PUBLIC HEALTH ASSESSMENT
PANTEX PLANT
AMARILLO, CARSON COUNTY, TEXAS
The Department of Energy (DOE) Pantex Plant near Amarillo, Texas, does not pose a threat to public health from any site release at this time based on currently available environmental sampling data. No site-related contaminants are currently accessible on- or off-site at levels that would cause adverse health effects. On-site variations have appeared in specific areas of the Pantex Plant; however, monitoring and surveillance off-site did not exceed normal variations. The on-site areas where variations appeared were associated with the burning grounds and the radioactive solid waste management unit. The DOE continues clean-up activities at the Pantex Plant with oversight provided by the Texas Natural Resources Conservation Commission and the Texas Department of Health (TDH).
In evaluating residents' public health concerns, the Agency for Toxic Substances and Disease Registry (ATSDR) obtained the assistance of the TDH Bureau of Epidemiology. A synopsis of the evaluation of residents' concerns follows. Residents raised questions about excessive cancer rates in Carson, Potter, Randall, and Armstrong counties, excessive birth defects, and other adverse health effects they believed to be related to environmental releases from the site. Although the number of cases and/or deaths reported for some types of cancers in those counties may be higher than what would be expected based on comparison with numbers for other populations, an ATSDR review of available environmental data indicated that it is unlikely that area residents come into contact with significant enough amounts of chemicals or radioactive substances from the plant to cause adverse health effects. Thus, the Pantex Plant is probably not the cause of the higher than expected levels of cancer found in this area. The concern that the occurrence of birth defects was elevated in the counties surrounding Pantex required the evaluation of information obtained from birth certificates, fetal death certificates, and infant death certificates. The number of children born in this area with certain categories of birth defects appears to be higher than what would be expected based on similar birth defect information obtained for the entire State. To determine an underlying cause for the apparent increase, TDH evaluated parental occupation and place of employment as well as distribution of the birth defects by zip code. No occupations or workplaces for mothers or fathers were notable. Very few parents of children reported to have been born with birth defects worked at the Pantex facility. Additionally, although one zip code near the plant (79107, which extends from the western edge of the Pantex Plant along the Potter County/Carson County border towards Amarillo) showed significant elevations for several birth defect categories, there was no consistent pattern among zip codes showing that closer proximity to Pantex increased the risk of birth defects.
An investigation of the incidence of low birthweight babies concluded that although there was an increase in Armstrong County, there was no pattern that would suggest that proximity to the Pantex Plant increased the risk of having a low birthweight baby. An evaluation of the number of people with muscular dystrophy, multiple sclerosis, amyotrophic lateral sclerosis, and lupus erythematosus in the area indicated a higher than expected number of deaths from all but lupus erythematosus. There was no consistent pattern of deaths from these diseases in the four-county area. In some instances, the number of deaths due to these diseases was elevated for males and not females; in other instances, the reverse was true. The causes of many of these diseases are not clearly understood. Detailed answers to questions about patterns of disease occurrence follow.
1. Is there a higher than expected number of birth defects in this area?
Possibly. Using information obtained from birth certificates, fetal death certificates, and infant death certificates, the Texas Department of Health Birth Defects Monitoring Division (TBDMD) found that the observed cases and/or deaths reported for several categories of birth defects in this area are higher than what would be expected based on comparison to State rates. Specifically, the TBDMD looked at birth defect information for Armstrong, Carson, Potter, and Randall counties for the years 1990 to 1994 and found the following:
birth certificate information showed that several categories of birth defects were significantly elevated in specific counties and in the four counties grouped together, fetal death certificate information showed a statistically significant excess of hydrocephalus in Carson County and a statistically significant excess of "other congenital anomalies" in Potter County, and infant death certificate information showed a statistically significant excess in two major heart defects in Carson County.
Should the public be worried about these results, and what do they mean?
The public should not be worried. In some instances, even though the results are statistically significant, they are based on few observed cases and wide confidence intervals. Thus, we would not interpret these results as indicating an increased risk for birth defects. In other instances, the birth defect categories were nonspecific. Because these categories include many different types of defects, it is impossible to determine whether the increase is the result of slight (nonsignificant) elevations among several types of defects or the result of a large increase in one or two defects.
For Potter County, Randall County, Potter and Randall counties combined, and the combined four-county area, several of the clinically specific birth defect categories appeared elevated. Although we are fairly certain that these statistical findings are real and not solely due to chance, there are other possible explanations for these results.
