PUBLIC HEALTH ASSESSMENT
NAVAL AIR STATION PATUXENT RIVER
ST. MARY'S COUNTY, MARYLAND
We describe here one situation in which exposure to contaminants may be occurring, but posesno apparent public health hazard, two situations in which the presence or absence ofcontaminants has not been determined, and two others in which contamination is present, but noone is being exposed. In this section we will discuss available information that relates to ouranalysis and suggest measures to mitigate risks. When appropriate, we list additionalinformation that should be gathered in a situation to add data necessary for a completedetermination.
ATSDR's public health assessments are exposure, or contact, driven. Chemical contaminantsdisposed of or released into the environment at NAS Patuxent River have the potential to causeadverse health effects. However, not all releases result in exposure. Persons can only beexposed to a chemical if they come in contact with that chemical. Exposure may occur bybreathing, eating, or drinking a substance containing the contaminant or by skin (dermal) contactwith a substance containing the contaminant.
The type and severity of health effects that occur in an individual from contact with acontaminant depend on exposure concentration (how much), frequency and/or duration ofexposure (how long), route or pathway of exposure (breathing, eating, drinking, or skin contact),and the multiplicity of exposures (combination of contaminants). Once exposure occurs,characteristics such as age, sex, nutritional status, genetics, lifestyle, and health status of theexposed individual influence how that individual absorbs, distributes, metabolizes, and excretesthe contaminant. Together these factors and characteristics determine what health effects mayoccur as a result of exposure to a contaminant.
ATSDR concluded that one situation on the NAS Patuxent River installation poses no apparentpublic health hazard: eating fish caught from Pond 3 on base.
On April 4, 1989, the Hazardous and Solid Waste Administration of the Maryland Department ofthe Environment (MDE) issued a site complaint requiring NAS Patuxent River to banconsumption of fish from Pond 3, one of 6 on-base ponds, due to pesticide contamination foundupgradient at Site 17, the Pesticide Shop (4). The concern was that contaminants from the Pesticide Shop may have migrated to Pond 3 via a drainage ditch during heavy rains. NASPatuxent River personnel sampled largemouth bass and catfish from Pond 3 on April 4, 1990,according to an MDE protocol (5). The mean weight of the bass sampled was 0.51 kg (range of0.22 - 1.36 kg). A weight of 0.51 kg corresponds to 1.1 pounds. The two catfish weighed 0.22kg and 0.43 kg, respectively. Fillets were analyzed.
|PATHWAY NAME||CONTAMINANT(S) OF CONCERN||EXPOSURE PATHWAY ELEMENTS||TIME||COMMENTS|
|SOURCE||ENVIRONMENTAL MEDIA||POINT OF EXPOSURE||ROUTE OF EXPOSURE||POTENTIALLY EXPOSED POPULATION|
|Fish in Pond 3*||DDT, DDE, DDD||Unknown||Fish||Eating Pond 3 fish||Ingestion||Recreational harvesters who eat contaminated fish||PastPresentFuture||Site 17 wasfirst thought tobe the sourceof DDT inPond 3.|
|PCBs||Unknown||Fish||Eating Pond3 fish||Ingestion||Recreationalharvesters whoeatcontaminatedfish||PastPresentFuture||Source ofPCBs in Pond3 is not known.|
|Fish in Ponds1, 2, 4, 5, 6**||PCBs possible||Unknown||Fish||Eating pondfish||Ingestion||Recreationalharvesters whoeatcontaminatedfish||PastPresentFuture||Data toestimate PCBconcentrationsin Ponds 1, 2,4, 5, 6 fish areneeded.|
|Fish andShellfish inChesapeakeBay, PatuxentRiver, andSeaplaneBasins**||Various arepossible,includingmetals, PAHsand PCBs||Possiblesources:Sites 1, 4,11, 15, 23,24, and theFuel Farm||Fish and shellfish||Eating fishandshellfish||Ingestion||Recreationalharvesters whoeatcontaminatedfish andshellfish||PastPresentFuture||Data on contaminant concentrations in fish and shellfish are needed.|
* No Apparent Public Health Hazard
** Indeterminate Public Health Hazard
PCBs - Polychlorinated Biphenyls
PAHs - Polycyclic Aromatic Hydrocarbons
The only contaminants found at significant levels were the pesticide DDT, two breakdownproducts (DDD and DDE), and polychlorinated biphenyls (PCBs) (6). Data for the seven bassand two catfish sampled are shown in Table 2. From the levels of DDT and its breakdownproducts found in fish, MDE lifted its ban and established a consumption limit of two, 8-ozmeals per month and no more than 19 meals per year from Pond 3 (7). No fish sampling in theponds has been reported since 1990.
