PUBLIC HEALTH ASSESSMENT
MONTICELLO MILL TAILINGS (DOE)
AND
MONTICELLO RADIOACTIVELY CONTAMINATED PROPERTIES
(aka MONTICELLO VICINITY PROPERTIES)
Substances released into the environment do not always result in human exposure. Human exposure to a nonradioactive chemical contaminant can occur only if humans come in contact with the chemical contaminant either by ingestion (eating or drinking a substance containing the chemical), inhalation (breathing air containing the chemical), or dermal absorption (skin contact with a substance containing the chemical). In the case of radioactive substances, human exposure can occur also when humans enter fields emanating from the substances.
To understand the type and severity of health effects that exposure to a specific chemical contaminant may cause, we must consider several factors related to an exposed individual's interaction with the chemical. Such factors include the amount or dose of the chemical to which a person is exposed, frequency and duration of exposure, route of the chemical's entry into the body (ingestion, inhalation, or dermal absorption), and the multiplicity of exposure (combination of chemical contaminant exposures).
Health effects are also related to such characteristics as age, sex, nutritional habits, health status, lifestyle, and family traits, all of which may influence how a specific chemical is absorbed (taken up by the body), metabolized (broken down by the body), and excreted (eliminated from the body).
To determine the possible health effects specific chemicals can produce, ATSDR representatives consider those physical and biological factors as well as a variety of informational sources, such as scientific literature, research reports, and reports from other agencies.
The following sections evaluate the potential health effects from exposure to contaminants from the Monticello Mill Tailings Site. The toxicological evaluation for each contaminant assesses probable health effects from exposure to the contaminant. These health effects relate to contaminant concentration, exposure route, exposure frequency, and population potentially exposed. Populations known to be or suspected of being sensitive to exposure to the contaminant are included. The information is presented for those pathways identified as completed exposure pathways for on-site and off-site surface soils and ambient air and for potential exposure pathways involving groundwater, surface water, and bioaccumulation of contaminants in the food chain.
Although ATSDR representatives have not yet completed their review and analysis of the data needed to estimate the risk to health from all radon-222 exposures, both indoors and outdoors, adverse health effects from exposure of the public to this gas outdoors in the vicinity of the mill site are highly unlikely. Two considerations led ATSDR scientists to the conclusion about outdoor exposure near Monticello:
1. Outdoor ambient radon-222 activity was not reported higher off site than 2.98 pCi/L (48). This level is less than the guideline of 4 pCi/L used by EPA as adequately protective against lung cancer from continuous long-term indoor exposure (49).
2. Outdoor exposure to radon in general is much less hazardous than indoor exposure because radon-222 gas itself is not directly capable of causing human lung cancer. Any radon-associated carcinogenic effects are from the radon daughters (products of the radioactive decay of radon-222) that are discussed in Appendix C. Unlike radon-222, the daughters are not gases, but solids. They form small particles suspended in the air. The particulate daughters typically dissipate more rapidly outdoors than indoors due to increased air flow outdoors. Radon-222 gas is almost eight times as dense as the ambient air and could remain measurable for some time.
It is indoor exposure in poorly ventilated space, in which the particulate daughters are confined along with the parent gas, that could present a health hazard if radon-222 activities are elevated. Some of the foundations of the structures on Monticello Vicinity Properties were poured from concrete containing material from the tailings piles (3). This material contains radium-226, which decays radioactively to radon-222. The radon daughters that would accumulate in these structures would be confined along with the radon-222 gas. In the record of decision for the Monticello Vicinity Properties, Department of Energy (DOE) representatives estimated average lung doses for 15 Monticello Vicinity (indoor and outdoor) Properties, indicating that DOE has indoor concentration data (3). Moreover, DOE reportedly has indoor radon-222 data for more than 1,000 vicinity properties. Staff members at ATSDR are scheduled to begin analyzing the database that contains this information during calendar year 1998. The completion and success of this activity is dependent on the quality and quantity of data provided by DOE as well as the financial funding provided by DOE. Appendix C of this document contains other information about radon-222.
ATSDR representatives calculated the radiation dose due to ingestion of radium-226 for the average (27 picocuries per gram (pCi/g)) and maximum (7,185 pCi/g) concentrations found in publicly accessible areas. The dose is based on the following scenario: persons playing outside 5 days per week for 1 hour per day. The route of exposure is via incidental soil ingestion (100 mgsoil/day).
The dose calculated using the assumptions described above for the average concentration is 0.05 millirem per year (mrem/yr) and for the maximum is 14.40 mrem/yr. Both doses include the radiation dose contributed by radium-226 naturally in the soil, and both are below the recommended dose limit of 100 mrem/yr (50). In addition, there is no apparent risk of increased cancer and no apparent health hazard due to long-term (in this case, assumed to be 45 years) chronic ingestion of radium-226 in the scenario.
c. Uranium-234 and Uranium-238
People are unlikely to suffer adverse health effects from the uranium present in water sources known to supply drinking water. However, the uranium content of the alluvial aquifer, which could potentially be tapped for drinking water in the future, could cause kidney problems if someone drank water from wells drilled at some future time (37, 42, 51). Because uranium was not reported at levels of concern in soil or sediment, amounts sufficient to cause adverse health effects are unlikely to have entered the food chain by bioconcentration from soil (51).
The hazard posed to the kidney by the chemical toxicity of uranium (especially so for its soluble forms) is greater than that posed by its radioactive properties (51). Drinking water used by residents near the mill site is either supplied by the city from surface water taken upstream of the mill site or taken from wells that tap the Burro Canyon Aquifer. These water sources have not exceeded activities of 30 to 43.5 pCi/L for uranium (43 to 62 µg uranium/L) (42, 51). The range of concentrations in water taken from city water upstream of the mill site or the Burro Canyon Aquifer is unlikely to result in kidney damage to children or adults from the chemical toxicity of uranium, nor would it pose a significantly increased likelihood of cancer from uranium radioactivity (52).
Since 1984, the alluvial aquifer rarely exceeded uranium activities of 533 pCi/L, although concentrations as high as 2,870 pCi/L have been reported recently (42). No wells are known to draw from this aquifer. However, it is possible that some wells might do so now or in the future in the absence of institutional controls, such as ordinances to prevent screening this aquifer. Children and adults who drink this water in the future would be at risk for kidney injury. If people use this water in the future as their sole drinking water source for their entire lifetimes, they could have, in the future, a moderately increased risk of cancer from the radioactive properties of uranium (52).
A.2 Nonradioactive Contaminants in Soil and Sediment
The concentration of beryllium in soil (1 part per million [ppm]) is insufficient to cause cancer or noncancer health effects through soil ingestion (37, 53). No significant adverse effects were produced in any of the studies in which animals were orally exposed to greater amounts than humans could be assumed, by the most conservative scenarios, to ingest from this soil (52, 53). Beryllium is known to cause lung cancer in humans and animals exposed by inhalation, although not all beryllium is capable of producing lung cancer. Very specific forms of beryllium oxides have the proven potential, but other forms are relatively inert. However, calculations described in Appendix C established the fact that windborne soil would not contain enough beryllium to present a significantly increased risk of cancer by inhalation. The concentration of beryllium in off-site soils is well within the range of beryllium soil concentrations reported for the United States in general and for Utah soils and sediments in particular (37, 54). Bioconcentration of soil beryllium by locally grown produce or grazing animals is not expected to generate dietary beryllium intake greater than would normally exist.
