PUBLIC HEALTH ASSESSMENT
US DOE MOUND FACILITY
[a/k/a MOUND PLANT (USDOE)]
MIAMISBURG, MONTGOMERY COUNTY, OHIO
APPENDIX E: ATSDR AND NAREL ENVIRONMENTAL SAMPLING IN THE VICINITY OF THE MOUND PLANT (1994)
Background
In 1992, the U.S. Environmental Protection Agency's (EPA) National Air and Radiation Environmental Laboratory (NAREL) entered into an interagency agreement with the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct environmental sampling and analyses for radionuclides at Department of Energy sites. In December 1993, NAREL and ATSDR staff began their environmental sampling program in Miamisburg. They visited Miamisburg to arrange for the placement of the air monitors, to survey the area with radiation equipment to establish sampling locations, and to sample the soil, water, air, and vegetation. They collected final groundwater and vegetable samples in November 1994 and removed the air monitors from city and private properties in January 1995.
In December 1994, ATSDR staff issued letters to the residents whose groundwater was sampled to provide each of them with the results from their well water collected in June and July 1994 [1]. None of the groundwater samples contained radionuclides at levels of health concern. In February 1996, following a Mound Plant public meeting where we received requests for the results from our environmental sampling, we gave interested stakeholders the data from all environmental media without comment [2]. Upon request, we sent a letter briefly summarizing the data to the Miamisburg city manager in March 1996 [3]. None of the results indicates that radioactive materials in the environment around the Mound Plant pose a public health hazard.
This appendix presents a complete evaluation, including dose estimates, of the environmental data that ATSDR and NAREL personnel made available in February 1996.
The discussions are organized, as the data are organized, into eight groups: air particulates, air tritium, groundwater, surface water, soil, sediment, locally grown produce (mainly vegetables), and vegetation (mainly grasses and weeds). Each media group is evaluated under the following headings: exposure pathways and dosimetry considerations; gross alpha and beta results; gamma spectrometry results; and analyses of hydrogen-3 (tritium), plutonium, thorium, and uranium. At the end of the individual media evaluations, we present a summary of internal radiation doses a person could receive from exposures to all the environmental media (from all the pathways) combined.
The radiation doses in this appendix represent internal radiation doses that a person could get if she or he breathed the air; or drank the water; or ate the soil, sediment, locally grown produce, or vegetation containing the radionuclides, we measured. In most cases, if not all, we have assumed a very high exposure situation to estimate a "worst-case" or upper limit on the radiation dose that a person might receive. In most cases, we have assumed a 1-year exposure and a 50-year committed effective dose. This means the dose includes the effects of radiation from the portion of the radionuclides that were inhaled or ingested--and their subsequent decay products--that remain in the body up to 50 years. The term "committed" refers to the 50-years of radiation exposure inside the body, and the term "effective" means the absorbed radiation is weighted for the radiation type (alpha, beta, gamma) and for the biological effects of the radiation on different body organs. The term committed effective dose is properly used for radiological protection; it provides a basis for estimating the probability of developing cancer from exposures to very low levels of radiation [4]. We have calculated the doses in this appendix for comparison purposes; none of the doses we calculated are known to cause any adverse health effects.
In addition to the potential internal exposures to the radionuclides we measured, people will be exposed externally to radiation from outer space (cosmic radiation) and to gamma radiation from naturally occurring gamma-emitting radionuclides in the environment. The average annual cosmic radiation dose to people in the United States is about 26 mrem at sea level; this value doubles with each 2,000 meters increase in altitude [5]. The main contributors to terrestrial gamma radiation are potassium-40 and the decay products from the thorium and uranium decay series that are naturally present in the soil. Most of the terrestrial gamma radiation comes from the top few inches of soil [5]. Concentrations of gamma-emitting radionuclides naturally present in soil vary among different soil types and in different areas of the country; the annual effective dose to a person ranges from about 20 mrem to 70 mrem [5].
During our field survey of properties around the Mound Plant, we measured gamma radiation to help us identify sample locations. Most of the readings, including those we measured in the Miami-Erie Canal and at the background locations, were in the range of 8 to 14 microroentgens per hour (µR/h). Near the seeps at the railroad cut (on the Main Hill) the readings were 15 to 16 µR/h, and near the picnic area in the Community Park they were 24 µR/h. All of these readings are consistent with gamma radiation levels we expect from cosmic radiation plus naturally-occurring levels of gamma-emitting radionuclides in soils. (However, we suspect from the laboratory analysis that the Community Park samples include remnants of coal ash deposited on the grounds when the property was the site of the Miamisburg power plant. See the discussion in Section 5, this appendix, on soils analyses.) These measurements indicate that a person living in Miamisburg will receive about 60 to 70 mrem per year from external gamma radiation.
For a reference dose that is protective of the public health (i.e., a dose that will not result in adverse health effects), all the radiation dose estimates included in this appendix may be compared to a standard the International Commission on Radiological Protection (ICRP) recommends. The ICRP recommends that people in the general public (as distinguished from people who work with radioactive materials) do not receive more than 100 millirem (100 mrem) per year radiation dose from sources other than medical and those occurring naturally in the environment [4]. (The Committee on the Biological Effects of Ionizing Radiation estimates that people in the United States receive a total average radiation dose of approximately 300 mrem per year from naturally occurring sources [6].) Additionally, the ICRP considers that whole body radiation doses (which describe many environmental exposures) at levels higher than 100 mrem per year acceptable for short durations, provided that the average dose over 5 years does not exceed 100 mrem per year. None of the radiation doses we calculated for the samples we collected in any environmental medium exceeded 100 mrem per year.
In addition to ICRP recommendations, we have included with the groundwater and surface water data evaluations references to EPA-proposed Safe Drinking Water standards [7]. These standards technically apply to public drinking water supplies, but they are useful for comparison. Safe drinking water standards for radionuclides are concentrations based on radiation dose limits of 4 mrem per year for beta- and gamma-emitting radionuclides and on additional criteria for alpha emitters, such as plutonium, thorium, and uranium. Allowable doses from alpha emitters in drinking water under the Safe Drinking Water Act may exceed 4 mrem per year; however, none of the concentrations of alpha emitters we measured in groundwater or surface water near the Mound Plant would result in doses that exceed 4 mrem per year.
