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1. ATSDR > Public Health Assessments & Consultations

INTRODUCTION

We describe here one situation in which exposure to contaminants may be occurring, but poses no apparent public health hazard, two situations in which the presence or absence of contaminants has not been determined, and two others in which contamination is present, but no one is being exposed. In this section we will discuss available information that relates to our analysis and suggest measures to mitigate risks. When appropriate, we list additional information that should be gathered in a situation to add data necessary for a complete determination.

ATSDR's public health assessments are exposure, or contact, driven. Chemical contaminants disposed of or released into the environment at NAS Patuxent River have the potential to cause adverse health effects. However, not all releases result in exposure. Persons can only be exposed to a chemical if they come in contact with that chemical. Exposure may occur by breathing, eating, or drinking a substance containing the contaminant or by skin (dermal) contact with a substance containing the contaminant.

The type and severity of health effects that occur in an individual from contact with a contaminant depend on exposure concentration (how much), frequency and/or duration of exposure (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 the exposed individual influence how that individual absorbs, distributes, metabolizes, and excretes the contaminant. Together these factors and characteristics determine what health effects may occur as a result of exposure to a contaminant.

I. NO APPARENT PUBLIC HEALTH HAZARD

ATSDR concluded that one situation on the NAS Patuxent River installation poses no apparent public health hazard: eating fish caught from Pond 3 on base.

Fish in Pond 3

On April 4, 1989, the Hazardous and Solid Waste Administration of the Maryland Department of the Environment (MDE) issued a site complaint requiring NAS Patuxent River to ban consumption of fish from Pond 3, one of 6 on-base ponds, due to pesticide contamination found upgradient 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. NAS Patuxent 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 of 0.22 - 1.36 kg). A weight of 0.51 kg corresponds to 1.1 pounds. The two catfish weighed 0.22 kg and 0.43 kg, respectively. Fillets were analyzed.

* 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 breakdown products (DDD and DDE), and polychlorinated biphenyls (PCBs) (6). Data for the seven bass and two catfish sampled are shown in Table 2. From the levels of DDT and its breakdown products found in fish, MDE lifted its ban and established a consumption limit of two, 8-oz meals per month and no more than 19 meals per year from Pond 3 (7). No fish sampling in the ponds has been reported since 1990.

Table 2 - Concentrations of DDT, its breakdown products, and PCBs in Pond 3 fish, Naval Air Station Patuxent River site, Maryland, 1990
Sample Designation		Contaminant Concentration (µg/kg)
		DDE	DDD	DDT	PCBs
Bass	1B	111	315	20	83
	2B	73	331	24	112
	3B	5	29	10	87
	4B	11	87	16	203
	5B	5	54	15	170
	6B	9	58	13	60
	7B	26	60	<10	100
	Average	34.3	133.4	14	116.4
Catfish	1C	8	41	<10	140
	2C	40	10	<10	19
	Average	24	25.5	<10	79.5
These results are from a single round of sampling in 1990. Fillets were analyzed. Please see the text for information on the weights of fish sampled for analysis.

ATSDR reviewed the 1990 fish data and performed an exposure evaluation using site-specific assumptions for cancerous and non-cancerous health implications. Our cancer-risk calculations identified PCBs as the consumption-limiting contaminant. We agree with the state's limit of 19 meals/year, but for additional risk reduction, we recommend an exposure duration of no more than 7 years at this rate of annual consumption. The acceptable consumption rate is no more than two, 8-oz meals per month or 19 meals/year, based on an exposure duration of 7 years, a value 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 NAS Patuxent River, the 7-year exposure-duration limit should not affect the majority of pond-fish consumers. However, because Department of Natural Resources personnel on base hand out educational materials including size, creel, and consumption limits with the required annual permits, they can easily convey a consumption limit of 19 fish meals/year for no more than 7 years. Indeed, they may point out, if they wish, that consumers who eat less than an average of 19 pond-fish meals/year may continue to eat the fish until they reach the lifetime limit of 133 meals. Our calculations and greater detail on our assumptions are shown in Appendix C.

II. INDETERMINATE PUBLIC HEALTH HAZARD

ATSDR concluded that eating fish caught from Ponds 1, 2, 4, 5, and 6 on base and eating fish and shellfish from areas of Chesapeake Bay and the Patuxent River affected by IRP sites pose an indeterminate public health hazard.

A. Fish in Ponds 1, 2, 4, 5, and 6

Despite the original concern about Site 17, the source of contaminants in Pond 3 remains unknown. This raises the possibility that one or more of the other 5 ponds may contain fish with these contaminants from the same unknown source. Because a point source for the contaminants has 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. ATSDR suggests that measures be taken to prevent possible significant human exposure to PCBs due to consumption of fish from Ponds 1, 2, 4, 5, and 6. As an interim measure we recommend two meals/month and 19 meals/year consumption limits on fish from these ponds as well. We recommend sampling sediment in all 6 ponds to determine whether contaminant levels exceed EPA screening levels and warrant fish sampling in Ponds 1, 2, 4, 5, and 6 .

