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Site Location Map
Figure 1. Site Location Map

Conceptual Model Illustration for the Jet Propulsion Laboratory
Figure 2. Conceptual Model Illustration for the Jet Propulsion Laboratory

Locations for JPL Groundwater Monitoring Wells and Nearby Municipal Production Wells
Figure 3. Locations for JPL Groundwater Monitoring Wells and Nearby Municipal Production Wells

ATSDR's Exposure Evaluation Process
Figure 4. ATSDR's Exposure Evaluation Process



Occurring over a short time, usually a few minutes or hours. An acute exposure can result in short-term or long-term health effects. An acute effect happens a short time (up to 1 year) after exposure.

Surrounding. For example, ambient air is usually outdoor air (as opposed to indoor air).

A chemical component of a sample to be determined or measured. For example, if the analyte is mercury, the laboratory test will determine the amount of mercury in the sample.

Background Level:
A typical or average level of a chemical in the environment. Background often refers to naturally occurring or uncontaminated levels.

Any substance that may produce cancer.

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, also known as Superfund. This is the legislation that created ATSDR.

Occurring over a long period of time (more than 1 year).

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

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

Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.

Referring to the skin. Dermal absorption means absorption through the skin.

The amount of substance to which a person is exposed. Dose often takes body weight into account.

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

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

Exposure Investigation:
The collection and analysis of site-specific information to determine if human populations have been exposed to hazardous substances. The site-specific information may include environmental sampling, exposure-dose reconstruction, biologic or biomedical testing, and evaluation of medical information. The information from an exposure investigation is included in public health assessments, health consultations, and public health advisories.

Finished Water:
Water that has been filtered, blended with water from other source(s), or treated with other chemical or physical processes to produce water that is suitable for human consumption.

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

Health Investigation:
Any investigation of a defined population, using epidemiologic methods, which would assist in determining exposures or possible public health impact by defining health problems requiring further investigation through epidemiologic studies, environmental monitoring or sampling, and surveillance.

Health Consultation:
A response to a specific question or request for information pertaining to a hazardous substance or facility (which includes waste sites). It often contains a time-critical element that necessitates a rapid response; therefore, it is a more limited response than an assessment.

Health Outcome Data:
A major source of data for public health assessments. The identification, review, and evaluation of health outcome parameters are interactive processes involving the health assessors, data source generators, and the local community. Health outcome data are community specific and may be derived from databases at the local, state, and national levels, as well as from data collected by private health care organizations and professional institutions and associations. Databases to be considered include morbidity and mortality data, birth statistics, medical records, tumor and disease registries, surveillance data, and previously conducted health studies.

Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.

Breathing. Exposure may occur from inhaling contaminants because they can be deposited in the lungs, taken into the blood, or both.

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

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

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

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

No Public Health Hazard:
Sites for which data indicate no current or past exposure or no potential for exposure and therefore no health hazard.

An area of chemicals in a particular medium, such as air or groundwater, moving away from its source in a long band or column. A plume can be a column of smoke from a chimney or chemicals moving with groundwater.

Potential/Indeterminate Public Health Hazard:
Sites for which no conclusions about public health hazard can be made because data are lacking.

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

Public Availability Session:
An informal, drop-by meeting at which community members can meet one-on-one with ATSDR staff members to discuss health and site-related concerns.

Public Comment:
An opportunity for the general public to comment on Agency findings or proposed activities. The public health assessment process, for example, includes the opportunity for public comment as the last step in the draft phase. The purposes of this activity are to 1) provide the public, particularly the community associated with a site, the opportunity to comment on the public health findings contained in the public health assessment, 2) evaluate whether the community health concerns have been adequately addressed, and 3) provide ATSDR with additional information.

Public Health Action:
Designed to prevent exposures and/or to mitigate or prevent adverse health effects in populations living near hazardous waste sites or releases. Public health actions can be identified from information developed in public health advisories, public health assessments, and health consultations. These actions include recommending the dissociation (separation) of individuals from exposures (for example, by providing an alternative water supply), conducting biologic indicators of exposure studies to assess exposure, and providing health education for health care providers and community members.

Public Health Advisory:
A statement by ATSDR containing a finding that a release of hazardous substances poses a significant risk to human health and recommending measures to be taken to reduce exposure and eliminate or substantially mitigate the significant risk to human health.

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

Public Health Hazard:
Sites that pose a public health hazard as the result of long-term exposures to hazardous substances.

Raw Water:
A term, when used in reference to a water supply intended for treatment for a public water supply, describes the water extracted directly from groundwater or surface water, prior to filtration, blending with water from other sources, or other chemical of physical treatment processes.

In risk assessment, the probability that something will cause injury, combined with the potential severity of that injury.