Finally, we offer the following comments on the data tables we distributed in February 1996. Some of the tables include negative numbers. A negative number means the result is essentially zero. Negative numbers result from normal electronic fluctuations in the radiation-counting equipment and fluctuations in background radiation. Because the equipment is very sensitive, it will sometimes produce a "reading" when there is no sample in the counting chamber. Therefore, the counting procedure includes taking an equipment "background" measurement, which a computer later subtracts from the sample measurements. When a sample measurement is zero or very small, i.e., near the detection limit of the equipment, subtracting out equipment background can result in a negative number. These results are sometimes reported as "not detected" (ND) or as zero. We also reported some measurements in our data where the error term is as large as or larger than the reported measurement. This result can also occur when the sample measurement is near or below the minimum detection level. Large error terms also mean the measurements are essentially zero.
Data Evaluation
1. AIR PARTICULATE SAMPLES
DOSIMETRY:
The two major pathways for exposure to particulates in the air are inhalation and submersion. We did not consider deposition on crops and produce in this section because we conducted separate studies of those media; (results from those studies are presented elsewhere in this appendix).
The ICRP 23 breathing rate for an adult is 22,000 liters per day [8]. Dose conversion factors for a 50-year committed effective dose are from ICRP 68 [9]. Submersion doses were estimated and found to be very small compared to the inhalation doses; therefore, they are not included in this evaluation.
The doses calculated are the maximum concentrations for a person who would be exposed to each radionuclide for a full year. We made no corrections for background concentrations.
GROSS ALPHA/BETA:
June-September 1994: There are no elevated levels of radioactivity in any of the samples. The highest gross alpha values are similar to the gross alpha value from the September-December 1994 background site. Gross beta values are the same as those for the background site.
September-December 1994: There are no elevated levels of radioactivity in these samples. All values are similar to values for the background site.
GAMMA SPECTROSCOPY:
June-September 1994: Other than Be-7, a naturally occurring radionuclide, there was no detectable activity in any of the samples.
September-December 1994: Other than Be-7, a naturally occurring radionuclide, there was no detectable activity in any of the samples.
TRITIUM:
We did not analyze tritium in air particulate samples. We measured tritium in water vapor samples that we collected separately on three occasions.
PLUTONIUM ALPHA SPECTROSCOPY:
June-September 1994: Two samples had very low positive values for Pu-238. The highest, 6.4 x 10-5 picocuries per cubic meter (pCi/m3), collected on Shephard Road, represents a dose of 0.08 mrem. The Pu-238 in these samples does not pose a public health hazard.
September-December 1994: One sample had a very low positive value for Pu-239: 7.6 x 10-5 pCi/m3. This sample, also collected on Shephard Road, represents a dose of 0.11 mrem. The Pu-238 in this sample does not pose a public health hazard.
THORIUM ALPHA SPECTROSCOPY:
June-September 1994: There were some positive values for Th-227, but the associated error terms are large and indicate that the results could be interpreted as nondetectable. Th-227 is a naturally-occurring radionuclide in the uranium-235 decay chain. Th-230 was present in all samples. This nuclide is in the uranium-238 decay series and is naturally occurring. The highest value for Th-230 was at the background site.
September-December 1994: We found one positive value for Th-227; this measurement also had a large error term and can be considered nondetectable. The values for Th-230 were similar to the June-September 1994 background site values except for the result for the Mound State Memorial Park site: it was 2.8 x 10-4 pCi/m3, or 5 times background. This represents a dose of 0.33 mrem (50-year committed effective dose) to an individual breathing the air for one year. In one sample from Harmon Field, we detected Th-232 at a level that represents a dose of 0.08 mrem to an individual breathing the air.
The thorium detected in these samples does not pose a public health hazard.
URANIUM ALPHA SPECTROSCOPY:
June-September 1994: Both U-234 and U-238 were detected on all of the air filters. The U-234 activities are similar to the background values for both time periods. The highest U-238 activity, 1.2 x 10-4 pCi/m3, collected near the water slide, is twice background. It represents a dose of 0.03 mrem.
September-December 1994: Both U-234 and U-238 were detected on all of the air filters. The U-234 activities, except for the sample from the waste treatment plant, are similar to the background values for both time periods. The waste treatment plant sample was 5.1 x 10-4 pCi/m3, which represents a dose of 0.13 mrem. The highest U-238 activity, 2.2 x 10-4 pCi/m3, also collected at the waste treatment plant, is 3 times background for this period. It represents a dose of 0.05 mrem.
All of the uranium values are small and have high associated error terms. The consistency of the data for all of the samples indicates that these results represent naturally occurring uranium rather than material released from the Mound Plant. Both the water slide and waste treatment plant samplers were near areas where a lot of dust could be generated. The uranium in these samples does not pose a public health hazard.
2. TRITIUM IN AIR SAMPLES
DOSIMETRY:
The primary exposure pathway for tritiated water vapor is inhalation. We evaluated tritium in garden vegetables and water supplies separately by sampling those media; we evaluate the data from those samples elsewhere in this appendix.
The breathing rate for standard man, 0.9 cubic meters per hour (m3/hr), comes from ICRP 23 [8]. The dose conversion factor for a 50-year committed effective dose is from ICRP 68 [9].
The annual doses calculated are for the maximum concentrations detected. We did not correct for background concentrations in air.
GROSS ALPHA/BETA: These samples were collected only to measure tritium in air; air particulate filters were analyzed for gross alpha and gross beta radioactivity.
GAMMA SPECTROSCOPY: These samples were collected only to measure tritium in air; air particulate filters were scanned for gamma radiation.
TRITIUM:
July 1994: Positive values were found at the water slide, Harmon Field, and Mound State Memorial Park sampling sites. The highest value was 664 picocuries per liter (pCi/L) of water vapor in air, or 9.4 pCi/m3 of air at Mound State Memorial Park. This level of activity represents a dose of 0.01 mrem per year.
