PUBLIC HEALTH ASSESSMENT
NAVAL AIR STATION WHITING FIELD
MILTON, SANTA ROSA, FLORIDA
What is meant by exposure?
ATSDR's public health assessments are exposure, or contact, driven. Chemical contaminants disposed or released into the environment have the potential to cause adverse health effects. However, a release does not always result in exposure. People can only be exposed to a chemical if they come in contact with the chemical. Exposure may occur by breathing, eating, or drinking a substance containing the contaminant or by skin contact with a substance containing the contaminant. To acquaint readers with terminology used in this report, a glossary is included in Appendix B.
How does ATSDR determine which contaminants and exposure situations to evaluate?
ATSDR scientists evaluate site conditions to determine if people could have been (a past scenario), are (a current scenario), or will be (a future scenario) exposed to site-related contaminants. When evaluating exposure pathways, ATSDR identifies whether exposure to contaminated media (such as soil, water, air, or waste) has occurred, is occurring, or will occur through ingestion, dermal (skin) contact, or inhalation.
If exposure was or is possible, ATSDR scientists then consider how often exposure occurs and whether contamination is present at levels that might affect public health. ATSDR selects contaminants for further evaluation by comparing them against health-based comparison values. Comparison values are developed by ATSDR from scientific literature available on exposure and health effects. These comparison values are derived for each of the different media and reflect the estimated contaminant concentration that is not likely to cause adverse health effects for a given chemical, assuming a standard daily contact rate (e.g., amount of water or soil consumed or air breathed) and body weight.
Comparison values are not thresholds for adverse health effects. ATSDR comparison values establish contaminant concentrations many times lower than levels at which no effects were observed in experimental animals or human epidemiologic studies. If contaminant concentrations are above comparison values, ATSDR further analyzes exposure variables (for example, duration and frequency), the toxicology of the contaminant, other epidemiology studies, and the weight of evidence for health effects.
Some of the comparison values used by ATSDR scientists are described in the glossary in Appendix B and include ATSDR's environmental media evaluation guides (EMEGs), reference dose media guides (RMEGs), cancer risk evaluation guides (CREGs), and USEPA's reference doses (RfDs) and maximum contaminant levels (MCLs). MCLs are enforceable drinking water regulations, while CREGs, EMEGs, and RMEGs are non-enforceable, health-based comparison values developed by ATSDR for screening environmental contamination for further evaluation.
More information about the ATSDR evaluation process can be found in ATSDR's Public Health Assessment Guidance Manual at http://www.atsdr.cdc.gov/HAC/HAGM/ or by contacting ATSDR at 1-888-42ATSDR.
If someone is exposed, will they get sick?
Exposure does not always result in harmful health effects. The type and severity of health effects that occur in an individual from contact with a contaminant depend on the exposure concentration (how much), the frequency and/or duration of exposure (how long), the route or pathway of exposure (breathing, eating, drinking, or skin contact), and the multiplicity of exposure (combination of contaminants). Once exposure occurs, characteristics such as age, sex, nutritional status, genetics, life style, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes, and excretes the contaminant. Together, these factors and characteristics determine the health effects that may occur as a result of exposure to a contaminant in the environment.
There is considerable uncertainty about the true level of exposure to environmental contamination. To account for this uncertainty and to be protective of public health, ATSDR scientists typically use high-end, worst case exposure level estimates as the basis for determining whether adverse health effects are possible. These estimated exposure levels usually are much higher than the levels to which people are actually exposed. If the exposure levels indicate that adverse health effects are possible, then a more detailed review of exposure combined with scientific information from the toxicological and epidemiologic literature about the health effects from exposure to hazardous substances is performed.
Figure 4 provides an overview of ATSDR's exposure evaluation process.