Risk Communication:
Activities to ensure that messages and strategies designed to prevent exposure, adverse human health effects, and diminished quality of life are effectively communicated to the public. As part of a broader prevention strategy, risk communication supports education efforts by promoting public awareness, increasing knowledge, and motivating individuals to take action to reduce their exposure to hazardous substances.

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

Significant Health Risk:
Circumstances where people are being or could be exposed to hazardous substances at levels that pose an urgent public health hazard or a public health hazard; public health advisories are generally issued when urgent public health hazards have been identified.

Another name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), which created ATSDR.

Superfund Amendments and Reauthorization Act (SARA):
The 1986 legislation that broadened ATSDR's responsibilities in the areas of public health assessments, establishment and maintenance of toxicologic databases, information dissemination, and medical education.

Toxicological Profile:
A document about a specific substance in which ATSDR scientists interpret all known information on the substance and specify the levels at which people may be harmed if exposed. The toxicological profile also identifies significant gaps in knowledge on the substance, and serves to initiate further research, where needed.

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


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

Action Level (AL)
Action Levels are based upon a mode-of-action approach that harmonized noncancer and cancer approaches to derive a single oral risk benchmark (RfD). The contaminant concentration expressed in terms of mg/kg/day when applied to the standard default body weight (70 kg) and water consumption (2 L/day) results in an action level expressed as the chemical concentration expressed as parts per billion (ppb). An Action Level is a regulatory level recommended by the EPA or a state health department warrant or trigger a response action under Superfund.

Cancer Risk Evaluation Guides (CREGs)
CREGs are estimated contaminant concentrations that would be expected to cause no more than once excess cancer in a million (10-6) persons exposed over a lifetime. ATSDR's CREGs are calculated from EPA's cancer potency factors.

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

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

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



The perchlorate ion (ClO4-) is often used by chemists to promote crystallization of compounds. Perchlorate is soluble in water and is a strong oxidant. Ammonium perchlorate (NH4ClO4), in particular, is used in the manufacture of solid rocket fuel, fireworks, and explosive devices.

Although perchlorate has been known as an environmental contaminant at some hazardous waste sites, no standardized methods exist for detecting perchlorate in water, and, until recently, perchlorate could not be detected at concentrations below 400 ppb. In 1997, Aerojet Corporation--a company responsible for a Superfund site in southern California where perchlorate has been a contaminant of concern--developed a new analytical method to detect perchlorate concentrations as low as 4 ppb. CDHS subsequently began urging California water purveyors and responsible parties at hazardous waste sites to analyze groundwater for perchlorate using the new test method. Since sampling began in the summer of 1997, perchlorate has been detected at low levels in wells throughout southern California, and at higher levels in some areas. As a result, regulatory agencies, water purveyors, and the public are becoming more aware of perchlorate as a potential contaminant in drinking water and are especially interested in the potential health effects of this contaminant.

Health Effects

In 1992 and again in 1995, EPA evaluated the body of toxicological information on perchlorate and determined that, although there is considerable information about the health effects from short-term exposure to perchlorate, there is not enough information about the effects from long-term exposure (CDHS, 1997). At high levels, perchlorate can interfere with production of thyroid hormones and lead to below-normal levels of thyroid hormones in the blood. This condition, called hypothyroidism, can cause the body to increase its production of thyroid stimulating hormone (TSH). Increased levels of TSH may cause enlargement of the thyroid and a person to feel sluggish, depressed, cold, or tired. Because perchlorate can reduce the body's level of thyroid hormone, in the past doctors used high doses of potassium perchlorate (KClO4) as a drug treatment for people with hyperthyroidism, a condition in which the thyroid produces an above-normal amount of hormones (this condition is often caused by Grave's Disease). Perchlorate treatments were discontinued when some patients developed blood or immune system disorders. However, it is unknown if perchlorate caused these problems (CDHS, 1997). As the interest in perchlorate contamination has grown, EPA and other researchers have begun new studies on the toxicological effects of perchlorate. ATSDR will analyze all new data on perchlorate as they become available, and will use any and all new information to further evaluate the perchlorate contamination at JPL.

