PUBLIC HEALTH ASSESSMENT
JET PROPULSION LABORATORY (NASA)
PASADENA, LOS ANGELES COUNTY, CALIFORNIA
The National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) is located in Pasadena, California, northeast of Interstate 210. Established before World War II, the facility has been under the jurisdiction of NASA since 1958. Activities at JPL currently focus on automated exploration of the solar system and deep space. Under a contract with NASA, the California Institute of Technology operates JPL and maintains the facility. As a result of former site activities, chemicals, primarily volatile organic compounds (VOC) and perchlorate (a component of solid rocket fuel), used at JPL have been released to soil and groundwater.
The Agency for Toxic Substances and Disease Registry (ATSDR) conducted site visits in 1997 to assess the potential for public health hazards. During these visits, ATSDR identified two pathways where people could potentially be exposed to site-related contaminants: 1) exposure to contaminated groundwater and 2) exposure to contaminated soil. ATSDR also identified the following primary community concerns: 1) future groundwater and drinking water quality and 2) increased incidence of Hodgkin's disease. The evaluation of these potential pathways and community concerns is the focus of this Public Health Assessment.
Following a careful evaluation of available data, ATSDR determined that VOC-contaminated groundwater does not present a past, present, or future public health to JPL employees or nearby residents. On-site groundwater has never been used as a source of drinking water and area water purveyors, who are aware of the contamination problem in the water basin, regularly monitor their municipal water and take steps (e.g., well water blending, VOC treatment, or well closure) to ensure that the drinking water distributed to consumers is safe.
Since a new sensitive test for measuring perchlorate has become available, elevated levels have been detected in groundwater and in raw, unprocessed well water. As with the VOC, current sampling and well water blending procedures used by area water purveyors likely prevent harmful exposures to perchlorate. Insufficient data are available to estimate potential exposure to perchlorate in groundwater before 1997. However, based on the 1997-1999 perchlorate data, as well as data on groundwater flow, the migration patterns observed for other contaminants, and the protective measures taken by local water purveyors to ensure that VOC contaminants did not reach unsafe levels in finished drinking water, it is unlikely that perchlorate in groundwater posed a past public health hazard.
ATSDR also determined that exposure, if any, to contaminated soils associated with the JPL site and in the Arroyo Secco near the JPL boundary is unlikely to cause either short-term or long-term adverse health effects to employees and the public due to low contaminant levels, the depth of contamination, and/or infrequent or unlikely exposure.
Based on a review of the available information on groundwater and soil contamination, ATSDR concludes that JPL should be assigned to the No Apparent Public Health Hazard category for past, present, and potential future human exposure to VOC-contaminated groundwater processed for drinking water and surface soils or soil gasses. Even though it is unlikely that past human exposure to perchlorate in drinking water posed a public health threat, because the past levels of human exposure to perchlorate are unknown, ATSDR concludes that the site should be assigned to the Indeterminate Public Health Hazard category for potential past human exposures to perchlorate in drinking water.
The National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL) is located in Pasadena, California, northeast of Interstate 210. JPL consists of approximately 155 buildings on a 176-acre campus situated on a foothill ridge of the San Gabriel Mountains (see Figure 1). The facility is located within the boundaries of the cities of Pasadena and La Cañada-Flintridge; residential areas of these cities and the community of Altadena are within 1 to 3 miles of JPL. JPL is bordered to the north by the Angeles National Forest; to the east by the Arroyo Secco (an intermittent stream bed) and spreading grounds (a series of man-made basins used to percolate runoff water to replenish the aquifer); to the west by a residential neighborhood; and to the south by an equestrian club, a fire station, a U.S. Forest Service Ranger Station, and the Hahamonga Community Watershed Park (formerly known at Oak Grove Park). Also located south of the facility are several schools and the Devil's Gate Reservoir.
In 1936, a group of researchers began experimenting with rocket fuels in Pasadena's Arroyo Secco area. The group was soon enlisted to conduct research for the U.S. military, and in 1945 the group was designated the Jet Propulsion Laboratory, under the jurisdiction of the U.S. Army. In 1958, the facility was transferred to NASA and assigned a mission of research and development in aeronautics, space technology, and space transportation (JPL, 1991b).
The California Institute of Technology is currently under contract with NASA to perform research and development at JPL, as well as to manage the facilities. NASA maintains a presence at the facility in a supervisory role only. Primary activities at JPL currently include automated exploration of the solar system and deep space (including the Mars Pathfinder mission) and design and operation of the Deep Space Network that tracks spacecraft.
In performing these tasks, support facilities and research and development laboratories at JPL have used a variety of chemicals, including chlorinated solvents, solid rocket fuel propellants, cooling tower chemicals, sulfuric acid, Freon, mercury, and various laboratory chemicals. From 1945 to 1960, JPL disposed of liquid and solid wastes, including chemical wastes, in over 40 seepage pits and waste pits on the facility grounds (JPL, 1991a). It is believed that the seepage pits were backfilled between 1960 and 1963, when JPL installed a sewer system (Ebasco, 1990a, 1993). Since there is very little undeveloped land on the facility grounds, these disposal areas are now located under buildings, retaining walls, parking lots, roads, and flower planters. JPL now transports all of its hazardous wastes off site for destruction, disposal, or recycling.
In 1980, the city of Pasadena detected volatile organic compounds (VOCs)--carbon tetrachloride (CTC) and trichloroethylene (TCE)--in municipal wells located in and east of the Arroyo Secco spreading grounds southeast of JPL. VOCs were also detected at around the same time in two drinking water wells operated by the Lincoln Avenue Water Company, which primarily supplies the community of Altadena. Although the detected VOC concentrations initially did not exceed California drinking water standards (5 parts per billion [ppb] for CTC and TCE) the contaminant levels gradually rose so that the contamination in these wells was eventually above state standards (JPL, 1997a, 1994). These elevated contaminant concentrations forced the temporary closure of two Pasadena municipal wells in 1985, followed by the temporary closure of the two Lincoln Avenue wells in 1987, and finally the remaining two Pasadena wells in 1989 (JPL, 1994).
Because JPL is the major industrial establishment near these wells, it was suspected to be the source of the groundwater contamination. JPL and the city of Pasadena conducted preliminary assessment (PA) activities in 1982, 1984, 1986, and 1987 to identify the source(s) of contamination (JPL, 1991a).
In 1990, NASA funded the construction of a water treatment plant for the four contaminated Pasadena municipal wells. This allowed the city of Pasadena to resume production of drinking water from these wells. Also in 1990, JPL removed a suspected contaminant source area consisting of a storm drain and 160 cubic yards of soil and sludge (JPL, 1994). The Lincoln Avenue Water Company built a water treatment system in 1992, which allowed them to reopen the two closed drinking water wells.
In 1992, following an expanded site inspection (ESI) that identified CTC, TCE, and 1,1-dichloroethane (DCA), and to a lesser extent tetrachloroethylene (PCE), above drinking water standards in on-site groundwater (Ebasco, 1990a), JPL was placed on the U.S. Environmental Protection Agency's (EPA's) National Priorities List (NPL). Later that year (December 1992), EPA, the state of California, and JPL negotiated a Federal Facilities Agreement specifying how investigation and cleanup work at the site would be conducted.
