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PUBLIC HEALTH ASSESSMENT

UPPER TENMILE CREEK MINING AREA
RIMINI/HELENA, LEWIS AND CLARK COUNTY, MONTANA


PURPOSE AND HEALTH ISSUES

Upper Tenmile Creek Mining Area was proposed for the National Priorities List (NPL) on July 22,1999 and listed on October 22, 1999. In this public health assessment, ATSDR evaluates the publichealth significance of the site as mandated by Congress. ATSDR has reviewed availableenvironmental data and community health concerns to determine whether adverse health effects arepossible. In addition, this public health assessment recommends actions to prevent, reduce, or further identify the possibility for site-related adverse health effects.


BACKGROUND

Site Description

This site description comes in part from the Draft Preliminary Remedial Investigation Report (April2000) and the Final Site Inspection report (April 1995) [1,2]. The Upper Tenmile Creek MiningArea NPL site is located primarily within Lewis and Clark County near Helena, Montana (Figure1). Within the Tenmile Creek drainage basin, the site extends from Highway 12 south to thedrainage divide, where it adjoins the Basin Mining Area NPL site. At the drainage divide, the non-operating Basin Creek Mine is shared between Upper Tenmile and Basin NPL sites and serves as thewaste repository for both sites. The Tenmile Creek basin is the primary watershed within the site.Tenmile Creek flows to the north through the site; its headwaters are approximately five milesupstream of the community of Rimini, which is located at the approximate center of the site. The site is estimated to comprise 29,000 acres.

History

Mining activity in the Upper Tenmile Creek watershed occurred in the Rimini Mining District from1870 into the 1950s. Gold, lead, zinc, and copper were mined, with most production occurringbefore the 1900s. Falling silver prices in the early 1890s caused most of the region's mines to close.The last major producer to operate in the Rimini Mining District was the Montana Lead Company,which mined lead from 1927 to 1938. The mining activity in the area since that time has beenlimited to very small operations. The last known active mining at the site ended in 1953.

Extensive mining in the watershed has resulted in widespread metals contamination. Exposed wasterock and tailings piles can be found throughout the upper basin and along Tenmile Creek and itstributaries. Some wastes contain very high concentrations of heavy metals. Because of surface waterrunoff, the wastes have contributed heavy metals to Tenmile Creek and its tributaries, contaminatingstream sediments and severely impacting water quality. Another contributor to stream deteriorationis acid mine drainage (AMD), heavy metal-laden acidic water discharges that emanate from underground mine workings or from mine waste piles.

Site map
Figure 1. Site Map

Demographics

The Upper Tenmile Creek Mining Area is sparsely populated. In 1995, there were 19 year-roundresidents, located primarily in the community of Rimini [1]. The watershed is a popular area forrecreational activities including the seasonal use of cabins, hunting, fishing, camping, and the use ofsnowmobiles, ATV's, dirt bikes, and mountain bikes. Woodcutting and gathering also takes placeon the site. The watershed contains a significant amount of private land, mostly old mining claims,that could be developed for year-round or seasonal residences.

Figure 2 shows the demographic information for the population of Upper Tenmile Creek MiningArea. There are about 185 people in the area. Approximately 20 are children under 6 years of age. The population is mostly white.

Land and Natural Resource Use

There are dozens of old mine claims located throughout the Tenmile Creek watershed. Many ofthese claims have associated waste rock piles, tailings, or physical hazards. Because the mine claimsconstitute private land that is surrounded by US Forest Service land, development of full- and part-year residences is occurring, in some cases, on top of or close to these hazards.

Along Tenmile Creek and its tributaries are five water supply intakes for the City of Helena. Thiswater is treated at the Tenmile Water Treatment Plant before reaching the consumer. Most of thepeople who live in Rimini and the watershed area rely on private groundwater wells or bottled waterfor their drinking water. Many of the residents withdraw untreated water from the Tenmile Creekdrinking water intake that may be used for drinking as well as other household uses.

A Boy Scout camp is located about one mile downstream from Rimini. Campers and hikers alsofrequent the area. The Rimini area has in the past attracted recreational fishers, but in recent yearsthe fishery has declined, possibly due to metals and acid contamination and very low water levels.The downstream (northern) end of Tenmile Creek and other creeks in the area are used often for fishing, mostly during the spring.


DISCUSSION

Data Used

A number of environmental investigations have been conducted within the Upper Tenmile CreekMining Area, as summarized in the Draft Data Summary and Usability Report [3]. Theseinvestigations included sampling of surface water and sediments, residential and groundwatermonitoring wells, waste rock and tailings, and water discharges from mine shafts and seeps. Thesampling was part of investigations conducted by various state and federal agencies and their contractors since the early 1980s.

Demographic information
Figure 2. Demographic information

In March 2000, EPA's contractor, CDM Federal, conducted a thorough evaluation of the existingdata to determine its validity and suitability for use. Generally, data generated under a documentedQA/QC program were deemed acceptable for use. Data with no documentation were deemedunacceptable. Data with incomplete documentation was used for screening applications only.ATSDR reviewed the Draft Data Summary and Usability Report and agrees with the rationalepresented [3]. CDM Federal provided ATSDR with electronic files of the Upper Tenmile CreekNPL site database, which contains the data used to produce this health assessment [4]. This databaseis current as of February 2001.

ATSDR visited Upper Tenmile Creek Mining Area(1) to better understand the physical setting of thesite and its relationship to the people living and working nearby. We also met with communitymembers and local, state, and federal officials to learn more about the site and the community health concerns.

Evaluation Process

ATSDR's process for evaluating the possible health impacts of contaminants is summarized hereand described in more detail in Appendix A. ATSDR uses comparison values (CVs) to determinewhich chemicals to examine more closely. CVs are health-based thresholds below which no knownor anticipated adverse human health effects occur. However, exceeding a CV does not mean thathealth effects will occur, just that more evaluation is needed. Further information about CVs ispresented in Appendix B.

Further evaluation focuses on identifying which chemicals and exposure situations could be a healthhazard. The first step is the calculation of child and adult exposure doses, as described in AppendixC. These are then compared to an appropriate health guideline for a specific chemical contaminant.Any exposure situation resulting in an exposure dose lower than the appropriate health guideline is eliminated from further consideration and evaluation.

The next step is the revision of the exposure dose to better match probable rather than worst-caseexposure scenarios. Lastly, these revised exposure doses are compared to known toxicologic healtheffects levels identified in ATSDR's Toxicological Profiles. If the chemical of concern is acarcinogen, the cancer risk is recalculated using the revised exposure dose. These comparisons are the basis for determining the degree of exposure.

Exposure Pathways and Contaminants of Concern

The available data and information indicate that the most likely means of exposure to sitecontaminants are through drinking private well water, drinking surface water, incidental ingestion ofcontaminated soils, incidental ingestion of mining waste, exposure to surface water or streamsediments through recreational activities, and inhalation of road dust. These seven completedexposure pathways, along with a discussion of multiple exposure pathways, will be described in the following sections.

Well Water Pathway

Many residents of the Rimini area rely on private groundwater wells for their drinking water supply.Several residential water wells have been sampled in the past, with data existing for the period from1986 to 2000. The following evaluation of well water contamination health effects considers onlythe year 2000 groundwater sampling effort, which included almost all the wells in the UpperTenmile Creek Mining Area. A review of the complete data set shows that the 2000 testing issimilar to historical data.

In well water testing, some of the homeowners' wells were found to have contaminant levels wellabove the maximum contaminant level (MCL), or drinking water standard. Homeowners wereadvised of these results and were offered biomonitoring at the Lewis and Clark City-County HealthDepartment. EPA also provided bottled water to use as an alternate drinking water supply. Sincethen, most of these homeowners have installed under counter treatment systems using reverseosmosis or activated alumina technologies tailored for the existing water chemistry. These systemshave been effective in reducing contaminants in the well water to below drinking water standards.These actions have effectively interrupted the well water exposure pathway so that it no longer posesa hazard. It is not known how many of the homeowners actually drank water from their wells.However, to highlight potential health effects that might have occurred if the wells with high levelsof contaminants had been used for drinking water, the toxicological discussion below considers all the residential well results.

