose a public heath concern because the base hastaken action to reduce the chances of exposure to the chemical contaminants.
Table 1 summarizes ATSDR's public health conclusions for the exposure situations identifiedat NSWC-IHDIV, and a detailed discussion of each situation. Additional information describingATSDR's public health conclusion categories is provided in Appendix C.
|Public Health Hazard||Exposure to Residential Sources of Lead|
|Potential Health Hazards||Exposure to Mercury in Buildings 101 and102 |
Fish in Mattawoman and ChicamuxenCreeks
|No Public Health Hazard||Drinking Water Supply-Patapsco andPatuxent Aquifers|
Summary: The lead in exterior and interior paints, foundation soils, and household dusts, atNSWC-IHDIV housing poses a health hazard to residents, particularly children 6 years of ageand under and women of child-bearing age. Calculations using lead data from foundation soilsdemonstrate the potential for blood lead levels of resident children to increase above the CDCpublic health standard of 10 micrograms per deciliter (µg/dL). The base should take action toimprove 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 leadlevels meet or exceed 10 µg/dL. A summary of our evaluation of this situation is provided inTable 2.
Background: NSWC-IHDIV currently maintains housing on the base (the Detached singlefamily housing and the Riverview Village apartments). Off-base housing in the nearby townsof La Plata and Waldorf was taken out of service in 1997. Additional Detached housing at theStump Neck Annex was taken out of service in November of 1996. The housing ranges in agefrom approximately 30 to 80 years and has been identified by NSWC-IHDIV as a source ofresidential 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 UnitedStates 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 sourcesinclude lead-contaminated paint chips, household dusts, and foundation soils (soils locatednear the base of the buildings). In 1991-1992, the Navy Public Works Center/Norfolk sampledthe interior paint, household dusts, exterior paint, and foundation soils at each of the housinglocations. 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 leadat 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 aresidential setting, ingestion and inhalation of lead from multiple sources in a child'senvironment may result in exposures that pose a potential health hazard.
The Centers for Disease Control and Prevention (CDC) recommends that all children bescreened for lead poisoning at least annually, especially children between the ages of 6months and 6 years of age (9). Young children and fetuses are most vulnerable to lead toxicityfor 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 bodyweight 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 10-40micrograms per deciliter (µg/dL) may not cause distinctive symptoms of lead poisoning, but areassociated with impaired central nervous system development, lower IQs, and hearingproblems in children (7,9).
Based on the toxicity of lead at low concentrations in the blood, the CDC recommends thatchildren's blood lead levels fall below 10 µg/dL (9). Historically, NSWC maintained no databaseof past blood lead testing results which could be reviewed by ATSDR during the public healthassessment. However, blood lead tests conducted by the base in 1991 demonstrated that allchildren (6 months to 6 years of age) living in the Detached housing units tested positive forlead, 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 agoand is limited to only a subset of the children living on the base in 1991. During the publichealth assessment, NSWC provided additional blood lead data obtained in 1997 through their
|PATHWAY NAME||CONTAMINANTS||EXPOSURE PATHWAYS ELEMENTS|
Lead-Based Paint inDetached,Riverview, Waldorf,and La Plata Navyresidential housing
Flaking anddeteriorating lead-based paint oninterior and exteriorsurfaces of on-baseand off-base Navyresidential housing
(I) Lead-contaminatedhousehold dusts
(Ii) lead-contaminated painted surfaces
(Ii) lead-contaminated paint chips, soils
(of lead-contaminated dusts)
Children residents(particularly ages 6 andunder; approximately65 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*)
Calculations assumingexposure to NSWC-IHDIVresidential foundation soil leadconcentrations demonstratepotential increases in childblood lead levels above theCDC public health standard of
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 theDetached (one child) and Riverview (four children) housing demonstrate that these fivechildren have not been exposed to lead at levels of health concern. Blood lead concentrationsin 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 and3.4 µg/dL, respectively (7, 11).
