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PUBLIC HEALTH ASSESSMENT

COMMENCEMENT BAY, SOUTH TACOMA FIELD
(a/k/a COMMENCEMENT BAY, SOUTH TACOMA CHANNEL)
TACOMA, PIERCE COUNTY, WASHINGTON

ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

In Appendix - B, the contaminants of concern associated with the South Tacoma Field site are listed in tables. Contaminants of concern are selected from sampling data by comparing the maximum contaminant concentrations to comparison values, such as Environmental Media Evaluation Guides (EMEGs), Cancer Risk Evaluation Guides (CREGs), and other relevant health-based guidelines. The selected contaminants of concern are not necessarily contaminants that will cause adverse health effects from exposure, but rather are contaminants to be evaluated further in the Public Health Implications section of this Public Health Assessment.

EMEGs are estimated contaminant concentrations at which daily exposure would be unlikely to result in noncarcinogenic health effects. The oral EMEG for drinking water exposure is calculated from the ATSDR Minimal Risk Level (MRL), based on a child body weight of 10 kilograms (kg), and a child water ingestion rate of 1 liter per day. For soil exposure, the oral EMEGs are derived from MRLs based on a child body weight of 10 kg and child soil ingestion rate of 200 milligrams (mg) per day. ATSDR developed MRLs to evaluate health effects of contaminants commonly found at hazardous waste sites. MRLs are estimates of daily exposure to contaminants below which noncarcinogenic health effects are unlikely to occur. If a MRL does not exist for a specific contaminant, a Reference Dose Media Evaluation Guide (RMEG) is calculated from EPA Reference Dose (RfD). Similar to EMEGs, RMEGs are estimated contaminant concentrations at which daily exposure would be unlikely to cause a noncarcinogenic health effect.

CREGs are estimated contaminant concentrations at which exposure would be unlikely to result in more than 1 excess cancer in 1 million persons exposed for a lifetime of 70 years. These comparison values are derived from EPA cancer slope factors based on an adult body weight of 70 kg and an adult water ingestion rate of 2 liters per day for drinking water exposure and an adult soil ingestion rate of 100 mg per day for soil exposure.

Toxic Chemical Release Inventory

To identify possible facilities that could contribute to contamination found at the South Tacoma Field site, WDOH searched the Toxic Chemical Release Inventory (TRI) Database for all available years (1987 through 1993) by zip code (98409). TRI is developed by EPA from information about chemical releases to air, water, or soil, as provided according to law by certain industries. TRI contained information for 70 documented instances of point and non-point air releases near the South Tacoma Field site area.

Site contamination involves primarily heavy metals, polychorinated biphenyls, and polycyclic aromatic hydrocarbons in surface soils, surface water, and sediments. The review of the data on air releases indicated that the majority of releases are of volatile organic compounds which volatilize readily in air. However, data did included several releases of metals. The annual volume of these releases were at low levels unlikely to contribute significantly to contamination at the South Tacoma Field site.

A. On-site Contamination

1. Soil Investigation

For purposes of the remedial investigation, the South Tacoma Field site was divided into seven sampling units based on historical activities, and the potential for those activities to cause environmental contamination. Each sampling unit, with the exception of the Tacoma City Light unit, was designated as high, medium, and low relating to the perceived-risk from contamination detected in on-site surface soils. These perceived-risk designations formed the basis for sampling grid sizes. The high-perceived risk areas had the smallest grid size and low-perceived risk areas had the largest grid size.

Small 70-foot grid squares were established in the 2 sampling units with high-perceived risk levels, the Amsted and BNR Dismantling Yard units. The medium 150-foot grid squares and large 235-foot grid squares were associated with the medium- and low-perceived risk areas, respectively. Medium grids were established in the TIP and Airport units, and large grids in the Swamp/Lakebed and BNR Railyard units.

Surface Soil Investigation

Soil investigations were conducted in two phases at the South Tacoma Field site during 1991 and 1992; each phase included the collection of both surface and subsurface soil samples. Phase 1 Soil Investigation was designed to identify and delineate contaminant hotspot throughout the sampling area. A surface soil sample (taken from the upper six inches of soil) was collected from each medium and large grid square established in the sampling units: TIP, Airport, Swamp/Lakebed, and BNR Railyard. From each small grid square in the Amsted and BNR Dismantling Yard units, a composite of five surface soil samples were collected from upper six inches of soil. No surface soil samples were collected from the Tacoma City Light unit since the area is completely paved.

During Phase I Soil Investigation, a total of 622 surface soil samples were collect within the site. In additional, 11 background samples were taken from 10 off-site locations within the South Tacoma Channel. About 20 percent of the surface soil samples were analyzed for boron, cyanide and compounds on the EPA Hazardous Substance List including a series of inorganic chemicals, volatile and semi-volatile organic compounds, pesticides, and polychlorinated biphenyls (PCBs). The remaining samples were analyzed for boron, inorganic chemicals, polycyclic aromatic hydrocarbons (PAHs). The background samples were tested for total cyanide, inorganic chemicals, volatile and semi-volatile compounds, and PCBs.

Phase II Soil Investigation involved the collection of 75 additional surface soil samples to provide information on the distribution of selected chemicals in surface soils. Sample locations included the BNR Railyard sampling unit from which 37 surface soil samples were collected; Swamp/Lakebed, 19 samples; TIP, 8 samples; Airport, 7 samples; and Pioneer Builders Supply property, 4 samples. Surface soil samples were analyzed for inorganic chemicals and PAHs, and some of these samples were also tested for volatile and semi-volatile organic compounds, pesticides and PCBs.

Phase I and Phase II Soil Investigations results revealed that site contamination consist of various inorganic chemicals, volatile and semi-volatile organic compounds including PAHs, PCBs, and dioxins in surface soils. In Appendix - B, Table 1, the contaminants of concern selected for on-site surface soils are reported along with the range of detection, corresponding sampling unit and contaminant comparison value.

Subsurface Soil Investigation

During Phase I Soil Investigation, subsurface soil sampling was conducted at the Tacoma City Light unit and Pioneer Builders Supply property. Thirty-two subsurface soil samples were gathered from eight dry wells on the Tacoma City Light unit. Twenty-seven samples were collected from five borings ranging in depth from 15 to 50 feet; the borings were located in the area of the former tank excavation area on Pioneer Builders Supply property.

Subsurface soil samples collected from the Tacoma City Light unit were analyzed for chemicals on the EPA Hazardous Substance List. Pioneer Builders Supply property samples were analyzed for volatile and semi-volatile organic compounds, and PCBs. In addition, eight of these subsurface soil samples from the Pioneer Builders Supply property were randomly selected and analyzed for EPA Hazardous Substance List parameters including boron.

Additional subsurface soil sampling was performed during Phase II Soil Investigation to better characterize the extent of subsurface soil contamination. A total of 305 subsurface soils were collected from 92 borings located throughout the site. At the Swamp/Lakebed and Amsted units, borings were sampled at depths of 2, 7, 12, and 17 feet below ground surface. Subsurface soil samples from the Airport, BNR Dismantling Yard, and TIP units were collected at depths of 2, 7, and 12 feet below ground surface. Borings near dry wells at the Tacoma City Light unit were sampled at depths of 10, 12, and 14 feet below ground surface. Pioneer Builders Supply property borings were sampled at 5-foot intervals of 0, 5, 10, 15, 20, 25, 30 feet below ground surface. Phase II subsurface soil samples were analyzed for inorganic chemicals and PAHs. In addition, a subset of samples was analyzed for volatile and semi-volatiles organic compounds, pesticides, and PCBs.

Contaminants detected in subsurface soils consist of inorganic chemicals and semi-volatile organic compounds including PCBs and PAHs. The contaminants of concern in on-site subsurface soils are listed in Appendix - B, Tables 2 and 3 along with ranges of detection by sampling unit or area, and contaminant comparison values.

2. Air Dispersion Modeling Investigation

The potential migration of airborne contaminants was assessed using air dispersion modeling. The investigation was conducted in two phases. Using existing surface soil data prior to the remedial investigation, the first phase involved a preliminary dispersion modeling to confirm the assumption that off-site impacts were low and support the determination that monitoring was not warranted. The second phase predict airborne contaminant concentrations based on surface soil data obtained during the Phase I Soil Investigation and conservation assumptions regarding future site conditions.

Air Dispersion Modeling Investigation concluded that current site conditions which included extensive vegetation cover and limited public access, reduce the potential exposure from the airborne pathway. In addition, modeling estimated that airborne concentrations of contaminants were considered to be less than EPA industrial exposure screening levels.

3. Blackberry Investigation

The Blackberry Investigation evaluated the potential for contamination of blackberries through either root uptake of inorganics from soil or inorganics adhesion to the fruit surface due to atmospheric deposition of soil dust from on- and off-site sources. On August 16 and 17, 1991, composite blackberry samples were collected from each of the six on-site sampling units, as well as from three off-site locations. Samples were split; one-half of the sample was analyzed unwashed and the other half was washed prior to analysis. The analytical results from unwashed and washed composite samples were used to evaluate the extent, if any, to which root uptake and atmospheric deposition have resulted in inorganic contamination in or on the blackberries. Samples were analyzed for the inorganics: antimony, arsenic, beryllium, boron, cadmium, chromium (total), copper, lead, mercury, nickel, selenium, silver, thallium, and zinc.

In general, low concentrations of inorganics were detected in blackberries collected from both on- and off-site locations. From the BNR Railyard unit, the unwashed blackberry sample contained copper at 3.7 mg/kg and boron at 4.4 mg/kg. Boron was also detected at 7.0 mg/kg in the washed sample from BNR Dismantling Yard unit. At the Swamp/Lakebed unit, arsenic was detected in the unwashed sample at 0.5 mg/kg and in the washed sample at 0.43 mg/kg, and zinc was detected in the unwashed sample at 4.10 mg/kg and at 3.9 mg/kg in the washed sample. In addition, lead was found at 0.22 mg/kg in the washed sample. (Note that low concentrations of lead were detected in the deionized water used to wash the sample.) The unwashed blackberry sample from the Airport unit contained chromium at 1.0 mg/kg and zinc at 11.4 mg/kg. The unwashed blackberry samples from the TIP unit had an arsenic concentration of 2.9 mg/kg.

The investigation concluded that inorganics were detected more frequently in blackberry samples collected from off-site locations compared with those collected from on-site locations, and concentrations of inorganics detected in on-site samples were similar to concentrations found in off-site samples. In comparing results for unwashed and washed blackberry samples from a particular sampling location, concentrations for washed samples were generally slightly lower than concentrations for unwashed samples. This results suggest that atmospheric deposition is a potential source of inorganics found in blackberry samples from on- and off-site locations.

