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PUBLIC HEALTH ASSESSMENT

CAL WEST METALS (USSBA)
LEMITAR, SOCORRO COUNTY, NEW MEXICO


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

Findings from previous investigations of environmental contamination at CWM have been reviewed by ATSDR. Unless otherwise stated, the environmental data presented are from the EPA Record of Decision (ROD) (1). The environmental data presented relate to possible exposure pathways at CWM as discussed above. ATSDR selects and discusses contaminants based on several factors: sample design, field and laboratory data quality, and comparison of chemical concentrations to levels that could cause cancer or other health effects. Community health concerns are also considered.

Table 2 lists contaminants detected in on-site surface soil and sediment (0-6 inches) at concentrations exceeding comparison values. Comparison values are amounts of contaminants found in specific environmental media (i.e., air, groundwater, soil, and sediment) that are used to determine whether those contaminants should be discussed further in the PHA. Those values were developed by ATSDR and other agencies as guidelines for estimating how much of a contaminant per day an average person can be exposed to with no harmful health effects. Comparison values are very conservative (i.e, they are very protective of public health) and are calculated based on "worst case scenarios."

Environmental contamination relating to possible exposure pathways at CWM is grouped by the type of medium (e.g., soil, groundwater, etc.) in which contaminants were detected. The media discussed are soils and sediments, contaminant waste source, groundwater, and air.

A. On-site Contamination 1. Soils and Sediments

Analytical measurements made by the EPA found three inorganic contaminants at levels above comparison values in soils and sediments: lead (maximum of 7,690 ppm in surface soil and 836,000 ppm in sediments), antimony (maximum of 101 ppm in surface soil and 1,160 ppm in sediments), and arsenic (maximum of 32 ppm in surface soil and 704 ppm in sediments in the trench area) (see Table 3). Cadmium, mercury, nickel, and silver were detected, but at levels below comparison values (i.e., levels of concern for further analysis). Semi-volatile organic compounds identified for further evaluation are the polynuclear aromatic hydrocarbons (PAHs) (6).

The EPA modeled exposure source contributions of lead using the Uptake/Biokinetic (UBK) model. That model determined that the battery source waste materials posed a threat to public health through inhalation and ingestion of contaminated soil (i.e., dust containing contaminant particles) if people were to come into close contact with the site.

The future scenario for the CWM property is residential use. The UBK model was used to calculate blood lead concentrations in children ages 0-6 using given environmental exposures. The following exposure routes were examined using the model: 1) ingestion of soil and dust, 2) ingestion of water, 3) ingestion of food, 4) inhalation of air, 5) exposure of a fetus through the maternal route (lead from the mother readily passes the placenta [8]), and 6) ingestion of paint chips (which is not applicable at this site). The UBK model, then, estimates the risk from lead using concentrations from all environmental media (1).

For CWM, only soil concentrations were varied in the UBK calculations. Site-specific concentrations that were detected during sampling were used for air and drinking water. In other words, at CWM the UBK model estimates the maximum amount of lead that could be present in soil to help ensure that harmful lead exposures do not occur if the site is used for residential purposes in the future. Since the estimates were based on exposures to children from ages 0-6, the findings are very conservative and protective of public health (i.e., children are typically affected more by a given level of exposure than are adults).

It was determined that the cleanup level would have to be 640 ppm for the land to be used as residential property; that level complies with limits set by EPA's Office of Solid Waste and Emergency Response (Directive 9355.4-02), which sets recommended cleanup levels for lead in soil of 500-1,000 ppm (1). In other words, an average lead concentration in soil at CWM of 640 ppm would not cause blood lead levels to rise to harmful levels in future residents.

A field portable x-ray fluorescence (FPXRF) survey was taken during Phase II of the Remedial Investigation by EPA to find out if lead contamination at the site is widespread. An X-Met 880 field portable instrument was used to measure lead concentrations. Grids measuring 100 feet x 100 feet were surveyed and staked at the site. The area was extended 400 to 500 feet north, south, and west of the fenced area (Fig 3). The X-Met was used to measure lead concentrations at the grid intersections and at points outside the grid area. Of the 203 samples taken, 145 were surface samples. Using the results from this survey, an isopleth diagram outlining the areas of contamination and their approximate lead concentrations was drawn (Figure 4). It was determined that approximately 8 of the 43.8 acres of surface area were contaminated above the cleanup level of 640 ppm. According to the figure, those eight acres included both an area north of CWM outside the fence and a large area inside the fence (6).

