PUBLIC HEALTH ASSESSMENT
MURRAY, SALT LAKE COUNTY, UTAH
ATSDR has evaluated all of the available environmental monitoring data to determine whatenvironmental contaminants and which specific areas on or around the site may be a concern. Weused comparison values to determine which contaminants and which areas to examine moreclosely. Comparison values are health-based thresholds below which no known or anticipatedadverse effect on the health of persons should occur. The values allow an adequate margin ofsafety. The contaminant tables in this section identify the comparison values for eachcontaminant. Appendix 2 contains a description of the comparison values used in this publichealth assessment.
We evaluate a contaminant further if the contaminant level in a valid environmental sampleexceeds comparison values. The presence of a chemical in the contaminant tables does not meanthat either exposure to the contaminant or adverse health effects has occurred or will occur. Inclusion in the tables indicates only a potential for human exposure to the selected chemical. Later sections of this public health assessment contain more detailed discussions of the potentialfor adverse human health effects as a result of any exposures to the selected contaminants.
This document focuses on those contaminants which were in areas where there is reasonablepotential for human exposure. However, the environmental data for the all on- and off-site areaswere evaluated.
Figure 1 depicts the site boundaries. Grandview and Doc and Dell's mobile home parks, and property of the Church of Jesus Christ of Latter-day Saints are on the Murray Smelter site. As indicated on Figures 3 and 4, samples were taken throughout the site area and analyzed for lead and arsenic. Soil, interior dust, and drinking water were sampled at the Grandview Mobile Home Park and analyzed for lead (4). This on-site contamination subsection includes discussion of the sampling results. Slag and airborne deposition of lead from historical smelting operations contribute to soil lead levels. This subsection presents air dispersion modeling results (5).
Soil and Slag
Two factors--airborne emissions and placement of waste slag near the smelter--resulted in thespread of contaminants from the smelter. Most of the site slag has been leveled or mined out andforms the base of yards for the on-site facilities and industries. The slag was used for road base,railroad base, and fill throughout north and central Utah (2). It was also used in concrete. Analysis of the slag material indicates that it contains high levels of arsenic, cadmium, lead, zinc, and other heavy metals (see Table A on page 40).
Soil investigations (including some slag) of the Murray Smelter site including Grandview and Docand Dell's mobile homes parks were conducted in July 1992, April 1993, and September/October1995 (6,7). The investigations showed greater than 5000 ppm lead in on-site areas associatedwith slag (Figure 3). The 1995 data indicate that mean concentrations on site ranged from 2.5 to7,700 ppm arsenic and 71 to 33,000 ppm lead (7). The maximum mean concentrations for arsenicand lead were from sampling area EU3, which is located between the railroad tracks on thewestern edge of the on site area (Figures 1, 3, & 4).
Specific information on the mobile home parks is given below.
Grandview Mobile Home Park
This mobile home park is near the southwest corner of the Murray Smelter site (Figure 1). Wasteslag material is present at the ground surface at the west end of Grandview and at several otherlocations throughout the park (2). Grandview contains approximately 45 homes, and about 13children live there (2, 6). As observed on the two site visits, a fence separates this residential areafrom the commercial on-site activities.
The Valley Smelter Study in July 1992 included systematic sampling of surface soil for lead athistoric lead smelter sites in the southern end of the Salt Lake Valley (9). Samples of 6 locationsat Grandview showed a mean concentration of 710 parts of lead per million parts of soil (ppm).Material placed around the swing set area at Grandview was sampled in November 1992 (10). Two samples were taken from the upper 6 inches of this material, which contained slag and ablack, sooty substance. These samples contained elevated levels of arsenic (66 - 900 ppm),cadmium (less than 10 to 140 ppm), and lead (34 to 8,499 ppm). Because the material in theswing set area was not soil, the sampling results are not included in tables 1, B, and C. However,the Toxicological Evaluation section of this public health assessment contains a discussion ofpossible health implications of the results. Soil in the swing set area was removed to a depth of18 inches and replaced with clean fill in September/October 1995.
Table 1 summarizes the results of additional sampling at Grandview in April 1993. Table Bdescribes the results further. Arsenic and cadmium concentrations in surface soil (upper fewinches) exceeded ATSDR comparison values for ingestion (Table 1). The mean arsenic andcadmium concentrations were 206 ppm for 13 arsenic samples and 15.6 ppm for 62 cadmiumsamples. The mean lead concentration from 116 surface soil samples was 862 ppm. The April1993 sampling focused on high use/high exposure areas such as play areas, walkways, bare areasin lawns, or the home perimeter (2,13).
|Metal||Range in ppm*||Mean (ppm*)||CV1 in ppm*||CV1 Source|
|Arsenic||41 - 470||206||0.4||CREG2|
|Cadmium||6.9 - 84||15.6||1||EMEG3|
|Lead||90 - 5300||862||none|
|* - ppm = parts per million|
1 - CV = Comparison Value
2 - CREG = Cancer Risk Evaluation Guide
3 - EMEG = Environmental Media Exposure Guide
Additional sampling results can be found in Table B on page 41.