One possible explanation for the higher than expected number of reported birth defects in this area is that compared to those in other areas of the State, local health care providers may be more careful to report birth defects on the birth certificates. When a child is born with a birth defect, attending health care providers or hospital personnel may indicate the presence of a birth defect by checking off 1 of 23 categories of birth defects listed on the birth certificate. In an attempt to rule out better reporting as a possible explanation for the apparently higher number of reported birth defects, the TBDMD compared the reports of birth defects from this area to what would be expected based on the experience of two active surveillance systems (California and Atlanta). Active surveillance systems are best at capturing the true occurrence of disease in populations. In these systems, public health workers visit hospitals and other health care facilities to review and record pertinent information from medical records. Using information from these systems for comparison, no statistically significant excesses in reported birth defects were found in the four counties. Thus, we cannot rule out better reporting as a possible explanation for the apparently higher than expected number of birth defects reported for this area. However, we cannot rule out the possibility that the apparent excess is real.
2. Could the Pantex Plant be the cause of the higher number of birth defects observed?
Not likely. ATSDR review of available environmental data indicates that it is unlikely that residents are coming into contact with significant amounts of chemicals or radioactive substances from the Pantex Plant. Thus, it is not likely that the Pantex Plant is associated with these results. Currently, the causes of two-thirds of birth defects remain unknown. Many birth defects have a multifactoral etiology, meaning that a variety of both genetic and environmental (diet, lifestyle, and occupational) factors play a role. For example, microcephaly may be caused by one of several inherited syndromes or by degenerative brain disorder, birth trauma, intrauterine infection, or exposure to X rays in utero. The causes of tracheo-esophageal fistula, cleft lip, cleft palate, and club foot are thought to be multifactoral. Esophageal atresia is thought to arise from a random, generalized insult to embryogenesis. Most cases of polydactyly or syndactyly have a genetic cause. The wide range of birth defects for which statistically significant excesses were noted argues against a single causative physical or chemical agent.
In an attempt to better answer this question, TBDMD did a subsequent analysis of the birth defect information obtained from the birth certificates. Specifically, staff looked at parental occupation and place of employment as well as the distribution of the birth defects by zip code. There were no occupations or workplaces that seemed unusual for mothers or fathers. Several fathers of children with birth defects worked in meat processing, but this is common in Amarillo. Very few parents of children reported to have been born with birth defects worked at the Pantex Plant. Additionally, although one zip code near the plant (79107) had significant elevations for several birth defect categories, other zip code areas also had significant elevations; there was no consistent pattern showing that closer proximity to Pantex increased the risk of birth defects. Fastidious reporting practices by the hospital that delivers the majority of live births in this area could explain these results.
3. Is there a higher than expected number of low birthweight babies born in this area?
Yes, in Carson and Potter counties. Information obtained from birth certificates (1990-1994) indicates the rate of low birthweight babies born in Carson and Potter counties was higher than the rate reported for the State of Texas. However, the rate of low birthweight babies born in the other two counties (Randall and Armstrong counties) was not significantly different from the rate for Texas.
Should the public be worried about these results?
The public should not be worried. The higher than usual rate of low birthweight babies born in Carson and Potter counties could in part be the result of the reporting practices of the hospital that delivers the majority of babies in this area. Northwest Texas Hospital strictly adheres to the policy of the Texas Department of Health to file a birth certificate for all live births regardless of gestational age, and previous discussions with hospital staff indicate that all infants with any life signs, regardless of gestational age, are considered live births. The practice of reporting very premature births as live births may not be uniform throughout the State. Some hospitals may report very premature births as fetal deaths, and some may not report premature births with gestational ages less than 20 weeks.
4. Could the Pantex Plant be the cause of the higher rate of low birthweight babies?
Not likely. Although reporting practices may not completely explain the elevated rates for this area, there are several risk factors that increase a woman's chances of giving birth to a baby born with a low birthweight. Mothers who smoke, drink alcohol, use illicit drugs, or have poor nutritional habits during pregnancy may have an increased risk for low birthweight babies. In addition, maternal age and the number of previous live births are other examples of factors that can have an effect on the developing fetus. In summary, there are many factors, some of which can be controlled by the mother and others that cannot, that play an important role in the health of the developing fetus.
There was no pattern observed that would suggest that proximity to the Pantex Plant increased the risk of having a low birthweight baby. Additionally, an ATSDR review of available environmental data indicates that it is unlikely that residents are coming into contact with significant amounts of chemicals or radioactive substances from the Pantex Plant. Thus, it is not likely that the Pantex Plant is associated with these results.