For initial screening, the sampling results are compared to appropriate CVs described in AppendixA. Table 1, below, lists six contaminants detected at least once above their corresponding CV in residential groundwater wells.

Table 1.

Residential Well Groundwater Contaminants Above Comparison Values
  Range in Water in ppb1 Samples > DL2 Samples > CV3 CV in ppb CV Source4
Arsenic 0.4 - 659 36 / 36 36 / 315 .02 / 36 CREG7 / EMEG8
Cadmium ND - 237 25 / 36 10 2 EMEG8
Lead ND - 80 35 / 36 5 15 EPA ACTION LEVEL
Iron ND - 29,500 35 / 36 2 11,000 R3 RBC9
Manganese ND - 8,650 34 / 36 6 500 RMEG10
Zinc 2 - 22,800 35 / 36 8 3,000 EMEG8
1 ppb = parts per billion of chemical in water. ppb = mg (microgram) per liter of water.
2
DL = detection limit.
3 CV = comparison value.
4
These comparison values are described in Appendix B.
5 The first number is the number of samples above the CREG and the second is the number above the EMEG.
6
The first number is the CREG and the second is the EMEG.
7 CREG = cancer risk evaluation guide.
8 EMEG = environmental media evaluation guide.
9
R3 RBC = EPA Region 3 risk-based concentration.
10
RMEG = remedial media evaluation guide.

People could be exposed to contaminants present in the groundwater by drinking the groundwater,breathing water vapor during showering or other activities, or by contact with the skin.Proportionally, people's exposure from drinking water is much greater than that from inhalation orskin contact. Therefore, we only evaluated exposure from drinking the water.

The estimated doses of the chemicals that adults and children would be exposed to are comparedwith health guidelines. This procedure is described in detail in Appendix C. Health guidelines aredoses below which no adverse health effects are likely to occur. Exposure situations which result in doses lower than the health guideline are dropped from further consideration.

Table 2 presents the estimated exposure doses for the residential groundwater contaminants ofconcern identified in Table 1. These exposure doses are based on an assumption of year-roundconsumption of the maximum concentration of groundwater. As indicated, exposures to themaximum concentration of all of the six contaminants of concern from Table 1 are above the corresponding health guideline and will be evaluated further.

Table 2.

Estimated Exposure Doses and Cancer Risk for Groundwater Contaminants Compared to Health Guidelines for Ingestion1
Contaminant Maximum Level in parts per billion (ppb) Estimated Exposure Dose in mg/kg/day2 Health Guideline in mg/kg/day Source of Guideline Cancer Risk
Adult Child
Arsenic 659 0.02 0.07 0.005 / 0.0003 Provisional Acute / Chronic Oral MRL3 3 in 1005
Cadmium 237 0.007 0.02 0.0002 Chronic Oral MRL3 No CSF7
Iron 29,500 0.8 3.0 0.3 RfDo R34 N/A8
Lead 80 0.002 0.008 None6 - No CSF7
Manganese 8,650 0.2 0.9 0.02 RfDo R34 N/A8
Zinc 22,800 0.7 2.3 0.3 Chronic Oral MRL3 N/A8
1 An explanation of how these exposure doses and cancer risk were calculated can be found in Appendix C. No health guidelines are available for lead. No cancer slope factors are available for cadmium, manganese, lead, or zinc.
2
mg/kg/day = milligrams of chemical per kilogram of body weight per day.
3 MRL = ATSDR's minimal risk level.
4 RfDo R3 = EPA Region 3's reference dose.
5 Maximum additional lifetime risk of cancer per 100 individuals.
6
No health guideline; EPA action level equals 15 ppb.
7 No cancer slope factor available.
8 Not applicable; substance is not classified as a carcinogen.

Toxicological Evaluation

There are no health effects expected from drinking water that meets drinking water standards, andpeople owning wells with contaminants above the MCL have begun treating their water or beenprovided with alternate drinking water. However, because it is possible that in the past people drankwater from wells that had high levels of contaminants, all the well results are considered here. Someof the wells tested had very low contaminant levels, while others had much higher levels of severalcontaminants. The following toxicological discussion is based on a worst-case scenario of year-round exposure to the maximum level of each contaminant. The health effects that could actuallyhave occurred from exposure to site contaminants through drinking private well water depends onthe specific concentration in that well and the actual intake of water from the well. The exposuredoses in Table 2 were calculated assuming the EPA default drinking water intake rate of 2 liters perday for adults and 1 liter per day for children for one year [5]. The actual exposure would be less ifit occurred only on weekends during the warm months, such as with a vacation home.

Arsenic

Acute health effects could occur in adults and children if they drank water containing the maximumlevel of arsenic measured in private wells. In addition, long-term exposure to the higherconcentrations of arsenic could cause health effects for adults or children drinking the water year-round. If the exposure occurred only on the weekends, as with a vacation home, health effects areless likely. Exposure over a period of many years to arsenic in well water could increase a resident'schance of cancer.

Both adult and child maximum calculated exposure doses are higher than ATSDR's provisionalacute MRL of 0.005 mg/kg/day [6]. For one out of the 36 wells sampled, the child dose is higherthan the lowest observed adverse effect level (LOAEL) of 0.05 mg/kg/day for acute exposure forhumans [6]. At the acute LOAEL, gastrointestinal effects such as nausea, vomiting, and diarrheahave been observed.

Regarding long-term (chronic) exposure, the calculated maximum adult and child exposure doses toarsenic are higher than the LOAEL of 0.014 mg/kg/day for chronic exposure for humans [6]; healtheffects are possible at this exposure level. Three out of 36 wells sampled resulted in a child exposuredose higher than the chronic LOAEL, and 1 out of 36 resulted in an adult exposure dose above thatlevel. At the chronic LOAEL, symptoms such as skin changes have been observed.

Based on human epidemiological studies, arsenic is a known carcinogen [6]. Exposure to themaximum arsenic concentration measured in a water well would present a moderate to highincreased lifetime risk of cancer if exposures were daily for 70 years.

The remaining 33 private wells tested had arsenic at concentrations too low to cause any healtheffects. The possibility of health effects actually occurring for the other wells depends on manyfactors, including the actual exposure scenario. Anyone who owned a well with any contaminantlevel higher than the MCL has now been provided with an alternate water supply, interrupting thisexposure pathway.

Cadmium

The maximum level of cadmium measured in private wells could lead to serious health effects ifexposure occurred over several months.

Three out of 36 wells sampled resulted in adult and child exposure doses greater than the NOAEL of0.0021 mg/kg/day for humans [7]. The LOAEL for serious effects such as kidney problems is0.0078 mg/kg/day [7]. Three of the calculated adult exposure doses were between the NOAEL andLOAEL, and the corresponding calculated child doses were higher than the LOAEL. Therefore,health effects could occur.

Animal data indicate that cadmium is a probable human carcinogen [7]. However, there is no oralcancer slope factor for cadmium, so it was not possible to evaluate carcinogenic risk.

The remaining 33 private wells tested had cadmium concentrations too low to cause any healtheffects. The possibility of health effects actually occurring for the other wells depends on manyfactors, including the actual exposure scenario. Anyone who owned a well with any contaminantlevel higher than the MCL has now been provided with an alternate water supply, interrupting thisexposure pathway.

Iron

The maximum level of iron measured in private wells is not likely to result in health effects in adultsor children.