November 1994: Positive values were found at the water slide and Harmon Field sites. The highest value was 631 pCi/L of water vapor, or 6.61 pCi/m3 of air, at Harmon Field. This concentration represents a dose of less than 0.01 mrem per year.
January 1995: No positive values were found at any of the sites.
The positive values found in the three surveys did not correlate as well with wind direction as expected. Although there was some correlation some of the time with wind direction, positive values occurred when the wind was not blowing from the facility toward the sampling site, and no detectable tritium appeared at some sites when the wind was blowing toward the sampling site. Positive values at the water slide site could be the result of aeration of the well water used; water from the Community Park well, which feeds the water slide, had 1,600 pCi/L tritium in the July sample.
None of the tritium levels that we measured in water vapor poses a public health hazard.
PLUTONIUM ALPHA SPECTROSCOPY: These samples were collected only to measure tritium in air; plutonium was measured in the air particulate samples.
THORIUM ALPHA SPECTROSCOPY: These samples were collected only to measure tritium in air; thorium was measured in the air particulate samples.
URANIUM ALPHA SPECTROSCOPY: These samples were collected only to measure tritium in air; uranium was measured in the air particulate samples.
3. GROUNDWATER SAMPLES
DOSIMETRY:
Potential pathways for human exposures to radionuclides in groundwater include direct ingestion of the groundwater, eating meat from animals that have consumed the water, eating crops (produce) irrigated with the water, and consuming animals that have eaten irrigated crops. Based on our knowledge of the use of groundwater around the Mound Plant, we conclude that direct ingestion of the groundwater would give the greatest radiation dose.
The value for ingestion of water by an adult given in EPA 600 (Exposure Factors Handbook) is 1.4 liters of water per day [10]. We took dose conversion factors for a 50-year committed effective dose from ICRP 68 [9]. We assumed that maximally exposed individuals would obtain all of their drinking water from the groundwater source with the maximum concentration of each radionuclide detected across all the groundwater samples. We did not correct for background concentrations in groundwater.
GROSS ALPHA/BETA:
July 1994: We detected only marginally positive activity in these samples. There were no results that would indicate the presence of radionuclides other than the ones identified below.
November 1994: We detected only marginally positive alpha activity in these samples. There were no results that would indicate the presence of radionuclides other than the ones identified below. One gross beta sample had 12 pCi/L. The sample from July did not show this level of activity.
GAMMA SPECTROSCOPY:
July 1994: We did not find any radionuclides of significance in any of the groundwater samples. The Pb-214 recorded for the Community Park sample may not be real. The measurement is likely the result of fluctuations in the background in our Counting Room; it is not supported by positive results for Ra-226 or Bi-214.
November 1994: We did not find any radionuclides of significance in any of the groundwater samples.
TRITIUM:
July 1994: The maximum concentration of tritium that we found was in the Community Park well: 1,600 pCi/L. This value represents a dose of 0.05 mrem to an individual. The proposed EPA guideline for tritium in drinking water is 60,900 pCi/L.
November 1994: The maximum concentration of tritium that we found was in the Community Park well: 670 pCi/L. This value represents a dose of 0.02 mrem to an individual drinking this water.
The tritium levels we measured in these samples do not pose a health hazard to people who drink this water.
PLUTONIUM ALPHA SPECTROSCOPY:
July 1994: We detected low levels of Pu-238 in three samples. The highest value, from the Community Park well, was 0.073 pCi/L. Although this well supplies water to the Community Park swimming pool, we did not detect Pu-238 activity in the pool. The proposed EPA guideline for Pu-238 in drinking water is 7.0 pCi/L. The maximum concentration detected represents a dose of 0.03 mrem to an individual drinking this water.
We detected Pu-239 in three samples: one from the swimming pool, one from the Benner Road site, and one from the city drinking water supply collected at a residence on Mound Avenue. The maximum concentration, 0.24 pCi/L from the Mound Avenue sample, represents a dose of 0.11 mrem to an individual. We reanalyzed the Mound Avenue sample to confirm the presence of Pu-239; the analysis verified its presence. The November sample from this site did not have any detectable Pu-239. The EPA guideline for Pu-239 in drinking water is 62 pCi/L.
The Pu-238 and Pu-239 that we detected in these samples do not pose a health hazard to anyone who might drink this water.
November 1994: One sample had positive Pu-238; however, a review of the raw data suggests that this result is highly questionable. If the Pu-238 that we measured in this sample is real, it does not pose a health hazard to anyone who might drink this water. The July sample from this site had no detectable activity.
THORIUM ALPHA SPECTROSCOPY:
TABLE I. GROUNDWATER THORIUM DOSIMETRY.
| Nuclide | Maximum Value | Proposed EPA Guideline (pCi/L) |
|||
| July | November | ||||
| (pCi/L) | (mrem) | (pCi/L) | (mrem) | ||
| Th-227 | 0.068 | 0.00 | 0.59 | 0.01 | 400 |
| Th-228 | -- | -- | -- | -- | 125 |
| Th-230 | 0.86 | 0.34 | 0.77 | 0.31 | 79 |
| Th-232 | 0.040 | 0.02 | 0.13 | 0.05 | 88 |
July 1994: We detected Th-227 in one sample and positive Th-232 in two samples; no samples were positive for Th-228. All of the samples had positive Th-230. Table I below contains the doses we calculated.
November 1994: We detected Th-227 in four samples, Th-232 in two samples, and Th-228 in no samples. All of the samples but one were positive for Th-230. Table I below contains the doses we calculated.
None of the positive results pose a health hazard to persons drinking this water.
URANIUM ALPHA SPECTROSCOPY:
July 1994: We found positive results for U-234 and U-238 in all samples, including the sample from the background location. The highest value, 1.2 pCi/L U-234 from a well on Farmington Road, is significantly below the proposed EPA guideline of 30 pCi/L. It represents a dose of 0.11 mrem to an individual. The 0.92 pCi/L of U-238 represents a dose of 0.08 mrem per year to an individual.
November 1994: We found positive results for U-234 and U-238 in all samples, including the sample from the background location. The highest value, 1.2 pCi/L U-234 from a well on Farmington Road, is significantly below the proposed EPA guideline of 30 pCi/L. It represents a dose of 0.11 mrem to an individual.