5. Is there a higher than normal amount of cancer in this area of the State?
Yes, for some types of cancer. The number of cases and/or deaths reported for some types of cancers in this area may be higher than what would be expected based on comparison with other populations. The Texas Department of Health Texas Cancer Registry (TCR) looked at cancer records for Armstrong, Carson, Potter, and Randall counties and found statistically significant excesses for some types of cancer. Specifically, the TCR looked at records for lung, bone, prostate, breast, brain, and thyroid cancer, leukemia, and all types of cancer combined and found the following:
a higher than expected number of females who have cancer (all types combined) in the combined Potter/Randall counties area;
a higher than expected number of males who have chronic lymphocytic leukemia in the combined Potter/Randall counties area;
a higher than expected number of males who died from prostate cancer in Potter and Randall counties; and
a higher than expected number of males who died from cancer (all types combined) in Potter County.
Should the public be worried about these findings, and what do they mean?
The public should not be worried. The higher than expected number of females with cancer (all types combined) in the combined Potter/Randall counties area and the higher than expected number of males who died from cancer (all types combined) in Potter County are difficult to evaluate with any degree of certainty. The excesses are small and the categories are nonspecific and include all types of cancer. The results could be the result of slight (nonsignificant) elevations among many different types of cancer or the result of moderate (nonsignificant) increases in one or two cancer site locations.
The higher than expected number of males with chronic lymphocytic leukemia (CLL) in the combined Potter/Randall counties area may be noteworthy. In a previous investigation, the TCR found a slight excess of CLL among females from this area. The causes of CLL are not known, and although there is some evidence that there may be an inherited susceptibility component to this disease, it is our opinion that the significant excess of CLL deserves further investigation.
The higher than expected number of males from Potter and Randall counties who died from prostate cancer also is noteworthy and deserves further attention. The fact that a higher number of males who have prostate cancer was not found suggests that late detection and treatment of this disease may be contributing to the higher number of deaths from this disease. Increased awareness and attempts to improve the early periodic screening for this disease in this area may be needed.
6. Could the Pantex Plant be the cause of the higher than expected number of people with cancer that the TCR observed?
Not likely. Cancer is a very common disease, much more common than most people realize. Approximately four out of every ten persons alive today will develop some type of cancer in their lifetime. Furthermore, cancer is not one disease, but many different diseases. Different types of cancer are generally thought to have different causes. In Texas, as in the United States, cancer is the second leading cause of death, exceeded only by heart disease. In 1995, Texas reported 31,571 cancer deaths. Sixty-five percent of these deaths were of persons 65 years of age or older. Finally, it takes time for cancer to develop, usually 20 to 40 years. The occurrence of cancer may vary by race/ethnicity, gender, the type of cancer, geographic distribution, population under study, and a variety of other factors. Scientific studies have identified a number of factors for various cancers that may increase an individual's risk of developing a specific type of cancer. These factors are known as risk factors and include the following: heredity, diet, age (cancer risk increases with age), family history, exposure to certain chemicals (only a limited number of chemicals show definite evidence of human carcinogenicity, e.g., benzene, asbestos, vinyl chloride, arsenic, aflatoxin), radiation (ionizing radiation and ultraviolet radiation), alcohol, and tobacco smoke.
The chances of a person developing cancer as a result of exposure to an environmental contaminant are actually slight. Tobacco use and diet are estimated to cause 30% and 35% of all cancer deaths respectively or 65% total for all cancer deaths. Pollution and occupational exposures collectively are estimated to cause 4-6% of all cancer deaths.
A careful review of available environmental data by ATSDR indicates that it is unlikely that area residents are coming into contact with significant amounts of chemicals or radioactive substances from the Pantex Plant. Thus, the Pantex Plant is probably not the cause of the higher than expected levels of cancer found in this area.
7. Is there a higher than usual number of people with muscular dystrophy, multiple sclerosis, amyotrophic lateral sclerosis, and lupus erythematosus in this area?