The 22 ppm chromium maximally present in off-site soil and sediment samples is well within the soil chromium concentration range found in the state of Utah and is not a threat to the public's health (37, 52, 54). Environmental chromium occurs primarily in two chemical states: chromium-III (Cr-III) and chromium-VI (Cr-VI). Cr-III, which is environmentally very stable, is nutritionally essential for health and not harmful at soil concentrations 100 times that maximally reported (52). Even if all the chromium originally released to the soil were Cr-VI, which is much more toxic, especially if inhaled, it would be readily converted to Cr-III (55, 56, 57). The concentration of chromium in the soil (22 ppm) off site could be of concern to children who play in and daily ingest large quantities of the soil only in the highly unlikely event that nearly all the chromium had persisted in the environment as Cr-VI for the 30 years since the mill closed. We did not analyze air for respirable chromium in either oxidation state, but using the method described in Appendix C for beryllium, the soil chromium content, even if entirely Cr-VI (unit inhalation risk of 1.2 x 10-2 (µg/m3)-1), could not present a significant risk of cancer through inhalation (52).
The off-site soil concentration reported is well within the range of chromium soil concentrations reported for the United States in general and for Utah soils and sediments in particular (37, 54). We believe that even persons whose entire diet consists of homegrown items will take in chromium within the general range ingested within the United States -- 0.025-224 mg/day -- an intake level not expected to produce adverse effects (58).
Lead was present in off-site soil and sediment at concentrations up to 22 ppm (37). ATSDR does not regard lead soil concentrations in this range to be a significant threat to human health (59). The concentration of lead in off-site soils is well within the range of lead soil concentrations reported for the United States in general and for Utah soils and sediments in particular (37, 54). Bioconcentration of soil lead by locally grown produce or grazing animals is not expected to generate dietary lead intake greater than would normally be the case. For more details about adverse health effects that might be seen in children residing where soil lead concentration was reported at higher levels than found adjacent to Monticello, see Appendix C.
No adverse effects are anticipated from the reported concentrations of nickel in off-site soil (37, 52). The absence of nickel at levels of concern in groundwater or surface water suggests that the soil nickel is in a poorly soluble form and likely to be poorly absorbed if ingested. Moreover, nickel was present in off-site soil at 16.2 ppm, a concentration well within the natural background of Utah soils and alluvial sediments (37, 54). Bioconcentration of soil nickel by locally grown produce or grazing animals is not expected to generate dietary nickel intake greater than would normally be the case.
Thallium might be present in off-site soil at concentrations above 0.2 ppm and might therefore be sufficient to cause adverse health effects in children who exhibit pica behavior -- i.e., children who ingest non-nutritive substances, such as soil (37, 60). This substance, which ranged up to 3 ppm in soil on site, was below its quantitation limit of 2 ppm in off-site soil (37). The concentration of thallium normally occurring in Utah soil is not known (54). Thallium is absorbed by plants from soil and enters the food chain; dietary intake is probably the major source of human exposure to thallium (61). ATSDR scientists did not have necessary data on the concentration of thallium in locally grown produce to evaluate the potential for adverse health effects from eating food grown in residents' backyards. For information about the toxicity of thallium, see Appendix C.
A.3 Nonradioactive Contaminants in Groundwater
The arsenic present in known drinking water sources is insufficient to cause adverse health effects, and there is little likelihood that the arsenic in one potential future source of drinking water (future wells that may draw from the alluvial aquifer) could cause health problems (see Appendix C). The average United States diet supplies about 50 µg arsenic each day, much of it because of arsenical pesticides, a more likely source of arsenic in home-grown foods than is bioconcentration of site-related arsenic in irrigation water (62).
When the facility was in operation, children swam in the tailings ponds. Dermal exposure to arsenic is not known to cause harmful effects other than contact dermatitis. The children might have ingested some of the water while playing, and their likelihood of being harmed would depend on the arsenic concentration in the ponds at that time. That concentration of arsenic is not known, although it might have reached or exceeded the level of 48,000 µg/L (48 ppm) reported in groundwater in some western mining areas (62). Water in the tailings pond could have been higher because of its origin -- direct runoff from the tailings pond. A small (10-kg or 25-pound) child playing in the water could swallow 50 ml (1-2 tablespoons) of water each swim. Repeated splashing and dunking could lead to ingestion of several times that amount on a single warm afternoon, with the child ingesting as much as 10 mg arsenic (1 mg/kg/day), if the water at the tailings pond was contaminated to that extent. ATSDR scientists found reports that 1 to 2 mg/kg/day of inorganic arsenic from contaminated water resulted in nausea and vomiting, followed by severe abdominal pain, bleeding in the digestive tract, and in some cases, death by renal failure (62). Children who had no acute adverse effects after swimming in the ponds on several occasions or who stopped swimming in the ponds because it made them feel sick are unlikely to be at risk now. Levels of arsenic insufficient for such acute effects but substantially above that in current drinking water, if ingested daily over many years, could cause the chronic arsenic poisoning (blackfoot disease, symptoms similar to Raynaud syndrome, and cancers of the skin, liver, and lung). For additional information, see Appendix C.
Molybdenum was not present at levels of health concern in known drinking water sources or in off-site soil (37). However, if in the future some off-site residents draw drinking water from the alluvial aquifer and at the same time derive a substantial proportion of their food from homegrown produce, they could be at risk for gout-like illnesses (52). Up to 213 parts per billion (ppb) molybdenum was present in the alluvial aquifer downgradient of the mill site, and up to 340 ppb molybdenum was present in surface water used for irrigation downstream of the mill site (1, 42). Plants may bioconcentrate molybdenum from the irrigation water so that their molybdenum content is increased by five times the molybdenum content in the soil in which they grow (63). Data on the molybdenum content of grains, fruits, and vegetables grown on properties near the Monticello Mill Tailings Site are not available. Therefore, ATSDR scientists are not able to determine whether total molybdenum intake levels are sufficient to cause adverse health effects.
Between 1984 and 1995, well after the end of milling operations, surface water (Montezuma Creek) on site has been contaminated with as much as 3,420 ppb molybdenum (42). During operations and in the decades immediately following, Montezuma Creek molybdenum concentrations may have reached higher values than 3,420 ppb. It is possible to speculate that similar concentrations of molybdenum were present in the tailings ponds when the facility was in operation. If children swam in the ponds often over many years, they could have ingested enough molybdenum to have interfered with their ability to use dietary copper and put them at risk for hypochromic microcytic anemia (52).
Nitrate was not present at levels of health concern in known drinking water sources (37). If in the future, some families living off site draw their drinking water from the alluvial aquifer downgradient of the mill site (33 ppm), their newborn infants could be 10 times more likely than those drinking water from the alluvial aquifer upgradient of the mill site to become cyanotic (turn blue) from increased levels of methemoglobin (an oxidized red blood cell pigment that has lost its ability to carry oxygen) in their blood (42, 52). There are several reasons why these babies could be vulnerable. Shallow wells, such as those that in the future might draw from the alluvial aquifer, are more readily contaminated by bacteria than are deeper wells, such as those that draw from the Burro Canyon Aquifer. The stomach juices in newborns, especially those 3 months old or younger, are less acid than those in older babies, children, and adults. The low acidity favors bacterial growth in the stomach. Stomach bacteria can convert ingested nitrate to nitrite. Because of the lower acidity in the infant's stomach, the conversion can proceed to a greater extent than the 5% to 10% that occurs in adults. Nitrite attacks hemoglobin, resulting in the cyanosis described above when infants drink water containing more than 10 ppm nitrate (52).
Nitrates are used to fertilize soils to improve plant growth. The effectiveness of this practice stems from plant metabolism of inorganic nitrate to precursors of plant proteins. Minor additional quantities of nitrates from use of the alluvial aquifer for irrigation are not expected to result in toxic levels of nitrate in the local diet.