Without actual blackberry consumption data for the site, it is difficult to develop accurate comparison values to determine contaminants of concern in blackberry samples. Data on homegrown raw strawberry consumption rates are available. The average homegrown raw strawberry consumption rate of 12.3 grams of strawberries per day was used to calculate the comparison values for contaminants in blackberries. Note that this rate may not be representative of the annual consumption rate since the value was derived from a 3-day consumption rate (30). The rate is likely to be similar to the blackberry consumption rate during the growing season, but may overestimate the annual consumption rate for fresh blackberries. In turn, the rate may possibly underestimate the annual consumption rate should blackberries be frozen or preserved as jam and jelly to be used year-round. However, should blackberry consumption be similar to that of homegrown raw strawberries, the concentrations of contaminants detected in blackberries fall below the calculated comparison values with the exception of arsenic and copper. A refined look at these concentrations reveals that estimated daily exposure doses for children and adults are below health-based guidelines for arsenic and copper. Contaminants found in on-site blackberry samples are not considered as contaminants of concern.

4. Soil-gas Investigation

A limited soil-gas investigation was conducted to characterize soil-gas contamination in the vicinity of the former underground storage tanks removal excavation on the Pioneer Builders Supply property. The tanks were located north of the Pioneer Builders Supply facility in the southeastern portion of the site. Soil-gas sampling consists of the collection of 35 samples from 24 locations along the soil sampling grids typically at depths of 6 and 13 feet below soil surface. Nine samples locations were taken within 50 feet of the excavation site and 2 locations were within the excavation site. The remaining samples were collected within 100 feet of the excavation site.

Analysis of the soil-gas samples detected low-to-no concentration of hydrocarbons and halogenated volatile organic compounds. Based on the soil-gas investigation, no evidence of significant or widespread soil-gas contamination was detected surrounding the removal excavation site near Pioneer Builders Supply.

5. Groundwater Investigation

The Groundwater Investigation consisted of sampling from 26 on-site monitoring wells, 5 upgradient wells, and 5 background wells. Although several wells are located adjacent to the site boundary, the 26 monitoring wells are considered to be on-site for purposes of this groundwater investigation (Appendix - A, Figure 3). Groundwater samples were collected for four quarters; the first quarter sampling occurred during April 1991, second quarter during July and August 1991, third quarter during October and November 1991 and the fourth quarter during January and February 1992. The on-site monitoring wells were sampled during all four quarters, while the upgradient and background wells were sampled only during the second and fourth quarter (25).

The investigation of water quality focused on the Upper Layer A aquifer with the sampling of 21 on-site monitoring wells which access this uppermost aquifer zone. In addition, there are two depth-staggered well clusters consisting of three wells per cluster completed in Upper Layer A, Lower Layer A, and Layer C aquifers at both locations. The total construction depths reported for monitoring wells completed in the Upper Layer A aquifer range from 18 to 48 feet. The two monitoring wells installed in the Lower Layer A aquifer are both at a total construction depth of 127.5 feet, and the two wells in the Layer C aquifer are at total construction depths of 195.5 and 200.5 feet.

Groundwater samples were analyzed for chemicals on EPA Hazardous Waste List such as pesticides, inorganic chemicals, volatile and semi-volatile organic compounds including PAHs and PCBs. Concentration of inorganic chemicals, as well as volatile and semi-volatile organic compounds were detected in on-site groundwater. However, no PCBs or pesticides were found. Table 4 in Appendix - B reports the contaminants of concern observed in on-site groundwater with the ranges of detection and contaminant comparison values.

6. Surface Water and Sediment Investigation

Surface Water

Surface water runon comes from two upgradient drainage sub-basins which discharge through two storm drains on the northwest portion of the site into a channel. The surface water channel traverses along the western border of the site, running from north to south. The channel is comprised of two areas with permanent standing water, an area adjacent to the storm drain outfall and a remnant of a former swamp. The channel elevation from north to south drops five feet at a consistent grade along the south half of the channel. This south half of the channel consists of two low sections occurring at and south of the former swamp remnant. The channel eventually turns east then continues south again parallel to Madison Street where the channel crosses the southern boundary. The channel continues off-site at Madison Street to about 150 feet north of the South 56th Street at which point the channel enters a 72-inch storm drain.

Surface water from the site combines with other sources of surface water and discharges to Flett Creek about 1.4 miles south of the site. About three miles downstream, the Flett Creek empties into Chambers Creek and eventually into marine waters of Puget Sound.

The investigation of surface water quality involved the collection of 41 surface water samples from about 29 on-site locations. Surface water samples were collected during three separate sampling events, dry, transitional, and wet seasons. Over the one-year monitoring period, 11 monthly runon surface water samples were collected from the storm drain outlet south of city of Tacoma pump station and 10 monthly surface water runon samples from the manhole for South 38th Street storm drain, 50 feet west of the on-site surface water channel. Four biweekly surface water runoff samples were collected from the surface water channel at the site boundary; no surface water flow was present during 22 possible sampling events. In addition, 11 storm event surface water samples were collected from each of the 2 runon sampling locations and one storm event surface water sample from the runoff sampling location.

On-site and runoff surface water samples were analyzed for chemicals on EPA Hazardous Waste List with the addition of boron, cyanide, and fecal bacteria. The runon surface water samples were analyzed for inorganics, boron PAHs, and fecal bacteria. Summarized in Appendix - B, Table 5 are the contaminants of concern detected in runon, on-site, and runoff surface water samples.

Sediments

During the 3 sampling events, transitional, dry, and wet seasons, 69 sediment samples were also collected from the 29 surface water sample locations within the on-site surface water channel. Analysis of the on-site sediment samples involved inorganics, boron, cyanide, PAHs, VOCs, semivolatile compounds, pesticides, and PCBs. Table 6 in Appendix - B lists the contaminants of concern in on-site sediments with maximum concentrations and comparison values.

B. Off-site Contamination

1. Soil Investigations

Surface Soil Investigation

During the Phase I Soil Investigation, 11 surface soil background samples were collected from 10 off-site locations situated north and south of the site. These samples were analyzed for total cyanide, inorganic chemicals, volatile and semi-volatile compounds including PAHs, PCBs, and pesticides.

Analytical results indicated that generally inorganic concentrations detected in background surface soil samples fall within the common concentration range for inorganics naturally occurring in soil. Low concentrations of organics were detected in background samples. PAHs were observed at concentrations ranging from 0.01 to 0.1 mg/kg. Probable carcinogenic PAHs were identified in 8 of the 11 background samples with the total probable carcinogenic PAH concentrations ranging from 0.033 to 0.459 mg/kg. Two volatile compounds with concentrations below 0.7 mg/kg were detected and three semi-volatile compounds, excluding PAHs with concentrations below 0.5 mg/kg. One PCB compound, Aroclor - 1254, and one pesticide, 4,4 -DDT, were also detected at concentrations of 0.19 mg/kg and 0.12 mg/kg, respectively.

No background surface soil sampling was conducted as part of the Phase II Soil Investigation.

Subsurface Soil Investigation

No off-site or background subsurface soil sampling was conducted. Results of subsurface soil sampling were compared to results of background surface soil sampling performed during the Phase I, Soil Investigation.

2. Air Dispersion Modeling Investigation

The purpose of the Air Dispersion Modeling Investigation was to predict the migration of contaminants and human exposure through air emissions from the South Tacoma Field site. Windblown dust emissions of arsenic, beryllium, cadmium, chromium, copper, manganese, mercury, and total probable carcinogenic PAHs were estimated for receptors located both within the site and off the site. Predicted airborne concentration of contaminants were below EPA's screening levels for industrial and residential exposure scenarios at off-site receptors.

3. Blackberry Investigation

As part of the Blackberry Investigation, six blackberry samples were gathered from three off-site locations within one mile of the South Tacoma Field site. Natural background samples were collected to determine concentrations of inorganics consistently detected in blackberries in the environment. Area background samples were collected to evaluate concentrations of inorganics detected in blackberries potentially impacted by human activities, such as industrial emissions.

Natural background samples were collected from one sampling location, the Flett Creek drainage area located about one-quarter mile south of South 74th Street. Area background samples were collected from two locations situated in industrial areas with similar conditions as the site. One sampling location, 58th Street and South Adams, is considered upwind of the site, and the other sampling location, South Tacoma Way and Warner Street, is considered downwind.

Analytical results revealed that blackberry samples from off-site locations have low concentrations of inorganics. Results also indicated that inorganics were detected more frequently in background samples then on-site samples, and background concentrations were similar to those detected on-site. Concentrations of inorganic detected in natural background samples were similar to concentrations found in area background samples. In addition, area background samples collected upwind of the site contained more detectable inorganics then area background samples collected downwind.

Contaminants detected in off-site blackberry samples are below comparison values and are not considered as contaminants of concern. Comparison values are based on the assumption that the blackberry consumption rate is similar to the average homegrown raw strawberry consumption rate of 12.3 grams of strawberries per day. Note, this rate is derived from a 3-day consumption rate, and may not be representative of the annual consumption rate (30).

4. Soil-gas Investigation

The Soil-gas Investigation was confined to the Pioneer Builders Supply property; no off-site soil-gas sampling was performed.

5. Groundwater Investigation

To characterize off-site water quality, the Groundwater Investigation included monitoring of upgradient and background groundwater wells. Five upgradient and five background wells are screened in the Upper Layer A aquifer within the vicinity of the site. Groundwater samples were collected during the second quarter, July and August 1991, and fourth quarter, January and February 1992.

Elevated concentrations of inorganic chemicals were detected in background and upgradient wells. Aluminum, chromium, cobalt, cooper, iron, lead, sodium, and vanadium detected in background wells at concentrations exceeding the range of inorganic concentrations naturally occurring in groundwater. Some of the highest inorganic concentrations were detected in samples collected from the upgradient well, CBS-10A, located adjacent to the southeast corner of the site (Appendix - A, Figure 3). Low concentrations of volatile and semi-volatile compounds were detected in samples collected from upgradient wells, TL-12A, TL-13, TL-23A, and CBS-10A, and background wells TL-16A and WCC-2. No pesticides and PCBs were detected in off-site groundwater. Refer to Appendix - B, Table 7 for contaminants of concern associated with off-site groundwater.

6. Surface Water and Sediment Investigation

Surface Water

The primary source of on-site surface water originates from two upgradient drainage sub-basins northwest of the site. To characterize surface water flowing onto the site, runon surface water samples were collected from two locations: the storm drain outlet south of the city of Tacoma pump station and the manhole for South 38th Street storm drain. During the 1-year monitoring period, 11 monthly surface water samples as well as 11 storm-event samples were collected from the two runon sampling locations. Runon samples were analyzed for inorganic chemicals, boron, PAHs, and fecal bacteria.