The U-234 and U-238 levels we detected in these samples do not pose a health hazard to people who drink this water.
4. SURFACE WATER SAMPLES
DOSIMETRY:
Potential pathways for human exposures from radionuclides in surface water include direct consumption of the water, eating the meat of animals that consume the water, eating crops (produce) irrigated with the water, and consuming fish from the water. Based on the limited use of surface water around the Mound Plant, we have concluded that direct consumption of the surface water and consumption of fish are the major exposure pathways for surface water near the Mound Plant.
The value for consumption of water by an adult given in EPA 600 is 1.4 liters of water per day [10]. We assumed that individuals would obtain 10% of their drinking water from the surface water. This assumption will probably overestimate the impact to the public, but it should provide an upper limit on the radiation dose that people actually receive. Dose conversion factors for a 50-year committed effective dose are from ICRP 68 [9].
We estimated doses separately for the dissolved and the undissolved radionuclides detected in the surface water samples. We calculated the doses using the highest f1 values (fractional uptake values) for each radionuclide we detected. Fractional uptake values are the fraction of a radionuclide ingested that crosses the gut and enters the bloodstream. These values differ depending on the form--i.e., the chemical compound--of the radionuclide, although many other factors, such as ingestion of food, affect the amount of a substance that crosses the gut. For undissolved radionuclides, fractional uptake values are generally small. By using the highest fractional uptake value, we maximize the possible radiation dose that would result from ingesting the water.
The doses we calculated are for the maximum concentrations detected. See Table II for the maximum surface water concentrations and their associated doses.
Our fish consumption dose calculations are at the end of this section.
GROSS ALPHA/BETA:
July 1994: We detected elevated alpha activity in the filtrate (liquid portion) of one sample and some alpha activity in all the filtered particulate fractions. The highest particulate fractions (in samples from the South Canal and Overflow Creek) exceed EPA guidelines for gross alpha in drinking water, 20 pCi/L vs. 15 pCi/L, but the guidelines are for dissolved activity in public drinking water supplies.
We detected gross beta activity in the dissolved portion of 1 sample: 6.8 pCi/L from the sample collected in the Overflow Creek. This activity is well below the EPA guidelines of 50 pCi/L.
November 1994: We detected elevated alpha activity in the filtrate of five samples; all but three had alpha activity in the particulate fraction. The dissolved concentrations are below EPA guidelines, and the undissolved activity is not a health concern.
Five samples had elevated gross beta activity in the filtrate, and only two had activity in the particulate fraction. The dissolved activity does not exceed EPA guidelines, and the undissolved activity is not a health concern.
GAMMA SPECTROSCOPY:
July 1994: Gamma spectroscopy did not detect any radionuclides in any of the surface water samples.
November 1994: Gamma spectroscopy did not detect any radionuclides of significance in any of the surface water samples.
TRITIUM:
July 1994: The highest activity that we detected, 5,900 pCi/L, was in the National Pollutant Discharge Elimination System (NPDES) Outfall 001 sample. It is well below EPA guidelines.
November 1994: The highest activity that we detected, 4,510 pCi/L, was in the NPDES Outfall 002 sample. It is well below EPA guidelines.
None of the tritium levels that we detected pose a health hazard to anyone who might drink the surface water near the Mound Plant.
PLUTONIUM ALPHA SPECTROSCOPY:
July 1994: We detected Pu-238 in five samples of filtrate and six particulate fractions. The highest filtrate value was 3.6 pCi/L from a sample collected in the South Canal.
We detected Pu-239, 0.032 pCi/L, in the filtrate of 1 sample taken from the South Canal.
November 1994: We detected Pu-238 in seven samples of filtrate and seven particulate fractions. The highest filtrate value was 2.3 pCi/L in the sample from the Overflow Creek.
We detected Pu-239 in the filtrate for 3 samples; the highest level was 0.12 pCi/L in a sample from the South Canal.
None of the plutonium that we detected poses a health hazard to persons drinking from these surface water locations. Table II contains our calculated doses.
THORIUM ALPHA SPECTROSCOPY:
July 1994: We detected Th-227 in seven filtrate samples, Th-228 in one filtrate sample, Th-230 in all filtrate samples, and Th-232 in three filtrate samples. Except for Th-230 at 1.1 pCi/L in the NPDES 002 Outfall sample, we detected only traces of undissolved thorium.
November 1994: We detected Th-230 in eight samples and Th-232 in two samples. We detected only traces of undissolved thorium in these samples.
None of the thorium results pose a health hazard to persons drinking from these surface water locations. Table II contains our calculated doses.
URANIUM ALPHA SPECTROSCOPY:
July 1994: We detected U-234 and U-238 in both the filtrate and particulate fractions of all samples, including the background sample. The highest filtrate value, 0.93 pCi/L U-234, from the sample we collected in the Outfall 002 effluent, is significantly below the proposed EPA guideline of 30 pCi/L.
November 1994: The highest filtrate activity was 1.6 pCi/L U-234, found in the sample we collected from the NPDES Outfall 001 effluent. The maximum U-234 and U-238 activities found in the undissolved fractions of the samples were 0.32 and 0.13 pCi/L, respectively.
None of the uranium levels we detected pose a health hazard to persons who drink the surface water.
FISH CONSUMPTION:
We did not collect fish in our environmental survey. We estimated radiation doses to people who eat fish from the area waterways near the Mound Plant by considering how much fish people eat and how much of the radionuclides in the surface water might accumulate inside the fish. For each radionuclide that we measured, we added together the highest concentration in the dissolved portions of samples and the highest concentration in the undissolved portions of samples from independent samples. We used the sum of the concentrations for each radionuclide to calculate doses.
Fish consumption rates vary widely. We used the fish consumption rate from an analysis of food consumption data collected by the U.S. Department of Agriculture and published in the journal, Health Physics [11]. The rate is 14.7 grams of fish per day per person, or about half an ounce per day or about 12 pounds a year per person [11].
