PUBLIC HEALTH ASSESSMENT
US DOE MOUND FACILITY
[a/k/a MOUND PLANT (USDOE)]
MIAMISBURG, MONTGOMERY COUNTY, OHIO
APPENDIX A: HISTORIC RELEASES OF NONRADIOACTIVE SUBSTANCES TO WATER AND AIR
Background
In this appendix we review data describing releases of nonradioactive substances from the Mound facility to the environment. The Mound environmental monitoring reports are the primary source of the data. This Appendix is intended to supplement information presented in the Environmental Contamination and Evaluation section in the main body of this public health assessment. This discussion is divided into considerations of nonradioactive substances in water and nonradioactive substances in air.
Exposures to Nonradioactive Substances in Water
ATSDR scientists reviewed Department of Energy (DOE) data (1971-1995) in the Mound environmental monitoring reports for nonradioactive liquid effluents to the Great Miami River and the Miami-Erie Canal. Mound employees did not routinely sample the river itself for nonradioactive substances because there have always been many other contributors of nonradioactive substances to the river upstream from Mound. Initially, the effluent data represented analyses of a composite sample from each of Mound's liquid effluent streams. After 1974, the effluent streams to the Great Miami River and the Miami-Erie Canal were analyzed separately.
From 1971 to 1975, Mound employees compared levels of nonradioactive substances in liquid effluents to Environmental Protection Agency (EPA) Surface Water Criteria for Public Water Supplies. In July 1975, the Mound Laboratory received an EPA National Pollutant Discharge Elimination System (NPDES) permit, which specifies how effluent streams will be sampled and what criteria they must meet. The sampling criteria under the Mound permits were substantially revised in 1981. The State of Ohio became the administrator of the permits when they were renewed and modified in 1985. The permits were renewed with modifications in 1992, and modified again in 1994. The data collected under the effluent regulatory system and published in the Mound annual environmental reports are the subject of this portion of our review.
Over the 25-year period (1971-1995), there have been numerous instances where the standards for the effluent streams set by the NPDES permits (or their predecessors) were exceeded; however, there have been far fewer such instances since 1985, when the Ohio EPA ordered Mound officials to take corrective actions to control the release of suspended solids. ATSDR scientists consider the standards outlined in the NPDES permits to be protective of the public's health. Many of the recorded instances where effluent streams exceeded test standards during the 25 years have been related to releases from the sanitary (sewage) treatment facility. Effluent tests that indicate performance of the sanitary (sewage) treatment facility include suspended solids, chlorine, fecal coliform, and biochemical oxygen demand. Reasons given in the reports for exceeding permit standards include equipment problems, high rains or melting snow, and salting roads to remove snow and ice. Rain, snow, and salt affect the surface runoff and change the quality of the effluent streams. There were also occasional instances where oil and grease exceeded standards in the earlier years and other times when copper, iron, and nickel exceeded standards. There was one instance (1989) where 1,1,1-trichloroethane was slightly above standards. In nearly all of these cases, deviations from the standards were small.
ATSDR scientists are not concerned that any of these data represent a public health hazard except the fecal coliform bacteria test results in the early 1980s. During a period from 1981 through 1986, there were one or more instances each year where fecal coliform bacteria exceeded the standard. In 1982, 1983, and 1984, the levels were 12, 8, and 12 times the standard, respectively. (The standard was 2,000 MPN per 100 mL [milliliters], maximum reading, where MPN stands for "most probable number" and is a way of counting bacteria colonies in the laboratory.) We are concerned that people swimming and boating in the Great Miami River at the recreational facility at the Chautauqua Dam might have been exposed to pathogenic microbiological organisms because of fecal pollution from the Mound facility.
The 1982, 1983, and 1984 fecal coliform maximum readings were the only three that were at levels of concern among the 6 years when the standards were exceeded. In 1984, the high fecal coliform reading occurred in January. Since we do not know of anyone who was swimming in the river in January, we do not believe there was any public health hazard associated with this release. In 1982 and 1983, however, the high readings occurred in August. The effluents released from the Mound site on these sampling dates did pose a health hazard to people engaged in recreational activities downstream in the Great Miami River. The most common health effects from exposure to these releases, if any, would have been gastroenteritis, Giardiasis, Salmonellosis, and Shigellosis [1, 2]. These releases are not persistent contaminants in the environment, and they would not pose a long-term public health problem.
