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A. Toxicological Evaluation

Substances released into the environment do not always result in human exposure. Humanexposure to a nonradioactive chemical contaminant can occur only if humans come in contactwith the chemical contaminant either by ingestion (eating or drinking a substance containing thechemical), inhalation (breathing air containing the chemical), or dermal absorption (skin contactwith a substance containing the chemical). In the case of radioactive substances, humanexposure 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 chemicalcontaminant may cause, we must consider several factors related to an exposed individual'sinteraction with the chemical. Such factors include the amount or dose of the chemical to whicha person is exposed, frequency and duration of exposure, route of the chemical's entry into thebody (ingestion, inhalation, or dermal absorption), and the multiplicity of exposure (combinationof 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 fromthe body).

To determine the possible health effects specific chemicals can produce, ATSDR representativesconsider those physical and biological factors as well as a variety of informational sources, suchas scientific literature, research reports, and reports from other agencies.

The following sections evaluate the potential health effects from exposure to contaminants fromthe Monticello Mill Tailings Site. The toxicological evaluation for each contaminant assessesprobable health effects from exposure to the contaminant. These health effects relate tocontaminant concentration, exposure route, exposure frequency, and population potentiallyexposed. Populations known to be or suspected of being sensitive to exposure to thecontaminant are included. The information is presented for those pathways identified ascompleted exposure pathways for on-site and off-site surface soils and ambient air and forpotential exposure pathways involving groundwater, surface water, and bioaccumulation ofcontaminants in the food chain.

A.1 Radioactive Contaminants

    a. Radon-222

    Although ATSDR representatives have not yet completed their review and analysis ofthe data needed to estimate the risk to health from all radon-222 exposures, bothindoors and outdoors, adverse health effects from exposure of the public to this gasoutdoors in the vicinity of the mill site are highly unlikely. Two considerations ledATSDR 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 adequatelyprotective against lung cancer from continuous long-term indoor exposure (49).

    2. Outdoor exposure to radon in general is much less hazardous than indoor exposurebecause radon-222 gas itself is not directly capable of causing human lung cancer. Anyradon-associated carcinogenic effects are from the radon daughters (products of theradioactive 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 areconfined along with the parent gas, that could present a health hazard if radon-222activities are elevated. Some of the foundations of the structures on MonticelloVicinity Properties were poured from concrete containing material from the tailingspiles (3). This material contains radium-226, which decays radioactively to radon-222. The radon daughters that would accumulate in these structures would be confinedalong with the radon-222 gas. In the record of decision for the Monticello VicinityProperties, Department of Energy (DOE) representatives estimated average lung dosesfor 15 Monticello Vicinity (indoor and outdoor) Properties, indicating that DOE hasindoor concentration data (3). Moreover, DOE reportedly has indoor radon-222 datafor more than 1,000 vicinity properties. Staff members at ATSDR are scheduled tobegin 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 ofdata provided by DOE as well as the financial funding provided by DOE. Appendix Cof this document contains other information about radon-222.

    b. Radium-226

    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 followingscenario: persons playing outside 5 days per week for 1 hour per day. The route ofexposure is via incidental soil ingestion (100 mgsoil/day).

    The dose calculated using the assumptions described above for the averageconcentration is 0.05 millirem per year (mrem/yr) and for the maximum is 14.40mrem/yr. Both doses include the radiation dose contributed by radium-226 naturally inthe soil, and both are below the recommended dose limit of 100 mrem/yr (50). Inaddition, there is no apparent risk of increased cancer and no apparent health hazarddue 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 watersources known to supply drinking water. However, the uranium content of the alluvialaquifer, which could potentially be tapped for drinking water in the future, could causekidney 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 forits soluble forms) is greater than that posed by its radioactive properties (51). Drinkingwater used by residents near the mill site is either supplied by the city from surfacewater taken upstream of the mill site or taken from wells that tap the Burro CanyonAquifer. These water sources have not exceeded activities of 30 to 43.5 pCi/L foruranium (43 to 62 µg uranium/L) (42, 51). The range of concentrations in water takenfrom city water upstream of the mill site or the Burro Canyon Aquifer is unlikely toresult in kidney damage to children or adults from the chemical toxicity of uranium,nor would it pose a significantly increased likelihood of cancer from uraniumradioactivity (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). Nowells are known to draw from this aquifer. However, it is possible that some wellsmight do so now or in the future in the absence of institutional controls, such asordinances to prevent screening this aquifer. Children and adults who drink this waterin the future would be at risk for kidney injury. If people use this water in the future astheir 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

    a. Beryllium

    The concentration of beryllium in soil (1 part per million [ppm]) is insufficient to causecancer or noncancer health effects through soil ingestion (37, 53). No significantadverse effects were produced in any of the studies in which animals were orallyexposed to greater amounts than humans could be assumed, by the most conservativescenarios, to ingest from this soil (52, 53). Beryllium is known to cause lung cancer inhumans and animals exposed by inhalation, although not all beryllium is capable ofproducing lung cancer. Very specific forms of beryllium oxides have the provenpotential, but other forms are relatively inert. However, calculations described inAppendix C established the fact that windborne soil would not contain enoughberyllium to present a significantly increased risk of cancer by inhalation. Theconcentration of beryllium in off-site soils is well within the range of beryllium soilconcentrations reported for the United States in general and for Utah soils andsediments in particular (37, 54). Bioconcentration of soil beryllium by locally grownproduce or grazing animals is not expected to generate dietary beryllium intake greater than would normally exist.

    b. Chromium

    The 22 ppm chromium maximally present in off-site soil and sediment samples is wellwithin the soil chromium concentration range found in the state of Utah and is not athreat to the public's health (37, 52, 54). Environmental chromium occurs primarily intwo chemical states: chromium-III (Cr-III) and chromium-VI (Cr-VI). Cr-III, which isenvironmentally very stable, is nutritionally essential for health and not harmful at soilconcentrations 100 times that maximally reported (52). Even if all the chromiumoriginally released to the soil were Cr-VI, which is much more toxic, especially ifinhaled, it would be readily converted to Cr-III (55, 56, 57). The concentration ofchromium in the soil (22 ppm) off site could be of concern to children who play in anddaily ingest large quantities of the soil only in the highly unlikely event that nearly allthe chromium had persisted in the environment as Cr-VI for the 30 years since the millclosed. We did not analyze air for respirable chromium in either oxidation state, butusing 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 asignificant risk of cancer through inhalation (52).

