PUBLIC HEALTH ASSESSMENT
Saipan Capacitors
(a/k/a Tanapag Village (Saipan))
Tanapag Village, Saipan, Commonwealth of the Northern Marianas Island
EPA Facility ID: MPD982524506
August 31, 2004
Releases of polychlorinated biphenyls (PCBs), a hazardous substance, from damaged electrical equipment resulted in widespread environmental contamination in Tanapag village. This electrical equipment was owned by the military in the 1960s, but how exactly this equipment came to Tanapag is unclear. As a result of the PCB releases, people living in Tanapag were concerned about the health and the safety of their families. During investigations, surface soil, biota (animals and plants), surface water and sediment, and groundwater samples were collected and analyzed for PCBs. PCBs were detected primarily in surface soil, and to a lesser extent in sediment and locally harvested foods. Sampling results show that soil and sediment contamination was fairly localized and limited to discrete areas in the village.
The Agency for Toxic Substances and Disease Registry (ATSDR) was asked by the Commonwealth of the Northern Mariana Islands (CNMI) Department of Public Health (DPH) and the U.S. Environmental Protection Agency (EPA), to assist with evaluating village residents' exposure to PCB, determine the extent of public health impact and address community health concerns related to the PCB contamination.
The DPH and ATSDR conducted a health screening in the community. A clinic facility was opened in the village to evaluate exposure to PCB and to examine residents for physical illness related to PCB exposure. Physicians provided complete medical exams to individuals who visited the clinic, and participants were asked to provide a medical history to screen for health conditions and health risk behaviors. Information was collected on participants' health conditions, including cancer, diabetes, and dermatologic problems. The clinical examination included the collection of blood samples for a battery of routine clinical tests. A portion of each blood sample was sent out to specialized commercial laboratories to measure PCB levels in blood serum.
The sum of available evidence indicates that the PCB contamination in Tanapag has not adversely affected the health of village residents. No clinical signs of PCB-related illness was observed in Tanapag residents. However, data gathered at the Tanapag Clinic revealed a number of community health issues including hypertension, diabetes, and obesity. Collection and analysis of serum PCB levels indicated that on average the Tanapag Village population had serum PCB levels within the range of background for the nonoccupationally-exposed U.S. mainland population. It does not appear that the population tested in Tanapag Village are being exposed to PCBs at levels of health concern. Evaluation of the exposure history database revealed that there is insufficient evidence to indicate that contact with PCBs or PCB-contaminated items may have contributed to elevated serum PCB levels.
Contaminated soil has been removed from Tanapag Village, eliminating a major exposure source. As a result of the clean up, the PCB contamination does not pose a current or future health hazard to Tanapag Village residents. Some small degree of exposure may continue if people choose to consume contaminated land crab, however this exposure would not be likely to result in health harm.Releases of polychlorinated biphenyls (PCBs), a hazardous substance, from damaged electrical equipment resulted in widespread environmental contamination in Tanapag village. This electrical equipment was owned by the military in the 1960s, but how exactly this equipment came to Tanapag is unclear. As a result of the PCB releases, people living in Tanapag are concerned about the health and the safety of their families. Additionally, villagers were concerned that the following activities may be harmful:
- living in Tanapag Village,
- eating fish, crabs, and vegetables from Tanapag Lagoon and Tanapag Village,
- breast-feeding babies,
- allowing children to play outside, and
- visiting the village cemeteries.
In addition to developing a joint action plan with local and federal government agencies and community representatives, ATSDR worked with the DPH to establish and staff a clinic in the village. At the clinic, village residents received a thorough medical examination, blood sampling for PCB and a detailed interview to collect exposure history information.
Prior to the current public health assessment document, ATSDR previously released two health consultations related to PCB contamination in the village: 1) evaluation of land crab contamination; and 2) an exposure investigation detailing results of blood serum sampling and analysis for PCB. In the land crab health consultation, ATSDR found that the levels of PCB contamination in the crab are too low to harm people who eat them. In the exposure investigation health consultation, ATSDR determined that the majority of people tested for PCBs in their blood did not have abnormally high levels, and no one had levels high enough to result in health harm.
