PUBLIC HEALTH ASSESSMENT
HILL AIR FORCE BASE
HILL AIR FORCE BASE, DAVIS AND WEBER COUNTIES, UTAH
ENVIRONMENTAL CONTAMINATION, HUMAN EXPOSURE PATHWAYS, AND PUBLIC HEALTH IMPLICATIONS (CONT.)
Summary
From our visits, discussions with base personnel, and information review, ATSDR identified two ways people living in Riverdale can come in contact with environmental contaminants originating from Hill AFB: groundwater contamination off-gassing into indoor air and contact with contaminated springs.
Background
Riverdale, which comprises 4.4 square miles, is north of Hill AFB. The section of Riverdale that is closest to Hill AFB is the Craigdale subdivision. Craigdale consists of approximately 80 homes and borders Hill AFB. The Farr subdivision is the next area in proximity to Hill AFB. Contamination from former base operations and waste disposal practices has spread north and affected groundwater in Riverdale. Sources of contamination that have created the contamination in Riverdale are listed in Table 2 and described in Table 18 of this document. Two plumes of groundwater contamination affect the community of Riverdale, one as part of OU-6 and the other as part of OU-4. The OU-4 plume under lays approximately 50 acres of primarily farm fields and sparsely vegetated hill slopes in Riverdale. The OU-6 plume under lays approximately 60 acres of a residential area known as the Craigdale subdivision in Riverdale (ATSDR 2002a). The USAF began initial sampling and analysis for contamination in the Riverdale area in 1988. This sampling identified contamination, primarily VOCs and metals. Contamination in Riverdale is related to Operable Units 4 and 6 at Hill AFB.
At the request of Hill AFB in March 1994, ATSDR commented on the public health implications of contaminants affecting Riverdale and the portion of Hill AFB nearest Riverdale (ATSDR 1994). ATSDR presented findings in a health consultation after a review of base-related records and reports, interviews with base personnel and off-base residents, and two base visits. At the time, ATSDR concluded that VOCs were not present in the indoor air in the Riverdale area at levels that represented a health threat. ATSDR also found that VOCs were not present in groundwater or surface water at levels representing a health threat for people who occasionally contact the water or use it for irrigation, nor would the VOCs be expected to bioaccumulate to harmful levels in fruits and vegetables grown in Riverdale.
In March 1998, the USAF prepared a report regarding the public health implications of the contaminants detected in the Riverdale area. The USAF concluded that TCE was the primary contaminant in the shallow groundwater aquifer in the area, but that the contamination did not impact area drinking water supplies. They concluded that no human health risk resulted from the contamination in Riverdale (HAFB 1998a).
The USAF has taken remedial actions to reduce groundwater contamination in Riverdale and to limit its further migration. Landfill 1 was capped in May 1996 and a horizontal drain collection and treatment system upgrade was completed in June 1997. Groundwater and surface water extraction was done in June 2001 (ATSDR 2002f). Additionally, fences have been placed around the Landfill 1 Cap, restrictions on issuance of future water rights in the area of contamination have been imposed, and wording was added to the Air Force Instruction, AFI 32-7020, to restrict construction or other activities that will disturb the soil or ground water in the area (HAFB 1998a).
To further reduce contamination spread in Riverdale, hybrid poplar trees were planted in August 2001 (ATSDR 2002f). The poplar trees use TCE as a carbon source, removing it from the groundwater. It is anticipated that the poplar trees will provide hydraulic control to limit the continuing mass flow of TCE into Riverdale (ATSDR 2002a). Additionally, air strippers have been installed near Cooley Pond and the Craigdale subdivision.
Riverdale Sampling
The groundwater contamination in Riverdale has spread to the surface water (Radian 1995b). The USAF conducted sampling for surface water from 1988 until the late 1990s. The most predominant contaminants found in the groundwater in Riverdale are the VOCs TCE (up to 329 ppb), methylene chloride (7 ppb), and benzene (up to 53 ppb) (HAFB 1994; Radian 1997). These chemicals move easily through groundwater and evaporate when exposed to air. The groundwater aquifer is not far from the ground surface. The VOCs in the groundwater are exposed to air and are able to evaporate, seeping into homes above pockets of VOC contamination.
Two VOC groundwater plumes resulting from leaks and spills at Hill AFB have migrated north of Hill AFB, toward and beneath homes in Riverdale (Figure 2). The most predominant contaminant in these plumes is TCE.
Indoor air was sampled in 14 basements in the Craigdale subdivision three times from December 1992 through February 1994 (Radian 1995b). Additionally, during the same sampling events, two locations away from the groundwater contamination, representing background locations, were monitored. Nine of the residences where air sampling was conducted were actually within the known extent of the TCE groundwater plume (Radian 1997).
Indoor Air Exposure in Riverdale
There are approximately 2,970 homes in Riverdale, with only 80 in the area nearest the base (Craigdale subdivision). A majority of the city of Riverdale has no exposure to the contaminants that have migrated off base into the Craigdale subdivision (Figure 2). Of the 80 homes above the groundwater plume, the USAF sampled indoor air in the basements of 14 residences. TCE, TCA, and chloroform were detected frequently. 1,1-DCE was detected in 15% of the samples at low levels for each sample. Vinyl chloride and 1,1,2,-trichloroethane were not detected.