    The off-site soil concentration reported is well within the range of chromium soilconcentrations reported for the United States in general and for Utah soils andsediments in particular (37, 54). We believe that even persons whose entire dietconsists of homegrown items will take in chromium within the general range ingestedwithin the United States -- 0.025-224 mg/day -- an intake level not expected to produce adverse effects (58).

    c. Lead

    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 threatto human health (59). The concentration of lead in off-site soils is well within therange of lead soil concentrations reported for the United States in general and for Utahsoils and sediments in particular (37, 54). Bioconcentration of soil lead by locallygrown produce or grazing animals is not expected to generate dietary lead intakegreater than would normally be the case. For more details about adverse health effectsthat might be seen in children residing where soil lead concentration was reported at higher levels than found adjacent to Monticello, see Appendix C.

    d. Nickel

    No adverse effects are anticipated from the reported concentrations of nickel in off-sitesoil (37, 52). The absence of nickel at levels of concern in groundwater or surfacewater suggests that the soil nickel is in a poorly soluble form and likely to be poorlyabsorbed if ingested. Moreover, nickel was present in off-site soil at 16.2 ppm, aconcentration well within the natural background of Utah soils and alluvial sediments(37, 54). Bioconcentration of soil nickel by locally grown produce or grazing animalsis not expected to generate dietary nickel intake greater than would normally be the case.

    e. Thallium

    Thallium might be present in off-site soil at concentrations above 0.2 ppm and mighttherefore be sufficient to cause adverse health effects in children who exhibit picabehavior -- 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 quantitationlimit of 2 ppm in off-site soil (37). The concentration of thallium normally occurringin Utah soil is not known (54). Thallium is absorbed by plants from soil and enters thefood 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 inlocally grown produce to evaluate the potential for adverse health effects from eatingfood grown in residents' backyards. For information about the toxicity of thallium, see Appendix C.

A.3 Nonradioactive Contaminants in Groundwater

    a. Arsenic

    The arsenic present in known drinking water sources is insufficient to cause adversehealth effects, and there is little likelihood that the arsenic in one potential futuresource of drinking water (future wells that may draw from the alluvial aquifer) couldcause health problems (see Appendix C). The average United States diet suppliesabout 50 µg arsenic each day, much of it because of arsenical pesticides, a more likelysource 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. Dermalexposure 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 likelihoodof 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 exceededthe level of 48,000 µg/L (48 ppm) reported in groundwater in some western miningareas (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 thewater could swallow 50 ml (1-2 tablespoons) of water each swim. Repeated splashingand dunking could lead to ingestion of several times that amount on a single warmafternoon, with the child ingesting as much as 10 mg arsenic (1 mg/kg/day), if thewater at the tailings pond was contaminated to that extent. ATSDR scientists foundreports that 1 to 2 mg/kg/day of inorganic arsenic from contaminated water resulted innausea and vomiting, followed by severe abdominal pain, bleeding in the digestivetract, and in some cases, death by renal failure (62). Children who had no acuteadverse effects after swimming in the ponds on several occasions or who stoppedswimming 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 incurrent drinking water, if ingested daily over many years, could cause the chronicarsenic poisoning (blackfoot disease, symptoms similar to Raynaud syndrome, andcancers of the skin, liver, and lung). For additional information, see Appendix C.

    b. Molybdenum

    Molybdenum was not present at levels of health concern in known drinking watersources or in off-site soil (37). However, if in the future some off-site residents drawdrinking water from the alluvial aquifer and at the same time derive a substantialproportion of their food from homegrown produce, they could be at risk for gout-likeillnesses (52). Up to 213 parts per billion (ppb) molybdenum was present in thealluvial aquifer downgradient of the mill site, and up to 340 ppb molybdenum waspresent in surface water used for irrigation downstream of the mill site (1, 42). Plantsmay bioconcentrate molybdenum from the irrigation water so that their molybdenumcontent is increased by five times the molybdenum content in the soil in which theygrow (63). Data on the molybdenum content of grains, fruits, and vegetables grown onproperties near the Monticello Mill Tailings Site are not available. Therefore, ATSDRscientists are not able to determine whether total molybdenum intake levels aresufficient 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 ppbmolybdenum (42). During operations and in the decades immediately following,Montezuma Creek molybdenum concentrations may have reached higher values than3,420 ppb. It is possible to speculate that similar concentrations of molybdenum werepresent in the tailings ponds when the facility was in operation. If children swam in theponds often over many years, they could have ingested enough molybdenum to haveinterfered with their ability to use dietary copper and put them at risk for hypochromicmicrocytic anemia (52).

    c. Nitrate

    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 thealluvial aquifer downgradient of the mill site (33 ppm), their newborn infants could be10 times more likely than those drinking water from the alluvial aquifer upgradient ofthe 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 theirblood (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, aremore readily contaminated by bacteria than are deeper wells, such as those that drawfrom the Burro Canyon Aquifer. The stomach juices in newborns, especially those 3months 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 convertingested nitrate to nitrite. Because of the lower acidity in the infant's stomach, theconversion 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 infantsdrink water containing more than 10 ppm nitrate (52).

    Nitrates are used to fertilize soils to improve plant growth. The effectiveness of thispractice stems from plant metabolism of inorganic nitrate to precursors of plantproteins. 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.

    d. Selenium

    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 ofSciences recommends adults consume 55 to 75 µg selenium per day to preventdeficiency (64). If the intake from food and water is as low as 7 to 11 µg/day, thedeficiency causes adverse effects to cartilage tissue and the heart (65). These effectscan be treated with supplements of 230 to 920 µg/day (65). The mean United Statesdaily intake is 83 to 129 µg/day (64). Ingestion ranging from 240 to 1,510 µg seleniumper day, an amount that could require drinking 4 gallons of off-site alluvialgroundwater daily (should future wells tap this aquifer) does not produce harmfuleffects (1, 42, 65). However, excessive selenium intake can cause adverse healtheffects; continuous total intake of 3,200 to 6,690 µg selenium per day has causeddamage 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 Creekselenium concentrations may have reached higher values than 3,110 ppb. It is possibleto speculate that similar concentrations of selenium were present in the tailings pondswhen the facility was in operation. Children who swam often in the tailings ponds formany years could have been at risk.