ATSDR identified the on-site and off-site groundwater and surface water, sediment, and fish exposure pathways for further evaluation. Soil exposures are not a public health hazard and are not discussed in detail in this document because there is no public exposure to on-site soil and exposure to authorized workers is sufficiently infrequent that the low contaminant levels detected would not cause adverse health effects. Table 1 provides a summary of ATSDR's evaluation of potential exposure pathways.
Levels of certain VOCs exceeding ATSDR comparison values were detected in NAS Whiting Field production wells in the mid-1980s. The contamination in these wells was subsequently addressed by remedial actions. Could past exposure to the on-site water supply have resulted in adverse health effects?
Based on the following evaluation, ATSDR has determined that past consumption of on-site drinking water poses no apparent public health hazard.
Prior to installing treatment systems at each well in 1986, elevated concentrations of VOCs were detected in samples from the NAS Whiting Field distribution system and from two of the supply wells. The detected concentrations are unlikely to cause adverse health effects. The samples analyzed in 1984 did not contain detectable concentrations of VOCs. The highest concentrations of contaminants detected more than once in 1985 and 1986 were several orders of magnitude (i.e., 1,000 to 100,000 times) lower than the lowest levels known to cause adverse effects in animals. Water from the supply wells is routinely mixed, so that any contamination present would have been diluted by unaffected water. Also, because it is unlikely that VOCs reached levels high enough to cause adverse health effects, past consumption of on-site drinking water poses no apparent public health hazard.
The surficial aquifer underlying NAS Whiting Field, known as the sand-and-gravel aquifer, is the major water-bearing unit in the area. This aquifer is believed to be 200 to 350 feet thick in the vicinity of the installation. In some areas, the aquifer is separated by layers of clay or clayey sand into an upper and a lower zone. These clay lenses, which may be as much as 60 feet thick, are considered leaky confining layers. All recharge to the aquifer comes from rainfall, and the upper zone is the primary source of recharge to the lower zone, which is more productive. Groundwater also may discharge to surface water bodies, such as creeks (ABB-ES 1998a).
Underlying the sand-and-gravel aquifer is an intermediate aquifer system, which is not a significant water-producing unit in Santa Rosa County. Other layers, most notably the Floridan aquifer system, are present under NAS Whiting Field, but have not been studied during IRP-related investigations of the facility (ABB-ES 1998a).
In the western half of NAS Whiting Field, groundwater generally flows to the south-southwest (toward Clear Creek), while it flows to the southeast (toward Big Coldwater Creek) in the eastern half of the installation. In certain areas, especially in the central part of the installation, groundwater flows to the south. Wells drilled in connection with the RI have indicated the depth to the water table in certain parts of the facility. In the northwest corner of the installation, groundwater is first encountered between 65 and 115 feet below ground surface (bgs). In the southwest corner of the installation, groundwater is encountered at about 20 to 100 feet bgs (ABB-ES 1995a). Depending on the depth to groundwater in the upper zone of the aquifer, groundwater in the lower zone of the aquifer may be found from approximately 100 to 180 feet bgs or deeper (ABB-ES 1998a).
On-site Groundwater Use
Potable water is supplied to NAS Whiting Field from three wells in the industrial area, all screened in the sand-and-gravel aquifer. W-N4, known as North Well, is located at the southeast corner of the intersection of Wasp Street and Saratoga Street. It was installed in 1975 and draws water from approximately 220 feet bgs. W-W3, known as West Well, is located on the east side of Saratoga Street, between Yorktown Street and Langley Street. Installed in 1965, it draws water from 170 to 210 feet bgs. Finally, W-S2, known as South Well, was installed in 1951 and draws water from approximately 170 to 225 feet bgs. It is located east of Saratoga Street, about 750 feet south of Langley Street (ABB-ES 1998a). Figure 5 depicts the three installation supply wells. West Well and South Well were temporarily closed in late 1986 and subsequently reopened after activated carbon adsorption filtration systems were installed to address VOC contamination. As a precautionary measure, an activated carbon adsorption filtration system has also been installed on North Well.
