PUBLIC HEALTH ASSESSMENT
AMARILLO, CARSON COUNTY, TEXAS
The Agency for Toxic Substances and Disease Registry (ATSDR) selects and discusses contaminants based on severalfactors: sample design, field and laboratory data quality, and comparison of chemical concentrations to levels thatcould cause cancer or other health effects. In addition, community health concerns are considered.
Evaluating the sample design involved reviewing Department of Energy General Environmental Protection Programregulations as per DOE Order 5400.1, and the Pantex Plant's approach to locating and defining contamination. Spatial distribution of sampling locations, sampling frequency, concentration changes over time, medium-to-mediumdifferences, and correlation between the selected list of analytical parameters and suspected environmentalcontaminants are factors considered by ATSDR when determining the contaminants to which humans could beexposed.
Review of field sampling quality control procedures included interpreting data on background (or regional)concentrations of chemicals. Additionally, the adequacy and number of replicate, spiked, and blank samples arechecked to verify detection of contaminants. To assess laboratory quality control, procedures used to verifyinstrument reliability are reviewed.
Contaminant concentrations detected on- and off-site are compared to values that are believed to be without adversehealth effects upon exposure. Those values are developed by health and regulatory agencies to provide estimates oflevels at which health effects might be observed. Those values, in many cases, have been derived from animalstudies. Health effects are related not only to the exposure dose, but to the route of entry into the body and the amountof chemical absorbed by the body. For those reasons, comparison values used in public health assessments arecontaminant concentrations in specific media and for specific exposure routes. Several comparison values may beavailable for a specific contaminant. ATSDR generally selects the comparison value that is calculated using the mostconservative exposure assumptions in order to protect the most sensitive segment of the population. The potential foradverse health effects from exposure to contaminants is discussed in the Public Health Implications Section of thisdocument.
ATSDR reviewed the non-radiological (chemical) and radiological data collected in support of environmentalmonitoring at the Pantex Plant. The material reviewed covered the period of 1973 through 1998. A combined list ofenvironmental monitoring parameters for 1992 through 1997 is provided in Appendix A. The documents reviewedincluded annual and supplemental environmental reports, support documentation for the environmental impactstatement (EIS) prepared by the Los Alamos National Laboratory, and the on-going EIS.
Under Section 313 of the Emergency Planning and Community Right-to-Know Act (SARA, Title III), manufacturersare required to report to the Environmental Protection Agency (EPA) annually if they have released into theenvironment (routinely or accidentally) any of more than 300 toxic chemicals. Section 313 authorizes EPA tomaintain the data in a computerized database that is known as the Toxic Chemical Release Inventory (TRI). Manufacturing facilities (as defined in the Standard Industrial Classification codes 20-39) that have 10 or more full-time employees and that manufacture or use a Title III-listed chemical in an amount greater than its specifiedthreshold for manufacture, import, processing, or other use during any calendar year are required to estimate theirannual releases of such toxic chemicals into the air, water, and land. The database is available to federal and stategovernment officials and to the public.
A review of the current TRI file database for the Pantex Plant, consisting of data for calendar years 1987-1994, did notindicate the occurrence of environmental releases expected to cause adverse health effects.
The following terms are used in this section:
CMS (Corrective Measures Study) The analysis of potential cleanup methods and is part of the corrective actionprocess under the Resource Conservation and Recovery Act (RCRA). The RCRA CMS is equivalent to theComprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Feasibility Study.
EMEG [Environmental Media Evaluation Guide (ATSDR)] EMEGs are screening values used to select chemicalcontaminants for further evaluation in the ATSDR public health assessment. EMEG values are calculated by ATSDRusing conservative exposure assumptions that would protect the most sensitive segment of the population.
ICM (Interim Corrective Measure) A remedial action employed in the interest of protecting human health and theenvironment to address the hazards posed by actual or suspected contamination.
MCL (Maximum Contaminant Level) MCLs represent contaminant concentrations that EPA deems protective ofpublic health over a lifetime (70 years) at an exposure rate of two liters of water per day. MCLs are also regulatoryconcentrations.
mg/Kg [milligrams per kilogram (parts per million)] The unit applied to express contaminant concentrations in soil.
NFA (Finding of No Further Action) A recommendation of no further remediation action based on the finding of nocontamination, or the finding that remediation of contaminants is not warranted based on Risk Reduction Standards asestablished by the Texas Natural Resource Conservation Commission (TNRCC).
n/a not available.
Phase I Fieldwork Activity performed to determine whether contamination exists and, if so, the vertical and lateralextent of the contamination.
Phase II Fieldwork Activity performed if Phase I fieldwork identifies a need for additional information to determinethe proper characterization of the site.
Risk Reduction Standards Guidance established by the TNRCC to ensure that Resource Conservation and Recovery Act (RCRA) remedial actions are completed with utmost regard to present and future threats posed to human health and the environment. The Risk Reduction Standards also draw on guidance from the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).(6)
|Standard 1||Requires complete removal of all waste, waste residue, and contaminated media and/or decontamination to natural background concentrations for sites which have concentrations exceeding natural background concentrations. |
|Standard 2||Requires the removal and/or decontamination of waste and waste residue to the extent of eliminating any substantial present or future threats to human health and the environment for sites having concentrations which exceed the established health-based levels. |
|Requires the removal, decontamination, and/or control of waste and waste residue to the extent that any substantial present or future threats to human health and the environment are minimized or eliminated to the maximum extent practicable.|
SWMU (Solid Waste Management Unit) Any unit from which hazardous constituents may migrate irrespective of whether the units were intended for the management of solid and/or hazardous wastes.
SWMU Grouping A discrete portion of a DOE installation identified as a group of release sites treated as a singleproject for remediation. SWMUs are grouped by contaminant commonality for the purpose of identification.
µg/L [micrograms per liter of water (parts per billion)] The unit applied to express contaminant concentrations inwater.
UST (Underground Storage Tank) A stationary device, designed to contain an accumulation of liquid waste, solidwaste, or product, and constructed primarily of non-earthen materials providing structural support. Such a tank isclassified as a UST when at least 10% of the waste/product volume is below the surface.
IV.C.2 Overview of the Pantex Plant Remediation Process
The Resource Conservation and Recovery Act (RCRA) Facility Investigation (RFI) is designed to detect the presenceof hazardous substances and to determine whether they may be contaminating the surrounding environment. RFIs area condition of Pantex Plant's RCRA permit issued by the Texas Natural Resources Conservation Commission(TNRCC).
In January 1989, the EPA conducted a RCRA facility assessment to identify Solid Waste Management Units(SWMUs) that may require investigation and/or corrective action under the 1984 Hazardous and Solid WasteAmendments to the RCRA. The Draft Administrative Order of Consent, pursuant to Section 3008(h) of RCRA, wasissued in September 1989. It identified 144 SWMUs. This order outlines requirements for performing interimmeasures, RFIs, corrective measure studies, and corrective measure implementation at the Pantex Plant SWMUs. The SWMUs were organized into 15 SWMU Groupings that are to be characterized and, if found to be contaminated,carried through the corrective action process on independent schedules. SWMU Activity Data Sheet (ADS) numbersare also provided.
|1. Operable Unit AL-PX-1:||Burning Grounds Assessment (ADS 1232) |
2. Operable Unit AL-PX-2:
|High Priority Potential Release Sites (ADS 1219) |
3. Operable Unit AL-PX-3:
|Former Cooling Tower in Zone 12 (ADS 1207) |
4. Operable Unit AL-PX-4:
|Old Sewage Treatment Plant Sludge Beds (ADS 1220) |
5. Operable Unit AL-PX-5:
|Fire Training Area Burn Pits (ADS 1203) |
6. Operable Unit AL-PX-6:
|Zone 12 Groundwater Assessment (ADS 1230) |
7. Operable Unit AL-PX-7:
|Landfills (ADS 1200) |
8. Operable Unit AL-PX-8:
|Ditches and Playas (ADS 1216) |
9. Operable Unit AL-PX-9:
|Firing Sites (ADS 1205) |
10. Operable Unit AL-PX-10:
|Leaking USTs (ADS 1223) |
11. Operable Unit AL-PX-11:
|Miscellaneous High-Explosives Radiation Sites (ADS 1212) |
|12. Operable Unit AL-PX-12:|| |
Miscellaneous Chemical Spills/Releases (ADS 1198)
13. Operable Unit AL-PX-13:
|Supplemental Verification Sites (ADS 1222) |
14. Operable Unit AL-PX-14:
|USTs at Other Locations (ADS 1227) |
15. Operable Unit AL-PX-15:
|11-14 Hypalon Pond (ADS 1213)|
A general description and comment on the current activity status of each of the Pantex Plant SWMUs is presented in Appendix D.
The Pantex Plant Groundwater Monitoring Program includes 77 wells (64 monitoring wells, 5 drinking waterproduction wells, 7 water treatment study wells, and 1 off-site control location). Twelve monitoring wells, the singleoff-site control location, and all five production wells are completed in the Ogallala aquifer. The remaining 59 wellsare completed in the perched aquifer.
Samples from the production wells are used as a secondary check for possible chemical migration from the perchedaquifer into the Ogallala aquifer. If contamination of the Ogallala aquifer were to occur as a result of Pantex Plantoperations, it would be discovered first in the production wells. In this manner, the Pantex Plant production wellsserve as interceptor wells for the downgradient City of Amarillo drinking water production wells. The Pantex Plantand City of Amarillo production wells are also monitored in accordance with Safe Drinking Water Act requirementsfor source water.
The water supply at a control location in Bushland, Texas, is sampled monthly to obtain control data for comparisonwith data from the plant. This control well is completed in the Ogallala aquifer upgradient from Pantex Plant and isnot affected by plant operations.
Constituents analyzed under the environmental monitoring programs for all media are listed in Appendix A. Theanalyses include four screening tests for indicators of contamination: pH, conductivity, total organic carbon, and totalorganic halogen. Analyses also include the water quality parameters specified under Resource Conservation andRecovery Act (RCRA) monitoring requirements: iron, manganese, sodium, chlorides, phenols, and sulfates.
Analytical results are evaluated quarterly and compared to guidelines for RCRA-regulated facilities, drinking waterstandards, and DOE criteria. Mean values between monitored wells and the off-site or control location are comparedstatistically to determine potential impacts of Plant operations on groundwater. Data are compared to the SafeDrinking Water Act Maximum Contaminant Levels (MCLs), Maximum Contaminant Level Goals (MCLGs), the riskreduction levels developed for Pantex Plant, or derived concentration guides for radionuclides. The risk reductionlevels are generally at least as stringent as the Safe Drinking Water Act MCLs and also set standards for contaminantsnot regulated by the Safe Drinking Water Act.
Fifty-one on-site wells completed in the perched aquifer are sampled quarterly, semi-annually, or annually. Samplesare analyzed for radiological and chemical constituents. No pesticides, herbicides, polychlorinated biphenyls (PCBs),or dioxins have been detected in perched groundwater. Chemical contamination initially detected in the on-siteperched aquifer in the early 1990s and still present is made up of metals, explosive compounds, and volatile organiccompounds. Because that particular perched aquifer is not utilized as a drinking water source downgradient of thecontaminant plumes, no one is exposed to those contaminants. Pantex Plant is currently conducting perched aquiferremediation activities using pump, treat, and recharge technology to reduce contaminant concentrations to acceptablelevels. A May 1998 update on the treatability study is provided in Appendix C.