B. Fish and Shellfish in Patuxent River, Chesapeake Bay, and the Seaplane Basins

Several present or former IRP sites have the potential to contaminate surface waters associated with the base, including the river, bay, and seaplane basins. Such sites on the northeast section of the installation, near the Patuxent River and its 2 basins, include the Fishing Point Landfill (Site 1), the Defense Reutilization and Marketing Office Yard (Site 23), and the Fuel Farm (now included 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 of sediment and shellfish samples from the river, bay, and seaplane basins during the Remedial Investigation process (9). Results of sediment analyses would be an indicator for contamination emanating from base sites. Comparison with baseline data available for sediments in Chesapeake Bay from the Mussel-Watch Program of the National Oceanic and Atmospheric Administration (10) and other databases would indicate whether site-specific contamination might be occurring and whether there might be an uptake by fish and shellfish. Suites of compounds for assay should be chosen based on contaminants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated pesticides, and metals, that have been characterized on potentially contributing IRP sites.

Limited analytic data available on river, bay, and basin sediments and aquatic fauna exist from several sources (11, 12, 13). The data are insufficient to characterize levels of possible contaminants in these media in areas near the NAS Patuxent River shoreline. Contamination in the sediments is of public health interest primarily because of the potential for bioaccumulation of certain of these contaminants in fish and shellfish that people consume. Benthic invertebrates such as oysters and clams can serve as useful, immobile, sentinel species to characterize the extent of bioaccumulation. Unfortunately, the population of native oysters (Crassostrea virginica) has been decimated in many areas of the bay by intensive harvesting, high rates of sedimentation, and the ravages of two protozoal parasites (Perkinsus marinus and Haplosporidium nelsoni). Oysters are not available in sufficient distribution and numbers near NAS Patuxent River to permit collection of definitive data. We recommend collection of specimens of an abundant edible shellfish (perhaps the softshell clam, for example), in concert with sediment sampling, to establish whether possible contaminants in sediment might be bioaccumulating in aquatic fauna to levels that pose a potential public health hazard.

Conclusions and Public Health Action Plan for Possible Fish and Shellfish Contamination
(Ponds, River, Bay and Seaplane Basins)

Conclusions:

1. 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.

2. 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.

3. ATSDR cannot determine whether consumption of fish or shellfish from nearby areas of the Patuxent River or Chesapeake Bay or from the Seaplane Basins poses a public health concern at this time, because existing data are insufficient to evaluate levels of contaminants in fish and shellfish from waters possibly affected by IRP sites.

Completed Action:

1. Drainage ditches downgradient of the Pesticide Shop (Site 17) that carried stormwater runoff to Pond 3 were excavated to remove 3245 tons of contaminated soil. The soil was hauled to a RCRA-approved landfill, and clean soil and topsoil were used for backfill.

Recommended Actions:

1. 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.

2. 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, and analyzing for likely contaminants. Comparing the sediment-analysis values found with simultaneously acquired reference background analytic results and appropriate data available in federal, state, and other environmental databases could identify possible migration of contaminants. Depending on the sediment data and possible exposures, the need for additional sampling of biota for human consumption can be determined. ATSDR will review sampling plans as they become available.

III. NO PUBLIC HEALTH HAZARD

ATSDR concluded that two situations on the NAS Patuxent River installation pose no apparent public 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.

A. Possible Future Contamination of On-base Deepwater Wells, Prevention Needed

The Coastal Plain area near NAS Patuxent River is underlain by several aquifers. The surficial aquifer, the shallowest, is unconfined and discharges primarily to surface water. The Piney Point, Nanjemoy, and Aquia Aquifers (listed in order of increasing depth) are confined. The Aquia 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 Point Aquifer 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/Nanjemoy Aquifers. The three water towers on the installation are each served by several wells (15). Other wells directly serve specific locations on the facility. As recently as early 1994, 12 of the wells in service tapping the Aquia Aquifer were more than 50 years old (16). The concern is that casings on wells of this age may be deteriorating, providing a pathway for contaminated shallow groundwater to enter the lower aquifers. Such wells can be sampled at the wellhead and the water analyzed for contaminants present in nearby groundwater to test for casing leakage, or they can be inspected in detail for casing integrity. In concert or alternatively, old wells in areas of groundwater contamination can be proactively repaired or replaced according to a schedule dictated by criteria including well age, groundwater quality, and projected availability of funding over time.

During 1994, casings of six of the older wells in use on base were inspected with down-well video cameras using monies available from a fund earmarked for NAS Patuxent River infrastructure maintenance. A breach was found in one of the casings; however, the decision was made to seal all six wells, five of which were more than 50 years old, and to drill new wells to replace lost capacity. Three additional Aquia-Aquifer wells more than 50 years old have been replaced since 1994. Of the 25 currently active drinking water wells on the installation, only 4 of the 17 accessing the Aquia Aquifer are more than 50 years old. These four have been regularly and 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 with proactive replacement of selected wells as funding permits.