This health assessment document evaluates possible exposure situations involving PCB, discusses environmental sampling and clean up activities, provides an overview of the health evaluation conducted by ATSDR and DPH and responds to community health concerns about PCB contamination. The Background section presents information gathered when asking questions about the Tanapag Village, village residents, and how PCBs came to the village. The Nature and Extent of Contamination section answers questions about how much PCB has been found in Tanapag Village, where they were found, and what was done to remove them. The Potential Exposure Situations section discusses how people may have contacted PCBs found in their village. The evaluation of public health impact section addresses questions about how contact with PCB might affect the health of villagers.
Additionally, this document summarizes the questions asked and answered by ATSDR in response to villagers' concerns about PCB in Tanapag. As part of the public health assessment process evaluating the health impact of PCB contamination, ATSDR asks a series of questions that focuses on "who, what, where, when, and how" might people contact PCBs released to the village environment. By focusing on these questions, ATSDR gathers information needed to understand how people in the village might contact PCBs, when contact might occur, and how this contact may affect people's health. This information allows ATSDR to then determine the potential impact of the contamination on human health and what actions are appropriate to protect village residents.Where is Tanapag Village?
Tanapag Village is a small town located in the north-central west coast of the island of Saipan in the CNMI (USACE 2002). The CNMI is located in the Pacific Ocean east of Japan (Figure 1). Saipan is the northernmost of the populated islands and was the location of a World War II battle in 1944 (Ogden 1999).
Tanapag Village covers 1.2 square miles along the northwestern shore of Saipan (Figure 2). Tanapag Lagoon forms a beach, which serves as a public park, along the western side of the village. The lagoon also creates the northern boundary of the village. Residential homes, a former Head Start center, church, cemetery, and elementary school are in the village center. A second cemetery and additional residential homes are south of the village center. The Department of Public Works (DPW) Lower Base Yard (LBY) is further south of the village center. Mountains and hillsides are to the east of the village (Ogden 1999; ECC 2002).
Who lives in Tanapag Village?
ATSDR examines demographic data (i.e., population information) to determine the number of people potentially exposed to environmental chemicals. This information is also used to determine the presence of sensitive populations, such as women of childbearing age (age 15-44), children (age 6 and younger), and the elderly (age 65 and older). Demographic data also provide details on population mobility which, in turn, helps ATSDR evaluate how long residents might have been exposed to different substances in their environment.
Tanapag Village is a fishing village with a close community where most families are related, sometimes with as many as four generations living in one household (Prasad 1999). Similar to other villages, the most common occupations for residents include government employment, tourism, fishing, agriculture, and transportation (Ogden 1999; Prasad 1999). Census data show that Tanapag is the smallest village in Saipan with 323 households and a population of 3,318, excluding non-permanent residents and temporary workers such as those employed in garment manufacturing. Approximately 32 percent of residents were born in the CNMI and 64 percent of the population is classified as foreign born, with most of these residents entering the CNMI after 1990. Approximately 32 percent of Tanapag Village residents have lived in the same home since 1995, 14 percent lived in another home in the CNMI in 1995, and 52 percent of the village population reported living outside the CNMI in 1995 (DOC 2002).
Aside from Chalan Kanoa Village, Tanapag has perhaps the largest number of Carolinians on the island of Saipan. Carolinians currently make up 5.2% (3,000) of the total population of Saipan . The ancestors of the Carolinian residents of Tanapag came from Satawal Island, and settled on Saipan between 1810 and 1815 (Ogden 1999; Prasad 1999).
In addition to demographic data, ATSDR also examines land and natural resource information to determine activities that might put people at risk for exposure. This information is important because the types and frequencies of land use activities can affect exposure to contamination. ATSDR uses this information as part of the evaluation of contamination and exposure in this document.
Tanapag's reputation as a fishing village indicates that fish, crab and shellfish contamination can put villagers at increased risk for exposure. Environmental contamination in areas where people visit frequently can result in exposure. Village fishermen keep their boats harbored at Tanapag Beach Park, and frequently gather there for communal fishing trips. The village has a school, church, cemeteries, a Head Start Center and a beach park. Additionally, villagers frequent locations in the village such as baseball fields, basketball courts, a picnic pavilion and other recreational areas (Figure 5).
What are PCBs?
