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PUBLIC HEALTH ASSESSMENT

MOUNTAIN HOME AIR FORCE BASE
MOUNTAIN HOME, ELMORE COUNTY, IDAHO


TABLES

Table 1.

Potential Exposure Pathways
Pathway Name Source of Contamination Environmental Medium Point of Exposure Route of Exposure Time of Exposure Exposed Population Comments
Completed Exposure Pathways
Drinking Water (Base Production Wells) Light industrial activities at Mountain Home AFB; drinking water chlorination process. Groundwater Drinking water wells Ingestion
Inhalation
Dermal
Past/Current/Future
  • Trihalomethanes (bromoform, bromodichloromethane, and chlorodibromomethane) and trichloroethylene have been detected above the CREG but below MCLs in drinking water wells.
  • Residents and employees of Mountain Home AFB; visitors Contaminants are not detected at levels that are likely to pose a health hazard under past, current, and future exposure situations, as indicated by conservative exposure dose estimates (Appendix C).
    Potential Exposure Pathways
    Soil Light industrial activities at Mountain Home AFB Soil Various IRP sites Ingestion
    Dermal
    Past/Current/Future
  • Contamination exists sporadically and at low levels at some industrial sites.
  • Residents and employees of Mountain Home AFB, trespassers Contaminants are not detected at levels that are likely to pose a health hazard under past, current, and future exposure situations.
    Drinking Water (Off-base Private Wells) Light industrial activities at Mountain Home AFB Groundwater Drinking water wells Ingestion
    Inhalation
    Dermal
    Past/Current/Future
  • No contaminants have been detected above ATSDR comparison values in private drinking water wells.
  • Users of private wells in the Mountain Home AFB area Contaminants are not detected at levels that are likely to pose a health hazard under past, current, and future exposure situations.
    Surface Water Light industrial activities at Mountain Home AFB Surface Water IRP sites SD-25 and LF-1 Dermal Past/Current/Future
  • Contaminants exist sporadically and at low levels at SD-25 and LF-1.
  • Residents and employees of Mountain Home AFB, trespassers Contaminants are not detected at levels that are likely to pose a health hazard under past, current, and future exposure situations.



    Table 2.