Since the housing inspection results indicate that the children living in NSWC-IHDIV housingare at high risk for lead exposure, historical annual screening data and limited current bloodlead data are available for these children, ATSDR evaluated the potential for blood lead levelsof 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 bloodlead levels to concentrations of lead in soils, to estimate the potential for blood lead levels toexceed 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 thechildren in residence at the NSWC-IHDIV. Calculated increases in blood lead levels rangedfrom 7.1 (Riverview Village apartments) to 23.5 (Detached housing) µg/dL. Adding thesevalues to the baseline blood lead concentrations for U.S. children (noted above), one arrives atpredicted blood lead levels ranging from approximately 11 to 27 µg/dL for children living inNSWC-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 bloodlead levels which exceed the 10 µg/dL screening criterion.
These calculations may overestimate potential increases in blood lead levels by assumingregular 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 theNSWC-IHDIV residential setting. The value of the calculations lies in demonstrating the needfor 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 personnelinterviewed during the site visit indicated that participation in the program at the NSWC-IHDIVMedical Clinic is low.
Actions Taken and Proposed:
The Navy Public Works Center and NSWC-IHDIV have taken several actions to address theproblem of lead in the residential setting.
- NSWC-IHDIV medical personnel are currently reviewing the existing Navy PediatricLead Poisoning Prevention Screening Plan to determine how to adapt this plan toaddress the specific residential lead exposure situation at the base.
Educational outreach activities have been proposed by the NSWC-IHDIV medicalpersonnel. These outreach efforts will include letters to military personnel enteringbase housing, and personal contacts with personnel already living in base housing, toinform them of the availability of blood lead level screening at NSWC-IHDIV. Bloodlead 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 continuingeducational effort, will be initiated in July or August of 1997 (12).
- In 1996, external lead risk-reduction activities (encapsulation) were initiated for theDetached housing and associated garages with external lead paint contamination. These activities will continue through 1997. However, risk-reduction activities for leadin foundation soils and abatement of lead in the interior of the housing units have notbeen initiated or scheduled. Execution of these activities at NSWC-IHDIV will dependon the Navy Public Works Center plan to perform abatement using a "worst-first"approach, and where the NSWC-IHDIV is ranked relative to other Navy bases with leadproblems (12). Funding for interior lead-based paint activities at the base has beenapprove (10).
- Incoming residents are notified of the presence of lead in the housing per HUD requirements and given the option to live elsewhere. In addition, educational literatureon the sources and health effects of lead are provided to the new residents. "Ledizolv",a lead-specific cleaning agent, is available from Housing upon request (10).
- Family Housing has purchased a high efficiency filter vacuum and will schedulecleaning of window sills, areas around radiators, and other areas where paint chippingexists in the homes (10).
Because children at the NSWC-IHDIV can be exposed to lead from many sources, and thepotential increase in blood lead levels from exposures to lead in only one of the possibleexposures pathways exceeds the 10 µg/dL blood lead screening criterion, ATSDRrecommends that the revised Lead Poisoning Prevention Plan for NSWC-IHDIV include thefollowing components:
- The plan should integrate the activities of Primary Care and Housing, and the Bethesda lab. The program should coordinate education efforts, provision of blood lead tests, tracking of blood lead results, feedback to the residents, and a plan of action in the event that blood lead levels of health concern are identified.
- The program should focus on children through 6 years of age with a goal of 100% voluntary participation.
- Parents of dependents who participate in blood lead screening at military medical facilities other than the NSWC-IHDIV Clinic should be urged to share the results of those tests with NSWC-IHDIV Housing or Primary Care.
- The blood lead screening program should continue until abatement or risk reduction activities have been completed and subsequent screening shows blood lead levels to be below levels of public health concern, or the housing is vacated.
- NSWC-IHDIV should consider establishing baseline lead levels for the dependents of base residents upon acceptance into Navy housing. These baselines provide the data necessary for interpreting subsequent blood lead screening data.
- Application of the algorithm demonstrated that the average soil concentration for eachunit of Detached housing was high enough to drive the predicted blood lead levelsabove the public health criterion of 10 µg/dL. Considering this information and themultiple pathways of exposure to lead in this older housing area, ATSDR recommendsthat screening efforts focus early on children in Detached housing and that this housingreceive early action for any proposed lead abatement or risk reduction activitiesaddressing lead in soil and interior paint sources.