    Moreover, Utah is one of the states known to have highly seleniferous soils and plantsthat can cause ingestion of amounts of selenium that could be of health concern (65). Itis possible that use of irrigation water drawn from the alluvial aquifer could increasethe potential for adverse health effects from naturally occurring selenium in produceand meats from Utah.

    e. Vanadium

    Vanadium has not been associated with cancer in people or animals by any route ofexposure (66). The substance was not reported in sufficient concentration for acuteexposure to gusts of wind to cause bouts of coughing and other signs of respiratoryirritation to on-site workers or off-site residents (1, 37, 66). Should the highestreported on-site concentration occur frequently off site, however, persons with asthmaand others with chronic respiratory problems might experience increased symptoms(66). Adverse effects to workers from prolonged exposure are not anticipated becausethe highest on-site concentration reported is below the threshold limit value required bythe Occupational Safety and Health Act (67).

    Vanadium has not been identified at levels of health concern in known drinking watersources (37). The likelihood of kidney damage to people who might in the future havewells that tap the alluvial aquifer or to children who frequently swam in the tailingsponds for many years is unclear (1, 66). Contamination of foodstuff is more likely toresult from adhesion of vanadium-containing fertilizers than from bio-uptake ofcontaminated 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 withmoisture could have resulted in an increase in respiratory diseases among nonsmokersdepending on the concentrations that were present in the ambient air, although it is notclear whether the adverse effects might have persisted to the present. Thesesubstances, in unknown concentrations, were probably responsible for the sulfur odorand damage to clothing and automobile chrome trim noted by off-site residents whenthe plant was operating (see the Community Health Concerns sections). At that time(1960 or earlier), the ambient air concentration of these substances exceeded the odorthreshold for sulfur oxides (0.007 to 0.03 ppm) by an undocumented quantity whichwas, however, sufficient to cause the damage described earlier (68). Concentrations ofsulfur dioxide as low as 0.04 ppm have been associated with chronic obstructive lungdisease in nonsmokers (69). The study reporting this association did not examine thepersistence of respiratory injury. However, another study reported decreased mortalitydue to chronic bronchitis that lagged about 4 years behind improvement in air qualityresulting from pollution controls designed to lower ambient sulfur oxide concentration(70). These two unknown quantities (the concentration of sulfur oxides present duringmill operation and the persistence of injuries that might have resulted from exposure atthat time) add considerable uncertainty to the possibility of predicting the likelihoodthat 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 ofhealth outcome data for the Monticello area. In response to the large number of health concernsvoiced by former workers at the Monticello Mill Tailings Site, they conducted a search ofavailable literature on studies of uranium mine and mill workers. A few of the studiesmentioned the Monticello mill with respect to industrial hygiene surveys. ATSDR staffmembers were able to determine from those studies what the conditions were like in and aroundthe mill and whether the types of diseases present in the mill workers were also present in thecommunity surrounding the mill.

Worker Issues

Representatives of the occupational health program of the U.S. Public Health Service performedenvironmental surveys in many uranium mills in the western United States, including the AtomicEnergy Commission (AEC) mill in Monticello, during the 1950's. Workers in most of the millswhere industrial hygiene surveys were done experienced a chronic irritation of the upperrespiratory 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 andteeth, 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 usualpulmonary fibrosis compared with 7.5% in the control group. Twenty percent of the Indianmillers 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 participantsfrom 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 diedbetween 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 tissueother 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 ofapproximately 215 workers at the Monticello Ore Concentrating Plant in 1957 to determine thelevels of radioactive dust exposures workers were experiencing. The study revealed that therewas no effective dust control equipment throughout the plant. It also showed that 86 employeesout of the total plant population were exposed to average dust concentrations above themaximum allowable concentration (MAC). Nineteen of those were exposed to greater than fivetimes 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 showedthat workers in the mill experienced no hazard from external radiation (beta plus gamma orgamma only) (73). According to the survey, there had been a urine sampling and assayingprogram in place since 1956. All plant personnel were included in the program, and thoseworkers in areas having higher air dust levels were sampled weekly. ATSDR scientists have notbeen 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 hadworked at one or more of seven mills in the Colorado Plateau region. The study sought todetermine the possible relationship between exposure(s) to uranium, thorium, and radium andthe development of malignant and nonmalignant diseases. The risk of mortality among theuranium mill worker cohort was analyzed from 1940 to 1977. Results from the study showed nostatistically significant excesses of any malignancies. However, although not statisticallysignificant, there was an excess of chronic renal disease. There was also a significantly elevatedstandard mortality ratio (SMR) because of nonmalignant respiratory disease. Analysis of thestudy determined that the elevated ratio was caused by emphysema, fibrosis, silicosis, andchronic obstructive pulmonary disease (74). The study revealed that, in those workers who hadworked 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 associationbetween lung cancer and working in uranium mills. There were no subcohorts identified andmost likely there are none that exist.

ATSDR representatives have used this information as background as we looked for similaradverse health effects in the community of Monticello. It appears that the green and yellowcoating of the mouths and on the tongues of the workers were acute, short-term effects andconsequently would not be listed in any type of health-related database. ATSDR staff membersdid 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 has been a reportable disease in Utah since 1948, but there was not a statewidepopulation-based registry until 1966. The Utah Cancer Registry is part of the National CancerInstitute's Surveillance, Epidemiology, and End Results (SEER) program. Utah has the lowestoverall cancer incidence in the SEER system and the lowest overall cancer mortality rate of anystate. The main reason seems to be the low smoking rates and the associated low rates ofsmoking-related cancers. Since becoming part of the SEER system, Utah has had an incidencerate approximately 16% below national rates, and mortality rates are approximately 28% belowthe national average. As of September 1992, Utah males have a lifetime risk of developingcancer 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-yearincrements. Incidence rates are the number of new cases of disease in a population over a periodof time. The incidence rates measure the probability that healthy people will develop a diseaseduring a specified period of time. (The numbers for some years were so small that comparisonswould not have been statistically significant with less than a 10-year increment.) The UtahCancer Registry also provided statistical tables summarizing cancer incidence in Monticello andBlanding residents diagnosed between 1967 and 1992. For most of the analyses of cancer, thepopulation exposed was assumed to be the entire population of Monticello, primarily because thedocumented radioactive hazards were quite widespread in the community, and there were severalpotential pathways for exposure. Table 14 shows the number of cancer incidence cases forMonticello 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, butthese data are not adjusted for different proportions of the population of different ethnic orreligious origins; however, they are age-adjusted. The sites and cancer types reviewed includedthe 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 thestate of Utah. Cancer of the cervix is the only type of cancer whose rate is significantly elevatedin San Juan County as compared with rates for the state of Utah. This type of cancer would notbe associated with the contaminants present at the mill site.