The Grandview Mobile Home Park was part of ASARCO's soil investigation in September 1995. It was broken into three exposure units (EUs)- EU8, EU9, and EU10. The mean arsenic and leadconcentration in EU8 was 1674 ppm and 6177 ppm, respectively. Soils in EU8 (area with surfaceslag and potential smelter-derived materials) were removed to a depth of 6" and replaced withclean fill in September/October 1995 (8). Although the mean arsenic and lead concentrations in the other exposure units were substantially lower, the levels are still of public health significance (75 and 118 ppm arsenic and 909 and 569 ppm lead respectively).
Doc and Dell's Mobile Home Park
Doc and Dell's is adjacent to large slag piles (Figure 1), but there is a limited amount of surfacesoil because most of the park is paved with asphalt (13). The Valley Smelter Study includedsamples from six locations at Doc and Dell's, and the results indicated low lead concentrations (arange of 74 to 429 ppm and a mean of 253 ppm)(9).
The majority of this slag adjacent to Doc and Dell's is not easily accessible because it forms asteep wall about 20 feet high immediately west of this mobile home park. A cement well severalfeet high lies at the base of the slag pile and runs nearly the entire length of the exposed slag pile(observation made during the two site visits). Doc and Dell's has approximately 45 homes withvery few, if any, children living there. The slag adjacent to Doc and Dell's has high concentrationsof lead and other metals (Table A).
ASARCO analyzed two slag samples from Doc and Dell's in April 1993. They detected elevatedconcentrations of metals. The maximum arsenic and lead concentrations were 930 and 7,600 ppmrespectively (10).
The Doc and Dell Mobile Home Park was part of ASARCO's soil investigation in September1995. The mean arsenic and lead concentrations from 10 soil samples taken from the upper twoinches of soil were 18 ppm and 759 ppm, respectively.
The Church of Jesus Christ of Latter-day Saints Property
In June 1994, fifteen boreholes 2 to 12 feet deep were drilled on the property of the Church ofJesus Christ of Latter-day Saints (11). Soil was sampled over the 0 to 6 inch depth interval in seven of these boreholes. In the upper 6 inches of soil, arsenic concentrations ranged from 5.4 to 63 ppm (26 ppm mean) and lead concentrations ranged from 13 to 1700 (498 ppm mean). The maximum lead concentration, 2,000 ppm, was found in the 0 to 2 foot interval (11). These dataindicate low concentrations of metals in most samples, with a few elevated concentrations ofarsenic and lead.
Interior dust samples were collected from 28 homes at Grandview in April 1993 (13). Each dustsample represents vacuuming from a one-third meter square area of the floor in two to three hightraffic locations: adjacent to the main traffic path from the most frequently used entrance to thehouse, a main pathway in the most used room, or a child's bedroom. The lead concentrations indust collected using this method ranged from 24 to 526 ppm, with a mean of 210 ppm (12).
Tap water (city water, not site groundwater) from the cold water spigots in kitchens andbathrooms at Grandview was sampled for lead in April 1993. The samples were collected by theresidents, who took a first draw sample (the water sat motionless for a minimum of at least sixhours) (13). Two of 28 residences had detectable levels of lead. Tap water at these residences contained 9 and 17 parts of lead per billion parts of water (ppb) (14). EPA's action level for lead in drinking water is 15 ppb.
There are three aquifers beneath the Murray Smelter site: a shallow unconfined (permeable byrainwater) aquifer, an intermediate confined or semiconfined (bound above by the Bonneville BlueClay and below by impermeable clay beds) aquifer, and the deep principal aquifer. The deepprincipal aquifer is the main source of groundwater used in the Jordan Valley (4). It is the sourceof water for the municipal water supplies (15) and for many of the local private wells. The deepprincipal aquifer is separated from the surface by at least five confining layers (15), therefore it isunlikely to be affected by contamination in overlying aquifers. Monitoring wells at the MurraySmelter site were placed in slag fill material or in the shallow and intermediate aquifers. Groundwater contamination at the Murray Smelter site is found primarily in the shallowunconfined aquifer. Groundwater in the shallow unconfined aquifer flows north-northeast towardthe Little Cottonwood Creek (16). Groundwater in the intermediate aquifer flows northwest fromthe site toward the Jordan River.
EPA investigated groundwater in the vicinity of the Murray Smelter in 1984 through fivegroundwater wells (three shallow wells and two intermediate wells, each with one upgradientwell) (2). Lead was below the detection limit of 4.5 ppb in both shallow and intermediate wells. Cadmium was above the detection limit of 2.3 ppb only in the upgradient wells (indicating thatcadmium levels are background or not site related). Arsenic was below the detection limit of 9ppb in all but one well, which contained a concentration of 9.5 ppb.
In June 1991, Versar Architects and Engineers, Inc. sampled groundwater from three monitoringwells at the Monroc Asphalt Plant location in the north-central portion of the Murray Smelter site(32). The wells were adjacent to surface slag piles. Total lead ranged from 240 to 5,800 ppb,and dissolved lead ranged from below the detection limit of 10 ppb to 30 ppb. These 2-inchdiameter monitoring wells were purged, but the water was reported as having high turbidity. ATSDR received some December 1991 monitoring well results from Monroc well #1. These dataindicate that arsenic, cadmium, and lead were below detection limits (10).