Antimony was detected at levels above comparison values in the battery and sludge sediments (1,160 ppm), as well as in the pond (581 ppm). Arsenic was detected above comparison values only in the trench area (704 ppm). Again, those comparison values are very protective of public health. A person would have to be exposed to the contaminants at the levels detected on a daily basis and for long periods of time to experience adverse health effects; such exposures were unlikely at the CWM site.

2. Contaminant Waste Source

Field investigations, which took place during the Phase I and Phase II Remedial Investigation by EPA, showed that hazardous substances were present in several sources. Those sources included the broken battery waste piles, dried sludge waste sediments, and sediment from the evaporation ponds.

The highest concentrations of contaminants were found within the fenced area of the CWM site. The highest concentrations of lead were found in the battery and sludge sediments. Polynuclear aromatic hydrocarbons (PAHs), which are associated with plastics and rubber products, were the predominant semi-volatile organic compounds detected in the samples.

As part of testing for chemical contamination on site, the southwest berm area was trenched and then sampled. Arsenic (704 ppm) and lead (51,100 ppm) were the only contaminants found to be above the comparison levels in the trench area (Table 3).

3. Groundwater

Groundwater was tested from a pre-existing monitoring well (CWMW-2) and two supply wells (CWSW-1 and CWSW-2) during Phase I investigations on site (see Figure 2). Six wells were constructed for the Phase II investigation (CWMW-4 to CWMW-9) and were sampled at that time along with the three pre-existing monitoring wells (CWMW-1, 2, and 3). The monitoring wells were used only for sampling, not as potable water sources. Those samples were all tested for target analyte list (TAL) metals; TAL metals are metals that are commonly found in the environment and that are typically sampled for in site investigations. Only unfiltered samples were targeted during Phase I examination. Samples from the new and old monitoring wells were taken October 29-30, 1991, during Phase II. Filtered and unfiltered samples were examined for TAL metals. Lead levels from all of the newly constructed monitoring wells on-site were below the New Mexico ground water standard of 0.05 ppm, and the EPA action level of 0.015 ppm. Unfiltered samples from the old monitoring wells were slightly elevated for lead levels during Phase II testing. Wells CWMW-1, CWMW-2, and CWMW-3 had levels of 0.090, 0.043, and 0.035 ppm, respectively. Groundwater samples collected during Phase I and from wells CWMW-5, CWMW-7, and RW-1 during Phase II were also analyzed for TAL organic compounds, but no volatile or semi-volatile organic compounds were detected.

4. Air

Air samples were collected during field activities of Phase II of the remedial investigation, during the week of September 23, 1991. Temperatures ranged from 48o to 86oF. Winds were from a southerly direction at average speeds of 5 to 13 miles per hour (1).

Samples were taken next to the trenching operations, and upwind and downwind of the source waste materials found on site at CWM (1). Thirty-two samples were collected and analyzed for PAHs and 11 metals (1). Lead was detected at concentrations below standards in most of the air samples tested. One air sample measured 35.6 micrograms per cubic meter (1), which was above the National Ambient Air Quality Standard of 1.5 micrograms per cubic meter for lead. That sample was collected during trenching operations when soil was being disturbed; on-site remedial workers took proper safety precautions so that chances of harmful exposures were minimal. The nearest households are 1,000 feet northeast and southeast of the site on the other side of Interstate 25 and Lemitar is one-half mile to the southeast, also on the other side of the highway, so it is highly unlikely that lead concentrations of that magnitude would have reached populations off site, especially for a period of time that would cause adverse health effects.

B. Off-site Contamination

1. Soils and Sediments

An assessment was made to determine if contaminants had migrated off-site. Sediment samples were collected off-site north and south of CWM (Figure 5). The samples were taken from the drainage areas of the arroyos. Eight samples were taken in these areas during the Phase I investigation. All samples were surface samples. Two samples were taken south of CWM (one 100 feet away from the fence and the other 200 feet away), and six samples were taken 200 feet or less north of the fenced area, as seen in Figure 5. A background sample was collected about 200 feet west of the site (1).

