HEALTH CONSULTATION
JACOBS SMELTER SITE
STOCKTON, TOOELE COUNTY, UTAH
BACKGROUND AND STATEMENT OF ISSUES
Mr. Jeff Coombs, Director of Environmental Health, Tooele County Health Department (TCHD) requested that the Environmental Epidemiology Program (EEP) review the potential for adverse health effects resulting from exposure to lead and arsenic in the soils at Stockton, Utah. The U.S. Environmental Protection Agency (USEPA) has conducted a survey of soil lead and arsenic levels. The TCHD, with assistance from USEPA, conducted a survey of blood lead levels and urine arsenic levels.
The Jacob's Smelter site is located in the town of Stockton, Tooele County, Utah. Stockton is a community with 437 residents located on State Route 36, approximately 5 miles south of Tooele City, Utah. The town is approximately 45 miles southwest of Salt Lake City, Utah. Development of the mining industries in Stockton started following the discovery of silver and lead in the foothills east of the town. Numerous smelters were built around Stockton to support more than 100 operating mines and leases. Mining activities were at their height during the 1870s (1, 2).
In 1997, the Utah Department of Environmental Quality (UDEQ) collected 29 soil samples from Stockton and the surrounding area. Analysis of the samples revealed the presence of elevated levels of lead (maximum = 68,400 mg/kg of soil) and arsenic (maximum = 30,400 mg/kg of soil) in the soil. The concentrations of those metals are much higher than are usually encountered in residential areas and could be a potential health concern to area residents (2).
Following the discovery of high levels of lead and arsenic in residential area soils, USEPA and the Bureau of Reclamation (BOR) conducted a much more extensive soil sampling study of the area to identify residences where the lead levels were above 3,000 mg/kg of soil. The results of that investigation were presented to the community on January 21, 1999, (3) and emergency remedial action was begun March 1, 1999, to remove those soils.
Soil Lead Concentrations: Four hundred eighty seven surface soil samples (0-2 inches) were collected from 248 properties within the residential area during the summer months of 1998. Those samples were evaluated for lead and arsenic using X-ray fluorescence (XRF) technology. The soil concentrations of lead ranged from 13 mg/kg to 41,537 mg/kg, with an average concentration of 1,474 mg/kg (2). Figure 1 presents a map of Stockton showing the lead concentrations (4). Ten percent of the samples were also analyzed by Inductive Coupled Plasma Mass Spectrometry (ICP-MS). Subsurface samples were taken from 242 of the original sampling sites for samples 2-6, 6-12, and 12-16 inches below the surface. The soil lead levels were consistent through the different depths, indicating that no gradient of concentration of lead is in the soil as a function of depth. The primary phase of lead in the soil is cerussite (PbCO3), which accounts for approximately 73% of the soil lead mass. The lead bearing soil particles tended to be small (< 100 µm in diameter) and are not tightly bound or integrated with the surrounding matrix, increasing the bio-availability (2).
Soil Arsenic Concentrations: Difficulties were encountered in detecting arsenic by the XRF method because of strong masking by the presence of high levels of lead in the sample. However, laboratory analysis via ICP demonstrated a strong correlation between lead and arsenic, making it possible to estimate the concentrations of arsenic in the soil. The estimated soil concentrations of arsenic ranged from 12 mg/kg to 2,728 mg/kg with an average concentration of 108 mg/kg. The primary phases of arsenic are lead arsenic oxide (PbAsO, 52% of the soil arsenic), arsenic iron oxide (AsFeO, 34%), and arsenic iron sulfide (AsFeSO4, 12%). Most of the particles are small (<100 µm in diameter) and are almost completely (87-100%) liberated from the surrounding soil matrix (2).
House Dust Lead and Arsenic Concentrations: Indoor house dust samples were obtained from a total of 23 residences in Stockton. Samples were collected from three locations (each 0.33 m2) within each residence. Samples were analyzed for lead and arsenic. Indoor dust lead levels ranged from 103 mg/kg to 1,370 mg/kg with a mean lead concentration of 455 mg/kg. Indoor dust arsenic levels ranged from 8 mg/kg to 153 mg/kg with a mean lead concentration of 40 mg/kg (2).
Potential for Lead Contamination in the Drinking Water: All residences in Stockton are on a community water source. Water is obtained from Soldier Canyon and is processed by a slow sand filter treatment plant (6). First flush water samples were taken from 23 homes. The measured concentration of lead in the tap water ranged from <2 to 5 µg/L with an average lead concentration of 1.2 µg/L (2).