After water is pumped through the filtration system at each well, it is pumped to the installation's water treatment plant. After treatment (e.g., flouridation), water is pumped to four on-site water towers. When the level of water in any of the towers begins to get low, the water system operator pumps water to it by turning on one or two wells, depending on need. Use of the three production wells is cycled (Auston 2000). The drinking water supply system is subject to state and federal safe drinking water requirements for water supply systems that serve more than 3,500 users (ATSDR-DHAC 1995). Since the water is fluoridated, fluoride levels are tested daily, and nitrate/nitrite is sampled annually. The state of Florida also requires that samples be analyzed for semi-volatile organic compounds (SVOCs), pesticides and polychlorinated biphenyls (PCBs), metals, and radionuclides every 3 years. North Well is also sampled for 1,2-dibromoethane semi-annually. Because of past VOC detections in NAS Whiting Field water supply wells, the installation is required by regulators to analyze samples for VOCs from each well every 6 months. However, NAS Whiting Field analyzes samples for VOCs every month (Touart 2000).
Six other wells previously supplied potable water to NAS Whiting Field. Wells W-N1, W-S1, and W-W1 were installed in 1943, when the installation was built. Most information about the design of these wells is unavailable. These three wells were abandoned in 1951 and replaced by Wells W-N2, W-S2, and W-W2, drilled within 75 feet of the original wells. The new wells, designed to draw water from over 170 feet bgs. Although records on the construction of these wells are not clear on the matter it is likely that they were installed to deliver increased yields. Because of unacceptably high levels of iron in the water they delivered, Well W-W2 was abandoned and replaced by Well W-W3 in 1965, and Well W-N2 was abandoned and replaced in 1975. Well W-N3, a test well, also produced water with unacceptably high levels of iron, and therefore the well known as Well W-N4 replaced Well W-N2. Well W-S1 was immediately adjacent to Well W-S2, Wells W-W1 and W-W2 were near the intersection of Ranger Street and Langley Street, and Wells W-N1, W-N2, and W-N3 were near the intersection of Hornet Street and Saratoga Street. (ABB-ES 1998a; Geraghty & Miller 1984, 1986)
Nature and Extent of Contamination
VOCs, SVOCs, metals, and pesticides have been detected in groundwater samples collected from various sites under investigation at NAS Whiting Field. Pesticides and metals do not tend to be transported significant distances by groundwater flow, as they adhere to soil particles. Pesticides have only been encountered at a few sites. Appendix A provides the locations and levels at which chemicals have been detected in on-site groundwater. The contaminants of greatest concern are two classes of VOCs, which originate from petroleum products and solvents, respectively.
Benzene, toluene, ethylbenzene, and xylenes (or BTEX compounds, which are petroleum byproducts) affect much of the groundwater underlying the installation. A primary source of these contaminants is thought to be Site 4, the North AVGAS Tank Sludge Disposal Area, also an UST site. There is an ongoing effort to remove petroleum products from the soil at the site, which is located near the North Field Maintenance Hangar (Site 32). Plumes of BTEX compounds in the upper and lower zones of the aquifer are located near the North Field Maintenance Hangar and South Field Maintenance Hangar (Site 30, located near the South AVGAS Tank Sludge Disposal Area and associated USTs, Site 7), as well as in groundwater at Site 5 (the Battery Acid Seepage Pit), not far from the Midfield Maintenance Hangar (Site 33). Levels of benzene thought to originate from Site 4 (as suggested by testing to "fingerprint" the contamination) have been detected in the lower zone of the aquifer at Sites 15 and 16, just northeast of Clear Creek (Martin 2000).