During the site investigation process, JPL was divided into three operable units (OUs) to facilitate characterization of the sources, nature, and extent of contamination at and around the installation and to enable the proper design of cleanup measures. At each OU, JPL is conducting both a remedial investigation (RI) to identify and characterize the contamination and a feasibility study (FS) to determine the best methods of remediation. For OUs 1 and 3, JPL anticipates completing an RI report in early 1999, to be followed by an FS report. For OU2, JPL recently completed a draft RI (February 1999) and they continue to study treatment technologies for removing VOC vapors from soil (JPL, 1997a, 1998; Foster Wheeler, 1999). The following are descriptions of the OUs at JPL.
- OU 1: On-site groundwater. This OU addresses contaminated groundwater directly beneath the JPL site and the adjacent Arroyo Secco. RI/FS activities have included installation of 19 groundwater monitoring wells on JPL grounds and in the arroyo (Foster Wheeler, 1998a). By periodically monitoring the presence of contaminants in these wells, and performing computer modeling of groundwater movement, investigators will determine possible remedial actions. Current information about on-site groundwater contamination is summarized in Table 1.
- OU 2: On-site contamination sources. This OU encompasses all potential contaminant sources in soil at JPL. The majority of these sources are seepage pits where JPL allegedly disposed of liquid hazardous wastes before installing a sewer system in the early 1960s (connected to the Pasadena/Los Angeles sanitary sewer system). Other source areas include waste pits, stormwater discharge points, and chemical spill areas. Figure 2 is a three-dimensional model of JPL which shows the relationship of the contamination sources to nearby city of Pasadena drinking water wells. RI/FS activities at OU 2 have included soil-vapor probes, soil sampling, and/or installation of soil-vapor wells at suspected source areas. These activities help investigators characterize soil contamination and evaluate clean-up strategies. Current information about these on-site contamination sources is summarized in Table 1.
- OU 3: Off-site groundwater. This OU addresses any potential groundwater contamination detected in communities east of the Arroyo Secco. RI/FS activities have included installation of five groundwater monitoring wells in nearby Altadena and Pasadena (Foster Wheeler, 1998a). Monitoring these wells will help indicate whether contaminants have moved off site and determine the direction of movement and extent of contamination. Current information about all drinking water wells in the vicinity of JPL is summarized in Table 1.
In the summer of 1997, perchlorate, a chemical used in solid rocket fuel, was detected in monitoring wells at JPL and in some municipal wells near JPL. Perchlorate has become a contaminant of concern only recently, because until 1997 there was no laboratory test to detect low levels of perchlorate in water. Although there is a good deal of information about the health effects from short-term exposure to perchlorate, relatively little is currently known about the effects from long-term exposure (CDHS, 1997).
NASA, JPL, and other federal agencies are cooperating fully in joint industry, government, and academic efforts to develop a better understanding of the human health issues associated with perchlorate. In May 1997, a peer review panel of experts associated with the Toxicology Excellence for Risk Assessment convened to recommend and prioritize a set of studies to develop a better understanding of the long-term human health and ecological risks of perchlorate, address key data gaps, and reduce uncertainties in EPA's guidance levels. EPA's National Center for Environmental Assessment reviewed the data from these studies, and in September 1998, released its findings in an external review draft health risk assessment titled "Perchlorate Environmental Contamination: Toxicological Review and Risk Characterization Based on Emerging Information." The document, along with all new data and the study protocols, was subjected to an external expert peer review early in 1999 (EPA, 1999).
Until new information about perchlorate becomes available, the Agency for Toxic Substances and Disease Registry (ATSDR) is unable to fully evaluate any potential public health hazards related to perchlorate at JPL. ATSDR will evaluate these new data as they become available, and will use any and all new information to further assess the perchlorate contamination at JPL. A summary of current information about perchlorate and its occurrence at JPL is presented in Appendix C.
JPL has a work force of approximately 8,000 people (6,000 employees and 2,000 contractors). Approximately 30 percent of JPL employees come from Pasadena, 7 percent from Altadena, and 7 percent from La Cañada- Flintridge (JPL, 1994). There are no residents on the JPL property.
Population data, housing data, and a census tract map of the JPL area are presented in Appendix D. The total population residing in the vicinity of JPL includes:
- 9,500 people within 1 mile of the site
- 17,000 people within 2 miles of the site
- 20,000 people within 3 miles of the site
The city of Pasadena borders JPL to the south and southeast and has primarily residential, office, retail, and service areas. From 1980 to 1990, the population of Pasadena grew 9.7 percent to 131,591 (JPL, 1994).
Altadena borders JPL to the east. Altadena has residential as well as office, retail, and service areas, but Altadena residents are generally employed outside their home community. From 1980 to 1990, Altadena's population rose 3.9 percent to 42,658 (JPL, 1994).
Bordering JPL to the west is La Cañada-Flintridge. Most residents commute outside of La Cañada-Flintridge to work. From 1980 to 1990, the population declined 2.9 percent to 19,578 (JPL, 1994).
JPL is an active research and development facility that performs light industrial activities. The perimeter of the facility is surrounded by an 8-foot high chain link fence with motion detectors; access to the facility is controlled at all times (JPL, 1994). Adjacent areas to the east and west of the facility, except for Arroyo Secco, are primarily residential; the adjacent Arroyo Secco area to the east and south includes a reservoir, park, ranger station, fire station, and equestrian club; directly north of the facility are the San Gabriel Mountains and the Angeles National Forest.
Groundwater beneath JPL has never been pumped for use as drinking water (JPL, 1997e). Employees at JPL receive public drinking water from the city of Pasadena. Pasadena currently pumps groundwater from three Raymond Basin wells, blends and treats the "raw"water from the wells at the Devils Gate Groundwater Treatment Facility, and then sends the water to the Windsor Reservoir before delivering the "finished" -- treated and blended--drinking water to area customers.(1) In addition to groundwater sources, about 60 percent of the city of Pasadena's water supply comes from the Metropolitan Water District of Southern California (MWDSC). The MWDSC's imported water supplies are from northern California via the California Water Project and its supply from the Colorado River (Raymond Basin, 1998b).
JPL is situated on an alluvial fan formed by sediments that washed down from higher ground in the San Gabriel Mountains. The facility is located in the Monk Hill Sub-Basin of the Raymond Basin, an aquifer covering approximately 40 square miles which is replenished by water flows from the San Gabriel Mountains, including the Arroyo. The Raymond Basin is an important source of drinking water for many communities in the area including Alhambra, Altadena, Arcadia, La Cañada-Flintridge, Pasadena, San Marino, and Sierra Madre. Sixteen water purveyors, who are each allowed to pump a certain amount of water per year, supply groundwater from the Raymond Basin to the public. In 1944 the Superior Court of California approved the Raymond Basin Judgement, which adjudicated the rights to groundwater production to preserve the safe yield of the groundwater basin (Raymond Basin, 1998b). Under authority of a 1984 court order, the Raymond Basin Management Board, made up of representatives of the water purveyors, oversees the management and protection of the Raymond Basin (Raymond Basin, 1997a, 1997b). A total of six Raymond Basin water purveyors operate wells within 4 miles of JPL. The closest--within 2,500 feet of JPL--are four drinking water wells, directly east of the Arroyo Secco, that are operated by the city of Pasadena. Other nearby municipal wells are located in Altadena, La Cañada-Flintridge, and Pasadena (locations of nearby drinking water wells and monitoring wells are shown in Figure 3).