ATSDR reviewed the 1990 fish data and performed an exposure evaluation using site-specificassumptions for cancerous and non-cancerous health implications. Our cancer-risk calculationsidentified PCBs as the consumption-limiting contaminant. We agree with the state's limit of 19meals/year, but for additional risk reduction, we recommend an exposure duration of no morethan 7 years at this rate of annual consumption. The acceptable consumption rate is no morethan two, 8-oz meals per month or 19 meals/year, based on an exposure duration of 7 years, avalue derived from and justified by the median head-of-household occupancy time for the region(8). With an average length of residence of approximately 5 years for the vicinity of NASPatuxent River, the 7-year exposure-duration limit should not affect the majority of pond-fishconsumers. However, because Department of Natural Resources personnel on base hand outeducational materials including size, creel, and consumption limits with the required annualpermits, they can easily convey a consumption limit of 19 fish meals/year for no more than 7years. Indeed, they may point out, if they wish, that consumers who eat less than an average of19 pond-fish meals/year may continue to eat the fish until they reach the lifetime limit of 133meals. Our calculations and greater detail on our assumptions are shown in Appendix C.
ATSDR concluded that eating fish caught from Ponds 1, 2, 4, 5, and 6 on base and eating fishand shellfish from areas of Chesapeake Bay and the Patuxent River affected by IRP sites pose anindeterminate public health hazard.
Despite the original concern about Site 17, the source of contaminants in Pond 3 remainsunknown. This raises the possibility that one or more of the other 5 ponds may contain fish withthese contaminants from the same unknown source. Because a point source for the contaminantshas not been identified, it is unlikely that these compounds are present at higher concentrations in Ponds 1, 2, 4, 5, and 6 than in Pond 3, which is larger and drains a larger area. ATSDRsuggests that measures be taken to prevent possible significant human exposure to PCBs due toconsumption of fish from Ponds 1, 2, 4, 5, and 6. As an interim measure we recommend twomeals/month and 19 meals/year consumption limits on fish from these ponds as well. Werecommend sampling sediment in all 6 ponds to determine whether contaminant levels exceedEPA screening levels and warrant fish sampling in Ponds 1, 2, 4, 5, and 6 .
Several present or former IRP sites have the potential to contaminate surface waters associatedwith the base, including the river, bay, and seaplane basins. Such sites on the northeast section ofthe installation, near the Patuxent River and its 2 basins, include the Fishing Point Landfill (Site1), the Defense Reutilization and Marketing Office Yard (Site 23), and the Fuel Farm (nowincluded in the Underground Storage Tank Program and located immediately northwest of Site 6,encompassing Site 9 and the Supply Pond). Sites of concern on the western (Chesapeake Bay)side of NAS Patuxent River are those within the Pine Hill Run drainage area, such as Sites 4, 11,22, and 24. (Site names are given in Appendix B). ATSDR recommends the collection ofsediment and shellfish samples from the river, bay, and seaplane basins during the RemedialInvestigation process (9). Results of sediment analyses would be an indicator for contaminationemanating from base sites. Comparison with baseline data available for sediments inChesapeake Bay from the Mussel-Watch Program of the National Oceanic and AtmosphericAdministration (10) and other databases would indicate whether site-specific contaminationmight be occurring and whether there might be an uptake by fish and shellfish. Suites ofcompounds for assay should be chosen based on contaminants, such as polycyclic aromatichydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated pesticides, and metals, thathave been characterized on potentially contributing IRP sites.
Limited analytic data available on river, bay, and basin sediments and aquatic fauna exist fromseveral sources (11, 12, 13). The data are insufficient to characterize levels of possiblecontaminants in these media in areas near the NAS Patuxent River shoreline. Contamination inthe sediments is of public health interest primarily because of the potential for bioaccumulationof certain of these contaminants in fish and shellfish that people consume. Benthic invertebratessuch as oysters and clams can serve as useful, immobile, sentinel species to characterize theextent of bioaccumulation. Unfortunately, the population of native oysters (Crassostreavirginica) has been decimated in many areas of the bay by intensive harvesting, high rates ofsedimentation, and the ravages of two protozoal parasites (Perkinsus marinus andHaplosporidium nelsoni). Oysters are not available in sufficient distribution and numbers nearNAS Patuxent River to permit collection of definitive data. We recommend collection ofspecimens of an abundant edible shellfish (perhaps the softshell clam, for example), in concertwith sediment sampling, to establish whether possible contaminants in sediment might bebioaccumulating in aquatic fauna to levels that pose a potential public health hazard.
- Bass and catfish in Pond 3 are contaminated with PCBs at concentrations that increase risk of cancer in recreational anglers. The source of the PCB contamination in Pond 3 is unknown.