Conditions in the Great Miami River may not have been conducive to the survival of microorganisms on the days that high levels of fecal coliform were present in Mound's liquid effluents. The river may have been chemically or physically toxic to microorganisms. On the other hand, we have taken into account dilution in the river, and we consider that the temperature of the water in August was likely conducive to the multiplication of bacteria and other microorganisms. We don't know what the actual conditions were, so we consider the releases a health hazard.
In addition to the data we've just described (NPDES data), ATSDR scientists considered what historical water release information we are missing.
In the 1950s, nonradioactive liquid releases to the Great Miami River included strong inorganic acids, citric acid, formic acid, detergents, soaps, chelating agents, lubricating oils, organic solvents, sodium hydroxide, sodium tartrate, formaldehyde, and many other substances [3]. These chemicals were released to the waste stream that flowed off site to the river without restriction [3]. There is no indication that liquid chemical wastes were ever released to the Miami-Erie Canal.
We do not know the quantities of nonradioactive substances released to the river, or those already in the river, during this time period. Therefore, we are not able to estimate doses to people who swam, boated, or engaged in other recreational activities in the Great Miami River before 1971, and ingested or breathed nonradioactive substances from the river, or got water on their skin or ate fish from the river.
In summary, there were two instances in the early 1980s when the Mound facility released to the environment liquid effluent containing nonradioactive contaminants that posed a public health hazard. The contaminants are pathogenic microorganisms. There are no other documented releases of nonradioactive substances from Mound at levels that posed a public health hazard; however, we do not know how much chemical pollution Mound Laboratory employees released to the Great Miami River in the 1950s.
Exposures to Nonradioactive Substances in Air
Mound scientists began reporting particulate matter concentrations on and off site in 1971 [4]. The standard was 60 micrograms per cubic meter (µg/m3), annual geometric mean, from 1972 through 1993. The National and the Ohio Ambient Air Quality Standards for particulate matter were changed (made more stringent) to 50 µg/m3, annual arithmetic mean, in 1994. In the 1970s and the early 1980s, air particulate matter concentrations regularly exceeded the Ohio Ambient Air Quality Standard both on site and off site at the Mound facility. Since 1989, all the Mound air particulate matter concentration measurements have met the standards. However, the U.S. EPA is currently implementing further changes to the air particulate matter standards (making them more stringent again) to reflect newer information about the toxic effects from breathing particulate matter. Therefore, air particulate matter concentrations that met ambient air quality standards historically would not necessarily meet the newly proposed ambient air quality standards.
Many particulates do not exhibit a specific toxic effect but may still inhibit the clearance mechanisms in the lungs or, at relatively low concentrations, cause sensitization or allergic reactions in sensitive individuals. The Ambient Air Quality Standards for particulate matter were established to protect the public from excessive, respirable, solid material in air. The standard specifies a mass concentration in air and not the chemical identity of the solid material. The standard today applies to particulate matter that has an aerodynamic diameter of 10 micrometers or less [5]. This size of particulates describes "respirable" particles. Larger particles are exhaled or swallowed during the normal breathing process and do not cause health problems. Mound's data is derived by weighing filter papers from the air monitors before and after pulling air through them. This method (gravimetric) results in a total particulate mass that may include particles larger than 10 micrometers; to the extent that it does, the data overstate the health hazard. Since we don't know what portion of the data represent respirable particulates, we don't know whether the air quality was ever a problem. To the extent that air particulate matter under 10 micrometers exceeded the standard, more people could have experienced allergic reactions and difficulties breathing.
Mound's environmental reports state that the particulate matter measurements are a measure of the ambient air quality in the area and that emissions from the site add a "negligible contribution" to the ambient air. This may be true. The Mound facility did not exceed emissions standards during the years that particulate concentrations at air monitors exceeded ambient air quality standards. Nevertheless, we have very little data for nonradioactive substances in air before 1976 and none before 1971.
