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1. ATSDR > Public Health Assessments & Consultations

HEALTH CONSULTATION

BUNKER HILL MINING AND METALLURGICAL
KELLOGG, SHOSHONE COUNTY, IDAHO

DISCUSSION

In this health consultation, ATSDR will review available sampling data for surface soil, household dust, and blood lead to determine if the above site-wide objectives are being met and to determine if the lead is present in these media at levels of public health concern. ATSDR will also review available air sampling data to evaluated whether the levels of particulates and lead in fugitive dust are a public health concern. In order to evaluate the effectiveness of the soil remediation barriers, ATSDR's evaluation will focus on sampling data for the city of Smelterville because Smelterville is the only site community in which remediation of residential yards, commercial properties, and ROWs has been completed. In addition, ATSDR will limit its review to data collected in Smelterville from 1997 to present because soil remediation activities in Smelterville were not completed until 1997. Sampling data for heavy metals other than lead will not be reviewed or evaluated in this health consultation.

Surface Soil

Lead levels in soil samples from residential yards in Smelterville for the last 3 years are shown in Table 1. Soil samples were collected in two different ways: (1) from yards of homes with children who participate in the annual blood lead screening program, and (2) from yards of all cooperating homes in the community (not just those with children). As shown in Table 3, over the last 3 years, lead levels in both sampling categories met the site RAO goals for residential soil of 350 mg/kg as a community wide geometric mean and 1000 mg/kg for any individual yard. In addition, the geometric mean soil concentrations are below the EPA national soil screening level of 400 mg/kg.

Table 1. Lead Levels in Smelterville Residential Yards

Household Dust

Lead levels in household dust inside Smelterville homes were measured in 1997, 1998, and 1999 by both vacuum bag sampling and by dust map sampling. Separate lead dust studies were conducted by the Idaho Panhandle Health District (PHD) and by TerraGraphics Environmental Engineering, Inc. (TerraGraphics). The PHD studies were generally limited to those homes where children resided and had participated in previous blood lead screenings while the TerraGraphics studies included homes with and without children.

As shown in Tables 2a and 2b, the lead levels were generally higher in samples from the dust mats than in samples from the vacuum bags. By 1999, geometric mean dust levels, as measured by vacuum bag sampling, were below the 500 mg/kg RAO in homes with children and slightly above the RAO in homes community-wide. In addition, dust levels in vacuum bags from some individual homes continued to exceed the maximum RAO of 1000 mg/kg. Dust mat samples from homes with children and from homes community-wide exceeded both the geometric mean RAO and the maximum individual house RAO throughout the last 3 years.

Ingestion of housedust lead has been identified as a major route of lead exposure (especially for younger children) at the site. According to EPA reports, reducing geometric mean housedust lead concentrations to 500 mg/kg (the dust lead RAO) or less is required to achieve the site-wide child blood lead RAOs. Even then, some individual children, especially those living in homes with unremediated yards and with housedust levels at or near the maximum ROA (1000 mg/kg), may have a greater than 5% chance of exceeding the blood lead levels of concern (10 ug/dL).

Table 2a. Smelterville Indoor Dust Lead Levels - Homes with Children¹

Table 2b. Smelterville Indoor Dust Lead Levels - All Homes¹

Blood Lead

Blood lead levels in area children age 9 months to 9 years have been monitored yearly by the PHD since 1988. The most recent blood lead levels for children in Smelterville are shown in Table 3. Blood lead levels in Smelterville children have generally been declining over the past several years as more residential yards, commercial properties, and ROWs are remediated. In 1999, the blood lead RAO that requires less than 5% of children to be above 10 ug/dL was achieved. However, the blood lead RAO that specifies that no child be above 15 ug/dL was not.

Site-wide, one and two year old children generally have the highest average blood lead levels and the highest incidences of elevated blood lead levels (>10 ug/dL) among all age groups. As such, it is possible that including blood lead data for older children (e.g. 9 year olds) may "dilute" the higher levels found in younger children. Therefore, the broad age range (9 months-9 years) used to report blood lead levels may underestimate the site's public health risks for younger children.

Table 3. Blood lead levels in Smelterville children (age 9 months - 9 years)

Ambient Air (Fugitive Dust)

Lead and Total Suspended Particulate (TSP) levels in ambient air have been monitored in Kellogg (at the Kellogg Medical Clinic) for many years. Monitoring data from the last 9 years (1990-1998) are shown in Table 4. Lead air levels at the Kellogg station have not exceeded the National Ambient Air Quality Standard (NAAQS) of 1.5 ug/m³ (quarterly average) since the smelter shut down in 1981. In addition, long-term (i.e., yearly) TSP levels have not exceeded the NAAQS for particulate matter less than 10 microns (PM10) of 50 ug/m³ (annual average) since 1992. In contrast, short-term (i.e, daily) TSP levels have exceeded the NAAQS of 150 ug/m³ (24hr average) periodically since 1990. However, no exceedences have occurred in the last few years (since 1995).

Ambient air monitoring at sampling stations in other site communities, including Smelterville, was discontinued in 1988. Therefore, no sampling data are available to evaluate ambient levels of lead or particulates in these communities since remediation of residential yards began in 1989.

Table 4. Ambient Air Lead and TSP Levels at Kellogg Medical Clinic Station

Localized air monitoring to evaluate fugitive dust levels during remediation activities conducted by the U.S. Army Corps of Engineers (ACOE) and the Upstream Mining Group (UMG). From 1995 to 1999, the ACOE collected approximately 800 samples for TSP around 7 cleanup areas; most of these samples were also analyzed for lead. The data from these samples indicate that the TSP levels exceeded the 24-hour NAAQS standard (150 ug/m³ PM10) 47 times. The majority (39 out of 47) of the exceedences reportedly occurred in 1997 and 1998 around heavy haul-route areas such as the "Multiplate" (overpass) structure in Smelterville. During the 5 year monitoring period, the annual average lead concentrations, which ranged from 0.150 ug/m³ to 0.355 ug/m³, never exceeded the NAAQS (1.5 ug/m³).

The UMG has monitored TSP and lead air concentrations during their yard remediation activities since 1994. TSP levels were measured weekly in real time (instantaneously) around the soil cleanup areas, and lead levels were measured daily in the personal breathing zone of remediation workers. From 1994 to 1999, out of more than 2300 monitoring records, no exceedences of the Occupational Safety and Health Administration (OSHA) standard for TSP (15 mg/m³) were recorded, while the OSHA permissible exposure level (PEL ) for lead (50 ug/m³) was exceeded 3 times and the OSHA action level (30 ug/m³) was exceeded once in the workers' personal breathing zone.

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