Although the earlier groundwater data did not indicate contamination or were inconclusive, welldata collected in 1995 and 1996 indicated arsenic contamination primarily in the shallow unconfined aquifer (shallower than 30 feet below ground surface) (30, 31). Monitoring well dataindicated shallow aquifer contamination was highest (around 30 ppm of arsenic) at monitoringwell 106 near the southwest corner of the site. In February 1996, hydropunch sampling (samplingthrough temporary wells) was conducted to help delineate shallow groundwater contamination. Arsenic concentrations ranged from less than 0.005 ppm to 166 ppm from 27 sampling locations(31). The data indicate several on-site areas of shallow groundwater contamination by arsenic.The maximum contaminated area was just east of the on-site stacks. This data also confirmedshallow groundwater contamination beneath the railroad tracks in the southern portion of the site. Lead concentrations were below the detection limit throughout the site.
Some arsenic contamination of the intermediate aquifer (to an approximate depth of 70 feet) hasalso occurred at well locations GW-1A and GW-2A. This contamination is probably the result ofcross-contamination from the shallow to the intermediate aquifer due to failure of the seals in theintermediate wells (31). The majority of wells in the intermediate aquifer do not have elevatedconcentrations of arsenic. Hydrometrics, Inc. has recommended that the two contaminated wellsin the intermediate aquifer be abandoned.
Although the shallow groundwater on the Murray Smelter site is contaminated with arsenic, thereare currently no drinking water wells on or near the site which draw water from this aquifer. However, since some private wells in the intermediate aquifer may exist, ATSDR recommendsthat the source of arsenic in the shallow aquifer be determined and removed if feasible.
During the operation of the Murray Smelter, two tall stacks, 300 and 455 feet high, were sourcesof air-borne emissions at and surrounding the site (5). Emissions from both stacks were controlled by air pollution control equipment, a baghouse for the 300-foot stack and an electrostatic precipitator for the 455-foot stack (5). Stack discharge was modeled based on historical data on stack parameters and lead emission rates and information from an ASARCO smelter in East Helena, Montana. The modeling reflects representative meteorological and precipitation data from the Salt Lake County Airport stations (approximately 10 miles north). Figure 5 shows the pattern of deposition, which is similar to the wind pattern at the Salt Lake City Airport. The peak total deposition predicted for the Murray Smelter area occurred 300 meterssouth-southeast of the stacks on Murray High School property (5). The peak annual average deposition was predicted as 0.10458 grams per square meter (g/m2), based on a 700 ton/day production rate. The smelter operated for about 47 years.
Shady Grove mobile home park is about a mile north of the Murray site boundaries and has otherhistorical smelters in its vicinity; thus, it was considered to be off site. Environmental sampling atthis and other off-site locations is discussed below. Additionally, ASARCO sampled soil andhouse dust immediately west and south/southeast of the Murray Site boundaries for arsenic andlead (Figure 1).
The results of several sampling efforts are depicted on Figures 3 and 4. During the Valley Smelter Study several off-site areas were evaluated including the City Park and County Fairgrounds to the east, and the Murray High School and Hillcrest Junior High School south and southwest of the site. The study showed that these off-site areas generally had leadconcentrations below 1,000 ppm. There was one high reading of 2,014 ppm lead on the CountyFairgrounds. There were several elevated lead results (16,974 and 18,345 ppm) to thesouth/southwest of the site adjacent to Interstate 15. The highest off-site concentrations, thoseexceeding 5,000 ppm, are within 500 feet of the railroad tracks.
ASARCO conducted a soil investigation in September/October 1995. The off-facility areashaving the highest arsenic and lead concentrations were the zone just south of the GrandviewMobile Home Park (ISZ-7) and the zones along the western property boundary (ISZ-1 and ISZ-8). The mean concentrations in these zones ranged from 71 to 130 ppm arsenic and 990 to 1256 ppm lead (7). The 1995 data indicate that mean concentrations off site ranged from 18 to 130 ppm arsenic and 259 to 1256 ppm lead (as compared to 18 to 1674 ppm arsenic and 759 to 9346 ppm lead on site) (7). Specific information on the Shady Grove mobile home park and Murray High School is given below.
Shady Grove Mobile Home Park
The two July 1992 samples in the Shady Grove mobile home park indicated lead concentrations of252 and 713 ppm. Surface soil samples taken at Shady Grove in March 1993 showed a meanconcentration of 430 ppm lead for 12 samples (18). Two samples had arsenic concentrations of45 and 65 ppm.
Murray High School
The Valley Smelter Study indicates two samples on the Murray High School property with leadconcentrations in the 1,000 - 2,000 ppm range. Soil at Murray High School was also sampled inOctober 1984 and June 1992 (2). The average concentrations from seven samples were 629 ppmlead and 127 ppm arsenic. ASARCO conducted additional sampling at the school in January1995. Soil near the tennis courts was sampled to a depth of 18 inches in five locations. Concentrations for the upper 2 inches of soil (excluding the vegetation) ranged from 9.7 to 249ppm arsenic (mean of 155 ppm) and from 31 to 1,899 ppm lead (mean of 1,248 ppm). The 1995data indicated means of 54 ppm arsenic and 775 ppm lead (7).