TABLE II. DOSIMETRY OF HIGHEST MEASURED RADIONUCLIDES IN SURFACE WATER SAMPLES.
|
JULY |
NOVEMBER |
Proposed EPA Drinking Water Guidelines (pCi/L) |
|||||||
|
Dissolved |
Undissolved |
Dissolved |
Undissolved |
||||||
| Activity (pCi/L) | Dose1 (mrem) | Activity (pCi/L) | Dose (mrem) | Activity (pCi/L) | Dose (mrem) | Activity (pCi/L) | Dose (mrem) | ||
| H-3 (Tritium) | 5,900 | 0.02 | - - | 0.00 | 4,510 | 0.02 | - - | 0.00 | 60,900 |
| Pu-238 | 3.61 | 0.16 | 21.1 | 0.91 | 2.3 | 0.10 | 11.2 | 0.49 | 7.2 |
| Pu-239 | 0.032* | 0.00 | 0.16 | 0.01 | 0.12* | 0.01 | 0.087 | 0.00 | 62 |
| Th-227 | 0.21 | 0.00 | 0.085* | 0.00 | 0.38* | 0.00 | 0.029* | 0.00 | 400 |
| Th-228 | 0.13 | 0.00 | 0.64 | 0.01 | - - | 0.00 | 0.095 | 0.00 | 125 |
| Th-230 | 0.19 | 0.01 | 1.1 | 0.04 | 1.7 | 0.07 | 0.54 | 0.02 | 79 |
| Th-232 | 0.034* | 0.00 | 0.10 | 0.00 | 0.088* | 0.00 | 0.056 | 0.00 | 88 |
| U-234 | 0.93 | 0.01 | 0.20 | 0.00 | 1.6 | 0.01 | 0.32 | 0.00 | 30 |
| U-235 | 0.078 | 0.00 | 0.014* | 0.00 | 0.068 | 0.00 | 0.035* | 0.00 | 30 |
| U-238 | 0.80 | 0.01 | 0.13 | 0.00 | 0.78 | 0.01 | 0.10* | 0.00 | 30 |
| 1 Annual dose is component attributed to maximum value of radionuclide measured in surface water, across all samples, and assuming 10% of total annual water consumed is this concentration. Dose assumes the highest fractional uptake. Measurements are considered non-detect (i.e., zero) where the value was negative or the uncertainty associated with the measurement was greater than the value (see text). Values with asterisks (*) mean the uncertainty associated with the measurement is greater than 50% of the value measured. | |||||||||
Fish sometimes concentrate substances from the water where they live into their body tissues. This is particularly true for some metals, some pesticides, and polychlorinated biphenyls. This means that although low levels of metals such as plutonium in water may not pose a health hazard to someone who drinks the water, the metals could become more concentrated in fish and become a health hazard to someone who eats the fish. Concentration factors are computed as the concentration of a substance in fish divided by the concentration of the substance in the water where the fish live.
Concentration factors for metals in fish vary widely among different species of fish and depend on factors such as what the fish eat, how long the fish remain in a contaminated environment, and how the fish are processed. Concentration factors have been measured or estimated by a number of scientists for a variety of metals (including radionuclides) and for a variety of fish; however, the data from different studies are not all in close agreement.
For our calculations, we initially chose concentration factors for the radionuclides in our surface water samples from concentration factors compiled and analyzed in 1988 in a review of the available data [12]. The concentration factors range from 1.0 for tritium (which is not a metal) to 250 for plutonium in bottom-feeding fish. Using the highest concentrations of radionuclides in our water samples, we calculated a total annual dose of 30.3 mrem to a person who eats bottom feeding fish in these composite waters. Of this dose, greater than 94% results from the plutonium in the water.
The same study lists concentration factors for plutonium in planktivorous fish and piscivorous fish that are much lower than in bottom feeders--25 and 5, respectively, compared to 250 for bottom feeders. The total annual doses to people eating these fish are 4.6 mrem and 2.3 mrem, respectively. These concentration factors indicate that bottom-feeding fish concentrate plutonium much more than the other types of fish.
We also located concentration factors that were derived from fish collected in the Great Miami River near the Mound Plant. In one study, concentration factors for plutonium in fish range from 4 to 30 [13]. These values are much lower than 250 and would result in doses similar to those presented above for planktivorous and piscivorous fish (in the range of 2 to 6 mrem per year). In another study of fish from the Great Miami River, the concentration factors for plutonium were much lower--from 0.1 to 1.0 [14]. (Note: concentration factors less than 1 indicate the concentration of the metal is lower in the fish than in the surrounding water; i.e., there is no net concentration of the metal in the fish.) The study implies that these concentration factors are lower because they are based on plutonium in the fish filets and not in the whole body. The study indicates that only 1% to 2% of the plutonium taken into the fish's gastrointestinal tract gets into the rest of the fish; therefore, the amount of plutonium in the filets is much less than in the whole fish [15].
The concentration factors derived from fish collected from the Great Miami River are perhaps more representative of those for fish people would eat from the surface waters we sampled. However, we presented our dose estimates using the higher concentration factors for plutonium because there is much variation in measured concentration factors throughout the scientific literature and the higher concentration factors for plutonium provide a more conservative dose estimate. For comparison, we offer one more example: If we consider only the maximum concentrations of radionuclides we measured in the Great Miami River at the Chautauqua Bridge Road, and we use the highest concentration factor, 30, for plutonium reported from the studies in the Great Miami River, our annual dose from eating these fish is 2.1 mrem.
Our calculations indicate that even our worst-case assumptions result in a dose--30.3 mrem per year--that does not pose a health hazard to a person eating fish in the area waterways. We don't really think a person would eat a whole year's diet of fish from the waterways near the Mound Plant. And it is not likely that a person would eat only bottom feeders or regularly eat the whole fish (including gut)(1). The maximum dose, therefore, is an upper limit estimate of what a person might receive. The range of possible radiation doses that are plausible is wide, and it is likely that a person eating fish from the area would receive a dose much lower than the maximum we have calculated.
DOSIMETRY:
Potential pathways for human exposures from radionuclides in soil include soil ingestion and inhalation of resuspended soil. We have looked at the resuspension pathway by sampling airborne particulates. We evaluated the ingestion pathway for soils collected from the South Canal for an adult, a 1-year-old child, and a 5-year-old child and for soils from other areas only for an adult.