The climate in Pasadena is semiarid and is characterized by hot, dry summers and mild winters with intermittent rain. The average annual precipitation in the area is 22.5 inches. The local aquifer is recharged by both natural infiltration of precipitation and artificial recharge from spreading grounds located on the eastern edge of the Arroyo Secco. The spreading basins and the Arroyo Secco are used for flood control during rainy months (December to March), when the intermittent stream running through the arroyo reaches its highest levels. The arroyo drains into the Devil's Gate Reservoir located 1 mile south of JPL. The reservoir is formed by the Devil's Gate Dam, which is situated at the southern edge of the reservoir by Interstate 210. The level of the reservoir fluctuates during the year, with little or no standing water present during dry seasons. During major floods, water has risen over portions of Hahamonga Community Watershed Park to the west and the spreading basins to the east. The Devil's Gate Dam and Reservoir has undergone renovations that should result in a several-acre-large permanent pond. The level of this pond will be raised and lowered throughout the year to maintain proper flow downstream of the dam. There are no other lakes, ponds, or wetlands in the vicinity of JPL.
ATSDR conducted initial site visits at JPL on August 12 and August 20, 1997, to meet with JPL environmental personnel and state public health and environmental officials and to gather information pertinent to the preparation of a public health assessment (PHA) for this site. On December 2 and 3, 1997, ATSDR conducted another site visit to collect further information for the PHA and held four public availability sessions near JPL to provide community members an opportunity to ask questions and voice their concerns regarding public health issues at JPL. Those public availability sessions were announced in a November 19, 1997 ATSDR-issued press release. sent to major and local news media of the Los Angeles-Pasadena area. Eleven community members attended and expressed concerns. ATSDR addresses their concerns in the "Community Health Concerns" section of this PHA.
On August 4, 1998 ATSDR release the Jet Propulsion Laboratory Public Health Assessment (PHA) for public review and comment. That public comment period ended September 20, 1998. During that period ATSDR received comments or questions from six individuals and two organizations or agencies. Subsequently, ATSDR met with two individuals to obtain clarification on their concerns.
In preparing this public health assessment (PHA), ATSDR relied on the information provided in the referenced documents and from the referenced contacts. ATSDR assumes that adequate quality assurance and control measures were followed with chain-of-custody, laboratory procedures, and data reporting. The validity of the analyses and conclusions drawn in this document are dependent on the availability and reliability of the referenced information.
In this section, ATSDR evaluates whether a public health hazard exists for people who live near or access the JPL site. In evaluating health hazards, ATSDR first tries to establish whether individuals could have been (past), are (present), or could be (future) exposed to chemicals originating from the JPL site. ATSDR does this by carefully evaluating the elements of an exposure pathway that might lead to human exposure. These elements, include a source of contamination, an environmental medium (such as soil, water, or air) in which contaminants may be present, a point of human exposure, a route of human exposure (such as ingestion, inhalation, or skin contact), and a receptor population (such as nearby residents). Figure 4 explains the exposure evaluation process in more detail.
ATSDR identifies exposure pathways as completed or potential. A completed exposure pathway exists in the past, present, or future if all elements of the exposure pathway are present and if the receptor population has been, is, or will be exposed to the contaminants in sufficient concentration and/or duration that adverse health effects could result. Potential pathways, however, are defined as situations in which at least one of the pathway elements is missing, but could exist.
If exposure was or is possible, ATSDR considers whether chemicals were or are present at levels that might be harmful to people. ATSDR does this by screening the concentrations of contaminants in an environmental medium against health-based comparison values. Comparison values are chemical concentrations that health scientists have determined are not likely to cause adverse effects, even when assuming very conservative exposure scenarios designed to be protective of public health. Because comparison values are not thresholds of toxicity, environmental levels of contaminants that exceed comparison values would not necessarily produce adverse health effects. If a chemical is found in the environment at levels exceeding its corresponding comparison value, ATSDR examines the duration of potential exposure variables and the toxicology of the contaminant. Through examination of both the level and duration of exposure to contaminants ATSDR makes a determination on the potential public health hazard that may arise from exposure to contaminated environmental media.
ATSDR's evaluation of potential public health hazards associated with areas of concern at JPL is summarized in Table 1. Except for the completed and potential exposure pathways for groundwater and soil, other pathways are not associated with any known public health hazards because: 1) no site-related contamination is present, 2) contaminant concentrations detected are too low to pose health hazards, and/or 3) exposure to the general public has been prevented. ATSDR summarizes its evaluation of the completed and/or potential groundwater and soil exposure pathways in Table 2 and describes it in more detail in the discussion that follows. To acquaint readers with terminology used in this report, a glossary and comparison values list are included in Appendices A and B, respectively.
Has groundwater contamination from the JPL site resulted in municipal drinking water that is unsafe for local residents or JPL employees to drink?
- Groundwater at JPL has not affected the health of facility employees because on-site groundwater has never been used for drinking water.
- Off-site groundwater with VOC contamination does not pose a past or present public health hazard. Although VOCs were found in groundwater monitoring wells and in raw water of nearby public supply wells, area water purveyors have taken and continue to take measures (e.g., well water blending, water treatment, or well closure) that improve the quality of finished drinking water delivered to the public. Furthermore, as required by the California Department of Health Services, water purveyors regularly monitor drinking water for VOCs to ensure that it meets safe drinking water standards.
- Off-site groundwater with VOC contamination is not expected to pose a future public health hazard. Area water purveyors are aware of the contamination in the water basin and will continue to monitor, blend, and treat water to safe levels. If contaminant levels continue to rise in the water basin, however, water purveyors may need to take additional measures to preserve the quality of drinking water, including closing more wells, building more treatment systems, increasing their treatment capacities, and/or buying imported water.
- Perchlorate contamination in off-site groundwater presents no apparent present or future public health hazard. The current sampling and well water blending procedures used by the drinking water purveyors near JPL help to prevent any potential present or future public health hazards posed by perchlorate in groundwater. Past exposures to perchlorate contamination present an indeterminate public health hazard because there are no data on perchlorate levels before 1997. Based on the available data, however, it is unlikely that past perchlorate levels in groundwater posed a public health hazard.
As discussed in "Land Uses and Natural Resources," JPL is situated in the Raymond Basin aquifer, which is a significant source of drinking water for many nearby communities. Groundwater has been encountered in monitoring wells at JPL at depths of 100 to 240 feet below ground surface. Groundwater flows predominantly south and southeast from JPL toward the Arroyo Secco, although the direction can change, and even reverse for short periods of time, depending on seasonal variations, pumping rates of the various supply wells in the area, and the quantity of infiltration of surface runoff water in the Arroyo Secco basins (Ebasco, 1993). Groundwater elevations at JPL are generally lower between July and December and higher between January and June.
Thrust faults in the vicinity of JPL include the Mount Lukens Thrust Fault, the south branch of the San Gabriel Thrust Fault, and the JPL Thrust Fault. These faults comprise part of the Sierra Madre Fault system that separates the San Gabriel Mountains from the Raymond Basin. The JPL Thrust Fault runs along the hillside at the uphill edge of the JPL campus, and creates an uplifted, or perched, aquifer that is separate from the larger regional aquifer (Ebasco, 1993).
