PUBLIC HEALTH ASSESSMENT
KENNECOTT (NORTH ZONE)
MAGNA, SALT LAKE COUNTY, UTAH
The Kennecott--North Zone site is west of Salt Lake City Utah, along and near the shore of Great Salt Lake. The Agency for Toxic Substances and Disease Registry (ATSDR) staff toured the several operable units the U.S. Environmental Protection Agency (EPA) tentatively has identified to comprise the site; staff also reviewed data available for the site area. Those activities disclosed that community members and area visitors might be exposed in the vicinity of the community of Magna (Operable Unit-9) and Tooele Valley (Operable Unit-19) and also by Great Salt Lake Park. Those exposure situations considered one or more of the following:
The following is a summary of conclusions and recommendations.
An earlier version of the document was made available for public review and comment. Public
comment information is provided in an appendix.
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 the vicinity of Magna, Utah. More specifically, ATSDR has reviewed available environmental and health outcome data and community health concerns to determine whether adverse health effects are 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 the Superfund law (Comprehensive Environmental Response, Compensation, and Liability Act of 1980 [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--North Zone 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 property near the south shore of Great Salt Lake. At its Magna operations, Kennecott processes ore taken from its pit about 15 miles south and produces copper and other metals. Ore tailings are retained in a pond near the process facilities. Smelting and associated operations at Magna began in 1905 and have been conducted under multiple owners. Kennecott purchased the facilities in 1959. The company has continued to reduce contaminant releases over the years by improving the facility smelter and process equipment, process methods, and waste handling procedures.
EPA provided ATSDR a list identifying six operable units (OU) that tentatively comprise the north 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, and OU-19--Fallout in Tooele Valley. Operable unit locations (approximate) are shown on Figures 2 and 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 more information becomes available or as Kennecott initiates remediation and improves processes and equipment. 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 considers contaminant concentrations, plausible human exposure pathways, health concerns expressed by community 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 of the geographic, physical, and demographic settings. Exposure evaluations considered multiple contaminant origins (and releases that occurred over a period of multiple facility owners), including:
Those evaluations and observations aided staff in identifying community members and visitors that might experience exposure. That information, together with environmental sampling data, was used in further evaluations to decide whether exposures are likely to have any associated public 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 vicinity
of Magna (OU-9), Tooele Valley (OU-19), and Great Salt Lake Park that warrant discussion in
this assessment. Those exposure situations and the resulting public health hazard classification
determined 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 Situation | Public Health Hazard Classification |
| Airborne Contaminants
|
No Apparent Health Hazard No Apparent Health Hazard Insufficient Data to Classify Hazard |
| Soil Contaminants |
No Apparent Health Hazard |
| Surface Water Contaminants |
No Apparent Health Hazard |
Operable Units 8, 13, 14, and 15 are not addressed further in this assessment because the community has no or very limited incidental access, and any exposures that might occur at those operable units to workers (e.g., employees, contractors) or plant visitors would be within the jurisdiction of state and federal occupational health agencies.
ATSDR also evaluated data for surface water in the Utah and Salt Lake Canal, sediment from the
C-7 ditch and Great Salt Lake, and surface water in the C-7 ditch; these will be not described
further because we concluded that human exposures are not significant. Our evaluation of
Magna 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 soils
exposures in the Magna vicinity led ATSDR to conclude that soils at Great Salt Lake Park are
not 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 public
health assessment (Kennecott--South Zone). Airborne-related contaminant exposures are
evaluated for the site vicinity (e.g., for the Magna and Tooele Valley operable units and for Great
Salt Lake Park). The assessment does not address greater Salt Lake City's occasionally adverse
air quality and exposures from urban and industrial sources of which site-related releases have
been considered a contributor under certain atmospheric conditions (1).
PUBLIC HEALTH EVALUATION OF AIRBORNE CONTAMINANTS
The possibility of public health impact by air-borne contaminants is evaluated in this portion of the assessment for three exposure situations (Magna vicinity, Great Salt Lake Park, and Tooele Valley). Table 2 summarizes the results of these evaluations.
