PUBLIC HEALTH ASSESSMENT
KENNECOTT (NORTH ZONE)
MAGNA, SALT LAKE COUNTY, UTAH
LIST OF FIGURES
EPA reports this operable unit includes the wastewater treatment plant and four associated sludgeponds and any areas impacted by the sludge ponds. The facilities are on Kennecott property. Most pond segments are unlined; three of the four ponds have reached capacity and are out ofservice. The treatment plant is slated to terminate operation soon. The treatment plant, which isnorth of the Kennecott refinery, is on the northeast corner of the intersection of State Highways201 (2100 South Street) and 202. Treated effluent is piped to the Magna Tailings Pond. ATSDRobserved that plant components are fully fenced. Two sludge ponds are north and east of thehighway intersection and lie between the highways and the Magna Tailings Pond. The other twoponds lie west of State Route 202 and south of Interstate 80. ATSDR's observations indicate thepotential for trespass to the plant and pond areas is small because of the fence system, terrainfeatures, and remoteness. The sludge will be permanently disposed in a lined repository, and thewaste water treatment plant will become obsolete with completion of the new smelter. ATSDRobserved that the nearest residence(s) are to the west about ¾ miles away in the community ofLake Point, in Tooele County, and about 2½ miles to the east, in Magna. The shore of Great SaltLake and the Great Salt Lake visitor center are north of Interstate 80, about ½ mile north of the nearest pond.
OU-9 Magna Soils
Magna is an unincorporated community of nearly 18,000 residents located principally south ofState Route 201 (2100 South Street) and immediately east of Kennecott's production area (Figure2). Discussions with citizens indicate that the community has experienced wind-drivenparticulates from the Magna Tailings Pond on the north side of Route 20l. A resident reportedthat wind-driven tailings particles sometimes were quite noticeable while Kennecott was notoperating in the mid 1980s. Data (described elsewhere) also indicate that releases (gaseous andparticulate) from the facility's smelter, and probably other process facilities, have impacted thearea. Transported particles deposited in the community and became a component of surfacesoils.
The smelter, acid plant, and related process facilities are on the lower slope of the OquirrhMountain range, immediately south of State Route 201 . EPA has included several waste storageand disposal areas and rail and truck maintenance facilities in the operable unit. All of theoperable unit facilities are on Kennecott property. The largest of the waste areas appears to be aslag pile (approximately 175 acres) and adjacent ponds that lie in an area bounded by State Route201 (on the south) and Interstate 80 (on the north). The slag is being recovered for constructionpurposes. A dike and Interstate 80 separate the ponds from Great Salt Lake. Pond sedimentswill be cleaned up after storm water management modernization is completed. The process areais contained behind a fence along State Route 201; at the east end of the process area, the fenceextends southward from Route 201 along the Magna boundary. ATSDR's observations indicatethe potential for trespass to the process and waste areas is small because of the extensive fencesystem, guard gates, terrain features, and remoteness. Some contaminated soils and wastes havebeen removed from the smelter/acid plant area; a contaminated plume underlying a portion of theproperty also is being remediated. Releases occur to air primarily from the smelter stack. Potential also exists for releases from the slag pile and ponds to groundwater. The smelter stackis about 2½ miles east of the Lake Point community in Tooele County, about 5 miles west ofMagna, and ½ mile south of Great Salt Lake, the County Boat Harbor, and Silver Sands Beach.
Facilities, fuels, and operations have changed substantively since smelting began in 1905. Kennecott bought the smelter in 1959 and have since modified and improved major components. A major refit in 1978 modified the gas handling equipment to capture fugitive emissions,constructed a 1,200 foot stack, installed a computerized emission control system, and providedadditional acid plants to increase sulfur capture. Slag now is being processed for copper recoveryin a slag concentrator. The tailings from the slag concentrator are deposited in the MagnaTailings Pond. New smelter and acid plant systems now under construction are expected tofurther reduce releases to the environment. Contaminated soil encountered within the smelterconstruction area has been removed.
The refinery operable unit includes the refinery, a former waste evaporation pond, and anunderlying contaminated groundwater plume. The facilities are on Kennecott property south ofState Route 201 and are contained behind the process area fence. The refinery is about 4½ mileseast of the Lake Point Community, about 2½ miles west of the nearest Magna residences, and 1¾miles south of Great Salt Lake. ATSDR observations indicate that trespass potential to the areais small because of the extensive fence system, guard gates, terrain features, and remoteness. Therefinery was completed in 1950 and has since been modified and expanded. Process wastewateris pumped to the wastewater treatment plant (OU-8). The former evaporation pond, whichoperated in the 1950s and 1960s, is unlined and is the suspected source of underlyinggroundwater contamination. Additional discharges of spent solutions occurred as seepagethrough the basement floor of the refinery. Contaminated residues have been removed as part ofongoing operations or refinery modernization. Contaminated soils have been identified andeither removed, contained, or controlled. ATSDR was told that Kennecott plans to remove thesediments from the pond area. Kennecott's process modifications, component replacements, andnew construction are expected to deter future releases.