House dust samples were collected from 24 residences in the off-facility area (7). The samesampling methodology was used off-facility as was used on-facility at Grandview in April 1993: acomposite dust sample was collected from three areas. There was one residence on Wilsonavenue that had elevated arsenic and lead loads and no indication of a lead paint problem. Ingeneral, lead in house dust was higher off-site (lead concentrations ranged from 74-5,315 ppmwith a mean of 510 ppm) than in interior dust samples taken from on-site residences at Grandview(lead concentration ranged from 24-526 ppm lead with a mean of 210 ppm). The 1993 arsenicdust results for Grandview were rejected by ASARCO, Inc because of the data quality concernsdiscussed in the QA/QC section on page 20. The 1995 arsenic concentrations in dust for the off-facility area ranged from below the detection limit of 10 ppm to 94 ppm (with a mean of 27 ppm).
Little Cottonwood Creek flows along the northern boundary of the site and merges with theJordan River approximately 4,500 feet west of the site. EPA collected two surface water samplesin October 1984, one in the Murray City Park, which is upstream from the site and one at theVine Street culvert, which is downstream (2). They found no major differences in the metal concentrations of surface water upstream versus downstream. Surface water of the Little Cottonwood Creek in the vicinity of Murray Smelter is not used as drinking water.
ASARCO collected five surface water samples in March 1984 (one upstream sample, one sampleadjacent to the site, and three downstream samples on the Little Cottonwood Creek) and analyzedthem for arsenic, cadmium, and lead. At each sample location, dissolved samples (filter samplesexcluding sediment on the filter) and total samples (unfiltered samples including any sediment)were collected for cadmium and arsenic analysis. Dissolved cadmium and lead concentrationsremained fairly constant and low regardless of sample location. Total lead was highest upstreamof the site. Total arsenic concentrations ranged from 40 to 170 ppb. These surface water dataindicate metal contamination in creek sediment.
Surface water samples were also collected by ASARCO in April and June 1995 (19) The results indicate some total recoverable and dissolved arsenic (40 to 65 ppb in April 1995) adjacent to the site and at a location about 2000 feet downstream. It appears that there is somelocalized leaching of arsenic into surface water. The soil near the creek contains some elevatedarsenic and lead concentrations near the site. The 1995 data indicate little, if any, impact to theJordan River.
Slag is present in the sediment of Little Cottonwood Creek near the site (2). The slag pile abutsthe creek near the former Germania Smelter location. Sediment results from 1993 indicate heavymetal contamination of sediment in the creek (3): the downstream concentrations of metals (214ppm arsenic, 88 ppm cadmium, 2,348 ppm lead, and 3,384 ppm zinc) are significantly higher thanthe upstream concentrations (5 ppm arsenic, less than 2 ppm cadmium, 76 ppm lead, and 208 ppmzinc). Sediment data collected by ASARCO in 1995 also indicate elevated metals in LittleCottonwood Creek adjacent to the site and in closed depressions on site (19).
Although groundwater is used for drinking water in the site vicinity, no drinking water wells areknown to be contaminated because of historical smelting operations at Murray Smelter (2). Within a half mile of the site boundaries, there are 5 public drinking water wells, serving about8,428 people, and about 30 private wells or available water rights for wells. The City of Murrayoperates four of these public drinking water wells, and Winget Enterprises operates the other one. The nearest domestic well is approximately three-tenths of a mile from the site.
Between a half mile and a mile from the site boundaries, there are 11 more public drinking watersupply wells that draw groundwater from the deep principal aquifer (2). Four of these wells areMurray City wells, four are Taylorsville-Bennion wells, two are Salt Lake County wells, and oneis a Winget Enterprises well. The population served by these wells is estimated at 22,171 people.
A well survey indicates that the private wells near the Murray Smelter site are in the intermediateand deep aquifers (most well depths are greater than 100 feet deep). Arsenic contamination atMurray has been found on site primarily in the shallow aquifer at approximately 26 feet. Monitoring wells off site, outside of the Murray Smelter property boundaries, have arsenicconcentrations below the federal drinking water standard of 50 ppb. Although shallowcontaminated groundwater could migrate off-site, no one is likely to be affected because the drinking water wells are not in the contaminated aquifer and are unlikely to be influenced bycontamination at the Murray Smelter site.
Air modeling results show that total (wet and dry) deposition of lead was highest on the MurrayHigh School property, which is south-southeast of the Murray Smelter site, and was also highimmediately west of the site (Figure 5). Air dispersion modeling was described in the on-site air subsection. EPA has included these areas in its off-facility boundaries and has sampled soil and dust.
Some fishing occurs in Little Cottonwood Creek near the site (2). People have been seen fishingat the Vine Street Bridge, which intersects the site midway on its northern boundary. The creekin this area receives some water draining off the site and groundwater that has flowed through theformer smelter area. Slag is present in a few locations in the creek, and sediment values indicatecontamination by metals. No fish tissue data were available for Little Cottonwood Creekdownstream of the site. Benthic macroinvertebrates were collected from Little CottonwoodCreek near the site and analyzed for metals in 1995. Elevated concentrations of some metals werefound in benthic macroinvertebrates.