Selenium was not present at levels of health concern in known drinking water sources (37). Selenium is an essential element in human nutrition; the National Academy of Sciences recommends adults consume 55 to 75 µg selenium per day to prevent deficiency (64). If the intake from food and water is as low as 7 to 11 µg/day, the deficiency causes adverse effects to cartilage tissue and the heart (65). These effects can be treated with supplements of 230 to 920 µg/day (65). The mean United States daily intake is 83 to 129 µg/day (64). Ingestion ranging from 240 to 1,510 µg selenium per day, an amount that could require drinking 4 gallons of off-site alluvial groundwater daily (should future wells tap this aquifer) does not produce harmful effects (1, 42, 65). However, excessive selenium intake can cause adverse health effects; continuous total intake of 3,200 to 6,690 µg selenium per day has caused damage to nails and hair, blistered skin, tooth decay, numbness in hands and feet, paralysis, and convulsions (65).
Between 1984 and 1995, well after the end of milling operations, surface water (Montezuma Creek) on site has been contaminated with as much as 3,110 ppb selenium (42). During operations and in the decades immediately following, Montezuma Creek selenium concentrations may have reached higher values than 3,110 ppb. It is possible to speculate that similar concentrations of selenium were present in the tailings ponds when the facility was in operation. Children who swam often in the tailings ponds for many years could have been at risk.
Moreover, Utah is one of the states known to have highly seleniferous soils and plants that can cause ingestion of amounts of selenium that could be of health concern (65). It is possible that use of irrigation water drawn from the alluvial aquifer could increase the potential for adverse health effects from naturally occurring selenium in produce and meats from Utah.
Vanadium has not been associated with cancer in people or animals by any route of exposure (66). The substance was not reported in sufficient concentration for acute exposure to gusts of wind to cause bouts of coughing and other signs of respiratory irritation to on-site workers or off-site residents (1, 37, 66). Should the highest reported on-site concentration occur frequently off site, however, persons with asthma and others with chronic respiratory problems might experience increased symptoms (66). Adverse effects to workers from prolonged exposure are not anticipated because the highest on-site concentration reported is below the threshold limit value required by the Occupational Safety and Health Act (67).
Vanadium has not been identified at levels of health concern in known drinking water sources (37). The likelihood of kidney damage to people who might in the future have wells that tap the alluvial aquifer or to children who frequently swam in the tailings ponds for many years is unclear (1, 66). Contamination of foodstuff is more likely to result from adhesion of vanadium-containing fertilizers than from bio-uptake of contaminated water (66). For additional information about the toxicity of vanadium, see Appendix C.
A.4 Nonradioactive Contaminants in Air
Sulfur Oxides, Sulfurous Acid, and Sulfuric Acid
Oxides of sulfur and the acids (sulfuric and sulfurous acid) they form on contact with moisture could have resulted in an increase in respiratory diseases among nonsmokers depending on the concentrations that were present in the ambient air, although it is not clear whether the adverse effects might have persisted to the present. These substances, in unknown concentrations, were probably responsible for the sulfur odor and damage to clothing and automobile chrome trim noted by off-site residents when the plant was operating (see the Community Health Concerns sections). At that time (1960 or earlier), the ambient air concentration of these substances exceeded the odor threshold for sulfur oxides (0.007 to 0.03 ppm) by an undocumented quantity which was, however, sufficient to cause the damage described earlier (68). Concentrations of sulfur dioxide as low as 0.04 ppm have been associated with chronic obstructive lung disease in nonsmokers (69). The study reporting this association did not examine the persistence of respiratory injury. However, another study reported decreased mortality due to chronic bronchitis that lagged about 4 years behind improvement in air quality resulting from pollution controls designed to lower ambient sulfur oxide concentration (70). These two unknown quantities (the concentration of sulfur oxides present during mill operation and the persistence of injuries that might have resulted from exposure at that time) add considerable uncertainty to the possibility of predicting the likelihood that current respiratory disease might stem from past inhalation of the mill's sulfur oxide emissions.
B. Health Outcome Data Evaluation
Representatives of ATSDR and Boston University identified and reviewed many sources of health outcome data for the Monticello area. In response to the large number of health concerns voiced by former workers at the Monticello Mill Tailings Site, they conducted a search of available literature on studies of uranium mine and mill workers. A few of the studies mentioned the Monticello mill with respect to industrial hygiene surveys. ATSDR staff members were able to determine from those studies what the conditions were like in and around the mill and whether the types of diseases present in the mill workers were also present in the community surrounding the mill.
Worker Issues
Representatives of the occupational health program of the U.S. Public Health Service performed environmental surveys in many uranium mills in the western United States, including the Atomic Energy Commission (AEC) mill in Monticello, during the 1950's. Workers in most of the mills where industrial hygiene surveys were done experienced a chronic irritation of the upper respiratory tract, presumably caused by the vanadium fumes escaping from the fusion furnaces. Workers in the vanadium processing areas of the mill(s) had a green coating of the tongue and teeth, and workers in the uranium leaching process had a yellow coating of the tongue and teeth (71, 72). The surveys revealed that 26.5% of the white millers showed more than usual pulmonary fibrosis compared with 7.5% in the control group. Twenty percent of the Indian millers showed more than usual pulmonary fibrosis compared with none in the control group.
One of the initial uranium mill worker studies involved medical examinations of 715 participants from 6 mills between 1950 and 1953. The mills were in the Colorado Plateau states (Colorado, Utah, New Mexico, and Arizona). The workers were followed over time, and 104 of them died between 1950 and 1967. The rate was nearly the same as the expected 105.11 rate (71, 72). However, the excess deaths due to malignant diseases of the lymphatic and hematopoietic tissue other than leukemia did appear to be meaningful, even though the numbers involved were small.
Representatives of the Health and Safety Laboratory of the AEC also performed a study of approximately 215 workers at the Monticello Ore Concentrating Plant in 1957 to determine the levels of radioactive dust exposures workers were experiencing. The study revealed that there was no effective dust control equipment throughout the plant. It also showed that 86 employees out of the total plant population were exposed to average dust concentrations above the maximum allowable concentration (MAC). Nineteen of those were exposed to greater than five times the MAC. The areas in the mill that exceeded the MAC were the ore sample plant, crushing areas, sample preparation area, and yellow cake drying area (73). The survey showed that workers in the mill experienced no hazard from external radiation (beta plus gamma or gamma only) (73). According to the survey, there had been a urine sampling and assaying program in place since 1956. All plant personnel were included in the program, and those workers in areas having higher air dust levels were sampled weekly. ATSDR scientists have not been able to obtain documentation of that program.
In 1971 and 1972, representatives of the National Institute for Occupational Safety and Health (NIOSH) performed a retrospective cohort study of 2,002 uranium mill workers who had worked at one or more of seven mills in the Colorado Plateau region. The study sought to determine the possible relationship between exposure(s) to uranium, thorium, and radium and the development of malignant and nonmalignant diseases. The risk of mortality among the uranium mill worker cohort was analyzed from 1940 to 1977. Results from the study showed no statistically significant excesses of any malignancies. However, although not statistically significant, there was an excess of chronic renal disease. There was also a significantly elevated standard mortality ratio (SMR) because of nonmalignant respiratory disease. Analysis of the study determined that the elevated ratio was caused by emphysema, fibrosis, silicosis, and chronic obstructive pulmonary disease (74). The study revealed that, in those workers who had worked for more than 10 years in the mill, there was only 1 lung cancer death observed, compared with the 5.7 expected (74). This particular study did not reveal an association between lung cancer and working in uranium mills. There were no subcohorts identified and most likely there are none that exist.
