Department of Health & Human Services
Agency for Toxic Substances and Disease Registry
Atlanta GA 30333
January 2, 2009
Thank you for your May 7, 2008, e-mail to the Agency for Toxic Substances and Disease Registry (ATSDR) regarding your concerns about your potential exposure to environmental contaminants released at the Marine Corps Air Station (MCAS), El Toro, California. As you may know, ATSDR received several petitions for MCAS El Toro from former Marines who had been stationed there or, in some instances, their family members. In all cases the petitioners were concerned that Marines who had been stationed at MCAS El Toro, and their family members, may have been exposed to trichloroethylene (TCE) and possibly tetrachioroethylene (PCE) via the base drinking water system. Additionally, some petitioners were concerned that Marines assigned to the Marine Wing Service Group-37 may have been exposed to TCE vapor in the indoor air of hangars #296 and #297 due to a process known as soil vapor intrusion—where contaminants present in the underlying groundwater or soil migrate into the soil gases and then into the indoor air through openings in the building foundation. The majority of the petitioners were stationed at the base for one to four years between 1962 and the early 1990s.
As mentioned in our previous letter, Congress, through the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund) legislation, provided ATSDR with the authority to conduct certain public health assessment activities following a request from a community member. ATSDR conducts these activities to determine whether people have been, or are currently being exposed to hazardous substances released into the environment. We then evaluate whether the exposure is harmful, or potentially harmful, and should therefore be stopped or reduced. It is important to note that ATSDR’s public health assessment activities are not able to determine the cause of an individual’s disease or identify whether a particular exposure caused a disease.
ATSDR’s evaluations are based on the available environmental sampling data. This is an especially important factor when ATSDR is asked to evaluate whether an exposure that may have occurred in the past could have harmed human health. Over the last 20 to 30 years, significant legislative changes have occurred in regulations describing the sampling program required of municipal drinking water providers and the occupational health and safety programs, including indoor air sampling, expected of employers using potentially hazardous materials like TCE and PCE. Prior to the mid-1980’s there were few requirements and limited technical capability to accurately measure solvent concentrations in drinking water or indoor air.
ATSDR worked with the U.S. Environmental Protection Agency (EPA) and the Department of the Navy Base Realignment and Closure Program Management Office West (BRAC PMO) to identify and gather the relevant environmental data for MCAS El Toro. We sought information describing the source of water used for the base’s drinking water needs and the available sampling data describing the contaminant concentrations measured in the groundwater beneath the industrial area used by the Marine Wing Service Group-37, in the base drinking water wells, in the air inside hangars 296 and 297, and in the soil gases beneath the industrial area. This letter describes the type of information ATSDR was able to gather and our review of that information.
The majority of the petitioners were concerned to know whether their drinking water at the base was impacted by groundwater contaminants discovered in the surficial aquifer in 1985. As previously mentioned, before the mid- 1980’s there were no federal guidelines requiring municipal drinking water providers to routinely test the drinking water source areas or the finished water for what are now routinely monitored contaminants such as TCE and PCE.
The Safe Drinking Water Act (SDWA) was originally passed by Congress in 1974. The law was subsequently amended and strengthened in 1986 and 1996. SDWA authorizes EPA to establish health-based standards for naturally-occurring and man-made contaminants found in drinking water. Regulatory requirements to test drinking water resources or finished water for TCE and PCE were not available until the release of the Safe Drinking Water Act of 1986. (To learn more about the Safe Drinking Water Act visit EPA’s website ‘Understanding the Safe Drinking Water Act at http://www.epa.gov/safewater/sdwa/30th/factsheets/understand.html).