The Magna Tailings Pond operable unit includes the pond, a landfill within the pond, the tailingsslurry pipeline, the C-7 Ditch (discharges to Great Salt Lake at a remote section of Great SaltLake Park), and the Diving Board Tailings. The facilities are wholly on Kennecott property,except for a short segment of the C-7 ditch between Interstate 80 and the lake. ATSDRobservations indicate that trespass potential to Kennecott property in these areas is small becauseof the extensive fence system, terrain features, and remoteness.
The pond was about 2 square miles in area in 1907 and has been enlarged several times. Itpresently is about 170 feet high and covers about 5,700 acres; Kennecott reports they have plansfor near-term expansion toward the north. The impoundment receives tailings in a slurry fromseveral Kennecott facilities including the Copperton Concentrator, Magna Concentrator and theSlag Concentrator. It also receives fly ash from the Kennecott power plant and liquid effluentfrom their wastewater treatment plant. Kennecott reports the transportation routes for thesematerials are located totally within Kennecott property, except where the slurry pipeline crossesState Route 201. Some severe episodes of wind-blown dust from the pond has been reported byMagna residents--especially in the mid 1980s when operations were suspended. Elevated metalsconcentrations also have been documented in downwind air samples. An EPA document saysthat metals detected in shallow- and medium-depth monitoring wells located north and east of thepond suggest a release to groundwater also has occurred. Multiple measures have beenimplemented to counter dust and slope erosion, including sprinklers, chemical and mulchstabilization products, wind fencing, and vegetative cover. The State now requires Kennecott tokeep 90 percent of the tailings pond wet at all times. This has been accomplished byconstructing a tailings manifold system that allows tailings slurry to be discharged from manypoints on the pond perimeter. Aerial photos are taken frequently to confirm that the state'srequirements are being met. The tailings slurry pipeline, which has experienced a few ruptures,is in the process of being lined with rubber. Kennecott also has initiated measures to increasedike stability near Magna; measures include slope flattening and internal slope dewatering.
Ponded water is removed from the facility via a combination of evaporation, recycling, anddischarge to the C-7 Ditch which partially bounds the pond. The C-7 ditch discharges to GreatSalt Lake at a remote section of Great Salt Lake Park between the visitor center and SaltaireBeach.
Various demolition debris have been placed in the impoundment landfill, which is located on thewestern side of the pond. The full nature of those wastes is not known. In 1992, landfill covermaterial found to contain high lead concentrations was removed and deposited at the USPCI.
ATSDR observed that the closest single residence is about ¼ mile east of the pond; the nearestsubdivision is about ¼ mile to the southeast. The community park and golf course, on the south side of State Route 201, is a few hundred feet away.
The Diving Board Tailings consists of 8-acre and 13-acre impoundments located along the southside of State Highway 201 within the fenced process area. One impoundment is within a fewhundred feet of the Magna Golf Course property. Kennecott reports they are completingrelocating the tailings to the Magna Tailings Pond. The company then plans to use the area tocapture localized storm water runoff. A earthen basin will be used to retain anticipated process tailings discharges and recycle them to the Magna Tailings Pond.
OU-19 Fallout in Tooele Valley
This operable unit pertains to airborne releases from the facility's smelter stack that may affectcommunities in Tooele Valley (Figure 3). The nearest community Lake Point, is about 2½ mileswest of the facility's smelter stack, and several others (Stansbury Park, Erda, Tooele City,Grantsville) are within 15 miles in a southwesterly direction.
Demographics, Land Use, and Natural Resources Use
Magna is an unincorporated community of approximately 17,800 population, according to the1990 census (10); the approximate boundaries ATSDR inferred from census data are shown onFigure 2 in relation to other area features and West Valley City. Ninety four percent of the population is of the white race.
Our staff's observations indicate that essentially all of the population resides south of State Route201, which is 2400 South (Street). The residents closest to Kennecott's production facilities livealong 9200 West Street, which is adjacent to the company boundary fence. Several elementaryand other schools are in the community. The nearest, a former elementary school that wasrecently closed due to requirements for complying with the Americans with Disabilities Act andseismic upgrades, is on the west edge of town adjoining the Kennecott property boundary. Thenext closest school is several blocks east of Kennecott's property. ATSDR observed that thenearest residents to Kennecott's large tailings pond north of Route 201 (Figure 2) are a singlefamily (about 1,500 feet east of the pond rim) on 8000 West. The next nearest residents are asimilar distance from the pond in a subdivision south of Route 201 and immediately west of8000 West. A community golf course and recreational park (Figure 2) lie on the south side of Route 201, within several hundred feet of the pond. No nursing homes or hospitals are reported in the community.
A water company official reports that the Magna community obtains its public water supply fromtwo well fields located about 1 to 3 miles east of the tailings pond. A few residences, less than10, are not connected to the system and, instead, rely on private wells.