Remedial actions instituted by the USAF in the area of the groundwater plumes
affecting Riverdale were begun after the indoor air sampling was performed (HAFB
1994; Radian 1997). Considering this, the indoor air sampling results from the
1992-1994 time frame in Riverdale likely represent a worst-case situation for
residents of these communities. Future indoor air concentrations in Riverdale
are expected to decrease.
Highest Concentrations Detected
TCE (up to 4.3 ppb) and 1,1,1-TCA (up to 41 ppb) were detected in indoor air in homes in the Craigdale subdivision. One sampling location, a garage sump enclosure, had a higher detected TCE measurement of 117.5 ppb. Access to this location is limited, however, to daily visits of short duration by a USAF contractor involved with monitoring the performance of the treatment system at this location (Radian 1995b). This concentration is much higher than the other detected levels of TCE. The next highest concentration detected was 4.3 ppb.
Chloroform (up to 5 ppb) was also detected in the indoor air. Chloroform, however, was not detected in soil or groundwater in Riverdale, nor has it been associated with past operations at the Hill AFB source areas affecting Riverdale. Therefore, the potential source of chloroform is unknown. Chloroform is a degradation product of carbon tetrachloride, but the use of carbon tetrachloride was reported in only one building on base. Furthermore, carbon tetrachloride has not been detected in any other media in the area. These data indicate that the occurrences of are chloroform in groundwater appear unrelated to the VOC plume and detected concentrations in the Craigdale subdivision (HAFB 1995).
The garage spring enclosure had a TCE concentration above commonly detected levels (1.3 ppb), while the average of the other TCE measurements in the Craigdale subdivision was below commonly detected levels. The maximum detected concentrations of TCA and chloroform in the Craigdale subdivision were below commonly detected levels (48.9 ppb and 8.4 ppb, respectively).
Exposure Evaluation
Exposure doses were calculated for the maximum detected concentrations for TCE, TCA, and chloroform. The concentration of TCE found in the garage sump enclosure is also included in our analysis. ATSDR conservatively assumed that adults and children were exposed to the maximum and average contaminants constantly for 24 hours a day/365 days per year. The exposure dose for the maximum concentration of TCA found in indoor air in homes in Riverdale was more than ten times lower than the EPA inhalation reference doses (Table 12). Adverse health effects should not result from exposure to this level of contamination in homes. For a more detailed analysis, see Table 23 in the Tables section at the end of this document.
TCE and chloroform, detected in the indoor air in Riverdale, are suspected carcinogens. The estimated excess lifetime cancer risk for TCE is below levels likely to result in either cancerous or non cancerous health effects. Adverse health effects are not expected for humans exposed to these levels of TCE and chloroform in their homes. The maximum exposure dose for TCA is far below the EPA Reference Dose. As a result, ATSDR concludes that no health hazard exists in Riverdale.
Table 12. Riverdale Housing Area In-Home Indoor Air Measurements (1992 to 1994)
| Compound | Maximum Concentration (ppb) | Common National (ppb) | Rick (unitless)/Dose (mg/kg/day) | Comparison Value (units) |
Source |
| Carcinogens | |||||
| TCE | 4.8 | 1.3 | 1.7E-05 | - | - |
| Chloroform | 5 | 8.4 | 24E-05 | - | - |
| Noncarcinogen | |||||
| TCA | 41.35 | 48.9 | 90E-05 | 600E-05 mg/kg/day | EPA Reference Dose |
Indoor Air Modeling for Riverdale-Past Exposures
It was unclear whether the indoor air sampling was conducted when the groundwater contamination under the homes was at its worst. Therefore, ATSDR used a model to estimate whether intrusion of the highest levels would have presented a health hazard. TCE, methylene chloride, and benzene were the only detected VOCs in the groundwater beneath Riverdale that had corresponding information available for use in the model. The maximum concentration of TCE, 15,000 ppb, was entered in the model. The model indicated an indoor air concentration of 998 ppb, which was far lower than the LOAEL (ATSDR 1997b). The maximum groundwater concentration, found near the Davis-Weber Canal, was chosen to serve as a worst-case scenario. Indoor air sampling has not detected TCE concentrations near this magnitude. The highest groundwater concentration of TCE found in the Craigdale subdivision is 187 ppb (Radian 1997). This concentration was entered into the model and resulted in an indoor air concentration of 13 ppb, far below levels that may cause adverse health effects.
The maximum concentration of methylene chloride, 7 ppb, was entered in the model. The model resulted in an indoor air concentration of 0.5 ppb, which was far lower than the NOAEL (ATSDR 2000). The maximum concentration of benzene, 53 ppb, was entered in the model. The model resulted in an indoor air concentration of 6 ppb, which was far lower than the LOAEL (ATSDR 1997a). Based on the modeling results, ATSDR would not expect residents of homes above the plumes to become sick or develop adverse health effects associated with the low levels of indoor air contaminants.