ATSDR scientists reviewed information pertaining to the sources of nonradioactive airborne emissions from Mound. Since 1971--and possibly much earlier than that, although we don't know how early--the primary source of nonradioactive emissions to the air from the Mound facility has been the site steam power plant. The power plant operates on natural gas except in very cold weather, when it is converted to No. 2 fuel oil. Mound scientists began reporting emissions of particulates and sulfur dioxide from the power plant, organic compounds from the paint shop, and particulates from the explosives disposal and fire-fighting training areas in 1976. Other sources for nonradioactive air emissions mentioned in other environmental reports include maintenance grinding operations, carpentry shop operations, and construction and deconstruction activities on site. In 1994, Mound staff stopped reporting air emissions by on-site operations and simply reported air emissions as total suspended particulates, sulfur oxides, nitrogen oxides, volatile organic compounds, carbon monoxide, and lead.
Mound employees burned solid and liquid wastes in Area B from 1948 to 1969 [6]. The Mound Plant RI/FS (Remedial Investigation/Feasibility Study) Site-Wide Work Plan contains the following description of these materials: "administrative and laboratory trash including paper, glass, wood, plastics, kitchen garbage, ...bottled urine samples ...[and] perhaps ...beryllium, mercury, trichloroethene, carbon tetrachloride, nickel carbaryl, benzene, alcohol, photo processing solutions, and plating materials..." [6]. The State of Ohio enacted a law banning non-permitted, open burning in 1969, and the practice was discontinued. Since it was legal, we expect that open burning was a wide-spread practice on both public and private properties throughout the period before it was banned. We are not able to estimate the inhalation exposures to air emissions from these activities at the Mound Laboratory because we do not know the quantities of the emissions. We note, however, that burning wastes containing metals (beryllium, mercury, and nickel) can result in very toxic airborne particulate matter [7].
In summary, the available data for nonradioactive air emissions from Mound (1976-1995) do not indicate that the emissions were at levels that would cause adverse health effects. The reported air particulate matter concentrations, both on and off site, have not exceeded EPA and Ohio Ambient Air Quality Standards since at least 1989. However, we don't know whether the air (since 1989) would meet the new ambient air quality standards for particulate matter. Finally, there are no Mound data describing nonradioactive air quality before 1971, including 21 years when Mound Laboratory personnel disposed of solid and liquid wastes by open burning.
References
APPENDIX B: POLONIUM-210 RELEASES FROM THE MOUND LABORATORY
Polonium-210 in Air
The Monsanto Chemical Company brought polonium-210 research to the Mound Laboratory from the Dayton Project when the Miamisburg plant opened in 1948; work with radioactive materials ("hot-side" operations) began in 1949. From the beginning, Mound Laboratory scientists established an aggressive environmental monitoring program. However, we do not have all the environmental data today that they originally collected, and the quality of the data is not as high as the quality of environmental data generated today.
We have polonium air summary data for most months (1949 through March 1954), quarters (April 1954 through 1962), half-years (1963 into the early 1970s), and years (1972 through 1974). Mound Laboratory scientists stopped reporting concentrations of polonium-210 in the environment in 1975. They had stopped using it several years before and environmental levels had decreased, through radioactive decay, to three orders of magnitude below the Radioactivity Concentration Guide value recommended by the United States Energy Research and Development Administration, the immediate predecessor to DOE, at that time.
Although a few of the earlier reports are missing or are illegible, the air data we have are consistent. In many of the air samples, Mound Laboratory personnel detected no polonium. Among the samples where they did detect polonium, the maximum levels from different reporting periods and different locations range from 2.7 x 10-13 microcuries per milliliter (µCi/mL) to 6.56 x 10-11 µCi/mL. The highest level detected (6.56 x 10 -11 µCi/mL) is more than three times as high as the next highest level in the set of environmental reports we have.
The usefulness of the available data--especially data from the 1950s--is limited. Air samples collected before 1972 were not collected in one location around the clock as the air samples Mound scientists collect today at their permanent air monitoring stations. Therefore, we cannot be sure that the polonium-210 air data reported before 1972 reflect maximum, or even average, concentrations of polonium-210 that people might have breathed at these locations.
Nevertheless, ATSDR staff asked, do the available data show that there was a problem? We considered whether a person who breathed air containing the highest concentration of polonium-210 that we have data for would have experienced any adverse health effects. A 1958 quarterly health physics report indicates polonium-210 was measured at 6.56 x 10-11 microcuries per cubic centimeter (µCi/cc) in air at Fairhaven, Ohio; (this is equivalent to 6.56 x 10-11 µCi/mL) [1]. This was the maximum reading recorded during the third quarter of 1958 and the highest measurement we located in any of the environmental reports.