In late 1995, a perched aquifer monitoring well in the southeastern corner of the Pantex Plant revealed high levels (inexcess of 5,000 ug/L) of the explosive RDX (also known as Royal Demolition Explosive, Cyclonite, or Hexogen). Two new monitoring wells were installed in the perched aquifer on the off-site property (1,200 feet east of the PantexPlant boundary) in May 1996. Sampling of those off-site wells in June 1996 and January 1997 detected explosiveconstituents at levels above ATSDR comparison values; however, it is critical to note that these are perched aquifermonitoring wells and this particular perched aquifer is not used as a drinking water source.
Two Ogallala wells were present at a property owner's home 1,200 feet east southeast of the two off-site monitoringwells. The first well (windmill well) was drilled to the Ogallala in 1896 as a drinking water well. In 1964, due todropping Ogallala water levels, a new, deeper well (domestic well) was installed in the Ogallala. The new well waslocated 10 feet north of the old windmill well. The common problem with the two drinking water wells was in themanner of installation. The well casing ran from the surface to the Ogallala, where it was gravel packed forproduction. There was no barrier to inhibit flow from the perched zone (if it is or has been present and saturated) intothe Ogallala through the annular space (the space between the casing and the bore hole). Apparently this was the casebecause, in May 1995 and again in May 1996, the Texas Natural Resource Conservation Commission (TNRCC)sampled the two drinking water wells and detected low concentrations of explosives at levels below health screeningvalues.
To prevent further intrusion into the Ogallala, the two off-site drinking water wells were sealed and a new drinkingwater well was installed in the Ogallala in May 1996. Precautions were taken in the construction of the new well toprevent intrusion of contaminated perched aquifer water into the Ogallala. Particulate and carbon filters were alsoinstalled between the well and the property owner's home. Quarterly sampling of the new well has not detectedcontaminants at levels known to cause adverse health effects; however, contaminants such as metals are detectedregularly and are typical of natural background levels.
Three monitoring wells in the Ogallala aquifer are sampled monthly and six quarterly for radiological and chemicalconstituents. Quarterly sampling in two additional wells was initiated in 1995. No chemical contaminants exceedinghealth screening values have been detected to date. Possible bacteriological contamination was detected in one of theproduction wells in July 1995; however, two subsequent samples did not detect and therefore did not confirm thepresence of biological contamination.
TNRCC collected samples from the Pantex Plant drinking water supply system in October 1996 to determine whetherregulatory requirements were met. Plant personnel collected additional samples at the same time. TNRCC alsoanalyzed for lead and copper in samples collected in July 1996 by Pantex Plant personnel. Results for all analyseswere similar and within regulatory limits.
In summary, although chemical contamination above screening values has been detected in the perched aquifer at thesoutheastern plant boundary, that particular perched aquifer is not used as a water source downgradient of thecontaminant plumes. If that perched aquifer was used in the future as a water source downgradient of the contaminantplumes, water from the perched aquifer would require treatment to remove contamination before it would be safe forconsumption. Chemical contamination above screening values has not been detected in the Ogallala aquifer, which isused as a drinking water source throughout the region.
There are no rivers or streams at the Pantex Plant; the only surface waters occur in ditches and playas. Department ofEnergy (DOE) owned and DOE-leased property is associated with six playas, two of which are on the Texas TechUniversity DOE-leased property. Most stormwater runoff from the DOE-owned and DOE-leased lands flows to theon-site playas: 11 effluents from Plant operations are treated and, along with some noncontact industrial discharges,are directed into ditches that drain to three playas (Playas #1, #2, and #4), treated industrial discharges from Zone 12and the eastern portion of Zone 11 flow through ditches to Playa #1, stormwater runoff from western portions of Zone11 is channeled to Playa #2, stormwater runoff from the Burning Ground drains into Playa #3 as sheet flow, andrunoff from southern portions of Zones 11 and 12 flows into Playa #4. Plant activities no longer influence flows toPantex Lake (owned by DOE), located to the northeast because plant discharges to Pantex Lake were discontinuedseveral years ago; however, monitoring is still conducted because of the past wastewater discharge practices. The areasurrounding Pantex Lake is used for agriculture, and currently stormwater is the only contributor to water in the playa. Playa #5, which is on Texas Tech University property, is not influenced by operations at Pantex Plant and receivesrunoff from surrounding Texas Tech farming operations.
Surface water monitoring at the Pantex Plant is generally dependent on rainfall or discharge events; samples arecollected when flows occur. Because flows are continuous at the Wastewater Treatment Facility, sampling there canbe conducted on a regular schedule. Sampling at the Wastewater Treatment Facility was conducted in accordancewith the Wastewater No-Discharge Permit issued in 1988 by the Texas Water Commission (the predecessor agency tothe Texas Natural Resource Conservation Commission) until that permit was replaced with a Wastewater DischargePermit issued by TNRCC June 14, 1996. A similar permit was issued to Pantex by EPA on June 1, 1996. For controlpurposes, off-site surface water is sampled from a playa at Bushland, Texas. The control data are compared with on-site data to identify significant differences in contaminant levels potentially resulting from plant operations. As shown in Appendix A, samples from selected monitoring locations are analyzed for metals, explosives,polychlorinated biphenyls (PCBs), pesticides, herbicides, volatile organic compounds, semivolatile organiccompounds, and water quality indicators reflecting water quality and treatment.
The tail-water pit located in the northeast corner of Pantex Plant near the Old Sewage Treatment Plant (OSTP)receives runoff from the surrounding agricultural lands, the OSTP (inactive), and portions of the Firing Sites. Thetail-water pit is a stormwater outfall, thus it receives no direct effluent discharge from the plant. Generally the tail-water pit contains all drainage from the northeast section of the plant and returns the water to Playa 1 by forcedpumping; however, during high rainfall events, the pit can overflow into the drainage ditches along FM 293 whichthen channels the water to Pratt Lake, a playa located north of the Pantex Plant boundary. This is the only surfacewater runoff boundary area at Pantex Plant which may be influenced by stormwater runoff from operational areas.
The tail-water pit is currently sampled quarterly in addition to "special request" sampling events when the wateroverflows. The "special request" sampling is performed as a good-neighbor policy when plant personnel are presentduring an overflow event. Due to pumps located in the tail-water pit which return the water to Playa 1, overflow ofthis area occurs infrequently. The last 3 known overflow events occurred on February 14, 1997, April 25, 1997, andMarch 19, 1998.
The sampling program for the tail-water area has changed over time. Starting October 1997, the pit was (and is)sampled quarterly for visual contamination. Visual inspection parameters include color, odor, clarity, sheen,suspended solids, floating solids, settled solids and other obvious indicators of stormwater pollutants. Prior toOctober 1997, the tail-water pit was sampled semiannually and analyzed for water quality indicators, metals, volatileorganic compounds, semi-volatile organic compounds, pesticides/herbicides, PCBs, chemical oxygen demand, pH,high explosives, radionuclides, and flow. The only parameter concentration detected above a background referenceplaya water sample was an occasional low-level detection of pesticide which would be reasonably expected from thesurrounding agricultural areas. Due to a change in the NPDES permit to a new "Multi-Sector Storm Water Permit,"sampling after October 1998 will be conducted quarterly and will include both visual and analytical sampling. Theanalytical parameters include total organic carbon, iron, gross alpha,and gross beta. For "special request" sampling, analytes include pesticides/herbicides, PCBs, volatile organiccompounds, semi-volatile organic compounds, high explosives, metals, radionuclides, and water quality indicators.
Since the issuance of the Pantex permits, some metals have been detected at Outfall 006 at concentrations above permitguidelines. Those elevated concentrations resulted from the natural levels of metals in soil in the open ditches leading tothe outfall weir. In a November 26, 1996, letter from J.S. Johnson (Pantex) to Ted Palit (EPA), "Written Notification ofNon-Compliance with U.S. Environmental Protection Agency (EPA) Industrial Discharge National Pollutant DischargeElimination System (NPDES) Permit No. TX0107107", the process for the identification, development, andimplementation of corrective measures for elevated metal concentrations at this outfall was defined. Correctivemeasures identified and implemented included placement of gravel in localized areas affected by erosion upstream ofOutfall 006, removal of all sediment from the drainage structure immediately upstream from the outfall with theexception of a thin layer that remains on the bottom of the channel and within sections of the security perimeter fences,and grading and placement of gravel in the buffer area immediately adjacent to the outfall structure.
Chlorine residual, ammonia, and total suspended solids have exceeded permit guidelines at the waste water treatmentfacility (WWTF); those elevated concentrations have been associated with algae growth in the lagoon. Theconcentrations of nitrogen, organic carbon, and phosphorus in the wastewater are high enough to promote significantalgae growth, which is typical at a facultative lagoon. These nutrients, coupled with the seasonal increase intemperature and sunlight, enhance the growth of algae in the WWTF during the warmer seasons. Subsequently, algaegrowth is reduced by colder temperatures and decreased sunlight typical in the winter months.
No enforcement action has been issued by the TNRCC or EPA to date, but a compliance order to enforce existingpermit limits was issued to the Pantex Plant by EPA. The EPA Administrative Order, which became effectiveDecember 1, 1997 requires negotiation of an action plan and schedule for correcting the violations. The violationsmentioned in the Administrative Order included ammonia; oil, greasy, and total suspended solids; total metals(manganese, titanium, zinc, copper, and chromium from soil transported in storm water runoff); and silver from aphoto processing operation.
The EPA and the Texas Natural Resource Conservation Commission inspected Pantex in April 1997 and identified nosignificant issues, with the exception of the permit violations. As a result of that inspection, Pantex has undertakencorrective actions to achieve compliance with the permit limits. Some of these actions include the algae-eating fishresearch project, initiated in October 1997, focused on controlling total suspended solid levels in discharge from thewaste water treatment facility (WWTF); erosion and sediment control; and process modifications including theinstallation of a flow-weighted chlorine-dosing system. To further meet permit requirements, design of an upgrade tothe existing WWTF was initiated in 1998. The goal of the project is to eliminate industrial discharges to open ditchesand improve treatment capabilities.
The EPA and TNRCC have found no instances to date where contaminant concentrations have exceeded guidelinesthat pose a threat to human health. ATSDR did not identify exposure pathways related to the violations.
Routine surface soil surveillance at Pantex Plant is conducted both on-site and off-site with samples analyzed formetals, explosives, and volatile compounds (Appendix A). The routine soil surveillance program provides a directmeasure of environmental contamination because soil accumulates contaminants deposited from the air and surfacewater over time; therefore, soil surveillance allows evaluation of long-term trends.
Soil is routinely sampled at 30 on-site and 17 off-site locations. In addition, samples are collected at 60 locationswithin Zone 4 West. All soil samples are collected according to sampling procedures outlined in Pantex Plant InternalOperating Procedure D4235, "Soil Sampling Procedures." Samples for radiological analyses are collected as 3.5 inchdiameter by 2-inch deep cores. Samples for metals, explosives, and volatile organics are collected as 2-inch diameterby 4-inch deep cores.
Soil samples are collected from two general landscape positions: playa bottoms and interplaya uplands. This routinesampling of the playa bottoms began March 17, 1994. The characteristic soil types for these landscape positions areRandall clay in playa bottoms and Pullman clay loam in the interplaya uplands. Two off-site sampling locations (anupland location and a playa bottom) are located at Bushland, Texas. Samples collected at these two locations areconsidered controls, indicating background levels of contamination. The control locations were chosen because theyare 35 miles from the Plant in a direction that is generally upwind and thus should not be affected by Plant operations. On-site soil samples are collected monthly from five areas: the Burning Ground, firing sites, Playa #1, Playa #2, andPlaya #3. Samples are collected in Zone 4 West once during the year. Off-site samples are collected quarterly fromareas within a 5-mile radius of the Plant. Samples from the control locations are collected monthly.