Surface Water Exposures for Residents of Riverdale
The USAF began surface water sampling in Riverdale as early as 1988 and continued sampling until the late 1990s. Surface water in Riverdale in the vicinity of Hill AFB includes one spring, two field drains, an off-base pond (Cooley's Pond), and the Davis-Weber Canal. Cooley's Pond is north of the Davis-Weber Canal near the southernmost home on 1200 West. It is a lined, artificial pond that is fed from the contaminated Cooley garage spring (ATSDR 2002a). One of the field drains in the northern section of the Farr subdivision, while the other is found near the intersection of 1150 West and 5600 South. Groundwater, springs, and field drains in this area are hydraulically connected; therefore, surface water near the groundwater plume area as well as Cooley's Pond contain contaminants, but at a lower levels than found in the groundwater. Four VOCs have been detected in the springs: TCE (up to 180 ppb), chloroform (up to 3 ppb), 1,1,1-TCA (up to 2.5 ppb), and cis-1,2-DCE (up to 2.1 ppb) (Radian 1995b). Samples collected from the Davis-Weber Canal did not contain contamination. Samples taken from Cooley's Pond show low levels of TCE contamination (below MCLs). The pond is currently being treated (ATSDR 2002a).
People come into contact with surface water in Riverdale in two ways: through accidental ingestion of water from springs and through dermal contact of the surface water in the springs. Exposure doses were calculated for each of these chemicals for both accidental ingestion and dermal contact.
Dermal Contact
The maximum dermal exposure doses for TCE, chloroform, 1,1,1-TCA, and cis-1,2-DCE are substantially lower than their EPA adjusted reference doses (Table 13). Adverse health effects should not result from exposure to this level of contamination in surface water in Riverdale.
Table 13. Riverdale Surface Water Measurements-Dermal
| Compound | Maximum Concentration (ppm) | Dose (mg/kg/day) | Comparison Value (mg/kg/day) | Source |
| TCE | 0.180 | 80E-05 | 100E-05 | Adjusted EPA Reference Dose |
| Chloroform | 0.003 | 2.61E-05 | 500E-05 | Adjusted EPA Reference Dose |
| TCA | 0.0025 | 30E-05 | 14000E-05 | Adjusted EPA Reference Dose |
| Cis-1,2-DCE | 0.0021 | 0.0399E-07 | 500E-05 | Adjusted EPA Reference Dose |
Ingestion of Surface Water
The maximum exposure doses for water ingestion for TCE, chloroform, TCA, and cis-1,2-DCE were more than ten thousand times lower than their EPA oral reference doses (Table 14). Adverse health effects are not expected for humans exposed to these levels of TCE, chloroform, TCA, and cis-1,2-DCE through accidental ingestion to contaminated surface water in Riverdale.
Table 14. Riverdale Surface Water Measurements-Ingestion
| Compound | Maximum Concentration (ppb) | Dose (mg/kg/day) | Comparison Value (mg/kg/day) | Source |
| TCE | 180 | 0.0563E-05 | 600E-05 | EPA Oral Reference Dose |
| Chloroform | 3 | 0.000781E-05 | 1000E-05 | EPA Oral Reference Dose |
| TCA | 2.5 | 0.000938E-05 | 28000E-05 | EPA Oral Reference Dose |
| Cis-1,2-DCE | 2.1 | 0.000656E-05 | 1000E-05 | EPA Oral Reference Dose |
Summary
From our visits, discussions with base personnel, and information review, ATSDR identified two ways people living in South Weber can come in contact with environmental contaminants originating from Hill AFB: groundwater contamination off-gassing into indoor air and contact with contaminated springs.
Background
South Weber, which has a land area of 4.6 square miles, is to the east of Hill AFB. Contamination from former base operations and waste disposal practices on Hill AFB has spread, affecting soil and groundwater in South Weber. The USAF began soil and groundwater sampling in South Weber in the early 1980s to determine the extent of contamination. Contamination in the soil, resulting from former chemical waste disposal activities, has spread to the shallow groundwater aquifer. Sources of contamination that have created the contamination in South Weber are listed in Table 2 and described in Table 18 of this document.
As part of remedial activities for South Weber, a Source Recovery System was installed in 1993 to remove DNAPL from the area near CDP 3. Landfill 1 (part of OU-4) was capped in May 1996. Groundwater extraction trenches were installed in June 2001 to limit contaminant migration from CDPs 1 and 2 and FTA 1. Additionally, municipal water connections were provided to homes known to have been affected by contamination in the area. Also, hybrid poplar trees were planted in August 2001 to contain the plume affecting South Weber and Riverdale (ATSDR 2002e). The trees are used as part of a treatability study being conducted to assess their viability to intercept and contain contaminated groundwater (ATSDR 2002a).
The USAF also identified contaminants in South Weber Well # 2, a drinking water well within the groundwater plume in South Weber on the eastern boundary of the base. This well was used sporadically over the years during peak demand periods. In 1996, the submersible pump motor in the well failed, and customers of the South Weber drinking water system complained of an oily petroleum hydrocarbon odor. The pump and motor were removed for repairs and oil was observed floating on top of the water column in the well. Approximately 300 gallons of oil were removed from the well in May 1997. The pump and motor were reinstalled in the well, and on July 3, 1997, water produced from the well was tested. The water was found to contain VOCs at less than the detection limit (HAFB 1998c).