Summary: Spills of elemental mercury impacted general use (non-laboratory) areas ofBuildings 101 and 102, potentially placing civilian employees in these buildings at risk ofmercury exposure. Based on historical mercury vapor data and limited medical monitoringdata, ATSDR has tentatively concluded that past mercury exposures may have occurred inBuildings 101 and 102 at levels of health concern. However, the potential past exposure forworkers between 1981 and 1991 does not place these individuals at an increased risk forreproductive problems, nor is it likely to shorten their expected life spans. Any neurologiceffects associated with chronic low-level exposure to the mercury vapor would have endedafter exposure stopped and would not be evident today. ATSDR cannot eliminate thepossibility, however, that the pre-1981 employees of these buildings were exposed at higherlevels 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 andsensitivity testing: these tests incorporate the use of elemental mercury (13). Mercury spills androutine historical releases of mercury to building drains have been documented, affecting bothlaboratory and general use areas of the buildings (13). In the case of Building 102, forexample, over 25 years elapsed between major mercury spills in the first floor laboratory in theearly 1960s and the discovery of elemental mercury dripping from the first floor sub-flooringonto the basement coffee mess area (14, 15). Similarly, elemental mercury and elevated mercuryvapors were discovered in a basement office area of Building 101 six years after mercury usehad ceased in that building (16, 17). Both buildings are currently secured from entry and areincluded 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 ofmercury employed in these buildings, and the documented mercury contamination in generaluse areas of each building, ATSDR identified and evaluated three exposure situations withpotential public health implications.
NSWC-IHDIV instituted a medical monitoring program for mercury in 1983 and an industrialhygiene (air sampling) program for mercury in 1982. The spills of mercury in Buildings 101and 102 represent uncontrolled sources of possible mercury exposure to workers whoparticipated in the industrial hygiene and medical monitoring programs, but also to thosepeople 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 workplaceand are not typically included in the industrial hygiene and medical monitoring programs: thiswas the case at the NSWC-IHDIV for non-laboratory workers in Buildings 101 and 102. Therefore, outside of the
|PATHWAY NAME||CONTAMINANTS||EXPOSURE PATHWAYS ELEMENTS|
Past exposure to Mercury inBuildings 101 and102
Mercury, asmercury vapor
building materials(concrete, ceilingtiles, floorboards,drains, pipes, etc.)
(I) Breathing(inhalation) ofmercury vapor
Past employees inBuildings 101 and 102(estimate ofemployees in thesebuildings from 1960-1991 is approximately78 individuals*)
(approximately1960 - 1991)
Based on historical mercury vapordata and limited medical monitoringdata, ATSDR has tentativelyconcluded that past mercuryexposures may have occurred inthese buildings at levels of healthconcern. This past potentialexposure does not place theseindividuals at an increased risk forcurrent 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 andaround the mercury, all building personnel may have experienced additional exposures touncontrolled 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 mercuryvapors. Thus, our evaluation focused on whether past exposures to mercury vapor in thesebuildings are of potential health concern, particularly for those employees who were notparticipants in an occupational mercury monitoring program. Since these workers did notparticipate in a medical monitoring program, and their work areas were not included in theindustrial hygiene environmental surveys, no information or data are available for review byATSDR and NSWC-IHDIV for these employees. However, inferences about the potential forexposure to mercury vapor at concentrations of health concern can be drawn from the existingindoor air mercury vapor level data and the results of the occupational medical monitoringprogram for mercury.
The worker populations were divided into two groups for evaluation and discussion: (i) workersin Buildings 101 and 102 between 1981 and 1991, and (ii) workers in these buildings between1960 and 1980. These groups were defined by the availability of environmental monitoringdata from the buildings, availability of medical records for the workers, and estimates of thecurrent ages of the employees. Environmental and medical records are available for 1981through 1991, but pre-1981 records are extremely limited or not available. The 1960 cut-offdate was established by calculating the current ages of past workers if they had beenanywhere between 20 and 40 years of age during their employment in these buildings: theseindividuals would now be approximately 60 to 80 years of age.
