PUBLIC HEALTH ASSESSMENT
EDWARDS AIR FORCE BASE
EDWARDS AIR FORCE BASE, KERN COUNTY, CALIFORNIA
ATSDR identified community health concerns through meetings with community members, state and local officials, and EAFB personnel, and through review of site documents, including RODs and Community Relations Plans.
In 1986, Kern County Health Department initiated an investigation of childhood cancers in Rosamond upon discovering eight incidences of cancer between 1975 and 1984. In November 1986, CADHS joined Kern County in its investigation, with the Environmental Epidemiology and Toxicology Section (now the Environmental Epidemiology and Toxicology Program) examining individual cancer cases and the Toxic Substances Control Division (now DTSC) looking at sites in and around Rosamond to determine if there were toxic contaminants in the environment that may have contributed to the high incidences of cancer. Thirty-four sites merited further investigation into the nature and extent of possible contamination (CADHS 1989b). The sites were studied to determine cleanup needs under state and federal environmental regulations, and remediation actions have been ongoing (CADHS 1989a). In 1989, CADHS tested soil and water in Rosamond School, a park, and homes where people with cancer resided, in addition to collecting samples of soil, eggs, and pork from the Rosamond community. These efforts did not find a connection between childhood cancer incidence and environmental factors. In 1991, CADHS conducted a four-county (Fresno, Kern, Kings, and Tulare) study of childhood cancer incidence. The study found the distribution of childhood cancers across communities of the entire Four County area during 1980-1988 not to be significantly different than would be expected. Some communities within the four counties exhibited higher-than-expected incidences of cancer, while other communities exhibited lower-than-expected incidences of cancer (CADHS 1991).
Contaminants at EAFB have not migrated off base and therefore would not provide a point of exposure to residents of Rosamond (see previous sections of this PHA for more details). In addition, though local factors have not been conclusively linked to the high rate of childhood cancer, it is extraordinarily unlikely that a more remote source, EAFB, would have contributed to cancer incidences.
For community members who are concerned about Rosamond cancer investigations, ATSDR suggests contacting Martha Harnly of CADHS. CADHS has recently distributed an updated factsheet related to the high incidences of cancer and will be posting it on their Web site (http://www.dhs.ca.gov) in the near future. For other concerns related to cancer incidence in California, Paul Mills, of the Cancer Registry of Central California, may be contacted.
California Department of Health Services
Environmental Health Investigations Branch
1515 Clay St., Suite 1700
Oakland, CA 94612
Cancer Registry of Central California
1625 East Shaw Ave., Suite 155
Fresno, CA 93710-8100
During the February 2001 RAB meeting, a RAB member expressed concern about a former bombing range, which was reportedly located beyond the current EAFB boundaries in California City. California City is a small community located north of EAFB (RAB 2001).
During World War II, the U.S. Navy took possession of 22,400 acres of land between California City and Mojave. The Navy used this land as a range for bombing, artillery, anti-aircraft, and anti-tank practice by the Marine Corps Air Station, Mojave. This practice area was called the Mojave C Bombing Range. In the 1960s and 1970s, 21,756.07 acres were relinquished to the original owners. The remaining 643.93 acres are owned by the Navy and are leased to private contractors. None of the area is affiliated with EAFB (DTSC 1998; U.S. Army 1999).
ATSDR visited the former Mojave C Bombing Range during its May 2002 site visit. The Mojave range is fully accessible to the public and shows evidence of all-terrain vehicle use and recreational shooting. ATSDR observed scattered "Land for Sale" signs across the former bombing range land, but no evidence of people living in those areas. ATSDR observed numerous remnants of former military use, including large craters, pieces of exploded ordnance, and spent casings.
It is possible that unexploded ordnance (UXO) exists in the area of the former bombing range, but EAFB's Explosive Ordnance Division has not received any reports, or experienced any incidents or accidents, related to UXO contact in that area (John O'Kane, DTSC/FUDS, personal communication, 2002). (Although EAFB is not affiliated with the range, it is the closest Department of Defense installation in the area and would therefore handle any incident reports.)
The Department of Defense has designated the inactive areas of the range a Formerly Used Defense Site (FUDS) (U.S. Army 1999). The Army is the executive agent for the FUDS program and the U.S. Army Corps of Engineers (USACE) is the organization that manages and executes the program (USACE 2002). DTSC is currently working with USACE to determine appropriate investigation and cleanup schedules for the range. Concerned community members may contact Ed Walker, DTSC, for more information.