Because open burning has the potential to release metals, explosives, or volatile organic compounds that may bedeposited or incorporated in surface water runoff, soil samples from the Burning Ground, Playa #3, and Bushland(control) are also analyzed for those contaminants. All samples are analyzed by an off-site contract laboratory thatmeets U.S. Environmental Protection Agency (EPA) requirements.
Overall, soil monitoring results have been within the observed ranges of concentrations for uncontaminated soil andcomparable to historical results and those for the control locations. Although, boron, manganese, zinc, HMX, andtotal xylene concentrations in the area of the Burning Grounds exceeded screening values, the location is on-site in acontrolled-access area thereby preventing exposure to unprotected individuals. The site is also being addressed underthe site remediation program. Those compounds have not been detected off-site at levels that would cause adversehealth effects.
Pantex established a system of radiological air monitoring stations consisting of 9 continuous air monitoring stationsat a 5 mile radius in November 1973. In 1995, concrete pads and electrical utilities at three of the fenceline airmonitoring stations were augmented so that the stations could be used for both nonradiological and radiologicalmonitoring. The three stations were upwind and downwind (based on the prevailing wind direction), respectively, ofthe Burning Grounds and were equipped to sample for hydrogen fluoride and volatile organic compounds. Onedownwind station was also equipped to sample for particulate matter less than 10 microns in size. The three sitesprovided an opportunity to compare Pantex Plant-collected data with data collected by the Texas Natural ResourceConservation Commission (TNRCC) on site.
Prior to 1998 TNRCC conducted routine air monitoring for air pollutants, such as volatile organic compounds,particulate matter less than 10 microns in diameter (PM-10), and hydrogen fluoride. Monitoring at those stations wasconducted for 24 hours every sixth day on a scheduled rotation. In addition, a Fourier Transform Infrared monitorwas installed in 1995 at the Masterson Pump Station, approximately 2 miles north by northeast of the plant. Thisstation operated continuously, collecting data on volatile organic compounds and meteorological conditions.
TNRCC also conducted routine nonradiological ambient air monitoring at Pantex Plant, and results of the samplingprogram have been published in a series of quarterly reports. Except for a few days on site when particulate matterwas detected at levels exceeding the National Ambient Air Quality Standard, and on one occasion when methylenechloride was detected at levels seven times the 24-hour Effects Screening Level, also on site, levels of pollutantsdetected have been below health screening values. TNRCC Effects Screening Levels (ESLs) are guidelinecomparison levels set below levels at which adverse health effects are reported in the scientific literature. If an airconcentration of a chemical is below an ESL, adverse health effects are not expected to occur. However, if an airconcentration is above the ESL, it is not indicative that adverse effects will occur, but rather that further evaluation iswarranted. Particulate matter is occasionally present in air around Pantex Plant as a result of high winds andagricultural activity, and the maximum 24-hour methylene chloride concentration, although in excess of the screeningvalue, was less than levels that would result in adverse health effects. The Air Quality Control Region includingPantex Plant and the surrounding Amarillo Area is classified by the Environmental Protection Agency (EPA) as"Attainment" for all National Ambient Air Quality Standards (40 CFR 52.2279). This classification means that thearea meets all existing air quality standards for which it could be evaluated.
In 1997, budget constraints combined with monitoring data indicating no significant levels of air contamination frompast air sampling, resulted in a decision to reduce the level of monitoring frequency beginning in 1998. It wasdetermined that monitoring would be on an episodic, event-triggered basis, with a maximum of thirty sampling eventsper year at two sites (Sites No. 4 and 5) containing noncontinuous monitors. Continuous monitoring would continueas in the past at one site containing a continuous Fourier transform infrared (FTIR) monitor (Site No. 7). The TNRCCRegional Manager, located in the Amarillo Office, will determine the particular sampling day, based on criteria suchas burning days, grass fires, or other work activities with potential impact on air quality. To assist in that effort, thePantex Plant is required to provide a weekly schedule to TNRCC of any scheduled activity that could result in apotential impact on air quality as well as immediate notification of grass fires, upset or emergency maintenancesituations, or any unscheduled activities potentially impacting air quality.
Parameters to be measured under the 1998 program include TSP, PM-10 and VOCs, using both gaschromatograph/mass spectrometer detector (GC/MSD) and FTIR detection. Meteorological parameters of wind speed,wind direction, temperature, and relative humidity will also be measured.
Monitoring sites are located around the burning ground of the Pantex facility to establish the effect of normaloperating activities on the ambient air. Meteorological information obtained from the National Weather Service wasused to establish the most prevalent wind direction, which is from the south/southwest. Based on this information,sampling sites were established around the burning grounds, and Zones 11 and 12, where most of the solvents arehandled. An additional monitoring site, Site No. 7, is located to the northeast of the Pantex facility. Under the 1998program, three of the five original sites remain operational, Sites No. 4, 5, and 7. At this time, there are no plans todismantle the inactive sites.
Because all the air monitoring sites require 240 volts alternating current power, they are located near power lines andtransformer locations. The TNRCC Ambient Air Monitoring staff coordinated with the DOE contractor to acquireneeded utility connections and security provisions. Because of the sensitive nature of nuclear weapons facilities,security considerations of the DOE were also a determining factor in monitor locations.
Siting criteria (established by the U.S. Environmental Protection Agency in 40 Code of Federal Regulations Part 58,Appendices D and E) for ambient monitoring sites were followed. Therefore, monitoring sites are located where theyare not hampered by tall structures or trees. Consideration was also given not to place TSP and PM-10 monitors closeto unpaved roads or alleyways. Accessibility to the monitoring sites is another important consideration because eachsite is visited frequently to change filters or sampling canisters. Therefore, monitors were sited in areas where securityclearance is not a problem. The following is a detailed description of the 1998 air monitoring program active sites.
Site No. 4: The sampling trailer is located about 210 feet due north and 70 feet west of Firing Site 16. Theequipment in the trailer includes a weather system that measures wind direction, wind speed, temperature,and relative humidity; the VOC sampler; and a data acquisition system. TSP and PM-10 samplers areplaced upon raised platforms near the trailer on a reinforced concrete pad.
Site No. 5: The sampling trailer is located just inside the perimeter fence on Farm-to-Market Road 293,approximately 3,400 feet northeast of the burning grounds, at the fourth power pole approximately 600feet west of a farmhouse. The farmhouse is the closest residence near the Pantex facility. Samplingequipment at this site is an exact replica of that at Site No. 4, except that a colocated PM-10 sampler forquality assurance sampling is located at Site No. 5, rather than a colocated TSP sampler, and two colocatedVOC samplers are located in the trailer.
Site No. 7: The sampling trailer is located at the Masterson pump station, northeast of the BurningGrounds. The trailer contains an FTIR detector with dual 100-meter White cells. A meteorological stationis integrated with the FTIR to incorporate wind direction, atmospheric pressure, and temperaturemeasurements into the sample data files. Because of the higher detection levels associated withmeasurements made using this method, these measurements are classified as non-critical, taken for informational purposes only.
Sampling for TSP, PM-10, and VOC's is on an episodic basis. Each sample is collected for a period of 24 hours. The FTIR samples are taken every six minutes, alternating between a scrubbed (of water and carbon dioxideinterferents) and unscrubbed cell. Meteorological data are collected continuously with a datalogger recordingfive-minute converted averages that are eventually converted into hourly averages. All noncontinuous pollutantsamples are transported to the TNRCC's Austin laboratory and analyzed.
Surveillance of plant and animal life is important to understanding and assessing the effects of Pantex Plant operationson the environment. Vegetation samples taken for radionuclide and fluoride analyses represent both native speciesand crops (see IV.C.4.g for discussion of radionuclide sampling results). Native vegetation on the Southern HighPlains is primarily range grasses and forbs (weeds). Crops are defined as any agricultural product that can beharvested or gathered for food, forage, or fiber. Forage, often referred to as fodder, is plant matter composed of leavesand stems that is used as food by domestic animals. Because various species and individuals take up contaminantsdifferently under different growing conditions, data interpretation is complex, and results must be considered andevaluated in concert with results of surveillance of other media, such as soils and air.
Systematic faunal sampling for radiological contamination was initiated in July 1995. Animals at Pantex Plant aresampled to determine whether the Plant's activities are having an impact on populations. Prairie dogs are the mainspecies sampled at the Plant because they interact with other environmental media being analyzed; they eat vegetation,dig in the soil, and breathe soil particulates daily. Prairie dogs are numerous enough that sampling will not seriouslyimpact their population, and samples can be collected from the same general location repeatedly. Because no priorsystematic data are available for comparison, the 1995 data serve as a baseline for future monitoring.
The only non-radiological parameter currently under surveillance is inorganic fluoride concentrations in vegetation. Pantex Plant's current operations include thermal treatment of explosives and explosive contaminated materials at theBurning Grounds, which may release fluoride particulates to the atmosphere that can be taken up through microscopicopenings in the leaves of vegetation. Some animals, particularly cattle, are more sensitive than people to fluoride andmay develop fluorosis from grazing on contaminated vegetation. The Texas Air Control Board, a predecessor agencyof the Texas Natural Resource Conservation Commission (TNRCC), established limits for inorganic fluoride in airand forage in Texas Administrative Code, Title 30, Chapter 113, "Control of Air Pollution from Toxic Materials." For1995, this limit varies from 20 to 60 parts per million (ppm) by weight, depending on the number of consecutivemonthly samples analyzed from any location.
Winter wheat, grain sorghum, forage sorghum, and native vegetation are grazed by cattle at Pantex Plant; thereforesamples of these plants were analyzed for inorganic fluoride. Samples from crops and native plants were collected inaccordance with plant procedures for inorganic fluoride in vegetation. The fluoride sampling was begun in March1995. Samples were collected and analyzed from at least five on-site and two off-site control locations each monthexcept May. One of the five on-site samples was always scheduled to be taken from Playa #3, which was not sampledif vegetation was submerged, as it was in May. All sampled locations with detectable fluoride were below theregulatory limits.
The following terms are used in this section:
AEC (Atomic Energy Commission) The AEC was established after the end of World War II to direct theuses of nuclear energy. The AEC was dissolved in the early 1970s into the Nuclear RegulatoryCommission (NRC) and Energy Research and Development Administration (ERDA). The NRC wasresponsible for regulating nuclear energy, power, and uses of radioactive materials. ERDA wasresponsible for nuclear weapons production. Later ERDA's name was changed to the Department ofEnergy.
Alpha Particle A charged particle emitted from the nucleus of an atom having a mass and electricalcharge (+2) equal to that of a helium nucleus: i.e., two protons and two neutrons.
Beta Particle A charged particle emitted from the nucleus of an atom. Each beta particle has a -1electrical charge and a mass equal to an electron. Once emitted, there is no difference between the betaparticle and the electron.
DCG (Derived Concentration Guide) The concentration of a radionuclide in air or water that, underconditions of continuous exposure for one year by one exposure mode (either ingestion of water,submersion in air, or inhalation), would result in an effective dose equivalent of 100 mrem. DCGs do notconsider decay products when the parent radionuclide is the cause of the exposure.
Dose Equivalent The radiation dose arising from an exposure to the whole body or parts of the bodymodified using radiation protection factors that take into account the type of radiation (alpha or betaparticles; radiation weighting factors) and the dose to tissues (tissue weighting factors). The radiationweighting factors describe the relative damage caused by the types of the radiation. The tissue weightingfactors describe the sensitivity of different tissues to radiation.