Concentrations of metals and PAHs detected in runon surface water samples were generally equal or higher than concentrations detected in on-site surface water. In Appendix - B, Table 5, contaminants of concern detected in runon surface water samples are listed.

In addition, 10 surface water samples were collected from 5 background locations within the South Tacoma Channel. The quality of background surface water appears to be impacted by contamination of urban surface water runoff. Elevated inorganic chemicals were detected consistently in background surface water samples. Background surface water also had concentrations of volatile and semi-volatile compounds, including PAHs.

Sediments

The investigation does not include off-site or background sediment sampling.

C. Quality Assurance and Quality Control

In preparing the Public Health Assessment, information provided in the reference documents was used with the assumption that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, field and laboratory procedures, data reporting. The validity of the analysis and conclusions drawn in this Public Health Assessment is determined by the completeness and reliability of the referenced information.

D. Physical and Other Hazards

No physical or other hazards were found at the South Tacoma Field Superfund site that would pose a public health threat.

PATHWAYS ANALYSES

To determine whether people are exposed to contaminants of concern associated with the South Tacoma Field site, environmental and human components of the exposure pathways are evaluated. Pathway analysis consists of five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of exposure, and an exposed population.

Exposure pathways are categorized as completed or potential. Completed exposure pathways have all five elements and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or is likely to occur in the future. Potential exposure pathways have at least one of the five elements missing, but it could exist. Potential exposure pathways indicate that exposure to a contaminant of concern could have occurred in the past, could currently be occurring, or may occur in the future. An exposure pathway can be eliminated from consideration if at least one of the five elements is missing and will never be present. The following section discusses the relevant pathways with the completed and potential exposure pathway elements profiled in Appendix - B, Table 8.

A. Completed Exposure Pathways

Three completed exposure pathways, surface soils, sediments, and surface water exist for individuals who used the South Tacoma Field site for recreational activities.

Surface Soils Pathway

Past, present, and future completed exposure pathways exist for individuals who come in contact with surface soils during recreational activities at the sampling units: BNR Dismantling Yard, BNR Railyard, Airport, and Swamp/Lakebed. Recreational activities by workers and nearby residents, such as picnicking, walking, biking, and picking blackberries have been observed at the site. The public tends to use the site as a recreational park, despite EPA efforts in restricting site access.

Surface soils are contaminated primarily with inorganics, PAHs, and PCBs in several of the site's sampling units. However, a principal factor affecting the transport of these contaminants at the point of exposure is groundcover, such as vegetation or pavement. The majority of the site is well-vegetated with the exception of a dirt road and bike trails. The dirt road is an extension of Madison Street that runs along the west boundary of the Amsted and TIP sampling units, and north through the Swamp/Lakebed and Airport sampling units. A groundcover of perennial grasses, blackberry thickets, and scattered shrubs occupies the north end of the site, while the non-wetlands of the south end are covered with perennial grasses. Along the banks of the surface water channel grasses and blackberries grow. In addition, the surface water channel supports a 12-acre riparian woodland composed of alder and cottonwood with an understory of various shrubs. Pavement covers the TIP and southern portions of the BNR Railyard units. To the north, the Tacoma City Light unit is also mostly pavement. Though, groundcover may influence the extent of exposure, recreational use of the sampling units: BNR Dismantling Yard, BNR Railyard, Airport, and Swamp/Lakebed could result in people being exposed to contaminants in surface soils.

Recreationalists/trespassers can be exposed to contaminants in surface soils through incidental ingestion of soil, inhalation of soil dust, and dermal contact with soil. Both adults and older children have been observed trespassing onto the site for recreational activities. These recreationalists/trespassers are believed to be nearby residents, as well as workers from on-site businesses. The maximum duration recreationalists/trespassers are likely to be exposed to surface soils is 30 years, 6 years as a child and 24 years as an adult. This exposure duration is the residential standard value recommended by EPA for the national upper-bound time at one residence. National upper-bound time at one residence is actually the 90th percentile of the longest time a person would live at one residence. Based on best professional judgement, the frequency at which recreationalists/trespassers access the site is estimated to be 2 days per week for 52 weeks per year for children and 1 day per week for 52 weeks per year for adults.

Surface Water and Sediments Pathways

Surface water and sediments represent past, present, and future completed exposure pathways for recreationalists/trespassers at the following sampling units: BNR Dismantling Yard, Airport, and Swamp/Lakebed. Though the extent of recreational activities in the surface water channel and wetlands of these units is not known, contaminated surface water and sediments are accessible. Recreationalists/trespassers can be exposed to elevated levels of inorganics, PAHs, and PCBs through ingestion of and dermal contact with surface water and sediments.

The exposure assumptions for duration and frequency to surface soils also apply to the exposure of recreationalists/trespassers to sediments. Exposure to surface water through activities, such as swimming, is assumed to occur 1 hour per visit during the 3 months of summer, June through August. The frequency at which recreationalists/trespassers are anticipated to engage in water activities at the site is estimated to be 2 days per week for 12 weeks per year for children and 1 day per week for 12 weeks per year for adults.

B. Potential Exposure Pathways

At the South Tacoma Field site, three potential pathways of exposure exist groundwater, surface soils, and subsurface soils.

Groundwater Pathway

On-site contamination of groundwater involves inorganics, as well as volatile and semivolatile organic compounds in the shallow aquifer beneath the site. The results of the groundwater investigation did not indicate a site-wide contamination plume, but rather an impact to groundwater in four localized areas. The four areas include the Pioneer Builders Supply property, the adjoining portions of the Airport and Swamp/Lakebed sampling units, the former rail car cleanout area in the south end of the BNR Railyard sampling unit, and the Amsted property. Currently, there are no private supply wells within these areas of groundwater contamination.

Located in a heavy industrial district, future development of the site is likely to involve the construction of new industrial facilities. Facility owners may install private supply wells to provide water for their industrial operations. Should supply wells access contaminated groundwater, workers may be exposed to contaminants through incidental ingestion of water, inhalation of water vapors, and dermal contact with water.

Another future exposure pathway associated with groundwater is the migration of contaminants to nearby public supply wells or private supply wells used for industrial and domestic purposes.

Tacoma Public Utilities has 5 heat pump wells located on the northwest portion of the site, and a municipal well field consisting of 13 production wells north-northeast of the site. Forty-one residential wells are within a 1-mile radius of the site. Groundwater contamination is currently believed to be localized and migration of groundwater unlikely. However, infiltration of soil contaminants to groundwater can potentially occur resulting in a more extensive contamination plume. Should migration of the plume impact groundwater at nearby supply wells or at wells installed in the future, workers and residents could be exposed to contaminants through ingestion of water, inhalation of water vapors, and dermal contact with water.

Monitoring of upgradient and background wells revealed contamination of off-site groundwater. In general, contamination consists of elevated concentrations of inorganics and volatile and semi-volatile compounds detected in groundwater from wells considered upgradient of the site. Contamination from sources upgradient could potentially migrate and impact water quality at the site. Should future industrial wells be installed on the site, workers could be exposed to contaminants through ingestion of water, dermal contact with water, and inhalation of water vapors.

Additionally, the extent of off-site groundwater contamination is not known. Should existing public and private supply wells or wells installed in the future access contaminated groundwater, workers and residents could potentially be exposed to contaminants. Exposure could occur through ingestion of water, inhalation of water vapors, and dermal contact with water. Currently, municipal water supply is routinely monitored to ensure groundwater quality meets Federal and State Drinking Water Standards. There is no indication that the nearby municipal well field north-northwest of the site is being impacted by off-site groundwater contamination. However, it is uncertain whether this municipal water supply could be effected in the future and whether private supply wells are or could be impacted by off-site groundwater contamination.

Surface Soils Pathway

Past and future potential exposure pathways may exist for surface soils at the Amsted and TIP unit. Surface soils were contaminated with inorganics and PAHs as a result of operations performed at the Griffin Wheel Brass Foundry from 1890 through 1980. In 1989, the former brass foundry was demolished and access to the Amsted property restricted by the installation of 6-foot chain-linked fence. The TIP unit is also restricted by a chain-linked fenced with a gate at the South Proctor Street entrance. The gate is locked after normal business hours. During the operation of the brass foundry, people who worked on the property could have been exposed to contaminants in surface soil. In addition, people who trespassed on the property before access was restricted could have been exposed to surface soil contamination.

Exposure to surface soils may occur in the future should security be compromised and people trespass onto the Amsted or TIP units. Trespassers may be exposed to inorganics and PAHs through incidental ingestion of soil, inhalation of soil dust, and dermal contact with soil.

Subsurface Soils Pathway

Future exposure to contaminated subsurface soils by workers and recreationalists/trespassers may occur during construction activities. Zoned for heavy industry, future development of the South Tacoma Field site will include the construction of industrial facilities. Typical construction activities, such as laying a building foundation are likely to disturb subsurface soils down to depths of 15 feet. Site excavation can disturb subsurface soils exposing contaminants such as inorganics, PCBs, and PAHs. Should contaminated subsurface soils be uncovered, workers and recreationalists/trespassers may be exposed to contaminants through ingestion of and dermal contact with soil, and inhalation of soil dust.

PUBLIC HEALTH IMPLICATIONS

A. Toxicologic Evaluation

The Toxicologic Evaluation subsection examines the potential for health implications resulting from exposure to contaminants of concern associated with completed exposure pathways. The completed exposure pathways identified are past, present and future exposure to recreationalists/trespassers to contaminants of concern in surface soils, surface water, and sediments. Through this toxicological evaluation process, the contaminants of concern arsenic, copper, lead, manganese, PAHs, and PCBs were determined to be at sufficient concentrations that could potentially cause adverse health effects in recreationalists/trespassers.

In assessing health effects that could result from exposure to site contaminants, daily exposure doses which an individual may receive are calculated. The estimated daily exposure dose is compared to a health-based guideline which defines a level of exposure at which adverse health effects are unlikely to occur. ATSDR developed MRLs to be used as a health-based guideline in evaluating noncarcinogenic adverse health effects for routes of exposure such as ingestion and inhalation, and for exposure durations including acute (less than 14 days), intermediate (15 days to 364 days), and chronic (greater than 365 days). When MRLs are not available, EPA health-based guidelines are used. EPA has developed RfDs and reference concentrations (RfCs) for ingestion and inhalation exposure, respectively.