Air Data Evaluation: ATSDR reviewed air monitoring data sets for Buildings 101 and 102 from1978 through 1995. These data sets were typically generated by the base during the conductof industrial hygiene surveys to evaluate the potential for occupational mercury exposure. In afew cases, the air data were collected in response to the discovery of previously spilledelemental mercury dripping from ceilings into general use areas of the buildings. Thecomplete information on how the air sampling was conducted is not available for each dataset; however, the bulk of the data were generated using direct read mercury vaporinstrumentation (i.e. Bacharach Model MV-2 and Jerome Model 411).
The central nervous system is sensitive to exposures of inhaled metallic mercury vapor (18). Todraw conclusions about the potential for worker exposure at levels of health concern, themercury vapor data sets for NSWC-IHDIV were compared with a mercury vapor value of 0.03milligrams per cubic meter (mg/m3). This concentration is at the low end of the range ofconcentrations at which chronic mercury vapor exposure may result in subtle health effects onthe central nervous system (18).
Indoor Air Monitoring Data - Building 101: Indoor air mercury monitoring data from Building101 is available for 1978 and 1983, 1990 through 1991, and 1995. These time intervalscorrespond to distinct periods of building use. During the years when mercury was used in theBuilding 101 laboratories (1978 and 1983 data), indoor mercury vapor concentrations rangedfrom 0.0019 to 0.015 mg/m3 (19, 20, 21). These data were collected from laboratory areas of thebuilding: no data were found for the general use areas of the building where mercury vaporsfrom uncontrolled releases may also have existed.
Between January 1990 and January 1991, the NSWC-IHDIV conducted extensive weekly airmonitoring for mercury vapor in response to the discovery of beaded mercury on pipeinsulation and elevated mercury concentrations in basement areas of the building (22). Theentire building, including general use areas, was screened for mercury vapors. Althoughmercury use ceased in Building 101 in 1984 (16), mercury vapor levels persisted up to amaximum value of 0.021 mg/m3 in 1990-1991 (22). These data represent the mercury vaporconcentrations to which these workers, who were not participants in a medical monitoringprogram, may have been exposed. Thus, during the time period between 1983 and 1991when workers occupied Building 101, the data indicate that mercury vapor concentrationsprobably did not exceed the 0.03 mg/m3 concentration at which health effects may beobserved 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 thebuilding was closed in 1994. Although the maximum mercury vapor value detected exceeds0.03 mg/m3, the building is currently unoccupied and there is no route exists for workerexposure to these vapors.
Indoor Air Monitoring - Building 102: Building 102 air monitoring data are available for two timeperiods: 1978 -1983 and 1987 -1989. In 1978 -1983, mercury vapor levels ranged from 0 to0.04 mg/m3, surging up to 0.08 mg/m3 when mercury was cleaned from laboratoryinstrumentation 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 useareas appear to have been monitored. The workers who conducted the laboratory activitiesusing 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 andbiological testing. Other building employees would not have been expected to be exposed tothese sources and levels of mercury.
Surveys were conducted in 1987 after the discovery of elemental mercury dripping from thefirst floor sub-flooring onto the basement coffee mess area. These survey data were generallyreported as "well below 0.05 mg/m3" (15, 25) and the survey included the room where elementalmercury was discovered and adjacent rooms in the building. Data collected in 1989 did notexceed 0.0036 mg/m3 (26). Building 102 was closed in 1989. Overall, the data do not suggestlevels of mercury vapor at concentrations associated with health effects (18). However, it isimportant to note that the air data were collected after the dripping mercury had been noticedand 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 coffeemess 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 workedin these buildings between 1981 and 1991 were provided to ATSDR. These results indicatethat none of the employees in the mercury medical monitoring program, for whom recordshave currently been retrieved, were exposed to mercury at levels of health concern. Theseresults suggest that other participants in the monitoring program, as well the people who didnot work with mercury and may be presumed to have had lower exposures, did not experienceexposure to mercury at levels of health concern between 1981 and 1991 in Building 101. However, the incomplete medical monitoring data for the occupational population, andthe lack of medical monitoring data for the non-occupational population, introducesconsiderable uncertainty into this evaluation.