There are also thought to be plumes of the solvent trichloroethylene (TCE) and its breakdown products affecting groundwater underlying NAS Whiting Field. The source of this contamination is not known. Until 1985, however, TCE was used as a cleaner on site, particularly in the maintenance hangar areas (Martin 2000). TCE and its breakdown products are present in the upper and lower zones of the aquifer near the North Field and South Field Maintenance Hangars, in the upper zone near the Midfield Maintenance Hangar, and in the lower zone at Sites 15 and 16 (both disposal areas). The compounds have also been detected at low levels in several samples from the upper zone of the aquifer and one groundwater sample from the lower zone, near Sites 35 through 37 (facilities used for public works, auto repair, and painting) and in the upper zone groundwater at Sites 11 and 13 (both disposal areas).
The first sample analyzed from the installation's water distribution system (i.e., the system and not an individual supply well) for which records are available was in February 1984 and did not contain detectable levels of VOCs, SVOCs, or pesticides (Geraghty & Miller 1984). Records from FDEP's Potable Water Section do not show a February 1984 sample, but do show a sample from the NAS Whiting Field water distribution system collected in March 1984 that did not contain any detectable levels of contaminants (Touart 2000). It is possible that the two reports of sampling in 1984 are actually referring to the same sample.
A sample collected from South Well, near Site 5, on November 1, 1985, contained 4 ppb of TCE. A sample from the installation's water distribution system was also collected that day and contained 7 ppb of TCE, exceeding the ATSDR comparison value (i.e. screening value) of 5 ppb (Geraghty & Miller 1985). According to state records, the next samples collected at the installation were from South Well, in which 4 ppb of benzene was detected on March 21, 1986, 2 ppb of benzene was detected on April 21, 1986, 49 ppb of vinyl chloride was detected on May 21, 1986, and 4 ppb of benzene was detected on July 21, 1986. These concentrations exceed ATSDR comparison values for benzene and vinyl chloride, respectively, as well as state drinking water standards. For this reason, South Well was shut down on August 18, 1986. Although the well was not in use at the time, samples from South Well collected from October 1986 through January 1987 contained levels of benzene reaching 17 ppb. Vinyl chloride was not detected in any samples from South Well other than the one analyzed in May 1986 (Touart 2000; Hendon Engineering Associates 1989).
NAS Whiting Field documents indicate that the first sample taken directly from West Well, on September 14, 1986, contained 7.9 ppb of TCE. West Well was closed 11 days later. The level of TCE measured in the well while it was closed reached 10.5 ppb, but after a filtration system was installed, only trace levels of TCE were detected, and the well reopened December 1, 1986. No contaminants were detected in North Well in the 1980s during six sampling events, other than a trace level of toluene in one sample (Hendon Engineering Associates 1989).
The first recorded sample taken from the distribution system subsequent to the November 1985 sample was collected in October 1986, at which time only North Well was operating. The sample did not contain detectable levels of any contaminants. A January 7, 1987, distribution system sample contained 7.8 ppb of benzene, which exceeds both the Florida drinking water standard and the ATSDR comparison value (Touart 2000; Hendon Engineering Associates 1989).
In the 1990s, VOCs were detected sporadically in treated water leaving one of the three supply wells. 1,1-Dichloroethene was detected in the West Well at 0.8 ppb in January 1996, 0.9 ppb in July 1996, 0.75 ppb in March 1997, and 0.7 ppb in April 1997. 1,2-Dichloroethane was detected at 0.51 ppb in a sample collected on August 5, 1994, (noted as "West Well and South") and at 0.52 ppb in a sample from North Well collected on August 12, 1994. 1,2-Dichloroethane was not detected in subsequent samples from any location at concentrations above the detection limit of 0.5 ppb (Touart 2000). In January 1999, 1.2 ppb of bromodichloromethane and 0.7 ppb of dibromochloromethane were detected in treated water leaving North Well (Aqua Tech 1999a). However, they were not detected in July 1999 (Aqua Tech 1999b). While these VOCs have been detected at concentrations exceeding ATSDR's comparison values in the 1990s, they have not exceeded federal or state safe drinking water standards.