Gross Alpha and Gross Beta Radiation Measurements Estimations of the total amount of alpha or betaemitting radionuclides in the environmental media. The measurement can only serve as an approximationor starting point for further analyses. Because these types of measurements do not identify theradionuclide(s), it is weighted relative to the radionuclide selected for instrument calibration; no estimateof radiation dose can be made from these values.
Maximum Contaminant Level (MCL) The MCL is the regulatory limit for contaminants in drinkingwater supplies. For radioactive materials, the MCL, which varies with the radionuclide, is based on theradiation dose delivered to an individual who consumes 2 liters of water per day every day of the year.
NRC (Nuclear Regulatory Commission) An independent agency established by the U.S. Congress underthe Energy Reorganization Act of 1974. The NRC mission is to ensure adequate protection of the publichealth and safety, the common defense and security, and the environment in the use of nuclear materials inthe United States. The NRC's scope of responsibility includes regulation of commercial nuclear powerreactors; nonpower research, test, and training reactors, fuel cycle facilities; medical, academic, andindustrial uses of nuclear materials the transport, storage, and disposal of nuclear materials and waste. NRC regulations do not specifically apply to DOE facilities such as Pantex but comparison of NRCcompliance values and DOE values can be used as a reference point.
Radioactivity Units Radioactivity units are used to quantify radioactive material. The units are based onthe rate at which radioactive materials decay; that is, the number of transformations (atomicdisintegrations) per second (dps). The units are expressed in two systems, a conventional system and theSysteme International (SI). A curie (Ci) of radioactive material is defined as 37 billion dps; one becquerel(Bq) is defined as one dps. One Bq equals 27 x 10-12 Ci. Because of the small amounts of contaminantsfound in the environment at Pantex, prefixes are used. Table 1 lists the conventional and SI units.
|Conventional system||SI (International System)|
|1 picocurie (1 x 10-12)||0.037 Bq|
|1 microcurie (1 x 10-6)||37,000 Bq|
|1 millicurie (1 x 10-3)||37,000,000 Bq|
- Radiation Dose The radiation dose is a generic term for any of the following terms. Specifically, theabsorbed dose describes the amount of energy deposited by radiation into a system of a given mass. Theunits are the rad or the gray (Gy). The effective dose adjusts the absorbed dose for the type of radiation(alpha, beta, gamma). The equivalent dose weights the effective dose with a factor for the type of tissueirradiated. The units are the rem or the sievert (Sv). As with the radioactivity units, conventional unitsand SI units are used. The conventional system uses the rad and rem and the SI system uses the gray andthe sievert. The same prefixes discussed in the radioactivity units are used for the radiation dose. Thereare 100 rads or rem in one Gy or Sv, respectively. The average background radiation exposure in theUnited States is 3 mSv (300 millirem) which includes radon.
Radioactivity per Mass Unit The radioactivity of a material divided by a mass. This is usually expressedas activity per gram (1/30th of an ounce) or per kilogram (2.2 pounds per kilogram). An example of suchusage is pCi per gram (g).
Radioactivity per Volume Unit Expressed as amounts of radioactivity per cubic meter or milliliter ofwater or air. A cubic meter contains over 264 gallons; whereas, a milliliter (mL) equals about 1/30th ofone ounce. A liter is 0.946 quarts or 30 ounces.
RCG (Radiation Concentration Guides) Established by the AEC and were used to set limits of exposureto workers or members of the public. The RCG represents the dose limit delivered by a specific amount ofradioactivity in a specific environmental media. For the public, the RCG was 170 millirem.
SI (Systeme International or International System) is a relatively new single system designed to provide aunified system of technical terminology within the scientific community. In this report, the SI units willbe given with the conventional units in parenthesis.
Thermoluminescent Dosimeters (TLD) TLDs are used to monitor long-term levels of gamma or photonradiation in environmental settings. TLDs are also used for personal dosimeters. The most common typesof TLDs are made of lithium fluoride.
Uranium, Depleted A product of the uranium enrichment process, depleted uranium (DU), is composedof mostly U-238 (minimum 99.3% U-238). The amounts of U-234 and U-235 present in natural uraniumhave been artificially separated. The DU is used in industry and the military for uses such as ballast inaircraft and elevator counterbalances, radiation shielding, armor, and armor piercing shells. The DU canbe used in nuclear weapons.
Uranium, Naturally Occurring Natural uranium is composed of 3 chemically identical forms or isotopesthat occur at different abundances. They have the same number of protons and electrons but the number ofneutrons differ. The atomic mass is the sum of the protons and neutrons. In nature, the isotopes ofuranium with their abundances are U-238 (99.275%), U-235 (0.72%) and U-234 (0.0055%). Of the threeisotopes, only U-235 can be used as nuclear weapons material and it must be separated through a series ofcomplex technical steps. In Texas, the apparent background concentration of total uranium in Pullmansoils which compose much of the Panhandle area ranges from 0.034 to 0.046 Bq/g (0.91 - 1.25 pCi/g). The background levels of uranium collected near the Bushland location were reported at about 0.031 Bq/g (0.84 pCi/g).
The Pantex Plant Annual Environmental Monitoring Reports were reviewed for the years covering 1973 through 1996as were the quality assurance and quality control program reports for radiological sampling and laboratory analysis. Many of these reports were prepared prior to the remedial investigations at the site. Those reports contain descriptionsof the radiological monitoring and sampling programs in support of environmental restoration and protection aroundthe Pantex plant. Pantex monitors surface waters, groundwater, soils, air, and biota in and around the facility. Another data source used was the USGS National Geochemical Data base: National Uranium Resource EvaluationData for the Conterminous United States, USGS Digital Data Series DDS-18-A (1994). The following is a summaryof these environmental reports.
In general, Pantex initiated environmental monitoring in 1972 when they began air, water and vegetation monitoring. At that time, the monitoring reports contained a limited amount of data. Since then, the number of samples hasincreased on a yearly basis and the range of the sample area has increased. For example, in 1974, Pantex addedtritiated water (HTO) monitoring to the air monitoring system and 7 rabbit specimens were collected. Today non-radiologicals and more plant and animal species are included in their reports. In the early reports, the data wereexpressed in units commonly used at that time. To compare those data with current terminology required conversionto the more commonly used terms of today.
The Los Alamos National Laboratory estimated the annual releases of depleted uranium (DU) from 1963 to 1979. These estimates are U-238 (595 million Bq; 16.1 mCi), U-234 (222 million Bq; 6 mCi), and U-235 (11.1 million BQ;0.3 mCi). Aerial surveys located the majority of the DU (96%) around Firing Site 5 with the remainder around FiringSite 4.(8)
The waters sampled in the 1990s included groundwater from the Ogallala aquifer, production wells, and monitoringwells. Radioactivity in groundwater samples or wells are below the current or proposed Maximum ContaminantLevels (MCL); that is, the radiological dose is expected to be less than 0.04 mSv (4 mrem) per year. Appendix Acontains the list of the radionuclides monitored or analyzed for in the groundwater.
Waters contained on-site in some playas were higher in radioactivity than off-site background levels; however, thesewere still below MCL values. Few surface water samples were collected off-site in the early years of environmentalsampling. In 1975 and 1976, elevated levels of gross alpha radioactivity (concentration) were found at stations WS 1(near Pantex Lake), 2, and 6. However, no conclusions can be drawn from these samples. In the 1980s, watersamples collected were all below the levels mandated in the Safe Drinking Water Act.
The radioactivity concentrations in soil samples during 1973 were less than the established RCG for members of thepublic. Based on a percent of the RCG, the highest value was less than 10% of the RCG and that was plutonium (Pu),presumably from world-wide atmospheric testing. The AEC (now DOE) did share the environmental samples withthe EPA but at that time, the comparisons of the AEC results with EPA results were not very good. The averageuranium in soils was about 0.0056 Bq/g (0.15 pCi/g) and plutonium was about 0.015 Bq/g (0.4 pCi/g). The EPAvalues were higher for plutonium but lower for uranium - but still below levels that would cause adverse healtheffects.
In 1975, elevated levels of uranium were found in the soils north of Zone 4; but, the values were still less than 0.11Bq/g (3 pCi/g), about 3 times above background levels. Radioactivity concentrations in soils of the 1990s show trendssimilar to that in waters. The radioactivity levels in off-site soils are similar or equal to background levels both in thevicinity of Pantex and at other locations in the United States. However, uranium levels in soils of several Pantexfiring sites (Sites 4 and 10) strongly suggest the presence of depleted uranium. Elevated levels of uranium in soilswere reported at several firing site sampling locations, FA-SS-01, FB-SS-05 through 08, FC-SS-04 and 05. The levels,however, are within acceptable health and exposure levels of both the DOE and the Nuclear Regulatory Commissionfor areas of controlled access.
In 1985, no plutonium was detected in either on-site or off-site soils. Uranium in soils near the site (off-site) werecomparable to background locations. High levels of uranium (several times above background) were still detected insoils at several firing site sampling locations.
In the 1986 environmental report, off-site sample location OS-SS-06 showed elevated uranium in soil 0.48 Bq/g (13pCi/g). This sample was collected north of Zone 4 and appears to have been collected at the fence line (propertyboundary). Soil samples around Firing Sites 4 and 5 continued to show high uranium in soils.
Pantex did not report releases of uranium in 1987; however, samples OS-SS-04 and samples OS-SS-01 (NW), 02(NWN), 10 (N Zone 4), 18 (NE Pantex Lake), 30 (NW of lake), and 31 (SW of lake) showed high uranium in soil. Firing site samples FA-SS-01 and FB-SS-01 continued to show very high uranium in soils.
More recent reports cover the Pantex area in more detail with respect to uranium and plutonium concentrations in soilsboth on-site and off-DOE property. In all cases of off-site samples, there were no levels of uranium or plutoniumfound that would be considered a health hazard.
Soil samples from Landfill 6 located within Solid Waste Management Unit 57 show elevated levels of uranium in soilaveraging 0.38 Bq/g (10.25 pCi/g) in both landfill debris and in subsurface soils outside the landfill proper. Themethod used for this evaluation was a gamma scan (nonspecific) and when samples were re-analyzed using alphaspectroscopy (specific analysis), U-238 was found at background levels.(9) In general most samples for this particularsite were qualified estimates as contamination was also present in the blanks prepared for quality control. The actualconcentrations could be higher or lower than reported because uranium was present in the quality control samples.
Soil concentrations of uranium in Firing Sites 5, 6, and 15 (ADS 1205) show that thorium-232 (Th-232) and one of itsdecay products, Th-228, appear to be in equilibrium from 0 to 2 feet in depth. However, the relative concentrations oftwo uranium isotopes, U-238/234, indicate the presence of depleted uranium as expected from firing site activities. Depleted uranium was found in excess of 1.1 Bq/g (30 pCi/g) at 6 locations from the surface to 2 feet in depth. Therange found was 1.3 - 19.4 Bq/g (35.8 - 523.5 pCi/g). Very little U-235 was found in these samples, 0.033 Bq/g (0.89pCi/g) and 0.28 Bq/g (7.5 pCi/g). The highest reported value was 1-2 feet down and located near the foot of a berm. At the same location, DU was found at concentrations ranging from 1.3 - 5.8 Bq/g (34 - 156 pCi/g) at 3, 4 and 5 feet(9).
Within the area of the Nuclear Weapons Accident Residue site, some indication of DU existed. The Nuclear WeaponsAccident Residue site contained debris from weapons accidents. All debris had been removed by the late 1980's toother DOE complexes. The expected ratio of U-238/U-234 should have been 1.0 but at this site the ratio was 6.5.However, the total activities still were less than 1.1 Bq/g (30 pCi/g) (10) which is not considered a health hazard.