- No analytic data are available to permit an estimation of PCB or other contaminant concentrations in either sediment or fish in Ponds 1, 2, 4, 5, or 6. These ponds may also be contaminated by the same or a similar source as Pond 3, particularly because Pond 6 is used as a brood pond for the other five.
- ATSDR cannot determine whether consumption of fish or shellfish from nearby areas of thePatuxent River or Chesapeake Bay or from the Seaplane Basins poses a public health concern atthis time, because existing data are insufficient to evaluate levels of contaminants in fish andshellfish from waters possibly affected by IRP sites.
- Drainage ditches downgradient of the Pesticide Shop (Site 17) that carried stormwater runoffto Pond 3 were excavated to remove 3245 tons of contaminated soil. The soil was hauled to aRCRA-approved landfill, and clean soil and topsoil were used for backfill.
- We recommend instituting a limit of two 8-ounce meals/month up to 19 meals/year over a 7-year exposure duration for all on-base ponds. We further recommend sediment sampling in Ponds 1 to 6 to determine contaminant concentrations. These concentrations can then be compared with screening levels for ecological resources that EPA and NOAA (National Oceanic and Atmospheric Administration) are developing to determine whether fish sampling is necessary. The combination of these sediment data and available fish data from Pond 3 should then provide a measure of the predictive value of sediment concentrations for fish levels.
- We recommend sampling sediments and a species of edible shellfish from the Patuxent River,Chesapeake Bay, and Seaplane Basins in areas that are potentially impacted by IRP sites, andanalyzing for likely contaminants. Comparing the sediment-analysis values found withsimultaneously acquired reference background analytic results and appropriate data available infederal, state, and other environmental databases could identify possible migration ofcontaminants. Depending on the sediment data and possible exposures, the need for additionalsampling of biota for human consumption can be determined. ATSDR will review samplingplans as they become available.
ATSDR concluded that two situations on the NAS Patuxent River installation pose no apparentpublic health hazard: 1) the possibility for future contamination of deep wells on base and,thereby, the deep aquifer and 2) on-site physical hazards or surface contaminants.
The Coastal Plain area near NAS Patuxent River is underlain by several aquifers. The surficialaquifer, the shallowest, is unconfined and discharges primarily to surface water. The PineyPoint, Nanjemoy, and Aquia Aquifers (listed in order of increasing depth) are confined. TheAquia Aquifer is the primary source of potable water for the installation and surrounding areas. The initial assessment study for NAS Patuxent River reported in 1984 that the Piney PointAquifer was leaking into the Aquia Aquifer via faulty casings in some area wells (14).
A system of base wells pumps water for drinking from the Aquia and the Piney Point/NanjemoyAquifers. The three water towers on the installation are each served by several wells (15). Otherwells directly serve specific locations on the facility. As recently as early 1994, 12 of the wells inservice tapping the Aquia Aquifer were more than 50 years old (16). The concern is that casingson wells of this age may be deteriorating, providing a pathway for contaminated shallowgroundwater to enter the lower aquifers. Such wells can be sampled at the wellhead and thewater analyzed for contaminants present in nearby groundwater to test for casing leakage, or theycan be inspected in detail for casing integrity. In concert or alternatively, old wells in areas ofgroundwater contamination can be proactively repaired or replaced according to a scheduledictated by criteria including well age, groundwater quality, and projected availability of fundingover time.
During 1994, casings of six of the older wells in use on base were inspected with down-wellvideo cameras using monies available from a fund earmarked for NAS Patuxent Riverinfrastructure maintenance. A breach was found in one of the casings; however, the decision wasmade to seal all six wells, five of which were more than 50 years old, and to drill new wells toreplace lost capacity. Three additional Aquia-Aquifer wells more than 50 years old have beenreplaced since 1994. Of the 25 currently active drinking water wells on the installation, only 4 ofthe 17 accessing the Aquia Aquifer are more than 50 years old. These four have been regularlyand meticulously inspected for structural integrity.
We recommend that a long-term plan be in place and periodically upgraded for continued monitoring of well-casing integrity and repair or seal of wells as results dictate, integrated withproactive replacement of selected wells as funding permits.
Because groundwater on base flows toward the river and the bay, it does not contribute tocontamination of off-base groundwater; thus no pathway exists whereby on-base groundwatercontamination could enter the deep aquifer via poorly sealed off-base wells.