EPA has reviewed available data from human and animal studies to determine the carcinogenic potential of specific chemicals, and for many chemicals, EPA has derived cancer slope factors for oral and inhalation exposure routes. In evaluating carcinogenic health effects, a cancer slope factor is used with the estimated daily exposure dose to predict the increased risk of an individual in developing cancer over a lifetime of 70 years. In a normal population, the expected rate is about 250,000 individuals developing cancer per 1,000,000 people; in the Toxicologic Evaluation subsection, cancer risk is related as anticipated increase above the expected cancer rate. Cancer risk is qualitatively expressed as "no increased risk" which corresponds to 1 to 9 excess cancers in 70 years per 1,000,000 persons exposed; "no apparent increased risk," 1 to 9 excess cancers per 100,000 persons exposed; "low increased risk," 1 to 9 excess cancers per 10,000 persons exposed; "moderate increased risk," 1 to 9 excess cancers per 1,000 persons exposed; "high increased risk," 1 to 9 excess cancers per 100 persons exposed; and "very high increased risk," 1 to 9 excess cancers per 10 persons exposed.

The estimation of the daily exposure dose involves determining contaminant concentrations at points of potential human exposure and developing assumptions regarding the extent of human exposure in the completed exposure pathways. For this evaluation, maximum concentrations detected for contaminants of concern in surface soils, surface water, and sediments are considered as concentrations at points of potential exposure. Assumptions of recreational exposure to contaminants are described below, and are also presented in Appendix - C. Individuals are assumed to access the site for recreational activities a maximum of 2 days per week for 52 weeks per year for children and 1 day per week for 52 weeks per year for adults. This exposure frequency is based on best professional judgement considering conversations with EPA site manager. Children are assumed to have a body weight of 16 kg, and to ingest 200 mg of soil per day, and adults are assumed to have a body weight of 70 kg, and to ingest 100 mg of soil per day. The assumptions for soil ingestion is presumed to be the same for sediment ingestion.

For surface water, incidental ingestion is assumed to be 50 milliters (ml) per hour for both children and adults. Recreational water activities are assumed to occur one hour per visit. This intake rate is based on EPA recommended intake value for intensive water activities, (e.g., swimming). Water activities are most likely to occur during the summer months at the site. Therefore, recreationalists/trespassers are believed to access surface water at a maximum of 2 days per week for 12 weeks per year for children and 1 day per week for 12 weeks per year for adults. Exposure duration of recreationalists/trespassers to surface soils, surface water, and sediments is assumed to be 6 years for children and 30 years for adults. In predicting the lifetime excess cancer risk, the duration of exposure is presumed to be 30 years over a lifetime of 70 years.

Following is a toxicological evaluation of the contaminants of concern associated with the completed exposure pathways surface soils, surface water, and sediments.

Inorganic Compounds

Aluminum

Exposure to aluminum may have occurred in the past, may presently be occurring, and could occur in the future should individuals engage in recreational activities on the site. Recreationalists/trespassers can be exposed to aluminum primarily through incidental ingestion of contaminated surface soils, surface water, and sediments. Dermal contact is not considered to be a significant route of exposure for aluminum, as for most inorganics. Inhalation of aluminum in soil dust is also likely to be minimal. Due to present conditions at the site, air dispersion modeling concluded that airborne concentrations of surface soil contaminants are relatively low and in general, below industrial and residential screening levels. For this reason, inhalation as a route of exposure for surface soil contaminants is likely to be insignificant, therefore not evaluated in this toxicological evaluation.

Analytical results of surface soils revealed aluminum at maximum concentrations of 24,000 mg/kg at the Swamp/Lakebed, 26,600 mg/kg at the Airport, 104,000 mg/kg at the BNR Dismantling Yard, 28,000 mg/kg at the BNR Railyard, 15,400 mg/kg at the TIP, and 27,500 mg/kg at the Amsted sampling units. Though the Amsted unit is presently secured and unaccessible by recreationalists/trespassers, past exposure to aluminum may have occurred or may occur in the future depending on site security available at the time. Therefore, contaminants of concern detected at the Amsted unit will also be evaluated. Aluminum was detected in surface water at maximum concentrations of 38,500 µg/L in runon samples, 80,900 µg/L in on-site samples, and 4,040 µg/L in runoff samples. In sediment samples, the maximum concentration of aluminum was detected at 38,700 mg/kg.

Because of the lack of toxicity data, a chronic oral ATSDR MRL or EPA RfD has not been developed to evaluate the potential for noncarcinogenic health effects following aluminum exposure. Exposure to aluminum may be harmful to certain individuals, such as people with kidney disease and possibly Alzheimer's patients. Noncarcinogenic health effects associated with aluminum exposure include respiratory problems from breathing aluminum dust, and possibly neurological, teratogenic, and skeletal problems from drinking water containing high levels of aluminum.

EPA has not yet evaluated aluminum for evidence of human carcinogenicity. However, based on available data at this time, aluminum exposure is not known to cause cancer in humans (2, 28).

The estimated daily exposure dose for recreationalists/trespassers exposed to aluminum in surface soils, surface water, and sediments is considered low and likely to be conservative. In calculating the estimated daily exposure dose, absorption of aluminum following ingestion was assumed to be 100 percent. However, evidence from human and animal studies suggest that the absorption of aluminum is lower than 100 percent, yet the actual rate and extent of absorption have not been established. Many plants and processed foods contain low levels of aluminum. Daily exposure to aluminum in common beverages and food products, such as soft drinks, peanut butter, milk, cheese, eggs, and lettuce is higher than the estimated daily exposure dose (2). Though health effects cannot be accurately predicted without additional toxicity data, it is unlikely that recreationalists/trespassers would experience adverse health effects from exposure to concentrations of aluminum found at the site.

Antimony

Past, present, and future exposure to antimony may have occurred, may be occurring, and could occur should recreationalists/trespassers come in contact with contaminated surface soils, surface water, and sediments on the site. Exposure to antimony can result through incidental ingestion of surface soils, surface water, and sediments. Dermal contact is not considered an important route of exposure for antimony.

At four of the six sampling units, elevated concentrations of antimony were detected in surface soil samples. A maximum concentration of antimony was detected at 24.4 mg/kg at the Airport, 46.6 mg/kg at BNR Dismantling Yard, 491 mg/kg at the BNR Railyard, and 43.7 mg/kg at Amsted sampling units. In surface water, antimony was found at a maximum concentration of 15.9 µg/L in runon samples; antimony was not detected in on-site or runoff surface water samples. Antimony was detected in sediment samples at a maximum concentration of 33.9 mg/kg.

EPA derived an oral RfD for antimony of 0.0004 mg/kg/day for chronic exposure. Antimony exposure at the maximum concentration detected in surface soils at the BNR Railyard unit can result in estimated daily exposure doses for adults and children that exceed the chronic oral RfD. Estimated daily exposure doses based on maximum antimony concentrations in surface soils at the Airport, BNR Dismantling Yard, and Amsted sampling units do not exceed the RfD. Estimated daily exposure doses determined for maximum concentrations of antimony in surface water and sediments also do not exceed the RfD.

Animal studies indicated long-term exposure to antimony can cause irritation to eyes, skin, and lungs, as well as heart problems, vomiting, and diarrhea. The RfD was derived from the chronic Lowest Observed Adverse Effect Level (LOAEL) of 0.35 mg/kg/day for less serious effects in animals (3, 28). In comparison, the estimated daily exposure dose for children exposed to antimony in surface soils at the BNR Railyard unit is about 200 times below the LOAEL, and the estimated daily exposure dose for adults is about 800 times below the LOAEL. Because estimated daily exposure doses are well below the LOAEL, it is unlikely that recreationalist/trespasser would experience adverse noncarcinogenic health effects from long-term exposure to antimony in surface soils at this unit.

Antimony has not been evaluated by EPA for evidence of human carcinogenicity. Because of insufficient data, the lifetime cancer risk of recreationalists/trespassers exposed to antimony cannot be predicted.

Arsenic

Arsenic was found in surface soil samples at maximum concentrations of 54.4 mg/kg at the Swamp/Lakebed, 50.1 mg/kg at the Airport, 696 mg/kg at the BNR Dismantling Yard, 395 mg/kg at the BNR Railyard, 26.2 mg/kg at the TIP, and 389 mg/kg at the Amsted sampling units. In addition, arsenic was detected in surface water at maximum concentrations of 25.5 µg/L in runon samples, 24.8 µg/L in on-site samples, and 4.0 µg/L in runoff samples. The maximum concentration of arsenic detected in sediment samples was 93.8 mg/kg.

Exposure to arsenic may have occurred in the past, may presently be occurring, and could occur in the future to individuals who trespass on the site for recreational purposes. Exposure can result through incidental ingestion of arsenic-contaminated surface soils, surface water, and sediments. Dermal contact is not considered a significant route of exposure for arsenic.

ATSDR has developed an oral MRL for inorganic arsenic of 0.0003 mg/kg/day for chronic exposure (4). Estimated daily exposure doses for children and adults exposed to arsenic at maximum concentrations detected in surface soils at the BNR Dismantling Yard, BNR Railyard, and Amsted sampling units exceed the chronic oral MRL. The estimated daily exposure dose for children predicted for the maximum concentration of arsenic detected in sediments also exceeds the MRL. Estimated daily exposure doses for children and adults exposed to maximum concentrations of arsenic in surface water does not exceed the MRL.

To further evaluate possible health effects, estimated daily exposure doses were compared to the No Observed Adverse Effect Level (NOAEL) of 0.0008 mg/kg/day and LOAEL of 0.014 mg/kg/day in humans from which the MRL was derived (4). Adult estimated daily exposure doses calculated for arsenic-contaminated surface soils at the BNR Dismantling Yard, BNR Railyard, and Amsted sampling units are below the NOAEL. However, the child estimated daily exposure dose determined for arsenic-contaminated surface soils at the BNR Dismantling Yard unit is about three times greater than the NOAEL and about six times below the LOAEL. For the BNR Railyard and Amsted sampling units, the child estimated daily exposure doses are about 2 times greater than the NOAEL and about 10 times below the LOAEL. The estimated daily exposure doses for adults and children exposed to a maximum concentration of arsenic detected in sediments are below the NOAEL.

Frequent exposure by children to arsenic in surface soils at the BNR Dismantling Yard, BNR Railyard, and Amsted sampling units may result in noncarcinogenic health effects particularly in sensitive individuals. Adverse effects observed at the chronic LOAEL of 0.014 mg/kg/day are hyperpigmentation, keratosis, and vascular complications. Gastrointestinal irritation such as nausea, vomiting, and diarrhea were also observed at chronic LOAELs for less serious effects in humans with values near the LOAEL of 0.014 mg/kg/day.