The Utah and Salt Lake Canal crosses the southern part of the community and carries waterdrawn from the Jordan River for irrigation and other nonculinary uses. Kennecott staff reportthat rainfall runoff in the process areas is collected and recycled to the greatest practical extent. Runoff from the tailings pond slopes collects either in the C-7 Ditch (and discharges to Great Salt Lake) or in the pond return canal (and is recycled via production facilities).
Tooele Valley extends south and west of Great Salt Lake between the Stansbury Mountains (onwest) and Oquirrh Mountains (on east) (Figure 3). The mountains rise a few thousand feet above the valley floor.
Several communities in Tooele Valley comprise almost 80 percent of the entire countypopulation. The principal population centers are Tooele (population 13,887) and Grantsville(population 4,500), which are located about 13 and 15 miles, respectively, from the facility'ssmelter. Communities nearest that smelter include Erda (population 1,113), Stansbury Park(population 1,049), and Lake Point (estimated population 400). Those communities are about 9,6, and 2½ miles from the facility's smelter. The city of Tooele is about 2 miles southwest of theformer International smelter. More than 93 percent of the population is of the white race (10). ATSDR learned from the county planning department that there is one nursing home in thecounty, in Tooele. A county school representative said there are elementary schools in StansburyPark, Grantsville, and Tooele, a middle school in Grantsville, and a junior high and high schoolin Tooele. Kennecott staff report that some mining and milling have been conducted on the westslopes of the Oquirrh Mountains, principally east and southeast of Tooele. The small communityof Lincoln (population about 100 (10)) is a short distance northwest of that former Internationalsmelter location (Figure 3). The Tooele Army Depot (Figure 3), immediately west of the town,advised ATSDR that they employ about 1,400 persons.
ATSDR learned from the Tooele County engineering department that everyone in the valleyrelies on groundwater as a drinking water source. Tooele has a public water system, but outlyingareas use private wells. Grantsville also has a public water system. Two subdivisions in Erda areconnected to a public system; the remainder of the residents are on private wells. Everyoneresiding within the Stansbury Park Water Improvement District is required to be connected tothat municipal water system. In Lake Point, everyone relies on private wells for their watersupply. Stansbury Park provides water to Great Lake State Park and other facilities along thelake shore.
Great Salt Lake Park Vicinity
Great Salt Lake Park, which lies to the north of the Kennecott facilities and Interstate 80,occupies about 3½ miles of shoreline, according to park officials. The park extends from aboutSaltaire Beach on the east to about Sunset Beach on the west (Figure 3). The county boat harborhas a capacity of about 300 craft. ATSDR was told by park officials that there were 676,000visitors in 1994, of which only about 10 percent enter the water. Potable water at the park issupplied by the Stansbury Water Improvement District located to the southwest in TooeleCounty.
Selection of Contaminants for Public Health Significance Evaluation
ATSDR reviews contaminant data and selects those that warrant subsequent further evaluationfor public health significance.
Contaminant selection considers the following factors:
- Concentrations of contaminants in media.
- Sample locations, field data quality, and laboratory data quality.
- Relationship of concentrations to ATSDR's public health assessment comparison values; also,the unavailability of suitable comparison values.
- Community health concerns.
Identification and selection of these contaminants does not imply that human exposure doesoccur or that exposure would actually result in adverse health effects. The contaminants selectedfor further evaluation and the media in which sampling shows they have occurred aresummarized in the data tables in Appendix E. The data tables also identify specific public healthassessment comparison values ATSDR considered in the selection process. An EnvironmentalMedia Evaluation Guide (EMEG) is an estimated comparison concentration that is based oninformation determined by ATSDR from its toxicological profiles for a specific chemical. Reference Dose Media Evaluation Guide (RMEG) comparison concentrations are based onEPA's estimates of the daily exposure to a contaminant that is unlikely to cause adverse healtheffects. An Action Level (AL) is an EPA regulatory concentration that, if exceeded in a publicwater system, requires the system operators to initiate specified response actions. A Cancer RiskEvaluation Guide (CREG) is a comparison concentration that is based on an excess cancer rate ofone in a million persons and is calculated using EPA's cancer slope factors. The OccupationalSafety and Health Administration (OSHA) and National Institute for Occupational Safety andHealth (NIOSH) standards for air in the workplace have been divided by 400 to develop aconservative comparison value for community exposure. Ambient Air Quality Standard(NAAQS) was also selected as a comparison value. An estimated (Est.) comparison value isbased on ATSDR staff review of toxicologic data for a contaminant.
ATSDR also reviewed the EPA Toxic Chemical Release Inventory (TRI) for 1992 to learnwhether that database would disclose any supplemental information about contaminant releasesin the area. The database confirmed Kennecott's reported releases of metals and sulfuric acid toair. Examination of the database also showed that an industry about two miles south of Magnareported substantial releases of organic chemicals to air (29). Staff at the UDEQ Air MonitoringCenter say they are not aware of any ambient air organic chemical sampling data for the sitevicinity.