    Evaluation of Potential Public Health Hazards Associated With the Installation Restoration Program Sites at Mountain Home Air Force Base
    Mountain Home AFB Sites Site Description/
    Waste Disposal History
    Investigation Results/Environmental Monitoring Results1 Corrective Activities and Current Status ATSDR's Evaluation of Public Health Hazards
    Lagoon Landfill
    (LF-1)
    A former landfill (1952 -1956) which now contains a wastewater lagoon system. The landfill was the main sanitary landfill for the base and received general household refuse and approximately 6 barrels of liquid waste (possibly mineral or engine oil, hydraulic fluids or solvents [TCE and carbon tetrachloride]) per month. In 1961, the lagoon system, consisting of 4 unlined wastewater cells, was constructed on top of the four (three east-west and one north-south) trenches which served as the landfill. The current daily flow of wastewater to the lagoons is between 600,000 and 800,000 gallons. Oil/water separators collect waste oils and lubricants from industrial discharges prior to discharging to the lagoons, however, collection may be incomplete, resulting in some discharge to the lagoons. Wastewater Lagoons: Area 1
    Cadmium, copper, mercury, silver, and vanadium were detected above background levels but below ATSDR comparison values.
    Sediment
    Metals: Lead (47.5 ppm).
    PAHs: TRPH (4,140 ppm).
    Pesticides: 4,4-DDT (35 ppm).
    Wastewater Lagoons: Area 2
    Cadmium, copper, chromium, mercury, silver, and vanadium were detected above background levels but below ATSDR comparison
    values.
    Sediment
    Metals: Lead (35.2 ppm).
    PAHs: TRPH (2,760.5 ppm).
    Lagoon Landfill Soil (depth of 35 feet)
    Metals: Arsenic (0.96 ppm, M), beryllium (0.49 ppm, M), lead (5.3 ppm, M).
    Lagoon Landfill Groundwater
    Metals and trichloroethylene (TCE) were detected below ATSDR comparison values.
    Surface Water
    VOCs: Benzene (0.004 ppm).
    SVOCs: bis(2-Ethylhexyl)phthalate (0.025 ppm).
    Current Status:
    • No further remedial action required.
    Soil/Sediment: No public health hazard is associated with the soil at this site. Contaminants detected in sediment and soil are not accessible.
    Surface water: No public health hazard is associated with the surface water at this site. Because public access to this site is limited, the area is industrial and the site is some distance from residential areas, exposure to surface water is unlikely.
    B Street Landfill
    (LF-2)
    LF-2 was the main sanitary landfill for the base between 1956 and 1959. LF-2 consists of a rubble area, a drum disposal site, the ash disposal area (5 trenches), and a burn site. Materials disposed of at LF-2 include petroleum waste/solvents, pesticides, and asbestos. The ash disposal area of the landfill was capped in March 1995. Drum Disposal Area
    Barium, copper, chromium, mercury, and zinc were detected above background levels but below ATSDR comparison values.
    Surface Soil (0.5 - 1 foot)
    Metals: Arsenic (42.7 ppm, M), beryllium (1.9 ppm, M), lead (133 J ppm, M).
    PAHs: Benzo(a)pyrene(0.730J ppm, M), benzo(b)fluoranthene (1.1J ppm, M), benzo(g,h,i)perylene (0.045, M ppm), phenanthrene (0.34 ppm, M), TRPH (1,120 ppm, M).
    Trench Area
    Cadmium and zinc were detected above background levels but below ATSDR comparison values.
    Surface Soil (1 foot)
    Metals: Arsenic (12.1 ppm, M), beryllium (0.68 ppm, M), lead (79 ppm, M.
    PAHs: Benzo(a)pyrene (0.130 ppm, M), benzo(g,h,i)perylene (0.073 ppm, M), phenanthrene (0.120, M), TRPH (155 ppm, M).
    Pesticides: 2,4-D (45 ppm, M)
    PCBs: Arochlor-1260 (0.034ppm, M).
    Current Status
    •No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. Exposure to the surface soil is unlikely and would be infrequent if it occurred; therefore, contaminated concentrations are not associated with health hazards.
    Existing Landfill (LF-3) LF-3 has been the principal sanitary solid landfill since 1969. Empty drums were disposed in a metals trench and petroleum wastes were possibly disposed. Asbestos is disposed in one of the open pits. Site operation procedures and records do not indicate that hazardous wastes have been disposed at this site. No sampling was conducted at this site and the site was not considered for soil or groundwater exposure pathways. No air or soil monitoring for asbestos has been conducted. Current Status:
    •No further remedial action required.
    Soil: No public health hazard is associated with this site. If proper compacting procedures are followed, no asbestos or other materials should be disturbed or released to the environment. LF-3 is not likely to be associated with any public health hazards.
    Fire Department Training Area
    (FT-4)
    FT-4 is a burn pit (60 X 140 ft) which was used in 1943 and 1944 for training exercises. Chemicals used in the training exercises included aviation fuels, solvents, waste oils, and petroleum lubricants. Soil
    Soil gas surveys indicate that volatile organic compounds (VOC) and benzene, toluene, ethylbenzene, and xylene (BTEX) levels are below ATSDR comparison values.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Fire Department Training Area
    (FT-5)
    FT-5 was used between 1944 and 1945. Chemicals used in training exercises included aviation fuel and petroleum, oil, and lubricant wastes (POL). FT-5 is currently located under supply warehouse building 1325. Soil
    Soil gas surveys indicate that VOC and BTEX levels are below ATSDR comparison values.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Fire Department Training Area
    (FT-6)
    FT-6 is a circular area (310 ft diameter) which was used for fire extinguishing training between 1948 and 1953. Chemicals used in training exercises included aviation fuel and POL. Soil
    One subsurface (3 ft) soil gas VOC sample was found to have a concentration higher than background levels (TVOC = 27 ppb). The other 31 sampling sites were below ATSDR comparison values.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Fire Department Training Area
    (FT-7)
    FT-7 is comprised of three areas, 7A, 7B, and 7C, which were used between 1953 and 1962. Chemicals used in training exercises included aviation fuel and POL. FT-7 is located in an open, non-irrigated field which requires minimal maintenance. The field is located near an abandoned runway. Soil (Depth unspecified)
    FT-7A - Soil gas surveys indicated that VOC and BTEX levels are below ATSDR comparison values.
    FT-7B - Elevated soil gas concentrations led to subsequent soil sampling.
    Metals: Arsenic (14.7 ppm), lead (24.5 ppm).
    PAHs: 2-Methylnaphthalene (20 ppm), TRPH (8,720 ppm).
    FT-7C -Elevated soil gas concentrations led to subsequent soil sampling. Soil sampled for VOCs, semi-volatile organic compounds (SVOC), TRPH, and metals. Several VOCs (fuels and solvent constituents) were detected below ATSDR comparison values.
    Current Status:
    • No further remedial action required at the three sites.
    Soil: No public health hazard is associated with the soil at this site. Public access is believed to be limited due to the site's proximity to the flight line and distance from the residential area. Exposure is, therefore, unlikely.
    Fire Department Training Area
    (FT-8)
    FT-8 is a burn area which was used between 1962 and 1986. FT-8 is a secure site surrounded by a chain link fence topped with barbed wire with three locked gates. Access is limited. The structures at the site include: a three story building, a single story shed, a burn area (125 ft in diameter) with an airplane shell surrounded by a 1 ft high berm, a fire hydrant, and an underground storage tank (15,000 gallons). Fire training exercises were conducted 2-3 times a month on a seasonal basis. Fuels used for the training exercises were waste petroleum, oils, lubricants, and jet fuel (JP-4). Fire extinguishing agents used were: Aqueous Film Forming Foam (a water-based mixture of (60:30) diethylene glycol monobutyl ether and 10% surfactants/stabilizers), and a water-based protein foam. Soil (0 to 1.5 feet deep)
    PAHs: TRPH (14,000 ppm).
    SVOCs: 2-Hexanone, 4-methyl-2-pentanone (49 ppm).
    Current Status:
    Site was remediated and an underground storage tank was removed. A non-porous berm was placed under the burn area.
    Soil: No public health hazard is associated with this site. Access is restricted.
    Waste Oil Disposal Site (DP-9) DP-9 was used for waste oil/liquid disposal between 1953 and 1956. DP-9 is located between the taxiway and the runway approach. Soil samples analyzed for metals and other contaminants (VOCs, SVOCs, pesticides, and PAHs).
    Soil (Depth Unspecified)
    Metals: Arsenic (4.8J ppm)