ATSDR representatives have used this information as background as we looked for similar adverse health effects in the community of Monticello. It appears that the green and yellow coating of the mouths and on the tongues of the workers were acute, short-term effects and consequently would not be listed in any type of health-related database. ATSDR staff members did not receive any concerns regarding such coatings in any of their public availability sessions. Most of the concerns that came from the public availability sessions were about cancer.
Cancer
Cancer has been a reportable disease in Utah since 1948, but there was not a statewide population-based registry until 1966. The Utah Cancer Registry is part of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. Utah has the lowest overall cancer incidence in the SEER system and the lowest overall cancer mortality rate of any state. The main reason seems to be the low smoking rates and the associated low rates of smoking-related cancers. Since becoming part of the SEER system, Utah has had an incidence rate approximately 16% below national rates, and mortality rates are approximately 28% below the national average. As of September 1992, Utah males have a lifetime risk of developing cancer of approximately 20%, and Utah females have a lifetime risk of approximately 24% (75).
In the publication Cancer In Utah, there were cancer incidence rates for each county in 10-year increments. Incidence rates are the number of new cases of disease in a population over a period of time. The incidence rates measure the probability that healthy people will develop a disease during a specified period of time. (The numbers for some years were so small that comparisons would not have been statistically significant with less than a 10-year increment.) The Utah Cancer Registry also provided statistical tables summarizing cancer incidence in Monticello and Blanding residents diagnosed between 1967 and 1992. For most of the analyses of cancer, the population exposed was assumed to be the entire population of Monticello, primarily because the documented radioactive hazards were quite widespread in the community, and there were several potential pathways for exposure. Table 14 shows the number of cancer incidence cases for Monticello and Blanding, both located within San Juan County.
In general, cancer rates for San Juan County tend to be below the rates for the rest of Utah, but these data are not adjusted for different proportions of the population of different ethnic or religious origins; however, they are age-adjusted. The sites and cancer types reviewed included the following: bladder, breast, cervix, colon/rectum, leukemia, lung, lymphoma, melanoma, pancreas, prostate, and uterine corpus. The years reviewed were 1966 to 1975 and 1981 to 1990. Table 15 shows the cancer incidence ratio of San Juan County compared with the ratio for the state of Utah. Cancer of the cervix is the only type of cancer whose rate is significantly elevated in San Juan County as compared with rates for the state of Utah. This type of cancer would not be associated with the contaminants present at the mill site.
ATSDR representatives searched the CDC Wide-Ranging Online Data for Epidemiologic Research (WONDER) database for incidents of malignant neoplasms of the respiratory and intrathoracic organs in San Juan County and compared the age-adjusted rates with the state of Utah rates. Intrathoracic organs include the larynx, trachea, bronchus, and lung. The white population rate in the county was 39.9, while the state rate was 24.6 (76). Rates for all other races were below the state age-adjusted rate.
ATSDR representatives reviewed EPA's Riggan's Mortality Tapes and identified two large percentage rate changes for white males living in San Juan County between 1950 and 1970. Between the years of 1950 and 1959 and 1970 and 1979, there was a 395% increase in trachea bronchus lung pleura cancerous deaths (77). Tracheobronchial lymph nodes tend to be the site of greatest concentration for inhaled uranium and thorium (71, 72). There was also a significant excess of deaths from prostate cancer between 1960 and 1969 compared with rates for the U.S. population during the same period. Prostate cancer is the most common type of cancer among Mormon males (78). Radiation has not been shown to be a factor in increasing the chances of developing prostate cancer. Between 1960 and 1969 and 1970 and 1979, there was a 287% increase in breast cancer mortality in white females living in San Juan County (77). Exposure to high levels of radiation is known to increase females' chances of developing breast cancer.
ATSDR staff members also noticed that the population of Monticello made up approximately 15% of the county population during the years 1966 to 1975 and 1981 to 1990; however, Monticello's cancer cases during those periods made up 27% of the cancer cases in San Juan County (77).
Insoluble uranium tends to be retained in the alveolar passages of the lung, whereas soluble uranium is retained in the bone (79). Three mortality cases due to bone/jaw cancer were reported between 1950 and 1979 in San Juan County. Although studies have indicated a possible link between long-term, low-level exposure to enriched uranium produced in enrichment facilities, a relationship has not been observed for natural uranium which is found at the mill site.
Cancer mortality in general and lung cancer mortality in particular were examined among Monticello residents. Data provided by the Utah Department of Health made it possible to compare cancer mortality among Monticello residents with rates for San Juan County and the state of Utah. We compared Monticello residents' odds of dying of lung cancer to their odds of dying from some other cancer with similar odds for other San Juan County residents. The risk of dying of lung cancer among Monticello residents during the period 1967 to 1992 was 2.5 (95% confidence interval 1.03-5.8). This comparison provides some limited evidence that during these years there was excess risk of dying of lung cancer in Monticello compared with risk for a county (San Juan) with a low overall risk of death from this disease. When the lung cancer mortality data were broken down into shorter time intervals, or for males and females separately, the numbers were too small for meaningful analysis.
A memorandum to the director of the National Communicable Disease Center reported that,
between 1956 and 1965, four children who were residents of Monticello, Utah, (1960
population: 1,845) developed acute leukemia. On the basis of the leukemia mortality rate for the
United States in 1960, only one leukemia case in 30 years would be expected among children in
a town the size of Monticello (80). A review of the childhood cancer cases for Monticello
between 1967 to 1992 revealed only one cancer, a case of acute lymphoblastic leukemia
diagnosed in 1970 (75). The cause of the leukemia clustering is still not known. ATSDR staff
members were told that a leaking underground gasoline storage tank, which was in the area of
the cluster, had been removed shortly after the cases were identified (81). ATSDR
representatives checked the state records for underground storage tank removals in Monticello,
however, and there was no record of one being removed from the area of the cluster (82).
| Table 14. Cancer Incidence Cases (1967-1992) (75) | ||
| Cancer Sites | ||
| Lip | ||
| Stomach | ||
| Colon | ||
| Rectosigm | ||
| Rectum | ||
| Pancreas | ||
| Lung | ||
| Blood System | ||
| Skin | ||
| Breast | ||
| Vagina | ||
| Cervix Uterine | ||
| Corpus Uterine | ||
| Ovary | ||
| Prostate | ||
| Kidney | ||
| Bladder | ||
| Brain | ||
| Thyroid | ||
| Lymph Node | ||
| Unknown | 3 | 8 |
| Table 15. Cancer Incidence Ratio of San Juan County Compared With That of the State of Utah (75) | ||
| Cancer Type or Site | 1966-1975 | 1981-1990 |
| Bladder | .643 | .168 |
| Breast | .811 | .497 |
| Cervix | 1.286 | 2.567 |
| Colon/Rectum | .289 | .523 |
| Leukemia | .907 | 1.042 |
| Lung | .679 | .963 |
| Lymphoma | .532 | .394 |
| Melanoma | .631 | .519 |
| Pancreas | .851 | 1.549 |
| Prostate | .950 | .477 |
| Uterine Corpus | .795 | .823 |
| All Sites | .705 | .684 |
Damage to the kidneys seems to be the primary systemic health risk in humans from exposure to non-enriched uranium. Statistically significant increases in deaths due to chronic and unspecified nephritis and renal sclerosis have been reported for uranium millers (74). One noncancerous cause of death, end-stage renal disease, was considered, based on toxicologic effects of uranium.