In August 1997, an oil odor was again noticed emanating from the well. Oil was observed on water produced from the well during flushing. The submersible pump motor subsequently failed, and VOCs were detected in samples taken from water collected in the discharge piping (CH2M Hill 1998). Benzene (15.3 ppb), chloroform (1.7 ppb), ethylbenzene (1.1 ppb), styrene (1.2 ppb), toluene (11.1 ppb), and total xylenes (2.5 ppb) were detected in the discharge pipe at the wellhouse after the pump failed. At this point, the well was taken off line. To determine if the source of the light non-aqueous phase liquid (LNAPL) in the well could be attributed to contamination from Hill AFB, additional sampling was performed. The analysis confirmed that the LNAPL from the well was significantly different from the contamination that was present in the Hill AFB plume (Weston Engineering 1997). The well was taken off-line as soon as the pump failed. Any exposure that took place was short in duration, and far below levels that could present adverse health effects.
The chemicals found in the off-base portion of the OU-1 plume where Well #2 is located are primarily composed of 1,2-DCE. 1,2-DCE was not detected in the analysis of the oil found in the well. Additionally, the LNAPL associated with OU-1 is restricted to the source area on base. Hill AFB concluded that the probable cause of the problem was from contaminated oil used when the well was serviced. Therefore, the problem was not connected to the contaminated groundwater associated with the OU-1 plume (ATSDR 2002a).
South Weber Sampling
Results of the groundwater and soil sampling have helped identify two shallow groundwater contamination plumes (Figure 2). No contamination has been detected in the deeper aquifer, which is the source of drinking water for residents of South Weber (HAFB 1994, 1998b). The largest plume associated with OU-1 consists of cis-1,2-DCE and lower concentrations of TCE. The highest measured concentration of TCE is 2,400 ppb. The highest 1,1,1-TCA concentration is 26,000 ppb. Higher concentrations of petroleum hydrocarbons have been measured in the source area.
Several South Weber private residences are above the groundwater contamination plumes. In 1990, 1993, and 1994-1995, the USAF sampled the indoor air in South Weber homes located over the groundwater plumes to determine whether contaminants had migrated into the homes and affected indoor air quality. The sampling rounds are summarized below.
South Weber (1990) Indoor Air Exposure
The USAF conducted air sampling in May 1990 in one private residence on West South Weber Drive in South Weber. Sampling was performed in May and June for three reasons: groundwater elevations are highest at this time of the year; it is one of the two times during the year when TCE levels inside the basement could be expected to be highest; and windows will be closed, creating additional insulation allowing TCE to build up in the house (HAFB 1993). In 1990, pumps were placed 2-5 feet in front of the basement wall and 2-3 feet above the ground for 1,470 minutes (24.5 hours) to pull in air and collect contaminants on charcoal filters. No TCE was detected in the 1990 sampling on West South Weber Drive (at a detection limit of 3,700 ppb), while 1,1,1-TCA was detected at 4 ppb (USGS 1992).
South Weber (1993) Indoor Air Exposure
The second round of sampling, performed on the same home as the 1990 sampling, used the SUMMA canister method, with a lower detection limit of about 1 ppb. TCE was detected on two of the four sampling days, with a maximum concentration of 0.74 ppb. TCA (up to 144 ppb) and chloroform (up to 0.23 ppb) were also detected (North American Weather Consultants 1993).
South Weber (1994-1995) Indoor Air Exposure
During the 1993 sampling, two homes, thought to represent worst-case conditions of VOCs in indoor air, were selected. One home on South Weber Drive was sampled in May 1994 because it is above groundwater containing cis-1,2-DCE and has a sump where basement air comes into contact with groundwater, increasing the likelihood of volatilization of groundwater contaminants into the basement air. Indoor air was also evaluated at a home on South 850 East in July 1995 because this home is in close proximity to Hill AFB. Given that this home did not have a sump, its exposure potential was considered to be lower than the home with a sump (Montgomery Watson 1995c). Chloroform and cis-1,2-DCE were found in these homes at a maximum of 0.08 ppb and 0.29 ppb. 1,1,1-TCA (up to 0.89 ppb) and TCE (up to 0.4 ppb) were detected in indoor air at South Weber Drive and South 850 East.
Indoor Air Exposure in South Weber
South Weber has a little more than 1,100 homes. A majority of the groundwater contamination is on the hillside where no homes are situated. It appears that less than 100 homes are above the groundwater contamination from Hill AFB. Therefore we believe a majority of the homes in South Weber have no potential for exposure to indoor air contamination resulting from Hill AFB.
Remedial actions instituted by the USAF in the area of the groundwater plumes affecting South Weber were initiated at the same time the first sampling was performed and completed several years after the 1994-1995 indoor air sampling. The concentrations of VOCs detected in the earlier sampling are higher than the levels found in either 1993 or 1994-1995. Considering this, the earlier sampling round represents a worst-case situation for residents of these communities. Indoor air concentrations in South Weber are decreasing. ATSDR has no reason to believe that this decrease will not continue.