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The site is not easily accessible and; therefore, exposure is unlikely and infrequent if it does occur.
    Perimeter Road Site (OT-10) OT-10 was used for waste oil/degreasing solvent disposal from the flight line, motor pool, and auto hobby shop. Disposal may have started in 1943 and continued until 1975. Waste oil was placed on the perimeter road for dust control. The road was paved with crushed asphalt after 1987 and is currently an active roadway. Soil samples were analyzed for VOCs, SVOCs, TRPH, and metals. VOCs (1,1-dichloroethane and 1,2-dichloroethane) and SVOCs (4-nitrophenol and di-n-octylphthalate) were detected in subsurface soils. Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The contaminants are located in the subsurface soil and are, therefore, not accessible to the public.
    Flight Line Fuel Spill (ST-11) The fueling system was installed in the mid-1950s. Leaks occurred soon after it was installed and continue. It is estimated that as much as 50,000 gallons of jet fuel may have been released. ST-11 is located underneath an aircraft parking lot and is almost entirely covered by pavement. Soil gas, soil borings, and rock cores indicate that contamination did not affect bedrock at or below a depth of 170 ft.
    Surface Soil (0-0.5 feet)
    Pesticides: Lindane (0.00005 ppm, M).
    Soil (Depth Unspecified)
    Cadmium was detected above the background levels but below ATSDR comparison values.
    Metals: Arsenic (4.86 ppm), beryllium (0.29 ppm), lead (91.43 ppm).
    VOCs: Dibromochloromethane (9.3 ppm), tetrachloroethylene (11.8 ppm), trichloroethylene (106 ppm).
    SVOCs: Benzo(a)pyrene (0.480 ppm), benzo(g,h,i)perylene (0.230 ppm), phenanthrene (0.280J ppm).
    Perched Water (groundwater)
    Benzene (7.5 ppm)
    Current Status:
    • Long-term monitoring is required at this site.
    • Property records were amended to impose deed restrictions and include contamination issues. Site conditions will be re-evaluated if a change in land use is proposed in the future.
    Soil: No public health hazard is associated with the soil at this site. Most of the soil is covered with concrete, so exposure is unlikely and would be infrequent if it occurs.
    Perched water (groundwater): No public health hazard is associated with the groundwater at this site. Contamination is no longer migrating. Modeling shows that the chemicals of concern will not reach the groundwater in concentrations that would exceed ATSDR comparison values. The perched water is not used as a drinking water source.
    Entomology Shop Yard (SD-12) SD-12 was used to store/handle herbicides, pesticides, and application equipment from 1969 to 1987. Wastewater generated by cleaning the application equipment was discharged to the surrounding surface soils through a cement ditch and later a buried drainpipe. In 1981, an underground storage tank was installed to collect the wastewater. Surface Soil (1 foot)
    Metals: Arsenic (5.6 ppm, M), lead (32.7 ppm, M).
    Pesticides: Aldrin (0.120 ppm, M), alpha-Chlordane (1.300 ppm, M),
    4,4'-DDT (2.7 ppm, M), Dieldrin (2.900 ppm, M), Heptachlor (0.280 ppm, M), MCPP (75 ppm, M).
    Corrective Activities:
    The entomology shop was demolished and the underground storage tank was removed in 1987. The site is currently covered with asphalt and is used as a parking lot.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The contaminants are not accessible as they are located under an asphalt cover. Past exposures would have been limited as this was an industrial site.
    Petroleum, Oil, and Lubricants; Gasoline Tank Site (Four Underground Storage Tanks) (ST-13) Four storage tanks were present at ST-13 until 1988. The tanks ranged in capacity from 12,000 - 15,000 gallons and were used for temporary storage of petroleum, oil, and lubricant wastes prior to removal from the site. No pre- or post-tank removal data were available for review. Corrective Actions:
    The tanks were removed in June 1988. The site was backfilled with clean soil and covered with a clay cap.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. No current or future exposures because the contaminated soil as been removed and the site has been capped.
    Groundwater: No public health hazard is associated with the ground water at this site. There was no evidence of contamination below 30 ft from the surface. Chemicals of concern will not reach the groundwater in concentrations that would exceed state or federal standards.
    Radioactive Material Burial Site (RW-14) A 55-gallon drum of radioactive waste and associated materials (radium-coated aircraft instrument faces, radioactive metabolic tracer material, and x-ray equipment components) were buried at
    RW-14 in the mid-1950s.
    Radioactive contaminants were not detected in the surrounding soil. Corrective Actions:
    The radioactive materials were removed and disposed of as low-level radioactive waste.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Corker Material Burial Site
    (OT-15)
    Corker material (boron fibre composite) from an aircraft crash was bagged and buried at this site in July 1979. Boron was not detected in soil samples. Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Munitions Disposal Area (OT-16) OT-16 was built between 1950 and 1957 and was in operation until 1980 to dispose of explosives. The explosives were placed in a furnace/burn pit, doused with fuel, and ignited to cause detonation. Soil samples in the burn pit were found to contain explosive compounds, low levels of VOCs, and some relatively high concentrations of PAHs. Explosive compounds were not detected in the soil where the furnace was located.
    Soil (Depth Unspecified)
    Metals: Lead (23.33 ppm).
    PAHs: Benzo(a)anthracene (2.122 ppm), benzo(a)pyrene (2.1 ppm), benzo(b)fluoranthene (2.308 ppm),TRPH (653.23 ppm).
    Corrective Activities:
    • The burn pit was cleaned out and backfilled with new fill. The furnace was dismantled in 1992.
    • No further remedial action required
    Soil: No public health hazard is associated with the soil at this site. Exposure is unlikely and contaminants were detected at levels below health-based guidelines.
    Groundwater: No public health hazard is associated with the groundwater at this site. Chemicals of concern in the soil will not reach the groundwater in concentrations which would exceed state or federal standards.
    Old Burial Trench
    (DP-18)
    DP-18 was excavated in 1953 (800 ft x 10 ft) and was filled with excess supplies generated by WWII such as outdated ammunition, wrecked jeeps, and canned food. Test pits (12 ft deep) did not show evidence of waste materials.
    Soil (Depth Unspecified)
    Metals: Arsenic (18.8 ppm).
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Titan Missile Maintenance Area (ST-22) ST-22 consists of four underground storage tanks used to store solvents, acids, and caustic solutions. Organic residues (1,2-dichloroethane, methylene chloride [possible laboratory contaminant] and acetone - [possible laboratory contaminant]) were detected below ATSDR comparison values. Current Status:
    • No further remedial action required.
    Corrective Activities: The underground storage tanks were abandoned, filled with sand, and sealed.
    Soil: No public health hazard is associated with the soil at this site.
    Solid Waste Disposal Area (LF-23) LF-23 consists of three burial trenches which contain tires and household and solid waste. The site is in an open, non-irrigated field which receives minimal maintenance. Soil samples from test pits (10-16 ft) were analyzed for VOCs, SVOCs, and metals. Metals, SVOCs, and PAHs were detected slightly above ATSDR comparison values in the subsurface soil (~15 feet). Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The contaminants detected in the subsurface soil are not accessible to the public.
    Auto Hobby Shop/ Munitions Trailer
    (SD-24)
    SD-24 was built in 1960 for use as a liquid oxygen production and helium loading plant. In 1965, it was converted to an auto hobby shop. Waste oil was normally removed from the site via discharge drain lines from the oil sump. Between 1965 and 1974, some waste oil was dumped on the surface soils on the southwest side of the building. A munitions maintenance shop has occupied the site since 1982. The site is fenced. Varying concentrations of contaminants were found in the soils around the waste collection tank and the oil sump. Several VOCs were detected in sediments below ATSDR comparison values.
    Surface Soil (up to 1 foot)
    Metals: Arsenic (3.9 ppm, M), beryllium (1.2 ppm, M), lead 522 ppm, M).
    VOCs: Dibromochloromethane (0.001 J ppm, M),
    PAHs: Benzo(a)pyrene (0.33 J ppm), benzo(g,h,i)perylene (0.42 ppm), dibenzo(a,h)anthracene (0.092 J), phenanthrene (0.51 J ppm).