ATSDR representatives searched the CDC Wide-Ranging Online Data for EpidemiologicResearch (WONDER) database for incidents of malignant neoplasms of the respiratory andintrathoracic organs in San Juan County and compared the age-adjusted rates with the state ofUtah rates. Intrathoracic organs include the larynx, trachea, bronchus, and lung. The whitepopulation rate in the county was 39.9, while the state rate was 24.6 (76). Rates for all otherraces were below the state age-adjusted rate.

ATSDR representatives reviewed EPA's Riggan's Mortality Tapes and identified two largepercentage 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 tracheabronchus lung pleura cancerous deaths (77). Tracheobronchial lymph nodes tend to be the siteof greatest concentration for inhaled uranium and thorium (71, 72). There was also a significantexcess 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 amongMormon males (78). Radiation has not been shown to be a factor in increasing the chances ofdeveloping 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 tohigh 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 approximately15% 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 solubleuranium is retained in the bone (79). Three mortality cases due to bone/jaw cancer werereported 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 inenrichment facilities, a relationship has not been observed for natural uranium which is found atthe mill site.

Cancer mortality in general and lung cancer mortality in particular were examined amongMonticello residents. Data provided by the Utah Department of Health made it possible tocompare cancer mortality among Monticello residents with rates for San Juan County and thestate of Utah. We compared Monticello residents' odds of dying of lung cancer to their odds ofdying from some other cancer with similar odds for other San Juan County residents. The riskof 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 duringthese years there was excess risk of dying of lung cancer in Monticello compared with risk for acounty (San Juan) with a low overall risk of death from this disease. When the lung cancermortality 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, (1960population: 1,845) developed acute leukemia. On the basis of the leukemia mortality rate for theUnited States in 1960, only one leukemia case in 30 years would be expected among children ina town the size of Monticello (80). A review of the childhood cancer cases for Monticellobetween 1967 to 1992 revealed only one cancer, a case of acute lymphoblastic leukemiadiagnosed in 1970 (75). The cause of the leukemia clustering is still not known. ATSDR staffmembers were told that a leaking underground gasoline storage tank, which was in the area ofthe cluster, had been removed shortly after the cases were identified (81). ATSDRrepresentatives 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 SitesMonticelloBlanding
Blood System77
Cervix Uterine58
Corpus Uterine26
Lymph Node64

Table 15.

Human Health Effects at Various Hydrogen Sulfide Concentrations in Air(75)
Cancer Type or Site 1966-1975 1981-1990
Lymphoma.532 .394
Uterine Corpus.795.823
All Sites.705.684

Damage to the kidneys seems to be the primary systemic health risk in humans from exposure tonon-enriched uranium. Statistically significant increases in deaths due to chronic andunspecified nephritis and renal sclerosis have been reported for uranium millers (74). Onenoncancerous cause of death, end-stage renal disease, was considered, based on toxicologiceffects of uranium.

We used the CDC WONDER system to review renal failure for males and females in San JuanCounty. The database covers mortality for the years 1979 to 1991. There were four cases formales, and the age-adjusted rate was equal to the average rate for all counties in Utah that hadreportable cases during the same period. There were 11 cases for females, and the age-adjustedrates were higher for San Juan County than for any other county in Utah. The age-adjusted ratefor white women was double the rate for all other races in San Juan County (76). The mapfollowing 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 renaldisease, the U.S. Renal Data System, for the National Institutes of Health. The data primarilyreflect 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 dataindicated that there were five cases of end-stage renal disease in San Juan County and 445 casesin the rest of Utah. This number does not represent a disproportionate percentage of cases ofthis disease in the county; the database does not indicate how many of the cases were inMonticello.

The rate of infant mortality in Utah has consistently been lower than rates for other parts of theUnited States (83). Studies have shown that congenitally malformed children are morefrequently born to mothers who use alcohol, drugs, or tobacco than to mothers who refrain fromusing such products. Seventy percent of the study population included members of the Churchof Jesus Christ of Latter-day Saints (Mormons), who discourage the use of alcohol, tobacco, andother drugs. However, Seegmiller and Hansen were unable to show through their research thatthe decreased use of these products had any effect on the rate of congenital malformations in thestate. Their research concerning congenital malformations in children born in Utah during theyears 1968 to 1972 shows that San Juan County had the highest rate of any county in the state ofUtah. The results show that San Juan County had the highest percentages of mothers receivinglate or infrequent prenatal care and the lowest mean level of public education (84). Interhospitalvariation 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 centralizedreporting was only established in 1992. There were no other major causes of death for whichthere 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 thisdocument.

The major problem in evaluating all the health outcome data described in this section has to dowith numbers: the small size of the Monticello population, the small numbers of health outcomesobserved, and the uncertainties about the size of the exposed population. The small number ofcases makes it difficult to calculate meaningful age-adjusted disease or mortality rates. Once therates 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 diseasebecause 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 likelyexposed population may be limited to parts of Monticello. In addition, persons exposed tocontaminants from the uranium mill may have moved away years before they developed healthproblems or died of them. These former residents will not be identified in the databases wereviewed while preparing this document.

ATSDR scientists will continue to review any future health outcome data resources that becomeavailable. Should additional information become available that alters the findings of this publichealth assessment or addresses issues described herein, this public health assessment will bemodified as needed. There are completed exposure pathways and the allegation of substantialexposure and serious diseases. Health studies need to be considered that would address the levelof current and past exposures and their relationships. ATSDR scientists plan to thoroughlyinvestigate and analyze DOE's residential/property database, which contains environmental datafor each off-site property. The completion and success of this activity is dependent on thequality and quantity of the data as well as the financial funding provided by DOE. Thecommunity's Monticello Uranium Mill Impact Survey and the leukemia study performed in the1980s both contain pertinent information. All these resources are an integral part in helpingmore clearly define exposure and disease rate and to determine what is occurring medically.

C. Community Health Concerns Evaluation

Exposure Concerns

Potential mill site-related health effects for the Monticello residents fall into two categories:

  1. Nondeterministic (the probability of the effect occurring varies with the dose withoutthreshold, e.g., heredity effects and cancer), and
  2. Deterministic (the severity of the effect varies with the dose, and there may be a threshold, e.g., cataracts and infertility) (85).