We note that the data do not permit us to estimate with any certainty what concentrations of polonium-210 people actually were exposed to. During the same quarter in which the highest polonium concentration in air was recorded, a second sample was collected at the same location one month later; the polonium-210 concentration in the second sample was 2 orders of magnitude lower than the first. If we simply average the two numbers, the resulting dose is half the higher number. But we don't know what the real long-term exposures were. It is very likely that exposures to polonium in air from the Mound Laboratory over the quarter, on average, were much lower than the highest reading because of non-continuous operations at the plant and variable wind patterns. On the other hand, we may not have measurements of higher concentrations in air that resulted in higher exposures--at this location or elsewhere.
When we consider the reported air concentrations, we must also acknowledge that there is uncertainty as to the minimum dose of polonium-210 necessary to cause adverse health effects. This is because polonium-210 is naturally occurring and is found throughout the human body. This makes it difficult to assign the cause of an adverse health outcome to exposures to environmental polonium. The human body normally incorporates polonium-210 from air, water, food, and especially tobacco smoke, and a person's body content of polonium will vary with diet and smoking habits [2]. We know from human studies where polonium-210 accumulates in the body once it is in the bloodstream, but our toxicity information comes from studies of mice and rats subjected to high doses of polonium-210, not from human evaluations.
Studies of uranium miners have shown that polonium-210 is distributed throughout many body tissues, but it tends to concentrate in the testes and kidney cortex. However, the distribution of polonium-210 in miners may result from primary exposure to and distribution of radioactive lead, which decays to polonium-210, and not primarily from the distribution of polonium-210 [3]. Other studies show that when ingested, polonium-210 aggregates in the gut wall but eventually appears predominantly in the red blood cells, sperm, and seminal fluid. Researchers studied the effects of polonium-210 on reproduction in mice; depletion of spermatocytes occurred at doses greater than 0.01 µCi per kilogram of body weight (0.01 µCi/kg) [4]. Bone cancers and lymphomas in mice occurred at higher doses (0.46 µCi/kg and 0.9 µCi/kg, respectively), and sarcomas, carcinomas of soft tissue, liver damage, and malignant renal tumors occurred in rats at even higher doses (6 µCi/kg) [4].
We used the results from the mice studies to evaluate polonium-210 exposures in humans. The lowest observed adverse effect level of polonium-210 that has been shown (in mice) to cause health problems is 0.01 µCi per kilogram of body weight [4]. A 30-kg child would have to breathe the highest-polonium air concentration (6.56 x 10-11 µCi/mL) continuously for around 300 days before receiving this much polonium radioactivity, and an adult male would have to breathe the air for more than a year before receiving this much radioactivity. Based on this information, we do not believe that people would have experienced adverse health effects from air exposures to polonium-210 released from the Mound Laboratory. However, based on the shortcomings of the air data collected before 1972, the data gaps before 1960, and the relative magnitude of polonium-210 operations and releases during the 1950s, we cannot conclude that there were no exposures at levels of health concern, either. Therefore, this exposure pathway is indeterminate.
Polonium-210 in Water
Mound Laboratory personnel monitored several locations in the Great Miami River for polonium-210 from very early in the plant's history. Nevertheless, as with air data, we have only limited data from the 1950s describing releases of liquid wastes containing polonium-210 and concentrations of polonium-210 in the Great Miami River. Reports before September 1951 indicate the number of samples that were collected from the river, but they do not provide the results of the sample analyses.
In the OU9 Site Scoping Report, Volume 7 - Waste Management document, Mound Plant staff reported liquid effluent radioactivities and waste sludge radioactivities (and liquid volumes of each) generated by the polonium-210 program [5]. These data cover September 1952 and October and November 1953 only; they show the highest levels of polonium-210 released to the Great Miami River among all the data available.
The highest river concentration of polonium-210 for which we have data (7.4 x 10-5 µCi/mL) was recorded on August 22, 1955, at the location where the effluents enter the Great Miami River.
To evaluate these data, we estimated the dose for a person who swam in the river at the Chautauqua Dam recreation facility and swallowed 100 milliliters of river water. (We know that it is unlikely that people would swim in the Great Miami River in October or November, but we are evaluating the data as though the same releases or measured concentrations could have occurred at any time.)