    Sediment
    Metals: Lead (338 ppm, M).
    Corrective Activities:
    In the mid-1980s, the drain trough and the oil sump were capped with concrete.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The site is fenced, so unauthorized access would have been limited.
    Groundwater: No public health hazard is associated with the groundwater at this site. Modeling indicates that chemicals of concern in the soil will not reach the groundwater in concentrations that would exceed ATSDR comparison values.
    Flight Line Storm Drainage
    (SD-25)
    SD-25 is a 2,000 ft ditch into which 1) storm water runoff from the flight line area, parking lots and streets, and 2) wastewater from operations facilities drain. The runoff drains to a check dam, before being discharged to Canyon creek. Sediment samples indicated the presence of petroleum-based products and trace levels of metals along the length of the ditch.
    Sediment
    Metals: Arsenic (8.3 ppm), beryllium (1.8 ppm), lead (282.5 ppm).
    VOCs: Dibromochloromethane (0.003 J ppm).
    SVOCs: 4-Methyl phenol (2J ppm).
    PAHs: Benzo(a)anthracene (6.45 ppm), benzo(a)pyrene (6.44 ppm), benzo(b)fluoranthene (16 ppm, M), benzo(g,h,i)perylene (6.621 ppm), chrysene (10 ppm, M), dibenzo(a,h)anthracene (0.092 J ppm), indeno(1,2,3-c,d)pyrene (6.55 ppm), phenanthrene (6.884 ppm), TRPH (9,408.2 ppm).
    Surface Water
    VOCs: Bromodichloromethane (0.001 J ppm), dibromochloromethane (0.003 J ppm).
    SVOCs: Pentachlorophenol (0.004 J ppm), phenol (0.008 ppm).
    PAHs: 2-Methylnaphthalene (0.002 J ppm).
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. Public access to this site is restricted due to its proximity to the flight line, so exposure is unlikely.
    Surface Water: No public health hazard is associated with the surface water at this site. Public access to this site is restricted due to its proximity to the flight line, so exposure is unlikely.
    Drum Accumulation Pad
    (SS-26)
    SS-26 is a concrete slab which was used for the temporary storage of drums containing solvents and wastes (petroleum, oil, and lubricants) from the mid-1970s to 1990. A covered shed was built nearby in 1990. Soil samples were analyzed for VOCs and contained no contamination. Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Wash Rack
    (SD-27)
    SD-27 was constructed in the 1960s and consists of a concrete area, an unlined drainage ditch, and a concrete drum storage pad. The site was used to clean construction vehicles. Until the mid-1980s, the cleaning agent used was a petroleum-distillate based degreasing solution. In the fall of 1993, the drainage ditch was filled in and replaced with an oil/water separator and piping to remove the wastewater discharges. Shallow soils near the drum storage pad and drainage ditch sediments are contaminated with petroleum-based chemicals (but below ATSDR comparison values). Chromium, mercury, and zinc were detected above background levels but below ATSDR comparison values. Pesticides and metals were also found in the ditch.
    Surface Soil (0.5 - 1 foot)
    Metals: Arsenic (4.4 ppm, M), beryllium (0.94 ppm, M), lead (161 ppm, M).
    PAHs: 2-Methylnaphthalene (9.3 ppm, M), benzo(a)anthracene (17 ppm, M), benzo(a)pyrene (18 ppm, M), benzo(b)fluoranthene (32 ppm, M), benzo(g,h,i)perylene ( 13.0 ppm, M), chrysene (19 ppm, M), dibenzo(a,h)anthracene (4.6 ppm, M), indeno(1,2,3-c,d) pyrene (11 ppm, M), phenanthrene (23 ppm, M), TRPH (9,230 ppm, M).
    Sediment
    Metals: Arsenic (9.4 ppm, M), beryllium (0.91 ppm, M).
    PAHs: 2-Methylnaphthalene (0.66 ppm, M), 4-methylphenol (1.1 ppm, M), Benzo(a)anthracene (6.0 ppm, M), benzo(a)pyrene (8.8 ppm, M), benzo(b)fluoranthene (12 ppm, M), benzo(g,h,i)perylene (7.3 ppm, M), chrysene (9.5 ppm, M), dibenzo(a,h)anthracene (1.7 ppm, M), indeno(1,2,3-c,d) pyrene (7.8 ppm, M), phenanthrene (23 ppm, M), TRPH (3,050 ppm, M).
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. Public access is limited, as the site is surrounded by a chain link fence which is secured during non-working hours. Exposure is unlikely.
    Groundwater: No public health hazard is associated with the ground water at this site. Chemicals in the soil will not reach the groundwater in concentrations that would exceed state or federal requirements.
    Former Wash Water Accumulation Pit (SS-28) SS-28 is a water accumulation basin used to collect wastewater from the maintenance of a train engine. Wastewater solvents, oil, and petroleum products used in engine maintenance were also present in the basin. SS-28 was closed in 1987. Soil (1 foot)
    Metals: Beryllium (1.2 ppm, M), lead (13.4 ppm, M).
    Corrective Activities:
    When the pit closed in 1987, contaminated soils were excavated and disposed.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. Due to the industrial activities conducted at the site, access was limited. Present and future exposures will not occur as the site has been remediated.
    Accumulation Pad (SS-29) SS-29 was in operation from the 1970s until 1990. SS-29 consists of a fenced concrete pad used to store drums of chemical waste (solvents, penetrants, emulsifiers, fuel, and hydraulic oil). Spilled waste was reportedly observed around the perimeter of the fence in 1986. Surface and shallow subsurface soils contain some contamination. Zinc was detected above background levels but below ATSDR comparison values.
    Soil (0 feet)
    Metals: Barium (4,270 ppm, M), cadmium (748 ppm, M), lead (369 ppm, M).
    PAHs: Benzo(a)anthracene (3.146 ppm), benzo(a)pyrene (5.449 ppm), benzo(b)fluoranthene (53 ppm, M), benzo(k)fluoranthene (54 ppm, M), chrysene (23 ppm, M), dibenzo(a,h)anthracene (0.58 ppm), indeno(1,2,3-c,d)pyrene (2.73 ppm), TRPH (10,800 ppm, M).
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The site is fenced, preventing unauthorized access.
    Groundwater: No public health hazard is associated with the groundwater at this site. Contaminants in the soil will not reach the groundwater in concentrations that exceed state or federal standards.
    Defense Reutilization and Marketing Office Storage Area
    (SS-30)
    SS-30, a temporary storage area for drummed wastes collected on the base, was in operation from the 1970s until December 1987. Soil samples were analyzed for VOCs, SVOCs, pesticides/PCBs, herbicides, and metals.
    Soil (1 foot)
    Metals: Arsenic (2.9 ppm, M), lead (17.6 ppm, M).
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. Due to restricted access and the industrial nature of the site, public exposure is unlikely.
    Base Exchange Gas Station Site (ST-31) ST-31 consists of three underground storage tanks (10,000 gallons each) which were in operation from 1955 to 1996. The tanks contained the fuel used by the service station. A leak in one of the tanks and its pipe were discovered in 1992. The duration of the fuel release is not known but 800 cubic yards of contaminated soil were found. The site is covered with asphalt (4 inches) or gravel (5 inches). Soil samples indicate residual gasoline contamination (BTEX) is present at the bottom of the tank excavation site. Contaminants were not detected in the surface soil. The fuel did not migrate to the basalt bedrock below the site. Corrective Activities:
    • 800 cubic yards of contaminated soil were removed around the leak.
    • The underground storage tanks were removed.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site. The surface soil contains no contaminants and is not accessible.
    Groundwater: No public health hazard is associated with the groundwater at this site. Contaminants in the soil will not reach the groundwater in concentrations that would exceed state or federal standards.
    Military Gas Station Site
    (ST-32)
    ST-32 was constructed in 1948 to fuel military vehicles and was in operation until 1991. The site is about 30,000 square feet and is located at the intersection of 9th Avenue and B street (south corner). The center of the site consists of a concrete pad (60 x 80 ft) with six pumps. There is a small building just south of the pumps. The majority of the area is covered with asphalt, except for an area south of the building and along the fence line. There are three underground storage tanks (12,000, 19,000, and 5,000 gallons) used to dispense gasoline and diesel fuel on site. A leak to the subsurface soil from piping connections may have piping connections may have occurred in the vicinity of pump 2. The leak probably occurred before 1962 and the quantity of fuel involved is unknown. Soil samples, taken after the removal of the underground storage tanks, contained BTEX constituents below ATSDR comparison values. Rock core sampling indicated that no detectable concentrations of fuel constituents were found at a depth of 153.8 ft.