Documents provided by Navy BRAC PMO included copies of two contracts regarding the municipal water service to the base. One was signed on July 1, 1969, between the Irvine Ranch Water District, and the Marine Corps Air Station, El Toro and Marine Corps Air Facility (MCAF), Santa Ana. This contract describes the terms by which the water district would provide water to MCAS El Toro and MCAF Santa Ana. In addition the contract indicates the 18-inch water main to be used to supply water to MCAS El Toro had already been built, was in use, and was to be transferred to the Irvine Ranch Water District. The second contract was signed on September 23, 1969, between the Metropolitan Water District of Southern California and the Orange County Municipal Water District. This contract essentially describes the roles and responsibilities of the Metropolitan Water District of Southern California, Orange County Municipal Water District, and the Irvine Ranch Water District as they implement the actions described in the previous contract signed in July. The following paragraphs describe some of the information presented in those two contracts that may be helpful when considering the source of the MCAS El Toro drinking water supply.
In the contract signed on July 1969, the Irvine Ranch Water District agreed to provide MCAS El Toro with treated municipal water to meet an estimated daily demand of 1,730,000 gallons of water (approximately 1,201 gallons per minute). This contract stipulated that the Navy was not obligated to use that much water and that the Navy could use more water. Although the estimated demand was approximately 1,201 gallons per minute, the contract also stipulated that the system would be capable of providing 3,500 gallons per minute under normal conditions.
This contract indicates the water would be delivered to El Toro via one 18-inch water main that enters the facility at the most westerly corner of the base. Although improvements to the water main system leading to the two bases are described in the contract, it is apparent that the 18-inch water main to El Toro was operational before the contract was signed and that the contract transferred ownership of the water main from El Toro to the Irvine Ranch Water District. Additionally, the contract indicates that if the Irvine Ranch Water District was unable to provide water to El Toro, the Irvine Ranch Water District would assist in providing water to El Toro from wells located at the Marine Corps Air Facility, Santa Ana. It appears that this contract was written as a consequence of a change in local ordnances that annexed both the Marine Corps Air Facility, Santa Ana and the Marine Corps Air Station, El Toro into the area served by the Irvine Ranch Water District.
The second contract, signed in September 1969 indicates a previous contract was signed in February 1951 to provide municipal water to El Toro using the 18-inch water main described in the text of the July 1969 contract. Additionally, Navy BRAC PMO provided a copy of one page from the Metropolitan Water District of Southern California 1951 Annual Report. This page indicated that delivery of softened water to El Toro began on June 4, 1951. The initial delivery rate was approximately 447 gallons per minute.
Some petitioners have expressed concern that this initial delivery rate may not have been sufficient to meet the needs of the base and that some of the original base wells may have been used to supplement the base water supply. These concerns stem, in part, from the initial municipal water delivery rate reported in 1951(447 gallons per minute). This delivery rate was approximately 1/3 of the estimated municipal water delivery rate (1,201 gallons per minute) described in the 1969 contract.
It is unfortunate that we can not conclusively determine whether the on-base wells were used to support the base’s water needs after 1951. However it is important to note that the historical documents indicate the 18-inch water main that was available to meet all of the base’s water needs in 1969, was built and operational in 1951. Additionally, the July 1969 contract noted that should the municipal water provider be unable to serve El Toro, they would assist the Government in providing water to El Toro from groundwater wells located at the Marine Corps Air Facility, Santa Ana. This suggests that the wells located at El Toro were not considered viable water supply resources in 1969.
As previously mentioned some petitioners were concerned that Marines assigned to the Marine Wing Service Group-37 may have been exposed to TCE vapor in the indoor air of the hangars due to soil vapor intrusion. ATSDR was unable to identify any sampling data that described the concentration of the TCE in the indoor air of the hangars. As a result it is not possible to conclusively determine whether the indoor air quality of the hangars was impacted by TCE present in the soil or groundwater beneath the buildings.
However, Navy BRAC PMO did provide results of soil vapor sampling conducted between December 1998 and February 1999 for approximately 25 different locations under and around the hangar and other neighboring buildings in this industrial area. Unfortunately, it is not possible to use this data to determine whether the air quality in the hangars was impacted by concentration of TCE measured in the soil gas. The soil gas sampling occurred about the time the base was closing; possibly 20 years or more after TCE use at the base was discontinued. The measured concentrations may not represent those that were present in the soil beneath the hangars while the base was an active facility. The soil gas samples were obtained from a depth of approximately 50 feet below the soil surface. The actual concentrations beneath the foundations of the hangars could have been higher or lower than those measured at the 50 foot depth.