A PCB (polychlorinated biphenyl) is a chlorinated bi-benzene compound which may exist in 209 different forms (called congeners). No natural sources of PCBs are known to exist. PCBs are either oily liquids or solids, colorless to light yellow in color, with no known smell or taste. Some PCBs can be present in the air as a vapor. PCBs are often categorized by their percent weight of chlorine. Some well-known PCB mixtures in the United States go by the trade name Aroclor. PCBs have been used as coolants and lubricants in transformers, capacitors, and other electrical equipment because they do not burn easily and are good insulators. These properties are the reason they were used widely in the electrical transformer manufacturing industry until PCBs were banned in 1977 (ATSDR 2000a).
Use of PCBs and disposal of PCB wastes led to releases of PCBs in the environment, mostly to surface soils. The fate of PCBs in the environment depends on the environmental medium (e.g., air, soil, or water) that is contaminated. PCBs have an affinity for binding to soil and may persist in the soil for many years. This is true for most PCB congeners that contain high amounts of chlorine such as the type released in Tanapag Village. PCBs with lower amounts of chlorine can volatilize (evaporate) from contaminated soil into the air. Since the PCBs in Tanapag soil are weathered (old spills) most if not all of the volatile portion would be gone, and little exposure would be expected from breathing PCB volatiles.
What are health concerns of exposure?
PCBs have been associated with several noncancerous health effects in animals, including liver, thyroid, dermal and ocular changes, immunological alterations, neurodevelopmental changes, reduced birth weight, and reproductive effects (ATSDR 2000a; Tryphonas 1989, 1991; Arnold 1993, 1995; Rice 1997, 1998, 1999; Rice and Hayward 1997, 1999). Studies attempting to show the same health effects in humans that have been observed in animals have generally been inconclusive. Studies of PCB-exposed workers are inherently the most valuable. Exposures to PCBs among workers in some occupations such as manufacture and testing of electrical equipment were very high, and some study populations contain workers with job-related exposures of 20 years or more. Both the magnitude and duration of exposure provides the best opportunity to clearly observe which kinds of effects might reasonably be attributable to PCB exposure.
PCB exposure in the general environment
- People can be exposed to PCBs from ingestion of contaminated food or soil, breathing dust or air containing PCBs, drinking contaminated water or absorbing PCBs through the skin.
- For most people who don't work with PCBs, exposure occurs primarily through ingesting fish, meats and milk containing small amounts of PCB residues.
- Most people in industrialized countries have very small amounts of PCB stored in their body tissues. These background levels of PCBs appear harmless. Over time, our bodies slowly eliminate them. Since PCBs were banned in the late 1970s, levels in the environment, animal foods and human bodies have been slowly declining.
PCBs are known to cause cancer in animals (ATSDR 2000a). However, the evidence that PCBs cause cancer in humans is not as clear. The potential for PCBs to cause cancer in humans has been investigated through human studies that have examined both occupational and environmental exposures. Some studies investigating exposures to PCBs in the work place (usually at much higher levels than what is found in the environment) have been associated with liver, biliary tract, intestinal, and skin cancer while others have found no statistically significant increase in cancer mortality (James 1993; Kimbrough 1995; Brown 1987; Brown and Jones 1981; Gustavsson 1986; Gustavsson P and Hogstedt C. 1997; Bertazzi 1987; NIOSH 1991; Kimbrough RD 1999; Sinks 1992; Kimbrough 1975; Loomis 1997). Although some of these studies did report a positive association, the limitations in the design of these studies and the inconsistency of results from one population to another make it difficult to ascertain whether the observed effects were causally related to PCB exposure.
In contrast to human studies, there is stronger evidence that PCBs cause liver and thyroid cancer in animals (Norback and Weltman 1985; Schaeffer 1984; NCI 1978; Moore 1994; Mayes 1998; GE 1997). Based on sufficient evidence of carcinogenicity in animals, PCBs have been classified as reasonably anticipated to be a human carcinogen by the National Toxicology Program (NTP) and as a probable human carcinogen by the U.S. Environmental Protection Agency (EPA). Although the evidence from animal studies clearly show that PCB exposure at high doses cause liver and thyroid tumors, the weight of evidence from human studies does not support a causal association between PCBs and human cancer (Kimbrough 1995; ATSDR 1997).
When and how did PCBs come to Tanapag Village?
