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PUBLIC HEALTH ASSESSMENT

KENNECOTT (NORTH ZONE)
MAGNA, SALT LAKE COUNTY, UTAH


SUMMARY

The Kennecott--North Zone site is west of Salt Lake City Utah, along and near the shore of GreatSalt Lake. The Agency for Toxic Substances and Disease Registry (ATSDR) staff toured theseveral operable units the U.S. Environmental Protection Agency (EPA) tentatively has identifiedto comprise the site; staff also reviewed data available for the site area. Those activitiesdisclosed that community members and area visitors might be exposed in the vicinity of thecommunity of Magna (Operable Unit-9) and Tooele Valley (Operable Unit-19) and also by GreatSalt Lake Park. Those exposure situations considered one or more of the following:

  • Process equipment contaminant releases to ambient air (principally from the stack of thesmelter operating on site), and subsequent deposition,
  • Tailings pond particulate releases to air and subsequent deposition,
  • Process unit and waste contaminant releases to groundwater.
  • Nondefinable sources, and
  • Naturally occurring metals in environmental media.

The following is a summary of conclusions and recommendations.

  • Air exposure---Exposure situations for the vicinity of Magna (includes Great Salt Lake Park)appear to pose no public health hazard. Air quality metals data in Tooele Valley areinsufficient to evaluate health issues. ATSDR recommends more of the samples being takenthere be analyzed for metals. ATSDR recommends that ambient air sampling be conductednear a chemical plant (about 2 miles south of Magna) that is not associated with the site toconfirm whether releases noted in EPA's Toxic Chemical Release Inventory pose a publichealth hazard to residents.

  • Soil exposures--Exposure situations for the Magna vicinity appear to pose no public healthhazard. Tooele Valley soils situations are being addressed in the companion Public HealthAssessment for the Kennecott, South Zone site. No recommendations needed.

  • Surface Water Exposures--Exposure situations at Great Salt Lake Park appear to pose nopublic health hazard. No recommendations needed.

An earlier version of the document was made available for public review and comment. Publiccomment information is provided in an appendix.


INTRODUCTION

In this public health assessment, the Agency for Toxic Substances and Disease Registry(ATSDR) evaluates the public health significance of the Kennecott--North Zone site in thevicinity of Magna, Utah. More specifically, ATSDR has reviewed available environmental andhealth outcome data and community health concerns to determine whether adverse health effectsare possible. In addition, evaluations considered whether actions are needed to reduce, prevent,or further identify the possibility for site-related adverse health effects. ATSDR, in Atlanta,Georgia, is one of the agencies of the U.S. Public Health Service. ATSDR is required by theSuperfund law (Comprehensive Environmental Response, Compensation, and Liability Act of1980 [CERCLA], as amended by the Superfund Amendments and Reauthorization Act of 1986[SARA]), to conduct public health assessments of sites proposed for the National Priorities List(NPL). The U.S. Environmental Protection Agency (EPA) proposed that the Kennecott--NorthZone site be added to the NPL in January, 1994. The site area, including the towns of Magna and Tooele, is shown on  Figure 1 (Appendix A)

Background--Overview

The Kennecott--North Zone site is comprised of areas on or near Kennecott Corporation propertynear the south shore of Great Salt Lake. At its Magna operations, Kennecott processes ore takenfrom its pit about 15 miles south and produces copper and other metals. Ore tailings are retainedin a pond near the process facilities. Smelting and associated operations at Magna began in1905 and have been conducted under multiple owners. Kennecott purchased the facilities in1959. The company has continued to reduce contaminant releases over the years by improvingthe facility smelter and process equipment, process methods, and waste handling procedures.

EPA provided ATSDR a list identifying six operable units (OU) that tentatively comprise thenorth zone: OU-8--Wastewater Treatment Plant Sludge Ponds, OU-9--Magna Soils,OU-13--Facility Smelter and Acid Plant, OU-14--Refinery, OU-15--Magna Tailings Pond, andOU-19--Fallout in Tooele Valley. Operable unit locations (approximate) are shown on Figures 2and 3 (Appendix A). Appendix B summarizes background information about the operable units. EPA advised ATSDR staff that they may add or delete operable units over time as moreinformation becomes available or as Kennecott initiates remediation and improves processes andequipment. Information about demographics, land use, and natural resources use for the site area also is in Appendix B.