Identification of Exposure Pathways
ATSDR identifies human exposure pathways by examining environmental and humancomponents that might lead to contact with contaminants of concern. A pathway analysisconsiders five elements: a source of contamination, transport through an environmental medium,a point of exposure, a route of human exposure, and an exposed population. Completedexposure pathways are those for which the five elements are evident, indicating that exposure toa contaminant has occurred in the past, is currently occurring, or will occur in the future. ATSDR regards people who come in contact with contamination as exposed; for example, peoplewho reside in an area with contaminants in air, or who drink water known to be contaminated, orwho work or play in contaminated soil are considered exposed. Potential exposure pathways arethose for which exposure seems possible, but one or more of the elements is not clearly defined. Potential pathways indicate that exposure to a contaminant could have occurred in the past, couldbe occurring now, or could occur in the future.
Only exposure situations associated with completed pathways are discussed in this assessment;evaluations did not disclose any potential pathways likely to be of public health significance. Key exposure pathway information is summarized in tables beginning on page 49 of Appendix E.
Determination of Public Health Implications
Determining the public health implications of a site is a two-track process: a toxicologicalevaluation, and, where appropriate, health outcome data evaluation.
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 an appropriate health guideline. Ifthe contaminant being evaluated is a carcinogen, the risk from exposure to that carcinogen isdetermined. The methodology for calculating exposure doses and cancer risk is described inAppendix F.
Health Outcome Data Evaluation
Health outcome data can provide information on the occurrence of cancer, birth defects, or otherdiseases or conditions; or the results of testing for the contaminants of concern in humans. Health outcome data are evaluated if it is biologically plausible for a health outcome to occur orif the community is concerned about specific health outcomes; and if the appropriate data can beidentified to evaluate a health outcome. For biological plausibility, the decision to evaluatehealth outcome data depends on whether a completed exposure pathway exists for a chemicalsuspected of causing the health outcome of concern (30). The selection of a noncarcinogenichealth outcome is based on a review of the toxicologic literature for that contaminant of concern.
Analysis of Groundwater/Drinking Water Pathway
Public drinking water supplies in the Kennecott--North Zone area do not appear to be affected bypast or present Kennecott operations. The water quality reports for the public water supply wellsdo not indicate any contaminant concentrations that would lead to adverse health effects. Thewater quality of public drinking water supplies is closely monitored by both the water utilitiesand the Utah Department of Environmental Quality. If conditions change, the department will beable to note such changes and take appropriate actions.
As in the case of public water supply wells, most private drinking water wells draw water fromzones deeper than 100 feet. These wells are not likely to be affected by Kennecott operations. Water below 100 feet is at a higher pressure than water near the surface. This higher pressureprevents either natural or man-induced contaminants from leaking downward into the drinkingwater aquifer. High concentrations of natural salts in the shallow aquifer usually eliminates the shallow zone as source of drinking water.
Note: See Appendix C for discussion of Comparison Values
| USEPA Action Level|
material also detected in laboratory blank
Cancer Risk Evaluation Guide
Environmental Media Evaluation Guide
estimated (by ATSDR)
value estimated (by laboratory)
milligrams per kilogram
milligrams per liter (water)
National Ambient Air Quality Standards
National Institute for Occupational Safety and Health
Occupational Safety and Health Administration
airborne particles 10 microns and smaller in diameter (relevant to inhalation exposure)
parts per million
Reference Dose Media Evaluation Guide
total dissolved solids
x-ray fluorescence analyses
micrograms per cubic meter (ambient air)
micrograms per liter (water)
less than the stated value
|Contaminant||Data Years|| Number|
|Note: From 1985 through 1989, for 1061 24-hour observations, themaximum PM10 reported was 487 g/m3. Ten of the observed valuesexceeded 150 g/m3 Ref. (5)|
|* Data from 1990 to 1993 were approximate. Sampler flow rate was assumed, rather than measured, during that interval.|
|Contaminant|| Magna--On site|
|West ValleyCity--Off site|
|* Many PM10 samples analyzed, 1991, 1992, 1993, 1994 Ref.(4)|
** Twenty-eight samples reported on-site and off-site, 1988 Ref. (14)
|Comparison Values (g/m3)|
|Sulfur Dioxide **||essentially |
|* Samples taken in 1993. Ref. (2) |
** Samples taken 1990 to mid 1994 for one sampler and from late 1992 to mid 1994 for another sampler. Results prior to 1994 are considered approximate. Ref. (4)
|Five PM10 samples analyzed, 1991, 1992Ref.(6)|