Ambient radiation is photon radiation present in the environment. This type of radiation, measured bythermoluminescent dosimeters (TLD), is statistically indistinguishable from on-site background levels. Ambientlevels of radiation as detected by TLD readings beginning in 1985 were similar both on and off-site, that is they werecomparable to background levels.
The current TLD readings show an average annual exposure of approximately 1 mGy (100 millirad) per year both on-site and off-site. This value is also consistent with ambient exposures across the country at similar altitudes.
Pantex established a system of air monitoring stations consisting of 9 continuous air monitoring stations at a 5 mileradius in November 1973. Early Pantex reports estimated atmospheric releases of depleted uranium (DU) and tritium(H-3) but stated that there had been no releases of plutonium (Pu). In 1973, the amount of DU released was 7.4billion Bq (0.2 Ci) and the amount of tritium released was 3.7 billion Bq (0.1 Ci). Much of the data were reported asan annual summary; however, the DU information can be misleading if all releases occurred as a result of briefperiods of testing at the firing sites.
Pantex air releases in 1974 were similar to the previous year. The estimated doses at the fence line were not at levelsknown to cause adverse health effects.
In 1982, more tritium was released to the atmosphere than in previous years. In 1982, the maximum levels of tritiumin air ranged from 0.059 - 0.24 Bq/m3 (1.6 to 6.4 pCi/m3). Although more tritium than usual was released, theestimated dose to the public was less than 0.01 mSv (1 mrem); much less than the 3 mSv (300 mrem) radiationexposure received from normal background (natural radiation sources).
In 1985, elevated levels of tritium were detected off-site; however, the levels were still below levels known to causeadverse health effects and, for comparison, below levels of NRC compliance.
In 1989, a major release of tritium occurred from within the assembly area. Dose assessments developed by DOE andre-evaluated by Battelle in 1994 suggested that tritium doses were well below levels known to cause adverse healtheffects. As late as 1994, tritium continues to be released from the gravel dome covering the release area and soilresulting in continuously decreasing doses (Table 2). The Battelle reassessment of the tritium release model usedindicates that doses from 1990 to 1992 ranged from 4 to 70 x 10-6 mrem.
In these dose assessments, the greatest contributor to dose was fruits and nonleafy vegetables - future public healthactions should (if release occurs again) be taken during the growing season.
Air monitoring for radionuclides (U, Pu, and tritium) in the 1990s shows the atmospheric concentrations of the U andPu radionuclides to be at levels similar or equal to background levels and would not cause adverse health effects. Incomparing the air concentrations around Pantex to other cities in Texas (Austin and El Paso), the air actually containsless radiological contaminants than those two cities. Tritium (H-3) concentrations have been elevated around Pantexin the past as a result of a major release occurring in May 1989. The elevated levels of tritium, however, have notresulted in radiation exposures or doses above levels that would cause adverse health effects.
|Year||Tritium Released||Estimated Dose to the MaximallyExposed Individual|
|1989||1.48 x 1015 Bq (40,000 Ci;accidental release)|| 14.3 µSv (1.43 mrem)|
(assumes uniform release during year)
|1990||9.44 x 1013 Bq (2550 Ci)||1.6 µSv (0.16 mrem)|
(assumes uniform over year - trapped tritium)
|1991||6.29 x 109 Bq (0.17 Ci)||1 x 10-10 Sv (1 x 10 -5 mrem)|
(no major releases)
|1992||4.66 x 109 Bq (0.126 Ci)||0.9 x 10-10 Sv (9 x 10 -6 mrem)|
(no major releases)
Vegetation samples collected and analyzed for tritium suggest that off-site tritium in vegetation is higher than samplescollected on-site. The highest values were from samples collected south-southeast to west of the plant. Thepredominant wind direction is from the south. However, during the 1989 tritium release, the wind was from theopposite direction and was followed by a thunderstorm. Pantex reported the maximum dose as a result of the releasewas toward the east-southeast direction.
Although the levels of tritium in vegetation may be elevated above the on-site values, the levels are well below levelsknown to cause adverse health effects. For example, an individual would have to consume over 5,000 tons of affectedvegetation per year to approach a dose knowned to cause adverse health effects.
In the early years of biota sampling at Pantex, similar results for uranium were seen. Very few samples showedelevated levels of uranium in foodstuffs and these levels were below levels that adversely affect health.
ATSDR obtained Quality Assurance/Quality Control (QA/QC) summaries from EPA and DOE with respect toenvironmental monitoring data. No analytical problems were noted in the QA/QC summaries obtained.
No accessible physical hazards were identified at the site. Protective measures for site workers are included inspecific workplans.
To determine whether people are exposed to contaminants migrating from a site, Agency for Toxic Substances andDisease Registry (ATSDR) representatives evaluate the environmental and human components leading to humanexposure. An exposure pathway consists of five components: (1) a source of contamination, such as drums or wastepits; (2) an environmental medium in which the contaminants might be present or from which they might migrate,such as groundwater or soil; (3) points of human exposure, such as drinking water wells or work areas; (4) routes ofexposure, such as inhalation, ingestion, or dermal absorption; and (5) a potentially exposed population.
Although historical Pantex Plant operations have resulted in contamination of on-site perched groundwater, surfacewater, soil, sediment, and air, no on-site potential or completed exposure pathways are evident from Pantex Plantactivities. Because of the contaminants' isolated locations and security measures at the storage and disposal areas,humans have little opportunity for contact with contamination on site.
The contamination of a downgradient Ogallala drinking water well of a private residence was evaluated as a potentialoff-site exposure pathway. The potential pathway was eliminated because the old well was closed and sealed, and thenew well was constructed in such a manner as to prevent intrusion of the contaminated perched aquifer. In addition, aparticulate and carbon filtration system sampled and maintained by Pantex Plant staff was installed on the newdrinking water well.
Tritium concentrations in air have been elevated in the past as a result of a major release occurring in May 1989. Theelevated air levels of tritium, however, have not resulted in radiation exposures or doses above levels that wouldcause adverse health effects. Although the levels of tritium in off-site vegetation are elevated above the on-site values,the levels are well below levels that would pose a health threat. For example, an individual would have to consumemore than 5,000 tons of affected vegetation per year to approach a dose that would cause adverse health effects.
Radioactivity in the Ogallala aquifer, which is the source of the water supply for the plant and for the City ofAmarillo, is well below the current or proposed Maximum Contaminant Levels and, therefore, is not a health hazard.
Chemical contamination above health screening values has been detected in the perched aquifer at the southeasternplant boundary; however, that particular perched aquifer is not used as a water source downgradient from thecontaminant plume, so no one is exposed to the contaminants. If the aquifer were used in the future as a water source,water from that perched aquifer would require treatment to remove contamination before it would be safe forconsumption.
A release of a hazardous waste does not always result in exposure. People are exposed to a contaminant such as thoseidentified at the Pantex Plant Site only if they come in contact with it; they might be exposed by breathing, eating, ordrinking a substance containing the contaminant or by skin contact with a substance containing the contaminant. Several factors determine the type and severity of health effects associated with exposure to a contaminant. Suchfactors include the exposure concentration (how much); the frequency and/or duration of exposure (how long); theroute of exposure (breathing, eating, drinking, or skin contact); and the multiplicity of exposure (combination ofcontaminants). Moreover, people can be exposed to an environmental contaminant by more than one route ofexposure. Once exposure takes place, characteristics such as age, sex, nutritional status, genetics, lifestyle, and healthstatus of the exposed individual influence how the individual absorbs, distributes, metabolizes, and excretes thecontaminant. Together, those factors and characteristics determine the health effects that might result from exposureto a contaminant.
The Agency for Toxic Substances and Disease Registry (ATSDR) considers the previously described physical andbiologic characteristics when developing health guidelines. Toxicological profiles prepared by ATSDR representativessummarize chemical-specific toxicologic and adverse health effects information. Health guidelines, such as ATSDR'sminimal risk level (MRL) and the Environmental Protection Agency's (EPA) reference dose (RfD) and cancer slopefactor (CSF) are included in the toxicological profiles. Those guidelines are used by ATSDR public healthprofessionals to determine an individual's potential for developing adverse noncancer health effects and/or cancerfrom exposure to a hazardous substance.
Health guidelines provide a basis for comparing estimated exposures with concentrations of contaminants in differentenvironmental media (soil, air, water, and food), depending on the characteristics of the people who might be exposedand the length of the exposure. An MRL is defined as an estimate of the daily human exposure to a contaminant thatis likely to be without an appreciable risk of adverse noncancer health effects over a specified duration of exposure(acute, less than 15 days; intermediate, 15-365 days; chronic, greater than 365 days). Oral MRLs are expressed inunits of milligrams per kilogram per day (mg/kg/day). MRLs are not derived for dermal exposure. The method forderiving MRLs does not include information about cancer; therefore, an MRL does not imply anything about thepresence, absence, or level of cancer risk. An EPA RfD is an estimate of the daily exposure of the human population,including sensitive subpopulations, that is likely to be without appreciable risk of adverse noncancer health effectsduring a lifetime (70 years). Noncancer health guidelines are adjusted downward using uncertainty factors to makethe guidelines adequately protective of the public health. Therefore, the health guidelines should not be viewed asstrict scientific boundaries between what level is toxic and what level is nontoxic. For cancer-causing substances, EPAhas established the CSF as a health guideline. The CSF is used to estimate the number of excess cancers maximallyexpected from exposure to a contaminant.
To link a site's human exposure potential with health effects that might occur under site-specific conditions, ATSDRrepresentatives estimate human exposure to site contaminants from ingestion and/or inhalation of differentenvironmental media. The following relationship is used to determine the estimated exposure to the site contaminant:
|ED||= (C x IR x EF) / BW|
|ED||= exposure dose (mg/kg/day)|
|C||= contaminant concentration|
|IR||= intake rate|
|EF||= exposure factor|
|BW||= body weight|
ATSDR uses standard intake rates for ingestion of water and soil. The intake rate for drinking water is 2 liters per day(L/day) for adults and 1 L/day for children. For incidental ingestion of soil, the intake rate is 100 mg/day for adults,200 mg/day for children, and 5,000 mg/day for children with pica behavior (repeated ingestion of nonnutritivesubstances). Standard body weights for adults and children are 70 kg and 10 kg, respectively. The maximumcontaminant concentration detected in a specific medium at a site is used to determine the estimated exposure; use ofthe maximum concentration results in an evaluation that is most protective of human health. When unknown, thebiological absorption from environmental media (soil, water, etc.) is assumed to be 100%.
For radiological contaminants, ATSDR uses information on radiation exposure and its effects related to environmentallevels prepared by federal agencies, including EPA, Department of Energy (DOE), and the Nuclear RegulatoryCommission (NRC). The agency also uses other publicly available data sources and recommendations on radiationdose limits. The National Council on Radiation Protection and Measurements (NCRP), the International Commissionon Radiological Protection (ICRP), and the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) develop these sources.
Pantex Plant on-site contamination is not considered to pose a health hazard. It is highly unlikely that the generalpublic contacted (past scenario), is contacting (current scenario), or will contact (future scenario) on-site contaminatedenvironmental media. Off-site migration of contamination has been identified in the perched aquifer at thesoutheastern plant boundary; however, that particular perched aquifer is not currently used as a water source in thedirection of contaminant migration, and the sole downgradient private drinking water well has been replaced with anupgraded new well with a particulate and carbon filtration system. Contamination above health screening levels hasnot been detected in the regional source for drinking water, the Ogallala Aquifer.