We used the CDC WONDER system to review renal failure for males and females in San Juan County. The database covers mortality for the years 1979 to 1991. There were four cases for males, and the age-adjusted rate was equal to the average rate for all counties in Utah that had reportable cases during the same period. There were 11 cases for females, and the age-adjusted rates were higher for San Juan County than for any other county in Utah. The age-adjusted rate for white women was double the rate for all other races in San Juan County (76). The map following depicts the rates of renal failure for each county in the state (76).
Staff members at the University of Michigan maintain a special database on end-stage renal disease, the U.S. Renal Data System, for the National Institutes of Health. The data primarily reflect Medicare reporting of kidney dialysis, and they are available only for the recent past; however, 1991 data were available for San Juan County and for the state of Utah. These data indicated that there were five cases of end-stage renal disease in San Juan County and 445 cases in the rest of Utah. This number does not represent a disproportionate percentage of cases of this disease in the county; the database does not indicate how many of the cases were in Monticello.
The rate of infant mortality in Utah has consistently been lower than rates for other parts of the United States (83). Studies have shown that congenitally malformed children are more frequently born to mothers who use alcohol, drugs, or tobacco than to mothers who refrain from using such products. Seventy percent of the study population included members of the Church of Jesus Christ of Latter-day Saints (Mormons), who discourage the use of alcohol, tobacco, and other drugs. However, Seegmiller and Hansen were unable to show through their research that the decreased use of these products had any effect on the rate of congenital malformations in the state. Their research concerning congenital malformations in children born in Utah during the years 1968 to 1972 shows that San Juan County had the highest rate of any county in the state of Utah. The results show that San Juan County had the highest percentages of mothers receiving late or infrequent prenatal care and the lowest mean level of public education (84). Interhospital variation in reporting might have had an effect on the higher rates reported for San Juan County.
There were no relevant hospital discharge data to review because the system for centralized reporting was only established in 1992. There were no other major causes of death for which there were sufficient numbers of decedents in Monticello or for which there was a plausible end-point based on the pathways and exposure analysis described in previous sections of this document.
The major problem in evaluating all the health outcome data described in this section has to do with numbers: the small size of the Monticello population, the small numbers of health outcomes observed, and the uncertainties about the size of the exposed population. The small number of cases makes it difficult to calculate meaningful age-adjusted disease or mortality rates. Once the rates are calculated, there tend to be large standard errors and little statistical significance. Therefore, rate comparisons or odds ratios may not be representative of the true risk of disease because it was impossible to adjust for different age distributions in the compared populations. Furthermore, several of the databases are available only at the county level, whereas the likely exposed population may be limited to parts of Monticello. In addition, persons exposed to contaminants from the uranium mill may have moved away years before they developed health problems or died of them. These former residents will not be identified in the databases we reviewed while preparing this document.
ATSDR scientists will continue to review any future health outcome data resources that become available. Should additional information become available that alters the findings of this public health assessment or addresses issues described herein, this public health assessment will be modified as needed. There are completed exposure pathways and the allegation of substantial exposure and serious diseases. Health studies need to be considered that would address the level of current and past exposures and their relationships. ATSDR scientists plan to thoroughly investigate and analyze DOE's residential/property database, which contains environmental data for each off-site property. The completion and success of this activity is dependent on the quality and quantity of the data as well as the financial funding provided by DOE. The community's Monticello Uranium Mill Impact Survey and the leukemia study performed in the 1980s both contain pertinent information. All these resources are an integral part in helping more clearly define exposure and disease rate and to determine what is occurring medically.
C. Community Health Concerns Evaluation
Potential mill site-related health effects for the Monticello residents fall into two categories:
The source and intensity of irradiation, radionuclide particle size of emitted material, dose rate, and pathway influence the degree of public health risk, influencing induction of nondeterministic and deterministic effects. Normally, deterministic effects are associated with chemical toxicity or acute high doses of radiation exposure. On the other hand, carcinogenic effects can be related to radiation. Animal studies have shown that external radiation exposure advances the onset of naturally occurring malignancies, especially leukemia and breast cancer; internal radiation normally affects the tissues where the radionuclides concentrate, e.g., lung and bone cancer (86).
Studies have shown that lower level exposure has constituted an occupational hazard in radiologists and physicists with the prevalence of acute and chronic myelogenous leukemia; cases involving both irradiated Western populations and Japanese populations show similar results. However, humans exposed to ionizing irradiation have not shown significant cases of chronic lymphatic leukemia (87).
Workers at the Monticello Mill Tailings Site experienced situations that led to their inhaling radioactive particles and radon gas. Figure 19 in Appendix F contains an illustration of the air-inhalation pathway. One concern was the workers' exposure to yellow cake. Inhaling or swallowing yellow cake can induce chemical toxicity of the lung, kidney, and liver. Both animal and epidemiologic studies indicate that kidney failure is the most likely chemical health effect of uranium in humans, whereas bone cancer is the most likely radioactive health effect. The evidence also suggests that chronically inhaling uranium dust in the workplace can cause lung cancer. The case for this is so weak, however, that we cannot determine the level of risk (88). One should expect, however, that people who did not work at the plant should not develop lung cancer from breathing the dust. Breathing the dust includes breathing the ore that mining trucks dropped on the way to the mill and vehicle traffic resuspended as well as breathing the dust shaken from a miller's work clothes before washing them. Such dust is inhaled for short intervals or at low concentrations, causing much lower exposures than the mill workers received. Because uranium intakes can be detected years later, some Monticello residents were tested. Their internal levels of radioactive material were below those of the control subjects in the studies (13).
Other people lived on the mill site during the period when the mill was operating. Depending on the prevailing wind direction, they could have received more radiation exposure than local residents. The exposure would have been from direct radiation from the mill site, radon gas, ore dust, and the chemical and radioactive effluents. Their cancer risk would depend on the radiation levels at those locations, the concentration in the air, and their individual life-styles.
Children were observed playing on the tailings piles for several years after the mill ceased operation. Based on the exposure rates from those tailings and their exposure time, their dose was well within the public dose limits and should not have caused any adverse health effects. The probability of their developing childhood leukemia was remote. Other childhood and adult diseases that would be more likely to occur as a result of radiation exposure have not been observed.
Occupations that involve soil excavation will temporarily expose workers to elevated levels of radon gas and its daughters. This phenomenon is normal, and these increased levels are expected regardless of the location because radon gas escapes naturally from the earth at all times. The rate at which radon gas escapes is determined by the soil's uranium and thorium content, its moisture level, and the prevailing temperature and pressure. The digging process loosens the soil and allows the radon gas to escape more rapidly for a time. The radon typically dissipates quickly and the levels return to normal, causing no harm. Shallow ditches and graves can be dug without concern for radon levels. Deep holes with small entrances will create higher and more lingering concentrations of radon and other gases because of poor ventilation. They should be ventilated and certified gas free before people enter, as is standard with underground mines, tunnels, and storm drain systems. If the digging will unearth thick tailings on the mill site, as when wells are dug, enhanced concentrations will occur. Such processes should be controlled by appropriately trained and equipped personnel (89).
Test wells have been bored at numerous locations throughout and beyond the mill site. The wells are sampled periodically for identification of any migration of radioactive materials from the mill site. They will be maintained as sampling points to assure that remediation efforts are effective. It is occasionally necessary to rebore a well to maintain its integrity. Reboring should be done under controlled conditions to protect the workers and contain any contamination.
DOE representatives found that 1,608 curies of radon gas escapes annually from the tailings piles (31). The rate is 160 picocuries per square meter second (pCi/m2s) averaged over the entire mill site. This is 8 times the EPA guideline of 20 pCi/m2s (90) and 400 times the world average of 0.42 pCi/m2s (91). Moving the tailings to another location or covering them with a sufficiently thick layer of claylike material will create a satisfactory reduction. These levels will soon be lowered; the piles are only temporary storage for materials from the remediated properties. Once remediation is completed and the tailings are removed or covered effectively, only the natural levels of radon should remain.