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 nondeterministicand deterministic effects. Normally, deterministic effects are associated with chemical toxicityor acute high doses of radiation exposure. On the other hand, carcinogenic effects can be relatedto radiation. Animal studies have shown that external radiation exposure advances the onset ofnaturally occurring malignancies, especially leukemia and breast cancer; internal radiationnormally 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 inradiologists and physicists with the prevalence of acute and chronic myelogenous leukemia;cases involving both irradiated Western populations and Japanese populations show similarresults. However, humans exposed to ionizing irradiation have not shown significant cases ofchronic lymphatic leukemia (87).

Workers at the Monticello Mill Tailings Site experienced situations that led to their inhalingradioactive 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 orswallowing yellow cake can induce chemical toxicity of the lung, kidney, and liver. Bothanimal and epidemiologic studies indicate that kidney failure is the most likely chemical healtheffect 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 causelung 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 developlung cancer from breathing the dust. Breathing the dust includes breathing the ore that miningtrucks dropped on the way to the mill and vehicle traffic resuspended as well as breathing thedust shaken from a miller's work clothes before washing them. Such dust is inhaled for shortintervals 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 thestudies (13).

Other people lived on the mill site during the period when the mill was operating. Depending onthe prevailing wind direction, they could have received more radiation exposure than localresidents. The exposure would have been from direct radiation from the mill site, radon gas, oredust, and the chemical and radioactive effluents. Their cancer risk would depend on theradiation 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 ceasedoperation. Based on the exposure rates from those tailings and their exposure time, their dosewas 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 adultdiseases that would be more likely to occur as a result of radiation exposure have not beenobserved.

Occupations that involve soil excavation will temporarily expose workers to elevated levels ofradon gas and its daughters. This phenomenon is normal, and these increased levels areexpected regardless of the location because radon gas escapes naturally from the earth at alltimes. The rate at which radon gas escapes is determined by the soil's uranium and thoriumcontent, its moisture level, and the prevailing temperature and pressure. The digging processloosens the soil and allows the radon gas to escape more rapidly for a time. The radon typicallydissipates quickly and the levels return to normal, causing no harm. Shallow ditches and gravescan be dug without concern for radon levels. Deep holes with small entrances will create higherand more lingering concentrations of radon and other gases because of poor ventilation. Theyshould be ventilated and certified gas free before people enter, as is standard with undergroundmines, tunnels, and storm drain systems. If the digging will unearth thick tailings on the millsite, as when wells are dug, enhanced concentrations will occur. Such processes should becontrolled by appropriately trained and equipped personnel (89).

Test wells have been bored at numerous locations throughout and beyond the mill site. Thewells are sampled periodically for identification of any migration of radioactive materials fromthe mill site. They will be maintained as sampling points to assure that remediation efforts areeffective. It is occasionally necessary to rebore a well to maintain its integrity. Reboring shouldbe 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 tailingspiles (31). The rate is 160 picocuries per square meter second (pCi/m2s) averaged over the entiremill site. This is 8 times the EPA guideline of 20 pCi/m2s (90) and 400 times the world averageof 0.42 pCi/m2s (91). Moving the tailings to another location or covering them with asufficiently thick layer of claylike material will create a satisfactory reduction. These levels willsoon be lowered; the piles are only temporary storage for materials from the remediatedproperties. 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 insideMonticello homes of the persons who experienced severe health effects. The EPA studies wereconducted in 1986. The radon levels measured were very low. Some data were reported in unitsof picocuries per liter (pCi/L) while others were in units of working levels (WL)(1) . EPA oftenassumes that the isotopes to which radon decays are at one-half the concentration they wouldreach if left undisturbed in a closed area. Under these normal conditions, 1 pCi/L is equal to0.005 WL. The data below use this conversion. The average radon concentration measured bythe scientists was 5.0 pCi/L in winter and 3.6 pCi/L in the spring (22). The average value of 4.3pCi/L is slightly above the EPA recommended guideline 4 pCi/L. EPA representatives alsostudied radon in several homes. Their measurements ranged from 0.4 to 1.6 pCi/L in the winterand 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 tooccur if contaminated mortar is used for such indoor applications as constructing fireplacemantels. These applications can be corrected by either replacing the affected mortar or applyingbarrier sealants to retard radon penetration. A thorough radioactive survey before beginningsuch efforts can help scientists set priorities and determine the most appropriate responsemeasures.

The operating mill released both radioactive and chemical effluents through the roaster stack, butit is the chemicals that would cause the greatest effects in animals and vegetation. Animals wereexposed by drinking contaminated water and grazing on soil contaminated by airbornedeposition and irrigation water. The radioactive material measured in those waters in recentyears has been observed to exceed the state of Utah standards as far as 2 to 3 miles downstreamof the property (31). Even higher levels existed during mill operations. However, cattle wereknown to be watered from springs whose concentrations were lower than those found in the riverwater. The radiation exposure is not expected to have been life threatening to either animals orplants, but the chemical effects could have been more pronounced. The chemicals include theyellow cake and black cake oxides of uranium and vanadium as well as sulfuric and hydrochloricprocessing acids. Uranium and vanadium are chemically toxic. In humans, uranium affects thekidney and vanadium irritates the intestines. Cattle may be affected similarly, with themagnitude depending on the intake. Fortunately, this pathway is not likely to affect humanhealth 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. Theseacids 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 tailingspile-soil-food crops pathway seems to be the most important. In that pathway, an individual hasused tailings to fill a home garden. We can check samples of vegetables grown in that soil to seehow 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 shouldreceive high priorities for remediation. The occupants of those areas should prudently keep theirradiation exposures as low as reasonably achievable. Adequate ventilation of the building theyoccupy is one good way to do that. Residential properties and commercial areas, including thethree ore storage sites, are now being remediated to bring them into compliance with standardsfor 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 fromother properties, an evaluation is in order. Once workers complete remediation of the vicinityproperties, the tailings piles will be moved. Performing an overall survey after all remediation iscomplete will determine whether the entire job is satisfactory. If it is, the public health riskshould be insignificant.

Specific Health Outcomes Concerns

  1. Could the following non-carcinogenic health effects be related to the mill site:miscarriages, stillbirths, birth defects, mental retardation, respiratory problems(including bronchitis, pleurisy, pneumonia, asthma, frequent coughs, andsinusitis), emphysema, pneumoconiosis, heart disease (including mitral valveprolapse, high blood pressure), anemia, high hematocrit, nosebleeds, slow healingof cuts, frequent infections, diabetes, bone problems (including spinal curvatureand brittle bone disease), arthritis, dental problems (poor teeth, many cavities,soft teeth), headaches (severe, chronic, migraine), muscle spasms, loss ofcoordination, tremors, dizziness, blackouts, eye disease, vision problems, kidneydisease, lumps/growths/moles, digestive tract problems, thyroid disease,neurofibromatosis, chronic fatigue syndrome, Parkinson disease, Crohn disease?