Inorganic arsenic is classified by EPA as a known human carcinogen. Epidemiological studies and case reports conclude that chronic arsenic ingestion is associated with skin cancer. An oral cancer slope factor of 1.75 (mg/kg/day)-1 for inorganic arsenic has been developed. This cancer slope factor is used with the estimated daily exposure dose for recreationalists/trespassers to predict the increased risk of developing skin cancer. In addition to skin cancer, there are studies suggesting arsenic ingestion increases the risk of liver, bladder, kidney, and lung cancer. EPA has not yet developed an oral cancer slope factor to estimate risk of internal cancers resulting from arsenic exposure (4, 28).

In conclusion, long-term exposure by recreationalists/trespassers to surface soils at the Swamp/Lakebed, Airport, and TIP sampling units is anticipated to result in no increased risk of developing skin cancer over a lifetime. Long-term exposure in surface soils at the BNR Railyard and Amsted sampling units may result in no apparent increased risk of developing skin cancer over a lifetime. However, should long-term exposure to arsenic-contaminated surface soils occur at the Dismantling Yard unit, recreationalists/trespassers may experience a low increased risk of developing skin cancer over a lifetime. Recreationalists/trespassers who are exposed to arsenic in surface water should have no increased risk of developing skin cancer, and long-term exposure to arsenic in sediments should result in no apparent increased risk of developing skin cancer over a lifetime.

Barium

Recreationalists/trespassers may have been exposed in the past, may presently be exposed, and could be exposed in the future to elevated concentrations of barium in on-site surface water. The maximum concentration of barium detected in on-site surface water samples was 773 µg/L. Exposure can occur through incidental ingestion of surface water during recreational activities, such as swimming.

ATSDR has not developed a chronic oral MRL for barium; however an EPA oral RfD of 0.07 mg/kg/day does exist for chronic exposure (5, 28). Estimated daily exposure doses for adults and children based on the maximum barium concentration detected in surface water do not exceed the chronic RfD. Human and animals studies revealed that increased blood pressure is associated with chronic exposure to barium. Recreationalists/trespassers are unlikely to experience adverse effects, such as increased blood pressure from exposure to barium in surface water.

Barium has not been evaluated by EPA for evidence of human carcinogenicity. Currently, no human studies exist and available animal studies are inadequate to evaluate the carcinogenic potential of barium.

Beryllium

Exposure to beryllium may have occurred in the past, may presently be occurring, and could occur in the future should individuals who engage in recreational activities at the site. Recreationalists/trespassers can be exposed primarily through incidental ingestion of surface soils, surface water, and sediments. Dermal contact is not an important route of exposure for beryllium.  

Maximum concentrations of beryllium in surface soils samples were detected at 1 mg/kg at the Swamp/Lakebed, 0.98 mg/kg at the Airport, 14.4 mg/kg at the BNR Dismantling Yard, 2.7 mg/kg at the BNR Railyard, 0.57 mg/kg at the TIP, and 4.4 mg/kg at the Amsted sampling units. In surface water, a maximum concentration of 1.9 µg/L was detected in on-site samples. Beryllium was not detected in runon and runoff surface water samples. A maximum concentration of beryllium found in sediment samples was at 1.1 mg/kg.

Based on animal studies, EPA has developed a chronic oral RfD of 0.005 mg/kg/day for beryllium. In comparison, estimated daily exposure doses for adults and children exposed to maximum beryllium concentrations detected in surface soils, surface water, and sediment are well below the RfD. Therefore, long-term exposure by recreationalist/trespasser to beryllium is unlikely to result in noncarcinogenic health effects.

EPA classifies beryllium as a probable human carcinogen and has derived a cancer slope factor of 4.3 (mg/kg/day)-1. The lifetime cancer risk for recreationalists/trespassers exposed for 30 years to beryllium through ingestion of contaminated surface soils, surface water, and sediments is predicted to be no increased risk of developing cancer over a lifetime (6, 28).

Boron

Elevated boron concentrations were detected in surface soils at the BNR Dismantling Yard unit, as well as in surface water. A maximum concentration of 1,300 mg/kg was detected in surface soil samples from the BNR Dismantling Yard unit and a maximum concentration of 174.4 µg/L in surface water runon samples. Recreationalists/trespassers may have been exposed in the past, may presently be exposed, and could be exposed in the future to boron-contaminated media.

A chronic oral RfD for boron of 0.09 mg/kg/day was developed. Estimated daily exposure doses for children and adults exposed to maximum concentrations of boron in surface soils and surface water do not exceed the chronic RfD. Therefore, recreationalists/trespassers exposed for long periods of time to boron are unlikely to experience noncarcinogenic health effects.

EPA's evaluation for evidence of human carcinogenicity for boron is currently under review. Until additional carcinogenicity data becomes available, the lifetime cancer risk cannot be predicted for recreationalists/trespassers exposed to boron-contaminated surface soils and surface water (7, 28).

Cadmium

Recreationalists/trespassers may have been exposed, might presently be exposed, or could be exposed in the future to cadmium through incidental ingestion of surface water. A maximum concentration of 18.3 µg/L was detected in one on-site surface water sample during the dry season. Concentrations of cadmium in surface soils and sediments were below ATSDR comparison values and not considered a health concern.

Based on a human study, ATSDR derived an oral MRL for cadmium of 0.0007 mg/kg/day for chronic exposure (8). Estimated daily exposure doses for adults and children exposed to the maximum cadmium concentration detected in surface water are below the MRL. Therefore, long-term exposure of recreationalists/trespassers to cadmium is not anticipated to result in noncarcinogenic health effects.

Currently there is insufficient data to assess the human carcinogenicity of cadmium by the oral route of exposure. Until additional data becomes available, the lifetime cancer risk cannot be predicted for recreationalists/trespassers exposed to cadmium-contaminated surface water.

Chromium (Total)

Exposure to chromium by individuals who trespass on the site may have occurred in the past, may presently be occurring, or could occur in the future. Recreationalists/trespassers can be exposed primarily through incidental ingestion of soils, surface water, and sediments. Dermal contact is not considered a significant route of exposure for chromium.

Chromium was detected in surface soil samples from the Swamp/Lakebed and BNR Dismantling Yard units at maximum concentrations of 501 mg/kg and 707 mg/kg, respectively. In surface water, a maximum concentration of 50.4 µg/L was observed in runon samples and 193 µg/L in on-site samples. A maximum concentration of chromium detected in sediment samples was at 614 mg/kg.

The most common forms of chromium produced by industry are chromium (III) and chromium (VI). Chromium (VI) is more readily absorbed into the gastrointestinal tract than chromium (III). Analytical results reported chromium as total, and did not specify the valence states, chromium (III) or (VI). Therefore for this toxicological evaluation, chromium (total) is assumed to be in the most bioavailable form, chromium (VI).

No MRL has been derived for oral exposure to chromium (VI); however an oral RfD of 0.005 mg/kg/day has been developed by EPA for chronic exposure. The estimated daily exposure doses determined for adults and children exposed to maximum chromium concentrations in surface soils, surface water, and sediments do not exceed the chronic RfD. Recreationalists/trespassers who come in contact with chromium-contaminated media are unlikely to experience noncarcinogenic health effects.

In evaluating carcinogenic effects, EPA classifies chromium (VI) as a known human carcinogen by the inhalation route of exposure. Epidemiological studies indicate a correlation between inhalation exposure to chromium (VI) and lung cancer. Ingested chromium (VI) has not be classified with respect to human carcinogenicity. The risk of cancer cannot be predicted for recreationalists/trespassers exposed to chromium through ingestion of contaminated media (8, 27).

Cobalt

Recreationalists/trespassers may have been exposed in the past, may currently be exposed, and could be exposed in the future to cobalt-contaminated surface soils, surface water, and sediments. Maximum concentrations of cobalt observed in surface soils were at 21.1 mg/kg at the Swamp/Lakebed, 17.7 mg/kg at the Airport, 135 mg/kg at the BNR Dismantling Yard, 37.4 mg/kg at the BNR Railyard, 18.2 mg/kg at the TIP, and 20.7 mg/kg at the Amsted sampling units. Cobalt was detected in surface water at maximum concentrations of 997 µg/L in the runon samples and 24.1 µg/L in on-site sample. A maximum concentration of cobalt in sediment samples was at 20 mg/kg.

No studies are available for to derive a chronic oral MRL or RfD for cobalt. EPA has yet to evaluate evidence of human carcinogenicity for cobalt (10, 28). Without further chronic exposure studies, the noncarcinogenic and carcinogenic potential of cobalt cannot be determined. Health implications of long-term exposure to cobalt in surface soils, surface water, and sediments cannot be evaluated until additional toxicological data becomes available.

Copper

Elevated concentrations of copper were found in surface soils, surface water, and sediments at the site. Maximum concentrations of copper detected in surface soil samples were at 287 mg/kg at the Swamp/Lakebed, 418 mg/kg at the Airport, 11,000 mg/kg at the BNR Dismantling Yard, 13,000 mg/kg at the BNR Railyard, 160 mg/kg at the TIP, and 163,000 mg/kg at the Amsted sampling units. Copper was detected at maximum concentrations of 52.2 µg/L in surface water in runon samples, 2,980 µg/L in on-site samples, and 9.2 µg/L in runoff samples. A maximum concentration observed in sediment samples was 979 mg/kg. Exposure to copper may have occurred in past, may presently be occurring, and could occur in the future by recreationalists/trespassers through inadvertent ingestion of surface soils, surface water, and sediments.

Because of inadequate toxicity data for copper, a chronic oral MRL or RfD has not been developed. However, an acute and chronic LOAEL exists for less serious effects in humans of 0.07 mg/kg/day and 0.056 mg/kg/day, respectively. There are numerous reports of acute gastrointestinal effects including vomiting, diarrhea, nausea, abdominal pain, and a metallic taste in the mouth after ingestion of large amounts of copper. The acute LOAEL is derived from an one time exposure to copper in drinking water resulting in gastrointestinal effects. The chronic LOAEL is based on a reported case of a family exposed to copper in drinking water for approximately a year and a half (11). The health effects experienced by the family also include nausea, vomiting, and abdominal pain.

Estimated daily exposure doses for adults and children exposed to the maximum concentration of copper observed in surface soils at the Amsted unit exceed the acute and chronic LOAELs. Currently, the Amsted unit is secure and access by recreationalists/trespassers unlikely. However, prior to securing the unit, recreationalists/trespassers could have explored the unit exposing themselves to contaminated surface soils. Future exposure by recreationalist/trespasser could also occur should the unit's security be compromised. Short- and long-term exposure by recreationalists/trespassers to copper-contaminated surface soils at the Amsted unit may result in gastrointestinal effects.