Radionuclides and VOCs were sampled in all three wells in January 1999, and SVOCs, pesticides and PCBs, and metals were sampled in August 1999. Only benzo(a)pyrene, detected at 0.03 ppb in North Well and West Well and 0.02 ppb in South Well, was detected above ATSDR's comparison values, but below federal and state safe drinking water standards. Due to these detections, samples from all three wells will be analyzed for benzo(a)pyrene quarterly for 1 year and then annually for 3 years. October 1999 sampling did not reveal measurable levels of the contaminant in any of the wells (Touart 2000).
Evaluation of Potential Public Health Hazards
In the mid-1980s, low levels of VOCs exceeding ATSDR comparison values were detected in individual production wells and, in two instances, in the water distribution system. Samples collected in 1984 from the distribution system did not contain any VOCs. Since vinyl chloride was only measured in South Well in one of five 1986 samples, and water from South Well was mixed with water from North and West Wells prior to distribution, it is unlikely that anyone was exposed to vinyl chloride at doses of health concern. Moreover, within 3 months of the vinyl chloride detection, South Well was temporarily deactivated. Other VOCs were not detected at levels of health concern, even for the worst-case scenario which assumes that an individual consumed (unmixed) water containing VOCs at the highest detected concentrations for a number of years.
The highest detected concentrations of these VOCs would result in doses several orders of magnitude (i.e., 1,000 to 100,000 times) lower than the lowest doses at which they were found to cause health effects in available animal studies. It is unlikely that VOC concentrations would have been high enough to cause adverse health effects prior to the mid-1980s. Thus, past consumption of on-site drinking water poses no apparent public health hazard. Current and future consumption of on-site drinking water poses no public health hazard because levels of VOCs are monitored monthly to ensure that the water meets all state and federal safe drinking water standards. ATSDR is available to review the results of future sampling of installation supply wells.
Has contaminated groundwater from NAS Whiting Field moved off site, and does it impact any municipal or private wells in the vicinity?
Consumption of water from off-site wells poses no public health hazard because exposure to contaminated water has not occurred and is unlikely to occur in the future. The U.S. Navy has performed a survey of all private and municipal wells within 4 miles of NAS Whiting Field. In order to insure that no wells exist that have not been located by surveys to date the Navy continues to make efforts to ascertain the location of nearby private wells. In ongoing environmental investigations, The U.S. Navy is continuing to delineate groundwater contamination plumes originating at NAS Whiting Field. If it appears that any private wells might be in the path of contaminant migration, ATSDR recommends that the U.S. Navy develop and implement a plan for monitoring these wells and for addressing any detected contamination. At present, the only location in which groundwater contamination appears to be migrating off site is to the east of Site 13. A nearby home served by a private well did not contain any VOCs. To date, no VOCs have been detected in a monitoring well about 300 feet upgradient of the home. If future sampling and hydrogeological investigations indicate plume movement towards private wells, ATSDR recommends that the private wells be sampled.
Off-site Groundwater Use
Milton's public water supply system relies on six wells screened in the sand-and-gravel aquifer. Wells 1, 2, and 3 supply potable water to areas east of NAS Whiting Field, including residential areas on East Gate Road and along Red Bug Road. Wells 4, 5, and 6 supply potable water to north Milton and suburban areas to the north and west of Milton. All of the Milton water supply wells are more than 2.5 miles southwest of NAS Whiting Field (ABB-ES 1998a).
Potable water is supplied to areas to the south and west of NAS Whiting Field by the Point Baker water supply system, which operates four wells. Point Baker Well 4 is northwest of the installation and serves the Allentown area. Since it is not downgradient of NAS Whiting Field, this well is not expected to be affected by site-related contamination. Point Baker Well 2 is dry. Point Baker Wells 1, 3, and 5 are connected to each other by pipelines and serve the population to the south and west of NAS Whiting Field (ABB-ES 1998a). Well 1 is about 2.5 miles due west of the installation, while Wells 3 and 5 are about 1 mile southwest and about 3 miles southwest of the facility, respectively. All wells are screened in the sand-and-gravel aquifer.