Because the individual contaminants detected at this site are present at levels not expected to result in adverse healtheffects, ATSDR considers the combined effect of these contaminants as not likely to be of public health concerneither. Research has shown that a mixture produces no adverse health effects in dosed animals when the componentsof that mixture are present at levels below their respective No Observed Adverse Effect Levels (NOAEL); forexample, at concentrations that would have caused no adverse effects in animals treated separately with thosecomponent chemicals. Considering that ATSDR comparison values are typically 100 to 1000 times lower than thecorresponding NOAELS, it is reasonable to expect that environmental contaminants will not produce any combinedeffects, even if their individual concentrations exceed their respective ATSDR comparison values. Therefore, thereare no adverse toxicological implications to Pantex Plant off-site residents.
To address community health concerns regarding the occurrence of certain health conditions in this area, the TexasDepartment of Health (TDH) evaluated data from several existing State of Texas vital records and disease surveillancedatabases. The databases used are described in this section. Depending upon availability, incidence data (new cases)and/or mortality data (deaths) from the four counties closest to the Pantex Plant (Armstrong, Carson, Potter, andRandall) were evaluated; however, there are problems associated with the interpretation of vital record and diseasesurveillance data. A discussion of these problems is presented in the appropriate sections of this report. Anevaluation of the data and answers to questions posed by the community are also provided in subsequent sections.
All data relating to birth defects were provided by the Texas Department of Health Birth Defects Monitoring Division(TBDMD). The TBDMD identified cases of birth defects by examining three types of vital record certificates:
1) Live birth certificates
2) Fetal death certificates
3) Infant death certificates
These certificates, which are available from the Texas Department of Health Bureau of Vital Statistics (BVS), containspecific information on birth defects and cause of death. When a child is born with a birth defect, attending healthcare personnel may indicate the presence of a birth defect by checking the appropriate category of birth defect on thebirth certificate (Appendix E; Table 1). Fetal death certificates also have these check boxes. Additionally, they listthe International Classification of Disease 9th Revision (ICD-9) code for the underlying cause of death. Infant deathcertificates list the ICD-9 codes for all causes of death (underlying cause and others). For birth certificates, birthdefects listed in the check boxes were counted. For fetal death certificates, the birth defects listed in the check boxesand the birth defects listed in the underlying cause of death section of the certificate were counted. For infant deathcertificates, all birth defects in both the underlying and all causes of death sections of the certificate were counted.
For this health assessment, the TBDMD defined a case as an infant or fetus who meets all of the following criteria:
1) Was delivered between January 1, 1990 and December 31, 1994;
2) Had a mother residing either in Armstrong, Carson, Potter or Randall counties at the time of delivery; and
3) Had a birth defect indicated on the vital record.
Because of a change in the type of information required to be reported on birth certificates in 1989, the TBDMDconsiders 1990 as the first year for which reliable data on specific birth defects are available. The last year for whichcomplete data are available is 1994. In addition to analyzing the data for each of the individual four counties, theTBDMD also analyzed the data for Potter and Randall counties combined, and for all four counties combined.
Limitations With These Types of Data
A brief discussion of the limitations associated with these types of data is warranted. In general, analyzing vitalrecord data for many different birth defects may result in the detection of a number of apparent random clusters ofbirth defects in time. Often it is difficult, if not impossible, to distinguish these random clusters from clusters of caseswhich may be caused by common environmental factors. In addition to this random statistical variation there is apotential problem with variations in case ascertainment and case definition. Differences in medical practice,recognition of syndromes, and changes in autopsy services alone often can explain many variations over time in the frequency of specific defects.
Data obtained from live birth certificates are limited by the nature of the document. In Texas, birth certificates arerequired by law to be filed with the State within five days of the birth. The expeditious nature of the filing system is apotential source for reporting bias. For instance, if a birth defect is not readily apparent or additional medical tests arerequired to confirm a specific diagnosis, the birth defect may not be detected prior to the filing of the birth certificate. Reporting of birth defects on birth certificates also may not be uniform throughout the State. Hospitals or birthingcenters that are more fastidious about reporting birth defects on birth certificates would have better reporting than the State as a whole.
Fetal Death Certificates
A fetal death certificate is required for any stillborn fetus delivered after 19 weeks gestation. Similar to the recordingof birth defects on birth certificates, fetal death certificates also are prone to reporting bias. Depending on thegestational age of the fetus, often it is difficult to determine whether the fetus died from a birth defect. This issue iscompounded by the fact that autopsies are less likely to be performed on fetuses. The diagnosis of cause of death maybe more vague because the incomplete formation of organs may preclude the detection of the birth defect. As withbirth certificates, reporting of birth defects on fetal death certificates may not be uniform throughout the State. Hospitals that are more fastidious about reporting defects on the fetal death certificates would have better reportingthan the State as a whole.
The Texas Department of Health obtained data relating to low birthweight infants from the information recorded onbirth certificates. A low birthweight infant is defined as an infant who is born weighing less than 2,500 grams (5.5pounds). The incidence of low birthweight for the period 1990-1994 was determined. A case was defined as an infantweighing less than 2,500 grams at birth who was born to a mother residing in one of the four counties of interest. There are many factors that can affect the birthweight of an infant. These factors are discussed in section VI.C.2 (LowBirthweight) of this report.
All cancer data were provided by the Texas Department of Health Texas Cancer Registry (TCR). The TCR maintainscancer incidence and mortality data for Texas. The TCR obtains mortality data from death certificate informationmaintained by the Texas Department of Health Bureau of Vital Statistics (BVS). Cancer incidence data are acquiredunder the Texas Cancer Incidence Reporting Act (Chapter 82, Health and Safety Code) which requires every generaland special hospital, clinical laboratory, and cancer treatment center to report all cases of cancer to the TCR. Everyinpatient or outpatient case diagnosed with or treated for cancer must be reported to the TCR. Although the TCR is apassive registry that relies on facilities to supply the information, it monitors the number of expected reports fromeach institution and contacts those facilities that fail to report. To ensure that reported data are complete and accurate,TCR staff perform case-finding and other quality control checks at these institutions. The TCR has determined thatfor Public Health Region 1, which includes the counties of concern, cancer incidence reporting is complete for theyears 1985-1993.
The TCR evaluated cancer incidence data for Armstrong, Carson, Potter, and Randall counties for the period 1985-1993. Specifically, the TCR evaluated incidence data for the following cancer sites (types of cancer): leukemia,cancer of the lung, bone, prostate, breast, brain, thyroid, and all cancer sites combined. Cancer incidence data wereanalyzed for Armstrong and Carson counties separately and for Potter and Randall counties combined. The cancerincidence data for Potter and Randall counties were combined because Amarillo is located in more than one countyand zip codes cross county lines; therefore, a cancer diagnosis may not always be coded to the correct county.
To maintain consistency with a previous investigation (11) of cancer incidence data for this area, TCR also analyzeddata for the four major cell-specific types of leukemia; acute lymphocytic leukemia (ALL), chronic lymphocyticleukemia (CLL), acute myelocytic leukemia (AML), and chronic myelocytic leukemia (CML) for the period 1985-1993.
Using death certificate information, the TCR also evaluated cancer mortality for Armstrong, Carson, Potter, andRandall counties for the period 1985-1994. Specifically, the TCR evaluated mortality data for leukemia, cancer of thelung, bone, prostate, breast, brain, thyroid, and all cancer sites combined. Cancer mortality data were evaluated foreach of the four counties separately because the procedural anomaly only occurs with the coding of cancer incidencecases and does not affect cancer mortality data.
One of the limitations with using computerized death certificate cancer mortality data is that only the underlying orprimary cause of death is available. Because people may live for many years with cancer and die from some cause notrelated to the cancer, there is a potential for an under reporting of these specific cancers. Any mortality data analysissuffers from the loss of people contracting cancer but who moved away from the region before they died, as well aspeople who moved into the region with pre-existing cancer.
In Texas, muscular dystrophy, multiple sclerosis, amyotrophic lateral sclerosis, and lupus erythematosus are notreportable diseases; therefore, incidence data are not available. However, mortality data for these diseases in each ofthe four counties and in Potter and Randall counties combined are available for the period 1980-1994 from deathcertificate information provided by the Texas Department of Health Bureau of Vital Statistics.
As with cancer mortality data, there also are limitations with computerized death certificate mortality data for otherchronic diseases which may result in differences in the reporting of these conditions. Diagnosis of these conditionsmay be difficult and may depend on the diagnosing physician. This could effectively reduce our confidence in theresults when comparing rates from one area to another. This issue is further addressed in Appendix F.
For all health conditions examined below, the observed occurrence was compared to the "expected" occurrence usingratios. The expected occurrence was based on the occurrence observed in a reference population, usually the State ofTexas as a whole. In some instances State of Texas data were not available; thus, other reference populations wereused. For birth defects and low birthweight babies, the number of cases observed was divided by the numberexpected, producing an observed:expected ratio or OER. For cancer and chronic diseases, the ratio of observed toexpected number of cases (incidence) or deaths (mortality) was examined and the information was furtherstandardized to eliminate possible effects due to race, sex, and age. These ratios are referred to as the standardizedincidence ratio (SIR) or standardized mortality ratio (SMR).
When any of the above ratios is equal to one (1.00), then the number of observed cases/deaths is equal to the numberof cases/deaths that would have been expected based on the incidence/mortality experience of the referencepopulation. When the ratio is less than 1.00, fewer people have the disease or have died from the disease than wouldhave been expected. Conversely, a ratio greater than 1.00 may indicate that more people have the disease or have diedfrom the disease than we would have expected.
Because rates and ratios fluctuate from year to year, one can only estimate the underlying ratio. To determine theprecision of our estimate, statistics are used to calculate a 95% confidence interval (95% CI). This is an estimate ofthe range in which one would expect the underlying ratio to fall 95% of the time. If the 95% CI includes 1.00, thenwe are reasonably certain that the ratio is within the range that would be expected based on the reference population. When the 95% CI excludes 1.00, the ratio is not within the range that would be expected based on the referencepopulation, and is "statistically significant". As defined here, "statistically significant" means that there is less than afive percent chance that the observed difference is merely the result of random fluctuation in the number of observedcases. The precision of our estimate of the underlying ratio varies inversely with the width of the confidence interval. A narrow confidence interval indicates that the estimate of the underlying ratio is precise. Conversely, a wideconfidence interval indicates that the estimate of the underlying ratio is not very precise. Confidence intervals werenot calculated where there were no observed cases.
Care should be taken when interpreting the meaning of statistical significance. To report that a result is statisticallysignificant merely means that the result was unlikely to have occurred by chance. Specifically, statistical significancemeans that the likelihood of the result having occurred by chance is small. A statistically significant result does notnecessarily mean that the result is significant in the everyday meaning of the word.
Interpreting statistically significant results often is difficult and requires the consideration of several factors. Inaddition to the magnitude of the observed to expected ratio; the number of observed cases, the number of expectedcases, the width of the confidence interval, and the source of the data all must be considered. For example, in the birthdefects tables, one observed case of "other central nervous system anomalies" was 55.73 times what we would haveexpected. However, based on the reference population, the expected number of cases was 0.0179. Because it is notpossible to observe a fraction of a case, observing as little as one case with an expected value less than one results in arelatively large ratio (55.73). In this example the confidence interval tells us with 95% confidence that the underlyingratio could be anywhere from 1.41 to 311.26; however, the width of the confidence interval tells us that in thisinstance our estimate is not very precise. Although the observed to expected ratio is statistically significant, the smallnumber of observed cases and the lack of precision would make it difficult to provide, with any degree of certainty, ameaningful interpretation.