Possibly. Because these diseases are not reportable in Texas, the Texas Department of Health (TDH) was not able to determine the number of people who have these diseases; however, to try to answer this question, the TDH reviewed death certificates from this area to determine how many people died from each of the diseases. The TDH did find a higher than expected number of deaths from some of these diseases for this time period. In Carson and Potter counties, a higher than expected number of males died from muscular dystrophy. In Randall County, a higher than expected number of females died from multiple sclerosis. In Potter and Randall counties combined there was a higher than expected number of females who died from multiple sclerosis and a higher than expected number of males died from amyotrophic lateral sclerosis. Deaths due to lupus erythematosus were not found to be higher in any of the four counties investigated.
Should the public be worried about these results?
Probably not. Incidence data were not available for these diseases; therefore, we used mortality data. For several reasons, mortality data may not be a good indicator of the actual occurrence of these diseases in the population. Individuals may live for many years with these and other chronic diseases, and death may ultimately result from other causes. Caution must be exercised when interpreting the elevations in the four-county area. All of the counties are sparsely populated, and even one additional death can result in an elevated mortality ratio.
Because of the nature of these data, we are not able to provide, with any degree of certainty, a meaningful interpretation. The causes associated with each of these diseases are still very speculative.
For muscular dystrophy, genetics is a major risk factor. This means that individuals who have relatives with the disease may have a greater chance of developing the disease themselves.
Multiple sclerosis, like muscular dystrophy, also may have a genetic component associated with its development. In addition, other factors that potentially have been associated with this disease include exposure to viral agents, country of origin, exposure to heavy metals, and being female.
Several possible risk factors that may be associated with amyotrophic lateral sclerosis (ALS) have been discussed in the scientific and medical literature. Genetics, prior trauma, heavy milk consumption, heavy physical labor, occupational exposure to chemicals involved in the manufacture of plastics, and exposure to infectious agents before the onset of disease all have been implicated in the development of ALS.
Lupus erythematosus also has a strong genetic association with its development. In addition, exposure to specific chemicals and toxins, dietary factors, and exposure to infectious agents before the onset of disease have been associated with lupus.
8. Could the Pantex Plant be the cause of the higher than usual number of deaths from muscular dystrophy, multiple sclerosis, and amyotrophic lateral sclerosis, observed in this area?
Not likely. There was no consistent pattern of deaths due to these diseases found in the four- county area. In some instances, the number of deaths due to these diseases was elevated for males and not females; in other instances, the reverse was true. The causes of many of these diseases are not clearly understood. Additionally, ATSDR did not find any evidence that area residents are coming into contact with significant amounts of chemicals or radioactive substances from the Pantex Plant.
9. What are the potential health effects of gaseous tritium releases (the last one recorded in 1989)?
In 1982, more tritium was released to the atmosphere than in previous years. In 1982, the maximum levels of tritium in air ranged from 0.059 - 0.24 Bq/m3 (1.6 - 6.4 pCi/m3). Although there was more tritium released than usual, the estimated doses were less than the radiation exposure from the normal background (natural radiation sources). In 1985, elevated levels of tritium were detected off site; however, the levels were still below levels that would cause adverse health effects and, for comparison, below levels of NRC compliance.
A major release of tritium from the assembly area occurred in 1989. Dose assessments developed by the Department of Energy (DOE) and reevaluated by Battelle in 1994 suggested that tritium doses were well below levels known to cause adverse health effects. As late as 1994, continuously decreasing doses of tritium continued to be released from the dome and surrounding soil. The Battelle reassessment of the tritium release model used indicates that doses from 1990 to 1992 ranged from 4 to 70 x 10-6 mrem. The greatest contributors to those doses were fruits and nonleafy vegetables. Air monitoring for radionuclides (uranium [U], plutonium [Pu], and tritium) in the 1990s shows the atmospheric concentrations of the U and Pu radionuclides to be at levels that would not cause adverse health effects. Comparisons of air concentrations around Pantex with those for Austin and El Paso, Texas, show the air around Pantex actually contains less radiological contaminants than the air in those two cities.
Tritium concentrations have been elevated around Pantex in the past as a result of a major release in May 1989. The elevated tritium levels, however, have not resulted in radiation exposures or doses above levels that would cause adverse health effects.