California Environmental Protection Agency
Department of Toxic Substances Control, Office of Military Facilities
8800 Cal Center Drive
Sacramento, CA 95826-3200
Pentaborane was manufactured in the late 1950s and 1960s as an experimental rocket propellant under an Air Force research program. From the 1950s until the 1990s, over 400 cylinders containing pentaborane, a highly toxic rocket fuel, were stored in a liquid propellant storage complex at Operable Unit 9. Because continued storage of pentaborane could result in an uncontrolled release, EAFB determined that public safety was best protected with controlled disposal of the fuel. Open burning was selected as the best method for pentaborane cylinder destruction (AFFTC 1998b; AFCEE/EMD 1997). As a result, approximately 209,582 pounds (412 cylinders) of pentaborane were destroyed at EAFB between 1994 and 1999. All open burns were conducted in OU 9 approximately 5 miles from the EAFB property line (AFFTC/EMR 2002g).
Before the burning, EAFB conducted air dispersion modeling to predict pentaborane concentrations during destruction. A risk assessment was performed that set the allowable limit for pentaborane concentrations at 0.1 ppb at the EAFB boundary (AFCEE/EMD 1997). To stay within public health limits, all pentaborane destruction activities were conducted on days with very specific climatic factors (i.e., air temperature above 50 F, no inversion below 2,000 ft, wind speeds between 5 and 15 miles per hour, wind blowing toward the west-southwest) (AFFTC/EMR 2002g). During burning, EAFB conducted monitoring and analysis to characterize the smoke plume and mitigate possible environmental or human health effects that could be associated with chemicals in the smoke plume (AFFTC 1998b). The nearest toxic gas monitor detected a small concentration of pentaborane during one of the burn events, but no pentaborane or diborane was detected by instruments downwind during any events (AFCEE/EMD 1997; AFFTC/EMR 2002g).
Soil sampling was also performed for pre-burn and post-burn operations throughout both phase I and phase II destruction activities. The soil samples were analyzed for boron, lead, and pH. Except for a few elevated detections of lead and boron within 50 ft of the test pads, the soil sample results indicated no adverse impact on the environmental media as a result of the pentaborane disposal (AFFTC/EMR 2002g). People are not expected to come in contact with soil near the burn pads, since the pads are located in a restricted area of the base (AFFTC 1998b).
ATSDR concludes that past pentaborane destruction activities are not likely to result in adverse health effects.
Piute Ponds encompasses approximately 560 acres in the southwestern corner of EAFB. The ponds are a series of interconnected surface-water impoundments whose primary water source is treated effluent from Los Angeles County District 14's wastewater treatment facility--Lancaster Water Reclamation Plant--located just outside the western boundary of the base. EAFB is not a potential source for any pond contamination. The ponds contain water year round; as a result, desert wildlife and waterfowl are attracted to the area. EAFB allows educational activities, nature study, birdwatching, and duck hunting at Piute Ponds. (EAFB 1989; AFFTC 1998b).
In 1996, a scientist from the California Science Center, Davis, trapped African clawed frogs from Piute Ponds. Of the 50 animals trapped, 5 showed abnormalities (i.e., blind eye, crooked spine, undeveloped reproductive system, abnormally shaped fat bodies, and an extra forelimb). The cause of these abnormalities was not determined (USGS 1996). Because of this observation, community members have speculated about possible contamination present in Piute Ponds.
To support a reproductive bird study, the U.S. Geological Survey (USGS) analyzed African clawed frogs collected from Piute Ponds and concluded that they were not contaminated with organochlorine pesticides or polychlorinated biphenyls (PCBs). Metals and trace elements were detected in frogs, but mean concentrations and upper ranges were not thought to be sufficient to adversely affect bird reproduction. USGS also monitored 226 bird nests in 1999 and found metals and trace elements in avian eggs, but at concentrations that were not likely to be sufficient to cause impaired reproduction. Organochlorine pesticides and PCBs were not found in ducks and avocets (USGS 2001).
In 1998, EAFB conducted water and sediment grab sampling at Piute Ponds and a background location (Rosamond Dry Lakebed). All water samples were analyzed for VOCs, SVOCs, pesticides and PCBs, chlorinated herbicides, metals, surfactants, total suspended solids, total dissolved solids, fecal coliform as E. coli, and total fecal coliform. All sediment samples were analyzed for VOCs, SVOCs, pesticides and PCBs, chlorinated herbicides, and metals. Water samples were within their respective water quality standards or Lancaster Water Reclamation Plant effluent limits for all contaminants except for thallium, whose maximum concentration was 18 ppb. Sediment samples were within health-based guidelines for all parameters (AFFTC 1998c). EAFB transferred Piute Ponds to "no further investigation"' status in 1999, with the approval of oversight regulatory agencies.