Groundwater Quality and Sources of Contamination
Through the RI and previous investigations, JPL has installed a total of 19 monitoring wells on site and in the adjacent Arroyo Secco to characterize contaminant concentrations in groundwater beneath source areas of the site, and to track contaminant movement (see Figure 3). There are a number of suspected contaminant source areas at JPL. Some of the source areas include seepage pits, waste pits, stormwater discharge points, and spill areas where hazardous waste may have been released indirectly to groundwater through the soil.
Many of these monitoring wells have screens at several different depths in the aquifer to provide information about the three-dimensional distribution of contaminants beneath JPL. Since August 1996, JPL has sampled its monitoring wells quarterly and analyzed the samples for VOCs and metals; JPL now analyzes these quarterly samples for perchlorate, as well (Foster Wheeler, 1997a, 1997b).
As part of the RI/FS, JPL has also installed five off-site monitoring wells to the south and east of the facility, in Altadena, Pasadena, and the Hahamonga Community Watershed Park (see Figure 3). These wells will help identify groundwater contamination that may have migrated from JPL and determine the horizontal and vertical extent of contamination. JPL also samples these wells quarterly.
The available data indicate that JPL is a source of VOC and perchlorate contamination in both on-site and off-site groundwater. Of the contaminants detected on site, TCE, CTC, 1,2-DCA, and perchlorate were detected most frequently and at concentrations above California maximum contaminant levels (MCLs) or action levels. The highest concentrations of these chemicals were found in the north-central portion of the site, just downgradient from the Liquid and Solid Propellant Laboratory and the Assembly Handling and Equipment and Shipping Facility.
Much lower concentrations of VOCs and perchlorate have migrated off site. Following the current direction of groundwater flow (southeastward), CTC, TCE, and perchlorate plumes have migrated approximately 2,500 feet downgradient toward the city of Pasadena and Lincoln Avenue Company production wells. (1,2-DCA has not been observed at any off-site well over the course of the RI groundwater monitoring.) While the highest levels of these VOCs were largely found in the upper layer of the aquifer, lower levels (0.5 to 5 ppb) had extended vertically to the deeper aquifer and laterally to the city of Pasadena wells. Concentrations and direction of contaminant flow can fluctuate in response to pumping of wells and seasonal variations in groundwater elevations. Since 1996, however, the shapes of the plumes have stayed relatively stable, suggesting that widespread or higher levels of contaminants are not traveling further downgradient and in the direction of public water supply wells (Foster Wheeler, 1998a).
Groundwater investigations performed by JPL indicate that VOC concentrations beneath JPL vary seasonally and may indicate the presence of an off-site sources in addition to on-site sources (JPL, 1997b). One such potential source of contamination is associated with the use of septic systems in La Cañada-Flintridge, an area without sewers. According to JPL and the Valley Water Company, citizens in these areas have often cleaned their plumbing pipes by pouring solvent down their drains (JPL, 1997a; Raymond Basin, 1997a).
The groundwater investigation conducted by JPL of Operable Units 1 and 3: on-site and off-site groundwater (Foster Wheeler, 1999) developed additional information on the configuration of the contaminated groundwater plumes and the distribution of contaminants within those plumes. Although not conclusive, the evidence gathered strongly suggests that potential additional sources of groundwater contamination lie upgradient to the west, in the direction of the Valley Water Company wells. Because VOCs are used in a wide variety of commercial application, many potential sources exist upgradient for those compounds. The injection of imported Colorado River water for aquifer recharge by Valley Water Company may be the source of additional perchlorate contamination detected in local municipal wells. The source of the perchlorate contamination (recently detected at levels as high as 16 ppb) in the water of the Colorado River may be traced to two sites near Henderson, Nevada associated with the manufacture of ammonium perchlorate.
Drinking Water Use and Quality
Located within 4 miles of JPL are drinking water wells operated by six water purveyors (municipal wells are shown in Figure 4). To the west there are four wells operated by the Valley Water Company and one well operated by the La Cañada Irrigation District. To the east and southeast there are four wells owned by the city of Pasadena, of which three are currently used; two wells operated by the Lincoln Avenue Water Company; two wells operated by the Rubio Canyon Land and Water Company; and one well operated by the Los Flores Water Company. Table 3 summarizes raw well water monitoring data for chemicals that exceed comparison values for each of these drinking water sources. It should be noted that raw water is pretreated and unblended water in the municipal wells. Raw water is processed before it is delivered to area consumers as finished water for drinking and other domestic uses. By such processes as blending with other water sources and effectively treating the water, area water purveyors are able to dilute and/or remove chemicals that may have been present in raw water.
The following discussion describes water quality information maintained by water purveyors about their systems.
Volatile Organic Compounds
VOC contamination has been detected in the raw water of wells belonging to three water purveyors located adjacent to JPL: the city of Pasadena and the Lincoln Avenue Water Company, to the east of JPL; and Valley Water Company, to the west. At various times the concentrations of TCE and CTC in the raw water drawn from some of these wells have exceeded drinking water standards and the purveyors have temporarily shut down some drinking water wells. As Table 3 indicates, some of the highest levels of CTC and TCE were found in raw water from the city of Pasadena's Arroyo well, located about 2,500 feet downgradient from and the closest to the site. The Arroyo well has been closed since June/July 1997 (City of Pasadena, 1999). PCE is also present in Valley Water Company wells (JPL, 1997d; Raymond Basin, 1997a), but the small amounts of PCE found at JPL makes it an unlikely source of the well water contamination. It should be noted that VOCs have not been detected or have not exceeded standards in raw water in municipal wells located farther away from JPL (La Cañada Irrigation District, Rubio Canyon Land and Water Company, and Los Flores Water Company) (JPL, 1997d; La Cañada, 1998; Rubio Canyon, 1998; Los Flores, 1998).
The California Department of Health Services (CDHS) sets and oversees sampling schedules for water purveyors in the area and throughout California to ensure that VOCs (and other chemicals) are adequately monitored. Through its Domestic Water Quality and Monitoring Regulations (Chapter 15, Title 22, California Code of Regulations), CDHS specifically requires a water purveyor to perform VOC sampling of raw water and submit the results to CDHS (Raymond Basin, 1998a). A water purveyor may need to adjust the water monitoring schedule as VOC concentrations in the wells change. The scheduled sampling for VOCs is as follows:
- Sample before beginning water distribution operations.
- Sample every three years unless or until VOCs are detected.
- Sample quarterly once VOCs have been detected, unless or until the contaminant concentrations exceed the drinking water standard. The water purveyor is required to take steps to reduce the contaminant concentration or shut down the contaminated well. If this occurs the water purveyor must also inform its customers about the detected contamination.
- On a case-by-case basis, sample finished water if detections in raw water exceed drinking water standards. This sampling is usually required monthly.
Area water purveyors are aware of the contamination problem in the water basin, but they have taken several measures to help safeguard against unacceptable levels passing through the system and reaching area consumers. These measures include:
- Treat water to remove VOCs. Each of the water purveyors now operates some type of water treatment system (e.g., air stripping or activated carbon filtering) to remove VOCs.