We chose the Chautauqua Dam area of the river because a recreational facility that includes a swimming beach is there. We estimated the concentration of polonium-210 in the river at the Chautauqua Dam for the polonium-210 release data by first calculating the average concentration of polonium-210 released to the river in each of the three months, and then reducing these concentrations by an amount that would be expected from dilution in the river. For the river concentration data, we took the highest level of polonium-210 measured in the river (at the effluent outfall) and diluted it to a concentration we would expect at the Chautauqua Dam.
We estimated a dilution factor in the river by averaging the concentrations of polonium-210 measured at the Chautauqua Dam during the period from the middle of 1960 through the end of 1969. We compared this average to the average polonium-210 concentration measured in Mound Laboratory liquid effluents during the same period. The ratio of the two averages, 0.017, is an approximate dilution factor.
Although the effluent data are presented as polonium radioactivities in waste water and in sludge separately, we assumed people would be exposed to polonium-210 from both waste water and sludge effluents. We don't actually know how the sludge behaved in the river- whether it entered the river continuously, whether the polonium in sludge would dissolve or become suspended in the river water, and whether it would travel downstream at the same rate as the polonium released in waste water. And we don't actually know the concentrations of polonium-210 in the effluents released. Therefore, we assumed the total volumes and polonium radioactivities in both waste water and sludge were released continuously, together, throughout each month.
TABLE I. GREAT MIAMI RIVER CONCENTRATIONS AND DOSES FROM POLONIUM-210 IN MOUND LABORATORY EFFLUENT.
| Month | Polonium-210 concentration in water + sludge, in effluent (µCi/mL).* | Polonium-210 concentration in water, at Chautauqua Dam (µCi/mL).** | Polonium-210 radioactivity ingested in 100 mL river water (µCi). | Radiation dose to an adult from ingesting 100 mL river water (mrem). |
| SEP 1952 | 8.96E-04 | 1.52E-05 | 0.0015 | 2.90 |
| OCT 1953 | 4.29E-04 | 7.29E-06 | 0.0007 | 1.39 |
| NOV 1953 | 3.10E-04 | 5.27E-06 | 0.0005 | 1.00 |
| * Calculated from data in the Mound Plant OU9 Site Scoping Report, Waste Management Report [5]. ** Calculated as previous column times 0.017. | ||||
The maximum effluent concentrations of polonium-210 we calculated in waste water and sludge together are higher than the reported highest concentrations of polonium-210 measured in the Great Miami River for these months. We have data for two of the three months; October 1953 river data are illegible in the report. Reported maximum concentrations in the river at the effluent outfall are 2.0 x 10-7 µCi/mL in September 1952 and 3.3 x 10-7 µCi/mL in November 1953. If we consider only the water portion of the effluent data (not the sludge), the calculated concentrations of polonium-210 in effluent are still greater than the maximum measured concentrations at the outfall. The concentrations measured in the river and those we calculated from the effluent release data may be different because the polonium-210 in sludge may not be dissolved in the river water, or the river was sampled at a time when the concentration of polonium-210 in the effluent was below average for the month, or there was some dilution by the river at the river sampling location.
The greatest amount of polonium-210 was released to the Great Miami River in September 1952, and the highest radiation doses would result from ingesting river water during this month (or any month with an equivalent release). Table I shows how much radioactivity and radiation dose a person would receive from ingesting 100 mL of water. During September 1952, a person swallowing 100 mL of water would ingest 0.0015 µCi of polonium-210. For an infant (10 kg), this quantity is more than 50 times smaller than our lowest observed adverse health effect level of 0.01 µCi/kg; for an adult (70 kg), it is more than 450 times smaller. The radiation dose (2.90 millirems [mrem]) from this amount of radioactivity is also very small. This dose does not represent a health hazard.
The available data show the maximum measured concentration of polonium-210 in the Great Miami River is 7.4 x 10-5 µCi/mL. The diluted concentration of this quantity at the Chautauqua Dam is about 1.2 x 10-6 µCi/mL. The dose would be about 0.23 mrem. This radiation dose is not a health hazard.