In 1995, a survey of wells within 4 miles of NAS Whiting Field identified 64 domestic wells, 5 agricultural wells, and 61 wells used for landscaping, as well as the nine public supply wells previously discussed. Four domestic wells and one well used for landscaping were identified within 0.5 miles of the installation. All of these wells are located due west of the industrial area, in the vicinity of the intersection of Route 87A and Route 87. One well used for agriculture was identified just under 1 mile southeast of NAS Whiting Field. An additional well, used for landscaping, is located between 0.5 miles and 1 mile west of the boundary of the installation. In the area between 1 and 2 miles away, there are an additional 10 domestic wells, 8 landscape wells, and 1 agricultural well. Between 2 and 3 miles from the facility, there are 14 domestic wells and 13 landscape wells. Finally, there are 36 domestic wells, 38 landscape wells, and 3 agricultural wells located between 3 and 4 miles from NAS Whiting Field. (ABB-ES 1998a)
During the well survey, the Public Works Department of the city of Milton, the Point Baker water supply office, and the Northwest Florida Water Management District were contacted. Created in 1976, the District requires homeowners to obtain a permit before drilling a well. Prior to 1976, there was no requirement that private wells be permitted by or registered with any government agency. However, personnel overseeing remediation at NAS Whiting Field believe that all private wells that may be located near installation groundwater contamination have been identified, as visual inspections have been conducted of nearby private properties to look for private wells during groundwater sampling events near installation boundaries (Martin 2000). Two additional wells were identified this way, and they were sampled subsequent to the well survey. One is located just east of Site 13, off East Gate Road, and the other is west of Clear Creek (Durbin 2000).
Nature and Extent of Contamination
There is only one known area--east of Site 13--in which groundwater contamination originating at NAS Whiting Field is thought to be migrating off site. In 1997, 1,2-dichloroethene was detected in samples from an off-site monitoring well about 1,200 feet southeast of Site 13's southeastern corner, an estimated concentration of 3 ppb in June 1997, and an estimated 2 ppb in late October 1997. In April 1998, NAS Whiting Field sampled tap water from a home served by a private well on East Gate Road that is about 600 feet northeast (crossgradient) of the well in which the 1,2-dichloroethene was detected. No VOCs were detected in the tap water sample. In addition, no VOCs have been detected in a monitoring well about 300 feet northwest (upgradient) of the home and about 800 feet north of the well in which 1,2-dichloroethene was detected.
After VOC contamination was detected in two NAS Whiting Field supply wells in 1986, the Santa Rosa County Health Department sampled certain wells in the vicinity of the installation. Three wells about a mile or more from the installation were sampled on October 8, 1986, as were Milton Wells 1 through 5 and Pace Wells 3 through 5. The Milton and Pace supply wells are more than 4 miles southwest of the installation. No organic contaminants were detected in any of the wells, other than a trace of bromoform found in Milton Well 4 (Hendon Engineering Associates 1989).
The Santa Rosa County Public Health Unit has sampled, at the homeowner's request, a private well just under 0.5 miles west of the center of the installation, off Route 87. No VOCs or SVOCs were detected (Florida DHRS 1992). NAS Whiting Field has also sampled a private well downgradient of the installation, to the west of Clear Creek, in response to a request from a homeowner. No VOCs were detected in the May 1997 sample. ATSDR has not identified any other sampling of off-site private wells. Municipal water distribution systems are sampled regularly, as required by the Safe Drinking Water Act.