The samples were analyzed for TAL metals and organic compounds. Lead was the only substance detected at concentrations above the comparison level in the north and south sampling areas. Runoff from the battery waste piles is the most likely source of drainage contamination because the piles were outside where no containment measures were used. The arroyos off site are not in an area that people are likely to pass through very often, so it is not likely that anyone was exposed to lead in this area long enough to suffer any ill health effects.

2. Groundwater

Residential wells north and south of CWM were monitored for contamination in 1979, 1981, 1985, 1990, and 1991. Residents at those locations had already switched to municipal water prior to sampling because their well water tasted bad and they thought that it may have been contaminated. Water from the wells is still used for irrigation. All of the wells draw water from the aquifer of concern, which lies beneath the CWM site. The water samples, which were all unfiltered, were tested for TAL metals and for general water quality. The northernmost residential well (RW-1) was chosen for background comparisons. Lead was below 0.002 ppm and all other metals were also detected below health standards in RW-1 (1).

Analytical results from the sampling of private wells "indicate that there has not been a release of hazardous substance metal contaminants from site waste sources to the groundwater beneath the Cal West site" (1). The highest lead concentration found was 0.06 ppm detected in RW-2 in 1981; that level is slightly above New Mexico's action level for lead of 0.05 ppm and EPA's maximum contaminant level (MCL) of 0.015. All other lead concentrations from RW-2 were below both EPA and New Mexico action levels. RW-2 is not in the path of groundwater flow from CWM, which means that the one slightly elevated lead sample most likely resulted from another source (1,5). One such common source of slightly elevated lead is leaching of lead solder from plumbing (8).

Manganese was detected in groundwater at concentrations above the MCL of 0.05 ppm in all residential wells tested. Iron concentrations in groundwater also exceeded the MCL of 0.3 ppm in RW-2, RW-3, RW-4, and RW-5. Those levels of iron and manganese measured in the residential wells represent the background water quality in the area because elevated levels were detected in all domestic wells tested, including those both upgradient and downgradient of the site. In addition, the MCLs for iron and manganese are for taste and odor, not health purposes (8). In other words, someone would have had to consume those metals in amounts substantially higher than detected to suffer any health problems. Groundwater from all residential wells also contained Total Dissolved Solids (TDS) at levels above the EPA water quality standard of 500 ppm. The sulfate level in RW-2 was 593 ppm, which exceeds EPA's water quality standard of 250 ppm. Those iron, manganese, TDS, and sulfate levels indicate that groundwater in the area is of relatively poor quality (1). Again, those wells are no longer used as potable water sources; the residences had switched to the Polvadera water supply prior to any sampling.

Flowing water was not present in the arroyos during the period of time when sampling occurred, and there are no rivers in the immediate vicinity of CWM. There was therefore no surface water to test during the remedial investigations (5).

C. Quality Assurance and Quality Control

In preparing this Public Health Assessment, ATSDR relied on the information provided in the referenced documents. The Agency assumed that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analyses and the conclusions drawn in this document are determined by the availability and reliability of the referenced information.

Upon review of documents related to CWM, it appeared that the appropriate samples were collected at the site. Contaminants which would be of concern at a battery smelting operation were examined by the laboratories. Any discrepancies that were detected by EPA were clarified by the contract laboratories. Data were clearly marked to indicate the types of dilutions used in the laboratory determinations. Data that were not within the detection limits of the assays were clearly marked on the data sheets (1,4).

D. Physical and Other Hazards

Buildings on the CWM property were not properly secured at the time of the site visit. A number of physical hazards were present, and a variety of chemicals were found in one building. The site has since been cleaned up, however. All physical hazards have been removed, along with the chemicals. The buildings have been cleaned and secured.