172 PM10 samples analyzed; zinc results areconsidered approximate, 1994 Ref (4)
|PM10||NR||70 (µg/m3)||Est. 11(µg/m3)||150|
|NR, butmuch lessthan 0.03(ppm)||0.14(ppm)||0.03|
|PM10 samples taken June 1992 through May 1993. Ref.(7)|
Sulfur dioxide samples taken 1981 through 1984. Ref (9)
|Samples taken in 1993. Sulfur dioxide not reported. Ref.(2)|
|Nine PM10 samples analyzed, 1993, 1994 Ref.(8)|
|Concentration: Maximum &Ranges (mg/kg)||Number of|
|Arsenic||Maximum = 40|
21 to 39
20 and less
|Cadmium||Maximum = 6.5|
6.4 and less
|Copper||Maximum = 600|
401 to 599
201 to 400
200 and less
|Lead||Maximum = 560|
401 to 559
201 to 400
200 and less
|Zinc||Maximum = 510|
401 to 509
201 to 400
200 and less
|* 255 samples analyzed via XRF methods, 1994. Ref.(13)        ** 2 samples, 1990. Ref.(14)|
|Contaminant|| Magna Soils|
West Valley City
|* Eleven samples, 1990. Ref. (14)         ** Two samples, 1990. Ref. (14)|
|Comparison Value *|
1993, 1994 (19)
|* Values are ultra conservative; would be pertinent in theimprobable event these waters would ever become asource of drinking water.|
Ref.(19) - eight samples in southern part of Great SaltLake, 1993, 1994
Ref.(18) - 44 samples in southern part of Great Salt Lake;1976
|Ambient Air |
|Source:||Kennecott facilities, other emissionsources||Kennecott facilities, naturallyoccurring metals|
|Exposure Point:||Magna vicinity, plus parts of Salt Lakeand Tooele Counties||Magna vicinity|
|Exposure Route:||Inhalation||Incidental ingestion|
|ReceptorPopulation:||Residents (also transient workers andvisitors)||Residents (perhaps transientworkers and visitors)|
|ExposurePeriod:||Past, present, future||Past, present, future|
|Estimated*NumberExposed toContaminants atanyConcentration:||On site**: in Magna, about 18,000|
Off site***:About 700,000, whichincludes 20,000 in Tooele County and670,000 (in 1994) visitors to Great SaltLake Park. There is another estimated300,000 to 500,000 in parts of theGreater Salt Lake City area whereoccasionally adverse air quality andexposures occur from a wide range ofurban and industrial sources of whichsite-related releases have beenconsidered a contributor under certainatmospheric conditions
|On site**: in Magna, about18,000|
Off site***: about 5,000 nearMagna
|ContaminantsSelected forDetailedEvaluation:||Particulates, sulfur dioxide, arsenic,cadmium, copper, lead, zinc||Aluminum, arsenic, barium,beryllium, cadmium, copper,lead, manganese, vanadium,zinc|
|* Estimate is believed to be within an order of magnitude of actual number|
** Within operable unit "boundaries"
*** Beyond operable unit "boundaries"
|Source:||Currently Kennecott, plus other sources;in the past, also the former InternationalSmelter|
|Exposure Point:||Tooele Valley and elsewhere|
|ReceptorPopulation:||Residents, transient workers and visitors|
|Exposure Period:||Past, present, future|
|Estimated* NumberExposed toContaminants atany Concentration:||On site**: in Tooele County, about20,000|
Off site***: About 700,000, whichincludes 18,000 in Magna and 670,000annual visitors (in 1994) to Great SaltLake Park. There is another estimated300,000 to 500,000 in parts of the GreaterSalt Lake City area where occasionallyadverse air quality and exposures occurfrom a wide range of urban and industrialsources of which site-related releases havebeen considered a contributor undercertain atmospheric conditions
|ContaminantsSelected for DetailedEvaluation:||Particulates, arsenic, cadmium, copper,lead, zinc|
|*Estimate is believed to be within an order of magnitude of actual number|
** Within operable unit "boundaries"
*** Beyond operable unit "boundaries"
|Surface Water--Great Salt Lake|
|Source:||Kennecott, plus other sources||Principally geologic andevaporative processes. Somedischarge from Kennecott viagroundwater and C-7 ditch.|
|Exposure Point:||Great Salt Lake Park vicinity||Great Salt Lake Park Vicinity|
|Exposure Route:||Inhalation||Incidental ingestion|
|ReceptorPopulation:||Principally visitors, some workers||Principally visitors, someworkers|
|Exposure Period:||Past, present, future||Past, present, future|
|Estimated*Number Exposedto Contaminantsat anyConcentrations:||On site**: not applicable; park is offsite|
Off site***:About 700,000, whichincludes 670,000 annual visitors (in1994) at park, 20,000 in TooeleCounty, and 18,000 in Magna. Thereis another estimated 300,000 to500,000 in parts of the Greater SaltLake City area where occasionallyadverse air quality and exposuresoccur from a wide range of urban andindustrial sources of whichsite-related releases have beenconsidered a contributor under certainatmospheric conditions.
|On site**: not applicable; park isoff site|
Off site***: annually about70,000 (based on 10 percent of1994 visitors) at park
|ContaminantsSelected forDetailedEvaluation:||Particulates, sulfur dioxide, arsenic,cadmium, copper, lead, zinc||Arsenic, cadmium, copper, lead,zinc|
|*Estimate is believed to be within an order of magnitude of actual number|
** Within operable unit "boundaries"
*** Beyond operable unit "boundaries"
Comparison of Exposure Dose to Health Guidelines
The air concentrations for a contaminant are compared directly to inhalation minimal risk levelswithout any additional calculation. The results of those comparisons are recorded in Table Awhich is on the following page.