Safe Drinking Water Levels

Based on the existing toxicological studies of perchlorate, EPA derived a provisional reference dose (RfD) for perchlorate. An RfD is a dose of chemical to which a person could be exposed over a long period of time without an increased risk of adverse, non-cancer health effects. Using the available toxicological information, EPA estimated that a perchlorate dose of 0.14 mg/kg/day (i.e., a mg of perchlorate absorbed per kilogram of a person's body weight per day) would not be expected to adversely affect a person's thyroid. By applying a safety margin of 300 to 1,000 to this value to account for any uncertainties in the toxicological data, EPA derived an RfD of 1 to 5 x 10-4 mg/kg/day. CDHS used the upper limit of this range (0.0005 mg/kg/day) to determine a provisional drinking water standard (called an "action level") of 18 ppb for California. Subsequent review of the toxicology of perchlorate has resulted in a proposed oral benchmark of 0.0009 (see EPA, 1999). This higher dose would give an action level of about 32 ppb, but formal action or adoption of these values has not yet occurred

Because of the 300-fold margin of safety, the current California action level of 18 ppb would translate to a perchlorate dose that is 300 times less than the lowest dose of perchlorate at which no adverse health affects have been observed. For example, although the action level is 18 ppb, a person could drink 8 cups (approximately 2 liters) of water contaminated with 540 ppb perchlorate and still be ingesting 10 times less perchlorate than the lowest amount at which no health effect has been observed in toxicological studies.

Monitoring Drinking Water for Perchlorate

Since CDHS initiated sampling in 1997, perchlorate has been detected in numerous monitoring and drinking water wells in the Monk Hill Sub-basin and elsewhere in the Raymond Basin. CDHS schedules sampling for the various water purveyors in the area to ensure that perchlorate levels are adequately monitored. CDHS regularly reviews the sampling data from all water purveyors, and adjusts the required sampling schedules as contaminant concentrations in the wells change. If perchlorate concentrations rise above the action level in drinking water wells, CDHS requires the water purveyor to shut down the contaminated well or take other steps (e.g., blending the groundwater with imported water or water from other wells) to ensure that the finished drinking water distributed to consumers meets the action level. If a water purveyor is unable to take these steps, it is required to inform its customers about the contaminated drinking water. In addition to the samples mandated by CDHS, many water purveyors perform more frequent sampling to ensure their compliance with water quality standards. Current sampling schedules of the water purveyors closest to JPL are listed in Table 1.

Perchlorate at JPL

In the summer of 1997, sampling showed the presence of perchlorate in JPL monitoring wells and in Pasadena municipal wells located east/southeast of JPL. Perchlorate concentrations above the CDHS action level forced the closure of the Pasadena drinking water well located closest to JPL (the Arroyo Well--see Figure 3). Perchlorate levels have recently risen above the action level in the next Pasadena well downgradient to JPL, Well No. 52. 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). In 1997, JPL sampled tap water from several locations at the facility and did not detect perchlorate above the action level (JPL, 1997c). The current sampling and blending procedures used at the drinking water wells near JPL are expected to prevent any potential present or future public health hazards posed by perchlorate in groundwater.

Perchlorate in groundwater was not analyzed before 1997, so it is unknown what the perchlorate levels in the Pasadena drinking water wells or other nearby wells were in the past. The rise in perchlorate levels observed during 1997 in the Pasadena wells may indicate that perchlorate levels were lower in these wells in the past. Although the Arroyo Well had perchlorate levels above the action level when perchlorate analysis began, the other three wells did not exceed the action level, so the blended water from these four wells probably did not exceed the action level. Even if finished water from these wells did exceed the action level in the past, this action level is very conservative. In fact, the maximum perchlorate concentration detected at JPL to date (615 ppb, in monitoring well MW-16), if present in drinking water, would still translate to a dose of perchlorate that is about eight times less than the lowest dose at which no health effect has been observed in toxicological studies. Based on the available data from JPL, it is unlikely that past perchlorate levels in groundwater have posed a public health hazard. Because there is no information on past perchlorate levels, however, ATSDR considers past exposures to perchlorate in off-site groundwater at JPL to be an indeterminate public health hazard.

Cleaning Up Perchlorate

Previous to the current investigations to determine feasible methodologies to remove the perchlorate anion from drinking water, the only known method of removing low levels of perchlorate from water was a reverse osmosis membrane technique that is very expensive (Bookman-Edmonston, 1997) and has not been implemented on a large scale for drinking water. EPA, the Department of Defense, responsible parties at hazardous waste sites, environmental technology companies, and university researchers are studying potential perchlorate cleanup technologies. JPL and its environmental contractors are currently looking at a number of possible cleanup strategies, including ion-exchange resins and hydrogenation (JPL, 1998). Very promising results have been obtained after conducting a series of large scale tests and a feasible cleanup system may heve been identified for use at JPL (JPL, 1999). The Raymond Basin Management Board has organized a Perchlorate Task Force--made up of water purveyors, state and federal regulators, and other interested parties--to look at ways to prevent, minimize, and clean up perchlorate contamination in the groundwater of the Raymond Basin. ATSDR will evaluate any developments in perchlorate treatment to assess their potential effect on environmental conditions and public health at JPL.