- Blend water from all wells. Since the VOC levels vary among their drinking water wells, some water purveyors are often able to blend well water from different wells to reduce the overall VOC concentrations to below drinking water standards. (Table 4 summaries the wells used by each of the area water purveyors.) For example, Pasadena has pooled raw water from the Arroyo well (1930) with water from the Windsor well (1918) and the Ventura well (1924), and later with Well 52 (1977). Water from these other wells has historically shown lower levels of contaminants, if any, than raw water drawn from the Arroyo well.
- Blend well water with imported water. The purveyors also have the option of blending their well water with imported water to augment their drinking water supplies. Table 4 presents information on the percent of imported water used by each water purveyor. As the table indicates, the city of Pasadena draws as much as 60 percent, the Lincoln Avenue Water Company draws as much as 20 percent, and the Valley Water Company draws as much as 75 percent from imported water sources.(2) Blending well water with imported water enables the water purveyors to dilute chemicals, if present, and deliver safe drinking water to their customers. For example, by blending well water containing PCE (even up to 17 ppb) with water imported from the MWDSC, the Valley Water Company has met safe drinking water standards.
Together these processes would be expected to greatly dilute VOC concentrations measured in raw water. Additional reduction of VOCs in the water is likely to occur when VOCs are released or volatilized--that is, converted from a liquid into a vapor--as the water flows through the distribution system.
The presence of perchlorate in groundwater did not become a concern until a sensitive test to detect perchlorate was introduced in early 1997. Since then, CDHS has recommended that water purveyors and responsible parties at hazardous waste sites analyze groundwater for perchlorate using the new test method. CDHS has set a conservative provisional drinking water standard (called an "action level") of 18 ppb. Perchlorate has been detected above the action level in the Pasadena drinking water well located closest to JPL (the Arroyo Well, shown in Figure 3). Perchlorate has been detected at much higher levels (maximum detection=1,230 ppb) in monitoring wells at JPL (Foster Wheeler, 1997b; Foster Wheeler, 1998a). The city of Pasadena closed the affected drinking water well as a result of the perchlorate detection. Perchlorate levels subsequently rose above the action level in the next Pasadena well downgradient to JPL (Well No. 52, see Figure 3). By blending the water from this well with water from the remaining drinking water wells, Pasadena has been able to avoid shutting down Well No. 52 while still providing finished water that is below the action level for perchlorate (City of Pasadena, 1998). Perchlorate has been detected below the action level in the other two Pasadena drinking water wells and in the wells of other nearby water purveyors. (See Table 3 and Appendix C for a summary of available information on perchlorate and its occurrence at and near JPL.)
Perchlorate levels in and around JPL before 1997 are unknown. Several factors suggest, however, that high levels of contamination may have never reached residential taps.
- The hydrogeologic and contaminant data given in the groundwater RI (Foster Wheeler, 1999b) and the results of the quarterly groundwater monitoring indicate that the operation of the Arroyo well has exerted considerable influence on groundwater flow in the area; drawing contaminants towards that well and limiting the spread of contaminants elsewhere.
- The rise in perchlorate levels in nearby Pasadena Well #52 began after pumping of the Arroyo well had ceased, suggesting that perchlorate levels were actually lower in other Pasadena of Lincoln Water wells in the past.
- The Arroyo well had perchlorate levels above the action level when perchlorate analysis began, but since the other three Pasadena wells did not, blended water from all four wells probably did not exceed the action level. The Arroyo well has not been used since June/July 1997.
- The action level for perchlorate is considerably lower than levels shown to cause harmful effects in available studies of communities, workers, and laboratory animals.
Exposure Pathway Evaluation
VOCs and perchlorate have been detected in groundwater monitoring wells on and near JPL and in raw water of nearby drinking water wells operated by Pasadena, Lincoln Avenue Water Company, Valley Water Company, Rubio Canyon, and Los Flores, but it is unlikely that people were exposed to harmful levels of contaminants when they drank water. Even though water testing data are not available for all years to fully evaluate the likelihood of past exposure, several factors suggest that unsafe levels of chemicals never reached finished drinking water supplies. First, no drinking water wells exist at the JPL facility where the highest levels of contamination exist, and employees have received their drinking water from public water sources. Second, when contaminants have been detected during periodic sampling of the raw groundwater supply, that water has been treated and tested to ensure its safety as drinking water before it is distributed to area customers.
Some people who lived near the JPL facility continue to be concerned about health problems and their relation to contaminants detected in raw well water. To determine if potential health hazards could have existed, ATSDR conservatively estimated exposure doses for an adult and a child assuming that they drank raw water from the affected public wells. Note that this is a highly conservative and unlikely scenario that greatly overestimates possible health risks associated with drinking finished water because no one drinks the raw, untreated or blended groundwater. Actual concentrations, if any, in the finished drinking water would have been much lower than the maximum detected concentrations noted in raw water. This maximum-exposure, hypothetical example is intended to determine whether adverse health effects might arise if exposure occurred at these high levels.
In estimating exposure, ATSDR derived human exposure doses using conservative assumptions about the frequency and duration of potential exposure. ATSDR assumed that a typical adult drank 2 liters of water each day and weighed 70 kilograms and that a child drank 1 liter of water each day and weighed 16 kilograms. Because it is not known when migrating chemicals first reached the wells, ATSDR used an exposure period of 50 years for adults (to consider the years roughly between JPL start up  and well closure [1985 to 1987]) and 6 years for children to calculate a maximum exposure dose. ATSDR also assumed that the drinking water contained the maximum concentrations of VOCs or perchlorate detected at any one well before the well was closed. Furthermore, ATSDR assumed that 100 percent of the water used for drinking came from the raw water of the affected well. These are conservative assumptions about exposure, since most consumers probably drank water from other sources and were probably exposed to much lower concentrations, if any, over the course of a life time.
ATSDR compared the estimated doses with available health guidelines (such as ATSDR's minimal risk levels and EPA's reference doses), cancer guidelines, and with data from available toxicologic studies. (The health guidelines provide a conservative estimate of daily exposures to a chemical that are not likely to result in adverse effects, even for the most sensitive members of a community [e.g., pregnant women, children]). In its analysis, ATSDR found that, even when assuming an individual drank the raw water containing the highest chemical concentrations, the estimated doses are less than or just slightly above the corresponding health guidelines and often many times lower than adverse effect levels reported in medical literature for daily lifetime ingestion of these chemicals. For this reason, ATSDR finds that drinking water in the past, or using it in the home, probably did not harm consumers' health, or increase their risk of cancer. However, because there is no information on past perchlorate levels, ATSDR has assigned past exposures to perchlorate in off-site groundwater as an indeterminate public health hazard.
Current and Future Exposures
No exposure to harmful levels of contaminants found in groundwater is occurring now nor is likely to occur in the future. As mentioned above, the groundwater beneath the site is not used for drinking water and water purveyors continue to monitor, blend, and treat well water to remove contamination from raw water, if present, before distributing the finished drinking water to the consumer. If contamination is routinely detected in wells in the future, the water purveyor is required to close the well.