During September of 1998, Tooele County Health Department (TCHD) and USEPA conducted a biomonitoring study among residents of Stockton to investigate exposure to lead and arsenic. Participants were identified by conducting a door-to-door survey and selected from residents living within areas where the soil lead level was above 500 ppm (500 mg / kg of soil). Fourteen homes with children less than seven years of age were identified in the study area. A total of 26 children is living in the study area. Residents from eight of the 14 homes with children and residents from six additional homes participated in the study. Blood lead levels were measured for 16 of the 26 children that were less than seven years old and 10 older persons (7 to 21 years of age) from those homes (1). Urine arsenic levels were measured for 10 children that were less than seven years old and 22 older persons (7 to 63 years of age) from those homes (1, 2).
All blood lead tests were below 10 µg/dL. All urine arsenic tests, except one, were below the detection limit (<15 µg/L). The one elevated arsenic level was found to be organic arsenic and was attributed to diet and not to environmental exposure to the arsenic in the soil in Stockton (1).
Public Health Concerns and Demographics
Chemicals of Concern: Lead and arsenic are present in the soil at concentrations that pose potential adverse health effects to exposed persons. House dust samples collected indicate that excessive indoor lead and arsenic contamination from the soil is not occurring (2). However, the baseline risk assessment discussed the relative liberation and bio-availability of the metal-containing particles. This suggests that while a completed pathway may not be shown for inside homes, there is a high potential for adults and children working and playing in their yards and surrounding contaminated areas to be exposed. Since all residences are connected to a community public water supply which is offsite, water is not a source of exposure.
Possibly Exposed Population: The population of Stockton is a predominately white community of approximately 437 residents. Approximately 6% of the population is Hispanic (5). Approximately 80 children, ages 0-6 years old, live in Stockton, with 26 children living in areas in which the soil lead concentration was detected above 500 ppm. The majority of the residents live on the east side of Highway 36 (Conner Avenue) and in the northern half of the community. School children are bussed into Tooele (approximately 5 miles to the north). Blood lead levels and urine arsenic measurements in study participants indicate that children and adults were not exposed to excessive levels of either lead or arsenic from the contaminated soil.
Adverse Health Effects of Lead Exposure: Lead poisoning is the most significant and prevalent disease of environmental origin in the United States, particularly among children. Lead exposure in children is a particular hazard because children absorb lead more readily than do adults. Environmental lead is a toxic substance that is affecting the growth and development of up to one million U.S. preschool children today, with effects that include learning disabilities and possibly more serious effects, depending upon blood lead levels (6). High levels of lead can adversely affect many systems in the body, including the neurological, reproductive, gastrointestinal, hematopoietic, and renal systems (7). The effect of lead that is usually considered to be of the greatest concern in children is the impairment on the neurological system and the resulting developmental and behavioral problems (2, 6). Blood lead levels as low as 10 µg/dL can adversely affect the behavior and development of children (8). Figure 2 provides shows blood lead levels at which the lowest observed health are seen (12).
During September of 1998, TCHD and EPA tested the blood lead levels of a small group of residents of Stockton living within areas where the soil lead level was above 500 ppm. All blood lead test results were below 10 µg/dL, within the normal range. Based on the limited data obtained by TCHD and EPA, the residents of Stockton did not have significant lead exposure from the contaminated soil or from other sources prior to September 1998. Blood lead tests can only detect recent lead exposure and cannot provide accurate information on exposure that occurred earlier than two to three weeks prior to testing (8).
Studies have found that on a volume basis, up to 16% of house dust was lead dust derived from a paint source and up to 26% of house dust was lead dust derived from mining wastes. Those studies suggest that the contribution of lead from mining and smelting wastes were at least as important a source as lead-based paint for exposure of children to lead (10, 11).
Adverse Health Effects of Arsenic Exposure: Organic arsenic is relatively non-toxic. However, ingestion of as little as 20 mg of inorganic arsenic may produce life-threatening toxicity. The most sensitive body sites to arsenic include the respiratory system, the liver, the heart, the hematopoietic system, the kidneys, and central nervous system (9).
Arsenic can enter the body by ingestion and inhalation. Absorption by ingestion is generally rapid and complete. Absorption by inhalation with the exception of certain salts of arsenite and arsenate are also rapid and nearly complete. Dermal contact may result in some localized toxicity; however, there is no evidence of direct dermal absorption of arsenic. The half-life of whole body arsenic is approximately five days (9).
The TCHD and EPA investigation conducted in September 1998 included arsenic exposure testing. No one tested was found to have elevated levels of arsenic in their urine that could be attributed to arsenic from the site. The one elevated arsenic level was attributed to diet.
Approximately 80 children under the age of seven years old live in Stockton, and 26 children live in areas with soil lead levels above 500 ppm. Young children are at particular risk from environmental exposure to lead and arsenic because they are more sensitive to the toxic effects of those metals. Children are less developed and may have developmental harm from exposure that would not be experienced by a completely developed adult. Neurological development is of particular concern for children because lead and arsenic exposure can cause learning and behavioral disabilities. In addition, children are more likely to have behaviors that will increase soil exposure.