PATHWAYS ANALYSIS

To determine whether people are exposed to contaminants migrating from CWM, ATSDR evaluated the environmental and human components that lead to human exposure. A pathways analysis consists of five elements: a source of contamination (e.g., landfills or lead piles), an environmental medium (media) through which contaminants move (e.g., movement of contaminants through groundwater or the air), a human exposure point (e.g., contaminated private wells or dust containing contaminants on a site), a human exposure route (e.g., ingestion, breathing, or contact with the skin), and a potentially exposed population (e.g., people using private well water or breathing in the dust particles). Unless noted, the information used in the pathways analysis was found in the ROD and the trip reports.

ATSDR identifies exposure pathways as completed or potential. Completed exposure pathways exist when the five elements of a pathway link the contaminant source to an exposed population. Potential exposure pathways exist when information on one or more of the five elements is missing.

A. Completed Pathways

Although there were sources of environmental contamination on-site at CWM before the site was cleaned up, one or more of the five elements of a pathway discussed above were absent for the pathways developed at this site. No completed human exposure pathways were therefore identified at the CWM site.

B. Potential Pathways

1. On-Site Media

Trespassers may have been exposed to environmental contaminants on-site, but, again, types of exposures to trespassers, if any occurred, cannot be determined due to insufficient information about their activities at the site. Those exposures would have been intermittent at worst.

A potential existed for short-term exposures to contaminated sediments and soils, ambient air, and lead wastes from batteries to anyone who visited the site. A variety of laboratory chemicals were found in one of the buildings. Those chemicals represented a potential exposure pathway for trespassers on the CWM site; those exposures would have been short term if they occurred at all. The soils and sediments on and around the site have been cleaned up and the chemicals have been removed. The potential for any exposures has therefore been eliminated.

2. Off-Site Media

Lead from battery wastes that got into the soil may have been dispersed to nearby off-site areas by strong winds in the past. However, the lead levels detected in soil samples taken 200 to 300 feet outside the fenced area do not suggest that depositional lead through the air was a substantial problem. The maximum lead level beyond the fenced area was 1,550 ppm in a drainage area about 200 feet north of the fence; the nearest residence is over 1,000 feet from the fence. That level is considerably lower than many on-site levels and, since it was detected in a drainage area that received runoff from the site, it is unlikely that very much of the lead was wind-borne. Lead carried off site by the wind would therefore have been present only intermittently, and it is highly unlikely that it would have been present at levels of human health concern in any off-site areas. Lead dispersion to off-site areas at levels of health concern is no longer possible since soil lead has been lowered to safe levels.

Children playing in the soil off-site could have been exposed to lead. Since there are no homes immediately adjacent to the arroyos, it is unlikely that this is a frequent play area. Such exposures, if any, would therefore have been intermittent. Those off-site areas have also been cleaned up.

As stated above, no area residences use a private well for potable water. Groundwater quality in the CWM area is naturally poor, and there is no evidence that site-related substances contaminated off-site drinking water wells. No exposure through groundwater is therefore possible.

PUBLIC HEALTH IMPLICATIONS

In this section, ATSDR discusses health effects that may result from exposures to site contaminants. Chemicals released into the environment do not always result in human exposure, and exposure does not necessarily result in adverse health effects. People can only suffer the ill effects of exposure to a site contaminant if they breathe, eat, drink, or come in contact with that contaminant for a certain length of time. Based on available evidence, it is highly unlikely that anyone came into contact with contaminants at CWM long enough to suffer any adverse health effects. Since the site has been successfully remediated, there is no longer any danger of such exposures.

A. Toxicological Evaluation

There are no current completed pathways resulting from past activities at CWM. The soil on site has been cleaned up so that contaminant levels, if any remain, are not harmful to human health. All physical and chemical hazards have been removed and the buildings have been secured. Although nearby residents, trespassers on the site, and children playing in the arroyos just off site may have been exposed to site-related contaminants in the past, those exposures would have been intermittent and unlikely to cause any health problems. Although no adverse health effects are expected at CWM due to lead exposure, ATSDR's toxicological profile on lead may be consulted for information on lead toxicity.

B. Health Outcome Data

Health outcome data (HOD) document health effects that occur in populations. The data can provide information on the general health status of the community living near a hazardous waste site. They can also provide information on patterns of specified outcomes. The New Mexico Department of Health maintains a tumor registry and vital statistics data. Those databases are not available for small areas and therefore would not supply reliable information for the area near CWM.