Highest Concentrations Detected
Chloroform and cis-1,2-DCE were found in these homes at a maximum of 0.23 ppb and 0.29 ppb. 1,1,1-TCA (up to 0.89 ppb) and TCE (up to 0.4 ppb) were detected in indoor air at South Weber Drive and South 850 East. Although both of these VOCs were detected in groundwater, the concentrations are higher in air than one would expect if they had volatilized from groundwater, indicating that there may be an unknown source of these compounds in the home (Montgomery Watson 1995a). Additional air contamination found in the home can be related to gasoline and vapor emissions that are widespread in the atmosphere or found in fumigants, solvents, paints, etc. Both TCA and TCE were detected at concentrations below those commonly detected. There is no commonly detected level of cis-1,2-DCE for comparison purposes.
Exposure Evaluation
ATSDR conservatively assumed that an adult was exposed to the highest detected concentration of indoor air contaminants constantly for 24 hours a day, 365 days per year. These assumptions create a very conservative estimate of exposure, most likely higher than an exposure dose for an average individual in the community.
TCE and chloroform were the only suspected carcinogens detected in indoor air in South Weber. The estimated excess lifetime cancer risk for TCE and chloroform are below levels likely to cause adverse health effects. Adverse health effects should not result from exposure to these levels of contamination in homes in South Weber.
The maximum exposure dose for TCA found in indoor air in homes in South Weber in 1990 was more than 100,000 times lower than its EPA reference dose (Table 15). Adverse health effects should not result from exposure to this level of contamination in homes. Because the detection limit was so high in this sampling round and the samples were collected on only one day, additional sampling was performed in 1993. For a more detailed analysis, please see Table 25.
The maximum exposure dose for TCA found in indoor air in South Weber in 1993 was more than five times lower than its EPA reference doses (Table 15). Using this information, ATSDR concluded that the maximum value of VOCs detected in homes in the South Weber area is much lower than the level known to cause adverse health effects.
The maximum exposure dose for TCA found in indoor air in South Weber in 1994-1995 was ten times lower than its EPA reference doses (Table 15). Therefore, adverse health effects should not result from exposure to this level of TCA in homes. The risk based concentration (RBC) for cis-1,2-DCE is more than 30 times higher than its maximum detected concentration. ATSDR concluded that the maximum value of VOCs detected in homes in the South Weber area is much lower than the level at which adverse health effects are detected.
Table 15. South Weber Housing Area In-Home Indoor Air Measurements (1990, 1993, and 1994-1995)
| Compound | Maximum Concentration (ppb) | Common National (ppb) | Risk (unitless)/Dose (mg/kg/day) | Comparison Value (units) |
Source |
| 1990 | |||||
| Noncarcinogen | |||||
| TCA | 0.004 | 48.9 | 0.624E-05 | 6300E-05 mg/kg/day | EPA Reference Dose |
| 1993 | |||||
| Carcinogens | |||||
| TCE | 0.74 | 1.3 | 2.92E-06 | - | - |
| Chloroform | 0.23 | 8.4 | 1.11E-05 | - | - |
| Noncarcinogen | |||||
| TCA | 18 | 48.9 | 0.0281 | 0.063 mg/kg/day | EPA Reference Dose |
| 1994-1995 | |||||
| Carcinogens | |||||
| TCE | 0.4 | 1.3 | 1.58E-06 | - | - |
| Chloroform | 0.08 | 8.4 | 3.87E-06 | - | - |
| Noncarcinogens | |||||
| TCA | 0.89 | 48.9 | 0.0014 | 0.063 mg/kg/day | EPA Reference Dose |
| Cis-1,2-DCA | 0.29 | N/A | - | 9.33 ppb | EPA RBC |
Indoor Air Modeling for South Weber-Past Exposures
It was unclear whether the indoor air sampling was conducted when the groundwater contamination under the homes was at its worst. ATSDR used the Johnson and Ettinger model to estimate whether intrusion of the highest levels would have presented a health hazard. TCE and PCE were the most predominant compounds in the groundwater plumes beneath South Weber. The maximum groundwater concentration of TCE, 6,300 ppb, was entered in the model. The model projected an indoor air concentration of 410 ppb, which was more than 100 times lower than the LOAEL (ATSDR 1997b). Once again, it was concluded that none of the groundwater contaminants off-gassing into indoor air were at levels that could contribute to adverse health effects.
Surface Water Exposures in South Weber
Surface water in South Weber includes springs and seeps on the hillside, as well as the Davis-Weber Canal and the Bambrough Canal, two constructed irrigation canals. The Davis-Weber canal is lined with concrete and contained from groundwater contamination. Surface water samples were collected in 1990-1992 from springs and seeps on the hillside that adjoins the Davis-Weber Canal and South Weber to evaluate off-base contamination migration and to assess whether this contamination was affecting surface water in South Weber. Sampling performed as part of Operable Unit (OU) 1, 2 and 4 investigations found no contamination in the portion of the Davis-Weber Canal that runs through South Weber.
Surface water samples from the Bambrough Canal were also tested. Low levels of ethylbenzene, toluene, xylenes, semivolatile organic compounds (SVOCs) and pesticides were found in this irrigation canal. DCE was found in seeps on the hillside downgradient of the eastern portion of OU 1, on the boundary northeast of Landfill 4, on the downgradient of the central portion of OU 1, on the hillside downgradient of the western portion of OU 1, and in the Weber River Valley downgradient of the western portion of OU 1. The maximum concentration of DCE (530 ppb) was detected in the hillside downgradient of the western portion of OU 1. Arsenic was found in seeps on the hillside downgradient of the eastern portion of OU 1, on the boundary northeast of Landfill 4, on the downgradient of the central portion of OU 1, and on the hillside downgradient of the western portion of OU 1. The maximum concentration of arsenic detected (1,160 ppb) was near the base boundary northeast of Landfill 4. No additional contamination was found in surface water in South Weber (HAFB 1994, 1996b,1998b).