Care also should be taken when interpreting a statistically significant result based on adequate numbers and precision. Other factors besides biology could be responsible. For instance, categories that include the term "other" in theirdescription are not very specific. Many types of defects are included in these categories. Thus, it would be verydifficult to tell if a "statistically significant" result was due to slight (non-significant) elevations in many defects or if it is due to largerincreases in one or two specific defects. Differences in reporting practices also could account for apparent statisticaldifferences between populations.
For each type of vital record, the TBDMD compared the observed number of cases for each category of birth defect tothe number that would have been expected. The number of expected cases was calculated using prevalence rates forthe entire State from the same vital record source (e.g. county birth certificates compared to birth certificates for allTexas).(12) The TBDMD did not adjust the ratios for race and maternal age; they determined that it would probablyhave a low impact for the majority of birth defects.
The results of analyses based on birth certificate data are presented in Appendix E; Table 2. For several types of birthdefects, the observed number of cases exceeded the expected number. In Armstrong County, six of the birth defectcategories had OERs greater than one; however, only one, "other central nervous system anomalies", was statisticallysignificant. In Carson County, five of the birth defect categories had OERs greater than one; only one category, "othergastrointestinal anomalies", was statistically significant. In Potter County, 20 of the birth defect categories had OERsgreater than one and 11 were statistically significant. Five of the categories that were statistically significant werenonspecific "other" categories. Two of the statistically significant categories had expected values less than one. InRandall County, 20 of the birth defect categories had OERs greater than one and eight were statistically significant. Five of the categories that were statistically significant were nonspecific "other" categories. One of the statisticallysignificant categories was based on an expected value less than one.
When all four counties were combined, OERs were statistically significant in 12 of the 23 birth defect categories. Five of these 12 categories were the nonspecific "other" categories. One category, "other congenital anomalies",exhibited significantly fewer cases than expected. Overall, for the four counties combined, the number of infants whohad birth defects noted on the birth certificate was 2.16 times more than the number expected in the four counties, andwas statistically significant. For reasons described previously, it is difficult to interpret statistical results with respectto the "other" categories because many different defects could be included in each of these categories. However, forindividual counties, Potter and Randall counties combined, and all four counties combined there were severalclinically clear (do not include "other" in their description) categories that were statistically significant. In somecases, these results are based on five or more observed cases, more than one expected case, and relatively narrowconfidence intervals. In these instances, random chance alone may not be responsible for the results.
One possible explanation for these results is that these excesses are a consequence of fastidious hospital reportingpractices. There are several reasons which support the role of fastidious reporting in explaining the results for thisarea. First, approximately three-fourths of all births to residents of Potter and Randall counties take place atNorthwest Texas Hospital (NTH). Thus, the reporting practices of that hospital would be expected to stronglyinfluence the overall statistics for birth defects reported for these counties. In the past, concern about high rates ofbirth defects from the Amarillo area was raised by area residents.(13) Generally, birth defects are under reported onvital records. If previous concern about birth defects resulted in more fastidious reporting, comparing birth defectsfrom this area (obtained from birth defects noted on birth certificates) to an expected number of birth defects based onthe State experience may not be appropriate and could result in artificially produced excesses.
In an attempt to rule out more fastidious reporting as a possible explanation for the statistically significant excesses,we compared the data from the four counties to two active surveillance systems (the California Birth DefectsMonitoring Program, CBDMP, and the Metropolitan Atlanta Congenital Defects Program, MACDP)[Appendix E;Table 3]. Rates obtained from active surveillance systems allow the most accurate estimation of the expected numberof cases for a given area. If birth defects observed in the four counties were higher than the expected number based onrates reported by the active surveillance systems, then reporting bias would not be sufficient to explain the excess. When this comparison was made, no significant excesses were observed; therefore, more complete reporting in thisarea cannot be ruled out as an explanation for the statistically significant excesses obtained using birth certificateinformation. Some of the specific birth defect categories did not have equivalent diagnoses among the California orAtlanta registries and, therefore, could not be compared.
The TBDMD was able to examine the birth certificate data with respect to parental occupation and place ofemployment.(14) Additionally, they were able to look at the distribution of the birth defects by zip code. They didnot find anything unusual with respect to parental occupation or workplace. Very few parents of children reported tohave been born with birth defects worked at the Pantex Plant. Some of the fathers of affected children worked in meatprocessing, but this is a common occupation in Amarillo. One zip code, 79107 which extends from the western edgeof the Pantex Plant along the Potter County/Carson County border towards Amarillo near the plant, appeared to havesignificant elevations for several of the birth defect categories (Appendix E; Table 4). Many of these excess caseseither were based on observed values less than five, expected values less than one, or nonspecific birth defectcategories that include "other" in their description. Reporting practices may explain the statistically significant resultsfor three of the birth defect categories; heart malformations, malformed genitalia, and club foot. The 79107 zip codeis in Potter County and had the highest number of reported live births (3,529) for any of the zip code areas studied inthe four county area. Because the majority of births to residents of Potter County take place at NTH, fastidiousreporting practices cannot be ruled out as a possible explanation. Statistically significant excess for these birth defectcategories also was observed in other zip code areas. Microcephalus was elevated in 79121; heart malformations waselevated in 79124, 79108, 79106, 79101, 79102, 79104, 79109, 79103, and 79015; malformed genitalia was elevated in 79110; and club footwas elevated in 79015 and 79068. No clear pattern was seen with respect to increasing ratios and proximity to Pantex.
Fetal Death Certificates
From 1990-1994, in the four counties combined, there were 20 fetal deaths where birth defects were indicated as acause of death (Appendix E; Table 5). Although "hydrocephalus" shows a statistically significant excess of 40.22times the expected number in Carson County, this excess is based on one observed case, an expected number of lessthan one case (0.0249), and an extremely wide 95% confidence interval which barely excludes 1.00 (1.02-223.76). For reasons outlined previously in this report we do not consider this statistically significant result meaningful. InPotter County, based on nine cases, the category "other congenital anomalies" was 2.64 times expected and wasstatistically significant; however, this is a broad based category with nonspecific diagnoses. As mentioned previously,it is difficult to interpret a nonspecific category that includes "other" in its description.
The portion of the fetal death certificate which lists the "underlying cause of death" also yielded sporadic statisticallysignificant results (Appendix E; Table 6). In Carson County, "other congenital anomalies of the circulatory system"(ICD-9 code 747) was 597.49 times what we would have expected; however, in addition to being a nonspecificcategory, this result was based on one case, an expected number of cases less than 1.00 (0.0017), and a very wide 95%confidence interval (14.89 to 3,277). Randall County had 2 cases of "other congenital anomalies of the heart" (ICD-9code 746) which was 9.74 times the expected number of less than one (0.205) with a 95% confidence limit that rangedfrom 1.18 to 35.17. Although these results are statistically significant, the small number of observed cases, the lack ofprecision in the estimates, and the nonspecific nature of the categories would make it difficult to provide a meaningfulinterpretation of these results.
Death Certificates for Infants
The TBDMD examined death certificates for infants (children less than one year old). In Carson County, two cases ofmajor heart defects 'bulbus cordis anomalies' and 'anomalies of cardiac septal closure' (ICD-9 code 745.0-745.9)were found to be statistically significant at 21.84 times the expected number (Appendix E; Table 7). This was theonly significant excess or deficit observed among the four counties. Because this finding was based on two cases, anexpected number of cases less than one (0.0916), and a relatively wide confidence interval (2.64 - 78.87), we wouldnot interpret these results as indicating an increased risk for these defects in this area.
Using birth certificates information, the TBDMD found that several categories of birth defects were significantlyelevated in specific counties and in the four counties grouped together. In some cases, the results for individualcounties were based on few observed cases, less than one expected case, and relatively wide confidence intervals. Inthese cases, it would be difficult to attach much importance to findings of statistical significance because ourconfidence in the precision of the data would be limited. In other cases, the category of defect on the birth certificatewas such that many nonspecific diagnoses could be included within the category. It is difficult to interpret theimportance of statistically significant findings for categories that can potentially include many different types of birthdefects. When such increases are observed it is impossible to determine whether the increase is the result of slightelevations among many types of birth defects or the result of a large increase in one or two birth defects which results in a significant overall increase.
For Potter County, Randall County, Potter and Randall counties combined, and the combined four county area, theTBDMD found a statistically significant excess in the reporting of several specific categories of birth defects. Manyof these elevated ratios may be due to factors other than random chance because they are based on a substantialnumber of observed cases, populations large enough to result in reasonable expected values for comparison, andrelatively tight confidence intervals.
Generally, birth defects are under reported on vital records. Thus, using the entire State as the comparison populationcould result in depressed expected rates. In this area, the majority of all live births take place at Northwest TexasHospital (NTH). Therefore, the reporting practices of this hospital could greatly influence the observed rates for thisarea. In an attempt to rule out more complete reporting as the cause, the TBDMD compared the rates observed forthis area to two active surveillance systems. Because active surveillance systems provide the most accurate results incollecting birth defects, exceeding the rates reported by these systems would eliminate reporting bias as a possibleexplanation for these results. When this comparison was made, they did not find any significant differences betweenthe rates for this area and those of the active surveillance systems. Thus, more complete reporting in this area cannotbe ruled out as an explanation for the statistically significant excesses obtained using birth certificate information.
Among the 390 comparisons made using fetal and infant death certificate information (Appendix E; Table 5-7), wewould have expected 5% or 19 of them to be "statistically significant" by chance alone. Only five comparisons inthese analyses showed a significant excess of a specific birth defect, each of those was based on very few cases withexpected values less than one. Additionally, there was no consistency regarding the specific type of defect acrosscounties. Consequently, these vital records do not offer compelling evidence of an excess occurrence of birth defects.
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. Forexample, microcephaly may be caused by one of several inherited syndromes, by degenerative brain disorder, birthtrauma, intrauterine infection, or exposure to radiation 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 rangeof birth defects for which statistically significant excesses were noted argues against a single causative physical orchemical agent.
To determine if there was an excess number of low birthweight babies born in each of the four counties (Armstrong,Carson, Potter, and Randall), the number low birthweight babies born in each county with the number that would beexpected based on State rates was compared. Statistically significant excesses in the number of low birthweightbabies born in Carson and Potter counties for the time period 1990 to 1994 (Appendix E; Table 8) was found. Basedon the number of observed and expected cases and the narrow confidence intervals, we are confident in the precisionof these results. However, the slight but statistically significant excesses are difficult to interpret; particularly becausegestational age could not be accounted for in this analysis and local reporting practices may partially be responsiblefor these findings.
The majority of births in this area are delivered at Northwest Texas Hospital (NTH). Evidence indicates that NTHstrictly follows Texas Department of Health policy to file a birth certificate for all live births, regardless of gestationalage.(15) Discussions with staff at NTH indicated that there was a strict and well-established practice for deliveryroom staff to send all infants with any life signs, regardless of gestational age, to neonatology. Because infants sent toneonatology would be considered live births, birth certificates would be filed. Some hospitals may report verypremature infants as fetal deaths or may not report premature births with gestational ages less than 20 weeks. Thus,the practice of reporting very premature infants as live births may not be uniform throughout the State. Birth recordsfrom 1991-1994 documented a higher rate of births of infants less than 24 weeks gestation at NTH (4.85 per 1,000live births) compared to the State of Texas (1.96 per 1,000 live births).(15) Because gestational age could not beaccounted for in this analysis we cannot rule out differences in gestational age as a potential explanation for theseresults.
Although reporting practices may not completely explain the elevated rates for this area, there are several risk factorsthat increase a woman's chances of giving birth to a baby born with a low birthweight. Mothers who smoke, drinkalcohol, abuse drugs, or have poor nutritional habits during pregnancy may have an increased risk for low birthweightbabies. In addition, maternal age and the number of previous live births, are other examples of factors that can effectthe developing fetus. In summary, there are many factors some of which can be controlled by the mother and otherswhich cannot that play an important role in the health of the developing fetus.