These calculations were meant to investigate whether people exposed at the most likely location in the Great Miami River to polonium-210 released to the river would have experienced adverse health effects. Our results show they would not. However, we acknowledge that a person could have swallowed more than 100 mL of contaminated water from the river, or the concentrations in the effluents could have been higher than we calculated, or someone could have ingested water closer to the effluent outfall where the concentrations were higher. (In our calculations, ingestion of 100 mL of effluent water at the outfall would have been a health hazard, but we don't think anyone would drink this water.) Regardless of our calculations, it is possible that more polonium-210 was released to the river than the available data indicate. We conclude, therefore, that although the data do not show that polonium-210 released to the area waterways ever posed a public health hazard, the data are incomplete. Therefore, this pathway is indeterminate.
References
APPENDIX C: HISTORIC RELEASES OF PLUTONIUM-238, HYDROGEN-3 (TRITIUM), AND OTHER RADIONUCLIDES TO THE ENVIRONMENT
Plutonium-238 and Hydrogen-3 (Tritium) in Air
Plutonium-238 was first incorporated in an RTG (radioisotopic thermonuclear generator) in 1961 at Mound for use in the SNAP (Satellite Nuclear Auxiliary Power) program; however, research and development for this program began earlier [1, 2]. Studies of hydrogen-3 (tritium) began at the Mound Laboratory in 1954 [1].
During the 1960s, the Mound Laboratory released the largest quantities of both plutonium-238 and tritium to the environment in the plant's history.
In 1960, the Mound Laboratory released more than 250 millicuries of plutonium-238 to the atmosphere [2]. This quantity is more than 16,000 times the quantity released to the air in 1994 [3]. In only one other year, 1967, did the air releases of plutonium-238 exceed even 20% of the quantity released in 1960. By 1972, total plutonium-238 air releases were about 0.1% of the quantity released in 1967, and they have been much lower than that in the years since 1972 [1, 2].
The earliest available data that describe air releases of tritium are for 1959 [1, 2]. Throughout the 1960s, the Mound Laboratory released to the air tritium that exceeded 100,000 curies in every year; in 3 of those years, tritium releases exceeded 300,000 curies. The peak year for tritium air releases was 1967, when Mound operators released 364,685 curies [2]. By 1972, total tritium air releases were about 8% of the quantity released in 1967. With one minor exception, quantities of tritium released to air have decreased since the early 1970s. In November 1989, there was an accidental release of 38,268 curies of tritium to the atmosphere through the stack of the SW building [4].
We used a simple air transport and dispersion model, CAP88-PC, to evaluate the plutonium-238 and tritium air releases [5, 6]. CAP88-PC (or the mainframe version, CAP88) is the computer code used for assessing regulatory compliance with NESHAPs (the National Emission Standards for Hazardous Air Pollutants). It incorporates a number of adjustable parameters, such as identity and quantity of radionuclides in air emissions, stack height, exit velocity, average meteorological conditions, and fraction of food products produced locally. The program calculates radiation doses to people in the pathway of the stacks emissions. It computes effective doses for inhalation; ingestion of produce, leafy vegetables, milk, and meat; air submersion; and ground shine (radiation from radionuclides deposited on the ground surface). For tritium, CAP88 also computes dose components from skin absorption and drinking water. CAP88 uses dose coefficients based on the ICRP-26 and ICRP-30 dosimetry model; it uses a specific activity model for tritium dose estimates [7, 8, 9].
We obtained annual summaries of on-site meteorological data for 1989 through 1994 from Mound Plant senior scientists. We secured other information, such as stacks locations and heights, diameters, and exit velocities, and information about how Mound Plant scientists run their program for NESHAPs compliance analyses from Mound's 1994 annual environmental monitoring report or from Mound senior scientists [3]. Using input from Mound's 1994 report, we were able to reproduce their results for 1994 to within a few percentage points. We then used the computer model to calculate effective doses for air emissions of plutonium-238 and tritium for 1960, 1967, and 1989. We chose 1960 and 1967 because these were the years when plutonium-238 and tritium releases were highest, respectively. Also; 1967 was the year of the second-highest plutonium-238 releases. We chose 1989 because it was the only recent year in which high releases of either radionuclide occurred.