Two out of 36 of the wells tested had calculated adult exposure doses, and 5 out of 36 wells hadcalculated child exposure doses, higher that the health guideline of 0.3 mg/kg/day. Exceeding thehealth guideline does not mean that health effects will occur, however. Severe toxic effects are notlikely with exposures under 30 mg/kg of body weight [8]. None of the wells had iron concentrationsresulting in exposure doses this high. Long-term exposure to elevated iron can cause clinical effectssuch as accumulation of iron in the liver [8]. However, water from the wells with higher ironconcentrations would have had an unpleasant taste, decreasing the possibility that it was used fordrinking.

The remaining 31 wells had iron at levels too low to cause health effects. The possibility of healtheffects actually occurring for the other wells depends on many factors, including the actual exposurescenario. The two wells which had the highest iron concentrations also had other contaminants atelevated levels. The owners of these wells have been provided with an alternate water supply,interrupting this exposure pathway.

Lead

Exposure to lead from drinking private well water alone is not likely to result in health effects inchildren or adult residents. Please see page 25, however, for a discussion of possible health effectsfrom multiple exposure pathways.

Exposure to lead causes a wide range of effects [9]. However, the lack of a clear threshold for health effects and the need to consider multi-media routes of exposure has made determining NOAELs and LOAELs for lead difficult. The level of lead in blood is a good measure of recent exposure to lead and also correlates well with health effects. Children are especially sensitive to lead. Many of its effects are observed at lower concentrations in children than in adults. Lead levels in children's blood of 10 micrograms per deciliter (µg/dL), and perhaps lower, have been associated with small decreases in IQ and slightly impaired hearing and growth. A slope factor for the increase in blood lead concentration per increase in water lead concentration for infants has been calculated as 0.04 µg/dL blood per part per billion (ppb) lead at water lead levels above 15 ppb [9]. The corresponding slope factor for school children was found to be 0.03 µg/dL per ppb. Using the maximum concentration of 80 ppb lead measured in a private well, increases in blood lead concentrations of 3.2 µg/dL and 2.4 µg/dL are predicted for infants and school children, respectively. The health effects associated with such increases would depend partly on the existing body burden of lead.

Only five of the private wells tested had lead levels above the MCL. The remaining 31 wells hadlead levels too low to cause health effects. The possibility of health effects actually occurring for thelead-containing wells depends on many factors, including the actual exposure scenario. Anyone whoowned a well with any contaminant level higher than the MCL has now been provided with analternate water supply, interrupting this exposure pathway.

Animal data indicate that lead is a probable human carcinogen [9]. However, there is no cancerslope factor for lead, so it was not possible to evaluate carcinogenic risk. The conclusion that leadcauses cancer in animals is based on experiments with a different form of lead than that which isfound in the mining wastes contaminating the Upper Tenmile Creek Mining Area.

Manganese

Six of the 36 wells tested had manganese levels higher than the comparison value. Exposure tomanganese by ingesting this well water could cause health effects in adults and children. Theremaining 30 wells had manganese levels that are not expected to cause health effects.

Epidemiologic studies suggest an association between ingesting water containing elevatedconcentrations of manganese and the development of neurological symptoms. However, each of thestudies had uncertainty regarding the exposure level or whether the effects were solely attributable tomanganese, so that no NOAEL, LOAEL, or minimal risk level could be identified [10]. Studies withrats have shown a LOAEL for neurological changes of 14 mg/kg/day, an order of magnitude higherthan the estimated child dose. However, humans appear to be more sensitive to manganese thananimals [10]. Therefore, the child and adult manganese dose for this pathway could cause healtheffects.

The six wells which had manganese concentrations above the comparison value also had othercontaminants at elevated levels. The owners of these wells have been provided with an alternatewater supply, interrupting this exposure pathway. The possibility of health effects actually occurringfor the manganese-containing wells depends on many factors, including the actual exposurescenario.

Zinc

Health effects could occur in children consuming water with the highest concentrations of zinc. Therecommended daily allowance for zinc, 15 mg/day for men and 12 mg/day for women, correspondsto an approximate dose of 0.2 mg/kg/day [11]. Consuming large amounts of zinc (10 to 15 times theRDA) for a short time can cause stomach cramps, nausea, and vomiting. Exposure to these highlevels over several months may cause anemia, damage the pancreas, and decrease levels of highdensity lipoprotein (HDL), "good" cholesterol [11]. The adult exposure dose for zinc is about 3.5times the RDA and would not be expected to lead to health effects. However, the child dose is morethan 10 times the RDA. Therefore, health effects are possible.

Six of the 36 wells tested had zinc concentrations resulting in a calculated child exposure dose ofgreater than 1 mg/kg/day, or 5 times the RDA. The remaining 30 wells had zinc concentrations toolow to cause any health effects. The wells which had the highest zinc concentrations also had othercontaminants at elevated levels. The owners of these wells have been provided with an alternatewater supply, interrupting this exposure pathway. The possibility of health effects actually occurringdue to zinc in the wells depends on many factors, including the actual exposure scenario.

Surface Water Ingestion Pathway

Some residents of Rimini withdraw untreated water from above the Tenmile Creek intake forresidential use. Some residents may drink this water. There was limited data (8 sample points)available for the Tenmile Intake surface water quality. Table 3 lists the contaminants which weredetected at least once above the CV.

It should be noted that some circumstances, such as snow runoff, rain events, or releases ofcontaminated waters from old mine sites, may result in transient very high levels of heavy metals inTenmile Creek. These would be difficult to measure during routine sampling. The following analysis does not consider these potential events, only the available limited data.

Table 3.

Surface Water Concentrations Above Drinking Water Comparison Values- Tenmile Intake Only
Contaminant Range in Water in ppb1 Samples > DL2 Samples > CV3 CV in ppb CV Source4
Antimony ND - 5.5 4 / 8 2 4 RMEG9
Arsenic 3.5 - 10.4 8 / 8 8 / 85 .02 / 36 CREG7 / EMEG8
Lead ND - 16.4 7 / 8 1 15 EPA ACTION LEVEL
Thallium ND - 3.1 4 / 8 1 2.6 R3 RBC10
1 ppb=parts per billion of chemical in water. ppb= mg (microgram) per liter of water.
2 DL = detection limit.
3 CV = comparison value.
4
These comparison values are described in Appendix B.
5
The first number is the number of samples above the CREG and the second is the number above the EMEG.
6 The first number is the CREG and the second is the EMEG.
7 CREG = cancer risk evaluation guide.
8 EMEG = environmental media evaluation guide.
9
RMEG = remedial media evaluation guide.
10 R3 RBC = EPA Region 3 risk-based concentration.

Table 4 presents the estimated exposure doses for the surface water contaminants of concernidentified in Table 3. These exposure doses are based on an assumption of year-round consumptionof the maximum concentration level of the surface water. As indicated in the table, the maximumconcentration of each of the four contaminants of concern from Table 3 resulted in exposure doses above the corresponding health guideline and will be evaluated further.

Table 4.

Estimated Exposure Doses and Cancer Risk for Surface Water Contaminants at the Tenmile Creek Intake Compared to Health Guidelines for Ingestion1
Contaminant Maximum Level in parts per billion (ppb) Estimated Exposure Dose in mg/kg/day2 Health Guideline in mg/kg/day Source of Guideline Cancer Risk
Adult Child
Antimony 5.5 0.0002 0.0006 0.0004 Oral RfD N/A7
Arsenic 10.4 0.0003 0.001 0.0003 Chronic Oral MRL3 4 in 10,0005
Lead 16.4 0.0005 0.002 None6 - No CSF8
Thallium 3.1 0.0001 0.0003 0.00007 RfDo R34 N/A7
1 An explanation of how these exposure doses and cancer risk were calculated can be found in Appendix C. No health guidelines are available for lead. No cancer slope factors are available for cadmium, manganese, or zinc.
2
mg/kg/day = milligrams of chemical per kilogram of body weight per day.
3 MRL = ATSDR's minimal risk level.
4 RfDo R3 = EPA Region 3's reference dose.
5
Maximum additional lifetime risk of cancer per 10,000 individuals.
6 No health guideline; EPA Action Level equals 15 ppb.
7 Not applicable; substance is not classified as a carcinogen.
8
No cancer slope factor available.