Radon gas is also present inside buildings. Scientists measured the radon levels inside Monticello homes of the persons who experienced severe health effects. The EPA studies were conducted in 1986. The radon levels measured were very low. Some data were reported in units of picocuries per liter (pCi/L) while others were in units of working levels (WL)(1) . EPA often assumes that the isotopes to which radon decays are at one-half the concentration they would reach if left undisturbed in a closed area. Under these normal conditions, 1 pCi/L is equal to 0.005 WL. The data below use this conversion. The average radon concentration measured by the scientists was 5.0 pCi/L in winter and 3.6 pCi/L in the spring (22). The average value of 4.3 pCi/L is slightly above the EPA recommended guideline 4 pCi/L. EPA representatives also studied radon in several homes. Their measurements ranged from 0.4 to 1.6 pCi/L in the winter and 0.2 to 0.6 pCi/L in the summer (92). These values are below the EPA guideline (90). Monticello remediation studies have shown that elevated indoor radon levels are more likely to occur if contaminated mortar is used for such indoor applications as constructing fireplace mantels. These applications can be corrected by either replacing the affected mortar or applying barrier sealants to retard radon penetration. A thorough radioactive survey before beginning such efforts can help scientists set priorities and determine the most appropriate response measures.
The operating mill released both radioactive and chemical effluents through the roaster stack, but it is the chemicals that would cause the greatest effects in animals and vegetation. Animals were exposed by drinking contaminated water and grazing on soil contaminated by airborne deposition and irrigation water. The radioactive material measured in those waters in recent years has been observed to exceed the state of Utah standards as far as 2 to 3 miles downstream of the property (31). Even higher levels existed during mill operations. However, cattle were known to be watered from springs whose concentrations were lower than those found in the river water. The radiation exposure is not expected to have been life threatening to either animals or plants, but the chemical effects could have been more pronounced. The chemicals include the yellow cake and black cake oxides of uranium and vanadium as well as sulfuric and hydrochloric processing acids. Uranium and vanadium are chemically toxic. In humans, uranium affects the kidney and vanadium irritates the intestines. Cattle may be affected similarly, with the magnitude depending on the intake. Fortunately, this pathway is not likely to affect human health because uranium is poorly transferred from cattle forage to the meat humans eat (93). The plant damage reported by the local population could have been from the processing acids. Sufficient exposure to sulfuric and hydrochloric acids causes plant browning and death. These acids also corrode metals and could have caused vehicle bumpers, fences, and screen doors to rust.
Some individuals are known to grow home vegetable gardens in soil contaminated with tailings. Three pathways exist for eating crops contaminated with radioactive material, but the tailings pile-soil-food crops pathway seems to be the most important. In that pathway, an individual has used tailings to fill a home garden. We can check samples of vegetables grown in that soil to see how readily the plants have absorbed radioactive materials. Then we can estimate the dose (12).
Areas where people work or live that are contaminated with radioactive ore or tailings should receive high priorities for remediation. The occupants of those areas should prudently keep their radiation exposures as low as reasonably achievable. Adequate ventilation of the building they occupy is one good way to do that. Residential properties and commercial areas, including the three ore storage sites, are now being remediated to bring them into compliance with standards for public health protection. Radioactive surveys are performed after each site is remediated. Where there is reason to believe that a property has been recontaminated through dusting from other properties, an evaluation is in order. Once workers complete remediation of the vicinity properties, the tailings piles will be moved. Performing an overall survey after all remediation is complete will determine whether the entire job is satisfactory. If it is, the public health risk should be insignificant.
Specific Health Outcomes Concerns
Based upon the available environmental sampling data that ATSDR staff reviewed concerning the Monticello Mill Tailings Site, there is no indication that the chemical contaminants are at levels that would result in adverse health effects. It is apparent from community responses that in the past children swam in the tailings ponds. However, ATSDR scientists do not have any environmental sampling data from those ponds; therefore, it is impossible to determine the concentrations of arsenic, molybdenum, selenium, and vanadium to which the children were exposed. One must come in direct contact with the tailings ponds (e.g., swimming) to have exposure. If one lived near the pond, but never swam in the water, or if they did swim in the pond, but never swallowed any of the water, the contaminants in the pond could not have caused their illnesses. See the Toxicological Evaluation subsection of the Public Health Implications section of this public health assessment for a discussion of possible adverse health effects from the chemicals mentioned above.
There is no known association between radiation and heart disease, Crohn disease, Parkinson disease, or neurofibromatosis. Miscarriages, stillbirths, birth defects, and mental retardation were all observed in survivors of the atomic bomb incident, but the levels of radiation were several orders of magnitude more than levels detected in and around Monticello. Infertility is considered to be a high-dose effect, not likely related to low-dose gamma radiation from environmental sources. Loss of coordination, tremors, dizziness, and blackouts are symptoms of high doses of radiation over a short period, followed by death a few hours to a day after exposure. Digestive tract problems would result from similar high doses over a short period of time, although death may not occur for several days or weeks.
Diabetes has not been shown to be related to radiation exposure. Eye disease, vision problems, slow healing of cuts, and frequent infections are symptoms of diabetes. Without specific medical diagnosis, it is not possible to determine whether lumps, growths, and moles are results of radiation exposure.
Thyroid disease is related primarily to iodine 131 exposure. Thyroid problems should not result from exposure to contamination generated at the Monticello Mill Tailings Site.
Respiratory problems, emphysema, pneumoconiosis, and sinusitis could be related to past or current activities at the mill site. At the time the mill was in operation, conditions inside it were most likely dusty, and workers were not required to wear respiratory protection. Inhalation of dusts and particulates are known to interfere with breathing passages and can affect persons who are sensitive to dusty conditions. Workers performing clean-up operations today are required to adhere to the Occupational Safety and Health Administration (OSHA) regulations cited in Title 29, Code of Federal Regulations (CFR), Part 1910.120, Hazardous Waste Operations and Emergency Response. The other symptoms or conditions relate to poor hygiene (dental problems), old age (arthritis), lifestyles (headaches), or to unidentified causes (chronic fatigue syndrome).
In the Health Outcome Data Evaluation section of this public health assessment, ATSDR scientists compare the incidence of various types of cancer in San Juan County with incidence in the state of Utah. Cancer statistics for Monticello are also compared with those for Blanding. Utah has the lowest incidence of cancer among the states in the nation. Comparing city or county rates with the rest of the nation would not show a good representation of health outcomes, i.e., rates may be much lower compared to the nation but still may be elevated for the city or county. The state of Utah records the medical data in its registries by the person's place of residence and not the place of diagnosis/death.
The National Academy of Sciences Biological Effects of Ionizing Radiation (BEIR) Committee has concluded that "... exposure to natural uranium is unlikely to be a significant health risk in the population and may well have no measurable effect." Studies have been conducted on radon-222, a decay or daughter product of natural uranium, to determine the implications for the risk of lung cancer. Doctors in Sweden determined that the effects of the interaction between radon exposure and smoking regarding lung cancer exceeded additivity and more likely represented a multiplicative effect (94). However, a study conducted in the United States determined that increased radon correlates strongly with decreased lung cancer rates. Also, when smoking was accounted for, there was no effect on the regression of lung cancer rates (95). There is evident need for more studies to determine what effects smoking and uranium and its associated daughter products have on the development of various forms of cancer.