Regular sampling for perchlorate, 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 these actions will continue to eliminate any potential public health hazard posed by exposure to perchlorate in groundwater near JPL. The presence of perchlorate contamination in groundwater is not without consequences, however. Until an effective treatment is identified, there is no practical way to remove perchlorate from water if perchlorate levels continue to rise in the groundwater near JPL. Therefore, water purveyors may need to close down more of their drinking water wells to prevent contamination. If these water purveyors are forced to replace their groundwater with much more expensive imported water, the increased cost could have a large economic impact on the communities that depend on these water purveyors to supply their drinking water. In addition, the availability of imported water in California can vary dramatically from year to year, depending on a host of conditions throughout the southwestern United States including rainfall, water demand, and ecological conditions. The conservation, preservation, and remediation of groundwater supplies is therefore vitally important to the people of southern California.


Population Data Table:

NASA Jet Propulsion Laboratory, Los Angeles County
  La Cañada-Flintridge1 La Cañada -Flintridge2 Altadena3 Altadena4
Total persons 5,294 4,245 4,200 6,006
Total area, square miles 2.92 1.00 0.50 0.7
Persons per square mile 1,815 4,250 8,329 8,528

% Male 49.7 48.6 48.8 49.9
% Female 50.3 51.4 51.2 50.1

% White 83.1 85.3 19.5 18.5
% Black 0.2 0.0 67.3 59.8
% American Indian, Eskimo, or Aleut 0.2 0.0 0.3 0.5
% Asian or Pacific Islander 15.4 13.5 2.9 4.2
% Other races 1.2 1.2 10.0 17.0

% Hispanic origin 3.8 4.8 16.0 27.4

% Under age 10 12.7 14.3 17.3 19.2
% Age 65 and older 12.1 13.8 10.1 8.7

Source: Census of Population and Housing, 1990: Summary Tape File 1A (California) [machine-readable data files]. Prepared by the Bureau of the Census. Washington, DC: The Bureau [producer and distributor], 1991.

1 Tract 4605.01 (see census tract map); 2 Tract 4505.02 (see census tract map);3 Tract 4603.02 (see census tract map); and 4 Tract 4610.00 (see census tract map)


NASA Jet Propulsion Laboratory, Los Angeles County
  La Cañada-Flintridge1 La Cañada -Flintridge2 Altadena3 Altadena4
Households* 1,331 1,785 1,469 1,713
Persons per household 3.11 2.97 2.89 3.44

% Households owner-occupied 75.5 94.5 90.5 67.4
% Households renter-occupied 24.5 5.5 9.5 32.6

% Households mobile homes 0.2 0.0 0.0 0.1

% Persons in group quarters 1.5 0.0 0.0 1.8

Median value, owner-occupied households, $ 167,800 500,001 467,900 157,700
Median rent paid, renter-occupied households, $ 572 1,001 969 549

Source: Census of Population and Housing, 1990: Summary Tape File 1A (California) [machine-readable data files]. Prepared by the Bureau of the Census. Washington, DC: The Bureau [producer and distributor], 1991.

* A household is an occupied housing unit, but does not include group quarters such as military barracks, prisons, and college dormitories.

1 Tract 4605.01 (see census tract map)
2 Tract 4505.02 (see census tract map)
3 Tract 4603.02 (see census tract map)
4 Tract 4610.00 (see census tract map)

Census Tract Map
Census Tract Map


The Agency for Toxic Substances and Disease Registry (ATSDR) released the Jet Propulsion Laboratory (JPL) Public Health Assessment (PHA) on August 4, 1998 for public review and comments. That public comment period ended September 20, 1998. During that period ATSDR received the following comments/questions from six individuals and two organizations or agencies.

Some of the comments received were very similar and those comments were grouped and summarized or, if possible, one exemplary comment was selected to state the issue. For comments that questioned the validity of statements made in the PHA, ATSDR verified or corrected the statements. ATSDR has not addressed requests for information to be included in the PHA, unless the party who filed the request provided the supporting documentation. The list of comments does not include editorial comments concerning such things as word spelling or sentence syntax.

Potential Past Exposure Comments

Several public comments were received that questioned various aspects of the ATSDR evaluation of the potential for human exposure to contaminants in the past. For the convenience of the reader we have grouped those comments and our responses together.

  1. Comment: One commenter wrote: "The Public Health Assessment for JPL does not contain enough scientific facts to support its conclusions that there are no health hazards from completed pathways of volatile organic compound (VOC) toxins at this site. It relies upon only current levels of toxins in the water to state that there was, is, and will be no health risk. It totally neglects to give correct data on past levels of toxins and any subsequent health hazards."
  2. Response: In the preparation of this public health assessment, as with all others, much more information and data are reviewed in the analysis phase than are incorporated in the document. Because of the concerns expressed about our evaluation of the potential for past exposure to contaminants from JPL, we decided to incorporate more historical data in the "Evaluation of Potential Exposure Pathways" sections and in Tables 3 and 4 on the levels of contaminants detected in the drinking water wells near JPL.