Toxicological Evaluation

It should be noted that there are not sufficient data on the quality of the surface water at the TenmileIntake; therefore, conclusions reached in this section are based on the available limited data. Thefollowing toxicological discussion is based on a worst-case scenario of year-round exposure to themaximum level of each contaminant. The health effects actually occurring from exposure to sitecontaminants through this pathway depends on the specific contaminant concentration as well as theactual intake. The exposure doses in Table 4 were calculated assuming the EPA default drinkingwater intake rate of 2 liters per day for adults and 1 liter per day for children for one year. Theactual exposure may be less because of the variable availability of water in the creek or if exposureoccurred only on weekends during the warm months, such as with a vacation home. Also, floodevents and other circumstances can result in transient, very high metals levels which may not bereflected in the limited data. Thus, there is considerable uncertainty in the following discussion.

Arsenic

Non-cancer health effects are not expected to occur from exposure to arsenic by drinking surfacewater from the Tenmile Creek Intake. The adult exposure dose is lower than the health guideline, sono health effects are expected. The child exposure dose to arsenic is higher than the NOAEL of0.0008 mg/kg/day for chronic exposure for humans, but an order of magnitude lower than theLOAEL of 0.014 mg/kg/day [6]. At the LOAEL, symptoms such as skin changes have beenobserved. It is unlikely that health effects will occur in this situation.

Exposure to the maximum arsenic concentration measured at the Tenmile Creek Intake wouldpresent a low to moderate increased lifetime risk of cancer if daily exposures occurred for 70 years.However, due to the uncertainties in determining risk and the actual exposure scenarios, increasedrisk of cancer is unlikely from drinking the surface water.

Other Contaminants

For lead, only one sample is slightly higher than the EPA action level of 15 ppb. No health effectsare expected to occur from exposure to lead from drinking surface water drawn from the TenmileCreek Intake. Animal studies indicate that lead is a probable human carcinogen [9]. However, thereis no cancer slope factor for lead, so carcinogenic risk could not be evaluated.

There is no data on chronic exposure to thallium. However, both adult and child exposures were atleast two orders of magnitude lower than the NOAEL for intermediate exposure [12]. Because theexposure dose is based on the maximum dose and people would be exposed to an averageconcentration, no health effects are expected from exposure to thallium.

Because adult and child exposures to antimony are several orders of magnitude lower than the NOAEL [13], no health effects are expected from this exposure.

Soil Pathway

Residents and recreational users will ingest soils as an incidental consequence of typical outdooractivities. This is an especially important pathway for children, who exhibit hand-to-mouth behaviorand have consequently higher soil ingestion rates. Soil sampling took place in the summer of 2000in Rimini and other residential areas of the Upper Tenmile Creek site, with a total of 39 residentialyard samples collected. Seven of these samples were collected in areas identified as children's playareas. Table 5 lists the six contaminants that were detected in the soil samples at least once above the CV.

Table 5.

Soil Contaminants Above Comparison Values
Contaminant Range in Soil in ppm1 Samples > DL2 Samples > CV3 CV in ppm CV Source4
Antimony ND - 101 32 / 39 18 20 RMEG5
Arsenic 15 - 1730 39 / 39 39 / 386 0.5 /207 CREG8 / EMEG9
Cadmium ND - 24 26 / 39 6 10 EMEG9
Iron 12000 - 66005 39 / 39 31 23,000 R3 RBC10
Lead 16 - 4845 39 / 39 20 400 SSL11
Manganese 259 - 3387 39 / 39 1 3,000 RMEG7
1 ppm = parts per million of chemical in soil. ppm = mg (milligram) per kg (kilogram) of soil.
2
DL = detection limit.
3 CV = comparison value.
4 These comparison values are described in Appendix 1.
5 RMEG = remedial media evaluation guide.
6 The first number is the number of samples above the CREG and the second is the number above the EMEG.
7
The first number is the CREG and the second is the EMEG.
8
CREG = cancer risk evaluation guide.
9 EMEG = environmental media evaluation guide.
10
R3 RBC = EPA Region 3 risk-based concentration.
11 SSL = EPA soil screening level.

Exposure doses for the contaminants of concern from Table 5 were calculated. The average of allsoil data was used to estimate chronic exposures, and the maximum arsenic level in identified playareas was used to estimate acute exposure for children exhibiting pica behavior (eating of non-fooditems such as dirt). Table 6 presents the estimated exposure doses which were higher than thecorresponding health guideline and will be evaluated further. The cadmium exposure dose was lower than the health guideline and was therefore dropped from consideration.

Table 6.

Estimated Exposure Doses and Cancer Risk for Soil Compared to Health Guidelines for Ingestion1
Contaminant Concentration2 in parts per million (ppm) Estimated Exposure Dose in mg/kg/day3 Health Guideline in mg/kg/day Source of Guideline Cancer Risk
Adult Child
Antimony 28 0.00002 0.0006 0.0004 Oral RfD4 N/A5
Arsenic 427 0.0002 0.007 0.0003 Chronic Oral MRL6 4 in 10,0007
Arsenic- Acute 688 - 0.38 0.005 Provisional Acute MRL6 -
Iron 29,886 0.02 0.6 0.3 RfDo R310 N/A5
Lead 638 0.0005 0.01 None11 - No CSF9
Manganese 1,201 0.0009 0.02 0.02 RfDo R310 N/A5
1 An explanation of how these exposure doses and cancer risk were calculated can be found in Appendix C. No health guidelines or cancer slope factors are available for lead.
2
Average of all soil data used for chronic calculations; maximum of soil data from identified play areas used for acute arsenic calculations.
3 mg/kg/day = milligrams of chemical per kilogram of body weight per day.
4
RfD = EPA's reference dose.
5 Not applicable; substance is not classified as a carcinogen.
6 MRL = ATSDR's minimal risk level.
7 Maximum additional lifetime risk of cancer per 10,000 individuals.
8
Based on ingestion of 5 grams of soil in one day by a 10-kg child exhibiting pica behavior (eating of non-food items).
9 No cancer slope factor available.
10 RfDo R3 = EPA Region 3's reference dose.
11 No health guideline; EPA soil screening level equals 400 ppm.

Toxicological Evaluation

It should be noted that the above exposure doses are likely overestimates of actual exposure thatmay occur from soil. Exposure to soil will be less during the winter months due to snow cover andless outdoor activity.

Arsenic

Exposure of children to arsenic in soil may cause both short- and long-term health effects. Adultsexposed to the soil are not expected to suffer noncancer health effects. However, exposure to arsenicthrough contact with site soils could increase a resident's chance of cancer if exposure were formany years.

For acute arsenic exposures, it was assumed that children exhibit pica behavior and ingest up to5000 milligrams of soil from play areas in one day. In all seven "play area" samples, the estimateddose for children exhibiting pica behavior is higher that the short-term (acute) arsenic LOAEL of0.05 mg/kg/day [6]. Three of these estimated doses were more than an order of magnitude higherthan the acute LOAEL. The estimated acute doses for children who do not exhibit pica behavior arelower than the acute LOAEL. At the acute LOAEL, effects such as nausea, vomiting, and diarrheamay occur. No acute health effects are expected for adults.