People come into contact with surface water in South Weber in two ways: through accidental ingestion of water from springs and through dermal contact of the surface water in the springs. Exposure doses were calculated for each of these chemicals for both accidental ingestion and dermal contact.
Dermal Contact
The maximum dermal exposure doses for DCE and arsenic are fifteen times lower than their EPA adjusted reference doses (Table 16). Adverse health effects should not result from exposure to this level of contamination in surface water in South Weber.
Table 16. South Weber Surface Water Measurements-Dermal (1990 - 1992)
| Compound | Maximum Concentration (ppm) | Dose (mg/kg/day) | Comparison Value (mg/kg/day) | Source |
| DCE | 0.530 | 0.0002 | 0.003 | Adjusted EPA Reference Dose |
| Arsenic | 1.160 | 0.000022 | 0.140 | Adjusted EPA Reference Dose |
Ingestion of Surface Water
The maximum exposure doses for water ingestion for DCE and arsenic were more than eighty times lower than their EPA reference doses (Table 17). ATSDR concludes that adverse health effects are not expected for humans exposed to these levels of DCE and arsenic through accidental ingestion of contaminated surface water in South Weber.
Table 17. South Weber Surface Water Measurements-Ingestion (1990 - 1992)
| Compound | Maximum Concentration (ppb) | Dose (mg/kg/day) | Comparison Value (mg/kg/day) | Source |
| DCE | 530 | 0.0017 | 0.009 | EPA Oral Reference Dose |
| Arsenic | 1,160 | 0.008 | 0.014 | EPA Oral Reference Dose |
ATSDR CHILD HEALTH CONSIDERATIONS
ATSDR recognizes that infants and children may be more sensitive to environmental exposure than adults in communities faced with contamination of their water, soil, air, or food. This sensitivity is a result of three factors. First, children are more likely to be exposed to certain media (e.g., soil or surface water) because they play outdoors. Second, children are shorter than adults, which means that they can breathe dust, soil, and vapors close to the ground. Third, children are smaller; therefore, childhood exposure results in higher doses of chemical exposure per body weight. Children can sustain permanent damage if these factors lead to toxic exposure during critical growth stages. ATSDR is committed to evaluating children's sensitivities at areas such as Hill AFB as part of its Child Health Initiative.
ATSDR has attempted to identify (a) populations of children at and in the vicinity of Hill AFB and (b) any public health hazards threatening these children. Approximately 1,700 dependents live in on-base housing. Two larger day care centers (with after school programs) and 50 smaller private day care facilities are in the area of Hill AFB. Together, these facilities serve approximately 500 children.
ATSDR determined that exposure of children to the highest levels of contaminants is unlikely because children who live at the base do not typically access IRP areas or locations of contamination at Hill AFB. However, ATSDR also considered the presence of children in unrestricted areas near schools, day cares, and housing areas where they might contact contaminants leaving the area, and exposure to children in homes above the groundwater plumes. These potential exposure pathways are discussed in the Environmental Contamination and Human Exposure Pathways section of this PHA. Based on our evaluation, ATSDR identified no situations in which children are likely to be exposed to harmful levels of contaminants associated with Hill AFB.
Each of the exposure calculations discussed in the text were also performed for children. ATSDR concluded that no adverse health effects are expected to occur in children who are exposed to the level of contamination present at Hill AFB and in the surrounding communities.
Through the PHA process, ATSDR has gathered information about health concerns voiced by members of the community. In gathering this information, ATSDR interviewed base public affairs personnel who address community questions and concerns about Hill AFB, met with other base personnel (including the support group commander, civil engineers, the judge advocate, and the commander of public health) who also meet with the public, and reviewed the results of the base's survey of community concerns.
Hill AFB has a community relations plan (CRP) that provides guidance for involving the community and other interested parties in the remediation decision-making process and for distributing information to these parties (HAFB 1997b). As part of its community relations activities, Hill AFB formed a restoration advisory board (RAB). The RAB, which is represented largely by local community members, meets to periodically review base documents and comment on actions and proposed actions taken by Hill AFB.
In evaluating available data from Hill AFB, ATSDR has not found exposures posing a public health hazard. Some residents, including adults and children, at Hill AFB and the surrounding communities could be exposed to contaminants via indoor air, surface water dermal contact, and consumption of surface water and locally-grown crops. Based on the currently available scientific literature, and the community specific data available for review, the level of exposure from each of these situations individually and combined are at very low levels and would not be expected to present adverse health effects in people living in these areas.
ATSDR uses human epidemiologic and occupational studies and also animal studies when evaluating the likelihood of cancerous effects or cancer risk. Using cancer risk estimates, ATSDR determined that cancerous health effects are unlikely in people who were exposed to VOCs at Hill AFB and in the surrounding communities. A few epidemiologic studies have suggested that exposure to VOCs at levels 50 to 100 times greater than the levels found in homes at Hill AFB and in the surrounding communities may be associated with leukemia, non-Hodgkins lymphoma, and bladder and kidney cancer. The exposure doses in these studies were higher than what was estimated here. Tables 20-24 present exposure and cancer risk estimates.