No pre-1978 air monitoring data or pre-1981 medical monitoring data have been retrieved fromNSWC-IHDIV files for Buildings 101 and 102. It is reasonable to assume that indoor airmercury 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 beparticularly likely in the basement areas of the buildings after the installation of impervious firstfloor coverings over contaminated sub-flooring in both buildings (mid-1960s through the early1970s). Thus, ATSDR cannot eliminate the possibility that pre-1981 employees of Buildings101 and 102 were exposed to the occupational and non-occupational mercury sources atlevels of health concern.
Health Implications: Available air monitoring data do not suggest that workers in Buildings 101and 102 were exposed to chronic high levels of mercury vapor. Thus, permanent effects ofmercury exposure on the central nervous system and kidneys, which occur at chronic highdoses, would not be expected.
At low doses of inhaled elemental mercury, the body is generally able to metabolize andexcrete the mercury in the urine, feces, saliva and sweat (27). Early signs of mercury toxicitydue 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 ashandwriting, headache, and short-term memory loss (28). These symptoms tend to disappear,however, when the exposure is stopped (27). In addition, studies on occupationally exposedworkers indicate that neither reproductive problems (29), nor decreases in life span (30), areassociated 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 distinguishablefrom the background levels of mercury in the body within one year after exposure to themercury source ends. Since exposures to the mercury ceased no later than 1989 in Building102 and 1991 in Building 101, no building-related mercury should persist in the bodies of individualswho worked in these buildings through this time period. Accordingly, no biological testingcould be performed today to reveal whether these individuals had been exposed in the past tomercury from Buildings 101 and 102.
- Based on historical indoor air screening data, the history of uncontrolled mercury spills, and incomplete (1981-1991) or unavailable (prior to 1981) medical monitoring data for these employees, ATSDR concludes that mercury exposures may have occurred in the past in Buildings 101 and 102 at levels of public health concern. However, for people who worked in these buildings, their potential past exposure 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 ceased and would not be evident today.
- However, because no environmental or medical monitoring records are available for review, ATSDR cannot eliminate the possibility that pre-1981 employees of these buildings were exposed at higher levels.
- The populations of primary concern include (i) those individuals who worked in thesebuildings prior to 1981 (regardless of job duty) and (ii) those individuals who worked inthese buildings from 1981 or beyond and were not participants in the occupationalmercury medical monitoring program.
- ATSDR needs additional data and information to complete our evaluation of potentialpast exposures to mercury in Buildings 101 and 102. ATSDR and NSWC-IHDIV areworking together to obtain and evaluate records from any past mercury-related medicalsurveillance activities conducted by NSWC-IHDIV for employees working in Buildings101 and 102. Some of these data have been provided by NSWC-IHDIV in a textsummary form to ATSDR. ATSDR requests the primary data and medical records inorder to draw conclusions about potential exposure-related health effects.
The National Institute for Occupational Safety and Health (NIOSH) has examined the potentialfor 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 hygieneprograms, including the program currently in place at the NSWC-IHDIV, are designed toprevent take home contamination by workers who work with hazardous chemicals.
Chemicals such as mercury may be transported into the home unknowingly on work clothesand shoes, or deliberately by persons who are unaware of the hazards of workplacechemicals. Mercury contamination in the home can result in exposures to children and adultresidents to vapors at concentrations of health concern. For residential properties, and forpopulations of people who may be more sensitive to chemical exposures such as youngchildren and women of child-bearing years, ATSDR recommends that mercury vaporconcentrations 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 inhome 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-contaminatedhomes 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 102presents a potential for past tracking of mercury from these buildings into the homes ofworkers. Observations which support this concern include: (i) the long history of mercury usein large quantities in both buildings; (ii) the documented spills and routine releases of mercurythat resulted in contamination of the buildings; (iii) the undefined extent of mercurycontamination in these buildings; (iv) the period of time between 1960 and 1980 whenmercury contamination was present pre-dates the establishment of the base program formedical monitoring for mercury and environmental monitoring for worker exposure; (v) onlylimited 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 setsfor these buildings.