Because people are not fishing or swimming in Piute Ponds, and no one is drinking the water from the ponds, the primary potential exposure route for recreational users of Piute Ponds would be eating waterfowl that were hunted and caught during hunting season. For this reason, ATSDR more closely examined sampling data to determine if any detected contaminants are known to bioconcentrate in ducks or geese. (Bioconcentration refers to the accumulation of a chemical in the tissues of an organism at levels greater than in the surrounding medium.) Thallium is the only contaminant detected in Piute Ponds that is known to bioconcentrate.
In order to determine if thallium concentrations detected in surface water at Piute Ponds pose a potential health risk to people who eat hunted waterfowl, ATSDR would, ideally, examine tissue concentrations of ducks and geese collected at Piute Ponds. However, these data are not available, so ATSDR attempted to estimate concentrations of thallium in waterfowl and the frequency with which people might eat that waterfowl. ATSDR was not able to locate data that specifically related surface-water concentrations of thallium to concentrations of thallium in edible portions of ducks or geese (called a bioconcentration factor, or BCF). However, the U.S. Department of Energy (DOE) has developed a BCF for relating surface-water concentrations of thallium to concentrations of thallium in animals at different trophic (food chain) levels (ORNL 1996). Because thallium is a chemical that bioconcentrates, but does not biomagnify (biomagnification occurs when a chemical increases in concentration at successive trophic levels), DOE's BCF of 34 is the same for ducks and geese as for other aquatic or aquatic-consuming organisms.
ATSDR does not have data related to the actual consumption of duck and/or geese by hunters at EAFB, but we do have data from a study about the consumption patterns of waterfowl hunters in Quebec, Canada, where similar waterfowl species are located and the hunting season is of comparable length. In the Canadian study, 92.7 percent of respondents had hunted during the previous hunting season, averaging 7.6 trips per year and 15 birds obtained (Duchesne et al. 2001). The hunters reported eating an average of 7.5 meals of hunted waterfowl annually, with an average meal consisting of 180.9 grams of meat (Duchesne et al. 2001). For the purposes of the Piute Ponds estimate, ATSDR assumed that EAFB personnel would consume similar amounts of waterfowl meat. Finally, to ensure a conservative estimate, ATSDR assumed that people would eat this quantity of waterfowl every year for 30 years over the course of their lifetime. It is very unlikely that people will be stationed at EAFB and continue to hunt and eat waterfowl from Piute Ponds continually over a 30-year period, but ATSDR wants to be sure we are using protective assumptions about consumption.
Using the preceding parameters and the maximum value of thallium detected, ATSDR estimates that someone would ingest approximately 3.3 × 10-5 milligrams per kilogram of body weight per day (mg/kg/day) of thallium by eating waterfowl caught from Piute Ponds. This value is less than half the EPA reference dose (RfD) of 7 x 10-5 mg/kg/day. Even if someone were to consume two times as many waterfowl meals per year as in the Canadian study, their thallium ingestion would be below the RfD. Therefore, ATSDR does not believe that eating waterfowl hunted from Piute Ponds would result in adverse health effects. ATSDR is unaware of any other viable pathways of exposure and concludes that recreational users of Piute Ponds are not being and will not likely be exposed to harmful levels of contaminants.
ATSDR recognizes that infants and children may be more sensitive to exposures than adults in communities with contamination in water, soil, air, or food. This sensitivity is the result of a number of factors. Children are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. Children are shorter than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children are also smaller, potentially resulting in higher doses of chemical exposure per unit body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care. Therefore, ATSDR is committed to evaluating their special interests at sites such as EAFB as part of the ATSDR Child Health Initiative.
ATSDR has attempted to identify populations of children in the vicinity of EAFB. Approximately 1,450 children under the age of 10 years live within the census tracts of EAFB (U.S. Census Bureau 2000). A child development center, two elementary schools, a middle school, a high school, a Teen Center, a Youth Activities Center, and a Boy Scout camp are all located on base (EAFB 2002a).
Like other people living or working at or near EAFB, children may contact contaminated site media. As discussed in the "Evaluation of Environmental Contamination and Potential Exposure Situations" and "Community Health Concerns" sections of this PHA, past, current, and future exposures for children could include arsenic in groundwater and dioxins in air.
To evaluate whether children may experience adverse health effects through past, current, or future exposures to site contaminants, ATSDR estimated the potential doses for children. To estimate these doses, ATSDR used very conservative assumptions that overestimate the levels of actual exposure. ATSDR concluded that exposure to site contamination at EAFB does not pose unique health hazards for children. This conclusion is based on ATSDR's exposure evaluation and the following information:
- In the past, on-base children may have been exposed to arsenic in groundwater pumped from one community supply well at North Base. To evaluate exposures, ATSDR assumed that children were exposed to the maximum detected contaminant concentration over the entire exposure period. ATSDR also used extremely conservative assumptions about how often and how long children are exposed to arsenic. Actual exposures are expected to be less frequent, of lower magnitude, and over a shorter duration than those assumed by ATSDR. A comparison of estimated exposure doses to ATSDR's minimal risk levels and the toxicology literature did not identify exposure levels for children that are likely to result in adverse health effects.