We used the EPA 600 values for ingestion of soil by a child and an adult; they are 200 and 100 milligrams per day, respectively [10]. Dose conversion factors for a 50-year committed effective dose for an adult are from ICRP 68 [9]; for a child they are from ICRP 67 [17]. Dose conversion factors for children are for commitment periods of 69 years for a 1-year-old child and 65 years for a 5-year-old child [17].
The values for soil ingestion are based on wet weight. The values reported in the data tables for the concentrations of radionuclides in soil are based on ash weights. Therefore, we used the ratio of wet to ash weight for each sample with the highest concentration of the nuclide being evaluated to convert from picocuries per gram of sample ash weight (pCi/gash) to picocuries per gram of sample wet weight (pCi/gwet) when calculating doses.
We do not expect that either adults or children will ingest soil every day of the year (an exposure period or an ingestion frequency of 365 days per year); therefore, we chose to use an exposure period of 90 days for a child and 30 days for an adult.
The doses calculated are for the maximum concentrations detected. We did not correct for background concentrations.
GROSS ALPHA/BETA:
We detected high gross alpha activity in several of the soil samples not from the canal. The alpha activity in the samples from the Community Park are most likely result from elevated levels of uranium, thorium, and radium [18].
We detected elevated gross beta levels in soil samples from the Community Park and a few other areas, but these levels probably result from the presence of naturally occurring radionuclides, including K-40 residue from decaying plant matter.
GAMMA SPECTROSCOPY:
The Cs-137 seen in most of the soil samples results from fallout from atmospheric weapons testing and is not a public health concern. The slight Co-60 seen in several samples could result from fluctuations in the detector backgrounds at the EPA laboratory.
We detected Ra-226 in several samples from the north end of the Community Park. The background level of Ra-226 in the Miamisburg area is approximately 1.5 to 2 pCi/g, and the samples from the picnic area in the Community Park are 6 to 8 pCi/g. The highest concentration of Ra-226 in soil was 8.9 pCi/g; this represents a dose of 0.02 mrem to an individual. We also detected elevated levels of the decay products of Ra-226 and Th-232 (i.e., Ra-228, Pb-212, and Tl-208) in this same area.
We did not detect gamma activity significantly above background levels at any of the other sampling locations.
TRITIUM:
We detected tritium in a majority of the soil samples from the Community Park and from the South Canal. The tritium levels are above background levels but are not high enough to pose a health hazard to the public. We saw low levels of tritium in the seeps along the Main Hill and also in soils north and east of the facility. The positive values in soils at Harmon Field could result from deposition of tritium from atmospheric water vapor.
We found the highest levels of tritium in soils along the North Canal--especially along the canal bottom. The highest concentration of tritium in soil, 277,000 pCi/L (soil water), or 27.2 pCi/gwet, represents a dose of much less than 0.01 mrem to an individual who would ingest this soil. We collected this sample at the south end of the Community Park across from where the kiddie playground used to be.
PLUTONIUM ALPHA SPECTROSCOPY:
As expected, we found high concentrations of Pu-238 in soils in the north and south Miami-Erie Canal and along the Overflow Creek all the way to the Great Miami River. The highest concentration, 789 pCi/gash, represents a dose of 1.4 mrem to an adult. These areas are scheduled to be remediated.
We detected low concentrations of Pu-238 in soil samples from the Community Park, north and east of the facility, and in two of the background samples. The highest concentrations apart from the Miami-Erie Canal and the Overflow Creek, were from the Community Park and in the golf course, 2.5 pCi/gash and 2.4 pCi/gash, respectively. They each represent doses of less than 0.01 mrem to an adult who would ingest the soil.
The only samples positive for Pu-239 were those from sites which had elevated concentrations of Pu-238. This measured activity may result in part from interference from Pu-238 in the sample. The highest concentration of Pu-239 was 4.8 pCi/gash; we collected this soil sample from the South Canal. Assuming this is really Pu-239 and not interference from Pu-238, it represents a dose of 0.01 mrem to an adult.
We also calculated doses for a 1-year-old and a 5-year-old child exposed to soils in the canals. We combined the highest Pu-238 and Pu-239 values; the total activities represent doses of 17.2 mrem and 13.1 mrem for a 1-year-old and a 5-year-old child, respectively.
Neither the Pu-238 nor the Pu-239, nor both radionuclides combined, pose a health hazard to children or adults who might ingest this soil.
THORIUM ALPHA SPECTROSCOPY:
The background levels measured for Th-227, Th-228, Th-230, and Th-232 are 0.2, 1.0, 1.5, and 1.0 pCi/gash, respectively. The majority of samples collected are at or below these background levels.
We detected elevated concentrations of thorium in the Community Park picnic area, at one site in the South Canal, and at one site in the North Canal. The Th-230 in a sample south of the Mound Plant appears unusually high since the uranium concentrations at this site were not elevated above background. The highest concentrations for each of the thorium nuclides, 0.88, 4.8, 4.9, and 4.8 pCi/gash, taken together, represent a dose of 0.02 mrem.
These levels of thorium in soils do not pose a public health hazard.
URANIUM ALPHA SPECTROSCOPY:
We detected elevated levels of uranium in soils in the picnic area of the Community Park and at two locations in the North Canal. The maximum uranium concentrations (5.9 pCi/gash U-234; 0.37 pCi/gash U-235; 5.0 pCi/gash U-238) taken together represent a dose of less than 0.01 mrem to an individual.
None of the uranium activities measured in soils are at levels of public health concern.
COMMENT:
The presence of uranium and its decay products, including Th-234 and Th-230, at elevated levels in the two samples from the picnic area of the Community Park, and the presence of elevated K-40 in these samples indicate that this area was used to store or dispose of ash from the coal-fired power plant that occupied a part of the site until the early 1970s [18]. This would explain the elevated external gamma readings obtained in this area also. The radionuclide concentrations we detected are very unlikely to be the result of releases from the Mound Plant.
We note that present EPA guidance for cleanup of Ra-226-contaminated soils is 5 pCi/g in the top 15 centimeters of soil and 15 pCi/g below that depth. The Ra-226 concentrations we reported for sites 01-07A and 01-07B exceed this guidance.