The Jacob's Smelter Site is considered a public health hazard (ATSDR health hazard category B) because of the high levels of lead and arsenic in the soil in residential areas. However, biological testing for blood lead and urine arsenic did not indicate that the residents were exposed to excessive levels of lead or arsenic.
Emergency cleanup efforts have begun to remove the most accessible layer of dirt (the top eighteen inches) with plans to evaluate the site for further remediation. The cleanup activities will remove the health hazard associated with the contaminated soil. However, during the cleanup process, the community may be exposed to high levels of lead or arsenic from the contaminated dust generated during the soil removal activities.
EEP will work with the TCHD to provide effective community education about the risks of lead and arsenic exposure to the community during the cleanup process and about methods to reduce exposures to lead and arsenic.
EEP will assist TCHD in monitoring the efficacy of EPA's emergency response clean-up activities to minimize exposure of the residents of Stockton to lead-contaminated soils. EEP will review data reported to the Utah Blood Lead Registry for trends in blood lead levels among Stockton residents and will provide summary reports of those trends to UDEQ and to TCHD.
EEP will work with TCHD to encourage continued screening of children in Stockton for blood lead levels and will monitor the results of that screening in order to identify any increases in blood lead levels that may indicate increased exposure.
Samuel D. LeFevre, M.S., Epidemiologist
Environmental Epidemiology Program
Bureau of Epidemiology
Utah Department of Health
R. Wayne Ball, Ph.D., DABT
Toxicologist
Environmental Epidemiology Program
Bureau of Epidemiology
Utah Department of Health
This Jacob's Smelter Site Health Consultation was prepared by the Utah Department of Health, Environmental Epidemiology Program under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the public health consultation was begun.
Gail D. Godfrey
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.
Sven Rodenbeck
Chief, SPS, SSAB, DHAC, ATSDR
Table 1. Summary of Environmental Data for Stockton, Tooele County, Utah, Collected by the U.S. Department of Environmental Quality During the Summer of 1998.
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Figure 1. Map of Stockton, Tooele County, Utah Showing Soil Lead Levels.
Figure 2. Lowest Observable Adverse Effects Levels of Inorganic Lead on Children and Adults (12)
Table 2. Completed Environmental Exposure
Pathways
| Pathway Name: | Source | Medium | Exposure Point | Exposure Route | Receptor Population | Time of Exposure | Exposure Activity | Estimated Number Exposed | Chemicals (identify by name or reference to tables in document) |
| Residential Soil | Smelter Tailings | Soil | Residential Property | Ingestion of Soil | Stockton Residents | Past, Present, Future |
Activities in yard. Gardening. |
437 total 26 children |
Lead Arsenic |
| Ingestion of Produce | Eating produce from home garden. | ||||||||
| Inhalation of Contaminated Dust | Wind blown dust. |
Table 3. Potential Environmental Exposure
Pathways
| Pathway Name: | Source | Medium | Exposure Point | Exposure Route | Receptor Population | Time of Exposure | Exposure Activity | Estimated Number Exposed | Chemicals (identify by name or reference to tables in document) |
| Residential Soil | Smelter Tailings | Soil | Residential Property | Ingestion of Soil | Stockton Residents | Past, Present, Future |
Activities in yard. Gardening. |
437 total 26 children |
Lead Arsenic |
| Ingestion of Produce | Eating produce from home garden. | ||||||||
| Inhalation of Contaminated Dust | Wind blown dust. |
Table 4. Exposure and Demographic Table
| Pathway Name | Unknown |
Estimated Pop. in Pathway |
Range Minimum |
Range Maximum |
| a. Pot. Pathways On-site |
437 |
400 |
500 |
|
| b. Pot. Pathways Off-site | 0 | 0 | 0 | |
| c. Total Pot. On and Off-site | 0 437 (26 children 0-6 years of age) |
400 22 children |
500 80 children |
|
| d. Compl. Pathways On-site | 437 (26 children 0-6 years of age) |
400 22 children |
500 80 children |
|
| e. Compl. Pathways Off-site | 0 | 0 | 0 | |
| f. Total Compl. On and Off-site | 437 (26 children 0-6 years of age) |
400 22 children |
500 80 children |
|
| g. Pot and Compl. Pathways On-site | 437 (26 children 0-6 years of age) |
400 22 children |
500 80 children |
|
| h. Pot and Compl. Pathways Off-site | 0 | 0 | 0 | |
| i. Total Pot. And Compl. On and Off-site | 437 (26 children 0-6 years of age) |
400 22 children |
500 80 children |