TABLE I. ANNUAL EFFECTIVE DOSES DUE TO PLUTONIUM-238 AND HYDROGEN-3 (TRITIUM) AIR RELEASES FROM THE MOUND FACILITY, CALCULATED USING CAP88-PC.
| Year | Releases | Direction | Distance | Total Dose | Percent of Dose | ||
| Pu-238 | H-3 | Pu-238 | H-3 | ||||
| units | curies | curies | NSEW | meters | millirems | % | % |
| 1960 | 2.50 E-1 | 102,427 | NE | 825 - 1,150 | 19 | 55 | 45 |
| 1967 | 5.43 E-2 | 364,685 | NE | 975 | 36 | 6 | 94 |
| 1989 | 4.00 E-6 | 41,534 | NNE | 825 - 1,050 | 65 | 0.00 | 100 |
In Table I, direction and distance represents the direction and distance from the release point on the site to the location with the highest dose estimate. The doses calculated are the total annual effective doses from exposures to plutonium-238 and tritium air releases. Percent of dose is the approximate portion of the total dose attributable to either plutonium-238 or tritium for that year's annual releases.
In 1989, the total dose is higher than in the other years even though the total quantity of both plutonium-238 and hydrogen-3 released to the air in that year was lower than in the other years. For the years 1960 and 1967, we assumed the releases of radionuclides occurred at a constant rate throughout the year. For 1989, we know the accidental release of tritium in November of that year--accounting for 92% of the total tritium released for the year--occurred in one day. Because the dose a person gets depends on the concentrations of radionuclides in the air, and the concentrations depend upon the duration over which the radionuclides are released, a person directly in the pathway of the tritium release in 1989 would have breathed a sufficiently higher concentration of tritium to receive a larger radiation dose than someone in the pathway of the air releases in either of the other years. Nevertheless, this dose (65 mrem) is not a public health hazard. Based on these dose estimates and the evidence we present below, we have concluded that plutonium and tritium air releases from the Mound facility have never posed a health hazard.
We acknowledge that the CAP88 dispersion model does not account for unusual terrain, unusual weather, and inconsistencies in the dispersion of particulates from the Mound stacks. We don't know whether the releases during the year were frequent or consistent in magnitude. Also, we inserted the 1994 stacks configuration and meteorological conditions from the Mound Plant into the model to represent conditions in 1960 and 1967; (we used 1989 meteorological data to model 1989 doses). These assumptions may not be entirely valid, but we think these doses are useful as an estimate of the general magnitude of doses a person would receive from airborne releases for these years.
We also know that sources other than the stacks may have contributed to off-site air contamination. We expect that these types of releases (for example, resuspension of contaminated dirt during excavation on site) would be close to the ground and that particulates from these releases would not travel as far as those from the stacks releases. For example, in 1994, the SM (Special Metallurgical) Building was torn down. The SM Building was near Mound Road across from the golf course and was in the area where Mound employees conducted plutonium operations. We expect that some dust and dirt will be disturbed during the tearing down of buildings; we note that the highest level of plutonium-238 recorded at an air monitoring station in 1994 occurred at the station nearest the SM Building [3].
Although we recognize that the CAP88 dispersion model may not provide us with precise dose estimates, we have additional evidence that the air releases of plutonium-238 and tritium never posed a health hazard.
Unlike the polonium air data, our data set of plutonium-238 and tritium releases to the environment and plutonium-238 and tritium air monitoring results is uninterrupted. The plutonium-238 air sampling data before 1972 are limited in the way that we described for polonium-210 air data (i.e., the air samples were not collected continuously; see Appendix B). Also, we do not have data for tritium releases to air from 1954 through 1958. Nevertheless, these data limitations do not appear to be significant. Tritium releases in 1959 and 1960, for example, were considerably lower than tritium releases for the remainder of the 1960s. Mound environmental reports state tritium was not detected at monitoring sites before 1967. This information suggests we have air measurements during the years when plutonium-238 and tritium concentrations were highest in air, and none of the data indicate these radionuclides were ever at levels of health concern.
Neither the metal nor the dioxide forms of plutonium (two chemical forms used at Mound) are particularly soluble in water. Plutonium binds tightly to soil and will remain in place in soil for many years. Therefore, the soil presents us with a cumulative record of plutonium releases from Mound [1, 10]. The soil does not typically bind tritium very well, however, and soil does not serve as a cumulative record of tritium releases(1). With the exception of plutonium-238 contamination in the Miami-Erie Canal, which resulted from a pipeline break and ground spill, the soil data do not show any plutonium-238 anomalies near the plant. We might expect such anomalies if large air releases escaped the detection of the air-sampling efforts. What the regional soils data show is that plutonium-238 concentrations decrease as distance from the Mound Plant increases [11]. This information at least tells us the most likely areas where air releases would have had the greatest impact: areas close to the plant. Department of Energy, Ohio Environmental Protection Agency, and ATSDR and the National Air and Radiation Environmental Laboratory soil samples taken near the Mound Plant do not show that plutonium-238 is a health problem today, and so plutonium-238 was not likely a health hazard in the past.