Public Health Evaluation Methodology and Scope--Overview

ATSDR evaluated public health implications through a sequential process that considerscontaminant concentrations, plausible human exposure pathways, health concerns expressed bycommunity members, and plausibility of related carcinogenic and noncarcinogenic health effects.

Evaluations included a visit to the operable units(1) and site vicinity to gain an understanding ofthe geographic, physical, and demographic settings. Exposure evaluations considered multiplecontaminant origins (and releases that occurred over a period of multiple facility owners),including:

  • Process equipment contaminant releases to ambient air (principally via the facility's smelterstack), and subsequent deposition
  • Tailings pond particulate releases to air and subsequent deposition
  • Process unit and waste contaminant releases to groundwater
  • Undefinable sources
  • Naturally occurring metals in environmental media

Those evaluations and observations aided staff in identifying community members and visitorsthat might experience exposure. That information, together with environmental sampling data,was used in further evaluations to decide whether exposures are likely to have any associatedpublic health implications. Further description of major components of the evaluation process is given in Appendix C.

The results of the evaluation process showed several key exposure situations occur in the vicinityof Magna (OU-9), Tooele Valley (OU-19), and Great Salt Lake Park that warrant discussion inthis assessment. Those exposure situations and the resulting public health hazard classificationdetermined for each are listed in Table 1. The locations where they occur are shown on Figures 2 and 3 (Appendix A).

Table 1.

KEY EXPOSURE SITUATIONS AND THEIR PUBLIC HEALTH HAZARD
Exposure SituationPublic Health HazardClassification
Airborne Contaminants
  • Magna Vicinity (OU-9)
  • Great Salt Lake Park
  • Northern Tooele Valley (OU-19)
  • No Apparent Health Hazard
    No Apparent Health Hazard
    Insufficient Data to Classify Hazard
    Soil Contaminants
  • Magna (OU-9)
  • No Apparent Health Hazard
    Surface Water Contaminants
  • Great Salt Lake
  • No Apparent Health Hazard

    Operable Units 8, 13, 14, and 15 are not addressed further in this assessment because thecommunity has no or very limited incidental access, and any exposures that might occur at thoseoperable units to workers (e.g., employees, contractors) or plant visitors would be within thejurisdiction of state and federal occupational health agencies.

    ATSDR also evaluated data for surface water in the Utah and Salt Lake Canal, sediment from theC-7 ditch and Great Salt Lake, and surface water in the C-7 ditch; these will be not describedfurther because we concluded that human exposures are not significant. Our evaluation ofMagna area drinking water supplies also indicated that there are no significant human exposures. A summary of this evaluation can be found in Appendix D. The evaluations conducted for soilsexposures in the Magna vicinity led ATSDR to conclude that soils at Great Salt Lake Park arenot likely to be a substantive contaminant exposure source for park visitors and workers. Drinking water supplies and surface soils in Tooele Valley are being addressed in another publichealth assessment (Kennecott--South Zone). Airborne-related contaminant exposures areevaluated for the site vicinity (e.g., for the Magna and Tooele Valley operable units and for GreatSalt Lake Park). The assessment does not address greater Salt Lake City's occasionally adverseair quality and exposures from urban and industrial sources of which site-related releases havebeen considered a contributor under certain atmospheric conditions (1).

    PUBLIC HEALTH EVALUATION OF AIRBORNE CONTAMINANTS

    A. Overview

    The possibility of public health impact by air-borne contaminants is evaluated in this portion ofthe assessment for three exposure situations (Magna vicinity, Great Salt Lake Park, and TooeleValley). Table 2 summarizes the results of these evaluations.

    The evaluation results lead ATSDR to conclude that the Magna and Great Salt Lake Park airexposure situations pose no apparent public health hazard. There are insufficient data toproperly evaluate the Tooele Valley situation.

    Table 2.