ATSDR was able to obtain quality assurance and quality control (QA/QC) information for mostof the data presented in this public health assessment. This information indicates appropriateQA/QC was performed for most samples. Data quality reports for the 1995 data indicated thatthey were valid and useable. ATSDR did not use data of questionable value. Many of the 1992and 1993 arsenic samples were analyzed by XRF (X-Ray Diffraction) and were found to have apoor correlation with analyses done using standard laboratory analytical techniques (10, 13). Therefore, we did not use these results. The 1994 groundwater data from the study of the Churchof Jesus Christ of Latter-day Saints property were not used because of unconventional samplingtechniques (11). We tried to base conclusions on accurate, relevant, and reliable data.
Two physical hazards were noted during the ATSDR site visits. Slag material could erode andslide into the Doc and Dell's Mobile Home Park. A Doc and Dell's resident reported that a pieceof slag fell into his truck and damaged it. Another hazard is the one created by commercialtrucks sharing the entrance of the Grandview Mobile Home Park. The latter is a safety issue thatis related to current on-site cement operations and is unrelated to the Murray Smelter site itself.
To identify possible facilities that could contribute to the environmental contamination in Murray,ATSDR staff members searched the 1987-1993 files of the TRI databases for the area around thesite (20). EPA staff members developed TRI from chemical release information certain industriesprovided for air, water, and soil. None of the facilities in the Murray area report releases ofchemicals that are contaminants of concern at the Murray site. Although no known activeindustries are reporting releases of metals such as those found near the Murray Smelter site, thereare many historical smelters in the area which may have contributed to metals contamination inthe area.
This section presents evaluations of the possible environmental pathways that help determinewhether individuals have been, are being, or will be exposed to site-related contaminants. Environmental pathways can be completed or potential. A completed pathway indicates that human exposure to contaminants has occurred in the past, is occurring, or will occur in the future (22). A potential exposure pathway indicates that human exposure to contaminants could have occurred in the past, could be occurring, or could occur in the future. An exposure pathway can be eliminated from consideration if exposure has never occurred and never will occur. If there is uncertainty about the site relatedness of the contaminants of concern in an exposure pathway, the pathway will be evaluated as if the contaminants were site related.
We could not evaluate the air pathway because we did not identify any air data for the period when the smelter operated (1902-1949). Air modeling suggests that deposition was highest just to the south-southeast of the site (see Figure 5 on page 15). Soil may have retained some of the contaminants from air deposition. Off-site residential soils and house dust were sampled by ASARCO in 1995.
Table 2 lists the components of the soil pathway, the only completed environmental exposure pathway (i.e., human exposure has occurred or is occurring) and the estimated number ofindividuals in the pathway. Exposure may occur from direct ingestion of soil in yards, soil trackedindoors, house dust, and inhalation of fugitive dust. As depicted on Figure 6, about 274individuals in the site area live where lead levels are above 500 ppm.
|Pathway Name||Point of Exposure||Route of Exposure||Exposed Population||Contaminants of Concern||Estimated Exposed Population|
|Soil/Dust||Contaminated areas depicted on Figure 6||Ingestion |
|People living or working in contaminated areas depicted on Figure 6||Lead |
Table 3 lists the components of the four potential environmental exposure pathways and theestimated number of individuals in each pathway. These possible environmental exposurepathways are potential contamination of groundwater and migration into drinking water wells,sediment of the Little Cottonwood Creek, vegetables from any gardens in contaminated soil, andfish.
Groundwater is a potential exposure pathway because contamination in the shallow aquifer couldmigrate off-site and this aquifer could be used locally for drinking water in the future. However,neither of these conditions currently exists. Murray residents are served by municipal wells thatare monitored for water quality. The municipal wells and many of the private wells drawgroundwater from depths of several hundred feet. Based on this information, we do not believethat anyone is currently being exposed to groundwater contamination from the Murray Smeltersite and that it is unlikely that anyone will be exposed to this contamination in the future.
Sediments in Little Cottonwood Creek adjacent to and immediately downstream of the sitecontain arsenic, cadmium, and lead contamination 16 to 44 times greater than that found upstreamof the site. Although it's possible for a child or adult to get to the creek and ingest sediment, it'sunlikely that it occurs frequently enough to have health consequences. The creek is not veryaccessible, particularly from the Grandview Mobile Home Park, because of fences, steeptopography, slag piles, industry, and other impediments. It seems more likely that local residentswould use the creek at Murray Park, which is upstream of the site.
On our site visit, ATSDR staff did not notice any vegetable gardens at either Grandview or Docand Dell's mobile home parks. There was no communal garden area at either mobile home park. However, it's possible that some vegetable gardens do exist or may have existed in the past. Farming in the area during the operation of the smelter may have led to ingestion of metals on orin fruits or vegetables. However, we have no data on which to base an estimate of an exposedpopulation. Although we estimated that fewer than 10 people are or were exposed to metals viauptake in homegrown vegetables, the number may be higher. We recommend that peopleconsuming homegrown produce from gardens in contaminated areas (Figures 3 and 4) use 2 feet of clean fill for their gardens.