10. Is contamination from the Pantex Plant entering private and/or municipal wells?
Although chemical contamination above screening values has been detected in the perched aquifer at the southeastern plant boundary, that particular perched aquifer is not used as a water source downgradient of the contaminant plume. If used as a water source in the future, water from that perched aquifer would require treatment to remove contamination before it would be safe for consumption. Chemical contamination above screening values has not been detected in the Ogallala aquifer, which is used as a drinking water source throughout the region. Samples from the Pantex Plant production wells are used as a secondary check for possible chemical migration from the perched aquifer into the Ogallala aquifer. If contamination of the Ogallala aquifer were to occur as a result of Pantex Plant operations, it would appear first in the production wells. The Pantex Plant production wells, therefore, serve as interceptor wells for the downgradient City of Amarillo drinking water production wells. The Pantex Plant and City of Amarillo production wells are also monitored in accordance with Safe Drinking Water Act requirements for source water. Monthly sampling of an additional off-site water quality monitoring station, the water supply at Bushland, Texas, provide control data for comparison with data from the plant. This control well is completed in the Ogallala aquifer upgradient from Pantex Plant and is not affected by plant operations.
11. What is the potential for airborne exposure as a result of open burning and dispersal of explosive residues and sediments from Pantex dry surface impoundments?
The Pantex Plant has a state-issued permit that provides limits on burning at the burning ground. Before the permit was issued, an air dispersion model calculated that the permit limits would protect public health and the environment. In addition, the permit requires monitoring of air, soils, vegetation, surface water, and groundwater. This monitoring has shown that burning has not resulted in releases outside the burning ground.
The entire burning ground was identified as multiple solid waste management units (SWMUs). The environmental investigations concentrated on the old solvent evaporation pit and the landfills. In addition, surface soil samples were taken around the burn pads and the burning ground complex. The sample results showed higher than background levels for explosives, and those areas with the highest levels are scheduled for cleanup in calendar year 1998. Because the area is covered with grass, movement of the explosives will occur only if the land is disturbed.
The 11-14 SWMU pond liner and sediments were removed and replaced with clean soil in the former impoundment. The surface impoundment at SWMU FS-16 was also removed and filled with clean soil.
Environmental investigation fieldwork was completed in 1995 for playas 1, 2, 3, and 4 and Pantex Lake. Surface and subsurface soils were sampled, and the results for all substances except arsenic and beryllium were within environmental guidelines; however, the amounts of these two materials were at or below background levels in soils normally found in similar playas in the geographic area.
12. Can asbestos from the asbestos disposal area in the northeastern corner of the plant blow off site?
Landfills 1 and 2 are in the northeastern corner of the plant. Although asbestos was put in Landfill 1, vegetation covering the area prevents release to the air. Landfill 2 has no confirmed asbestos material based on results of the RCRA Facility Investigation. The Landfill 1 maintenance cover, which consists of a 2-foot thick, compacted soil cover, a 6-inch thick topsoil layer and vegetation, has not been disturbed or plowed and is not grazed. It was originally seeded with a mixture of hard red winter wheat, Blue Gramma, and Sideoats Gramma.
13. What is the public health impact of previous discharge of waste waters from Pantex and the old Air Force base to Pantex Lake, an off-site, naturally occurring playa northeast of the plant?
Pantex Lake received discharges from the Old Sewage Treatment Plant via an underground pipeline from 1942 until late 1970 or early 1971. An environmental investigation of the treatment plant, which included the sludge drying beds, recommended no further action.
Environmental samples were collected beginning around 1970. The 1995 results showed the water at Pantex Lake to
be similar to that in the other playas. Samples were checked for radionuclides, metals, and water quality indicators.
II.A Site Description and History
The Pantex Plant Department of Energy (DOE) site was proposed for the Environmental Protection Agency's (EPA) National Priorities List (NPL) in July 1991. In August 1991, representatives of Panhandle Area Neighbors and Landowners (PANAL), Peace Farm, Serious Texans Against Nuclear Dumping (STAND), and the Texas Nuclear Waste Task Force petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a public health assessment of the Pantex Plant; however, because of the proposed listing, ATSDR was already mandated to conduct a public health assessment of the site. The site was subsequently officially added to the NPL in May 1994.
Pantex Plant is located in the panhandle of Texas in Carson County, approximately 17 miles northeast of downtown Amarillo and 9 miles west of the town of Panhandle. The Pantex Plant boundaries are U.S. 60 to the south, Texas Farm-to-Market (FM) Road 293 to the north, FM 683 to the west, and FM 2373 to the east.(1) Figure 1 shows the location of the Pantex Plant.