The evaluation results lead ATSDR to conclude that the Magna and Great Salt Lake Park air
exposure situations pose no apparent public health hazard. There are insufficient data to
properly evaluate the Tooele Valley situation.
| TABLE 2 - EXPOSURE TO AIR CONTAMINANTS* | |||||
| Situations | Key** Contaminants |
Exposed Population*** |
Route of Exposure |
Frequency of Exposure |
Public Health Classification |
| Magna Vicinity | Arsenic Cadmium | About 18,000 | Inhalation | Daily | No Apparent Health Hazard |
| Great Salt Lake Park |
Arsenic Cadmium | About 676,000 | Inhalation | Infrequent | No Apparent Health Hazard |
| Tooele Valley | Arsenic Cadmium | About 20,000 | Inhalation | Daily | Insufficient Data |
| * For each of the exposure situations, the facility smelter appears to be a primary source of contaminants. ** Key Contaminants--contaminants which initial evaluations showed had some potential to be a public health hazard. *** Note: the numbers shown focus on the subject operable units and nearby populations and do not include those in the greater Salt Lake City area where occasionally adverse air quality and exposures occur from a wide range of urban and industrial sources of which site-related releases have been considered a contributor under certain atmospheric conditions. | |||||
Over the years, smelting and its associated operations near Magna (Figure 2, Appendix A) have released metals, acids, and gases that have had a range of effects on ambient air quality nearby and in the region. The rates of contaminant releases have diminished substantially as Kennecott modified process systems, control equipment, and operating procedures. Former operations at International Smelting east of the city of Tooele, in Tooele Valley, once also contributed contaminants to air (Figure 3, Appendix A). Additional less substantive sources of airborne metal 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 selecting the several contaminants is provided on page 37 in Appendix C. Those several were further evaluated, yielding two that were identified as key contaminants, as summarized below. Readers are advised to read the public health implications section before making any conclusions about the 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 within
regulatory limits (Table 9A, Appendix E) (2,3,4). For the period of 1985 through 1989, 10 of the
1061 observations for particulate levels exceeded the 24-hour regulatory value (5). Laboratory
analyses between 1990 and 1994 showed relatively low metals concentrations in Magna and in
the adjacent West Valley City to the east (Table 9B, Appendix E) (4). Measurements at West
Valley City may nearly represent background air values, i.e., the area may not be affected by
wind-blown tailings and only modestly affected by releases from the facility's smelter stack.
| TABLE 3- KEY CONTAMINANTS FOR MAGNA AIR EXPOSURE SITUATION1 | ||||
| Contaminant | Average Level for 19942 | Average Level for 1990 -19933 | Comparison
Value (see Appendix C) |
Source |
| Arsenic | 0.017 µg/m3 | 0.022 µg/m3 | 0.0002 µg/m3 | CREG4 |
| Cadmium | 0.001 µg/m3 | 0.005 µg/m3 | 0.0006 µg/m3 | CREG4 |
| 1 There is a more detailed list of contaminants in Tables 9A and 9B starting on
page 43 in Appendix E. The process for selecting contaminants is described in
Appendix C starting on page 37. 2 Average for 256 samples from two Magna locations in 1994; in micrograms of contaminant per cubic meter of air 3 Average for 2147 samples from two Magna locations in 1990-93; in micrograms of 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 key
contaminants, arsenic and cadmium. Air sampling in 1988 and in the 1990s at the county boat
dock 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 | |||
| Contaminant | Average Level for 19942 | Comparison
Value (see Appendix C) |
Source |
| Arsenic | 0.046 µg/m3 | 0.0002 µg/m3 | CREG3 |
| Cadmium | 0.001 µg/m3 | 0.0006 µg/m3 | CREG3 |
| 1 There is a more detailed list of contaminants in Tables 10A and 10B starting on
page 44 in Appendix E. The process for selecting contaminants is described in
Appendix C starting on page 37. 2 Average for 164 samples taken at Great Salt Lake Park in 1994;. in micrograms of 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 years in Grantsville were available to characterize ambient air metals data in the valley. These are far too few to permit an evaluation of possible health impact. Analyses for PM10 at Erda and Grantsville 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 taken at 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 is located 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).