The chronic child exposure dose based on the average arsenic concentration in soil is higher than thelong-term NOAEL of 0.0008 mg/kg/day [6]. It is about one half the long-term LOAEL of 0.014mg/kg/day [6]. Health effects are not likely to occur at this exposure level. The adult exposure doseto arsenic is lower than the chronic NOAEL of 0.0008 mg/kg/day [6]. No long-term noncancerhealth effects are expected to occur in adults based on this exposure.

Based on human epidemiological studies, arsenic is a known carcinogen [6]. Exposure to theaverage concentration of arsenic found in soil (427 ppm) would present a low to moderate increasedlifetime risk of cancer if exposures were daily for 70 years.

There is some uncertainty whether health effects will actually occur if there is exposure to theselevels. Both acute and chronic LOAELs are based on exposure to arsenic in water, not soil. Arsenicis much less available for uptake when it is in soil. Exposure dose calculations used the EPA defaultof 80% relative bioavailability, as defined on page 50. However, regional studies have shown that aslittle as 10 to 50% bioavailability is more reasonable for this type of contamination [14]. The use ofa lower bioavailability would further decrease the effective exposure dose.

Lead

Exposure to lead in soil alone is not likely to result in health effects in children or adult residents.

Exposure to lead causes a wide range of effects [9]. The level of lead in blood is a good measure of recent exposure to lead and also correlates well with health effects. Children are especially sensitive to lead, and many of its effects are observed at lower concentrations in children than in adults. Levels of 10 µg/dL and less in children's blood have been associated with small decreases in IQ and slightly impaired hearing and growth. Epidemiological studies have determined soil slope factors which predict blood lead levels to increase from between 0.0007 and 0.0068 µg/dL per part per million (ppm) increase in soil lead level [9]. This wide range resulted from the presence of different sources of lead, exposure conditions, and exposed populations. The health effects associated with such an increase would depend partly on the existing body burden of lead. Using the highest slope factor of 0.0068 µg/dL/ppm, the average lead concentration measured in soil (638 ppm) could be expected to increase blood lead levels by 4.3 µg/dL.

The possibility of such an increase actually occurring with this exposure is small. In soil, tailingsmaterials are typically less bioavailable than other sources of lead, such as fine flue dust [9].Therefore, the soil slope factor will most likely be much lower than the maximum reported above.Also, children will have lower exposures since they will have minimal contact with site soilsthroughout the winter months.

Animal data indicate that lead is a probable human carcinogen [9]. However, there is no cancerslope factor for lead, so it is not possible to evaluate carcinogenic risk. The conclusion that leadcauses cancer in animals is based on experiments with a different form of lead than occurs in thetailings in the Upper Tenmile Creek Mining Area.

Other Contaminants

Adult and child exposures to antimony are several orders of magnitude lower than the NOAEL [13]. No health effects are expected from this exposure.

Child exposures to iron in soil are higher that the health guideline of 0.3 mg/kg/day. Exceeding thehealth guideline does not mean that health effects will occur, however. Severe toxic effects are notlikely with exposures under 30 mg/kg of body weight [8]. Long-term exposure to elevated iron cancause clinical effects such as accumulation of iron in the liver [8]. The calculated exposure doseslikely significantly overestimate actual exposure to iron, because iron may be less available in soiland exposure to soil will be less during the winter months. No health effects due to exposure to ironin the soil are expected.

Exposure to manganese in soil is not expected to cause health effects for children or adults. Theadult exposure is lower than the health guideline. The estimated child dose is two orders ofmagnitude smaller than the LOAEL of 14 mg/kg/day of manganese in water [10]. Actual exposurewill be even lower, since manganese in soil is less available for uptake and soil contact will not be asfrequent during cold weather. Therefore, no health effects are expected.

Mine Tailings and Waste Rock

Waste mining materials are found throughout the site, sometimes in or near residential yards.Current residential development is occurring close by these wastes. Some houses are built directlyon top of graded tailings. Residents, and especially children, may be exposed to very high levels ofcontaminants in these homes. Such exposure could potentially result in acute health effects.

The site database contains information on metals composition of waste rock and tailings found insamples collected throughout the Upper Tenmile Creek Mining Area during 1993 and 1994. Table7 shows contaminants in the waste rock and tailings that were detected at least once above the CV.Some samples contained very high metals levels. Arsenic, for example, was present at a level greater than 10,000 ppm in several samples.

Table 7.

Tailings and Waste Rock Contaminants Above Comparison Values
Contaminant Range in Tailings or Waste Rock in ppm1 Samples > DL2 Samples > CV3 CV in ppm CV Source4
Antimony ND - 827 107 / 118 102 20 RMEG5
Arsenic ND - 121,000 153 / 154 155 / 1536 .5 /207 CREG8 / EMEG9
Cadmium ND - 620 37 / 48 17 10 EMEG9
Iron 2010 - 111,347 186 / 186 111 23,000 R3 RBC10
Lead 23 - 48,700 157 / 157 117 400 SSL11
Manganese 3 - 138,322 124 / 124 7 3,000 RMEG5
Mercury 0.1 - 112 40 / 40 3 23 SSL11
Thallium 8 - 79 125 / 125 126 6 R3 RBC10
Zinc 7 - 82,456 150 / 150 1 20,000 EMEG9
1 ppm = parts per million of chemical in tailings or waste rock. ppm= mg (milligram) per kg (kilogram) of tailings or waste rock
2
DL = detection limit.
3 CV = comparison value.
4 These comparison values are described in Appendix 1.
5 RMEG = remedial media investigation guide.
6 The first number is the number of samples above the CREG and the second is the number above the EMEG.
7
The first number is the CREG and the second is the EMEG.
8
CREG = cancer risk evaluation guide.
9 EMEG = environmental media evaluation guide.
10
R3 RBC = EPA Region 3 risk-based concentration.
11 SSL = EPA soil screening level.

Initial screening considered tailings and waste rock together. However, the small particle size oftailings compared to waste rock makes it much more likely for ingestion of tailings to occur duringoutdoor activities. Therefore, exposure doses were estimated for exposure to tailings only. Iron,manganese, mercury, and zinc were dropped from consideration at this point, because the maximumconcentration in tailings was lower than the CV.

Exposure doses for the contaminants of concern from Table 7 were calculated using the average toestimate chronic exposures and the maximum to estimate acute arsenic exposure for childrenexhibiting pica behavior. Table 8 presents the estimated exposure doses which were higher than thecorresponding health guideline and will be evaluated further. The cadmium exposure dose was lower than the health guideline and was therefore dropped from consideration.

Table 8.

Estimated Exposure Doses and Cancer Risk for Tailings Compared to Health Guidelines for Ingestion1
Contaminant Concentration2 in parts per million (ppm) Estimated Exposure Dose in mg/kg/day3 Health Guideline in mg/kg/day Source of Guideline Cancer Risk
Adult Child
Antimony 43 0.00003 0.0009 0.0004 Oral RfD4 N/A5
Arsenic 555 0.0003 0.009 0.0003 Chronic Oral MRL6 5 in 10,0007
Arsenic- Acute 3,861 - 1.58 0.005 Provisional Acute MRL6 -
Lead 1,226 0.0009 0.02 None10 - No CSF9
Thallium 53 0.00004 0.001 0.00007 RfDo R311 N/A5
1 An explanation of how these exposure doses and cancer risk were calculated can be found in Appendix C. No health guidelines are available for lead. No cancer slope factors are available for antimony, cadmium, lead, or thallium.
2
Average of all tailings data used for chronic calculations; maximum of tailings data used for acute arsenic calculations.
3 mg/kg/day = milligrams of chemical per kilogram of body weight per day.
4 RfD = Reference dose.
5
Not applicable; substance is not classified as a carcinogen.
6 MRL = ATSDR's minimal risk level.
7 Maximum additional lifetime risk of cancer per 10,000 individuals.
8
Based on ingestion of 5 grams of soil in one day by a 10-kg child exhibiting pica behavior (eating of non-food items).
9 No cancer slope factor available.
10 No health guideline; EPA soil screening level equals 400 ppm.
11
RfDo R3 = EPA Region 3 reference dose.