Capacitors containing PCBs were identified as the source of PCB contamination found in Tanapag Village. These capacitors were each 4 feet long, 18-inches in diameter, and about 500 pounds (ACIE 2001b; ECC 2002). Each contained dielectric fluid made of the PCB Aroclor 1254 (ACOE 2001c). The U.S. Department of Defense (DOD) purchased these capacitors in the early 1960s for use on Kwajalein Atoll as part of the Nike-Zeus Radar Transmitter Program (ECC 2002). Later in the 1960s, the capacitors were brought by an unknown source from Kwajalein Atoll to Saipan, stored at the DPW LBY, and released for use in Tanapag Village in 1972 (Ogden 1999; ECC 2002). Reports indicate that the DPW LBY also received capacitors for storage in the 1970s. In 1986, the DPW LBY received capacitors damaged in a typhoon for storage before disposal (Ogden 1999). Whether the capacitors received in the 1970s and in 1986 were the same as those released to Tanapag Village in 1972 or were from other sources is unknown (Ogden 1999).
According to interviews with community members, approximately 50 capacitors were taken from the stockpile at the DPW LBY and given to Tanapag Village in 1972. Residents primarily used the capacitors as a barricade along Tanapag Beach to prevent vehicle entry. Residents also used the capacitors as fences around the cemetery and church, a perimeter around the village ballpark/community hall area, boundary markers, road blocks, cemetery headstones, and cooking pit windbreaks (Ogden 1999; ECC 2002). In the late 1970s, a typhoon hit Saipan and scattered the capacitors throughout Tanapag Village (ACOE 2001b, 2001c).
How did the PCBs spread throughout Tanapag Village?
When the capacitors containing PCBs were given to the village in 1972, the opportunity for PCBs to spread throughout the village was created. At least some of the capacitors given to the village cracked or leaked to start the process of PCBs spreading throughout the village. Capacitors stored in buildings or on concrete pads dripped PCBs to the floors or concrete. Capacitors stored outside on the soil dripped PCBs directly to the surface soil. Once released from the capacitors, the PCBs were able to move through Tanapag Village through either human or environmental means.
People unknowingly helped distribute PCBs throughout Tanapag Village. By excavating soil and transporting this soil to planters and homes in Tanapag Village, PCB-contaminated soil was moved to places were capacitors were never present. Cleaning floors or concrete contaminated with PCBs may have also helped move PCBs to surface soil if the water used to clean the surfaces was allowed to seep into nearby soil. PCBs in the surface soil were then available for transport to other media, such as surface water.
What has been done to understand PCB contamination in Tanapag Village and what has been done to remove PCB contamination?
In 1988, the CNMI Department of Environmental Quality (DEQ) began taking steps to remove the capacitors from Tanapag Village. During removal, CNMI DEQ found that a number of capacitors had leaked and released PCBs to the environment (EPA 2001; ECC 2002). This discovery lead to a number of investigations and removals. DOD assumed responsibility for the contamination that has since been identified at several dozen sites, under the Defense Environmental Restoration Program for Formerly Used Defense Sites (DERP-FUDS) (ACOE 2001b; ECC 2002). The U.S. Army Corps of Engineers (ACOE) has been acting as the executive agent for the DOD's PCB-related clean-up activities in Tanapag (ACOE 2001c).
- 1988-1991. Between 1988 and 1989, CNMI DEQ discovered 16 abandoned capacitors near private residences in Tanapag Village and near the Tanapag Head Start School. Five of the capacitors were reportedly leaking. CNMI DEQ removed 53 capacitors from Tanapag Village and placed them at the DPW LBY in 1988 and 1989. During the initial stabilization and removal activities, CNMI DEQ collected 50 soil samples from areas where the capacitors were located and field tested them for PCBs (ECC 2002). The ACOE collected an additional 44 soil samples and analyzed them for PCBs (Woodward-Clyde 1990). In 1991, CNMI DEQ found and removed two more capacitors from Tanapag Village (ACOE 2001c).
- 1992-1993. Approximately 180 tons of PCB-contaminated soil were excavated from Tanapag Village and the DPW LBY. Soil sampling conducted as part of the PCB soil clean-up revealed that contamination at Tanapag Village was much more extensive than estimated. A combination of poor weather and inability to define the extent of contamination halted the clean-up efforts (Woodward-Clyde 1995; ECC 1999; EPA 2001).