    Please keep in mind that these data we have been included in the assessment are from raw water samples prior to any treatment or blending with water obtained from other wells or water sources. Depending upon the level that contaminants are detected and many other specific circumstances, the detection of contaminants in the well may trigger a range of response actions, including the need for additional or more frequent sampling, the need to cease production of water from that well, or the need to treat or blend that water to ensure that the quality of the finished water meets safe drinking water standards.

    It must be emphasized, as we discussed in the public comment draft of this PHA, our review of the implications of groundwater contamination at JPL indicates there is no evidence of past human exposure to VOC-contaminated drinking water at levels know to result in adverse human health effects.

  3. Comment: One commenter wrote: "Contaminants are found at high levels in groundwater monitoring wells proving that human exposure has occurred."
  4. Response: ATSDR emphasizes that regardless of the presence or extent of contamination detected in groundwater monitoring wells located at or near the JPL site, exposures are only possible if people drink or otherwise come in contact with the groundwater. Monitoring wells characterize the contamination in the groundwater, but as we discuss in the PHA, no one uses groundwater drawn from beneath or immediately near the JPL site, where the highest levels of contamination. Therefore, no one has been exposed to the most contaminated groundwater. Rather, area residents receive drinking water from water purveyors, who are required by law to test and ensure that the drinking water they deliver to their customers meets federal and state standards. For a more detailed discussion on elements of an exposure pathway that might lead to human exposure, please see the "Evaluation of Potential Exposure Pathways" section of the PHA.

    Additionally, it is important to understand that monitoring wells are constructed to draw samples of groundwater from specific depth intervals, whereas drinking water wells are usually constructed to extract groundwater over a much thicker section of the saturated aquifer. Thus, while a monitoring well permits contaminant sampling of very narrow interval(s) of the aquifer to permit evaluation of plume characteristics, drinking water wells blend water from many levels of the aquifer and, therefore, typically show lower contaminant values than nearby monitoring wells.

  5. Comment: Some comments asserted that JPL has been contaminating drinking water for 50 to 60 years and that is a "long period of exposure"
  6. Response: ATSDR is not aware of any evidence to suggest that area's drinking water supplies have been contaminated for 50 to 60 years, or that people could have been exposed to contaminated drinking water for that duration. A number of factors suggest that it is highly unlikely that customers ever received finished drinking water containing harmful levels of contaminants originating from JPL. First, and most importantly, we know that since testing began in the 1980s, finished drinking water delivered to area customers has safely met drinking water standards. Second, water purveyors have blended raw well water with other well water over the course of their history and/or with imported sources since the 1950s. By blending raw well water with other sources, chemical concentrations, if any were present in the wells at the time, have been greatly diluted and reduced to safe levels. Third, it is unlikely that the contaminants have been in the public wells (or raw water) for 50 to 60 years, or since JPL started operations in 1945. Although information is not available to tell us when contaminants first reached some of the area public water supply wells, we know that it could take many years for the contaminants to infiltrate through the soils and alluvium from source areas at JPL to the groundwater and then migrate to the public drinking water supply wells.

  7. Comment: One commenter wrote: "The report acknowledges that there is no information on the level or presence of perchlorate prior to approximately 1996. In view of the absence of information on the presence and distribution of perchlorate in the drinking water, how is it possible to reach a conclusion that this has not been harmful?" Another commenter is also concerned that "ATSDR simply ignores the fact that JPL likely had the capability of doing this work, and perhaps has records which have not been provided to it."
  8. Response: Because the technology for accurately measuring perchlorate was not available until 1997, we do not have any data, nor does JPL, on what levels of perchlorate, if any, might have been present in drinking water supplies prior to that time. Without these data, it is difficult to determine with certainty when perchlorate first reached these area drinking water wells (e.g., city of Pasadena, Lincoln Water). In light of these uncertainties, we used our knowledge of the nature of groundwater and contaminant migration beneath JPL and our best professional judgement to draw conclusions regarding the likelihood of potential exposure to harmful levels of perchlorate. We must remind the reader that perchlorate was detected at elevated levels in the samples of untreated and unblended raw well water. ATSDR emphasizes that the treatment and blending processes, which have been practiced for many years, would have greatly diluted any perchlorate, if present, in well water before reaching the customer.