Publicly accessible waste streams from the tailings piles could include windborne tailings that deposited on off-site soil or rainwater leachate that carried contaminants to the alluvial aquifer and to Montezuma Creek downstream of the mill site. The deeper aquifer known to be tapped by private wells for household use was found to be uncontaminated by tailings leachates. During operation, leachate collected in tailings ponds in which children swam. Off-site residents used some of the tailings for construction purposes.
Of the nonradioactive substances in the soil detected in off-site soil, concentrations of beryllium, chromium, lead, and nickel are insufficient to cause adverse effects to human health.
The alluvial aquifer is not known to be used for household water. Because it could potentially be tapped for future household use, however, we evaluated this aquifer for its potential to affect the public health. Contaminants from the tailings piles (arsenic, molybdenum, nitrate, selenium, vanadium, gross alpha, radium-226, radium-228, uranium-234, and uranium-238) have leached into the shallow alluvial aquifer. Those contaminants have been detected in the shallow aquifer at concentrations exceeding comparison values. However, direct human contact with groundwater from the shallow aquifer, resulting in a completed exposure pathway, appears unlikely for two reasons. First, the shallow aquifer is not presently used as a source of potable water and is unlikely to be used in the future as a public water supply because of the unreliable well yield and limited saturated thickness. Residents in the area downgradient of the mill site currently obtain their water from the Monticello public water supply, which uses uncontaminated, topographically upgradient surface water sources. Second, the extent of the aquifer, which is physically confined to the narrow boundaries of the Montezuma Creek alluvial gravels, is limited. The aquifer downgradient of the mill site is estimated to be no more than 500 feet wide, and the contamination plume extends no more than a mile downgradient before it discharges into the creek. The plume has, therefore, reached its maximum dimensions. To prevent use of the contaminated alluvial aquifer as a source of potable water, institutional controls (establishing local ordinances that prevent the installation of wells screened in the contaminated alluvial aquifer) are effective in ensuring that the aquifer is not used during the time required for restoration. Where produce was grown in soil irrigated by Montezuma Creek, the selenium in the creek might have added to the natural selenium content of the produce. If people eat large quantities of that produce, they might lose hair and their fingernails or toenails might crack or fall off.
ATSDR representatives are reviewing data on the quantity of radon and radium to which residents are being exposed because of the use of tailings in construction materials. When these reviews are completed, it will be possible to evaluate whether the exposure is sufficient to affect the residents' health.
Representatives of the Department of Energy Grand Junction Projects Office (DOE-GJPO) have no plans to relocate or buy out any property owners. Proper safety procedures such as dust control and continuous radioactive air particulate monitoring during removal operations should ensure the safety of nearby residents.
Tailings removal from the mill site will be continuously monitored to ensure that off-site releases of radioparticulates do not exceed required standards. Dust control measures will be employed as they have been at other mill tailings sites to prevent the spread of radioparticulates.
It is unlikely that remediation of a vicinity property will contaminate an adjoining property unless large volumes and high concentrations of material are involved. Successful remediation will limit the concentration of radium-226 in the top 15 centimeters (cm) of soil to 5 pCi/g above the natural level of radium in that soil. Preliminary indications are that concentrations for many properties will be well below that level. In order for a property to be recontaminated, a sufficient thickness and concentration of dust would have to be deposited. For example, assume that the soil concentration at a newly remediated property is 4 pCi/g, concentration at the adjacent contaminated property is 10 pCi/g, and the natural background concentration is 1 pCi/g. The thickness of dust required to recontaminate the clean property would be about 5 cm. If the contaminated property is at 100 pCi/g, the dust layer will have to be 0.3 cm thick. Higher concentrations require thinner dust layers. Because of this relationship, it might be necessary to consider dust control measures when decontaminating highly contaminated properties where thin layers of dust could recontaminate adjacent properties. An integral part of any soil remedial action includes extensive dust control.
Possible corrective actions include partial rebuilding, ventilation, and masking. Mortar, bricks, and blocks made from mill tailings can increase the radiation level as well as the radon air concentration inside the building. If the radiation levels are too high, the only course is to remove the affected material and rebuild the part of the building containing the contaminated material. If the radon air concentration is too high, there are two options, ventilation and masking. Ventilation of the living spaces, or the basement or attic that feeds radon to the living spaces, will direct the radon out of the building. There are several ways to accomplish the ventilation: open windows; add a static precipitator to the ventilation system; or force ventilate the rooms, basement, or attic with mechanical devices. Also, if the contaminated mortar is accessible from the occupied side, as in a fireplace mantel, painting it with a heavy epoxy-type coating can reduce the radon emissions and air concentration. Before such efforts are started, there should be a clear understanding of how much each option can cost and how likely it is to improve the condition.
Monticello and area residents with questions or concerns about their property and radioactive materials can contact the DOE-GJPO at the following toll-free telephone number: 1-800-269-7145. Residents can also contact DOE in Monticello at (801) 587-4000.
Vicinity property remediation plans were designed to clean up the most heavily contaminated properties first. A city block concept provided for grouping properties into procurement packages that would be the most conservative of remediation funds. DOE representatives said socioeconomic status was never a consideration.
Some properties have been remediated a second or even a third time because of the discovery of additional contaminants or because the property failed to meet air quality requirements. Other vicinity property projects have experienced similar secondary or tertiary remediations because not all materials that can contribute to interior air quality were discovered initially. In fact, at the levels the DOE must achieve, natural contributions from certain rock units can create additional remediation requirements.
Asbestos was used as an insulating medium in mill buildings, pipe cladding, and vinyl asbestos tile. Similar composite materials were being used for residential, commercial, and industrial purposes throughout the country at the time the mill site was operational. Unneeded or unwanted asbestos-containing materials may certainly have gone to the local landfill.
Asbestos is the name for several minerals that occur in nature in the form of fibers. Because they are heat- and fire-resistant, they have long been used in building materials, friction-reducing products, and heat-resistant fabrics. Fibers can break away from natural asbestos (e.g., during mining operations) or from products containing asbestos (e.g., as they are manufactured). Fiber fragments that become airborne can be inhaled. The healthy human lung is able to remove very short asbestos fiber fragments after the fibers are inhaled. However, the longer fiber fragments cannot be easily removed from the lungs, and some of the shorter fibers are poorly removed by lungs that have been damaged (e.g., by smoking cigarettes). Large numbers of fibers retained in the body for many years could lead to adverse health effects.
The very low concentrations of these fibers normally present in indoor or outdoor ambient air have not been shown to be harmful to health. Brief one-time exposures to low or moderate fiber concentrations have not been shown to cause harm. Adverse health effects such as cancer and asbestosis have appeared in people, especially smokers, occupationally exposed to high fiber concentrations. However, the demolition of mill site facilities and the disposal of the demolition debris in a properly managed landfill are not expected to result in significant amounts of exposure. People who are concerned that they may have been harmed by exposures to asbestos can ask their physicians for chest Xrays. They and their physicians can learn more about the health effects of asbestos from ATSDR's Toxicological Profile for Asbestos (Update, 1994) and from ATSDR's Case Studies in Environmental Medicine: Asbestos.
We do not have specific information on the disposition of all the buildings, tubing, metal sheeting, and metal framework components from the mill site. Building components were rumored to have gone to the state prison. A field examination performed by DOE-GJPO project personnel did not confirm the presence of such materials at the prison. We do not know the disposition of tanks from the mill site. DOE representatives say no evidence exists that the materials mentioned above are radioactively contaminated.
Concerns were expressed about the granary. The granary is a privately owned site where six silos once stored seeds of beans, corn, wheat, and other crops for farmers. It may also have been an ore storage or ore truck cleaning site. It is west of the mill site across Utah State Road 191. This site was difficult to assess due to limited access and the presence of contamination beneath concrete pads and large silos.