Based upon the available environmental sampling data that ATSDR staff reviewed concerningthe Monticello Mill Tailings Site, there is no indication that the chemical contaminants are atlevels that would result in adverse health effects. It is apparent from community responses thatin the past children swam in the tailings ponds. However, ATSDR scientists do not have anyenvironmental sampling data from those ponds; therefore, it is impossible to determine theconcentrations of arsenic, molybdenum, selenium, and vanadium to which the children wereexposed. One must come in direct contact with the tailings ponds (e.g., swimming) to haveexposure. If one lived near the pond, but never swam in the water, or if they did swim in thepond, but never swallowed any of the water, the contaminants in the pond could not have causedtheir illnesses. See the Toxicological Evaluation subsection of the Public Health Implicationssection of this public health assessment for a discussion of possible adverse health effects fromthe chemicals mentioned above.

There is no known association between radiation and heart disease, Crohn disease, Parkinsondisease, or neurofibromatosis. Miscarriages, stillbirths, birth defects, and mental retardationwere all observed in survivors of the atomic bomb incident, but the levels of radiation wereseveral orders of magnitude more than levels detected in and around Monticello. Infertility isconsidered to be a high-dose effect, not likely related to low-dose gamma radiation fromenvironmental sources. Loss of coordination, tremors, dizziness, and blackouts are symptoms ofhigh doses of radiation over a short period, followed by death a few hours to a day afterexposure. Digestive tract problems would result from similar high doses over a short period oftime, 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 specificmedical diagnosis, it is not possible to determine whether lumps, growths, and moles are resultsof radiation exposure.

Thyroid disease is related primarily to iodine 131 exposure. Thyroid problems should not resultfrom exposure to contamination generated at the Monticello Mill Tailings Site.

Respiratory problems, emphysema, pneumoconiosis, and sinusitis could be related to past orcurrent activities at the mill site. At the time the mill was in operation, conditions inside it weremost likely dusty, and workers were not required to wear respiratory protection. Inhalation ofdusts and particulates are known to interfere with breathing passages and can affect persons whoare sensitive to dusty conditions. Workers performing clean-up operations today are required toadhere to the Occupational Safety and Health Administration (OSHA) regulations cited in Title29, Code of Federal Regulations (CFR), Part 1910.120, Hazardous Waste Operations andEmergency Response. The other symptoms or conditions relate to poor hygiene (dentalproblems), old age (arthritis), lifestyles (headaches), or to unidentified causes (chronic fatiguesyndrome).

  1. Can we compare disease rates with rates for other towns or with state andnational data? How do registries record medical data (e.g., by hometown or byplace of diagnosis/death)?

In the Health Outcome Data Evaluation section of this public health assessment, ATSDRscientists compare the incidence of various types of cancer in San Juan County with incidence inthe 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 orcounty rates with the rest of the nation would not show a good representation of healthoutcomes, i.e., rates may be much lower compared to the nation but still may be elevated for thecity or county. The state of Utah records the medical data in its registries by the person's placeof residence and not the place of diagnosis/death.

  1. What are the synergistic effects of smoking and uranium exposure leading to cancer?

The National Academy of Sciences Biological Effects of Ionizing Radiation (BEIR) Committeehas concluded that "... exposure to natural uranium is unlikely to be a significant health risk inthe population and may well have no measurable effect." Studies have been conducted onradon-222, a decay or daughter product of natural uranium, to determine the implications for therisk of lung cancer. Doctors in Sweden determined that the effects of the interaction betweenradon exposure and smoking regarding lung cancer exceeded additivity and more likelyrepresented a multiplicative effect (94). However, a study conducted in the United Statesdetermined 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 itsassociated daughter products have on the development of various forms of cancer.

  1. What are the possible harmful public health effects of the solutions that went into the waste stream from the tailings piles?

Publicly accessible waste streams from the tailings piles could include windborne tailings thatdeposited on off-site soil or rainwater leachate that carried contaminants to the alluvial aquiferand to Montezuma Creek downstream of the mill site. The deeper aquifer known to be tappedby 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 residentsused 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 potentiallybe tapped for future household use, however, we evaluated this aquifer for its potential to affectthe public health. Contaminants from the tailings piles (arsenic, molybdenum, nitrate, selenium,vanadium, gross alpha, radium-226, radium-228, uranium-234, and uranium-238) have leachedinto the shallow alluvial aquifer. Those contaminants have been detected in the shallow aquiferat concentrations exceeding comparison values. However, direct human contact withgroundwater from the shallow aquifer, resulting in a completed exposure pathway, appearsunlikely for two reasons. First, the shallow aquifer is not presently used as a source of potablewater and is unlikely to be used in the future as a public water supply because of the unreliablewell yield and limited saturated thickness. Residents in the area downgradient of the mill sitecurrently obtain their water from the Monticello public water supply, which usesuncontaminated, topographically upgradient surface water sources. Second, the extent of theaquifer, which is physically confined to the narrow boundaries of the Montezuma Creek alluvialgravels, is limited. The aquifer downgradient of the mill site is estimated to be no more than500 feet wide, and the contamination plume extends no more than a mile downgradient before itdischarges into the creek. The plume has, therefore, reached its maximum dimensions. Toprevent use of the contaminated alluvial aquifer as a source of potable water, institutionalcontrols (establishing local ordinances that prevent the installation of wells screened in thecontaminated alluvial aquifer) are effective in ensuring that the aquifer is not used during thetime 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. Ifpeople eat large quantities of that produce, they might lose hair and their fingernails or toenailsmight crack or fall off.

ATSDR representatives are reviewing data on the quantity of radon and radium to whichresidents are being exposed because of the use of tailings in construction materials. When thesereviews are completed, it will be possible to evaluate whether the exposure is sufficient to affectthe residents' health.

Remediation Concerns

  1. What will happen to residents who live next to the mill site during the cleanup?

Representatives of the Department of Energy Grand Junction Projects Office (DOE-GJPO) haveno plans to relocate or buy out any property owners. Proper safety procedures such as dustcontrol and continuous radioactive air particulate monitoring during removal operations shouldensure the safety of nearby residents.