Although fishing near the site does occur, there has been no collection of fish tissue data for theLittle Cottonwood Creek in the site vicinity. The fish pathway was considered potential becauseof this data gap.
Surface water is eliminated as an exposure pathway because surface water near the site is not usedas drinking water, and skin absorption of dissolved metals from surface water is unlikely to besignificant. Some leaching of arsenic from the site is occurring and is present in the surface waterof Little Cottonwood Creek. However, we anticipate that metals would be distributed to thesediments and would not be carried far as a dissolved species in surface water.
As discussed in the Pathways Analyses section, the soil exposure pathway is consideredcompleted (i.e., human exposure occurred). The contaminants of concern in the pathway arearsenic, cadmium, and lead.
Typically, the toxicological evaluation in a public health assessment is a comparison of theexposure dose (i.e., the amount of a substance individuals in an exposure pathway are exposed todaily) with an appropriate health guideline. In this evaluation, the health guidelines are ATSDR'sMinimal Risk Levels (MRLs). Table 4 contains a summary of the comparison of the exposuredoses to the MRLs for each chemical. There is a discussion of the methodology for calculatingthe exposure doses, along with the results of the calculations (Table C), in Appendix 3 on pages 45 and 46.
Adult, child, and pica child exposure doses for arsenic in soil exceeded the health guideline forarsenic. The child and pica child exposure dose for cadmium exceeded the health guideline. There is no health guideline for lead. Human epidemiological studies have formed the basis forclassifying arsenic as a known carcinogen (24). Animal data provide the basis for identifyingcadmium and lead as probable human carcinogens (33,34). A cancer slope factor exists forarsenic, but there is no cancer slope factor for cadmium or lead; therefore, the risk of carcinogenichealth effects could be evaluated only for arsenic. The limitations and methodology for thecarcinogenic evaluation are described on page 46. Results of those calculations (Table C) indicate that there is an increased risk of cancer for arsenic depending on length of exposure.
|CONTAMINANT||EXPOSURE PATHWAY||HEALTH GUIDELINE in mg/kg/day||SOURCE||EXPOSURE DOSE EXCEEDS HEALTH GUIDELINE|
|cadmium||soil||0.0007||MRL2||Yes for children|
|1 - An explanation of how exposure doses are calculated can be found in Appendix 3 along with Table C, which records the results of the calculations.|
2 - MRL = ATSDR's minimal risk level
Discussion of the Possibility of Health Consequences
Health assessors determine the possibility of health consequences by comparing the exposure tothe results of epidemiologic evaluations of human exposures to a chemical. If they do not havevalid human data, they use information from properly conducted animal studies. The type of dataused for an evaluation is indicated for each chemical. Usually, there is little or no information fora site on how much exposure is actually occurring, so we assume that maximum exposure hastaken place to insure that the public health is protected.
However, if there are valid data on exposure of area residents to site contaminants, we will usethese in deciding whether there is an ongoing public health hazard. For Murray, there are dataindicating that exposure to contaminants in soil is low, so that information was used indetermining the public health hazard of living in areas with contaminated soil.
Health effects due to arsenic are unlikely. For Grandview and Doc and Dell Mobile Home Parkchildren and adults, this conclusion is due to the apparent lack of exposure based on the results ofurine arsenic testing. This testing will be described in the Health Outcome Data Evaluationsection (page 28). For workers at the Metrowest Cement Plant, which is in sampling area EU3,this conclusion was based on the toxicological evaluation of the exposure doses for and exposuresituations at that facilities.
However, based on comparisons of the exposure doses to human data, some residents of theGrandview Mobile Home Park could experience health effects if sufficient exposure to arsenicin surface soil occurs (24). This conclusion also requires that the arsenic and lead in the soil arebeing readily absorbed into the bloodstream when ingested.
The conclusion that health effects in on site workers are unlikely is based on an evaluation ofworker exposure at the Metrowest Cement Plant which is the work location where contaminantlevels are the highest. We analyzed the 10 surface soil samples taken on the Metrowest facility. The exposure dose for the maximum arsenic concentration (1,900 ppm) at the plant is 1.25 timesgreater than the no observed effects level, but 14 times lower than the level where the first healtheffects (slight effects on the skin) were observed in a population that drank arsenic-contaminatedwater for 45 years (24). The exposure dose for the mean arsenic level at the plant, 406 ppm, is equal to ATSDR's Minimal Risk Level (MRL). In addition, arsenic levels at only 2 of 10sampling locations were above the mean level. Thus, the typical worker exposure level is lowerthan the mean. Health effects, thus, appear unlikely.
This conclusion about on site workers appears to differ from the conclusion of EPA's Murray riskassessment that there were significant health risks to workers (1). However, this apparentdifference is due to different exposure assumptions and different purposes. In this public healthassessment, we evaluated the existing exposure situation with the highest arsenic levels(Metrowest Cement Plant) and used a soil ingestion rate (50 mg/day) that we concluded wasappropriate for the work done at this facility.