6. SEDIMENT SAMPLES
DOSIMETRY:
Potential pathways for human exposures from radionuclides in sediments include ingestion and inhalation following resuspension of dredged material. We evaluated inhalation directly by sampling air particulates.
We used the EPA 600 value for consumption of soil by an adult; it is 100 milligrams per day [10]. This value assumes occupancy in an area where bare soil is readily accessible. EPA 600 also recommends using an occupancy duration of 350 days per year. We chose to use a 365-day occupancy to be consistent with our evaluations of other exposure pathways. This will very likely greatly overestimate the impact from river sediments. The estimated doses below would be possible only if the sediments were dredged and deposited in an area where they were constantly accessible to the public.
We took dose conversion factors for a 50-year committed effective dose from ICRP 68 [9]. Because the consumption value is based on wet weight, we converted the concentrations for each radionuclide from pCi/gash to pCi/gwet when calculating doses.
We calculated doses for the maximum concentrations we detected. We did not correct for background concentrations.
GROSS ALPHA/BETA:
Samples from the east and west sides of the river had high alpha and beta results. This activity is associated with elevated levels of naturally occurring radionuclides.
GAMMA SPECTROSCOPY:
The presence of Cs-137 is a result of fallout from atmospheric weapons testing and is not at levels of health concern. The elevated levels of Ra-226/Ra-228 and K-40 are discussed below. The estimated dose from Ra-226 is 0.04 mrem. The radionuclides we detected using gamma spectroscopy do not pose a health hazard to the public.
TRITIUM:
No tritium was detected in these samples.
PLUTONIUM ALPHA SPECTROSCOPY:
Only 1 sample had positive results, 0.7 pCi/gash Pu-238, contributing a dose of 0.01 mrem. The plutonium detected is not a health hazard to the public.
THORIUM ALPHA SPECTROSCOPY:
Thorium-227, Th-228, Th-230, and Th-232 were detected in these samples. All of these thorium nuclides are naturally-occurring, and their presence would be expected in these samples. Th-232 and Th-228 also occur naturally in the earth's crust. The maximum dose, 0.02 mrem, is from Th-230. The thorium detected is not a health hazard to the public.
URANIUM ALPHA SPECTROSCOPY:
Positive uranium activity was found in all of the samples. This is expected. The east and west sides of the river southwest of the facility were highest at 1.3 pCi/gash. The ratios of the three uranium nuclides are appropriate for naturally occurring uranium, so this activity does not appear to result from releases from the Mound Plant. The doses for U-234 and U-238 are both less than 0.01 mrem. The uranium detected is not a health hazard to the public.
COMMENT:
The elevated uranium, radium, thorium, and potassium-40 detected in the east and west sites in the river downstream of the Community Park and Mound Plant could be explained by the presence of coal ash residues in the sediment [18]. If city workers buried ash from the coal-fired power plant that once occupied a part of the Community Park site, some of that ash could have been released to the river. That would explain the presence of the radionuclides found in the sediment survey.
7. PRODUCE SAMPLES
DOSIMETRY:
We reviewed several references to determine the average values for consumption of produce. The EPA 600 values appear to be the most current and are in agreement with those in other references [10]. The average adult eats about 200 grams of vegetables per day and 142 grams of fruit per day. About 25% of the vegetables in the average diet are home grown and about 20% of the fruits in the average diet are home grown. Thus, the total consumption of home-grown produce per day is (200 x 25%) + (142 x 20%), or about 78 grams.
We took dose conversion factors for a 50-year committed effective dose from ICRP 68 [9]. The tritium concentrations are listed as pCi/L water in the various samples. Data from ORNL-5786 indicate that the average water content of produce is 85% [19]. We used this information to calculate the tritium concentrations in pCi/gram.
We calculated doses using the maximum concentrations of radionuclides we detected. We did not correct for background concentrations.
GROSS ALPHA/BETA:
We did not detect any significant gross alpha activity. Other than the radionuclides we identify below, the gross beta activities we detected do not indicate the presence of any other radionuclides.
GAMMA SPECTROSCOPY:
We detected Th-234 in one sample--tomatoes from Leis Road. Th-234, a decay product of U-238, occurs naturally. The Th-234 in the tomatoes contributes an annual dose of 0.13 mrem to persons eating the tomatoes. The K-40 we detected is naturally occurring and will contribute a dose of 5.1 mrem to persons eating this produce.
TRITIUM:
We detected tritium in five samples, including one background sample. The highest value, 3,960 pCi/L of water in apples collected from the Community Park, represents a dose of 0.01 mrem. The tritium we measured in produce does not pose a health hazard to anyone eating the produce.
PLUTONIUM ALPHA SPECTROSCOPY:
We detected Pu-238 activity slightly above background in one sample of zucchini from a location in northeast Miamisburg. The Pu-238 activity represents an annual dose of 0.01 mrem. A background zucchini had a Pu-238 concentration of about one-half of this sample's concentration. There is no health hazard to the public from the Pu-238 we detected.
Pu-239 may have been detected in turnips from Shephard Road, but the uncertainty in the measurement was greater than 95% of the measurement. The dose from the Pu-239 would be 0.01 mrem; this amount of Pu-239 is not a health hazard.
THORIUM ALPHA SPECTROSCOPY:
We detected little or no Th-227 or Th-228 in any of the samples. Th-230 was present in all of the samples and four of six background samples. Only one sample had detectable Th-232. The maximum activities we detected for Th-230 and Th-232--0.028 pCi/gwet and 0.0045 pCi/gwet--represent doses of 0.62 and 0.11 mrem, respectively, to the public. The thorium we detected does not pose a health hazard to the public.
URANIUM ALPHA SPECTROSCOPY:
We detected U-234 and U-238 in all of the samples at very low levels. The highest activity, 0.018 pCi/gwet U-234, was in turnip greens collected from the a residence on Shephard Road. This activity appears to be from natural uranium in the soil and not from operations of the Mound Plant. The doses from the maximum concentrations of U-234 and U-238 are 0.09 and 0.04 mrem, respectively. The uranium we detected in produce does not represent a health hazard to people eating the produce.