Perchlorate has been detected above the CDHS action level in two Pasadena drinking water wells. By closing one well, the Arroyo well, and blending water from the second well with the remaining drinking water wells, Pasadena is producing finished water that is below the action level for perchlorate (City of Pasadena, 1998). Perchlorate has been detected below the action level in numerous other drinking water wells near JPL. CDHS requires regular sampling of drinking water wells where perchlorate concentrations are of potential concern. This regular sampling, together with water blending or well closures (when necessary), now ensures that all water distributed to consumers meets California's action level for perchlorate. ATSDR believes that these actions will continue to eliminate any potential public health hazard posed by exposure to perchlorate in groundwater near JPL.
Could exposure to soil contamination at JPL result in adverse human health effects?
No public health hazards are associated with exposure to contaminated soils at JPL. Contaminants in on- and off-site (in the Arroyo Secco near the JPL boundary) soils were detected at levels that pose no public health hazard and were inaccessible to JPL workers or the public because of their depth below the ground's surface or were located where exposure was infrequent or unlikely. VOC vapors were detected in relatively shallow soil in the area of Building 107, but indoor air quality sampling in this building detected no VOC vapors.
Extent and Sources of Soil Contamination
The pre-RI and RI activities for OU 2 have involved measurement of soil gas through probes and wells and collection of subsurface soil samples from over 40 suspected contaminant source areas at JPL and nearby in the Arroyo Secco (Ebasco, 1993; Foster Wheeler, 1997c). Information on these sources is summarized in Table 1. Samples of surface soil (0 to 6 inches deep) generally were not collected at JPL, because most of the suspected source areas are buried beneath pavement, buildings, retaining walls, or flower planters (Foster Wheeler, 1998b). At areas that are exposed at the surface (e.g., the stormwater discharge points), soil sampling began at depths of 1 foot or more. For these areas, ATSDR considered the shallowest samples to be representative of surface soil. Subsurface soil sampling has detected no contamination at levels above health-based comparison values (CVs). Soil-gas sampling has detected areas of soil contamination:
- VOC vapors were detected above CVs for air in numerous soil-vapor probes and monitoring wells at JPL. Most of the detections that exceeded CVs were at depths of 80 to 200 feet below ground surface. CTC was detected above its CV at depths of 11 to 13 feet in soil-vapor probes 31 and 33, which were taken at two locations near Building 107.
Exposure Pathway Evaluation
The majority of suspected contaminant source areas at JPL are located beneath pavement, buildings, retaining walls, and flower planters and are not accessible to JPL employees (the types of cover over each source area are specified in Table 1). In addition, soil sampling has detected no contaminants at concentrations above CVs, although soil-gas sampling has detected VOC vapors above CVs. Although workers could be exposed to currently inaccessible subsurface soils during future excavation, demolition, or construction work, ATSDR assumes that these workers will wear proper protective equipment in accordance with the Occupational Safety and Health Administration (OSHA) regulations.
VOCs were detected above CVs for air in numerous soil-vapor probes and soil-vapor well samples. The majority of these detections were at depths of 80 to 200 feet and are not expected to pose a public health hazard to JPL workers. CTC vapors were detected above CVs at depths of 11 to 13 feet in soil-vapor probes 31 and 33, located directly south of Building 107. VOC vapors in soil at relatively shallow depths have the potential to collect in the lower levels of buildings, where they can pose a public health hazard. Soil-vapor measurements from soil-vapor probes are not necessarily indicative of VOC concentrations in the air at a nearby building, but they can indicate areas where indoor air sampling might be required. In response to ATSDR concerns about potential VOC vapors in indoor air, JPL performed indoor air quality sampling at Building 107. This sampling indicated that VOC vapors were not present in the building.
Community health concerns have been brought to ATSDR's attention through the PHA process at the JPL site. In 1994, JPL prepared a Superfund Community Relations Plan that details community concerns and develops goals and objectives to better understand the needs of the surrounding community. The plan summarizes the results of two rounds of interviews, conducted in 1991 and 1993, with a total of 43 members of the surrounding communities. Through these interviews, JPL found that overall awareness of environmental problems at the facility was low (JPL, 1994). Nevertheless, interviewees did express concerns regarding groundwater and drinking water quality, current hazardous waste disposal practices. Since these interviews, JPL has conducted remedial investigation activities at the facility and the surrounding communities that address these health and environmental concerns. ATSDR has thoroughly reviewed all available documents from these activities and addresses the communities concerns in the "Evaluation of Potential Pathways of Exposure" section of this PHA.
As previously mentioned, ATSDR conducted four public availability sessions between December 2 and 3, 1997. The following are other specific concerns expressed by community members at these meetings regarding contamination and health effects associated with the JPL site.
- Concern about future groundwater and drinking water quality.
Water purveyors surrounding JPL are aware of the contamination problem in their water basin. Currently, they are able to provide, through treatment and well water blending, drinking water that meets regulatory standards. ATSDR acknowledges, however, that with a rise in contaminant levels (especially for perchlorate), purveyors might need costly treatment systems, system upgrades, or drinking water well closures to continue to provide safe water to their customers. They may also need to then replace their lost groundwater capacity with imported water.
If contaminant levels continue to rise appropriate remedial measures may be required to maintain safe drinking water sources. JPL is currently considering remedial options that would reduce or remove contamination from the area groundwater. Under consideration is a laboratory bench scale study of removing perchlorate via ion exchange. Until more is known about the human toxicology of perchlorate (e.g., from the expert peer review) and until such time effective technologies or strategies are identified, however, ATSDR suggests that the best approach to ensuring the availability of a safe source of water is through frequent monitoring of any potentially affected well.
- Concern about a perceived increase incidence of Hodgkin's disease in communities surrounding JPL.
ATSDR is not aware of any studies that suggest an elevated rate of Hodgkins' disease exists in the community around JPL. Information available about Hodgkin's disease suggests that it is an uncommon malignancy of the lymphoreticular system that occurs most frequently in young adults (Rothman and Freed, 1989). Most researchers agree that the likely cause of Hodgkin's disease is an infectious agent--a virus in particular; however, neither the virus, nor the cell of origin of the disease have been identified (Michels, 1995).(3) The Epstein-Barr virus has been found at higher levels in individuals with Hodgkin's disease, and is a suspected agent (Herbst et al., 1990; Mueller et al., 1989); however, research suggests that the virus is probably a co-factor and not the single causative agent (Michels, 1995).
While the origin of the disease is likely infectious, socioeconomic and genetic factors also play a role (Rothman and Freed, 1989). The higher the socioeconomic status, the higher the risk of Hodgkin's disease in young adults. Socioeconomic factors (e.g., high maternal education, single facility housing and small family size have been associated with HD in young adults (15 to 39 years), but not in older patients (Gutensohn et al., 1982; Glaser, 1987; Bonelli et al., 1990; Chen et al., 1997). In addition, Hodgkin's disease patients generally had fewer childhood infectious diseases, or had them later in life (Grufferman and Delzell, 1984). Ethnic variation in the disease suggests that a genetic predisposition plays a role (Stiller, 1998). There is a familial link to the disease; however, while siblings of younger adults are at higher risk of contracting Hodgkin's disease, siblings of older adults are not. This suggests an interaction between "environment" and genetic factors (Grufferman and Delzell, 1984).