  9. Comment: One commenter was concerned that "Since water flows downhill and would clearly flow under the JPL site and into the Arroyo Secco spreading ponds, it is difficult to understand how a conclusion was reached that no toxic substances reach the drinking water."
  10. Response: ATSDR has stated in its environmental pathways discussion that trichloroethylene (TCE), tetrachloroethylene (PCE), carbon tetrachloride, and perchlorate have been detected above ATSDR's comparison values, EPA's MCLs, and/or CDHS action levels in the groundwater and raw water drawn from municipal drinking water wells operated the city of Pasadena, the Lincoln Avenue Water Company, and the Valley Water Company. With the exception of PCE, these chemicals are believed to have originated from the JPL site. As stated above, the reader should remember that the "raw" water containing the elevated levels of these chemicals is treated and blended with other well water or imported water before it is delivered to the customer. These routine measures dilute and/or remove the contaminants, if present, in the drinking water before it reaches residential taps. Local water purveyors must also conduct scheduled testing of the finished water quality to ensure it meets the state's drinking water standards.

  11. Comment: Several commenters expressed concerns about the extent of the discussion in the PHA on hazardous waste at the JPL site. They wrote: "There is no discussion of the nature of the buried material which ATSDR acknowledges is to be found on the site." and "ATSDR acknowledges that the use and disposal of chemical substances at JPL was done in a manner likely to penetrate into the groundwater and reach the soil and air. However, there is no review of the nature of the materials."
  12. Response: In evaluating potential public health hazards, ATSDR thoroughly reviews the available environmental data for any and all suspected releases. However, because it would be a duplication of effort to present every piece of environmental data in our document, we strive to present only the most relevant material for the exposure pathways of greatest concern. For a more detailed discussion on buried material at the site, please refer to JPL documents cited in the "Reference" section of this PHA.

  13. Comment: One commenter wrote: "ATSDR is silent on the question of monitoring of the use and disposal of material and migration of contaminants on and off site from 1936 to 1979."
  14. Response: Prior to the late 1970s, little if any environmental monitoring occurred, owing largely to the absence of federal, state, or local environmental requirements. It should be noted that this problem is not specific to JPL, but is a common concern at many other National Priorities List (NPL) sites and hazardous releases. One of the challenges we face is to evaluate public health hazards that may have occurred in the past, given the absence of adequate environmental monitoring. Where no historical data exist, we review available environmental and contaminant fate data and make assumptions about past exposure using our best professional judgement.

  15. Comment: One commenter wrote: "There is no acknowledgment of changes in standards which would have created a false sense of security since water standards have progressively fallen over the last 50 years. Although JPL may have been in compliance, and drinking water resources may have been in compliance with standards in the past, those standards were unlikely to be protective in the light of today's toxicologic knowledge."
  16. Response: In the 1980s, the federal EPA established mandatory water quality guidelines (standards) for key chemical contaminants, including TCE and carbon tetrachloride--the primary contaminants detected in groundwater at JPL. These standards set limits on the amount of a chemical that can be contained in drinking water supplies. Since that time, EPA and CA EPA have developed more standards and has changed some standards to reflect the current understanding of a chemical's toxicology. In 1997, the CDHS set a provisional water quality standard for perchlorate, another contaminant of concern at the site. However, there have been no changes in the MCLs for TCE, carbon tetrachloride, and the action level for perchlorate since they were developed.

  17. Comment: One commenter is concerned that "ATSDR's report assumes that the regional water purveyors were properly monitoring, treating, and blending drinking water to keep the finished water within standards. No data to support this is offered."
  18. Response: We based our discussions on information provided to us by the Raymond Basin Management Board and area water purveyors. The Raymond Groundwater Basin was adjudicated in 1943-44 and regulated under direction of the state of California. Since 1984, the Raymond Basin Management Board, under the California Department of Health Services requirements, has coordinated routine sampling, analysis, and monitoring programs throughout the basin to ensure that drinking water meets standards set by local, state, and federal regulatory agencies. ATSDR feels confident that, since these programs have been in place, and subject to state oversight and regulatory review, the state and area water purveyors have taken and continue to take appropriate measures to ensure that water is safe to drink.

    Because of the lack of demonstrated need, the absence of extensive regulatory requirements, and the limitations in the analytical methods applied to the testing of drinking water, limited groundwater monitoring occurred prior to the 1980s for the chemicals of concern identified at the site. It should be noted, however, that "raw", untreated well water has been blended either with imported water since the 1950s or with other well water. Therefore, if any low-level contamination from any source reached any potentially affected, nearby wells during the 1950s or later, the cumulative effects of blending of water from multiple sources, treatment, pumping to and holding in storage tanks resulted in not only a significant dilution of VOC content but also a significant reduction in the VOC content due to the volatilization and extractive effects of water processing before delivery to the customer's tap at their residence.