Taken together, these elements strongly suggest the opportunity for past workers in thebuilding to come into contact with mercury contamination under conditions where it could bepicked up on clothes and shoes unintentionally, or deliberately by a building employee notaware of the hazard, and tracked into the home. ATSDR's concern lies in the potential forcurrent residents of these homes to experience on-going inhalation exposures to mercuryvapors. Adults and children exposed to chronic low levels of mercury vapor may developnervous system effects including fine tremors in the fingers, lips and eyelids, and effects onprecision movements such as handwriting. Headaches and difficulties with short-term memorymay also occur (28). In general, individuals with diseases of the liver, kidney, lung, and nervesare considered to be at greater risk of suffering from the toxic effects of mercury thanindividuals in good general health. Inhaled metallic mercury can reach the fetuses of pregnantwomen 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'smilk to breast-feeding infants. These pre-birth and post-birth exposures place these children atrisk for nervous system development problems (18). Additional information about exposures tomercury in the environment is provided in the ATSDR Public Health Statement which isprovided in Appendix E of this public health assessment.
- It is possible that some of the spilled mercury in Buildings 101 and 102 was tracked intothe homes of workers.
- It is not possible to project back into the past and know with certainty whether workerhome contamination has occurred. However, the conduct of simple visual inspections,combined with in-home mercury vapor screening, would provide the evidence neededto determine in any exposures to "take home" mercury are occurring today. Therefore,ATSDR recommends that IHDIV-NSWC perform environmental screening of theresidences where Building 101 and 102 employees lived during their period ofemployment in those buildings. The list of residences proposed for screening shouldinclude the homes where any personnel who worked in these buildings between 1960and 1991 resided.
If the implementation of this recommendation is outside the appropriate scope ofIHDIV-NSWC responsibilities and resources, ATSDR possesses the capability tocoordinate with NSWC and perform the residential screenings in support of publichealth activities at the base.
No mercury clean-ups have been performed in Buildings 101 and 102. The mercurycontaminated area of Building 101 was closed in response to the discovery of elevatedmercury vapors and remains secured from entry and posted with a warning sign. This buildingis 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 RemedialInvestigation (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 theenvironment, or impact a military construction project) for RI characterization and clean-upactivities. Mercury vapors persist at detectable concentrations in areas of both buildings atconcentrations as high as 0.03 mg/m3: this concentration exceeds the ATSDR Minimal RiskLevel and EPA's Reference Concentration for mercury vapor. Therefore, indoor air levels ofmercury in these buildings exceed acceptable levels that are protective of public health.
ATSDR was concerned that indoor air concentrations could increase in response to futurebuilding uses that disturb the mercury, including renovation activities, before completion ofclean-up activities. However, during the course of the public health assessment, the NSWCSafety department determined that use of Buildings 101 and 102 will not be permitted until themercury within the buildings has been remediated (10). Preventing use of the buildingseliminates the exposure pathway to the mercury vapors and ATSDR's public health concern.
Summary: Concentrations of cadmium, mercury, and zinc in Mattawoman Creek fish tissue donot 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 todetermine if these metals are entering the food chain in Mattawoman and Chicamuxen Creeksand bioaccumulating to concentrations requiring consumption limits. A summary of ourevaluation of this situation is provided in Tables 4a and 4b.
Background: Studies conducted by the U.S. Fish and Wildlife Service provide data on levelsof 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 inMattawoman Creek fish tissue ranged from below to slightly above levels documented insimilar monitoring programs in Potomac River, Maryland, and U.S. studies (34). ATSDRevaluated these data using the chemical-specific Risk-Based Concentration (RBC) values forfish tissue(35). U.S. EPA's RBCs are useful data-screening tools that assume exposure to onlyone 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 (0.1milligrams 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 to0.37 mg/kg. Similarly, maximum zinc concentrations in tissue samples from six species of fishand the brackish water clam ranged from 14 to 55 mg/kg. These values are 7 to 29 timeslower than the RBC for zinc (410 mg/kg).