We conclude that the plutonium-238 and hydrogen-3 air releases from the Mound facility were never a public health hazard and that we have sufficient available data to make this conclusion.
Plutonium-238 in Water
In 1960, plutonium solid and liquid wastes were handled as "packaged waste" and were shipped off site for disposal. Mound's environmental reports issued until 1965 state that there were no direct discharges of plutonium into the waterways [12]. In 1965, Mound scientists began reporting plutonium-238 concentrations in the Mound drainage ditch, which flows from the site into the Miami-Erie Canal and from there into the Great Miami River. In 1967, Mound scientists began reporting plutonium concentrations in the Great Miami River at the same locations where they were reporting polonium-210 concentrations.
Although we do not have data on plutonium-238 concentrations in the Great Miami River before 1967, we have data for plutonium-238 in the Mound drainage ditch dating from 1965 [13]. The highest concentration of plutonium-238 reported in the Mound drainage ditch was in 1967. The highest reported releases of plutonium-238 in water to the environment were for the years 1968 and 1969 [2]. Therefore, it appears that we have data on plutonium-238 concentrations in the river for the years when releases were the highest. If we consider that someone could swallow water from the Great Miami River while swimming at the Chautauqua Dam recreational facility, and we assume this person swallowed the highest concentration of plutonium-238 measured at this location, the radiation dose the person would have received is much less than 1 millirem (mrem). This amount of plutonium-238 does not pose a health hazard.
In 1971, Mound scientists reported hydrogen-3 and plutonium-238 concentrations in Miamisburg municipal drinking water. They continued, in subsequent years, to report tritium concentrations in Miamisburg water, but they didn't report plutonium in city water in their annual environmental reports again for another 4 years. When they started again (1975), they also began reporting plutonium-238 in the private wells in and near Bud's Trailer Park. Among all the municipal and private wells data, the highest concentration of plutonium-238 reported, 0.491 picocuries per liter (pCi/L), was in Miamisburg's water in 1971 [14]. (This sample was taken from a resident's tap, not a municipal well.) However, even if people had used only this water for drinking, cooking, and bathing, they would have received an annual radiation dose from the plutonium of less than 1 mrem. This amount of plutonium-238 does not pose a health hazard.
We also considered whether plutonium-238 in Miamisburg's municipal water would have been a health hazard during 1967, when releases of plutonium-238 in water from the Mound facility were highest. Plutonium-238 releases in water in 1967 were about 16 times higher than those in 1971. We estimated that a person using Miamisburg's water for all purposes in 1967 would have received, at the most, no more than approximately 6 mrem. This dose includes contributions from plutonium-238, polonium-210, and hydrogen-3. This amount of radiation does not pose a health hazard.
We conclude, therefore, that plutonium-238 in the area waterways has never been a public health hazard.
Other Radionuclides
Mound scientists began studying a large variety of radioisotopes besides polonium-210, plutonium-238, and hydrogen-3 during the 1950s. These radioisotopes included actinium-227, radium-226, thorium-230, and protactinium-231 [2]. Many of these radioisotopes were used in smaller quantities (laboratory scale) than polonium-210, plutonium-238, and hydrogen-3. Wastes generated from these Mound programs were recycled or contained for off-site shipment, and there are fewer environmental data available for them than for polonium-210, plutonium-238, and hydrogen-3. Many of these radioisotopes were (and are) quite valuable and in some cases, recovery of these isotopes for resale was the purpose of the program. Neither the records of releases and spills nor the more recent characterization of the off-site soils and water indicate that these radioisotopes were ever a public health hazard [4, 11, 15, 16, 17].
Mound officials began publishing the concentrations of plutonium-239 in on-site and off-site air samples with the 1975 annual environmental data and concentrations of uranium-233, -234, and 238 in surface water with 1978 data. They later expanded monitoring programs for each of these radionuclides. The data for plutonium-239 and the uranium isotopes indicate that the levels of these radionuclides in the environment have always been very low and that they have never been a public health hazard.
References
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