- Children are not expected to have been exposed to CWM. No on-base areas that were identified as having the potential for buried CWM have shown any evidence of being contaminated. Adverse health effects to children from CWM in soil are not expected.
- Children may have been and may continue to be exposed to dioxins in air from DESs at Sites 16 and 18. However, wind patterns show that dioxins released from Sites 16 and 18 predominantly blow away from the residential areas of the base. In addition, Sites 16 and 18 are in relatively industrial areas of the base, within the Main Base flightline, so any exposure of children would be infrequent and of short duration. Adverse health effects to children from dioxins in air are not expected.
Current and future exposures to contaminated drinking water by children are not expected. EAFB has discontinued use of the arsenic-contaminated well, eliminating it as a potential source of exposure. Plume-related contamination has not reached any on-base or off-base drinking water supply sources. Therefore, current and future exposures pose no public health hazard for children.
On the basis of its evaluation of available environmental information, ATSDR concluded that the exposure situations at EAFB pose no apparent public health hazard. Conclusions regarding medium- and site-specific exposures are as follows:
- No apparent public health hazards are associated with past exposures to arsenic in one on-base supply system well (well N-2). Exposures to on-base workers and residents contacting contaminants in drinking water were evaluated using conservative, site-specific exposure assumptions. No adverse health effects to adults or children are expected from past exposures. EAFB has discontinued use of the arsenic-contaminated well to prevent current or future exposures.
- On-base residents were not exposed to potential CWM contaminants in subsurface soil. EAFB has investigated the potential for exposure to possible CWM burial sites and found no evidence of CWM or CWM degradation products in any locations. No public health hazards are posed by CWM.
- No apparent public health hazards to on-base workers or residents are associated with exposures to dioxins in air from dual extraction remediation systems at Sites 16 and 18. Because of prevailing wind patterns in the area, exposures to workers and residents are expected to be of limited duration; dioxin levels are also lower than those that would be expected to produce adverse health effects.
All other on-base and off-base drinking water wells have been shown to be free of contamination. EAFB currently monitors active on-base wells and boundary-line monitoring wells regularly. These measures prevent current and future exposures to contaminants that could pose potential public health hazards.
The Public Health Action Plan (PHAP) for EAFB contains a description of actions taken and to be taken by ATSDR, EAFB, EPA, DTSC, and CADHS subsequent to the completion of this PHA. The purpose of the PHAP is to ensure that this PHA not only identifies potential and ongoing public health hazards, but provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. The public health actions that are completed, ongoing or planned, and recommended are listed below.
- EAFB identified potential hazardous substance release sites (grouped in 10 OUs) during base ERP investigations.
- Remedial actions to address soil and groundwater contamination have been completed at a number of sites within each of the OUs. Remedial actions have included UST removal, abandoned well capping, soil excavation and treatment, and groundwater treatment. Two hundred eighty-nine sites have been approved for "no further investigation" status (EAFB 2002a).
- CADHS and Kern County Health Departments provided updated information to residents near Edwards AFB regarding conclusions and efforts related to the Rosamond cancer cluster investigation.
- EAFB is conducting investigations and identifying potential remedial actions for sites in OUs 1, 2, 4, 5, 6, 7, 8, 9, and 10.
- EAFB is conducting ongoing remedial actions at sites within each OU. Ongoing remediation includes soil-vapor extraction systems, soil excavation and treatment, and innovative technologies.
- EAFB, EPA, and DTSC are working to develop RODs for each of the OUs by 2007.
- EAFB regularly monitors water supply wells to ensure that the drinking water supply is free of contamination at levels of health concern. Regular monitoring includes collecting samples quarterly, bi-annually, or annually from on-base supply systems and analyzing the samples for organic and inorganic compounds of potential concern.
- Members of the community and EAFB participate in regularly scheduled RAB meetings. These meetings serve as a forum for communication of ongoing and planned activities at EAFB to the community and for communication of community concerns to EAFB personnel.
- If changes in proposed land use, remedial activities, or risk management actions (e.g., institutional controls) might lead to future exposures or new information identifies contaminants in environmental media at Edwards AFB that exceed ATSDR health-based screening criteria, ATSDR will assess environmental sampling data and exposure situations as warranted to protect public health.
- DTSC and USACE will coordinate an appropriate response to community concerns about the potential for UXO presence in the area formerly used as the Mojave C Bombing Range.
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