- 1997-1999. Clean-up efforts, with the objective to remove PCB-contaminated soil to below 10 ppm, resumed in 1997. Between August 1997 and February 1999, PCB-contaminated soil was treated using a thermal desorption system set up at the DPW LBY. Approximately 1,181 tons of soil were treated to less than 10 ppm PCBs (EPA 2001). In April 1999, the method of remediating PCB-contaminated soil changed from on-site thermal desorption to transport off site and disposal. A total of 547 tons of PCB-contaminated soil were excavated and shipped to Waste Management Inc. in Port Author, Texas (ECC 1999). A total of 74 tons of potentially dioxin-contaminated soil were removed from three sites, stored at the DPW LBY, and then shipped to Waste Management Inc. in July and August 1999 for incineration (ECC 1999).
As part of the site characterization and post-excavation confirmation during this remediation effort, over 860 surface soil samples were collected and tested for PCBs at 20 locations (capacitor sites). Of the 20 locations, 3 were free of contamination, 16 were remediated to 10 ppm PCB-contaminated soil, and 1 (Cemetery 2) could not be remediated to 10 ppm (ECC 1999; EPA 2001). - 2000. EPA conducted a multi-matrix PCB screening level survey. As part of this survey, EPA collected surface soil, sediment, surface water, groundwater, concrete, and biota (fish, clams, chicken eggs, land crabs, taro root, and yams) (Figure 3). A total of 384 surface soil, 30 sediment, 4 surface water, 21 groundwater, and over 140 biota samples were collected and analyzed for PCBs. Five surface soil samples were also collected and analyzed for dioxins and furans.
No PCBs were detected in any surface water, groundwater, clam, fish, or chicken samples. Trace concentrations of PCBs, well below risk-based consumption limits, were detected in taro root and yams. The study identified approximately 25 surface soil and concrete areas of PCB contamination over 1 ppm. Limited land crab sampling near Cemetery 2 identified PCBs in five of eight crabs collected. No dioxins were detected in any surface soil samples; low levels of furans were detected in the Cemetery 2 area (EPA 2001). - 2001. EPA and CNMI DEQ collected 92 land crabs from four harvest areas near Tanapag Village and a background (reference) location near Smiling Cove. Sampling showed PCBs in land crabs ranging from 0.0007 to 0.9600 ppm with an average of 0.0242 ppm. A few of the crabs were tested for metals. Three metals (iron, aluminum, and manganese) were slightly elevated in some areas. ATSDR estimated the amount of exposure to PCBs and metals from eating large amounts of land crabs for many years and concluded that PCB and metal concentrations in land crab were below levels likely to result in adverse health effects (ATSDR 2001).
- 2000-2003. The ACOE submitted a remediation plan to clean-up Cemetery 2, the 16 sites remediated to 10 ppm in 1997, and 5 additional areas of contamination found during the 2000 sampling event (ECC 2001). Between September 2000 and September 2001, the ACOE removed an estimated 13,236 cubic yards (approximately 20,000 tons) of contaminated soil, debris, and green waste exceeding 1 ppm PCB (ECC 2002). Excavated soil was stockpiled in an enclosure at Cemetery 2 for on-site treatment. After excavation and stockpiling, verification sampling (followed by additional excavation, if necessary) was performed to ensure that contamination was removed to below cleanup goals (ECC 2002). An indirect thermal desorption system operated from October 2001 to June 2003 to treat the contaminated soil. This system treated approximately 42,500 tons of soil, including soil previously excavated and stored at Cemetery 2 and additional soil from Cemetery 1 and Cemetery 2 that contained PCBs over 1 ppm as identified through verification sampling. The ACOE does not specify the amount of additional soil removed from these three sites due to verification sampling in the report summarizing final excavation and treatment activities (ECC 2003). Figure 4 shows the volumes of contaminated soil removed from Tanapag village in 1992, 1997, and 2001 (Ono 2002).
As of April 2002, an estimated 1,300 cubic yards of contaminated soil remained in-situ at Cemetery 2. Several cubic yards of PCB contaminated soil also lay beneath clean coral backfill at Cemetery 1. After excavated soil that has already been stockpiled at Cemetery 2 is treated, the remaining soil will be excavated and treated (ECC 2002).
ATSDR was asked by EPA and the Secretary of Public Health of CNMI DPH to assist in addressing citizens' concerns about health and exposure to PCBs. ATSDR was asked to provide technical consultation in support of DPH's exposure investigation, exposure history, and medical evaluations of Tanapag residents. Following is a summary of ATSDR activities since 1999. Details about ATSDR's activities and involvement at Tanapag Village can be found in Appendix 14.2.