COMMENT:
The radioactive potassium (K-40) that we detected in the produce contributes about 83% of the total annual radiation dose from eating the produce. This result is not unexpected. K-40 is the most abundant radionuclide in the human body, and it occurs naturally in all living things.
8. VEGETATION SAMPLES
DOSIMETRY:
Potential pathways for human exposures from radionuclides in vegetation (grasses and weeds from public areas), are ingestion and inhalation of resuspended decaying matter. There is no grazing in the area, so we did not evaluate the exposure pathway of consuming animals that eat grasses in the area.
For direct ingestion, we assumed an arbitrary consumption of 1% of the total produce consumed daily, 1% x 343 grams, or 3.4 grams per day. Although we don't expect people will intentionally eat grasses and weeds, this estimate should provide an upper limit on the dose to an individual of the public from contaminated grasses in the Community Park.
We used the EPA 600 value for consumption of produce by an adult [10]. We took dose conversion factors for a 50-year committed effective dose from ICRP 68 [9].
To evaluate the impact from inhaling resuspended decaying matter, we assumed that resuspension is a result of mowing. Title 10, CFR 61, recommends using a mass-loading approach when there is work involving the handling of contaminated soils [20]. It recommends assuming a resuspension of 565 micrograms per cubic meter of air. We used this value and assumed that all resuspended material was dried grass cuttings, which could be respired. We assumed that mowing required 4 hours per week over an area with the maximum concentrations for each nuclide, and that operations continued for 36 weeks a year. These assumptions should define the upper limit or maximum dose to an individual in the public.
The doses we calculated are for the maximum concentrations we detected. We did not correct our measurements for background concentrations in vegetation.
GROSS ALPHA/BETA:
We did not detect gross alpha activity in any of our samples. The gross beta activity we detected was consistent in all samples and would result from naturally occurring radioactivity in the samples.
GAMMA SPECTROSCOPY:
Gamma spectroscopy indicated the presence of Be-7 and K-40, which are naturally occurring, and Tl-208 in these samples. The Tl-208 (in the sample from Germantown) is suspect because other radionuclides that should have been present with Tl-208 were not detected.
TRITIUM:
Several vegetation samples had elevated tritium levels. The highest tritium level detected, 25,900 pCi/L from the North Canal, represents a dose from ingestion of less than 0.01 mrem and a dose from inhalation of resuspended particles of much less than 0.01 mrem to an individual in the public. This amount of tritium in vegetation is not a public health hazard.
The presence of tritium in the samples from residences on Mound Avenue at the bottom of the Main Hill shows that tritium is migrating in more than one direction.
PLUTONIUM ALPHA SPECTROSCOPY:
We detected Pu-238 in three samples and Pu-239 in four samples. The maximum Pu-238 and Pu-239 activities detected, 0.17 pCi/gwet and 0.0043 pCi/gwet, respectively, represent doses to the public of 0.01 mrem and much less than 0.01 mrem, respectively, from ingestion. Doses from inhalation of resuspended particles would be less. This amount of plutonium in grasses and weeds does not pose a health hazard to the public.
THORIUM ALPHA SPECTROSCOPY:
We detected Th-238 in 3 samples, Th-230 in 12 samples, Th-232 in 3 samples, and Th-227 in no samples.
The highest Th-228 activity detected was 0.013 pCi/gwet. This represents an ingestion dose of less than 0.01 mrem and an inhalation dose of less than 0.01 mrem. The presence of this radionuclide in the South Canal is uncertain, because Th-228 is a decay product of Th-232. No detectable Th-232 appeared in this sample.
The highest Th-230 activity was 0.014 pCi/gwet. This represents an ingestion dose of less than 0.01 mrem and an inhalation dose of less than 0.01 mrem.
The highest Th-232 activity was 0.01 pCi/gwet. This represents an ingestion dose of less than 0.01 mrem and an inhalation dose of less than 0.01 mrem.
None of the thorium radionuclides detected in the vegetation samples pose a health hazard--either individually or combined--to the public.
URANIUM ALPHA SPECTROSCOPY:
We detected U-234 and U-238 in all the vegetation samples, but only three samples had activities above levels of the background samples. The highest activities, 0.024 pCi/gwet U-234 and 0.014 pCi/gwet U-238, represent doses of less than 0.01 mrem for both radionuclides for both ingestion and inhalation pathways.
The uranium detected in vegetation does not pose a public health hazard.
DOSIMETRY SUMMARY
We added the doses from the various radionuclides we detected in all the environmental media to estimate maximum committed effective doses for inhalation and ingestion, considering all the exposure pathways we have described. We used the maximum concentrations of radionuclides we detected. We added radium-223 and radium-224 to the list of radionuclides in those samples where we detected Th-227 and Th-228. This is because Ra-223 and Ra-224 are decay products of thorium-227 and thorium-228, respectively. We expect they occur along with the thorium parent nuclides, even if we didn't detect them(2).
For the inhalation pathway, the media contributing to the radiation dose are air particulates, tritium in water vapor, and resuspended vegetation (from mowing the grass). The total committed effective 50-year dose for this pathway is 0.93 mrem per year.
For the ingestion pathway, the media contributing to the radiation dose are groundwater, surface water, soil, sediment, produce and vegetation (grass). Fish are not included here because they are discussed separately above. The total committed effective 50-year dose for the ingestion pathway is 9.7 mrem per year. Of this dose, the potassium-40 (K-40) that is naturally occurring in produce contributes 52%.
If we add all our doses for inhalation and ingestion and include the radiation dose from eating fish (30.3 mrem), we get approximately 41 mrem a year--even if we assume our exposed person is always eating bottom-feeding fish and we use our highest concentration factor for plutonium in fish. This total dose is calculated entirely from the maximum levels of radionuclides we measured under the maximum exposure scenarios that we assumed. We also did not subtract out components that are naturally occurring and are present in the background samples. Nevertheless, this dose is well below the 100 mrem annual dose, above background, to members of the public that the ICRP recommends.
In conclusion, the radionuclides we measured in all environmental media around the Mound Plant do not pose a health hazard to the public.
References
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