Several petitioners requested that ATSDR conduct modeling studies using the JohnsonEttinger model to estimate the indoor air concentrations based on the TCE concentrations measured in the soil gas. A few petitioners indicated this would be similar to the process we used in our work at Camp Lejeune. It is important to note that ATSDR did not use the Johnson-Ettinger model, or any other model, at Camp Lejeune to estimate indoor air concentrations. Modeling efforts at Camp Lejeune were conducted to estimate the amounts of contaminants escaping from the groundwater to the subsurface soils. This was accomplished to account for volatilization of the TCE from the groundwater, to better estimate the TCE concentration in the Camp Lejeune drinking water supply.
The Johnson-Ettinger model was developed by EPA to serve as a screening level model. It is frequently used to identifr situations where the indoor air of a building could be impacted by the underlying contaminants due to soil vapor intrusion. It is a popular model because it is relatively easy to use and is capable of identifying situations where additional investigations would be recommended to ensure the building occupants are not exposed to harmful levels of contaminants via soil vapor intrusion. (For detailed information about the Johnson-Ettinger model see the EPA website at: http://www.epa.gov/oswer/riskassessment/airmodel/johnsonettinger.htm)
It is important to note though that the model is not recommended to be used to estimate indoor air concentrations in sufficient detail to evaluate occupant exposure to contaminants that may be present in the indoor air. This is for two reasons. First, the accuracy of the model-predicted results depends on how much is known about the underlying geology and the contaminant concentrations. The Johnson-Ettinger model assumes that the soil properties are the same throughout the horizontal plane; however,there can be variations in the soil properties with depth between the various layers. More importantly the model assumes the concentrations of the contaminants within the soil are also the same throughout the horizontal plane beneath the building foundation; and are well known in at least one layer (e.g., the underlying groundwater or soil layer beneath the foundation) for the time period the indoor air concentrations are to be estimated. As previously noted, there is a significant amount of uncertainty concerning the TCE concentration that may have been in the groundwater and especially the soil vapor beneath the hangars while the base was an active facility.
The second reason why ATSDR does not recommend the use of the Johnson-Ettinger model to estimate the potential exposure of hangar occupants is that little is known about the indoor activities that would also have influenced the indoor air concentrations of TCE. These include information on how TCE and other solvents were used, and information on how the building was ventilated. Certain TCE practices such as heating solvents in uncovered vats, or intentionally or indirectly creating airborne droplets of TCE could have increased the indoor air concentrations. Other activities, such as use of vapor capture devices or adequate ventilation, could have reduced the indoor air concentration.
By Congressional statute, ATSDR is authorized to evaluate the potential exposure to environmental contaminants released from a facility. However ATSDR’s authority does not include evaluation of the potential exposure workers may have experienced to the chemicals used in their occupational environment. We have learned that the Navy Marine Corps Public Health Center, Occupation Health Department, does have the authority and appropriate expertise to address occupational exposure issues. If you have concerns about your occupational exposure to TCE while stationed at MCAS El Toro, our colleagues with the Navy recommend that you contact CDR Melissa Mohon at Melissa.Mohon@med.navy.mil.
Some petitioners indicate that they were not specifically assigned to any one portion of the base, but had duties that required them to patrol the entire base. They also are concerned about their potential exposure to TCE. The available information indicates TCE contamination is present in the underlying soil and groundwater in the industrial section of the base (identified as Site 24). ATSDR did not identify any information that indicates TCE was used or stored at other areas of the base, or was present in the environment at other areas of the base. The available information indicates that base personnel and visitors would not be exposed to harmful levels of TCE present in the soil in the industrial section, or any other section of the base.