ATSDR visited Tanapag Village to participate in public meetings and listen to community concerns. An ATSDR physician visited Tanapag village and provided information to local physicians on health effects from PCB exposures, exposure history collection methods and information on detecting clinical signs of PCB-related health effects.
ATSDR visited Saipan to participate in public meetings and to communicate the results of the PCB blood sampling and exposure investigation. In addition, ATSDR met with representatives from the EPA Region 9, CNMI DPH, CNMI Division of Fish and Wildlife (under the Department of Lands and Natural Resources), CNMI DEQ, and members of the Tanapag community to identify crab sampling areas and plan logistics for a follow-up round of crab sampling. ATSDR also met with the ACOE to discuss the status of the Army's ongoing removal actions, further sampling, and the installation of protective measures to prevent further contact with contamination, such as access restrictions and air sampling.
ATSDR provided comment on USEPA's environmental sampling plan and multi-agency Tanapag action plan, developed an exposure investigation protocol, exposure history survey and medical evaluations plan in conjunction with CNMI Department of Public Health and local physicians.
The CNMI Department of Public Health set up a health clinic to screen villagers for disease related to PCB exposure and collect blood samples for an exposure investigation. Many Tanapag villagers do not routinely see a physician, and the clinic provided an opportunity for community members to get needed health care services, screen for possible health effects from PCB exposure and collect information about possible routes of PCB exposure to Tanapag residents.
At the request of the CNMI Secretary of Health, ATSDR assisted the CNMI's DPH with its medical evaluation of the residents in the Tanapag Village satellite clinic. ATSDR requested and coordinated assistance in this effort with three health care providers from the Immigration Health Services Division of the Health Resources and Services Administration.
ATSDR staff presented results of the exposure investigation to community members, assisted DPH staff with follow up efforts on medical examinations, and provided training for local health care providers on recognizing the health effects PCB exposure and taking exposure histories. Individuals with elevated serum PCB levels were counseled about the health significance of their blood test results. Other individuals with abnormal lab values or other health concerns were seen in the clinic by an ATSDR physician and local health care providers. ATSDR and DPH staff counseled Tanapag residents who had health concerns about environmental contamination.
Information repositories were established in the local library and Tanapag clinic. ATSDR worked with DPH medical staff to identify data needed to perform a descriptive analysis of disease incidence and mortality in Tanapag. ATSDR also worked with DPH staff to identify what may be needed to develop a future disease surveillance data collection system for Saipan.
ATSDR staff worked extensively with EPA Region 9 to review soil and biota sampling plans and develop fact sheets and flyers. ATSDR then provided assistance to EPA and local health and environment agencies in developing a plan to fill critical data gaps for future sampling and data analysis and provided input into the need for a consumption advisory on crabs. ATSDR also provided technical assistance concerning PCB levels in locally-grown yams and taro.
ATSDR staff provided technical assistance to the ACOE concerning ongoing removal actions. ATSDR met with the ACOE to discuss the status of the ongoing removal actions, further sampling, and installation of protective measures such as access restrictions and air sampling to prevent further contact with contamination. ATSDR also commented on whether the proposed soil cleanup method would produce harmful levels of dioxin byproducts.
ATSDR staff reviewed land crab sampling and analysis data to determine whether the PCB levels pose a public health threat and to define appropriate recommendations for health and regulatory agencies on actions that would mitigate or prevent PCB exposure. ATSDR released a health consultation for PCB contamination in land crabs and determined that the contamination did not pose a public health hazard.
At the request of CNMI DPH, ATSDR assisted with additional blood sampling and PCB congener analysis of a subset of villagers. ATSDR communicated with DPH medical staff about the additional blood sampling results and provided interpretation.
Data Sources and Quality Assurance
In preparing this PHA, ATSDR reviewed and evaluated information provided in the referenced documents. Documents prepared for the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Resource Conservation and Recovery Act (RCRA) programs must meet specific standards for adequate quality assurance and control measures for chain-of-custody procedures, laboratory procedures, and data reporting. The validity of the analyses and conclusions drawn in this PHA are determined by the availability and reliability of the referenced information. Based on our evaluation, ATSDR determined that the quality of environmental data available is adequate to make public health decisions.