Most of the VOC detected in groundwater and indoor air are common in homes across the country. Automobiles, household paint, and cleaning products are the usual sources of VOCs in indoor air. During our review of the indoor air sampling, no contaminants were detected at levels likely to cause cancerous or noncancerous adverse health effects.
To help investigate community concerns, the Davis County Health Department that monitors cancer incidence in Davis County in conjunction with the University of Utah Public Health Program, performed a study from January 2001 to January 2002 that investigated the occurrence of brain cancer in Davis County. The study was in response to citizen concerns about dioxin-containing soil surrounding the Wasatch Energy Systems (WES) Energy Recovery Facility (i.e., "Burn Plant") and fumes emanating from this plant and their association with the development of brain cancer. The Energy Recovery Facility is in Layton, Utah, and is adjacent to the southeastern corner of Hill AFB. More than 200,000 tons of garbage is delivered to WES every year. WES helps reduce landfill waste by recycling, composting, and combusting waste.
As part of the combustion process at the Energy Recovery Facility, garbage is burned in a controlled environment with special air cleaning equipment that catches ash and impurities. Combustion reduces the bulk of municipal waste and provides energy production. Combustion also produces small amounts of dioxin, which may be released into the air. Airborne dioxin settles into the surrounding soil and even smaller amounts may be carried by the wind and air currents to communities surrounding the Energy Recovery Facility. People in the community were concerned about the number of brain cancer cases, possibly due to the dioxin releases, from WES. However, investigations of soil and air by the Utah Division of Air Quality have determined that dioxin emissions from WES do not pose a threat to public health (Wasatch Energy Systems 2002)
Researchers examined whether there was an increase in cancer cases in Davis County compared to the rest of the state. The study recorded a rise in brain-cancer rates over a three-year period, but found no link to the increase with any environmental causes (Khashan 2002a). The Davis County Health Department concluded that while there was an increase in brain cancer rates in these areas from 1997 to 1999, the rise was attributable to a random variation. Upon receiving year 2000 census data that showed cancer rates in that same area matched state averages, the study's sponsors determined that there was no evidence that brain cancer rate increases for the three years prior were related to environmental causes. All other cancers examined were found to be consistent with statewide averages (Khashan 2002b). The health department plans to continue cancer surveillance in the area (ATSDR 2002f).
People with concerns about cancer rates in the area surrounding the Hill AFB should contact the Davis County Health Department at 801-451-3340.
Recent media attention has been focused on unexploded ordnance (UXO) at the Utah Test and Training Range (UTTR). UTTR is 30 - 60 miles west of Hill AFB, on the west side of the Great Salt Lake. The UXO areas are not on or near Hill AFB proper. The areas in question are outside the current range boundary and fall under the Corps of Engineers Formerly Used Defense Sites (FUDS) program. UTTR is highly restricted. As such, no access by individuals without authorization is expected. Residents of Hill AFB and those who live in one of the communities surrounding Hill AFB are not expected to encounter UXO.
PUBLIC COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD
CONCERN ABOUT QUANTITY OF DATA
Although ATSDR stated throughout the text that its main focus was on indoor air, the primary emphasis in the Hill AFB studies was directed (especially off-base) on potential exposure to polluted groundwater with almost no indoor sampling in some cities. Therefore, how did ATSDR reach its conclusions about indoor air from such a thin data set?
We believe the quantity of data augmented with modeling data and data from other sites provided a sufficient database to evaluate the possible hazards posed by indoor air migration. ATSDR used the direct evidence of the indoor air samples and mathematical computer models to check indoor air levels and to predict indoor levels at areas where no air sampling has occurred. We also used information from other military bases where groundwater contamination migrated into the indoor air spaces of homes in other parts of the country. These various data sets along with information about the source of the contamination, groundwater movement, and length of time of contaminant release allowed ATSDR to predict what the levels were in the past and whether levels were likely to increase or decrease in the future. In this way, ATSDR could evaluate whether people were likely to have gotten sick in the past from their exposure, whether they are now likely to be sick, and whether they are likely to sick in the future from contaminants that have come from Hill AFB.
From our evaluation, we have concluded that the levels present or likely to be present in indoor air are much lower than levels of the same chemicals that have been shown to cause cancer or non-cancerous health effects.
CONCERN THAT INFORMATION ON PROXIMITY TO WASTE SITES SHOWS HEALTH RISKS
The commenter quoted the following information.
The California Birth Defect Monitoring Program (Croen et al 1997), determined that women who lived within ¼ mile of a Superfund site during the first 3 months of pregnancy had a greater risk of having babies with certain birth defects such as heart defects and neural tube defects.
In another set of studies looking at biogas from landfills in Quebec (Goldberg et al 1995a and 1995b), compounds such as tetrachloroethane, chloroform, and benzene that are included in biogases are embryo- or fetotoxic. Excess risks were found for stomach cancer and cancer of the cervix uteri for women living closer to the site. The risk of low birth weight was found in those living nearest to the site.