Because of the lack of human data and inadequate animal data, EPA has not classified copper as to chemical's potential for human carcinogenicity. Current data has not shown an elevated incidence of cancer in either humans or animals following inhalation, ingestion, and dermal contact exposure to copper. Until additional carcinogenic data becomes available, the lifetime cancer risk cannot be estimated for recreationalists/trespassers exposed to copper-contaminated surface soils at the Amsted unit.

Lead

Recreationalists/trespassers may have been exposed in the past, may currently be exposed, and may be exposed in the future to lead through incidental ingestion of contaminated surface soils, surface water, and sediments. Absorption through dermal contact is not considered a significant route of exposure for lead.

Maximum concentrations of lead observed in surface soils samples were at 1,510 mg/kg at the Swamp/Lakebed, 1,160 mg/kg at the Airport, 24,000 mg/kg at the BNR Dismantling Yard, 27,100 mg/kg at the BNR Railyard, 285 mg/kg at the TIP, and 118,000 mg/kg at the Amsted sampling units. Lead was detected in surface water at a maximum concentration of 124 µg/L in runon samples, 219 µg/L in on-site samples, and 9.5 µg/L in the runoff samples. In sediments, the maximum lead concentration was at 2,505 mg/kg.

No noncarcinogenic health guidelines, such as a MRL or RfD have been derived for inorganic lead because of the difficultly in identifying a clear threshold for lead below which there are no risks of adverse health effects (14, 28). The majority of human data regarding lead exposure are expressed in terms of blood lead levels, microgram per deciliter of blood (µg/dL), rather than daily exposure doses expressed as mg/kg/day. Increases in blood lead levels can represent a health concern; however the extent of concern depends on the pre-existing blood lead level of the exposed individual.

Unborn babies, infants, and young children are more susceptible than adults to increased lead absorption, as well as to toxic effects of lead. Children exposed to lead can accumulate concentrations in their bodies. Therefore, even exposure to low concentrations of lead over an extended period of time can result in a significant long-term accumulation in a child, increasing that child's risk of adverse health effects. Long-term exposure to low lead concentrations can cause irreversible learning difficulties, mental retardation, and delayed neurological and physical development in children. Low birth weights, premature birth, and factors that may influence early neurological development have been associated with infants having maternal or umbilical cord blood lead levels above 12 to 14 µg/dL and possibly as low as 7 µg/dL. In infants, deficits in mental indices have been observed at maternal blood lead levels as low as 6 to 7 µg/dL.

Deficits in IQ and other measures of cognitive function, such as attention span, have been associated with blood lead levels of 15 µg/dL and possibly lower in socially disadvantaged children. Slowed peripheral nerve conduction has been observed in children with blood lead levels of 20 to 30 µg/dL. Early childhood growth reductions have been associated with blood lead levels from 5 to 35 µg/dL in one study and with blood lead levels greater than 40 µg/dL in another study.

In adults, increases in blood pressure have been observed at blood lead levels as low as 7 µg/dL. In addition, lead exposure affects the peripheral nervous system and can cause impairment of hearing, vision, and muscle coordination. Blood, kidney, heart, immune, and reproductive systems can also be adversely effected by lead toxicity.

Without knowing pre-existing and actual blood lead levels of individual recreationalists/trespassers, it is difficult to determine whether blood lead is elevated from exposure at the site, and whether blood lead is at significant levels to result in noncarcinogenic effects. However, it is likely that frequent exposure to highly contaminated media over a long period of time will pose a health threat to recreationalists/trespassers, particularly those with blood lead levels already elevated from exposure to other lead sources.

Lead is classified as a probable human carcinogen by EPA based on sufficient animal carcinogenicity data. Because of uncertainties in the animal data, an oral cancer slope factor or oral unit risk for lead has not been developed (28). Although the cancer risk from lead cannot be quantified, frequent exposure of recreationalists/trespassers may potentially result in an increased risk of developing cancer over a lifetime.

Manganese

Recreationalists/trespassers may be exposed to manganese in surface soils at maximum concentrations of 6,090 mg/kg at the Swamp/Lakebed, 763 mg/kg at the Airport, 5,850 mg/kg at the BNR Dismantling Yard, 2,270 mg/kg at the BNR Railyard, 27,000 mg/kg at the TIP and 21,800 mg/kg at the Amsted sampling units. Exposure to manganese may occur at maximum concentrations in surface water of 659 mg/kg in runon samples, 865 µg/L in on-site samples, and 52.6 µg/L in runoff samples, as well as exposure at a maximum concentration in sediments of 814 mg/kg.

A chronic oral MRL has not been developed by ATSDR for manganese; however an EPA oral RfD of 0.005 mg/kg/day for chronic exposure is available (15, 28). The estimated daily exposure doses for adults and children exposed to surface water and sediment are below the chronic RfD. The estimated daily exposure doses calculated for children who may be exposed to contaminated surface soils exceed the RfD at five of the six sampling units: the Swamp/Lakebed, BNR Dismantling Yard, BNR Railyard, TIP, and Amsted sampling units. The estimated daily exposure doses for adults exceed the RfD at the BNR Dismantling Yard, TIP, and Amsted sampling units.

The RfD is derived from a NOAEL of 0.005 mg/kg/day and LOAEL of 0.06 mg/kg/day in humans. These toxicity values are based on a human study which central nervous system effects, such as weakness, stiff muscles, and tremors have been observed from exposure to elevated manganese concentrations in drinking water. For further evaluation of potential noncarcinogenic health effects, the estimated daily exposure dose is compared to the NOAEL and LOAEL. The estimated daily exposure doses for children exposed to surface soils at the Swamp/Lakebed, BNR Dismantling Yard, and BNR Railyard sampling units are about two to four times greater than the NOAEL, and about three to eight times below the LOAEL. The estimated daily exposure dose for adults exposed to surface soils at the BNR Dismantling Yard unit is at the NOAEL. The estimated daily exposure doses for children exposed to surface soils at the TIP and Amsted sampling units are about 19 times greater than the NOAEL, and about 1.6 times greater than the LOAEL. While, the adult estimated daily exposure doses are about five times greater than the NOAEL and about three times less than the LOAEL.

Considering the above comparisons and present groundcover conditions at the site, recreationalists/trespassers who are exposed to manganese-contaminated soils at the Swamp/Lakebed, BNR Dismantling Yard, and BNR Railyard sampling units are unlikely to experience noncarcinogenic health effects. Children may experience neurological effects as a result of long-term exposure to manganese in surface soils at the TIP unit. Also, should the Amsted unit become accessible to recreationalists/trespassers, children may develop neurological effects from long-term exposure to manganese-contaminated surface soils.

EPA considers manganese not classifiable as to human carcinogenicity due to inadequacies in the human and animal data. Without sufficient data, the lifetime cancer risk cannot be predicted for recreationalists/trespassers exposed to manganese in surface soils, surface water, and sediment.

Nickel

Maximum concentrations of nickel were detected in surface soil samples at 472 mg/kg at the Swamp/Lakebed, 70.9 mg/kg at Airport, 173 mg/kg at the BNR Dismantling Yard, 78.4 mg/kg at the BNR Railyard, 36.6 at the TIP, and 865 mg/kg at the Amsted sampling units. In surface water, the maximum concentration of 52.6 µg/L was detected in runon samples, 18.4 µg/L in on-site samples, and 15.3 µg/L in runoff samples. Nickel was also detected in sediment samples at a maximum concentration of 408 mg/kg. Recreationalists/trespassers may be exposed to nickel through inadvertent ingestion of surface soils, surface water, and sediments. Again, dermal contact is not considered an important route of exposure for nickel.

Limited data indicate that the gastrointestinal, hematological, and cardiovascular systems in humans may be targets of toxicity after oral exposure to nickel. Nickel compounds that dissolve easily in water, such as soluble salts of nickel, absorb more readily in the body than insoluble forms of nickel. Based on an animal study, an oral RfD of 0.02 mg/kg/day for nickel soluble salts has been developed for chronic exposure (18, 28). In comparison, estimated daily exposure doses for adults and children to nickel are well below the chronic RfD. Therefore, it is unlikely that recreationalists/trespassers who are exposed to nickel-contaminated surface soils, surface water, and sediments will develop noncarcinogenic health effects.

Carcinogenic effects have not been observed in humans and animals following oral exposure to nickel. EPA has not evaluated soluble salts of nickel, as a class of compounds, for evidence of human carcinogenicity. Nickel refinery dust and specific nickel compounds, however, have been classified as known human carcinogens through inhalation. The air dispersion modeling concluded that inhalation of contaminants through the air pathway is minimal. Without additional carcinogenicity data on oral exposure, the lifetime cancer risk cannot yet be predicted for recreationalists/trespassers exposed to nickel-contaminated media.

Thallium

Exposure to thallium-contaminated surface soils and surface water may have occurred in the past, may presently be occurring, and could occur in the future by recreationalists/trespassers accessing the site. Maximum concentrations of thallium were detected in surface soil samples at 0.57 mg/kg at the Swamp/Lakebed, 0.27 mg/kg at the Airport, 2.7 mg/kg at the BNR Dismantling Yard, 0.78 mg/kg at the BNR Railyard, 0.24 mg/kg at the TIP, and 0.28 mg/kg at the Amsted sampling units. A maximum concentration of thallium detected in surface water was at 19.5 µg/L in runon samples. Thallium was not detected in on-site and runoff surface water samples or in sediment samples.

There are no available studies regarding chronic oral exposure to thallium; therefore an oral MRL for chronic exposure has not been developed. An oral LOAEL in animals for less serious effects of 0.08 mg/kg/day has been derived for intermediate exposure of 15 days to one year (21). Though several intermediate NOAELs in animals have been developed, the NOAEL exposure doses are at a higher concentrations than the LOAEL. Estimated daily exposure doses for adults and children to thallium concentrations in surface soils and surface water runon are well below this LOAEL. Exposed recreationalists/trespassers are unlikely to experience adverse noncarcinogenic health effects.

Again, there are no studies concerning chronic oral thallium exposure. Therefore, thallium has not been classified as to potential for human carcinogenicity. Until carcinogenic data becomes available, the risk of cancer cannot be predicted for recreationalists/trespassers who are exposed to thallium-contaminated media at the site.

Vanadium

Elevated concentrations of vanadium were detected in surface soil samples at the Swamp/Lakebed unit and in runon and on-site surface water samples. Exposure may have occurred in the past, may presently be occurring, and could occur in the future by recreationalists/trespassers who come in contact with vanadium-contaminated media. Ingestion of contaminated surface soils and surface water is the principal route of exposure for vanadium. Recreationalists/trespassers may be exposed to maximum concentrations of vanadium at 321 mg/kg in surface soils, 66.9 µg/L in runon surface water samples, and 146 µg/L in on-site surface water samples.