The Pantex Plant site is primarily flat and is situated on the Southern High Plains at an elevation of approximately 3,540 feet. The site is characterized as mixed prairie of native and introduced grasses. Rainwater and snow melt feed natural playas. Playa 1 also receives effluent from the primary sewage treatment lagoon. The areas adjacent to Pantex Plant are primarily agricultural with typical farm residences.(2)
The Pantex Plant is owned by the U.S. Department of Energy and operated under contract by Mason and Hangar Corporation. The plant is on a 16,000 acre (10,000 acres DOE owned with 6,000 acres leased as a security buffer from Texas Technological University) portion of the former Pantex Army Ordnance Plant. The Pantex Army Ordnance Plant was constructed in the first half of the 1940s by the U.S. Army for the production of conventional ordnance. The plant was deactivated at the end of World War II, and the property eventually reverted to the War Assets Administration. In 1949, the entire installation was sold to Texas Technological College for one dollar. The land was to be used for experimental farming but was subject to recall under the National Security Clause. The Atomic Energy Commission (AEC) chose the site for expansion of its nuclear weapons assembly facilities in 1951. The Army Ordnance Corps reclaimed 10,000 acres of the site for the AEC and contracted the Silas Mason Company to rehabilitate it.(1)
According to DOE, the Pantex Plant Mission is to anticipate and satisfy U.S. Department of Energy requirements by providing competitive, quality, on-time products and services that exceed expectations and are achieved in a manner that protects the environment, ensures the safety and health of employees and the public, and protects our national security. Pantex Plant's primary mission is to: assemble nuclear weapons for the nation's stockpile, disassemble nuclear weapons being retired from the stockpile, evaluate, repair, and retrofit nuclear weapons in the stockpile, demilitarize and sanitize components from dismantled nuclear weapons, provide interim storage for plutonium pits from dismantled nuclear weapons, and develop, fabricate and test chemical explosives and explosive components for nuclear weapons, and support DOE initiatives.
The chemical explosives and explosive components are shipped to the Pantex Plant and fabricated into the required shapes for use in nuclear weapons. Other manufacturers supply all other nuclear weapons components. The Pantex Plant assembles the components to produce nuclear weapons for the Department of Defense.
Maintenance and modification of weapons in the military stockpile involve partial disassembly to permit replacement, modification, or inspection of components. A statistically selected number of nuclear weapons from the military stockpile or from initial production of a new weapons system receives a series of inspections and component evaluations.
When a weapon is completely disassembled for retirement, the Pantex Plant separates the chemical explosives and explosive components from the nuclear components. The recovered material is, where appropriate, offered for sale to external vendors for their use. A small fraction of the recovered explosives is thermally treated. The plutonium pits are stored in the magazines in Zone 4. The plant returns all other components to their manufacturers or sends them elsewhere for reuse, salvage, or ultimate disposal. The Pantex Plant also conducts research and development work on conventional high explosives to support weapons design and development programs for the Department of Energy.
The plant is divided into several major working areas. The manufacturing area fabricates high-explosive components and weapon assembly/disassembly operations. The high-explosives development area supports various DOE nuclear weapons design agencies. The temporary holding area is a safe, secure place for high explosives and nuclear weapons on which no active work is under way. Other important facilities include test-firing sites for testing high explosives, a landfill disposal area, a burning ground for treatment of explosives, a water treatment plant, a steam generation plant, and a sewage treatment plant.
Pantex Plant includes short-grass prairie, a buffer zone used for agriculture, and four playas on the 4,119 hectares (10,177 acres) of DOE-owned land including Pantex Lake, and two playas on the 2,370 hectares (5,800 acres) of land leased from Texas Tech University. The DOE-owned land includes approximately 1,216 hectares (3,004 acres) dedicated to industrial operations (e.g., buildings, roads, parking areas, and mowed grass areas: 1,747 hectares (4,317 acres) under cultivation; and 720 hectares (1,779 acres) used for domestic livestock grazing). The 436 hectares (1,077 acres) at Pantex Lake are used for domestic livestock grazing and farming.(2)
Representatives of the Agency for Toxic Substances and Disease Registry (ATSDR) first visited the Pantex facility December 2-5, 1991, as part of a program to evaluate Department of Energy (DOE) National Priorities List (NPL) sites and develop a sequential workplan to address those sites. Agency staff members used the site-ranking scheme published in the Federal Register (57 FR 37382) to rank each of the DOE sites. Rankings established the basis for a relative order for the efficient application of limited personnel and budget resources. The Pantex Plant's ranking, compared with rankings of other national DOE sites, qualified it for initiation of a public health assessment in 1995. ATSDR conducted a subsequent site visit September 11-14, 1995, to obtain information for conducting the scheduled public health assessment of the Pantex Plant. During that visit, ATSDR staff members met with representatives of the Texas Natural Resources Conservation Commission (TNRCC) and the Pantex Plant Citizens' Advisory Board (PPCAB) Planning and Training Subcommittee. ATSDR staff members also attended on-site briefings by Pantex Environmental staff members, toured the site, and reviewed historical documents pertaining to environmental sampling and remediation activities.