The exposure doses for soil ingestion were calculated in the following manner. The maximumconcentration for a contaminant was multiplied by the soil ingestion rate for adults, 0.0001Kg/day; children, 0.0002 Kg/day, or pica children, 0.005 Kg/day. (The habit of ingesting largeamounts of soil is called pica.) This product was divided by the average weight for an adult, 70Kg (154 pounds) or for a child, 10 Kg (22 pounds). Those calculations assume that there isfrequent daily exposure to soil contaminated at the maximum level. The results of the actualcalculations are recorded in Table B which follows.
Surface Water Ingestion
The exposure doses for surface water ingestion were calculated in the following manner. Themaximum concentration for a contaminant was multiplied by a water ingestion rate for adults andchildren, 0.02 liter/day. This product was divided by the average weight for an adult, 70 Kg (154pounds) or for a child, 10 Kg (22 pounds). These results were then multiplied by a factor of 0.03,which represents the maximum number of visits a year, 10, that we assume might occur, dividedby days in a year, 365. Those calculations assume that anyone entering the water, actuallyingests 20 milliliters (which is about cup) of water. The results of the actual calculations are recorded in Table C which follows.
Calculation of Risk of Carcinogenic Effects
Carcinogenic risks from the inhalation of contaminated air were calculated through the followingprocess. The mean air concentration for arsenic or cadmium was divided by the inhalationcancer risk evaluation guideline (CREG) to identify the risk per 1 million persons. The CREG isthe air level at which the additional cancer risk is 1 in 1,000,000 for lifetime exposure. Depending on its size, the result was then adjusted to put it in the form of 1 per 10,000, 100,000,or other appropriate number. For example, the mean arsenic level for the Magna Vicinity (0.021µg/m3) divided by the CREG for arsenic (0.0002 µg/m3) equals a 105 in 1,000,000 or 1 in10,000. The results for the Magna Vicinity situation represent the maximum risk for cancer after 70 years of daily exposure.
In the Great Salt Lake Park air situation, the most exposed individuals appear to be the park staff. We assumed that some staff may have exposure for 8 hours a day, 5 days a week, 50 weeks ayear, for 30 years. Those assumptions were used to adjust the calculations described above by a factor of about 0.3.
Carcinogenic risks from the ingestion of soil were calculated through the following procedure. The adult exposure doses for ingestion of soil (calculated as described previously) weremultiplied by the EPA's Cancer Slope Factor for the contaminants of concern. The resultsrepresent the maximum risk for cancer after 70 years of exposure to the maximum concentrationof the contaminant. A cancer slope factor was available only for arsenic. The results of thecalculation of carcinogenic risk from exposure to arsenic can be found on Table B which follows. The results are discussed in the Public Health Implications (on Page 12) part of the Public Health Evaluation of Contaminants in Soil section.
Carcinogenic risks from the ingestion of surface water were calculated through the followingprocedure. The adult exposure doses for ingestion of surface water (calculated as describedpreviously) were multiplied by the EPA's Cancer Slope Factor for the contaminants of concern. The results represents the maximum risk for cancer after 70 years of exposure to the maximumconcentration of the contaminant. A cancer slope factor was available only for arsenic. Theresults of the calculation of carcinogenic risk from exposure to arsenic can be found on Table Cwhich follows. The results are discussed in the Public Health Implications (on Page 17) portionof the Public Health Evaluation of Contaminants in Surface Water section.
Uncertainties in Calculating Cancer Risk
The actual risk of cancer is probably lower than the calculated number. The method used tocalculate EPA's Cancer Slope Factor assumes that high dose animal data can be used to estimatethe risk for low dose exposures in humans (31). The method also assumes that there is no safelevel for exposure (32). There is little experimental evidence to confirm or refute those twoassumptions. Lastly, the method computes the 95 percent upper bound for the risk, rather theaverage risk, which results in there being a very good chance that the risk is actually lower,perhaps by several orders of magnitude (33).
The public health assessment was available for public review and comment in the local libraryfor a period ending June 28. The public comment period was announced in local newspapers. Inaddition, the public health assessment was sent to several individuals and the KennecottCorporation. Specific comments and responses are summarized below. Page numbersmentioned in this appendix refer to pagination in the public comment version of the document.