Although medical researchers suspect that environmental factors may influence whether an individual contracts Hodgkin's disease, no specific environmental agents have been linked to the disease. Some studies have noted a higher than average rate of Hodgkin's disease in worker populations exposed to organic solvents; however, researchers were not able to identify which particular solvent may have been linked to the increased rate of disease (Hardell et al., 1981; Olsson and Brandt, 1980; Swaen et al., 1996). This is because workers are often exposed to multiple chemicals over the course of their work experience. Perchlorate has been potentially associated with cancer of the follicular thyroid cells (EPA, 1999), but it has not been associated with Hodgkin's disease. Similarly, no studies have associated TCE with Hodgkin's disease.
ATSDR recognizes that infants and children may be more sensitive to exposures than adults in communities with contamination of their water, soil, air, or food. This sensitivity is a result of the following factors: Children are more likely to be exposed to soil or surface water contamination because they play outdoors and often bring food into contaminated areas. For example, children may come into contact with and ingest soil particles at higher rates than do adults; also, some children with a behavior trait known as "pica" are more likely than others to ingest soil and other nonfood items. Children are shorter than adults, which means they can breathe dust, soil, and any vapors close to the ground. Also, they are smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Because children depend completely on adults for risk identification and management decisions, ATSDR is committed to evaluating their special interests at sites such as JPL.
ATSDR has attempted to identify populations of children in the vicinity of JPL and any completed exposure pathways to these children. Children are not regularly or normally present at JPL, although children of JPL employees may visit JPL on occasion. JPL offers a day care service for its employees at a facility located southeast of JPL near La Cañada High School. The following schools are located within one mile southeast of JPL: Flintridge School for Boys, St. Bede School, St. Francis High School, Oak Grove School, and La Cañada High School. Located within one mile east or southeast of JPL are Mt. Lowe Academy, Audubon School, Sacred Heart School, Franklin School, and Five Acres School. These schools are shown in Figure 1. Roughly 1,500 children under the age of ten are estimated to live within 1 mile of JPL. ATSDR did not identify any completed exposure pathways from JPL that are specific to children at nearby schools or residential areas. Like all other people living or working in the vicinity of JPL, children ingest drinking water--supplied by local water purveyors--that has, at least in part, been pumped from aquifers near JPL. This potential groundwater exposure pathway is discussed extensively in "Environmental Contamination and Potential Pathways of Exposure."
Based on an evaluation of available environmental information, ATSDR has reached the following conclusions:
- On-site groundwater at JPL does not present a past, present, or future public health hazard because on-site groundwater has never been used for drinking and there are no plans to use this groundwater in the future.
- VOC contamination in off-site groundwater does not present a past, present, or future public health hazard because water purveyors, under the supervision of CDHS, have regularly monitored drinking water wells and taken steps (e.g., water blending, water treatment, or well closure) to ensure that the "finished" drinking water distributed to consumers is safe. These actions will continue to prevent exposures to contaminated groundwater in the future.
- Perchlorate contamination in off-site groundwater presents no apparent present or future public health hazard. The current sampling and well water blending procedures used by the drinking water purveyors near JPL are expected to prevent any potential present or future public health hazards posed by perchlorate in groundwater. Past exposures to perchlorate contamination present an indeterminate public health hazard because there are no data on perchlorate levels before 1997. Based on the available data, however, it is unlikely that past perchlorate levels in groundwater have posed a public health hazard.
- Further degradation of groundwater quality could force water purveyors to build new treatment systems, increase their treatment capacities, and/or buy imported water.
- No public health hazards are associated with exposure to contaminated soils at JPL. Contaminants in on- and off-site (in the Arroyo Secco near the JPL boundary) soils were detected at levels that pose no public health hazard and were inaccessible to JPL workers or the public because of their depth below the ground's surface or were located where exposure was infrequent or unlikely. VOC vapors were detected in relatively shallow soil in the area of Building 107, but indoor air quality sampling in this building detected no VOC vapors.
- Community members expressed concern about a perceived increased incidence of Hodgkin's disease in communities surrounding JPL. Most researchers agree that the likely cause of Hodgkin's disease is an infectious agent. No studies to date have associated perchlorate or TCE with Hodgkin's disease, two primary contaminants of concern at JPL.
The public health action plan (PHAP) for JPL contains a description of actions taken and those to be taken by ATSDR, JPL, EPA, and CDHS at and in the vicinity of JPL after the completion of this PHA. The purpose of the PHAP is to ensure that this PHA not only identifies ongoing and potential 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, being implemented, planned, or recommended are as follows:
- JPL and the city of Pasadena installed a treatment system in 1990 to remove VOCs from groundwater detected in Pasadena drinking water wells located east/southeast of JPL.
- All water purveyors in the vicinity of JPL, under the supervision of CDHS, have taken steps (e.g., sampling, well water blending, water treatment, well closure) to ensure that all drinking water supplied to consumers meets drinking water standards.
- JPL performed indoor air quality sampling to ensure that VOC vapors detected in shallow soil near Building 107 are not collecting inside the building.
- In June 1999 JPL released a Draft Final RI report for OUs 1 and 3.
- In February 1999 JPL has released a draft RI report for OU 2.
Ongoing and Planned Actions
- When sufficient information on the toxicological effects of perchlorate become available, ATSDR will review the available information on perchlorate in nearby drinking water wells and further evaluate any potential public health hazards that may have been posed by exposure to perchlorate in groundwater.
- JPL is considering remedial options that would reduce or remove contamination from the groundwater. Currently, they have conducted a study of ion exchange resins for removing perchlorate and are currently evaluating other approaches and technologies. Until a feasible treatment technology or strategy is selected, ATSDR feels that the best approach to ensuring the availability of a safe source of water is through frequent monitoring of any potentially affected well.
- The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA; also known as Superfund), as amended, requires ATSDR to conduct needed follow-up health actions in communities living near hazardous waste sites. To identify appropriate action, ATSDR created the Health Activities Recommendation Panel (HARP). HARP has evaluated the data and information contained in the JPL Public Health Assessment for appropriate public health actions. It has been determined that the Division of Toxicology, ATSDR will prepare a Toxicological Profile for perchlorates.
W. Mark Weber, Ph.D.
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation
Gary Campbell, Ph.D.
Environmental Health Scientist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation
Assistance in the preparation of this report was provided by:
Public Health Scientist
Eastern Research Group
Senior Public Health Scientist
Eastern Research Group
Bonelli, L., Vitals, V., Bistolfi, F., Landucci, M., and P. Bruzzi. 1990. Hodgkin's disease in adults: Association with social factors and age at tonsillectomy. A case study. Int. J. Cancer. 45:423-427.
Bookman-Edmonston. 1997. Draft Raymond Groundwater Basin Perchlorate Contamination Problem Work Plan. Prepared by Bookman-Edmonston Engineering for the Raymond Basin Management Board. September 1997.
California Department of Health Services. See CDHS.
CDHS. 1997. Perchlorate in Drinking Water. Fact Sheet. California Department of Health Services. May 1997.
Chen Y.T., Zheng, T., Chou, M-C, P. Boyle. 1997. The increase of Hodgkin's disease incidence among young adults. Cancer. 79(11):2209-2218.
City of Pasadena. 1998. Personal communication with Brad Bowman, Principal Engineer, City of Pasadena Water and Power Department. February 19, 1998.
City of Pasadena. 1999. Personal communication with Farid Niknam, Engineer, City of Pasadena Water and Power Department. March 1999.