    Corrective Activities:
    The underground storage tanks were removed in 1992. Two tanker trucks currently supply unleaded gasoline and diesel fuel directly to service vehicles at the station.
    Current Status:
    • No further remedial action required.

    Soil: No public health hazard is associated with the soil at this site. Past exposures are not likely due to the depth of contamination. Current workers are not exposed to the contaminated soil as it is covered with asphalt.
    Groundwater: No public health hazard is associated with the groundwater at this site. Chemicals in the soil will not reach the groundwater in concentrations which exceed state or federal standards.
    Fuel Hydrant No. 9 System Leak Area
    (ST-34)
    ST-34 is a hydrant located near the middle of the main taxiway. It is almost entirely located under the concrete taxiway or the adjacent concrete parking apron. ST-34 was installed in the mid-1950s and was in operation until 1991. A leak (10 cubic gallons of jet fuel) was discovered in 1991. After initially replacing the fuel line, the hydrant and the surrounding soils were removed. Fuel constituents (BTEX) were detected below ATSDR comparison values. The fuel did not migrate further than 15 ft below the ground surface. Corrective Activities:
    • The hydrant and surrounding soils were removed.
    Current Status:
    • No further remedial action required.
    Soil: No public health hazard is associated with the soil at this site.
    Groundwater: No public health hazard is associated with the groundwater at this site. Chemicals in the soil will not reach the groundwater in concentrations which will exceed state or federal standards.
    Jet Fuel
    (JP-4) Pipeline Leak
    (ST-35)
    A fuel spill occurred at ST-35 in 1985 or 1986 when a pipeline was severed by a grading machine. Approximately 800 to 1,000 gallons of fuel were released, of which 350 to 400 gallons were recovered by the base. Soil screening showed no residual jet fuel contamination. Samples were not collected for analysis due to lack of visible signs of fuel contamination. Corrective Activities:
    • Soils were excavated over a 50 X 3.5 ft area around the spill. The soil was removed to a land farm on the base for remediation.
    Current Status:
    • No further remedial reaction required.
    Soil: No public health hazard is associated with the soil at this site.
    Underground Storage Tank
    (ST-39)
    ST-39 is located at Fire Training Area 8 and was in operation from the 1960s to the present. ST-39 is a 15,000 gallon underground storage tank used to store petroleum, aviation gas, jet fuel, and other petroleum products/solvents for fire training exercises. Investigation of the storage tank in 1993 indicated no evidence of a release.
    Soil (Depth Unspecified)
    Metals: Arsenic (3.2 ppm), lead (41 ppm, M).
    VOCs: Methylbutyl ketone (MBK) (0.008-220 ppm), TRPH (14,000 ppm, M).
    Current Status:
    • No further remedial reaction required.
    Soil: No public health hazard is associated with the soil at this site. Access to the site is restricted, so exposure is unlikely.
    Base-Wide Groundwater, Operable
    Unit 3
    Contamination of the base's drinking water supply is suspected. The groundwater investigation used to gather water quality information included 16 monitoring wells, 11 base production wells, and 12 off-base irrigation and domestic wells. The groundwater sampling program indicated trichloroethylene (3.0 ppb) in the groundwater on the south-central part of the base (near the former fire protection training areas). Earlier sampling of the base production wells by base personnel in compliance with the Safe Drinking Water Act showed TCE concentrations ranging from non-detect to 4.8 ppb. The maximum detected value exceeds ATSDR's CREG, but not EPA's MCL. Soil boring samples and rock cores indicate that the fuel released from the storage tanks and the lagoon landfill will not be capable of penetrating the thick bedrock zone which lies between the surface and the aquifer. Trihalomethanes (bromoform, bromodichloromethane, and chlorodibromomethane) have been detected in exceedance of CREG values but below MCLs. The trihalomethanes may result from the chlorination process used for the base's water supply.
    Drinking Water (Base Production Wells)
    VOCs: Benzene (1.4 ppb), bromoform (53.8 ppb), bromodichloromethane (2.8 ppb), chlorodibromomethane (1.1 ppb), TCE (4.8 ppb).
    SVOCs: Pentachlorophenol (0.65 ppb).
    Metals: Arsenic (3.8 ppb), vanadium (100 ppb).
    Groundwater (Monitoring Wells)
    SVOCs: BIS(2-Ethylhexyl)phthalate (120 ppb).
    Metals: Barium (893 ppb), beryllium (5.6 ppb), manganese (2,490 ppb).
    Current Status:
    • All sites will be subject to long-term monitoring and the status of groundwater at Mountain Home AFB will be re-evaluated every 5 years as stipulated by the Record of Decision (ROD).
    Groundwater: No Public health hazard is associated with the groundwater at this site. Conservative estimates of potential exposures show that there are no health hazards associated with consuming the maximum TCE, bromoform, bromodichloromethane, and chlorodibromo-methane concentrations detected.
    Wilder Air Force Station (OT-36) OT-36 is located 40 miles west of Boise, near the Oregon border. The site encompasses 10.7 acres on a hill overlooking the Snake River. A preliminary assessment and site investigation conducted in June 1994 indicated that there were no human health risks associated with exposure to site contaminants. Current Status:
    • No further action was recommended.
    Soil: No public health hazard is associated with the soil at this site.
    Groundwater: No public health hazard is associated with the groundwater at this site.
    Saylor Creek Range
    (OT-37)
    OT-37 is located to the northeast of the base and has been in operation since 1944. The range was used for detonation of various types of explosives (napalm, low/high order explosives, and tracer and armor piercing rounds). Vehicle/equipment maintenance and government facilities are located there as well and could have potentially released solvents, degreasers, and petroleum products into the surrounding environment. A preliminary assessment and site investigation (1995) indicated that there were no human health risks associated with exposure to site contaminants. Current Status:
    • No further action was recommended.
    Soil: No public health hazard is associated with the soil at this site.
    Groundwater: No public health hazard is associated with the groundwater at this site.
    Coal Storage Yard (Area of Concern [AOC-7]) AOC-7 was used for the storage of coal reserves between 1943 and 1993. AOC-7 encompasses a heat plant building, a concrete storage pad, an auxiliary generator and fuel tank, and other miscellaneous equipment associated with power generation. Although coal residue (1-18 inches) is present, the preliminary assessment (September 1996) concluded that there had been no release to the soil. Current Status:
    • No further action was recommended.
    Soil: No public health hazard is associated with the soil at this site. Most of the base population lives further than 1 mile away from this site. The annual rainfall (~8 inches) limits coal leaching.
    Groundwater: No public health hazard is associated with the groundwater at this site.
    Motor Pool Area "A" (AOC-9) AOC-9 has been in operation from 1943 to the present and is used for the repair and maintenance of refueling vehicles. A preliminary assessment (September 1996) concluded that there had been no release of contaminants to the soil. Current Status:
    • No further action was recommended.
    Soil: No public health hazard is associated with the soil at this site.
    Strike Dam Recreation Annex
    (AOC-10)
    AOC-10 is located on the northern section of the C.J. Strike Reservoir, approximately 8 miles southwest of the base. The facility consists of an office, reception area, patio, and storage building. Minor equipment maintenance and refueling occur on the site. Hazardous materials used at this site include gasoline, cleaning solvents, oil, greases, heating oil, transmission fluid, and battery acid. A preliminary assessment (September 1996) concluded that there had been no releases of hazardous materials at the site. Current Status:
    • No further action was recommended.
    Soil: No public health hazard is associated with the soil at this site.
    Precision Bombing Ranges 1,2,3 and 4
    (AOC1-4)
    AOC1-4 were constructed in 1943 and were used for bomb scoring evaluations. Preliminary site investigations found that these sites did not pose risks to human health. Current Status:
    • A RCRA Facilities Assessment found that no further action was required.
    Soil: No public health hazard is associated with the soil at this site.
    Small Arms Range (SAR) SAR is located 1 mile north of the base. The site was used for small arms and explosive ordnance disposal proficiency training. A preliminary site investigation found that this site did not pose risks to human health. Current Status:
    • A RCRA Facilities Assessment found that no further action was required.
    Soil: No public health hazard is associated with the soil at this site.
    Munitions Burial Site (Inactive), Saylor Creek Range
    (AOC-6)
    AOC-6 is located on Saylor Creek Range which is east of the base. The site is thought to have been used for the disposal of munitions residues from the 1940s to the early 1950s. A preliminary site investigation found that this site did not pose risks to human health. Current Status:
    • A RCRA Facilities Assessment found that no further action was required.
    Soil: No public health hazard is associated with the soil at this site.
    Pothole Canyon Burial Site (Inactive)
    (AOC-11)
    AOC-11 is located on Saylor Creek Range which is east of the base. The site is thought to have been used for the disposal of hazardous waste. A preliminary site investigation found that this site did not pose risks to human health. Current Status:
    • A RCRA Facilities Assessment found that no further action was required.
    Soil: No public health hazard is associated with the soil at this site.
    Oil/Water Separators
    (AOC-8)
    There are approximately 48 oil/water separators on the base and they have been used since the 1940s. Prior to 1980s, oil/water separators were used for hazardous waste disposal. A RCRA Facilities Assessment has been conducted. The Idaho Department of Environmental Quality inspected the oil/water separators on the base (May 1, 1996). Corrective Activities:
    •The oil/water separators have been decommissioned and associated underground storage tanks have been removed.
    Current Status:
    • The Final Oil/Water Separator Decommissioning Report recommended no further action.
    Soil: No public health hazard is associated with the soil at this site.