In a study of the Lipari Landfill in New Jersey where cleaning solvents, phenols, metals, bis (2-chloroethyl) ether and other compounds were disposed, Berry and Bove (1997) concluded that the population living immediately adjacent to the site was significantly impacted regarding birth weight.
Miller and McGeehin (1992) analyzed health questionnaires from residents living within 4 miles of two NPL sites near Houston, Texas. They found increases in a number of afflictions. Theses included eczema and other skin problems, ulcers or other non-cancer stomach diseases, hay fever or other non-asthma respiratory allergies.
A 1998 Report on Air Carcinogens published by EPA noted that many chemical may have health effects such as reproductive and developmental effects for which the agency has established no benchmark standards.
Swartz and Clapp (1992) reported that epidemiologic studies have found significantly elevated cancer rates among the general population at levels hundreds of times lower than work-place levels. They stated that there are no thresholds for cancer-causing agents and that exposure to low doses of these substances produces some increased risk of developing cancer.
Other studies by Peterson et al (1979) and Swartz et al (1982) learned that vinyl chloride can induce tumors over a range of five order of magnitude and that at the lowest dose, the cancer potency is 30 time that at the highest dose.
The studies mentioned above make no determination of whether the people have contact with any chemicals. ATSDR used studies about actual chemical exposures to make conclusions as to whether the people living in the areas surrounding Hill AFB are likely to get sick from exposure to chemicals that have come from the base. We believe using direct studies conducted of people and animals exposed to the actual chemicals at the relevant exposure levels as is present in the communities is more appropriate. The studies mentioned above are statistical reviews of two separate parameters 1) people living near a hazardous waste sites and 2) illness; they are indirect and coincidental occurrences which may or may not be related.
Conclusions regarding potential past, current, and future exposure situations on and in the communities near Hill AFB are based on a thorough evaluation of base investigation data and observations made during base visits. Conclusions about exposures are described below. (A description of the public health hazard conclusion categories is included in the glossary.)
Although exposure occurred in all of the above situations, the levels are too low to present a public health hazard.
The Public Health Action Plan (PHAP) for Hill AFB contains descriptions of actions taken and those to be taken by ATSDR, the USAF, EPA, and Utah Department of Environmental Quality Engineering at and in the vicinity of the base after the completion of this public health assessment. The purpose of the PHAP is to ensure that this public health assessment not only identifies public health hazards, but also provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment.
Hill AFB has an active environmental program that has developed and implemented innovative ways to reduce the groundwater contamination, and in turn, the indoor air contamination. The USAF's remedial efforts have focused on preventing the continued migration of contaminated groundwater into the communities surrounding the base. Some of their remedial efforts include constructing a hydraulic containment system. From fall 1997 through spring 1998, the USAF constructed a hydraulic containment system consisting of a series of eight vertical groundwater extraction wells. The system induces a hydraulic gradient that contains contaminated groundwater at the southern boundary of Hill AFB. The USAF installed a source recovery system in 1993 to remove dense non-aqueous phase liquid (DNAPL) from the eastern boundary of the base (near South Weber). Landfill 1, on the northeastern boundary of the base was covered with asphalt in May 1996.
Groundwater extraction trenches were installed at several locations on the base in order to limit contaminant migration from an area near South Weber. The USAF covered the Sodium Hydroxide Tank Site and Berman Pond with asphalt caps in the late 1990s. Hybrid poplar trees were planted in August 2001 in an effort to control the plume affecting Riverdale and South Weber.
Ongoing/Planned Actions
Recommended Actions
Carole Hossom
Environmental Health Scientist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry
Atlanta, GA
Diane Jackson
Environmental Engineer
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry
Atlanta, GA
Contributor:
Elizabeth C. Mitchell, MSPH
Environmental Health Scientist
Eastern Research Group, Inc.
Atlanta, GA
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Agency for Toxic Substances and Disease Registry (ATSDR) 1994a. Health Consultation for Hill Air Force Base OU6, Ogden, Utah. July 27.
Agency for Toxic Substances and Disease Registry (ATSDR) 1994b. Toxicological profile for 1,1-Dichloroethene. May.
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Agency for Toxic Substances and Disease Registry (ATSDR) 2002a. Record of Communication, electronic correspondence with Colleen Lovett, Air Force Materiel Command, September 12.
Agency for Toxic Substances and Disease Registry (ATSDR) 2002b. Record of Communication, electronic correspondence with Cary Fisher, Hill Air Force Base Environmental Management Directorate, April 24.
Agency for Toxic Substances and Disease Registry (ATSDR) 2002c. Record of Communication, electronic correspondence with Kyle Gorder, Hill Air Force Base Environmental Management Directorate, April 15.
Agency for Toxic Substances and Disease Registry (ATSDR) 2002d. Record of Communication, electronic correspondence with Kyle Gorder, Hill Air Force Base Environmental Management Directorate, April 17.
Agency for Toxic Substances and Disease Registry (ATSDR) 2002e. Record of Communication, electronic correspondence with Kyle Gorder, Hill Air Force Base Environmental Management Directorate, April 1.
Agency for Toxic Substances and Disease Registry (ATSDR) 2002f. Record of Communication, telephone discussion with Wendy Kelly, Davis County Health Department, April 10.
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