EPA's baseline risk assessment identified possible risks for the whole site and all possible uses(34). Therefore, they used the maximum level found on site (a location no one currently works), the highest mean (no one works in half of this sampling area), and soil ingestion rates (240 & 480 mg/day) that are appropriate for occupations where there is intense soil contact such as landscaping and ditch digging. It was our conclusion that no one currently does this kind of work on site. However, they could be done in the future so it is very appropriate for EPA to use these rates in their risk assessment.
The above conclusion about the possibility of health effects if exposure to arsenic occurs arebased on one assumption important to this evaluation, the assumption that arsenic attached to soilmakes it into the bloodstream as easily as arsenic in water. People investigated in the healthstudies used to evaluate health effects were exposed to arsenic in water. It is much harder forcadmium and manganese to get into the blood from soil than from water (25). There are severalrecent studies that indicate that is true for arsenic also (26 - 28). If it is, the arsenic levels wouldhave to be higher before health effects would occur.
Exposure to arsenic at the Grandview Mobile Home Park represents a moderate increased risk ofskin cancer for individuals who live at the Park for many years (24, 25). For individuals living at the mobile home park for 5 or fewer years, there is no apparent increased risk of cancer. See page 45 for a discussion of the uncertainties found in any evaluation of cancer risk.
Exposure to arsenic for workers at the Metrowest Cement Plant represents a moderate increasedrisk of skin cancer for individuals who work at the plant for 30 years if the mean arsenic level(406 ppm) is used to calculate cancer risk (24, 25). However, if you remove the two highestconcentrations (1,800 & 1,900 ppm - which are at the southern edge of the plant) from thecalculations, there is no apparent increased risk of cancer. See page 45 for a discussion of the uncertainties found in any evaluation of cancer risk.
Based on human data, there is a possibility of health effects for pica children exposed to cadmiumin residential soil from the Grandview Mobile Home Park (33). Both the maximum and averagecadmium soil concentrations result in exposure doses for pica children that exceed the lowestobserved effect level in humans. No health effects appear possible for other children or for adults.
Small children (10 kilograms [kg]/22 lbs) who daily ingest 5 or more grams of soil (the habitcalled pica), contaminated at the maximum (84 ppm) or average (15.6 ppm) cadmiumconcentrations found at Grandview, could experience proteinuria. Pica is a uncommon conditionand can be short-term, so there were probably few, if any, children that had a significant exposureto cadmium. The lowest observed effect for ingestion of cadmium in humans is proteinuria, whichis the discharge of proteins from the kidney into the urine (33). Epidemiologic studies identifiedstatistically greater rates of proteinuria for individuals living a lifetime in cadmium-contaminatedareas in Japan, Belgium, and China than for individuals living in uncontaminated areas. Thesestudies did not specifically focus on children, so it is uncertain that children with a few years ofexposure, rather than the many years of exposure for adults, would result in proteinuria. Proteinuria is considered a mild adverse effect on the kidney.
Health effects due to exposure to lead-contaminated soil are unlikely, either for residents orworkers. As discussed on page 29, testing of children living in the Grandview and Doc and DellMobile Home Parks, indicates that blood lead levels were within a safe range. These mobile homeparks were identified as areas with high lead contamination in soil (Figure 6, page 16). Testing was done because there is good evidence from three literature reviews that children's blood leadlevels could have been elevated because of soil lead contamination (35-36). All three reviews concluded that soil lead levels of 1,000 milligrams per kilogram (mg/kg) would increase concentrations in blood from 0.6 to 65 micrograms per deciliter (µg/dL) with an average increase of 4-5 µg/dL. This wide range resulted from different sources of lead, exposure conditions, and exposed populations.
Further evidence for the need for blood lead testing came from an EPA evaluation of Grandviewsoil lead levels (4). EPA used these environmental lead sampling results in a model to predict therisk of elevated blood lead levels (> 10 µg/dL) in children of the Grandview neighborhood. TheEPA Integrated Exposure/Uptake Biokinetic (IEUBK) model predicted that about 10% of thechildren under 6 years old in the Grandview Mobile Home Park could have blood leads exceedingthe 10 µg/dL level of concern. This model uses actual soil and house dust levels along withassumed exposure levels in water, air, and food.
For on site workers, our conclusion that lead-related health effects are unlikely is based on areview of the soil sampling data for the areas where people actually work. For the MetrowestCement Plant, lead concentrations at 6 of the 10 sampling locations were below 500 ppm and 2 ofthe other 4 were between 500 - 2,500 ppm. Thus, most of the exposures a worker at Metrowestmight experience would be to lead concentrations below which EPA identified as a risk for lead-related health effects at the Murray Smelter site (1). Similar results were obtained when welooked at other on site workplaces.
Exposure to lead causes a wide range of effects (34). The level of lead in blood is a goodmeasure of recent exposure and also correlates well with health effects. Children are especiallysensitive to lead, and many of its effects are observed at lower concentrations in children than inadults. Levels of 10 µg/dL and perhaps lower in children's blood have been associated withdecreased IQ and impaired hearing and growth. Neurological effects may persist after exposurehas ceased and blood lead levels have returned to normal (37).