Magna Vicinity
The approximately 18,000 residents of Magna, according to the 1990 census (10), are being exposed 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 former school), arsenic levels varied from nondetect to 0.3 µg/m3 with an average of 0.021 µg/m3, and cadmium from nondetect to 0.1 µg/m3 with an average of 0.0046 µg/m3. Residents of the Magna area have been exposed to arsenic, cadmium, and other contaminants since the facility's smelter began operation in the very early 1900s. Concentrations in the air have been decreasing through time. 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 about 3½ miles of shoreline (Figure 3). The individuals with the greatest exposure would be the park staff who would be exposed 8 hours a day 5 days a week. Another group being exposed would be the users of the 300 craft docked in a county boat harbor by the park. Maximum exposure frequency for these individuals would probably be 8-9 times a month for 8-9 months a year. Park visitors (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 varied from nondetect to 0.178 µg/m3 with an average of 0.046 µg/m3, and cadmium from nondetect to 0.007 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 to unknown concentrations of arsenic, cadmium, and other contaminants. Another 10,000 to 15,000 farther south in the valley also likely are exposed periodically. Tooele Valley extends west and south from Great Salt Lake and lies between the Stansbury Mountains (on west) and Oquirrh Mountains (on east) (Figure 3). The mountains rise a few thousand feet above the valley floor. Communities in the northern part of the valley are nearest the facility's smelter. These include Erda (population 1,113), Stansbury Park (population 1,049), and Lake Point (a resident estimated the population to be 400). Those communities are about 9, 6, and 2½ miles from the facility'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 in the 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 at Grantsville) that were analyzed for metals. This number of samples is insufficient to permit further evaluation of metals in this exposure situation. There are extensive data on sulfur dioxide levels. The levels identified are all below the permissible limits established by EPA, and thus will not be evaluated further.
Public health implications decisions made in the public health assessment process primarily are based on toxicological evaluations that compare exposure dose (i.e., the amount of a substance individuals in an exposure pathway are exposed to daily) to appropriate health guidelines for carcinogenic and noncarcinogenic effects. There are health guidelines for carcinogenic effects for arsenic and cadmium; for noncarcinogenic effects there is a health guideline for cadmium but not for arsenic. The methodology for calculating exposure doses and cancer risk and the results of 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 Vicinity air will result in health effects in area residents. Levels of arsenic and cadmium identified in sampling in Magna since 1990 are considered too low to result in noncarcinogenic effects or a significant increase in risk for cancer.
We evaluated continuous daily 70-year exposures to the mean and maximum levels of arsenic and cadmium in Magna Vicinity air, both separately and combined. We also evaluated the exposure Magna residents would receive if they lived in Magna and worked at the Great Salt Lake Park. Both the mean and maximum cadmium levels for any of these exposure scenarios are at least 30 times lower than the health guideline for cadmium. This indicates that there is little or no chance that these levels could cause any noncarcinogenic health effects. There is no health guideline for air exposures to arsenic, so we compared air levels to the lowest observed adverse health effects noted in long-term exposures of workers (11). The mean arsenic level is about 2,400 times lower and the maximum arsenic level about 170 times lower than the lowest observed 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 not significantly 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 Lake Park air will result in health effects in Park staff and visitors. Levels of arsenic and cadmium identified in sampling in the Great Salt Lake Park in 1994 are considered too low to result in noncarcinogenic 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 and cadmium in Great Salt Lake Park air both separately and combined. This staff exposure would be much greater than for park visitors, and thus any conclusions about the Park staff would also apply to Park visitors. Both the mean and maximum cadmium levels for any of these exposure scenarios are at least 30 times lower than the health guideline for cadmium. This indicates that there is little or no chance that these levels could cause any noncarcinogenic health effects. As with the Magna Vicinity exposure situation, we compared air levels to the lowest observed adverse health effects noted in long-term exposures of workers (11). The mean arsenic level is about 1,100 times lower and the maximum arsenic level about 280 times lower than the lowest observed 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 not significantly 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
Recommendation--ATSDR recommends that ambient air sampling be conducted near the plant
to confirm whether releases pose a public health hazard to residents.
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