    EXPOSURE TO AIR CONTAMINANTS*
    SituationsKey**
    Contaminants
    Exposed
    Population***
    Route of
    Exposure
    Frequency of
    Exposure
    Public Health
    Classification
    MagnaVicinityArsenicCadmiumAbout18,000InhalationDaily No Apparent HealthHazard
    Great Salt
    Lake Park
    ArsenicCadmiumAbout676,000InhalationInfrequent No ApparentHealthHazard
    TooeleValleyArsenicCadmiumAbout20,000Inhalation Daily InsufficientData
    * For each of the exposure situations, the facility smelter appears to be a primary source of contaminants.
    ** Key Contaminants--contaminants which initial evaluations showed hadsome potential to be a public health hazard.
    *** Note: the numbers shown focus on the subject operable units and nearbypopulations and do not include those in the greater Salt Lake City area whereoccasionally adverse air quality and exposures occur from a wide range ofurban and industrial sources of which site-related releases have beenconsidered a contributor under certain atmospheric conditions.


    B. Background--Overview

    Over the years, smelting and its associated operations near Magna (Figure 2, Appendix A) havereleased metals, acids, and gases that have had a range of effects on ambient air quality nearbyand in the region. The rates of contaminant releases have diminished substantially as Kennecottmodified process systems, control equipment, and operating procedures. Former operations atInternational Smelting east of the city of Tooele, in Tooele Valley, once also contributedcontaminants to air (Figure 3, Appendix A). Additional less substantive sources of airbornemetal and acid contaminants may occur in the area.

    C. Environmental Contamination

    Ambient air sampling data were reviewed and several contaminants were selected for further,more detailed, evaluation of public health significance. A description of the process for selectingthe several contaminants is provided on page 37 in Appendix C. Those several were furtherevaluated, yielding two that were identified as key contaminants, as summarized below. Readersare advised to read the public health implications section before making any conclusions aboutthe air contaminant levels. As described in Appendix C, finding a contaminant level above the comparison value only means that further evaluation is needed.

    Arsenic and cadmium were found to be key contaminants for all three exposure situations. Copper, lead, zinc, particulates, and sulfur dioxide were also detected in air; but concentrations are not great enough to warrant further evaluation.

    Magna Vicinity

    Table 3 summarizes average concentration data obtained in Magna for key air contaminants,arsenic and cadmium. Other air data in Magna in the 1990s showed respirable particulates(PM10--particulates that are 10 microns in diameter or less) and sulfur dioxide to be withinregulatory limits (Table 9A, Appendix E) (2,3,4). For the period of 1985 through 1989, 10 of the1061 observations for particulate levels exceeded the 24-hour regulatory value (5). Laboratoryanalyses between 1990 and 1994 showed relatively low metals concentrations in Magna and inthe adjacent West Valley City to the east (Table 9B, Appendix E) (4). Measurements at WestValley City may nearly represent background air values, i.e., the area may not be affected bywind-blown tailings and only modestly affected by releases from the facility's smelter stack.

    Table 3.

    KEY CONTAMINANTS FOR MAGNA AIR EXPOSURE SITUATION1
    ContaminantAverageLevel for 19942Average Levelfor 1990 -19933ComparisonValue
    (see AppendixC)
    Source
    Arsenic0.017 µg/m30.022 µg/m30.0002 µg/m3CREG4
    Cadmium0.001 µg/m30.005 µg/m30.0006 µg/m3CREG4
    1 There is a more detailed list of contaminants in Tables 9A and 9B starting onpage 43 in Appendix E. The process for selecting contaminants is described inAppendix C starting on page 37.
    2 Average for 256 samples from two Magna locations in 1994; in micrograms ofcontaminant per cubic meter of air
    3 Average for 2147 samples from two Magna locations in 1990-93; in microgramsof contaminant per cubic meter of air
    4 CREG is cancer risk evaluation guide. See Appendix C for an explanation.


    Great Salt Lake Park

    Table 4 summarizes average concentration data obtained in the park vicinity for keycontaminants, arsenic and cadmium. Air sampling in 1988 and in the 1990s at the county boatdock showed PM10, sulfur dioxide, and metals to be at relatively low levels in the park vicinity (Tables 10A and 10B, Appendix E) (2,4,6).

    Table 4.

    KEY CONTAMINANTS FOR GREAT SALT LAKE AIR EXPOSURE SITUATION1
    ContaminantAverage Level for 19942ComparisonValue
    (see Appendix C)
    Source
    Arsenic0.046 µg/m30.0002 µg/m3CREG3
    Cadmium0.001 µg/m30.0006 µg/m3CREG3
    1 There is a more detailed list of contaminants in Tables 10A and 10B starting onpage 44 in Appendix E. The process for selecting contaminants is described inAppendix C starting on page 37.
    2 Average for 164 samples taken at Great Salt Lake Park in 1994;. in microgramsof contaminant per cubic meter of air
    3 CREG is cancer risk evaluation guide. See Appendix C for an explanation.