- COMMENT: Page 1 and Page 10
The recommendation for additional sulfur dioxide air quality monitoring to evaluate the effectsof the Kennecott smelter in the Tooele Valley is unwarranted.
|Response:||ATSDR has reviewed recently acquired ambient sulfur dioxide air qualitydata gathered at the Kennecott Ranch, located in Tooele Valley betweenLakepoint and Tooele. The very low concentrations of sulfur dioxiderecorded at that location together with corresponding data gathered at Magnaand Great Salt Lake State Park lead ATSDR to conclude that additional sulfurdioxide monitoring is not required in Tooele Valley. The document has beenchanged to reflect this opinion.|
- COMMENT: Page 11, in "Public Health Evaluation of Contaminants in Soil", and inSubsection B. "Background--Overview"
It is not appropriate to refer to the contaminants in tailings deposited by air as being "additions"to those occurring naturally in soils. Also, contaminants deposited by air are near backgroundlevels and pose no apparent public health hazard.
|Response:||ATSDR has changed the text in Subsection B to indicate that wind-blowntailings deposition has caused some metals concentrations in affected surfacesoils to be somewhat greater than their corresponding concentrations inunaffected soils. Health effects issues are not intended to be presented inSubsection B. ATSDR summarizes soil-related health effects in Table 5 ("NoApparent Health Hazard") and describes in Subsection E ("Public HealthImplications") that exposures to metals in Magna soil are unlikely to result inhealth effects in area residents.|
- COMMENT: Pages 6, 7, and 16.
The ATSDR Cancer Risk Evaluation Guide (CREG) and Environmental Media EvaluationGuide (EMEG) comparison values should be explained more thoroughly in the text or inAppendix C. It is not intuitively obvious why contaminant levels above the comparison valuesdo not constitute a health threat (page 10, F, 1). A lay reader would be alarmed by thecontaminant levels as compared to the CREG and EMEG comparison values. Although CREGand EMEG are referenced in Appendix C, they are not explained sufficiently. Additionalinformation is required for the reader to make an informed comparison of the values.
|Response:||Thanks for bringing this to our attention. We alerted the reader to thisproblem in the first paragraph of the Environmental Contamination section.|
- COMMENT: Page 16 (Table 8)
Comparison values shown in Table 8 for drinking water are not relevant to the potential exposurepathway (dermal) of visitors to the Great Salt Lake. Visitors do not drink water from the lake.
|Response:||ATSDR has reported that park visitors obtain water for potable purposesfrom a public water system. In the section "Public Health Evaluation ofContaminants in Surface Water". ATSDR described visitor contact with lakewater via wading and swimming but focused on incidental ingestion exposureduring those activities (Table 7 and Subsection D. "Exposure PathwayAnalyses"). Thus, ingestion-based drinking water comparison values areconsidered to be the best available criteria for selecting contaminants forincidental ingestion exposure evaluations. As noted in Table 7 and thesupporting discussion, ingestion exposure is not expected to occur more thana few times a year to any one person, and there is no apparent health hazardassociated with that exposure. The text has been modified to clarify theingestion focus.|
The following language is suggested for addition to Appendix C: "The EMEG is based on aconservative Minimum Risk Level (MRL) that is lower than the EPA reference dose (RfD). Inaddition, the MRL is based on a dose per body weight in an adult that would result in cumulativeeffects on the kidney after lifetime exposure. The MRL is not applicable to the calculation of a safe exposure level for short-term exposure in a 10 kg child."
|Response:||This suggestion is not accurate. MRLs can be the same, above, or below aRfD. Also the discussion of EMEGs in Appendix C is a general one, notspecific to any MRL. Lastly, there are MRLs for short-term or acuteexposures to some chemicals.|
- COMMENT: Page 14. Portions of the information pertaining to the Magna, Utah Childhood Lead Exposure Study were incorrect.
|Response:||We appreciate being provided the updated information. The document hasbeen revised accordingly.|
- COMMENT: Page 18, Concern 2. The following is suggested: 'A study in Taiwan hasdocumented that ingesting arsenic in drinking water can cause skin cancer.
|Response:||We have revised this sentence.|
- COMMENT: General
Many of the tables show the range of contamination to be from "nondetect to the highestconcentration". Please indicate what the nondetect value is as it reflects the quality of thelaboratory data used in the health assessment.
|Response:||ATSDR uses maximum contaminant concentrations (and sometimes averageconcentrations) in its evaluations of public health issues. Detailedinformation about nondetect values would not enhance our presentation ofpublic health issues; thus it is not provided.|
- COMMENT: Surface water
Selenium is not evaluated in the surface water exposure scenario, yet it is present in surface water in the area. Please indicate why it is not assessed.
|Response:||Great Salt Lake water quality is evaluated only for the metals that ATSDRbelieves might have been released by Kennecott facilities at concentrationlevels that might have contributed perceptibly to lake water concentrations.|
- COMMENT: General
It would be helpful to the reader to know if there will be any follow up regarding the lack of datafor air exposure pathways in Tooele Valley.
|Response:||ATSDR has recommended that air samples being taken by the state inGrantsville be analyzed more frequently for metals at least for the next year ortwo. Those data, then, should be evaluated to decide whether there may be anassociated health threat. ATSDR does not yet know whether the state willundertake this activity. Sulfur dioxide sampling data show thatconcentrations have been well below levels of concern.|
- COMMENT: Page 12, Section C
Zinc is considered one of the principal metals analyzed in the surface soils and was identified tobe "somewhat elevated"; yet Table 6 does not mention zinc nor does the text indicate that zinc isno longer to be considered. Please modify the document accordingly.
|Response:||The second to the last paragraph on the Page 11 says, " Arsenic, cadmium,copper and lead were found to be key contaminants for soils. Zinc was alsodetected in soil; but concentrations are not great enough for this metal towarrant further evaluation". In a footnote to Table 5, key contaminants aredescribed as being contaminants which initial evaluations showed had somepotential to be a public health hazard. The document has not been changed.|
- COMMENT: Page 20, Community Health Concerns.