Limited data exists on chronic oral exposure to vanadium; therefore a chronic MRL has not been developed for this contaminant. However, ATSDR has derived an oral MRL of 0.003 mg/kg/day for intermediate exposure of 15 days to 1 year (23). The MRL is based on a rat study which effects on the renal system were observed after three months exposure to sodium metavanadate. In other animal studies, adverse developmental effects, cardiovascular effects, and gastrointestinal effects were observed at levels greater than the NOAEL used for the MRL. EPA has developed an oral RfD of 0.009 mg/kg/day for vanadium pentoxide based on the rat study. Estimated daily doses for adults and children exposed to vanadium-contaminated surface soil and surface water are below the intermediate MRL and chronic RfD. Recreationalists/trespassers who are exposed to vanadium-contaminated media are not anticipated to experience noncarcinogenic health effects.

Currently, there are no studies regarding the carcinogenicity of vanadium in humans, and animal studies are inadequate to be used in evaluating carcinogenic effects. Without additional data, the carcinogenic potential of vanadium cannot be determined. The lifetime cancer risk cannot be estimated for recreationalists/trespassers who may be exposed to vanadium at the site.

Zinc

Recreationalists/trespassers may have exposed in the past, may currently be exposed, and could be exposed in the future through inadvertent ingestion of zinc-contaminated surface soils and surface water. Zinc was detected in surface soil samples at maximum concentrations of 24,200 mg/kg at the BNR Dismantling Yard and 61,600 mg/kg at the Amsted sampling units, and in on-site surface water at 3,160 µg/L.

As an essential element for humans, Recommended Dietary Allowances (RDA) for zinc are estimated at 15 mg/day for men and 12 mg/day for women. The RDA of 15 mg/day is equivalent to 0.21 mg/kg/day for an average adult male of 70 kg. Large doses of zinc about 10 to 15 times higher than the RDA can cause adverse effects. The principal effects observed in humans following oral exposure include abdominal pain, vomiting, anemia, decreased high-density lipoprotein cholesterol, and pancreatic damage. Renal effects have also been seen in animals but not in humans. EPA developed an oral RfD of 0.3 mg/kg/day for chronic exposure based on a human diet supplement study (24, 28).

Estimated daily exposure doses for adults and children exposed to zinc-contaminated surface soils at the BNR Dismantling Yard and Amsted sampling units, as well as on-site surface water do not exceed either the chronic RfD or RDA. Therefore, recreationalists/trespassers are not anticipated to experience noncarcinogenic health effects from exposure to zinc.

Currently, EPA considers zinc not classifiable as to potential for human carcinogenicity because of inadequate evidence in humans and animals. The lifetime cancer risk cannot be estimated for recreationalists/trespassers exposed to zinc-contaminated surface soils and surface water at the site.

Volatile Organic Compounds

Methylene Chloride

Concentrations of methylene chloride were detected in on-site surface water samples during the wet season sampling event at a maximum concentration of 8 µg/L. Recreationalists/trespassers may have been exposed, may presently be exposed, and could be exposed in the future to contaminated surface water during water activities on the site. Exposure to methylene chloride can occur primarily through accidental ingestion of water and inhalation of vapors. Absorption through dermal contact is minimal for methylene chloride. Though inhalation is a primary route of exposure for methylene chloride, the actual concentration recreationalists/trespassers may be exposed to is considered insignificant because of such low concentrations of methylene chloride in surface water volatilizing into a large volume of ambient air.

In evaluating noncarcinogenic health effects, the ATSDR oral chronic MRL of 0.06 mg/kg/day for methylene chloride was compared to estimated daily exposure doses for adults and children. Estimated daily exposure doses do not exceed the MRL. Recreationalists/trespassers who are exposed to methylene chloride in surface water are not anticipated to develop noncarcinogenic health effects.

EPA classifies methylene chloride as a probable human carcinogen, and has derived an oral cancer slope factor of 7.5E-3 (mg/kg/day)-1. Based on the estimated daily exposure dose and cancer slope factor, long-term exposure to methylene chloride in surface water recreationalists/trespassers should have no increased risk of developing cancer over a lifetime (16, 28).

Semi-Volatile Organic Compounds

Bis(2-ethylhexyl)phthalate

Exposure in the past, present exposure, or future exposure to bis(2-ethylhexyl)phthalate may have occurred or may occur through incidental ingestion of contaminated surface water and sediments during recreational activities. Recreationalists/trespassers may be exposed to bis(2-ethylhexyl)phthalate in surface water at maximum concentrations of 55 µg/L in on-site samples and 75 µg/L in runoff samples, as well as in sediments at a maximum concentration of 160 mg/kg.

No ATSDR chronic oral MRL exists for bis(2-ethylhexyl)phthalate; however EPA has derived a chronic oral RfD of 0.02 mg/kg/day. Animal studies show that bis(2-ethylhexyl)phthalate can have adverse effects on the liver, testes, kidney, thyroid, and pancreas. Estimated daily exposure doses for adults and children to bis(2-ethylhexyl)phthalate in surface water and sediments do not exceed the RfD. Exposure to bis(2-ethylhexyl)phthalate by recreationalists/trespassers is unlikely to result in noncarcinogenic health effects.

Bis(2-ethylhexyl)phthalate is classified as a probable human carcinogen based on increase liver tumor responses in rats and mice. From a mouse study, EPA derived an oral cancer slope factor of 1.4E-2 (mg/kg/day)-1. Recreationalists/trespassers should have no increased risk of developing cancer over a lifetime bis(2-ethylhexyl)phthalate in surface water and sediments (13, 28).

3,3'- Dichlorobenzidine

Recreationalists/trespassers may have been exposed in the past, may presently be exposed, and could be exposed in the future to 3,3'- dichlorobenzidine through accidental ingestion of surface soils at the BNR Railyard unit. A maximum concentration of 3,3'- dichlorobenzidine of 9.7 mg/kg was detected in surface soil samples from this unit.

Current toxicity data is insufficient to derive a chronic oral MRL or RfD. Limited data indicate that long-term exposure in animals to 3,3'- dichlorobenzidine can cause developmental and liver effects. Estimated daily exposure doses calculated for adults and children exposed to 3,3'-dichlorobenzidine-contaminated surface soils are low. The majority of BNR Railyard unit has a groundcover of grasses and small shrubs which reduce the potential for direct contact with surface soils. Under these assumptions, recreationalists/trespassers should not develop noncarcinogenic health effects from exposure to 3,3'- dichlorobenzidine in surface soils at the site.

Based on inadequate human data and sufficient animal data, EPA classifies 3,3'- dichlorobenzidine as a probable human carcinogen and derived an oral cancer slope factor of 4.5E-1 (mg/kg/day)-1. Animal studies indicated that 3,3'- dichlorobenzidine can cause cancer of the liver, skin, mammary gland, bladder, and leukemia as well as other sites. Long-term exposure of recreationalists/trespassers to 3,3'- dichlorobenzidine in surface soils should result in no increased risk of developing cancer over a lifetime (12, 28).

Pentachlorophenol

Pentachlorophenol was detected in surface water at maximum concentrations of 6 µg/L in on-site samples and 0.7 µg/L in runoff samples. Exposure may have occurred in the past, may presently be occurring, and could occur in the future to recreationalists/trespassers through incidental ingestion of surface water.

In humans, long-term exposure to low levels of pentachlorophenol can cause damage to the liver, kidney, blood, and nervous system. Adverse effects to the immune system were also observed in animal studies. An EPA chronic oral RfD of 0.03 mg/kg/day for pentachlorophenol was developed based on a rat study indicating liver and kidney effects. In comparison, estimated daily exposure doses for adults and children exposed to maximum concentration of pentachlorophenol in surface water are well below the RfD. Long-term exposure of recreationalists/trespassers to pentachlorophenol in surface water should not result in noncarcinogenic health effects.

Pentachlorophenol is classified by EPA as a probable human carcinogen. This classification is based on inadequate human data and sufficient evidence of carcinogenicity in animals. From carcinogenicity data, a cancer oral slope factor of 1.2E-1 (mg/kg/day)-1 has been derived for pentachlorophenol. Using the cancer slope factor with the estimated daily exposure dose, it is predicted that recreationalists/trespassers should have no increased risk of developing cancer from exposure to pentachlorophenol in surface water (20, 28).

Polycyclic Aromatic Hydrocarbon Compounds

Exposure to polycyclic aromatic hydrocarbon (PAH) compounds may have occurred in the past, may presently be occurring, and could occur in the future. Recreationalists/trespassers may be exposed through incidental ingestion of PAH-contaminated surface soils, surface water, and sediments, and dermal contact with soils and sediments that contain high levels of PAHs.

Ten PAH compounds detected in surface soil, surface water, and sediment samples collected during the Phase I investigations were selected as contaminants of concern. The compounds are benz(a)anthracene, benz(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, benzo(k)fluorene, chrysene, dibenzo(a,h)anthracene, indeno(1,2,3-c,d)pyrene, naphthalene, and phenanthrene. Note that specific PAH compounds were not determined for surface soil samples collected during the Phase II investigation. Instead, results were reported only as total PAHs and total probable carcinogenic PAHs.

The range of concentrations for specific PAHs, total PAHs, and total probable carcinogenic PAHs observed in surface soils are listed in Appendix - B, Table I, "Contaminants of Concern in On-site Surface Soils, Phase I and Phase II." The maximum concentrations of total PAHs in surface soil samples were detected at 46.7 mg/kg at the Swamp/Lakebed, 25.0 mg/kg at the Airport, 105.3 mg/kg at the BNR Dismantling Yard, 70.4 mg/kg at the BNR Railyard, 37.0 mg/kg at the TIP, and 30.3 mg/kg at the Amsted sampling units. The maximum total probable carcinogenic PAH concentrations are at 34.2 mg/kg at the Swamp/Lakebed, 12.6 at the Airport, 38.5 mg/kg at the BNR Dismantling Yard, 24.5 mg/kg at the BNR Railyard, 10.6 mg/kg at the TIP, and 10.2 mg/kg at the Amsted sampling units.

Maximum concentrations of specific PAHs detected in surface water samples are presented in Appendix - B, Table 4, "Contaminants of Concern in On-site Surface Water." Maximum concentrations of total PAHs and total probable carcinogenic PAHs observed in on-site surface water samples were at 39 µg/L and 14 µg/L, respectively.