    Tooele Valley

    Ambient air metals data for the valley are quite limited. Only nine samples taken in recent yearsin Grantsville were available to characterize ambient air metals data in the valley. These are fartoo few to permit an evaluation of possible health impact. Analyses for PM10 at Erda andGrantsville in parts of 1992 and 1993 showed levels to be within regulatory limits except for one"exceptional" event at Grantsville during which the maximum 24-hour limit was exceeded(Tables 11 and 12, Appendix E) (2,7). Metals concentrations reported for the nine samples takenat Grantsville in 1993 and 1994 also are low (Table 13, Appendix E) (8).

    Sulfur dioxide sampling has been conducted in Tooele Valley near Mills Junction, which islocated about 4 miles north of Erda and about 7 miles southwest of the active smelter. Data for 1981 through 1984 show the levels are well within regulatory limits (Table 11, Appendix E) (9).

    D. Exposure Pathway Analyses

    Magna Vicinity

    The approximately 18,000 residents of Magna, according to the 1990 census (10), are beingexposed to a variety of airborne contaminants, primarily arsenic and cadmium, on a daily basis. The approximate boundaries of Magna, an unincorporated community, are shown on Figure 2. Ninety four percent of the population is of the white race.

    Based on five years of monitoring data at two sampling stations (at an active school and a formerschool), arsenic levels varied from nondetect to 0.3 µg/m3 with an average of 0.021 µg/m3, andcadmium from nondetect to 0.1 µg/m3 with an average of 0.0046 µg/m3. Residents of the Magnaarea have been exposed to arsenic, cadmium, and other contaminants since the facility's smelterbegan operation in the very early 1900s. Concentrations in the air have been decreasing throughtime. Individuals who work in or visit Magna would be exposed only for that period of time they are in the Magna area.

    Great Salt Lake Park

    Great Salt Lake Park lies north of the Kennecott facilities and Interstate 80, and occupies about3½ miles of shoreline (Figure 3). The individuals with the greatest exposure would be the parkstaff who would be exposed 8 hours a day 5 days a week. Another group being exposed wouldbe the users of the 300 craft docked in a county boat harbor by the park. Maximum exposurefrequency for these individuals would probably be 8-9 times a month for 8-9 months a year. Parkvisitors (676,000 in 1994) are exposed to arsenic, cadmium, and other contaminants while there. A portion of the visitors are likely to make multiple visits during a season.

    Based on a year's monitoring data (164 samples), arsenic levels at one sampling location variedfrom nondetect to 0.178 µg/m3 with an average of 0.046 µg/m3, and cadmium from nondetect to0.007 µg/m3 with an average of 0.001 µg/m3.

    Tooele Valley

    The 7,000 - 10,000 people that live in the northern Tooele Valley area, are being exposed tounknown concentrations of arsenic, cadmium, and other contaminants. Another 10,000 to15,000 farther south in the valley also likely are exposed periodically. Tooele Valley extendswest and south from Great Salt Lake and lies between the Stansbury Mountains (on west) andOquirrh Mountains (on east) (Figure 3). The mountains rise a few thousand feet above the valleyfloor. Communities in the northern part of the valley are nearest the facility's smelter. Theseinclude Erda (population 1,113), Stansbury Park (population 1,049), and Lake Point (a residentestimated the population to be 400). Those communities are about 9, 6, and 2½ miles from thefacility's smelter, respectively. Grantsville, the largest community in the northern valley(population 4,500), is located about 15 miles from the facility's smelter. Tooele, farther south inthe valley, has a population of about 14,000. About 93 percent of the area's population is of the white race (10).

    ATSDR has been able to identify only nine samples from Tooele Valley (samples taken atGrantsville) that were analyzed for metals. This number of samples is insufficient to permitfurther evaluation of metals in this exposure situation. There are extensive data on sulfur dioxidelevels. The levels identified are all below the permissible limits established by EPA, and thus will not be evaluated further.