The authors identify "permissible levels" for exposure to sulfur dioxide by an inhalation route but do not indicate the source of where the information was obtained.
|Response:||The "permissible levels" are EPA's National Ambient Air Quality Standards(NAAQS) and has been so noted.|
Page 4 says that Operable Units 8, 13, 14, and 15 were not addressed because the communitydoes not have or has very limited incidental access to them. However, more detailed informationshould be provided on each of those units and a thorough discussion presented regardingpotential offsite exposure from those units. Some specific concerns include:
- o Details should be provided regarding groundwater monitoring data, groundwater cleanupactivities, and the status of remediation.
o C-7 ditch water treatment and contaminant information should be included.
o Data should be presented about the depth of monitoring wells north and east of the tailingspond, the corresponding depth of the potable groundwater supply and the possibility ofmovement of the contaminated plume off site should be discussed.
|Response:||ATSDR believes the document adequately addresses the off-site health relatedeffects of on-site impoundments and contaminated areas and does not believethat additional facility, release, migration, etc. details would enhance thehealth purpose of the document. |
o Page 4 says--"ATSDR also evaluated data for...surface water in the C-7ditch; these will not be described further because we concluded that humanexposures are not significant."
o Page 4 says--"Our evaluation of Magna area drinking water supplies alsoindicated that there are no significant human exposures." On Page 19, inresponse to concerns about private well water raised by a resident living nextto the tailings pond, the document says that the concentrations reported forwell water appear to be within a natural range of concentrations for theaquifer and unaffected by the tailings pond. On Page 40, Appendix D saysthat public drinking water supplies in the area do not appear to be affectedby Kennecott operations; and most private drinking water wells draw waterfrom zones deeper than those that might be affected by Kennecott operations.
- COMMENT: Page 44, Table 10B
The comparison value used for lead detected in Great Salt Lake Park off-site air was the OSHAstandard ÷ 400 (0.125 g/m3) instead of the EPA ambient air standard of 1.5 g/m3. Since themaximum ambient concentration reported in Table 10B is 0.786 g/m3, ATSDR's use of theOSHA standard ÷ 400 (0.125 g/m3) indicates a health hazard. ATSDR should explain why thiscomparison value was used.
|Response:||In Appendix C (Page 37) ATSDR explains that comparison values are used toselect contaminants that warrant further evaluation for public healthsignificance. Comparison values are not threshold levels above which publichealth will necessarily be affected. Comparison values are levels belowwhich public health is not likely to be affected. Page 37 says thatidentification and selection of contaminants based on comparison valueconsiderations does not imply that human exposure occurs or that exposureswould actually result in adverse health effects. |
For Table 10B, our author selected the OSHA standard ÷ 400 (=0.125 g/m3)which is less than--and more conservative than--the EPA ambient airstandard of 1.5 g/m3. Thus, ATSDR's intent for comparison values isadequately served by this conservative selection.
- COMMENT: Comparison Values and Public Health Hazard Conclusions
Exposure concentrations often are shown in tables and elsewhere to be greater than theassociated comparison values, but the exposure situations are reported to be of no apparent health hazard. Please clarify this apparent conflict.
|Response:||As discussed in the preceding comment, comparison values are levels belowwhich public health is not likely to be affected and are used to selectcontaminants that warrant further evaluation for public health significance. Health Guidelines are discussed in Appendix F and are also used to identifycontaminants that need further evaluation. The determination that a publichealth hazard exists is done by comparing the specific exposure situations todata in the toxicological literature.|
- COMMENT: Page 12, Affected Populations.
A detailed description should be provided in the report on those areas in Magna in which metalsin soils are elevated with corresponding contaminant levels. A map of Magna should be includedin the report showing areas of Magna affected by high levels of those metals.
|Response:||ATSDR does not believe that a map is needed in this situation. We identifiedlittle or no clustering of the above-background metal levels. The possiblehealth implications (there were none) of the above-background levels arediscussed in the Public Health Implications section.|
- COMMENT: Page 13, Arsenic Availability.
The report states that arsenic appears to be less available in soil compared to water. A reference should be provided to support that statement.
|Response:||The statement has been deleted.|
1.ATSDR Staff (John Crellin, Don Gibeaut, John Mann, and Glenn Tucker) visited the sitevicinity during the weeks of September 4 and October 23, 1994. Pertinent information obtainedduring those visits is described in appropriate sections of this document.