In Appendix - B, Table 5, "Contaminant of Concern in On-site Sediments," the maximum concentrations of specific PAHs, total PAHs, and total probable carcinogenic PAHs found in sediment samples are listed. The maximum concentrations of total PAHs and total probable carcinogenic PAHs detected in sediment samples are at 560 mg/kg and 200 mg/kg, respectively.

Currently, no chronic oral ATSDR MRL or EPA RfD is available for the PAH compounds recognized as site contaminants of concern. However, noncarcinogenic health effects are associated with PAH exposure in animals including effects of the gastrointestinal, hematological, hepatic, and immune systems, as well as adverse reproductive and developmental effects. Adverse dermal effects, such as chronic dermatitis and hyperkeratosis, have also been observed in both humans and animals. Current toxicity data is insufficient to identify threshold levels for appropriate noncarcinogenic effects; therefore, chronic oral MRL or RfD cannot be developed for specific PAH compounds. Until additional toxicity data becomes available, noncarcinogenic health effects cannot be predicted for recreationalists/trespassers who may be exposed to PAH-contaminated media at the site.

Occupational studies indicate that workers exposed to mixtures containing PAHs through inhalation and dermal contact have developed lung and skin cancer, respectively. Animal studies demonstrated certain PAHs to be carcinogenic following inhalation, ingestion, and dermal exposure. Based on sufficient animal data and inadequate human data, EPA has classified several PAHs as probable human carcinogens. The probable carcinogenic PAHs detected at the site are benzo(a)anthracene, benz(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, dibenz(a,h)anthracene, and indeno(1,2,3-c,d)pyrene. EPA has derived a cancer slope factor for one PAH compound, benz(a)pyrene, of 7.3 (mg/kg/day)-1.

The cancer slope factor for benz(a)pyrene was used to evaluate the potential cancer risk from exposure to total probable carcinogenic PAHs found at the site. From this evaluation, recreationalists/trespassers exposed to PAH-contaminated surface soils at the Airport, TIP, and Amsted sampling units should experience no increased risk of developing cancer over a lifetime. Recreational exposure to PAH levels in surface soils at the Swamp/Lakebed, BNR Dismantling Yard, and BNR Railyard units should result in no apparent increased risk of developing cancer. Though no increased cancer risk is predicted from exposure to on-site surface water, recreationalists/trespassers may have a low increased risk of developing cancer over a lifetime from long-term exposure to PAH-contaminated sediments (19, 28).

Polychlorinated Biphenyl Compounds

Commercial polychlorinated biphenyl (PCB) mixtures produced in United States were primarily composed of Aroclor. During the remedial investigation, samples were analyzed for the PCB compounds: Aroclor 1242, Aroclor 1248, Aroclor 1254, and Aroclor 1260. Two compounds, Aroclor 1254 and Aroclor 1260, were detected in surface soil and sediment samples.

PCBs were found in surface soil samples from the BNR Dismantling Yard and BNR Railyard sampling units. At the BNR Dismantling Yard unit, the maximum concentrations of Aroclor 1254 and Aroclor 1260 observed were at 9 mg/kg and 0.44 mg/kg, respectively. The maximum concentration of total PCBs detected at a particular sample location within BNR Dismantling Yard unit was at 9 mg/kg. Maximum concentrations of Aroclor 1254 and Aroclor 1260 detected in surface soil samples from the BNR Railyard unit were at 42 mg/kg and 1 mg/kg, respectively, with the maximum concentration of total PCB at 42 mg/kg.

In addition, four soil borings were collected during the Phase II investigations from the Pioneer Builders Supply property. Though the property is mostly paved, borings were completed beneath asphalt and samples were at five-foot intervals ranging 0 (surface) to 30 feet below ground surface. PCB (Aroclor 1260) was detected in one of the four soil borings, and for this particular boring, the "surface" soil sample had a concentration of Aroclor 1260 at 56 mg/kg. Maximum concentrations of PCBs detected in sediment samples were Aroclor 1254 at 1.8 mg/kg and Aroclor 1260 at 4 mg/kg. A maximum total PCB concentration of 4 mg/kg was observed in sediments.

Recreationalists/trespassers may have been exposed, may presently be exposed, and could be exposed in the future to PCBs through accidental ingestion of and dermal contact with contaminated surface soils and sediments. Because current data is insufficient in relating contributions of dermal exposure to PCB toxicity, the significance of dermal contact with PCB-contaminated media cannot be predicted.

Based on immunological effects observed in animal studies, ATSDR developed an oral MRL for PCBs of 0.00002 mg/kg/day for chronic exposure. The chronic MRL was compared to estimated daily exposure doses calculated for adults and children exposed to PCB-contamination at the site. The estimated daily exposure dose for children exposed to the maximum concentration of total PCBs in surface soils at the BNR Dismantling Yard unit slightly exceeds the MRL. Both adult and child estimate daily exposure doses exceed the MRL for exposure to the maximum concentration of total PCBs in surface soils at the BNR Railyard unit. In addition, estimated daily exposure doses for adults and children exposed to Aroclor 1260 in surface soils at the Pioneer Builders Supply property exceed the MRL. Estimated daily exposure doses for adults and children exposed to PCB-contaminated sediments are below the MRL.

The chronic MRL was derived from a LOAEL of 0.005 mg/kg/day for less serious effects in animals with an uncertainty factor of 300. The child estimated daily exposure dose based on PCB exposure at the BNR Dismantling Yard unit is about 1.6 times greater than the MRL and 156 times less than the LOAEL. For the BNR Railyard unit, the adult estimated daily exposure dose is about 1.8 times above the MRL and about 135 times below the LOAEL, while the child estimated daily exposure dose is about 7.5 times above the MRL and 33 times below the LOAEL. Adult estimated daily exposure dose for the Pioneer Builders Supply property is determined to be about 2.4 times above the MRL and 102 times below the LOAEL, and the child estimated daily exposure dose about 10 times above the MRL and 25 times below the LOAEL. Based on these comparisons and the uncertainty factor involved, long-term exposure of children, particularly sensitive individuals, to PCBs in surface soils at the BNR Railyard unit and Pioneer Builders Supply property may potentially be a health concern.

The Pioneer Builders Supply property is paved and fenced; therefore exposure of children to surface soils is unlikely to occur. Total PCBs were observed at elevated concentrations of 42 mg/kg, 17 mg/kg, and 15 mg/kg in surface soil samples collected within the northern portion of BNR Railyard unit. The sample location 586 from which total PCBs of 42 mg/kg was detected is the only location of health concern for children should frequent exposure to surface soils occur over an extended period of time. Actual exposure to PCB-contaminated surface soils will depend on several factors, such as accessibility to this sample location and existing groundcover.

Evidence from animal studies suggest oral exposure to PCBs can result in numerous health effects to systems including hepatic, gastrointestinal, hematological, dermal, immunological, neurological, developmental and reproductive systems. Limited dermal studies involving animals indicate adverse hepatic, renal, dermal, immunological, and body weight effects. At the lowest chronic oral LOAEL of 0.005 mg/kg/day, a monkey study reveals immunological effects from exposure to Aroclor 1254 (21). Limited data from human studies are inconclusive regarding immunological effects; however PCBs are known to alter immune responses in a variety of animal species, which suggests humans may also be affected. In conclusion, children particularly sensitive individuals, who frequent the BNR Railyard sample location 586 may experience adverse immunological effects from long-term exposure to PCB-contaminated surface soils.

As a group, PCBs are classified by EPA as a probable human carcinogen with a cancer slope factor of 7.7 (mg/kg/day)-1. The classification is supported by evidence of liver cancer in animals, and suggestive evidence of excess liver cancer in human. Long-term exposure of recreationalists/trespassers to PCB-contaminated sediments or surface soils at the BNR Dismantling Yard unit should result in no increased risk of developing cancer over a lifetime. Recreationalists/trespassers should have no apparent increased risk of developing cancer over a lifetime from exposure to PCB-contaminated surface soils at the BNR Railyard unit and Pioneer Builders Supply property (21, 28).

B. Health Outcome Data Evaluation

Based on the toxicological evaluation, cancer is a possible health outcome for recreationalists/trespassers exposed to arsenic, lead, and carcinogenic PAHs at the site. To address cancer as a health outcome for recreationalists/trespassers, information from the CSS database at the Fred Hutchinson Cancer Research Center was evaluated. Though the CSS database does not specifically address cancer occurrences for the exposed population, it does have cancer occurrence data available for residents who live near the site. These residents are likely to makeup a portion of the exposed population. Residents of the three census tracts located nearest to the site for the time period 1980 through 1990 were chosen as the study group to be evaluated for cancer occurrence.

The cancer types of interest selected to be evaluated from the cancer occurrence data are esophagus, stomach, liver, larynx, lung, female breast, kidney, and all types of leukemia. Though skin cancer is a possible health outcome for arsenic exposure, this cancer type is not included in the cancer occurrence data and therefore cannot be evaluated.

Cancer Occurrence

Cancer occurrence rates (i.e., number of cancer cases per 100,000 residents during 1980 through 1990) were obtained to determine if the incidence of cancer in residents living near the site was different than that of all the residents of 13 counties in northwest Washington State. Cancer incidence rates for a) all cancer combined, b) all cancer types of interest combined, and c) each cancer type of interest were compared.

This comparison showed similar incidence rates for all cancers combined, cancer types of interest combined, female breast cancer, stomach cancer, and leukemia among the two resident populations. In conclusion, there is no indication of elevated rates of the above cancer types in residents living in the three census tracts around the South Tacoma Field site during 1980 through 1990. For cancer of the esophagus, stomach, liver, and larynx, there was insufficient data available for analysis due to the medical confidentiality requirements of the cancer registry.

However, the initial comparison of lung cancer incidence rates between the two populations showed a higher than expected rate in residents living near the site. To determine if this higher rate was unique for the three census tracts, or caused by some other factor, it was compared to the rate for the entire Pierce County population for 1980 through 1990. This comparison revealed that the lung cancer incidence rates for residents of the three census tracts and residents of the entire county were similar. The incidence rate of lung cancer in Pierce County ranks fourth highest of 17 regions for which data are available in Washington State. The higher rate of lung cancer in the resident population when compared to the 13 northwest Washington counties population is most likely the result of the higher overall rate seen in Pierce County.

From the comparison of lung cancer rates, it appears there is not a detectable increase in cancer in the residents living in the three census tracts around the South Tacoma Field site.

C. Community Health Concerns Evaluation

The community has not expressed health concerns regarding conditions at the South Tacoma Field site. Consequently, there are no site-related community health concerns to be addressed in this subsection. Lack of community interest maybe due to the fact that the site is located in a heavy industrial district, not a residential district.



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