Other Comments:

  1. Comment: Please clarify the difference between on-site and off-site groundwater if all groundwater belongs to the Raymond Basin.
  2. Response: The Raymond Basin covers approximately 40 square miles and includes groundwater beneath the JPL site and in its vicinity. During environmental investigations of the JPL site, groundwater samples were taken both from on-site wells (located within the JPL site boundaries) and from off-site wells (located beyond the JPL site boundaries). ATSDR reviews on-site groundwater data to determine whether chemicals used or stored at a site have entered the groundwater beneath or near suspected sources. Because groundwater is constantly moving under the site, ATSDR also reviews off-site groundwater monitoring data to help determine whether contaminants have traveled with groundwater beyond a site's boundaries, and to what extent. This is important because we want to know if contaminants have reached drinking water sources, or if they have the potential to in the future.

  3. Comment: One commenter wrote: "According to the information provided by ATSDR, the remedial investigation will not be completed until 1999, and the ATSDR did its site visit and data collection in 1997. Clearly, the report is based on incomplete data and any conclusion seems premature."
  4. Response: The conclusions and recommendations in the JPL PHA are based on environmental data and exposure information available at the time the document was prepared. ATSDR reviewed the draft RI reports for operable units 1, 2, and 3 (Foster Wheeler, 1990a, 1999b) prior to the release of this version of the PHA

    Sometimes site characterization and/or remediation continues for years after releases have first been suspected and after ATSDR's involvement begins. In such cases, a PHA may not be a single fixed document but will likely reflect the dynamic, iterative process of collection and evaluation of new information regarding the site. Therefore, if new data are collected or additional information compiled that suggests the public health may be adversely affected, ATSDR will modify or add to the document to reflect the public health implications of the additional data.

  5. Comment: One commenter wrote: "There is no characterization of plume movement or content."
  6. Response: A description of the groundwater contaminant plumes has been added to the PHA. Please see pages 11 - 13.

  7. Comment: One commenter asked why the well water is blended with imported water.
  8. Response: The available groundwater supply in the area around JPL is inadequate to serve all the needs of the rapidly expanding population. To ensure that their communities have sufficient supplies to meet increasing demands, many water purveyors augment their water supplies with imported surface water. Today, some communities import as much as 75 percent of their water supply from surface water sources.

  9. Comment: One commenter wrote: "The PHA cites that future increases in levels of contamination can be handled by water purveyors. If, however, contamination increases to the point that multiple wells must be closed, it is not certain that adequate supplies of additional imported water will be available to solve the problem."
  10. Response: ATSDR acknowledges that contamination can severely restrict the use wells and, in turn, of the groundwater resource of the basin and force area purveyors to import more water at a greater unit-cost. ATSDR also recognizes that ultimately there is a finite supply of water available in the combined resources of an adjudicated groundwater basin and the imported water supply. ATSDR did not intend to imply that the blending of water should in any way serve as a long-term solution to water quality problems in the basin. While blending has diluted the level of contaminants in the finished water and ensured the safety of the water delivered to customers, ATSDR agrees with the purveyors that the best approach to ensuring the availability of a safe source of water is to treat the contamination in the aquifer or, if necessary, at the point of use. But until effective remediation technologies are identified, ATSDR recommends that monitoring continue. ATSDR has added a recommendation to the "Public Health Action Plan" section of this PHA that addresses this concern.

  11. Comment: One individual expressed concern that the groundwater was blended with surface water from the Colorado River, which also contains perchlorate.
  12. Response: Several water purveyors, including the city of Pasadena, the Lincoln Avenue Water Company, and the Valley Water Company import surface water from the Metropolitan Water District of Southern California (MWDSC) to augment their drinking water supplies. The MWDSC obtains water from the Colorado River and from northern California. The MWDSC routinely checks the quality of water before delivering it to the purveyors. Since the methodology to test for perchlorate at low detection levels, the level of perchlorate in the water imported from the Colorado River has ranged from ND to about 7 ppb with a reported high of 16 ppb (see Foster Wheeler, 1999b) Thus, the safety of that source of drinking water is ensured through monitoring, as is the safety of the resultant blended water supplied by the water purveyors to their customers.

  13. Comment: One commenter wrote: "ATSDR has not calculated delivered doses or dose equivalents for any of the materials which have been identified in the drinking water. Thus, even volatile hydrocarbon distribution and dosage have not been calculated for which hydraulic models and pharmacokinetically based dose models are available."
  14. Response: ATSDR developed conservative estimates of exposure based on "raw" water. ATSDR assumed that every day an adult (154 pounds) and a child (22 pounds) drank "raw" water containing the highest detected concentrations of TCE, PCE, carbon tetrachloride, and perchlorate. (ATSDR considers this a highly conservative and unlikely exposure scenario.) ATSDR then compared these estimated doses to their respective minimal risk levels (MRLs) or reference doses (RfDs). In all cases, the calculated values were within an order of magnitude of the guidance levels. Because the calculated values were derived using contaminant concentrations in "raw" water rather than in " finished" water (finished drinking water has been blended and treated to meet safe drinking water standards) and because the guidance levels for the contaminants of concern are set many times lower (300 to 1,000 fold for perchlorate, see Appendix B) than the level shown in toxicologic studies to result in adverse health effects, ATSDR does not expect that drinking finished public water, or using that water as it is delivered to the tap at the home, will harm residents' health. ATSDR has added an expanded discussion on exposure to the "Exposure Pathway Evaluation" section.