ATSDR staff briefed the full membership of the PPCAB on September 26, 1995 on ATSDR's mission and how the Pantex Public Health Assessment would be conducted. ATSDR staff provided subsequent presentations to the PPCAB on February 27, March 26, April 30, August 27, September 24, November 26, 1996 and July 22, 1997 on the progress of the health assessment.
ATSDR held public meetings the first week in March 1998 to present the Pantex Plant Public Health Assessment and gather public comments on the health assessment. Meetings were held at the War Memorial Building in Panhandle, Texas (March 2nd and 3rd); Vickie's Grill on Highway 136 in Amarillo, Texas (March 3rd); the Amarillo Central Library (March 4th); and the Amarillo Association of Realtors Building (March 5th). Approximately 21 community members attended the public meetings.
II.C Demographics, Land Use, and Regional Hydrogeology
Summary Population Statistics Methodology: The potentially impacted site area was spatially defined as the area within the site boundary plus a one-mile buffer around that boundary. A one-mile buffer is useful for conveying information about the demographic structure of the area adjacent to the site and identifies those who might have a greater potential for exposure. It is important to note, however, that proximity, in itself, is not an adequate indicator of exposure to site-related contaminants. Proximity measures must be supplemented with environmental pathway information to evaluate exposed populations.
The Agency for Toxic Substances and Disease Registry (ATSDR) used an "area proportion" technique to calculate the summary population statistics presented. When combining census blocks with buffer distances, the periphery of the obtained boundary commonly intersects a census block. In such cases, applying an area weight factor to the population variables of interest is arguably the best choice for collecting site-specific demographic population data. The population in a census block is weighted to reflect the proportion of the block area that is actually in the buffered site area. This method assumes that the population is uniformly distributed throughout the block.
ATSDR demographic data sources are:
U.S. Bureau of the Census. 1990. Public Law 94-171 [machine-readable data files]. The Bureau, Washington, D.C.
U.S. Bureau of the Census. 1991. Census of Population and Housing, Summary Tape File 1 [machine-readable data files]. The Bureau, Washington, D.C.
U.S. Bureau of the Census. 1991. TIGER/Line Census Files on CD-ROM [machine-readable data files]. The Bureau, Washington, D.C.
U.S. Bureau of the Census. 1992. TIGER/Line Census Files on CD-ROM [machine-readable data files]. The Bureau, Washington, D.C.
Regional Demography: The 1990 census of the residential population surrounding Pantex Plant showed that most of the population is located west-southwest of the Pantex Plant in the Amarillo metropolitan area. Figures 2 through 11 show the population density and distribution for the following demographic variables: one mile site buffer, from 10 to 25 miles from the site boundary, and for susceptible populations such as children 6 years and younger, females aged 15 to 44, and adults 65 and older. The cumulative population within a 1, 5, 10, and 25 mile radius of the Pantex Plant was 36, 413, 6138, and 200857 respectively.
As of the 1990 Census, Amarillo had 157,615 residents. Pampa, Texas, located about 40 miles east-northeast of the Pantex Plant, is the second largest population concentration, with about 21,000 residents. The remaining population within the 25 mile radius is fairly evenly distributed at a density of about three people per square mile.(3)
The cultural and ethnic origins in the region are diverse, although historical trends are still reflected in the overall population composition. The population is predominantly white, with origins back to early settlers who relocated from the eastern U.S. and who were primarily European. Persons of Hispanic origin comprise the second largest group in the area.(4)
Land Use: The area around Pantex Plant is semiarid. Land is used mainly for farming and ranching. Although dryland farming is dominant, some fields are irrigated from the Ogallala aquifer or, less commonly, from local playas. Ranching in the region is primarily cow-calf operations. Several significant industrial facilities are located in the general area, including two electric power plants, a copper refinery, a beef packing plant, and the Amarillo International Airport with associated industries.(3)
Regional Hydrogeology: The land surface in the vicinity of the Pantex Plant is relatively flat and is dominated by shallow ephemeral lakes called playas. All surface drainage flows into these playas, of which 4 are located within the DOE-owned Pantex Plant boundaries. Rainfall averages between 18 and 20 inches/year; however, surface evaporation is up to five times greater than precipitation. Surficial deposits in the Pantex area are composed of Quaternary and Recent Eolian deposits (well sorted, fine grained sands and clays) that contain concentrations of clay and carbonate.