    1 Chemicals listed exceed ATSDR comparison values.
    Italics indicate ATSDR comparison values are not available and that the concentration exceeds EPA Region III Risk-Based Concentrations.
    Underlining indicates that neither ATSDR comparison values or EPA RBCs are available.
    Soil concentrations are 95% confidence limits unless otherwise indicated.
    M= maximum soil concentration.
    Soils of unspecified depths will be re-evaluated when ERG receives supporting documentation.
    Sources: Radian (1990), Resources Conservation Company (1989), Woodward-Clyde (1991, 1992, 1993, 1994, 1995).
    PAH = Polycyclic aromatic hydrocarbons
    TRPH = Total recoverable polycyclic hydrocarbons
    VOCs = Volatile organic compounds
    SVOCs = Semi-volatile organic compounds
    TVOCS = Total volatile organic compounds


    FIGURES


    Figure 1. Regional Location of Mountain Home AFB


    Figure 2. Mountain Home AFB Installation Restoration Program Sites


    Figure 2. Mountain Home AFB Installation Restoration Program Sites (continued)


    Figure 3. Mountain Home Air Force Base


    Figure 4. ATSDR's Exposure Evaluation Process


    Figure 5. Location of On-Base Production (BPW) and Monitoring Wells (MW)



    APPENDIX A: GLOSSARY

    Background Level
    A typical or average level of a chemical in the environment. Background often refers to naturally occurring or uncontaminated levels.
     
    CERCLA
    The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, also known as Superfund. This is the legislation that created ATSDR.

    Comparison Values
    Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body wight. The comparison values are calculated from the scientific literature available on exposure and health effects.

    Concentration
    The amount of one substance dissolved or contained in a given amount of another. For example, sea water contains a higher concentration of salt than fresh water.

    Contaminant
    Any substance or material that enters a system where it is not normally found, or that is found in greater concentrations than background levels.

    Environmental Contamination
    The presence of hazardous substances in the environment. From the public health perspective, environmental contamination is addressed when it potentially affects the health and quality of life of people living and working near the contamination.

    Exposure
    Contact with a chemical by swallowing, by breathing, or by direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic).

    Hazard
    A source of risk that does not necessarily imply potential for occurrence. A hazard produces risk only if an exposure pathway exists, and if exposures create the possibility of adverse consequences.

    Media
    Soil, water, air, plants, animals, or any other parts of the environment that can contain contaminants.

    Minimal Risk Level (MRL)
    An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncancer) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration via a given route of exposure. MRLs are based on noncancer health effects only. MRLs can be derived for acute, intermediate and chronic duration exposures by inhalation and oral routes.

    National Priorities List (NPL)
    EPA's listing of sites that have undergone preliminary assessment and site inspection to determine which locations pose an immediate threat to persons living or working near the release. These sites are most in need of cleanup.

    No Apparent Public Health Hazard
    The designation given to sites where human exposure to contaminated media is occurring or has occurred in the past, but the exposure is below a level of health hazard.

    Potentially Exposed
    The condition where valid information, usually analytical environmental data, indicates the presence of contaminant(s) of a public health concern in one or more environmental media contacting humans (e.g., air, drinking water, soil, food chain, surface water). There is evidence that some of those persons may have an identified route(s) of exposure (e.g., drinking contaminated water, breathing contaminated air, having contact with contaminated soil, or eating contaminated food).