The 46 IRP sites do not present on-site physical or chemical public health hazards because accessis restricted or limited by fences, natural barriers, capping of the site, and/or posting. A proposalto post selected additional IRP sites on base has been implemented at NAS Patuxent River (17). The restrictions to site access are designed to prevent on-site exposure. Migration ofcontaminants from these sites to areas where surficial exposure might occur is not expectedand/or the sites have already been adequately remediated. Current and planned remediation atNAS Patuxent River is designed to prevent future exposures. A summary of the IRP sites andATSDR's evaluation of why they are not a public health hazard is in Appendix D. ATSDRconcluded that the IRP sites represent no public health hazard from on-site physical hazards orsurface contaminants. Contamination may be present from past disposal practices, butconditions exist that make it unlikely people would be exposed to these contaminants. If land usechanges at any of these sites, the potential for human exposure should be reevaluated.
- Although some contamination of groundwater exists, no human exposure to this groundwater occurs. The Aquia, Nanjemoy, and Piney Point Aquifers are separated from shallow groundwater by impermeable strata. No potable water sources on the installation draw from shallow groundwater.
- Groundwater contamination on base does not currently appear to threaten deep aquifers that supply on-base or community water wells. Intervening nonpermeable layers prevent accessibilityof groundwater to the deep aquifer. The possibility exists that breaches may occur in old well casings, contaminating the drinking water from affected wells and fouling the aquifer itself.
- NAS Patuxent River has identified on-base groundwater contamination, removed sourceswhere appropriate, and monitors such contamination to prevent adverse impact on potable watersources.
- Continue to sample wells that supply water from the deep aquifer and analyze according to Safe Drinking Water Standards.
- Remediate remaining IRP sites that contribute significantly to groundwater contamination.
- Continue to inspect older water wells and seal as necessary or prudent as an important part ofa long-term maintenance program providing discretionary funds to update and upgrade NASPatuxent River infrastructure.
- Continue and regularly update a long-term, coordinated plan to monitor potable water wells. Levels of proximate, upgradient groundwater contamination and age of well would serve ascriteria for selecting wells and corresponding method and frequency of monitoring. Wellswould be rehabilitated or abandoned and sealed when monitoring indicates the need. However, proactive replacement of selected wells before specific problems are demonstrated is preferable,funds permitting, because monitoring is reactive to problems that may have already caused somewellwater and deep-aquifer contamination.
- The 46 IRP sites present no on-site surficial physical or chemical public health hazard becauseaccess is restricted and no migration of contaminants is expected to areas where such exposuremight occur.
- NAS Patuxent River has proposed posting of those IRP sites to which access is otherwiseinsufficiently restricted. This proposal has been implemented at the direction of the NASPatuxent River Commanding Officer.
- NAS Patuxent River continues remediation of sites and will remove postings as appropriatewhen sites are removed from the IRP list.
Health concerns were expressed by citizen members of the Restoration Advisory Board (RAB)for NAS Patuxent River.
- A citizen was told several years ago by someone who helped in the 1940s to constructhouses in a subdivision near the Naval Air Station, that 55-gallon drums had beendiscarded and buried in nearby gullies. This citizen and others asked about possibleadverse health effects that could occur from such dumping. They were especiallyconcerned about what seemed to them an unusually high number of cases of canceroccurring in the subdivision.
ATSDR made several efforts through the citizen to meet with the apparent eyewitness and havehim identify the location of the alleged burials. When ultimately contacted, the person did notremember seeing any burials of drums. Even if such burials had occurred in the 1940s, the mostlikely way people could come in contact with contaminants would be to drink groundwater fromwells that had become contaminated when drums leaked into the soil and leached into thegroundwater. A community water distribution system has been in place since the first houseswere built in the subdivision (18). The source of this water has been a confined aquifer, which isseparated from shallow groundwater by impermeable layers. No mixing of this drinking watersupply with shallow groundwater (or any contaminants that might have been in the shallowgroundwater) would have been possible. Thus, persons drinking the tap water were not exposedto any contaminant that might have been in the shallow groundwater. Any exposure togroundwater by skin contact, ingestion, or inhalation would have been incidental and infrequent(for example, as in the case of flooded basements). Had drums been placed in gullies and thencovered, no surface soil would have been contaminated to permit exposure of persons. Even ifdumping did occur, it appears that residents would have encountered little or no exposure tohazardous materials and would not have experienced adverse health effects.
A cancer survey was performed by the Maryland Department of the Environment, in coordinationwith the St. Mary's County Department of Health. The cancer incidence within the area of theLexington Park zip code (20653) was compared with statewide incidence for the time period1989 - 1991, the years for which data were available in a form that permits comparisons down tothe zip code level. The cancer incidence for all cancers was slightly, but statisticallysignificantly, less for Lexington Park than for the State of Maryland as a whole. (Incidence isdefined as the number of new cancers per year for each 100,000 persons.) Cancer deaths per yearfor each 100,000 persons and incidence of breast cancer were also reviewed for the same timeperiod and showed no statistically significant elevation for Lexington Park compared withstatewide numbers (19).