COMMUNITY HEALTH CONCERNS EVALUATION

1. One primary health concern of the state public health officials was whether the superficial aquifer had been contaminated. Concern was also expressed about off-site residential wells. Citizens were concerned that although those wells are clean and they now use the Polvadera municipal water supply, there may have been groundwater contamination in the past to which they could have been exposed.

    The most recent information indicated that all residences in the area use the Polvadera municipal water supply. The shallow wells in the nearby vicinity are used for irrigation (2). Groundwater flows in a south- southwesterly direction. Monitoring wells located southwest of the contaminated soils do not indicate that groundwater contamination has occurred. According to groundwater testing conducted after the households had been switched to the Polvadera municipal water supply, the residential wells have not been contaminated by substances found at CWM. Also, the remediation plan enacted by EPA has stabilized contaminants so that they are no longer a concern.

    Iron and manganese were detected above drinking water standards in Phase II sampling, which took place after local residents had switched to the Polvadera water supply. Those standards, however, are for aesthetic purposes (i.e., taste and odor); no health effects would have been expected from drinking that water in the past. The high levels of iron and manganese, along with relatively high levels of total dissolved solids indicate that groundwater throughout the area is of generally poor quality; none of those substances can be linked to contamination from CWM.

2. Concerns were raised on several occasions about lead exposures in the children of the community. Concerns were raised about the lead oxide piles located on-site at CWM. Citizens are concerned that the seasonal prevalence of strong winds could distribute the lead off-site.

    Under the selected remediation plan, the contaminated soil was stabilized with cement, buried, and capped. Therefore, there are no longer any concerns about distribution of that soil off-site by strong winds.

    Strong winds could have carried contaminants off site in the past. Off- site soil sampling was conducted in several drainage areas north and south of the site. The maximum lead concentration detected was 1,550 ppm at a location approximately 200 feet north of the fenced area, most of which was due to drainage from the site (i.e., very little would have come from wind borne particles). Given that the nearest homes are approximately 800 feet north of that sampling location, it is unlikely that exposure to harmful lead levels could have occurred through the air pathway.

    The closest active source of lead emissions is a smelter located approximately four miles south of Lemitar. As part of the public health assessment process, we consulted the Toxic Release Inventory (TRI) database. According to TRI, that smelter had a total air release of 255 pounds of lead in 1993 (9). That amount of lead in a year is not expected to produce any adverse health effects. The lead would be so dispersed after traveling four miles that any exposures would be quite minimal.

3. Concerns were raised about the appropriateness of the proposed remediation plan for the type of contamination found at CWM.

    The remediation alternative chosen for CWM involved solidification with Portland cement and subsequent on-site burial of approximately 15,000 cubic yards of contaminated soil, sediment, and source waste materials. The excavation was then filled with clean soil, capped with concrete, and covered with another layer of clean soil and vegetation. Continued groundwater monitoring was also part of the remediation chosen. That alternative was one of six considered by EPA. The alternatives were thoroughly screened and were presented and discussed in public meetings prior to the actual selection of the most appropriate cleanup method. EPA determined that the method chosen was the most cost-effective way to provide maximum protection for both the environment and the health of area residents. We concur with EPA that the selected remediation is protective of public health.

4. What kind of monitoring will be performed in the future for off-site contamination once the remediation has been completed?

    Existing monitoring wells located downgradient to the disposal site will be monitored yearly. Selected site wells will also be monitored quarterly. The effectiveness of the remediation will be reevaluated every five years (1).

5. The 640 ppm soil lead level chosen as the target for remediation by EPA was questioned by the citizens of the community. They questioned the variation of lead cleanup levels chosen at different NPL sites.

    According to the UBK model, which is based on some quite conservative site-specific assumptions relating to the possibility of human exposure to contaminants, an average concentration of lead in soil of 640 ppm at the CWM site would not pose any health problems for residents who move there. The cleanup level for lead at some sites has been set at 500 ppm, but those sites typically have only limited data upon which to base a decision, so the most conservative level is used as a default. In fact, cleanup levels close to 1,000 ppm have been set at some sites for which sufficient data were available.


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