Evaluation of Potential Public Health Hazards
NAS Whiting Field is planning to install and sample groundwater monitoring wells to continue to fully delineate the extent of all groundwater contamination plumes (Martin 2000). The installation has also performed a well survey and continues to make efforts to ascertain the location of nearby private wells. The only location in which groundwater contamination from NAS Whiting Field is thought to be migrating off site is southeast of Site 13. Tap water was collected and analyzed from one house (located near the off-site contamination) using a private well. The water did not contain any VOCs. Since no exposure to contaminants at levels of health concern has been found or is expected, ATSDR concludes that off-site groundwater contamination poses no apparent public health hazard. However, if any VOCs are detected in the future in the monitoring well east of Site 13 and about 300 feet northwest (upgradient) of the home, ATSDR recommends that the private well be resampled.
ATSDR recommends that the U.S. Navy fully delineate the extent of the groundwater plumes near installation boundaries to determine whether any private wells might be in the path of contaminants migrating from NAS Whiting Field. If it is appears that any private wells might be affected, the U.S. Navy should develop a plan to monitor these wells and address any detected contamination to ensure that no exposures occur to contaminant levels of health concern.
Could exposure to potentially-contaminated surface water, sediment, and/or fish in the Clear Creek floodplain pose public health hazards? Should public recreational use of this area be restricted?
After reviewing available information about exposure to the Clear Creek floodplain and associated sampling data, ATSDR concluded that contaminants in surface water and sediment pose no apparent public health hazard. Since Clear Creek is difficult to access, recreational use is thought to be limited. While recreational users of the area might come into contact with selected contaminants at concentrations exceeding CVs, detected concentrations of contaminants are not high enough to cause adverse health effects to individuals who come into contact with them briefly and infrequently. Thus, ATSDR does not recommend that recreational use of Clear Creek or its floodplain be curtailed.
No fish tissue samples are available. However, contaminants that might accumulate in fish have only been detected in sediment samples sporadically and therefore are not expected to have accumulated in fish to levels of health concern. According to information received by ATSDR, any fishing that may occur in Clear Creek is infrequent. Occasional consumption of fish from the creek, like exposure to surface water and sediment, is therefore not expected to result in adverse health effects.
Nature and Extent of Contamination
Surface water samples from Clear Creek analyzed in 1990, 1992, and 1997 have revealed concentrations of benzene, bromodichloromethane, dibromochloromethane, arsenic, cadmium, manganese, and thallium at levels exceeding drinking water comparison values. Sediment samples from the Clear Creek floodplain have contained benzo(a)pyrene, bis(2-ethylhexyl)phthalate, dieldrin, Aroclor-1260, arsenic, cadmium, iron, and lead at concentrations exceeding soil comparison values. See Appendix A for the maximum detected concentrations of these contaminants. The floodplain may be affected by contaminants being transported down New "A" Ditch or New "M" Ditch, contaminants in groundwater that recharges the creek, and/or contaminants that were present in four drums that were removed from the creek bed in 1993. No fish sampling data are available.
Evaluation of Potential Public Health Hazards
To evaluate whether past, current, or future hazards might be associated with Clear Creek contamination, ATSDR evaluated contaminant levels present in surface water and sediment and the potential for exposure to these media. Based on this review, ATSDR concluded that past, current, and future use of the area pose no apparent public health hazard.
Signs are posted around Clear Creek within NAS Whiting Field property to warn people of contamination detected in the floodplain (Holland 2000a). Nonetheless, recreational users may come into contact with certain site-related contaminants at levels exceeding drinking water and/or surface soil comparison values on and off site. Detected concentrations have been compared to drinking water and soil comparison values because no surface water or sediment comparison values are available.
The available comparison values assume daily exposure to contaminants in water and soil. However, Clear Creek is not used as a drinking water source. Recreational exposures (via dermal contact or ingestion) to contaminants in Clear Creek and its floodplain are expected to be incidental, infrequent and of shorter duration than the long-term, frequent exposure scenarios assumed for deriving drinking water and soil comparison values. Exposures to the levels of contaminants detected in surface water and sediment are not expected to cause adverse health effects.