Two aquifers, the Dockum Group aquifer and the Ogallala aquifer, are present in the region. The Dockum Group aquifer occurs at depths varying between 350 and 700 feet below ground surface in the region. Little recharge of the Dockum Group aquifer occurs in the Pantex area (less than 1 inch per year), and the potentiometric surface has not been established in this area. The direction of flow may be towards the southwest, but the hydraulic gradients have not been determined. In most of the region, the Dockum Group aquifer is thought to be semi-confined and hydraulically separated from the overlying Ogallala aquifer. In the Pantex vicinity, however, the confining units are missing, and the two aquifers are thought to be hydraulically connected.
The Ogallala aquifer occurs in permeable sediments comprising the basal portion of the Ogallala Formation, which have an average potential hydraulic conductivity of 22.5 feet/day. The Ogallala aquifer is unconfined in this region and occurs at depths between 280 and 460 feet with overall thicknesses of 50 to more than 350 feet in the Pantex vicinity. The regional gradient of the Ogallala is to the southeast and is locally different in the vicinity of Pantex Plant in that the gradient is east to northeast. Pumping at the City of Amarillo wellfield (just north of the Pantex Plant) has caused the shift in groundwater flow. Pumpage exceeds recharge by a factor of 24 and the net result is that pumping of the Ogallala aquifer has lowered the static level of the aquifer by about 2 feet/year. Recharge to the Ogallala aquifer occurs at a rate of less than 1 inch per year from vertical leakage in high permeability areas and preferential pathways from the playa basins. The central portions of the playas are underlain by relatively thick, impermeable clays. During infrequent, heavy rainfalls, playa water levels exceed the central areas and move downward and recharge the underlying aquifer. Where impermeable units, predominantly clay, are present at depth, downward flow is restricted and areas of perched water are present. On-site at the Pantex Plant, perched groundwater with saturated thicknesses of 0 - 75 feet at depths between 210 and 300 feet BGL (below ground level, as opposed to below MSL--mean sea level--a different reference data point) has been identified through the installation of 67 perched aquifer wells. The direction of flow for the perched groundwater is radially outwards from Playa 1 and Zone 12 with the major flow component to the southeast.(5)
Figure 2. Demographic Variables in 1, 5, 10 and 25 Mile Increments from Site Boundary
Figure 3. Demographic Statistics Selected from a 1 Mile Site Buffer
Figure 5. Total Population Density and Distribution 25 Miles from Site Boundary
Figure 6. Population of Children 6 Years and Younger in 1, 5 and 10 Mile Increments from Site Boundary
Figure 7: Population of Children 6 Years and Younger 25 Miles from Site Boundary
Figure 8: Population of Females Aged 15 - 44 in 1, 5 and 10 Mile Increments from Site Boundary
Figure 9: Population of Children 6 Years and Younger 25 Miles from
Site Boundary
Figure 10: Population of Adults 65 Years and Older in 1, 5 and 10 Mile Increments from Site Boundary
Figure 11: Population of Adults 65 Years and Older 25 Miles from Site Boundary
III. COMMUNITY HEALTH CONCERNS
Agency for Toxic Substances and Disease Registry (ATSDR) and Texas Department of Health (TDH) staff evaluated community health concerns as part of the public health assessment process. Staff identified the following community health concerns during meetings with concerned residents in April, June, and August, 1996:
perceived increase in the incidence of birth defects, low birthweight, muscular dystrophy, multiple sclerosis, amyotrophic lateral sclerosis, and lupus;
effects of gaseous tritium releases (the last one recorded in 1989);
potential contamination of private and municipal wells;
potential for airborne exposure as a result of open burning and dispersal of explosive residues and sediments from dry surface impoundments;
asbestos disposal area in the northeastern corner of the plant; and
public health impact of previous discharge of waste waters from Pantex and the old Air Force base to Pantex Lake, an off-site naturally occurring playa northeast of the plant.
For many of the health concerns, residents requested information for the eight counties closest to the Pantex Plant. After further discussion, TDH concluded that information on a four-county area would be sufficient to address residents concerns. This choice would be consistent with areas considered in previous cancer cluster investigations.
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