Using available data, we conclude that the 1991 concentrations of cadmium, mercury, and zincin 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 RBCscreening value. Although only five (5) fish of each species were collected and analyzed, theamount of contaminant to which an individual would normally be exposed in the edible portionof the fish would be less than the whole fish concentrations reported in Table 5. Consumptionof fish caught from these creeks is not a health concern.
Other chemical contaminants from the NSWC-IHDIV have also impacted the surroundingsediments: lead, silver, chromium and copper are documented to occur in Mattawoman Creeksediments at elevated concentrations relative to background and Chesapeake Bay referencesites (33). These chemicals may bioaccumulate in certain species of fish. However, becausethese chemicals were not included in the fish tissue analyses that have been conducted, it isnot known whether they are entering the food chain in Mattawoman and Chicamuxen Creeksand bioaccumulating. The U.S. Fish and Wildlife Service has recommended that additionalfish tissue analyses be performed and that the concentrations of selected chemicals in thebase's discharges be reduced (33).
|PATHWAY NAME||CONTAMINANTS||EXPOSURE PATHWAYS ELEMENTS|
Contaminated fishin Mattawomanand ChicamuxenCreeks
Releases of hazardoussubstances to soils andshallow groundwater at thesite, and historical dischargesof munitions process wastewaters to the creeks
Eating (ingestion of )contaminated fish
Potentially Exposed:people who eatcontaminated fish fromthe creeks
No apparent health hazardis posed by the metalscontaminants to peopleeating fish caught from thecreeks. Concentrationsare below levels of healthconcern
|PATHWAY NAME||CONTAMINANTS||EXPOSURE PATHWAYS ELEMENTS||TIME||COMMENTS|
Contaminated fishin Mattawomanand ChicamuxenCreeks
Lead, silver,chromium, copper
Releases of hazardoussubstances to soils andshallow groundwater at thesite, and historical dischargesof munitions process wastewaters to the creeks
Eating (ingestion of)contaminated fish
people who eatcontaminated fish fromthe creeks
Future sampling shouldalso include tissueanalyses for lead, silver,chromium, and copper todetermine if these metalsare bioaccumulating toconcentrations of publichealth concern.
|Channel Catfish||0.068||< 0.1||55|
|Largemouth Bass||0.370||< 0.1||NAf|
|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|
|Brackish Water Clam||0.025||< 0.1||17|
(RBC) screening value
Note: mercury, cadmium, and zinc were chosen by the U.S. Fish and Wildlife Service foranalysis in tissue samples based on records of maximum discharge concentrations fromNSWC-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.
- Concentrations of mercury, cadmium, and zinc in fish from Mattawoman Creek are below levels of health concern and do not pose a threat to people eating the fish.
- Insufficient data exist to evaluate whether lead, silver, chromium or copper arebioaccumulating in fish tissue to concentrations of public health concern.
Actions Taken or Proposed:
- Numerous efforts by NSWC-IHDIV to reduce or eliminate discharges to the Mattawoman and Chicamuxen Creeks and the Potomac River include (i) the connection of the industrial wastewater discharges to the sanitary sewer system, which permits sampling and treatment prior to release (rather than discharging directly to the local creeks and river); and (ii) the construction of sediment and erosion controls at the wastewater outfalls, many of which are ditches, in order to prevent the release of suspended sediments into the creeks and river. In the future, a central sewage system connection is planned for the Stump Neck Annex in order to eliminate septic tank discharges.
- Clean-up actions already been completed by NSWC-IHDIV, and clean-up activities willbe completed in the future, will reduce the contaminated soil runoff and shallowgroundwater discharges of contaminants to the creeks and river.
Mattawoman Creek supports significant recreational and limited commercial fishing activity.However, Remedial Investigation studies at NSWC and RCRA Corrective Action investigationsat the Stump Neck Annex do not currently include sampling activities to monitor possible futurefood chain contamination in Mattawoman and Chicamuxen Creeks (3, 4). Therefore, ATSDR makes the following recommendations:
- If follow-up studies conducted by the U.S. Fish and Wildlife Service do not include fish tissue analyses for lead, silver, chromium, and copper, we recommend that NSWC-IHDIV initiate a sampling program to fill this data gap.