ATSDR has been advised that Clear Creek is difficult to access and is infrequently used for fishing, if used at all. Contaminants that might accumulate in fish (pesticides and PCBs, for example) have only been detected sporadically at concentrations above CVs. Based on the infrequency of their detection, it is not expected that these contaminants have accumulated in fish at levels that would be of health concern to people occasionally consuming the fish.
NAS Whiting Field is planning to conduct further surface water and sediment sampling in the Clear Creek floodplain, known as Site 39. ATSDR is available to review the findings of future evaluations and will revise its conclusions, if appropriate. After an RI/FS is completed, the installation will select a remedy to address contaminants that have affected the floodplain. This remedy is expected to prevent future exposure to contamination.
During the site visits and in the conduct of the public health assessment, ATSDR met with Navy and NAS Whiting Field personnel, state and federal regulators and local government officials to discuss community concerns. No community health concerns associated with NAS Whiting Field have been brought to ATSDR's attention.
A community relations plan for NAS Whiting Field provides guidance for involving the community and other interested parties in the decision-making process for selecting remedial alternatives and keeping the community informed about site-related activities. Public meetings are held to inform citizens of ongoing remedial activities and to solicit their input. NAS Whiting Field officials have also given community presentations and are available to discuss any concerns that community members have. The public may review site-related documents, including RI reports and correspondence relating to cleanup activities, at a repository at the Milton Branch of the West Florida Regional Library (U.S. Navy 1995). A Restoration Advisory Board composed of community members and representatives of the U.S. Navy, U.S. EPA and FDEP meets regularly to discuss and review ongoing activities at NAS Whiting Field.
If, during the public health assessment process or after, concerns are raised, ATSDR will provide assistance in providing appropriate answers.
ATSDR recognizes that infants and children may be more sensitive to exposures than adults in communities with contamination in water, soil, air, or food. This sensitivity is a result of a number of factors. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. Children are shorter than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care. Therefore, ATSDR is committed to evaluating their special interests at sites such as NAS Whiting Field as part of the ATSDR Child Health Initiative.
ATSDR has attempted to identify populations of children in the vicinity of NAS Whiting Field. Approximately 166 children under the age of 6 years (approximately 12 percent of the total population) live within 1 mile of the installation (as calculated by ATSDR from 1990 U.S. Census data using an area-proportion spatial analysis technique). An on-site childcare center, which opened in 1988, serves about 60 children (NASWF 1999). There are no schools within a mile of the installation.
Like other people living or working at or in the vicinity of NAS Whiting Field, children may contact contaminated site media. As discussed in the "Evaluation of Environmental Contamination and Exposure Scenarios" section of this PHA, past, current, and future exposures for children only include contact with surface water and sediment during recreational use of the Clear Creek floodplain.
In evaluating whether children may experience adverse health effects through past, current, or future exposures to site contaminants, ATSDR used very conservative assumptions that overestimate the levels of actual exposure. ATSDR concluded that exposure to site contamination does not pose unique health hazards for children. This conclusion is based on ATSDR's exposure evaluation and the fact that detection of chemicals above comparison values, which are only screening values, does not necessarily imply that harmful exposure occurred.
During recreational use of Clear Creek, children may be and may have been exposed to contaminants detected in surface water or sediment. However, children would only have the opportunity to come into contact with these media briefly and infrequently. No surface water and sediment comparison values are available; therefore, contaminant concentrations detected in these media were compared to drinking water and surface soil comparison values, respectively. These comparison values are derived using conservative assumptions about daily exposures. Recreational use of the creek would occur less frequently than assumed by the comparison values. Exposure to the maximum contaminant concentrations detected in surface water and sediment are not expected to result in adverse health effects.
Although no fish tissue data are available, contaminants that might accumulate in fish have only been detected in sediment samples sporadically. Therefore, fish are not expected to be contaminated at levels of health concern to children infrequently consuming them.