    E. Public Health Implications

    Public health implications decisions made in the public health assessment process primarily arebased on toxicological evaluations that compare exposure dose (i.e., the amount of a substanceindividuals in an exposure pathway are exposed to daily) to appropriate health guidelines forcarcinogenic and noncarcinogenic effects. There are health guidelines for carcinogenic effectsfor arsenic and cadmium; for noncarcinogenic effects there is a health guideline for cadmium butnot for arsenic. The methodology for calculating exposure doses and cancer risk and the resultsof those calculations (Table A) are on pages 51 and 53, respectively.

    Magna Vicinity

    It is unlikely that the exposures to arsenic, cadmium, and other contaminants in Magna Vicinityair will result in health effects in area residents. Levels of arsenic and cadmium identified insampling in Magna since 1990 are considered too low to result in noncarcinogenic effects or asignificant increase in risk for cancer.

    We evaluated continuous daily 70-year exposures to the mean and maximum levels of arsenicand cadmium in Magna Vicinity air, both separately and combined. We also evaluated theexposure Magna residents would receive if they lived in Magna and worked at the Great SaltLake Park. Both the mean and maximum cadmium levels for any of these exposure scenarios areat least 30 times lower than the health guideline for cadmium. This indicates that there is little orno chance that these levels could cause any noncarcinogenic health effects. There is no healthguideline for air exposures to arsenic, so we compared air levels to the lowest observed adversehealth effects noted in long-term exposures of workers (11). The mean arsenic level is about2,400 times lower and the maximum arsenic level about 170 times lower than the lowestobserved health effects level. Thus there is little or no chance that the measured air levels would result in adverse health effects.

    Long-term exposures to the mean air levels of arsenic or cadmium separately or together do notsignificantly increase the expected lifetime risk of cancer of three in ten that an individual has. Arsenic is considered a known human carcinogen, based on human epidemiological studies (11). Cadmium is a probable human carcinogen based on animal data (12).

    Great Salt Lake Park

    It is unlikely that the exposures to arsenic, cadmium, and other contaminants in Great Salt LakePark air will result in health effects in Park staff and visitors. Levels of arsenic and cadmiumidentified in sampling in the Great Salt Lake Park in 1994 are considered too low to result innoncarcinogenic effects or a significant increase in risk for cancer.

    We evaluated exposures of Great Salt Lake Park staff members who are exposed 8 hours a day, 5 days a week, 50 weeks a year for 30 years to the mean and maximum levels of arsenic andcadmium in Great Salt Lake Park air both separately and combined. This staff exposure wouldbe much greater than for park visitors, and thus any conclusions about the Park staff would alsoapply to Park visitors. Both the mean and maximum cadmium levels for any of these exposurescenarios are at least 30 times lower than the health guideline for cadmium. This indicates thatthere is little or no chance that these levels could cause any noncarcinogenic health effects. Aswith the Magna Vicinity exposure situation, we compared air levels to the lowest observedadverse health effects noted in long-term exposures of workers (11). The mean arsenic level isabout 1,100 times lower and the maximum arsenic level about 280 times lower than the lowestobserved health effects level. Thus there is little or no chance that the measured air levels would result in adverse health effects.

    Long-term exposures to the mean air levels of arsenic or cadmium separately or together do notsignificantly increase the expected lifetime risk of cancer of three in ten that an individual has. Arsenic is considered a known human carcinogen, based on human epidemiological studies (11). Cadmium is a probable human carcinogen based on animal data (12).

    F. Conclusions, Recommendations and Public Health Actions

    1. Conclusion--ATSDR believes the Magna and Great Salt Lake Park air exposure situationspose no apparent public health hazard.

    2. Conclusion--Air quality metals data are not sufficient to properly evaluate the Tooele Valley situation.

      Recommendation--ATSDR recommends that air samples being taken by the state in Grantsvillebe analyzed more frequently for arsenic, cadmium, and other metals for the next year or two. Those data, then, should be evaluated to decide whether there may be an associated public health threat.

    3. Conclusion--Although the organic chemical releases from an industrial facility about 2 milessouth of Magna reported in EPA's Toxic Chemical Release Inventory (see Appendix C) are notassociated with the proposed NPL site and the focus of this assessment, those releases appear to be substantial in quantity and should be evaluated.

      Recommendation--ATSDR recommends that ambient air sampling be conducted near the plantto confirm whether releases pose a public health hazard to residents.

    4. Public health actions--Public health action information for all exposure situations issummarized in the Public Health Actions Section, found on Page 21.

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