  1. What measures will be taken during remediation of the mill site to prevent recontamination of previously remediated properties?

Tailings removal from the mill site will be continuously monitored to ensure that off-sitereleases of radioparticulates do not exceed required standards. Dust control measures will beemployed as they have been at other mill tailings sites to prevent the spread of radioparticulates.

  1. Can remediated properties become recontaminated by resuspension of dust?

It is unlikely that remediation of a vicinity property will contaminate an adjoining propertyunless large volumes and high concentrations of material are involved. Successful remediationwill limit the concentration of radium-226 in the top 15 centimeters (cm) of soil to 5 pCi/g abovethe natural level of radium in that soil. Preliminary indications are that concentrations for manyproperties will be well below that level. In order for a property to be recontaminated, asufficient thickness and concentration of dust would have to be deposited. For example, assumethat the soil concentration at a newly remediated property is 4 pCi/g, concentration at theadjacent 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 thecontaminated property is at 100 pCi/g, the dust layer will have to be 0.3 cm thick. Higherconcentrations require thinner dust layers. Because of this relationship, it might be necessary toconsider dust control measures when decontaminating highly contaminated properties where thinlayers of dust could recontaminate adjacent properties. An integral part of any soil remedialaction includes extensive dust control.

  1. What are possible corrective actions for homes with radioactive mortar?

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 airconcentration inside the building. If the radiation levels are too high, the only course is toremove the affected material and rebuild the part of the building containing the contaminatedmaterial. If the radon air concentration is too high, there are two options, ventilation andmasking. Ventilation of the living spaces, or the basement or attic that feeds radon to the livingspaces, will direct the radon out of the building. There are several ways to accomplish theventilation: open windows; add a static precipitator to the ventilation system; or force ventilatethe rooms, basement, or attic with mechanical devices. Also, if the contaminated mortar isaccessible from the occupied side, as in a fireplace mantel, painting it with a heavy epoxy-typecoating 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 toimprove the condition.

  1. How can a resident find out a property's history?

Monticello and area residents with questions or concerns about their property and radioactivematerials 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.

  1. What criteria were used to decide the order of remediation for vicinity properties?

Vicinity property remediation plans were designed to clean up the most heavily contaminatedproperties first. A city block concept provided for grouping properties into procurementpackages that would be the most conservative of remediation funds. DOE representatives saidsocioeconomic status was never a consideration.

  1. Why have some properties have been remediated a second and even a third time?

Some properties have been remediated a second or even a third time because of the discovery ofadditional contaminants or because the property failed to meet air quality requirements. Othervicinity property projects have experienced similar secondary or tertiary remediations becausenot all materials that can contribute to interior air quality were discovered initially. In fact, atthe levels the DOE must achieve, natural contributions from certain rock units can createadditional remediation requirements.

  1. Was asbestos removed from the mill site and disposed of in a local sanitary landfill? What are the possible public health effects?

Asbestos was used as an insulating medium in mill buildings, pipe cladding, and vinyl asbestostile. Similar composite materials were being used for residential, commercial, and industrialpurposes throughout the country at the time the mill site was operational. Unneeded orunwanted 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. Becausethey are heat- and fire-resistant, they have long been used in building materials, friction-reducingproducts, and heat-resistant fabrics. Fibers can break away from natural asbestos (e.g., duringmining operations) or from products containing asbestos (e.g., as they are manufactured). Fiberfragments that become airborne can be inhaled. The healthy human lung is able to remove veryshort asbestos fiber fragments after the fibers are inhaled. However, the longer fiber fragmentscannot be easily removed from the lungs, and some of the shorter fibers are poorly removed bylungs that have been damaged (e.g., by smoking cigarettes). Large numbers of fibers retained inthe body for many years could lead to adverse health effects.

The very low concentrations of these fibers normally present in indoor or outdoor ambient airhave not been shown to be harmful to health. Brief one-time exposures to low or moderate fiberconcentrations have not been shown to cause harm. Adverse health effects such as cancer andasbestosis have appeared in people, especially smokers, occupationally exposed to high fiberconcentrations. However, the demolition of mill site facilities and the disposal of the demolitiondebris in a properly managed landfill are not expected to result in significant amounts ofexposure. People who are concerned that they may have been harmed by exposures to asbestoscan ask their physicians for chest Xrays. They and their physicians can learn more about thehealth effects of asbestos from ATSDR's Toxicological Profile for Asbestos (Update, 1994) andfrom ATSDR's Case Studies in Environmental Medicine: Asbestos.

  1. Were on-site storage buildings, building components, and tanks relocated off site?

We do not have specific information on the disposition of all the buildings, tubing, metalsheeting, and metal framework components from the mill site. Building components wererumored to have gone to the state prison. A field examination performed by DOE-GJPO projectpersonnel did not confirm the presence of such materials at the prison. We do not know thedisposition of tanks from the mill site. DOE representatives say no evidence exists that thematerials mentioned above are radioactively contaminated.

Concerns were expressed about the granary. The granary is a privately owned site where sixsilos once stored seeds of beans, corn, wheat, and other crops for farmers. It may also have beenan 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 beneathconcrete pads and large silos.

The first radioactive assessment began in March 1989, and the site (granary) was added to theDOE remediation list that year. The site was scanned to identify areas exceeding the areabackground of 17 microroentgen per hour (µR/hr) plus 30%. Surface contamination was foundaround the perimeters of five silos and two concrete pads and in a few other small areas. Theowner at the time did not allow cores to be taken through the concrete floors of the silos, soinvestigators used a borehole logger to measure the contamination depth around the siloperimeters. They assumed a uniform depth of contamination. The surveys of the largest slabfound hot spots across the slab and an elevated reading on contact with one of the slab's steelreinforcing tubes where the slab's concrete covering had broken away. The hot spots indicatedthat the slab contains some ore rocks and the tubing is contaminated; however, borehole loggingof some of those tubes did not identify any contamination. The tubes may have come from themill 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 beenincluded in the Monticello Vicinity Properties Remedial Action Program. See Appendix D ofthis document for more details about radioactive surveys and response actions at the granary.

  1. Is the golf course in Monticello contaminated?

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 themill site across Utah State Road 191. The surveys indicated that the mill tailings had been usedas fill and top dressing, and 40 areas were found that exceeded the Monticello background of14.6 µR/hr plus 30%. Elevated soil concentrations existed from 6-inch to 66-inch depths, withthe 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. Excavationbegan in July 1994 and is now complete, and backfilling with clean soil is under way. SeeAppendix D of this document for more details about radioactive surveys and response actions atthe golf course.