To determine if there is an excess of specific types of cancer in the counties of interest, the observed number ofcancer cases (incidence) and cancer deaths (mortality) for each selected type of cancer to what would be "expected"were compared. For cancer incidence, the expected number of cases was determined using race-, sex-, and age-specific cancer incidence rates for California during 1988 to 1992. California rates were used because cancerincidence data for Texas are incomplete for that time period. Bone cancer rates were not available for California,therefore, cancer incidence rates for five regions of Texas during 1985 to 1991 were used to calculate expected bonecancer cases. For cancer mortality, the expected number of deaths was determined using the mortality experience ofthe State of Texas.
No significant excess of cancer incidence was observed among male or female residents of Armstrong or Carsoncounties (Appendix E; Tables 9 and 10) during the period 1985-1993. (16) However, a statistically significant excessof cancer incidence was observed for all cancer sites combined among females in the combined counties of Potter andRandall (Appendix E; Table 11) during the same time period. The public health significance of this excess is difficultto evaluate. The calculated Standardized Incidence Rate (SIR) is based on a large number of observed and expectedcases (4,015 and 3,693 cases; respectively). Because the 95% confidence interval is narrow, we are fairly confident inthe precision of this estimate of the SIR; however, the SIR barely exceeds one (1.0). Because the SIR barely exceedsone and the category "all sites" is nonspecific and includes all types of cancer; we would interpret this resultcautiously. The statistically significant excess could be the result of slight (nonsignificant) elevations among manydifferent cancer sites or the result of a large increase in one or two sites. Interpreting increases in all cancer sitescombined is further complicated by the fact that known causes for individual cancer sites differ.
In a previous evaluation of cancer incidence data for this area, an analysis of the four major cell-specific types ofleukemia [acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), acute myelocytic leukemia(AML), and chronic myelocytic leukemia (CML)], showed a significant excess of CLL during the period 1986-1992among females in the combined counties of Potter and Randall. To maintain consistency in the investigation ofcancer data in this area, the major leukemia subgroups were analyzed again for the period 1985-1993. There was asignificant excess of CLL among males in the combined counties of Potter and Randall; however, unlike the previousinvestigation, the number of CLL cases among the female residents in these two counties was within the expectedrange (Appendix E; Tables 12 and 13).
CLL appears to have a strong inherited susceptibility component and is primarily confined to the late middle-aged andelderly (the majority of these cases were in individuals age 65 years or older). It is very rare in Asians and remainsrare in Asians who migrate to western nations, which indicates the importance of genetic factors. Unlike other formsof leukemia, CLL has not been causally related to radiation exposure. The significant excess of CLL among males isa new finding as was the excess of CLL among females in the 1994 study and deserves further investigation.(11)
In response to a resident's request, the TCR analyzed the incidence of one additional cancer (malignant pleuralmesothelioma). Mesothelioma is a rare form of cancer with about 2,000 cases diagnosed in the United States everyyear. Most people who develop this form of cancer have a history of exposure to asbestos. For the period of 1985-1993, 16 cases of mesothelioma were diagnosed in the four counties of concern (Armstrong: 0, Carson: 1, Potter and Randall: 15). Based on the U.S. age-adjusted rate, the expected rate is one per 100,000 or 14.8 cases for the fourcounty area. The 16 observed cases are well within the range that would be expected for the area (SIR = 1.08, 95% CI= 0.62, 1.76).
For cancer mortality, no significant excess was observed among male or female residents of Armstrong or Carsoncounties (Appendix E; Tables 14 and 15) during the period 1985-1994. A statistically significant excess of deathsfrom prostate cancer was observed among males in Potter and Randall counties (Appendix E; Tables 16 and 17). Although we cannot directly explain this excess, it is important to note that it is not consistently supported byincidence data. The differences seen in prostate cancer incidence and mortality could result from past under-reportingof prostate cancer cases (prostate cancers are now more readily diagnosed in non-hospital settings), or could beexplained by differences in early diagnosis and treatment in this area compared to the rest of the State.
A statistically significant excess number of deaths due to all cancer sites was observed for males in Potter County. The public health significance of this excess is difficult to evaluate. The calculated SMR is based on a large numberof observed and expected deaths (1,140 and 1,045 deaths; respectively). Because the 95% confidence interval isnarrow, we are fairly confident in the precision of this estimate of the SMR; however, the SMR barely exceeds unity(1). Because the SMR barely exceeds one and the category "all sites" is nonspecific and includes all types of cancer;we would interpret this result cautiously. The statistically significant excess could be the result of slight(nonsignificant) elevations in deaths from many different types of cancer or the result of a large increase in deathsfrom one or two types of cancer. Interpreting increases in deaths from all types of cancer combined is furthercomplicated by the fact that known causes for individual types of cancer differ.
The TCR found a statistically significant excess of cancer incidence for all cancer sites combined among females inthe combined Potter County/Randall County area. When such increases are observed it is impossible to determinewhether the increase is the result of slight elevations among individual cancer sites or the result of a large excess inone or two cancer sites which results in a significant overall increase. Based on available information, it would bedifficult to provide, with any degree of certainty, a meaningful interpretation for these results.
There was a significant excess of CLL among males in the combined counties of Potter and Randall. CLL is aspecific type of cancer. Considering the previous finding of an excess of CLL among female residents from these twocounties, we believe that the occurrence of CLL in these counties deserves further investigation.
For cancer mortality, a statistically significant excess of deaths from prostate cancer was observed among males inPotter and Randall counties. This finding was not consistent with the incidence data. The differences seen in prostatecancer incidence and mortality could result from past under reporting of incident prostate cancer cases or could beexplained by differences in early diagnosis and treatment in this area compared to the rest of the State.
Cancer is a very common disease, much more common than most people realize. Approximately four out of every tenpersons alive today will be diagnosed with some type of cancer in their lifetime. Furthermore, cancer is not onedisease, but many different diseases. Different types of cancer are generally thought to have different causes. InTexas, as in the United States, cancer is the second leading cause of death, exceeded only by heart disease. In 1995,31,571 Texans died of cancer. Sixty-five percent of these deaths were in persons 65 years of age or older. Finally, ittakes time for cancer to develop, usually 20 to 40 years. Conditions that have prevailed for only the last 5 or 10 yearsare unlikely to be related to the current incidence of cancer in a community.
The occurrence of cancer may vary by race/ethnicity, gender, the type of cancer, geographic distribution, populationunder study, and a variety of other factors. Scientific studies have identified a number of factors for various cancerswhich may increase an individual's risk of developing a specific type of cancer. Some of these factors are: heredity,diet, age (cancer risk increases with age), family history, exposure to certain chemicals (only a limited number ofchemicals 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. Pollution andoccupational exposures are estimated to collectively cause 4-6% of all cancer deaths.
Mortality due to muscular dystrophy, multiple sclerosis, amyotrophic lateral sclerosis, and lupus erythematosus forArmstrong, Carson, Potter, Randall, and Potter/Randall counties combined for the time period of 1980-1994 aresummarized in Appendix E; Tables 18-22. To determine if there was an excess of deaths due to each of thesediseases, the number of deaths observed in this area for each disease was compared to the number of deaths that wouldbe "expected" based on the age-, sex-, and race/ethnicity-specific mortality experience for the State of Texas. Standardized mortality ratios (SMRs) were calculated and evaluated as described previously in this report. SMRswere not calculated when no cases of the disease were reported.
In both Carson and Potter counties there was a statistically significant elevation in the number of observed deaths dueto muscular dystrophy for males (Appendix E; Table 19-20). In Randall County and in Potter/Randall countiescombined, there was a statistically significant elevation in the number of observed deaths due to multiple sclerosis forfemales (Appendix E; Table 21-22). For males in Potter/Randall counties combined, there was a statisticallysignificant excess of amyotrophic lateral sclerosis. Deaths due to lupus erythematosus were not found to be excessivein any of the four counties of concern.
Incidence data were not available for these diseases therefore we used mortality data. In general, mortality data forthese diseases are difficult to interpret because they are diseases that people may have for many years with death oftenresulting from other causes. Caution must be exercised when interpreting the elevations among the four county area. All of the counties are sparsely populated and even one additional death can result in an elevated mortality ratio. Thecauses associated with each of these diseases are still very speculative. Because of the nature of these data we are notable to provide, with any degree of certainty, a meaningful interpretation.
Genetics is the primary risk factor associated with muscular dystrophy. This means that individuals who haverelatives who had 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. Inaddition to the genetic component, some other factors that have potentially 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 have been discussed in thescientific and medical literature. In addition to genetics, prior trauma, heavy milk consumption, heavy physical labor,occupational exposure to chemicals involved in the manufacture of plastics, and exposure to infectious agents prior tothe onset of disease have all been implicated in the development of amyotrophic lateral sclerosis.
Lupus erythematosus, like the other diseases, also has a strong genetic association with its development. In addition,exposure to specific chemicals and toxins, dietary factors, and exposure to infectious agents prior to the onset ofdisease have been implicated in the development of lupus.
The Agency for Toxic Substances and Disease Registry's (ATSDR) Child Health Initiative recognizes that the uniquevulnerabilities of infants and children demand special emphasis in communities faced with contamination of theirwater, soil, air, or food. Children are at greater risk than adults from certain kinds of exposures to hazardoussubstances emitted from waste sites and emergency events. They are more likely to be exposed because they playoutdoors and they often bring food into contaminated areas. They are shorter than adults, which means they breathedust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemicalexposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for riskidentification and management decisions, housing decisions, and access to medical care.
ATSDR evaluated the likelihood for children, living within 5 miles of the Pantex Plant, to be exposed to plantcontaminants at levels known to cause adverse health effects. ATSDR did not identify any currentexposure pathways for children. The perimeter of the plant is fenced and guarded, preventing children fromwandering into areas where environmental contamination exists. Unless these conditions change, there should not beany future exposure situations in which children may be exposed to chemical contaminants from the Pantex Plant.
The Texas Department of Health (TDH) evaluated health outcome data for birth defects, low birth weight, and specificcancers of community concern. These evaluations are discussed in the Health Outcome Data and Health OutcomeData Evaluation sections. Though there are no pathways identified which may expose children, TDH recommendedsurveillance of birth defects at area hospitals and birthing centers to better compare rates to other surveillance systemsin the United States.
Using information obtained from birth certificates, fetal death certificates, and infant death certificates, the TexasDepartment of Health found that the observed number of cases and/or deaths for several categories of birth defects inthis area are higher than what would be expected based on comparison to State rates. Although better reportingpractices could not be ruled out as a possible explanation for the higher than expected number of cases in this area,TDH also could not rule out the possibility that the apparent excesses are real. TDH is currently in the process ofexpanding an active birth defect surveillance system into this area beginning with 1998 deliveries. Data from thisactive surveillance system will be used to evaluate the accuracy and completeness of vital records in this area.
Information obtained from birth certificates indicates the rate of low birth weight babies born in Carson and Pottercounties was higher than the rate reported for the State of Texas. Northwest Texas Hospital, the main birthing centerfor this area, strictly adheres to TDH policy to file a birth certificate for all live births regardless of gestational age. Previous discussions with hospital staff indicate that all infants with any life signs, regardless of gestational age, areconsidered live births. This practice of reporting very premature births as live births may not be uniform throughoutthe State. Some hospitals may report very premature births as fetal deaths, and some may not report premature birthswith gestational ages less than 20 weeks.