  15. Comment: One commenter wrote: "ATSDR states that Hodgkin's disease has no reported association with any chemical exposure. This is not correct."
  16. Response: We have added a discussion on Hodgkin's disease (HD) to the "Community Health Concern" section of this PHA. As the discussion states, most researchers today agree that the likely cause of HD is an infectious agent. Although medical researchers suspect that environmental factors may influence whether an individual contracts HD, no specific environmental agents have been linked to the disease. Some studies have noted a higher than average rate of HD in workers exposed to organic solvents. Because workers are often exposed to multiple chemicals over the course of their work, researchers were not able to identify which particular solvent may have been linked to the increased rate of the disease. Furthermore, ATSDR found no studies that associate HD with either perchlorate or TCE, two chemicals of particular concern to the community.

  17. Comment: A commenter expressed concern that "ATSDR dismisses the reported increase in incidence of HD without investigation which is inappropriate." They asked ATSDR to "Explain why an epidemiological study has not been done to assess whether any HD disease or other health effects have occurred."
  18. Response: In assessing threats to the public's health, ATSDR first examines the potential exposure pathways related to a site. If ATSDR determines that a completed exposure pathway to environmental contaminants poses a potential public health threat, ATSDR may gather health outcome data to complement the environmental and exposure data. In evaluating available data from the JPL site, ATSDR has not found a completed exposure pathway posing a potential public health hazard. Based on the data available for review, ATSDR does not believe that contaminants from the JPL site are responsible for health problems such as Hodgkin's disease or cancer.

  19. Comment: What kinds of cancers were found in the community, how many cases, and what are the chances that a large number of similar cancers is coincidental.
  20. Response: The CDHS monitors cancer incidence in California communities. Community members with specific concerns about cancer rates in the area surrounding the JPL site should express their concerns to the CDHS's Cancer Surveillance at 510-540-2711.

  21. Comment: One commenter asked ATSDR to explain how we conclude that no adverse health effects are expected while assigning an intermediate public health hazard to the site.
  22. Response: 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.

  23. Comment: A commenter is concerned that the community is not being informed about information sessions about the site. They asked ATSDR to explain how the public is being informed about meetings as well as availability of remedial investigation reports.
  24. Response: At the outset and as an integral part of the public health assessment process, ATSDR issued a press release on November 19, 1997 to the major and local are news media of the Los Angeles-Pasadena area announcing a series of four public availability sessions to be held in the Pasadena Holiday Inn on December 2, 1997 and at the La Canada-Flintridge Library, La Canada, CA on December 3, 1997. Those sessions were attended by a total of eleven community members. Follow-up press coverage appeared in the Pasadena Star News and JPL's newspaper, The Universe.

    With the release of the Public Comment Draft of the JPL Public Health Assessment, ATSDR developed a two-sided fact sheet summarizing the assessment process and the findings of the assessment. Copies of that assessment draft and fact sheet were distributed to a total of 30 individuals and/or organizations and made available in the official document repositories established for the JPL site: the Pasadena Central Library, the La Cañada-Flintridge Public Library, the Altadena Public Library, and the JPL Library. In addition, multiple copies of the fact sheet were distributed to the libraries and to a La Cañada-Flintridge woman's group.

    JPL has sponsored several community activities to inform the public about environmental conditions at JPL and about the progress of any remediation activities. Many of these community activities are required by the U.S. Environmental Protection Agency's Superfund regulation. To assist in community relation activities, JPL has prepared a community relations plan that details community concerns (gathered from 43 interviews), develops a process to further investigate the needs of the public, and presents a plan to keep community members informed about actions at the site. This plan as well as other information about the site is kept at the Pasadena Central, Altadena Public, and the La Cañada-Flintridge Public Libraries.

    In addition, JPL has provided site information and public meeting schedules in the regional and local newspapers (e.g., Los Angeles Times, Pasadena Star-News), in informational fact sheets, and a news letter. JPL representatives have held meetings to inform members of the communities and public officials surrounding JPL of JPL activities, answer questions, and clear up differing perceptions and understandings. Any community member interested in obtaining information about the site should contact the Public Services Office at JPL.

  25. Comment: Several commenters suggested providing clearer, more legible figures.
  26. Response: The figures have been replaced as suggested.

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