Several of the petitioners have indicated that they would like for ATSDR to conduct astudy at El Toro similar to that being conducted at Camp Lejeune. ATSDR selected Camp Lejeune to study health effects associated with TCE exposure for several reasons. First the TCE concentrations measured in the drinking water were up to 320 times higher than the federal regulatory standard. As previously mentioned, no data are available to describe whether TCE was present in the drinking water used at El Toro.
Additionally, a significant amount of measured data was available to determine the TCE exposure of base residents and determine which neighborhoods received drinking water with higher versus lower TCE concentrations. As a result, we were able to identify two large groups of individuals; those who were exposed to a well characterized amount of TCE in their drinking water and those who were not exposed to TCE in their drinking water. Large groups, similar as much as possible, with significantly different TCE exposures are likely to produce statistically sound results. Although this study will focus on Camp Lejeune, we believe the results will provide meaningful information to other populations concerned about their exposure to TCE-contaminated drinking water.
As a part of our efforts at Camp Lejeune, ATSDR staff conducted an extensive literature review of the chronic adult health effects possibly linked to TCE exposure in drinking water or by occupational exposure. Based on evidence mostly from occupational studies, a number of health effects were identified for potential follow-up in the Camp Lejeune study: kidney diseases, kidney cancer, liver diseases, liver cancer, non-Hodgkin’s lymphoma, multiple myeloma, cervical cancer, Hodgkin’s disease, Parkinson’s disease, autoimmune diseases such as scieroderma and lupus, and skin disorders. Based on animal evidence, infertility in males and females were also considered for inclusion in the Camp Lejeune study. A complete copy of this literature review “An Assessment of the Feasibility of Conducting Future Epidemiological Studies at USMC Base Camp Lejeune” is available on the ATSDR website at:
http://www.atsdr.cdc.gov/sites/lejeune/docs/feasibility_assessment_Lejeune.pdf.
In summary, ATSDR made the following conclusions regarding MCAS El Toro:
The available information is not sufficient to determine if the on-base drinking water wells were used after 1951 to provide a portion of the base water supply. Additionally, the available information is not sufficient to determine if the wells were impacted by the groundwater contaminant plume present in the industrial area. As a result it is not possible to determine if base-related contaminants were present in the on-base drinking water system prior to 1969.
While it is not possible to conclusively determine whether the on-base wells were used to provide a portion of the base water supply; beginning in 1951 the base had the capability to purchase sufficient water from the municipal water provider.
The available information is not sufficient to determine if the indoor air at the hangars was impacted by TCE present in the underlying soil or groundwater.
Petitioners who are concerned about their potential occupational exposure to TCE while stationed at El Toro are encouraged to contact the Navy Marine Corps Public Health Center, Occupation Health Department.
The available information indicates Marines and their family members were not exposed to harmful levels of TCE present in the soil in any other area of the base.
Finally, each petitioner has indicated that they believe the health conditions they or their family members have experienced are a result of the TCE used on base or present in the environment on base. It is unfortunate to know that so many of our distinguished veterans are facing such difficult health challenges. I share your disappointment that we are not able to provide more detailed information to address your exposure concerns. Unfortunately, there simply is not enough environmental data for ATSDR to conduct public health assessment activities that would provide more information to you than what is in this letter. I trust that when completed, the epidemiological studies conducted at Camp Lejeune will provide more information about the potential health effects from TCE exposure that you will find useful.
Thank you for forwarding your concerns to ATSDR. If you have additional questions, please contact CAPT Susan Neurath, ATSDR Petition Coordinator, at (770) 488-3368 or email SNeurath@cdc.gov.
Sincerely,
William Cibulas Jr., Ph.D.
CAPT, U.S. Public Health Service
Director
Division of Health Assessment and Consultation
cc: Navy Base Realignment and Closure Program Management Office West.(BRAC PMO) Navy Marine Corps Public Health Center, Occupation Health Department