Ebasco. 1990a. Expanded Site Inspection Report, NASA-Jet Propulsion Laboratory. Prepared by Ebasco Environmental for NASA-JPL, Pasadena, CA. May 1990.
Ebasco. 1990b. Supplemental Information to the Expanded Site Inspection Report, NASA-Jet Propulsion Laboratory: Hazard Ranking System Documentation. Prepared by Ebasco Environmental for NASA-JPL, Pasadena, CA. November 1990.
Ebasco. 1993. Work Plan for performing a Remedial Investigation/Feasibility study, NASA-Jet Propulsion Laboratory. Prepared by Ebasco Environmental for NASA-JPL, Pasadena, CA. December 1993.
EPA. 1999. U.S. Environmental Protection Agency Office of Water. Overview of perchlorate issues. http://www.epa.gov/ncea/perch.htm
Foster Wheeler. 1997a. Report: Quarterly Groundwater Monitoring Results, February-March 1997. Prepared by Foster Wheeler Environmental Corporation for NASA-JPL, Pasadena, CA. April 1997.
Foster Wheeler. 1997b. Report: Quarterly Groundwater Monitoring Results, June-July 1997. Prepared by Foster Wheeler Environmental Corporation for NASA-JPL, Pasadena, CA. September 1997.
Foster Wheeler. 1997c. Soil-vapor probe, soil-vapor well, and soil boring data collected during RI activities for OU 2. Presented by Foster Wheeler Environmental Corporation to ATSDR on December 5, 1997.
Foster Wheeler. 1998a. Draft remedial investigation report for operable units 1 and 3: On-site and offsite groundwater. Prepared by Foster Wheeler Environmental Corporation for NASA-JPL, Pasadena, CA. September 1998.
Foster Wheeler. 1998b. Personal communication with B.G. Randolph, Foster Wheeler Environmental Corporation. February 27, 1998.
Foster Wheeler. 1999a. Draft remedial investigation report for operable unit 2: Potential on-site contaminant source areas. Prepared by Foster Wheeler Environmental Corporation for NASA-JPL, Pasadena, CA. February 1999.
Foster Wheeler. 1999b. Draft final remedial investigation for operable units 1 and 3: on-site and off-site groundwater. Prepared by Foster Wheeler Environmental Corporation for NASA-JPL, Pasadena, CA. June 1999.
Glaser, S.L. 1987. Regional variation in Hodgkin's disease incidence by histologic subtype in the US. Cancer. 60(11):2841-2847.
Grufferman, S. and E. Delzell. 1984. Epidemiology of Hodgkin's disease. Epidemiol. Rev. 6:76-106.
Gutensohn, N.M. and D.S. Shapiro. 1982. Social class risk factors among children with Hodgkin's disease. Int. J. Cancer. 30:433-435.
Hardell, L., Eriksson, M., Lenner, P., and E. Lundgreen. 1981. Malignant lymphoma and exposure to chemicals especially organic solvents, chlorophenols and phenoxy acids: A case-control study. Br. J. Cancer 43: 169-176.
Hebrst, H., Niedobitek, G., Kneda, M., Hummel, M. et al. 1990. High incidence of Epstein-Barr virus genomes in Hodgkin's disease. American Journal of Pathology. 136(1):13-18.
Jet Propulsion Lab. See JPL
JPL. 1991a. Environmental Cleanup Review Fact Sheet No. 1. April 1991.
JPL. 1991b. Jet Propulsion Laboratory Closeup. September 1991.
JPL. 1994. Superfund Community Relations Plan for National Aeronautics and Space Administration Jet Propulsion Laboratory. January 1994.
JPL. 1997a. Personal communication with Charles Buril, Manager, JPL Environmental Affairs Office. November 13, 1997.
JPL. 1997b. Superfund Project packet. Prepared for ATSDR. August 1997.
JPL. 1997c. Interoffice memorandum: Perchlorate in Drinking Water. Results from July 16, 1997 perchlorate sampling. August 15, 1997.
JPL. 1997d. Water sampling data from area water purveyors. Provided to ATSDR December 3, 1997 and June 24, 1998.
JPL. 1997e. Personal communication with Charles Buril, Manager, JPL Environmental Affairs Office. August 20, 1997.
JPL. 1998. Personal communication with Charles Buril, Manager, JPL Environmental Affairs Office. February 18, 1998.
JPL. 1999. Personal communication with Charles Buril, Manager, JPL Environmental Affairs Office. March 24, 1999.
La Cañada. 1998. Personal communication with Doug Laister, Engineer, La Cañada Irrigation District. February 19, 1998.
Lincoln Avenue. 1998a. Personal communication with Bob Heyward, Engineer, Lincoln Avenue Water Company. February 19, 1998.
Lincoln Avenue. 1998b. Personal communication with Bob Heyward, Engineer, Lincoln Avenue Water Company. December 3, 1998.
Los Flores. 1998. Personal communication with Ken Vader, Engineer, Los Flores Water Company. March 3, 1998.
Michels, K.B. 1995. The origins of Hodgkin's disease. Eur. J. Cancer. 4(5):379-388.
Mueller, N., Evans, A., Harris, N., Comstock, G., et al. 1989. Hodgkin's disease and Epstein-Barr. The New England Journal of Medicine. 320(11):689-695.
Olsson, H. and L. Brandt. 1980. Occupational exposure to organic solvents and Hodgkin's disease in men. A case-referent study. Scand. J. Work Environ. Health. 6(4):302-305.
Raymond Basin. 1997a. Personal communication with members of Raymond Basin Management Board. December 3, 1997.
Raymond Basin. 1997b. Watermaster Service in the Raymond Basin. July 1, 1996-June 30, 1997. September 1997.
Raymond Basin. 1998a. Personal communication with Ronald Palmer, Executive Officer, Raymond Basin Management Board. February 10, 1998.
Raymond Basin. 1998b. Comments on the Draft Public Health Assessment for the Jet Propulsion Laboratory. May 14, 1998.
Rothman, H. and N. Freed. 1989. Epidemiology of Hodgkin's disease. JAOA. 89(6):783-785.
Rubio Canyon. 1998. Personal communication with Wally Weaver, Engineer, Rubio Canyon Land and Water Company. March 5, 1998.
Stiller, C.A. 1998. What causes Hodgkin's disease in children ? Eur. J. Cancer. 34(4):523-528.
Swaen, G.M., Slangen, J.M., Ott, M.G., Kusters, E., et al. 1996. Investigation of a cluster of ten cases of Hodgkin's disease in an occupational setting. Int. Archives Occup. Environ. Health. 68(4):224-228.
Valley Water. 1998a. Personal communication with Andy Boytim, Engineer, Valley Water Company. February 19, 1998a.
Valley Water. 1998b. Personal communication with Andy Boytim, Engineer, Valley Water Company. RE: Water quality data. November 1998.
Valley Water. 1999. Personal communication with Andy Boytim, Engineer, Valley Water Company. February 26, 1999.
U.S. Environmental Protection Agency. See EPA.
1. The city of Pasadena has four wells located near JPL, but only three are currently operating since the Arroyo well's closure in June/July 1997 (City of Pasadena, 1999).
2. Local purveyors prefer not to import water because the cost of imported water is generally much higher than the costs of treatment (Raymond Basin, 1997a).
3. The cell of origin is the particular cells in the body that the virus attacks, and thus initiates the disease process.