The first radioactive assessment began in March 1989, and the site (granary) was added to the DOE remediation list that year. The site was scanned to identify areas exceeding the area background of 17 microroentgen per hour (µR/hr) plus 30%. Surface contamination was found around the perimeters of five silos and two concrete pads and in a few other small areas. The owner at the time did not allow cores to be taken through the concrete floors of the silos, so investigators used a borehole logger to measure the contamination depth around the silo perimeters. They assumed a uniform depth of contamination. The surveys of the largest slab found hot spots across the slab and an elevated reading on contact with one of the slab's steel reinforcing tubes where the slab's concrete covering had broken away. The hot spots indicated that the slab contains some ore rocks and the tubing is contaminated; however, borehole logging of some of those tubes did not identify any contamination. The tubes may have come from the mill site. Negotiations with the owner will determine the fate of this contamination. Negotiations with the granary's property owner were completed in 1996. The site has been included in the Monticello Vicinity Properties Remedial Action Program. See Appendix D of this document for more details about radioactive surveys and response actions at the granary.
ATSDR and National Air and Radiation Environmental Laboratory (NAREL) staff members reviewed DOE engineering design documents.
The City of Monticello owns the nine-hole public golf course. The course is southwest of the mill site across Utah State Road 191. The surveys indicated that the mill tailings had been used as fill and top dressing, and 40 areas were found that exceeded the Monticello background of 14.6 µR/hr plus 30%. Elevated soil concentrations existed from 6-inch to 66-inch depths, with the average being 11 inches. Cleanup involved removing approximately 27,000 cubic feet of tailings over 30,000 square feet of land, plus any overlying asphalt roadway.
The contaminated sites were included in the remediation schedule in March 1992. Excavation began in July 1994 and is now complete, and backfilling with clean soil is under way. See Appendix D of this document for more details about radioactive surveys and response actions at the golf course.
ATSDR and NAREL staff members reviewed DOE post-construction radioactive as-built drawings.
The cemetery is the main burial ground for the town and is north and northeast of the mill site. Radiation levels in 6 areas exceeded the Monticello background of 14.6 µR/hr plus 30%. Remediation involved removing approximately 20,000 cubic feet of soil in layers ranging from 4 to 24 inches over 33,000 square feet of land.
This site was included on the remediation list in October 1991. Phase I of the remediation construction started in May 1993 and ended in June 1993. Phase II was included in September 1993, the plan was approved in August 1995, and remediation construction was completed on June 19, 1996. See Appendix D of this document for more details about radioactive surveys and response actions at the cemetery.
Wells screened in the upper aquifer, especially wells in areas contiguous to the mill site and the old ore-buying stations, could be contaminated. Wells on the mill site are contaminated. Wells distant from the old ore-buying areas, Montezuma Creek Canyon, and the mill site are screened in the lower aquifer and are not associated hydrologically with the mill site activities. Therefore, we do not suspect that they are contaminated.
Rainwater leachate carried contaminants to the alluvial aquifer and to Montezuma Creek downstream of the mill site. The deeper aquifer known to be tapped by private wells for household use was found not to be contaminated by tailings leachates.
The alluvial aquifer is not known to be used for household water. However, because it could potentially be tapped for future household use, this aquifer was evaluated for its potential to affect the public health. ATSDR scientists found that concentrations of arsenic and selenium in the aquifer were insufficient in themselves to cause harm.
Selenium in Montezuma Creek might have increased the natural selenium content of the produce grown in soil irrigated by water from the creek. If people ate very large quantities of that produce for many years while drinking only the water from the alluvial aquifer, they might have some hair thinning and cracking or splitting of their fingernails or toenails. If the aquifer became some people's sole source of drinking water and they also ate large quantities of homegrown produce irrigated by water taken from Montezuma Creek downstream of the mill site, molybdenum could cause gout-like illness. Contaminants in the produce would not be expected to cause harm in individuals drinking water from the deeper aquifer.
The purpose of the Operable Unit (OU) III study was to collect sufficient information and data to characterize the nature and extent of environmental contamination in OU III, identify the sources of contamination, assess changes in contamination patterns over time once on-site sources (tailings piles) have been removed, and to calculate the levels of risk to human health and the environment from the contaminants associated with OU III. The OU III soil and sediment area, which is located entirely on private land, begins approximately 0.5 miles east of the eastern mill site boundary and extends downstream approximately 14,100 feet. The area is currently used for cattle grazing and recreational purposes; no residences are located within the OU III soil and sediment study area. Soil and sediment characterization began in 1994 and continued through September 1996. The primary source of soil and sediment contamination in the OU III soil and sediment study area is the mill site. Montezuma Creek, which flows through the tailings piles on the mill site, has been the primary transport mechanism for soils and sediments. The OU III Remedial Investigation draft report is currently under DOE review.
The initial findings of the OU III Remedial Investigation indicate that the alluvial aquifer contaminant concentrations decrease with increasing distance from the mill site, eventually matching natural background concentrations. The distances vary from 7,000 feet downgradient (east) of the mill site boundary for uranium, the most mobile site contaminant, to no further than the downgradient mill site boundary for radium-226, the most immobile site contaminant. The OU III Remedial Investigation report, currently under DOE review, will discuss contaminant plumes in detail as well as present final conclusions about future exposure scenarios.
Low levels of radon gas may be emitted from a permanent tailings repository; however, the repository is designed to make the release rates much lower so they will meet certain regulatory specifications in CFR 40.61 Subpart Q, National Emission Standard for Radon Emissions from the Disposal of Uranium Mill Tailings. According to this regulation, radon-222 emissions to the ambient air from uranium mill tailings piles that are no longer operational shall not exceed 20 picocuries per square meter second (pCi/m2s). This is much lower than the levels of radon-222 currently released from tailings piles in Monticello, which range from 100 to 700 pCi/m2s.
General construction and the disturbance of soils during removal actions can cause new hazards and intensify existing ones. Exposure to radiation and dusts is among the hazards. Remedial actions create greater need for short-term protection of workers and residents from these hazards.
ATSDR staff members are making every effort to ensure that former residents of Monticello and the surrounding area are contacted. We have developed a site-specific mailing list of around 2,000 names. Approximately 25% of the individuals on the mailing list are former residents of Monticello and the area. These individuals have been contacted and given the opportunity to express their public health concerns and questions.
ATSDR staff members have heard from several of these former residents. We have sent public health information and literature packets to those individuals expressing further interest. We will continue to inform current and former residents of Monticello and the area of ongoing ATSDR activities.
If anyone reading this document has information on individuals who would like to be added to the mailing list, please provide names and addresses to the following office:
We can evaluate any dose calculations that have been performed for utility workers to see if the calculations are reasonable. Those dose calculations would have factored actual data and assumptions into a model. If there is need for reevaluation, we should review the original data, assumptions made, and mathematical formulas used.
The properties containing sand from Dry Valley have been classified as disputed properties. The disputed properties that exceed the applicable standards for cleanup will be remediated as part of the Monticello project. The only difference between vicinity properties and disputed properties is the source of the radioactive materials (e.g., Monticello Mill Tailings Site, Dry Valley). ATSDR staff members do not have detailed information on the operations at Dry Valley.
Mill worker public health concerns should be referred to NIOSH, which has staff members who
conduct research on the health effects of exposures in the work environment. ATSDR
representatives will ensure that NIOSH researchers are aware of mill workers' public health
concerns.
ATSDR scientists will continue to review any future community health concerns that become available. Should additional information become available that alters the findings of this public health assessment or addresses issues described herein, this public health assessment will be modified as needed.
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