- In the event that future remedial, RCRA closure, or RCRA corrective action activities,will disturb wastes and release contaminants to the creeks, ATSDR recommendsadditional collection and analysis of fish at that time.
Both sampling recommendations will permit NSWC-IHDIV to determine whether metals in thewater and sediments are bioaccumulating in fish to concentrations requiring consumption limitsto protect public health. In the event that such sampling is proposed, ATSDR requestsinvolvement in the review of the Work Plan for those activities in order to ensure that theproposed sampling and analyses will generate the type and quality of data needed to drawconclusions about potential human health impacts.
Summary: NSWC-IHDIV is implementing a wellhead protection program to ensure that thegroundwater wells at the base do not serve, in the future, as conduits for the migration ofshallow contaminated groundwater to the deeper aquifers. This plan is needed to ensureprotection of the deep groundwater resources that serve as the drinking water supply for thebase 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 resultedin the release of chemical contaminants to soils and shallow groundwater at IRP and RCRAsites located throughout the facility (3, 5, 3). This shallow groundwater contamination does notcurrently pose a public health threat: drinking water supplies for the NSWC-IHDIV and themajority of the surrounding community are obtained from the deep Patapsco and Patuxentgroundwater aquifers. These aquifers are separated from the contaminated surface soils andshallow 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 NeckAnnex, lie upgradient from the contaminated areas at the base. These off-base private wellsare 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 accordancewith current groundwater protection standards, may serve as conduits for migration of chemicalcontaminants 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 andto the early 1900s on the Cornwallis Neck peninsula (5). In addition, NSWC-IHDIV isexperiencing problems with lowered water tables and saline water intrusion related toincreased regional water demands (3, 36, 37). Lowered water tables, saline water intrusion andthe potential for chemical contamination of the deeper aquifer are inter-related phenomena. Inthe same way that increased groundwater pumping rates and volume will lower water tablesand permit the infiltration of saline water into the freshwater aquifer, the reduction of pressureexerted by the deep aquifer in the well casings increases the possibility of downward migrationof chemically contaminated shallow groundwaters.
- These existing water supply problems, combined with the potential future public healthissue of chemical contamination, underscores the need for wellhead protectionactivities at the NSWC-IHDIV.
Actions Taken and Planned
- Since ATSDR's site visit in 1996, the NSWC-IHDIV worked with the MarylandDepartment of the Environment to establish a wellhead protection program. Currentand proposed efforts include record searches to locate missing wells, verification thatabandoned wells have been properly abandoned, and camera surveys to determinewell casing integrity. Based on the results of these efforts, wells will be repaired,replaced, or abandoned, as appropriate (12).
- NSWC-IHDIV should ensure that wells located hydraulically down-gradient ofchemically contaminated areas and, therefore, at greater risk of contamination, receivehigh priority for early action under the wellhead protection program.
|PATHWAY NAME||CONTAMINANTS||EXPOSURE PATHWAYS ELEMENTS||TIME||COMMENTS|
Drinking WaterSupply - Patapscoand PatuxentAquifers
Solvents, mercury,silver, lead, othermetals, nitrateesters
Historical releasesof hazardoussubstances to soilsand shallowgroundwater atsites locatedthroughout thebase
NSWC-IHDIVdrinking watersupply system
Water supply wells that(i) are aged (dating toearly 1900s)
(ii) are improperlyabandoned
(iii) are out of servicebut not abandoned, or
(iv) cannot be located,potentially serving asconduits for shallowgroundwatercontaminant migrationto the deeper supplyaquifer
residents, employees atNSWC-IHDIV
To date, water well samplingdoes not indicatecontamination of the deeperaquifer by the shallowcontaminated groundwaters. The on-going developmentand implementation of awellhead protection programby NSWC-IHDIV shouldprevent possible futureexposure.