An exposure investigation of Grandview and Doc and Dell Mobile Home Parks residents wasconducted and is described below. However, no health outcome databases, such as cancermortality, cancer incidence, and birth defects, were evaluated in this public health assessmentbecause the number of people exposed (fewer than 300) is too small to be evaluated. However,skin cancer and perhaps liver, bladder, kidney, and lung cancer are plausible health outcomesbecause area residents are being exposed to arsenic, a known human carcinogen. A discussion ofwhy health outcome databases weren't evaluated and why certain cancers are considered plausiblefollows the discussion of the exposure investigation.
In collaboration with ATSDR, EPA, and ASARCO, the Salt Lake City-County HealthDepartment (SLCHD) conducted an investigation of blood lead and urine arsenic levels ofchildren and adults from the Grandview and Doc and Dell Mobile Home Parks during the week ofOctober 16, 1995 (40). SLCHD staff conducted a door-to-door survey of both mobile homeparks to identify the names and ages of all the children living in the two parks. Information onlead and arsenic was left at each household. During the survey and after obtaining informedconsent from the parent, handwipe samples were obtained from all 14 children in the target groupof 6 to 84 months old with residence in one of the mobile home parks for at least 3 months. While the emphasis of the investigation was on the 6 - 84 month target group, all mobile homepark residents were offered blood lead and urine arsenic testing.
On October 30 and 31, 1995, venipuncture blood samples were obtained from 40 individualsincluding 10 of the 14 children in the 6 - 84 month target group (40). First morning-void urineswere collected on two consecutive days from 36 residents including 7 of the 14 target groupchildren; a single sample was obtained from one person. All the blood and urine samples,including 8 control and 3 duplicate samples, were split and send to two different laboratories foranalysis.
The 40 blood lead samples ranged from below the detection limit of 1 microgram of lead perdeciliter of blood (µg/dL) 7.1 µg/dL with a mean of 3.4 µg/dL (40). For the ten children from thetarget group of 6 to 84 months old, results ranged from 3.9 - 5.7 µg/dL with a mean of 4.7µg/dL. All the samples were below the Centers for Disease Control and Prevention's (CDC)recommended action level of 10 µg/dL.
Sixty-eight of the 73 urine arsenic samples analyzed (two each for 36 people; 1 sample from 1person) were below a detection limit of 2 µg of arsenic per liter of urine (40). The four samplesabove the detection limit ranged from 2 µg/L to 3.7 µg/L. For the 14 urine samples taken fromthe 7 children 6 - 84 months old, one was 2.2 µg/L and the rest were below the detection limit. All the samples were below 20 µg/L which ATSDR considers the upper limit of background ornormal concentrations.
As indicated by the low blood lead and urine arsenic levels found in SLCHD's exposureinvestigation, the residents of the Grandview and Doc and Dell Mobile Home Parks are not at riskfor lead- or arsenic-related health effects. The low urine arsenic and blood lead levels areprobably due to limited exposure to the arsenic- and lead-contaminated soil.
Poor absorption of the lead into the bloodstream from the digestive tract does not appear to be afactor. EPA conducted studies to evaluate how well lead and arsenic from Murray area soils andslag are absorbed in pigs. The results for lead are available and about 27% of the lead in slag and36% of lead in soil appears to be bioavailable (i.e., it moves from the soil in the digestive tract intothe blood) (41). These results are close to the expected level of 30%.
Why Health Outcome Databases Were Not Evaluated
Health outcome data are evaluated if it is biologically plausible for a health outcome to occur or ifthe community is concerned about specific health outcomes and if it is possible to identify theappropriate data with which to evaluate a health outcome. For biological plausibility, the decisionto evaluate health outcome data depends on whether a completed exposure pathway exists for achemical suspected of causing the health outcome of concern (22). The selection of anoncarcinogenic health outcome is based on a review of the toxicologic literature for thatcontaminant of concern.
When a contaminant of concern has been identified as a carcinogen, health outcomes for themajor anatomical sites are usually selected for evaluation (22). Designating a chemical as acarcinogen for purposes of health outcome data evaluation is based on its classification as such bythe National Toxicology Program, the International Agency for Research on Cancer, EPA, andthe United States Occupational Safety and Health Administration.
A latency period of at least 10 years between exposure and diagnosis has been observed in moststudies of human cancer (23). If exposure began less than 10 years before the latest dataavailable, analysis of health outcome data for cancer incidence or mortality is not likely to beuseful, particularly if the exposure level is low.
An important factor in evaluating health outcome data in any situation is the difference in sizebetween the population at risk of exposure to site contaminants and the smallest population unitfor which health outcome data are available (22). For example, adverse health effects due to asite would likely not be observed if the population at risk is 100 and the population unit for whichhealth outcome data are available is 100,000. That is the reason we have not evaluated cancerincidence data in this public health assessment. The only available cancer data were for the zipcode around the Murray Smelter Site, which has a population of several thousand, while theexposed population appears to be fewer than 300.
While it was not possible to evaluate cancer incidence data, cancer is a plausible health outcomebecause there is exposure of area residents to arsenic. Long-term ingestion of inorganic arsenic isknown to cause skin cancer (24). Some evidence also links liver, bladder, kidney, and lung cancerto ingestion of arsenic.