  1. Is the cemetery contaminated? Are there plans to remediate the cemetery?

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 4to 24 inches over 33,000 square feet of land.

This site was included on the remediation list in October 1991. Phase I of the remediationconstruction started in May 1993 and ended in June 1993. Phase II was included in September1993, the plan was approved in August 1995, and remediation construction was completed onJune 19, 1996. See Appendix D of this document for more details about radioactive surveys andresponse actions at the cemetery.

  1. Could wells on and near the mill site be contaminated?

Wells screened in the upper aquifer, especially wells in areas contiguous to the mill site and theold ore-buying stations, could be contaminated. Wells on the mill site are contaminated. Wellsdistant from the old ore-buying areas, Montezuma Creek Canyon, and the mill site are screenedin the lower aquifer and are not associated hydrologically with the mill site activities. Therefore,we do not suspect that they are contaminated.

  1. Does exposure to contaminated groundwater and surface water from the mill tailings leachate result in a long-term public health hazard?

Rainwater leachate carried contaminants to the alluvial aquifer and to Montezuma Creekdownstream of the mill site. The deeper aquifer known to be tapped by private wells forhousehold 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 couldpotentially be tapped for future household use, this aquifer was evaluated for its potential toaffect the public health. ATSDR scientists found that concentrations of arsenic and selenium inthe aquifer were insufficient in themselves to cause harm.

Selenium in Montezuma Creek might have increased the natural selenium content of the producegrown in soil irrigated by water from the creek. If people ate very large quantities of thatproduce for many years while drinking only the water from the alluvial aquifer, they might havesome hair thinning and cracking or splitting of their fingernails or toenails. If the aquiferbecame some people's sole source of drinking water and they also ate large quantities ofhomegrown produce irrigated by water taken from Montezuma Creek downstream of the millsite, molybdenum could cause gout-like illness. Contaminants in the produce would not beexpected to cause harm in individuals drinking water from the deeper aquifer.

  1. Will the final clean-up plan incorporate a suitable measure of public healthprotection for all present and future downstream uses of Montezuma Creekwater?

The purpose of the Operable Unit (OU) III study was to collect sufficient information and datato characterize the nature and extent of environmental contamination in OU III, identify thesources of contamination, assess changes in contamination patterns over time once on-sitesources (tailings piles) have been removed, and to calculate the levels of risk to human healthand the environment from the contaminants associated with OU III. The OU III soil andsediment area, which is located entirely on private land, begins approximately 0.5 miles east ofthe eastern mill site boundary and extends downstream approximately 14,100 feet. The area iscurrently used for cattle grazing and recreational purposes; no residences are located within theOU III soil and sediment study area. Soil and sediment characterization began in 1994 andcontinued through September 1996. The primary source of soil and sediment contamination inthe OU III soil and sediment study area is the mill site. Montezuma Creek, which flows throughthe tailings piles on the mill site, has been the primary transport mechanism for soils andsediments. The OU III Remedial Investigation draft report is currently under DOE review.

  1. Does the groundwater plume extend further downstream than where testing andremediation is taking place? Will people be exposed to contaminants in the 60years or so that passive restoration of groundwater is expected to take?

The initial findings of the OU III Remedial Investigation indicate that the alluvial aquifercontaminant concentrations decrease with increasing distance from the mill site, eventuallymatching 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 thanthe downgradient mill site boundary for radium-226, the most immobile site contaminant. TheOU III Remedial Investigation report, currently under DOE review, will discuss contaminantplumes in detail as well as present final conclusions about future exposure scenarios.

  1. Could radon gases be emitted from a permanent tailings repository?

Low levels of radon gas may be emitted from a permanent tailings repository; however, therepository is designed to make the release rates much lower so they will meet certain regulatoryspecifications in CFR 40.61 Subpart Q, National Emission Standard for Radon Emissions fromthe Disposal of Uranium Mill Tailings. According to this regulation, radon-222 emissions to theambient air from uranium mill tailings piles that are no longer operational shall not exceed 20picocuries per square meter second (pCi/m2s). This is much lower than the levels of radon-222currently released from tailings piles in Monticello, which range from 100 to 700 pCi/m2s.

  1. Why are new remediation areas suddenly surrounded by yellow "DO NOTENTER" tape and radioactive signs?

General construction and the disturbance of soils during removal actions can cause new hazardsand intensify existing ones. Exposure to radiation and dusts is among the hazards. Remedialactions create greater need for short-term protection of workers and residents from these hazards.

  1. Will ATSDR representatives follow up on former residents who have moved away from Monticello?

ATSDR staff members are making every effort to ensure that former residents of Monticello andthe surrounding area are contacted. We have developed a site-specific mailing list of around2,000 names. Approximately 25% of the individuals on the mailing list are former residents ofMonticello and the area. These individuals have been contacted and given the opportunity toexpress their public health concerns and questions.

ATSDR staff members have heard from several of these former residents. We have sent publichealth information and literature packets to those individuals expressing further interest. Wewill continue to inform current and former residents of Monticello and the area of ongoingATSDR activities.

If anyone reading this document has information on individuals who would like to be added tothe mailing list, please provide names and addresses to the following office:

    Monticello Mill Tailings Site Project
    1600 Clifton Road, NE
    Mail Stop E-56
    Atlanta, GA 30333
    FAX (404) 639-6075
  1. Can dose calculations for utility workers be evaluated?

We can evaluate any dose calculations that have been performed for utility workers to see if thecalculations are reasonable. Those dose calculations would have factored actual data andassumptions into a model. If there is need for reevaluation, we should review the original data,assumptions made, and mathematical formulas used.

  1. Will the properties containing contaminated sand from Dry Valley beremediated?

The properties containing sand from Dry Valley have been classified as disputed properties. Thedisputed properties that exceed the applicable standards for cleanup will be remediated as part ofthe Monticello project. The only difference between vicinity properties and disputed propertiesis 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.

  1. What are the most likely health effects associated with working at the mill site?

Mill worker public health concerns should be referred to NIOSH, which has staff members whoconduct research on the health effects of exposures in the work environment. ATSDRrepresentatives will ensure that NIOSH researchers are aware of mill workers' public healthconcerns.

ATSDR scientists will continue to review any future community health concerns that becomeavailable. Should additional information become available that alters the findings of this publichealth assessment or addresses issues described herein, this public health assessment will bemodified as needed.

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