Toxicological Evaluation

It should be noted that the above exposure doses are likely overestimates of actual exposure thatmay occur from tailings. Many of the samples were taken in remote areas which are not easilyaccessible to the general public. Acute exposures for children are highly improbable except in thecase of houses built directly on graded tailings. Exposure to tailings will be less during the wintermonths due to snow cover or to less outdoor activity.

Removal actions carried out by EPA in recent years have reduced the likelihood of exposure to highconcentrations of contaminants. However, procedures are needed for removing newly discoveredwaste piles and testing previously uncharacterized areas at the site.

Arsenic

Exposure of children to arsenic found in tailings materials may cause both short- and long-termhealth effects. Adults exposed to the tailings are not expected to suffer noncancer health effects.However, exposure to arsenic through contact with tailings could increase a resident's chance ofcancer if exposure were for many years.

Acute exposure doses were estimated for children, since some houses are being built directly on topof tailings. The acute dose estimated for children (with and without pica behavior) exposed to themaximum level of arsenic in tailings is higher than the short-term arsenic exposure LOAEL of 0.05mg/kg/day [6]. At the LOAEL, effects such as nausea, vomiting, and diarrhea may occur. Childrenwho are exposed to the average arsenic concentration and do not exhibit pica behavior are not likelyto experience acute health effects.

The chronic child exposure dose based on the average concentration of arsenic in tailings is higherthan the long-term arsenic exposure NOAEL of 0.0008 mg/kg/day [6]. It approaches the chronicLOAEL of 0.014 mg/kg/day [6]. At the LOAEL, effects such as skin changes have been observed.The adult exposure dose to arsenic is lower than the long-term arsenic exposure NOAEL [6]. Nolong-term noncancer health effects are expected to occur in adults based on this exposure.

There is some uncertainty whether health effects will actually occur if there is exposure to theselevels. Both acute and chronic LOAELs are based on exposure to arsenic in water, not solidmaterials. Arsenic is much less available for uptake in the form of tailings. Exposure dosecalculations used the EPA default of 80% relative bioavailability as defined on page 50. However,regional studies have shown that as little as 10 to 50% bioavailability is more reasonable for thistype of contamination [14]. The use of a lower bioavailability would further decrease the effectiveexposure dose.

Based on human epidemiological studies, arsenic is a known carcinogen [6]. Exposure to theaverage arsenic concentration found in tailings (555 ppm) would present a low to moderate increasein lifetime risk of cancer if exposures were daily for 70 years.

Lead

Exposure to lead in tailings alone is not likely to result in health effects in children or adult residents.Please see page 25, however, for a discussion of possible health effects from multiple exposurepathways.

Exposure to lead causes a wide range of effects [9]. The level of lead in blood is a good measure of recent exposure to lead and also correlates well with health effects. Children are especially sensitive to lead, and many of its effects are observed at lower concentrations in children than in adults. Levels of 10 µg/dL and less in children's blood have been associated with small decreases in IQ and slightly impaired hearing and growth. Epidemiological studies have determined soil slope factors which predict blood lead levels to increase from between 0.0007 and 0.0068 µg/dL per part per million (ppm) increase in soil lead level [9]. This wide range resulted from the presence of different sources of lead, exposure conditions, and exposed populations. The health effects associated with such an increase would depend partly on the existing body burden of lead. Using the highest slope factor of 0.0068 µg/dL/ppm, the average lead concentration measured in tailings (1226 ppm) could be expected to increase blood lead levels by 8.3 µg/dL.

The possibility of such an increase actually occurring with this exposure is small. Tailings materialsare typically less bioavailable than other sources of lead in soil, such as fine flue dust [9]. Therefore,the soil slope factor will most likely be much lower than the maximum reported above. Also,children will have lower exposures since they will have minimal contact with site soils throughoutthe winter months.

Animal data indicate that lead is a probable human carcinogen [9]. However, there is no cancerslope factor for lead, so it is not possible to evaluate carcinogenic risk. The conclusion that leadcauses cancer in animals is based on experiments with a different form of lead than occurs in thetailings in the Upper Tenmile Creek Mining Area.

Other Contaminants

There was no data on chronic exposure to thallium. However, both adult and child exposures wereat least an order of magnitude lower than the NOAEL for intermediate exposure [12]. Because theexposure dose is based on the maximum dose and people would actually be exposed to an averageconcentration, no health effects are expected from exposure to thallium.

Adult and child exposures to antimony are several orders of magnitude lower than the NOAEL [13]. No health effects are expected from this exposure.

Surface Water Recreational Pathway

The creeks in the area are attractive for recreational use, and campers and hikers visit the area.Table 7 shows the contaminants of concern screened from surface water sampling performed from1981 to 1999. Arsenic and cadmium were found to be present at levels above the CV. Exposuredoses were calculated for adult and child recreationists, assuming a reasonable maximum of 40 daysper year exposure to the average of the data. Neither contaminant has a predicted exposure dosehigher than the corresponding health guideline, and the estimated cancer risk for arsenic for this exposure scenario is within EPA guidelines.

Table 9.

Surface Water Contaminants Above Comparison Values*
  Range in Water in ppb1 Samples > DL2 Samples > CV3 CV in ppb CV Source4
Arsenic ND - 5400 544 / 834 614 / 8 2 / 3006 CREG7 / EMEG8
Cadmium ND - 702 621 / 993 6 200 EMEG8
* CVs multiplied by 100 because surface water incidental ingestion assumed to be 1/100th of drinking water ingestion.
1
ppb=parts per billion of chemical in water. ppb= mg (microgram) per liter of water.
2 DL = detection limit.
3
CV = comparison value.
4 These comparison values are described in Appendix A.
5 The first number is the number of samples above the CREG and the second is the number above the EMEG.
6
The first number is the CREG and the second is the EMEG.
7
CREG = cancer risk evaluation guide.
8 EMEG = environmental media evaluation guide.

Stream Sediment Pathway

Recreational users of the streams will be exposed to stream sediments. Using data collected from1993 to 1999, several contaminants were found to be present above CVs. However, calculatedexposure doses for this scenario were all below the health guidelines. The low likelihood of exposureto stream sediments makes the contribution to overall exposure from this pathway insignificant.

Road Dust

A section of the dirt road near Rimini was washed out during flooding in the early 1980s and wasfilled using tailings. When normal or construction traffic creates dust, people can possibly breathe incontaminants. EPA and its partners are treating the roads with water and magnesium chloride, whichserves to reduce the amount of dust kicked up by vehicular traffic. This road treatment prevents thecompletion of this exposure pathway currently. However, this pathway was complete in the past andwill be again if the road treatment does not continue. Samples from the road and from a dirtdriveway which also had tailings used as fill were collected during the summer of 2000. We used adust loading factor of 810-6 kg/m3 to estimate the chemical concentration in air from that in soiland assumed that people would only be exposed for a total of one hour per day. Table 10 shows thecontaminants that were detected in the road samples at least once above the corresponding CV.

Incidental ingestion of the road dust is also possible. We have not evaluated this pathway here.Because the road was filled with tailings, the likelihood of health effects is similar to that of the minetailings pathway.

Table 10.

Soil Contaminants Above Inhalation Comparison Values
Contaminant Range in Soil in ppm1 Maximum Air Concentration in (mg/m3)2 CV3 in (mg/m3) CV Source4
Antimony 2 - 439 4 1.5 R3 RBC5
Arsenic 133 - 6485 52 0.0043 CREG6
Cadmium 2 - 279 2 0.0006 CREG6
Manganese 190 - 948 8 0.04 CREG6
1 ppm = parts per million of chemical in soil. ppm = mg (milligram) per kg (kilogram) of soil.
2
mg/m3 = microgram per cubic meter.
3
CV = comparison value.
4 These comparison values are described in Appendix B.
5 R3 RBC = EPA Region 3 risk-based concentration.
6 CREG = cancer risk evaluation guide.