    Public Health Assessment
    The evaluation of data and information on the release of hazardous substances into the environment in order to assess any current or future impact on public health, develop health advisories or other recommendations, and identify studies or actions needed to evaluate and mitigate or prevent human health effects; also, the document resulting from that evaluation.

    Route of Exposure
    The path in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.

    Semi-Volatile Organic Compounds (SVOCs)
    Compounds amenable to analysis by extraction of the sample with an organic solvent. Polycyclic aromatic hydrocarbons, such as naphthalene, phenanthrene, benzo(a)pyrene, and chrysene, comprise one category of SVOCs. The term SVOCs is used synonymously with base/neutral and acid extractable compounds (BNAs).

    Volatile organic compound (VOC)
    Substance containing carbon and different proportions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily become vapors or gases. A significant number of the VOCs are commonly used as solvents (e.g., paint thinners, lacquer thinners, degreasers, dry cleaning fluids).


    APPENDIX B: COMPARISON VALUES

    The conclusion that a contaminant exceeds the comparison value does not mean that it will cause adverse health effects. Comparison values represent media-specific contaminant concentrations that are used to select contaminants for further evaluation to determine the possibility of adverse public health effects.

    Cancer Risk Evaluation Guides (CREGs)

    Estimated contaminant concentrations that would be expected to cause no more than one excess cancer in a million (10-6) persons exposed over a 70-year life span. ATSDR's CREGs are calculated from EPA's cancer potency factors.

    Environmental Media Evaluation Guides (EMEGs)

    EMEGs are based on ATSDR minimal risk levels (MRLs) and factors in body weight and ingestion rates. An EMEG is an estimate of daily human exposure to a chemical (in mg/kg/day) that is likely to be without noncarcinogenic health effects over a specified duration of exposure.

    Maximum Contaminant Level (MCL)

    The MCL is the drinking water standard established by EPA. It is the maximum permissible level of a contaminant in water that is delivered to the free-flowing outlet. MCLs are considered protective of public health over a lifetime (70 years) for people consuming 2 liters of water per day.

    Reference Media Evaluation Guides (RMEGs)

    ATSDR derives RMEGs from EPA's oral reference doses. The RMEG represents the concentration in water or soil at which daily human exposure is unlikely to result in adverse noncarcinogenic effects.


    APPENDIX C: ESTIMATED EXPOSURES AND HEALTH EFFECTS FOR CONSUMPTION OF CONTAMINANTS OF GROUNDWATER

    ATSDR typically evaluates the public health implications of exposure by considering the contaminant's chemical class, concentrations of the contaminants to which people may have been exposed, and how often and how long exposure to those contaminants occurred. Health effects are also related to individual characteristics such as age, gender, and nutritional status that influence how a chemical might be absorbed, metabolized, and eliminated by the body. Together, these factors help influence the individuals response to chemical contaminant exposure and potential noncarcinogenic and carcinogenic outcomes.

    ATSDR used to following equation to estimate an exposure dose for ingestion of water:

    Estimated exposure dose= Concentration x IR x EF x ED
    BW x AT


    where:


    Concentration = Maximum concentration in the water (ppm).
    IR= Ingestion rate: 2 liters per day (adult); 1liter per day (child)
    EF= Exposure frequency or number of exposure events per year of exposure
    ED= Exposure duration or the duration over which exposure occurs
    BW= Body weight: 70 kg (adult); 10 kg (child)
    AT= Averaging time or the period over which cumulative exposures are averaged

    When evaluating noncancer effects, ATSDR compares the estimated exposure dose to standard toxicity values, including ATSDR's minimal risk levels (MRLs) and EPA's reference doses (RfDs), to determine whether adverse effects will occur. The chronic MRLs and RfDs are estimates of daily human exposure to a substance that are likely to be without appreciable risk of adverse noncancer effects over a specified duration. The chronic MRLs and RfDs are conservative values, based on the levels of exposure reported in the literature that represent no-observed-adverse-effects levels (NOAEL) or lowest-adverse-effects-levels (LOAEL) for the most sensitive outcome for a given route of exposure (e.g. dermal contact, ingestion). In addition, uncertainty (safety) factors are applied to NOAELs or LOAELs to account for variation in the human population and uncertainty involved in extrapolating human health effects from animal studies.

    When evaluating the potential for cancer to occur, ATSDR uses cancer potency factors (CPF) that define the relationship between exposure doses and the likelihood of an increased risk of developing cancer over a lifetime. The CPFs are developed using data from animal or human studies and often require extrapolation from high exposure doses administered in animal studies to lower exposure levels typical of human exposure to environmental contaminants. The CPF represents the upper-bound estimate of the probability of developing cancer at a defined level of exposure; therefore, they tend to be very conservative (i.e., overestimate the actual risk) in order to account for a number of uncertainties in the data used in extrapolation.

    ATSDR estimated the potential for cancer to occur using the following equation. The estimated exposure doses and CPF values for the contaminants of concern are incorporated into the equation:

    Lifetime Cancer Risk = Estimated exposure dose (mg/kg/day) x CPF (mg/kg/day)-1

    Although no risk of cancer is considered acceptable, because a zero cancer risk is not possible to achieve, ATSDR often uses a range of 10-4 to 10-6 estimated lifetime cancer risk (or 1 new case in 10,000 to 1,000,000 exposed persons), based on conservative assumptions about exposure, to determine whether there is a concern for cancer effects.

    Estimated Exposure Dose for Consumption of Trichloroethylene in On-Site Drinking Water

    The maximum detected concentration of TCE (4.8 ppb) in on-site drinking water slightly exceeded ATSDR's CREG of 3 ppb, but was below EPA's MCL of 5 ppb. To determine the potential for adverse health effects from exposure to TCE in the on-site drinking water supply, ATSDR estimated an oral exposure dose using very conservative assumptions for on-site residents (including children and adults). On-site workers would consume less water over a shorter time period than residents so the exposure for an on-site worker is considered to be less than that of a resident. ATSDR assumes that if conservative exposure dose estimates indicate that adverse health effects are unlikely for residents consuming the drinking water, that this would also be the case for on-site workers. ATSDR assumed that a 70 kg resident drinks 2 liters of water and a 10 kg child drinks 1 liter at a frequency of 365 days a year for 30 years for adults and for 6 years for children (even though the average duration of stay on the base is 3 years). ATSDR assumed that the water contains the maximum TCE concentration detected (4.8 ppb) in the drinking water supply.