Because groundwater on base flows toward the river and the bay, it does not contribute to contamination of off-base groundwater; thus no pathway exists whereby on-base groundwater contamination could enter the deep aquifer via poorly sealed off-base wells.

B. Physical Hazards and/or Verified or Suspected Surface Contamination on Installation Restoration Program (IRP) Sites

The 46 IRP sites do not present on-site physical or chemical public health hazards because access is restricted or limited by fences, natural barriers, capping of the site, and/or posting. A proposal to 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 of contaminants from these sites to areas where surficial exposure might occur is not expected and/or the sites have already been adequately remediated. Current and planned remediation at NAS Patuxent River is designed to prevent future exposures. A summary of the IRP sites and ATSDR's evaluation of why they are not a public health hazard is in Appendix D. ATSDR concluded that the IRP sites represent no public health hazard from on-site physical hazards or surface contaminants. Contamination may be present from past disposal practices, but conditions exist that make it unlikely people would be exposed to these contaminants. If land use changes at any of these sites, the potential for human exposure should be reevaluated.

Conclusions and Public Health Action Plan for Possible Contamination of the Deep Aquifer

Conclusions:

1. 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.

2. Groundwater contamination on base does not currently appear to threaten deep aquifers that supply on-base or community water wells. Intervening nonpermeable layers prevent accessibility of 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.

Completed Actions:

1. NAS Patuxent River has identified on-base groundwater contamination, removed sources where appropriate, and monitors such contamination to prevent adverse impact on potable water sources.

Planned Actions:

1. Continue to sample wells that supply water from the deep aquifer and analyze according to Safe Drinking Water Standards.

2. Remediate remaining IRP sites that contribute significantly to groundwater contamination.

3. Continue to inspect older water wells and seal as necessary or prudent as an important part of a long-term maintenance program providing discretionary funds to update and upgrade NAS Patuxent River infrastructure.

Recommended Actions:

1. 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 as criteria for selecting wells and corresponding method and frequency of monitoring. Wells would 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 some wellwater and deep-aquifer contamination.

Conclusion and Public Health Action Plan for Possible Physical Hazards and/or Verified or Suspected Surface Contamination on Installation Restoration Program (IRP) Sites

Conclusion:

1. The 46 IRP sites present no on-site surficial physical or chemical public health hazard because access is restricted and no migration of contaminants is expected to areas where such exposure might occur.

Completed Actions:

1. NAS Patuxent River has proposed posting of those IRP sites to which access is otherwise insufficiently restricted. This proposal has been implemented at the direction of the NAS Patuxent River Commanding Officer.

Planned Actions:

1. NAS Patuxent River continues remediation of sites and will remove postings as appropriate when sites are removed from the IRP list.

COMMUNITY HEALTH CONCERNS EVALUATION AND HEALTH OUTCOME DATA

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 construct houses in a subdivision near the Naval Air Station, that 55-gallon drums had been discarded and buried in nearby gullies. This citizen and others asked about possible adverse health effects that could occur from such dumping. They were especially concerned about what seemed to them an unusually high number of cases of cancer occurring in the subdivision.

ATSDR made several efforts through the citizen to meet with the apparent eyewitness and have him identify the location of the alleged burials. When ultimately contacted, the person did not remember seeing any burials of drums. Even if such burials had occurred in the 1940s, the most likely way people could come in contact with contaminants would be to drink groundwater from wells that had become contaminated when drums leaked into the soil and leached into the groundwater. A community water distribution system has been in place since the first houses were built in the subdivision (18). The source of this water has been a confined aquifer, which is separated from shallow groundwater by impermeable layers. No mixing of this drinking water supply with shallow groundwater (or any contaminants that might have been in the shallow groundwater) would have been possible. Thus, persons drinking the tap water were not exposed to any contaminant that might have been in the shallow groundwater. Any exposure to groundwater 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 then covered, no surface soil would have been contaminated to permit exposure of persons. Even if dumping did occur, it appears that residents would have encountered little or no exposure to hazardous materials and would not have experienced adverse health effects.

A cancer survey was performed by the Maryland Department of the Environment, in coordination with the St. Mary's County Department of Health. The cancer incidence within the area of the Lexington Park zip code (20653) was compared with statewide incidence for the time period 1989 - 1991, the years for which data were available in a form that permits comparisons down to the zip code level. The cancer incidence for all cancers was slightly, but statistically significantly, less for Lexington Park than for the State of Maryland as a whole. (Incidence is defined as the number of new cancers per year for each 100,000 persons.) Cancer deaths per year for each 100,000 persons and incidence of breast cancer were also reviewed for the same time period and showed no statistically significant elevation for Lexington Park compared with statewide numbers (19).

Agency for Toxic Substances and Disease Registry, 1825 Century Blvd, Atlanta, GA 30345
Contact CDC: 800-232-4636 / TTY: 888-232-6348 

Department of Health and Human Services