To determine average exposure to road dust through the inhalation route, we assumed that peopleare exposed for 1 hour per day, 350 days per year. Thus, the concentrations were multiplied byexposure factors to account for this lower exposure. For antimony, the corrected air concentrationresulting from this calculation was below the corresponding health guideline. Cancer risk forcadmium was within EPA's acceptable range. These two contaminants were therefore dropped fromfurther consideration. Table 11 summarizes air concentrations above the health guidelines and cancer risk for arsenic and manganese.

Table 11.

Estimated Exposure Doses and Cancer Risk for Road Dust Compared to Health Guidelines for Inhalation1
Contaminant Average Road Material Concentration in ppm2 Air Concentration in (mg/m3)3 Corrected Air Concentration in (mg/m3)4 Health Guideline in (mg/m3) Cancer Risk
Arsenic 2,668 21 0.9 None5 4 in 1,0006
Manganese 542 4 0.2 0.047 N/A8
1 An explanation of how these exposure doses and cancer risk were calculated can be found in Appendix C.
2
ppm = parts per million of chemical in soil. ppm = mg (milligram) per kg (kilogram) of soil.
3 mg/m3 = micrograms per cubic meter.
4
Calculated by multiplying air concentration by (1/24) to account for 1 hour of exposure per day and by (350/365) to account for 350 days of exposure per year.
5
No inhalation health guideline is available for arsenic or cadmium.
6
Not applicable; no inhalation cancer slope factor is available for manganese.
6 Maximum additional lifetime risk of cancer per 1,000 individuals.
7
Source: chronic inhalation MRL/EMEG.
8
Not applicable; no inhalation cancer slope factor is available for manganese.

Toxicological Evaluation

Arsenic

Based on human epidemiological studies, arsenic is a known carcinogen [6]. Assuming people areexposed to the average concentration of arsenic through breathing road dust, a moderate to highincrease in lifetime risk of cancer is predicted.

There are only a few quantitative data on noncancer effects in humans exposed to inorganic arsenicby the inhalation route. However, it appears that such effects are unlikely below a concentration ofabout 100 - 1000 mg/m3 arsenic [6]. Therefore, no noncancer health effects are expected frominhalation of arsenic in road dust.

Manganese

The manganese concentration people may breathe in is higher than the health guideline, but lowerthan the LOAEL for humans of 140 mg/m3 [10]. No health effects are expected.

Multiple Exposure Pathways

People are exposed to contaminants through more than one exposure pathway. Assuming exposuresare additive, the potential for health effects is greater when multiple pathways are considered. Inmost cases, the conclusions from single pathway consideration are not changed when multiplepathways are considered.

For lead exposure, consideration of slope factors for exposure through single exposure pathways(water, soil, or tailings) resulted in predicted blood lead level increases less than 10 µg/dL andtherefore little chance of health effects. However, combining the well water and tailings pathwaysbrings the predicted blood lead level increase above the 10 µg/dL value. This means that childrenwho live in houses built directly on tailings and who drink lead-contaminated well water maypotentially exhibit some health effects from lead exposure. Although the calculations described inthis health assessment used worst-case assumptions, it would be prudent for children in thesecircumstances to be tested for elevated blood lead levels either through the family physician or the local health department.

Potential Exposure Pathways

Some possible exposure pathways are considered incomplete due to uncertainty that people couldactually come in contact with contaminants in reasonable activity scenarios. These potentialexposure pathways are summarized below.

City of Helena Drinking Water

Five intakes for the city of Helena drinking water supply are in the Upper Tenmile Creek MiningArea. Water is treated at the Tenmile water treatment plant before reaching consumers, but the wateris not treated specifically for metals. To date, there is no data indicating that the quality of drinkingwater reaching Helena consumers has been impacted by site contaminants. However, contaminantscould potentially reach the water supply, especially during mudflow events.

Biota

Recreational fishing is especially popular during the spring in the northern (downstream) areas ofTenmile Creek. Fish were sampled from various creek locations in 1998 [15,16]. Contaminantlevels in fish caught in this sampling were too low for occasional consumption to result in healtheffects.

Adit Discharges and Groundwater Seeps

Several adit discharges (water coming out of old mine entrances) and groundwater seeps in the areaare known to be highly contaminated with heavy metals. People in the area are not, however,drinking these waters directly. Because the streams to which these waters contribute were direct,complete exposure pathways, adit discharges and groundwater seeps were not considered completeexposure pathways.

Health Hazard

Potential exposures to arsenic, cadmium, manganese, or zinc in groundwater, to arsenic in soil ortailings located on the site, to arsenic in road dust, or to lead in tailings and groundwater could resultin adverse health effects for children and/or adults if exposure is not reduced or prevented. Based onthe available data and current exposures on the site, ATSDR classifies the Upper Tenmile CreekMining Area as a public health hazard.

Child Health Initiative

ATSDR recognizes that infants and children may be more vulnerable than adults to exposures incommunities faced with contamination of their air, water, soil, or food. This vulnerability is a resultof the following factors:

  • Children are more likely to play outdoors and bring food into contaminated areas.
  • Children are shorter, resulting in a greater likelihood of breathing dust, soil, and heavy vapors that exist close to the ground.
  • Children are smaller, resulting in higher doses of chemical exposure per body weight.
  • The developing body systems of children can sustain permanent damage if toxicexposures occur during critical growth stages.

Because children depend completely on adults for risk identification and management decisions,ATSDR is committed to evaluating their special interests at the Upper Tenmile Creek Mining Areasite as part of the ATSDR Child Health Initiative.

Children living in the community of Rimini may be exposed to site contaminants through drinkingprivate well water or surface water or through accidentally eating tailings materials. Please refer tothe Toxicological Evaluation section for each of these pathways for a discussion of the health effects that are possible for these children.

Community Health Concerns

ATSDR attended meetings of the Upper Tenmile Creek Watershed Steering Committee on May 25,2000 and June 21, 2001. Each meeting was attended by approximately 15 full or part-time residentsof Rimini, as well as an equal number of officials from local, state, and federal organizations.

At the May 2000 meeting, community members were concerned about the quantity of water inTenmile Creek and the state of the fishery and voiced no concerns regarding human health. At theJune 2001 meeting, community members expressed concern about the hazard category assigned tothe site in the public comment version of this document. They felt that categorizing the site as a"public health hazard" was inconsistent with the facts that no one in the community was known tohave been affected by the site contamination and that the site is currently being cleaned up. ATSDRstaff responded to this concern by explaining that one of our requirements in producing a publichealth assessment is assigning a hazard category to the site. Because our analysis showed that healtheffects are possible if the site is not cleaned up, the "public health hazard" category is warranted.This does not mean that it is unsafe for people to live and recreate in the area, but that actions toreduce site contamination are warranted. We agreed to express the community's concern to ATSDRmanagement and convey their suggestion that the category name be changed to be lessinflammatory.

Other community members contacted us by telephone and in written comments to indicate that theyare concerned about the health of themselves and their children. They filter their water and monitortheir children's activities to reduce the chance for contact with site contaminants. They stated thatmost people in the community are concerned and take common sense measures to avoid sitecontaminants. These residents disagreed with the statement in the public comment version of this document that the community had voiced no concerns regarding human health. These concerns are addressed in the response to written comments in Appendix D.


CONCLUSIONS

  1. Some private wells are contaminated with heavy metals. The highest levels of arsenic,cadmium, manganese, and zinc could cause mild to serious health effects, especially forchildren. Other wells appear to have adequate water quality.