    Noncancer

    In the ATSDR Toxicological Profiles, MRLs are developed for acute, intermediate, and chronic exposure intervals. A MRL for TCE is only available for acute (14 days or less) exposures and was used to evaluate potential noncancer effects associated with drinking water exposures. The resulting estimated exposure doses of 0.00014 mg/kg/day for adults and 0.00048 mg/kg/day for children do not exceed ATSDR's MRL of 0.2 mg/kg/day for acute oral exposure. A chronic oral exposure MRL or a chronic oral RfD is not available for TCE. ATSDR reviewed the available toxicologic studies using intermediate and chronic exposures for animals and found that the conservative exposure dose estimates for Mountain Home AFB were at least 100 times less than the lowest LOAEL in the literature. ATSDR does not expect the use of the drinking water to cause noncarcinogenic health effects for residents (children and adults) or on-site workers.

    Cancer

    Although TCE has been shown to produce cancer in experimental animals when administered in large doses, the link between TCE in drinking water and human cancer cases is not well established (ATSDR, 1997). EPA, in an effort to determine a cancer classification for TCE, is currently reviewing the scientific literature pertaining to the carcinogenicity of TCE. For screening purposes, ATSDR used a previously derived CPF for TCE of 0.011 (mg/kg/day). This approach provides a conservative evaluation of the likelihood of exposures to TCE in the base's drinking water supply. ATSDR derived a lifetime cancer estimate from drinking water from the base production wells of 7 x 10-7 (or an increased likelihood of 7 in 10 million of developing cancer). As the estimate is lower than the "acceptable" range of 10-4 to 10-6, ATSDR concludes that detected concentrations of TCE are not likely to be associated with an increased likelihood of cancer in residents and workers consuming on-site drinking water.

    Estimated Exposure Dose for Consumption of Bromoform in On-Site Drinking Water

    Noncancer

    Bromoform was present in on-site drinking water at levels above ATSDR's CREG of 4 ppb, but below the enforceable EPA MCL of 100 ppb (proposed). To determine the potential for adverse health effects from exposure to bromoform in the on-site drinking water supply, ATSDR used the same conservative assumptions as for TCE. ATSDR assumed that the water contains the maximum bromoform concentration (53.8 ppb) detected in the drinking water supply. The resulting estimated exposure doses of 0.0015 mg/kg/day, for residents, and of 0.0053 mg/kg/day, for children, do not exceed ATSDR's MRL of 0.2 mg/kg/day or EPA's RfD of 0.02 mg/kg/day for chronic oral exposure. ATSDR does not expect the consumption of drinking water to cause noncarcinogenic health effects for residents (children and adults) or on-site workers.

    Cancer

    Chronic animal studies have shown that bromoform has carcinogenic effects. Bromoform, administered orally, caused an increased incidence of tumors in the large intestine of rats, but not in mice (ATSDR, 1990). There are no studies pertaining to carcinogenic effects of oral bromoform exposures in humans. Epidemiological studies have shown a possible association between chronic ingestion of chlorinated water and increased cancer in humans; however, the carcinogenic constituent or group of constituents in the chlorinated water has not been clearly isolated (ATSDR, 1990). Bromoform is classified by the EPA as a "probable human carcinogen." ATSDR derived a lifetime cancer estimate for bromoform in drinking water from the base production wells of 1 x 10-5. As the estimate falls within the range of 10-4 to 10-6, ATSDR does not consider an increased risk of cancer from bromoform to be a concern for residents and on-site workers consuming the on-site drinking water.

    Estimated Exposure Dose for Consumption of Bromodichloromethane in On-Site Drinking Water

    Noncancer

    Bromodichloromethane was present in on-site drinking water at levels above ATSDR's CREG of 0.6 ppb, but below the enforceable EPA MCL of 100 ppb (proposed). To determine the potential for adverse health effects from exposure to bromodichloromethane in the on-site drinking water supply, ATSDR used the same conservative assumptions as for TCE. ATSDR assumed that the water contains the maximum bromodichloromethane concentration (2.8 ppb) detected in the drinking water supply. The resulting estimated exposure dose of 0.00008 mg/kg/day, for residents, and of 0.00028 mg/kg/day does not exceed ATSDR's MRL or EPA's RfD of 0.02 mg/kg/day for chronic oral exposure. ATSDR does not expect the consumption of the drinking water to cause noncarcinogenic health effects for residents (children and adults) and on-site workers.

    Cancer

    EPA has classified bromodichloromethane as a "probable human carcinogen". Increased incidences of liver, kidney, and renal tumors were observed as a result of chronic oral bromodichloromethane exposures in rats (ATSDR, 1989). There are no studies of the carcinogenic effects of chronic oral exposure to bromodichloromethane in humans, although there is some epidemiological evidence that increased cancer incidences result from the consumption of chlorinated water (which typically contains bromodichloromethane), the causal agent has not yet been identified (ATSDR, 1989). ATSDR derived a lifetime cancer estimate for bromoform in drinking water from the base production wells of 5 x 10-6. As the estimate falls within the range of 10-4 to 10-6, ATSDR does not consider an increased risk of cancer from bromoform to be a concern for residents or on-site workers consuming the drinking water.

    Estimated Exposure Dose for Consumption of Chlorodibromomethane in On-Site Drinking Water

    Noncancer

    Chlorodibromomethane was present in on-site drinking water at levels above ATSDR's CREG of 0.4 ppb, but below the enforceable EPA MCL of 100 ppb (proposed). To determine the potential for adverse health effects from exposure to chlorodibromomethane in the on-site drinking water supply, ATSDR used the same conservative assumptions as for TCE. ATSDR assumed that the water contains the maximum chlorodibromomethane concentration (1.1 ppb) detected in the drinking water supply. The resulting estimated exposure dose is 0.000031 mg/kg/day, for residents, and of 0.00011 mg/kg/day, for children, which do not exceed ATSDR's MRL of 0.03 mg/kg/day or EPA's RfD of 0.02 mg/kg/day for chronic oral exposure. ATSDR does not expect the consumption of the drinking water to cause noncarcinogenic health effects for residents (children and adults) and on-site workers.

    Cancer

    Chlorodibromomethane is classified by the EPA as a "possible human carcinogen." Although chronic animal studies indicate an increased incidence of liver tumors in mice, there are no carcinogenic studies for humans (ATSDR, 1990). Epidemiological data suggests an association between the chronic consumption of chlorinated water (of which chlorodibromomethane is a constituent) and an increased incidence of cancer in humans (ATSDR, 1990). ATSDR also derived lifetime cancer estimates for chlorodibromomethane in drinking water from the base production wells of 3 x 10-6. As the estimate falls within the range of 10-4 to 10-6, ATSDR does not consider and increased risk of cancer from chlorodibromomethane to be a concern for residents or workers consuming the on-site drinking water.


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