  2. Drinking untreated surface water taken from the Tenmile Intake does not appear to result inunsafe exposure to heavy metals, based on the limited data available for that location.However, the limited availability and chance for microbial contamination makes it a poorchoice for use as drinking water. In addition, flood events may result in transientdangerously high metals levels in the creek. Stream water and sediments should not pose a hazard for normal recreational use.

  3. Soils in residential areas are contaminated with heavy metals. Exposure of children toarsenic in soils could cause both short- and long-term health effects. In addition, long-term exposure of adults to arsenic in soils may result in a low to moderate increased risk of cancer.

  4. Tailings and waste rock containing high concentrations of heavy metals are presentthroughout the site. Exposure of children to arsenic in these materials may result in bothshort- and long-term health effects. In addition, exposure of adults to arsenic in tailings andwaste rock for many years may result in an low to moderate increased risk of cancer.Children who live on tailings or waste rock and drink groundwater may be exposed toenough lead to cause health effects.

  5. Fill material used to repair the road contains high levels of contaminants. If not kept under control, road dust has the potential to expose people to arsenic at a level that may result in a moderate to high increased risk of cancer through inhalation.

Because contaminants present in private wells, soils, and tailings in the Upper Tenmile CreekMining Area are high enough to cause health effects to residents,ATSDR classifies Upper Tenmile Creek Mining Area a public health hazard. Potential exposures to arsenic and other heavy metals could result in adverse health effects if exposure is not reduced or prevented.


RECOMMENDATIONS

  1. ATSDR supports EPA's action to provide people whose well water has been shown to becontaminated with heavy metals at levels above the MCL with treatment systems or analternate water source. Metals levels in private wells should continue to be monitoredregularly.

  2. Although the limited data suggest that surface water from Tenmile Creek has littlecontamination with heavy metals, high metals levels are possible during floods and other events. ATSDR recommends that people in the area not drink untreated water.

  3. ATSDR recommends that soils in residential areas be removed or remediated to reduce the chance for exposure of children to hazardous levels of arsenic.

  4. ATSDR recommends that appropriate removal and remedial actions, such as EPA and other agencies are carrying out, continue in order to reduce the chance of exposure to tailings on the site. ATSDR recommends that children under 6 years old and pregnant women residing in houses built on tailings have their blood lead levels checked by a physician or the local health department.

  5. ATSDR recommends that appropriate removal and remedial actions of contaminated roadfill or a plan for permanent control of road dust be implemented to prevent inhalationexposures from dust.

PUBLIC HEALTH ACTION PLAN

The Public Health Action Plan for the Upper Tenmile Creek Mining Area NPL Site contains adescription of actions to be taken by ATSDR at the site after the completion of this public healthassessment. The purpose of the Public Health Action Plan is to ensure that this public healthassessment not only identifies public health hazards, but provides a plan of action designed tomitigate and prevent adverse human health effects resulting from exposure to hazardous substancesin the environment. Included is a commitment on the part of ATSDR to ensure the plan'simplementation. The public health actions to be implemented are as follows:

A fact sheet on the findings of this public health assessment will be developed and distributed tocitizens living on or near the site.

ATSDR will reevaluate and expand the Public Health Action Plan as needed. New environmental, toxicological, or health outcome data, or the results of implementing the above recommendations or proposed actions may determine the need for additional actions at this site.


PUBLIC COMMENTS

The Upper Tenmile Creek Mining Area Public Health Assessment was released April 24, 2001 andwas available for public review and comment at the EPA Region 8 offices in Helena, MT. The PHAwas also sent to people on EPA's mailing list living in the Rimini community and several federal,state, and local officials. The public comment period was announced in local newspapers and ranuntil June 8, 2001 . At the request of several community members, the public comment period wasextended to the end of June 2001. All the comments received, including our responses, are listed in Appendix D.


SITE TEAM

Authors of Report
Jill J. Dyken, Ph.D., P.E.
Environmental Health Scientist
Superfund Site Assessment Branch
Division of Health Assessment and Consultation

John R. Crellin, Ph.D.
Senior Environmental Epidemiologist
Superfund Site Assessment Branch
Division of Health Assessment and Consultation

Regional Representatives
Dan Strausbaugh
Regional Representative
ATSDR Region 8 Montana Office
Regional Operations

Glenn Tucker, Ph.D.
Senior Regional Representative
ATSDR Region 8
Regional Operations

Community Involvement
Dan Holcomb
Health Communications Specialist
Community Involvement Branch
Division of Health Assessment and Consultation


REFERENCES

  1. CDM Federal Programs Corporation. Draft preliminary remedial investigation report, Upper Tenmile Creek Mining Area Superfund site. Prepared for the U.S. Environmental Protection Agency. Denver, CO: 2000 April.

  2. Pioneer Technical Services, Inc. Final site inspection report for the Tenmile Creek site.Prepared for the Montana Department of Health and Environmental Sciences. Helena, MT:1995 April.

  3. CDM Federal Programs Corporation. Draft data summary and usability report--UpperTenmile Creek Mining Area site. Prepared for US Environmental Protection Agency RegionVIII. Golden, CO: 2000 March 2.

  4. TetraTech EM. Microsoft Access database for Upper Tenmile Creek Mining Area(tenmile.mdb). Provided on CD-ROM. Helena, MT: 2001 February.

  5. US Environmental Protection Agency. Exposure factors handbook. Washington, DC: USEnvironmental Protection Agency. Office of Research and Development. EPA/600/C-99/001.1999 February.

  6. Agency for Toxic Substances and Disease Registry. Toxicological profile for arsenic: update.Atlanta: US Department of Health and Human Services, Agency for Toxic Substances andDisease Registry, 2000.

  7. Agency for Toxic Substances and Disease Registry. Toxicological profile for cadmium: update.Atlanta: US Department of Health and Human Services, Agency for Toxic Substances andDisease Registry, 1999.

  8. Amdur, Mary O.; Doull, John; and Klaassen, Curtis (Eds.). Casarett and Doull's Toxicology: The Basic Science of Poisons. 4th Ed. Pergamon Press, New York: 1991.

  9. Agency for Toxic Substances and Disease Registry. Toxicological profile for lead: update.Atlanta: US Department of Health and Human Services, Agency for Toxic Substances andDisease Registry, 1999.

  10. Agency for Toxic Substances and Disease Registry. Toxicological profile for manganese:update. Draft for public comment. Atlanta: US Department of Health and Human Services,Agency for Toxic Substances and Disease Registry, 1997.

  11. Agency for Toxic Substances and Disease Registry. Toxicological profile for zinc: update.Atlanta: US Department of Health and Human Services, Agency for Toxic Substances andDisease Registry, 1994.

  12. Agency for Toxic Substances and Disease Registry. Toxicological profile for thallium: update.Atlanta: US Department of Health and Human Services, Agency for Toxic Substances andDisease Registry, 1992.

  13. Agency for Toxic Substances and Disease Registry. Toxicological profile for antimony: update.Atlanta: US Department of Health and Human Services, Agency for Toxic Substances andDisease Registry, 1992.

  14. Casteel, et al. Relative bioavailability of arsenic in mining wastes. Prepared for US Environmental Protection Agency Region VIII, Montana Office. Helena, MT: 1997 December.

  15. Torma, Lazlo (MSU). Memorandum to Montana Fish, Wildlife and Parks concerning results of fish tissue sampling. Bozeman, MT: Montana State University (MSU). February 4, 1999.

  16. Skaar, D (MFWP). Letter to R. Wieland of URS Operating Services concerning locations of fish sampling. Helena, MT: Montana Fish, Wildlife, and Parks (MFWP). February 17, 1999.

1. ATSDR Staff (John Crellin and Jill Dyken) visited the site on May 25, 2000. Information obtained during this visit is described in the pertinent sections of this document.




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  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #