PUBLIC HEALTH ASSESSMENT
Elizabeth Copper Mine
(a/k/a Elizabeth Mine)
Strafford, Orange County, Vermont
CERCLIS NO. VTD988366621
August 23, 2004
ATSDR gathered community members' health concerns from petition letters in 2000 and identified a number of community concerns regarding the possibility of public health effects for people living near or on the Elizabeth Mine site resulting from environmental contamination. Community members first petitioned ATSDR to conduct a public health assessment in June 2000. The main community health concern was that the drinking water (particularly from wells close to the Elizabeth Mine site), soil, and air could contribute to health problems that children or adults in the community exhibit, such as seizures, epilepsy, respiratory and digestive problems, skin irritation, and kidney problems. ATSDR evaluated the community concerns along with the available data and addresses these concerns in the Discussion section of this document.
The Public Health Assessment was released for public comment on June 2, 2004. The public comment period for this document ended on July 16, 2004. During this period, the community has an opportunity to send written comments or to call ATSDR to discuss issues that may not have been addressed in the document or to express additional concerns. ATSDR did not receive additional concerns during this period, we did however, receive positive comments about the document and about the issues addressed in the document. As such, the document is being finalized and is being released as a final public health assessment. ATSDR will continue to work with the EPA and other state and local agencies to evaluate additional data as they become available and will prepare other public health documents to provide information to the community and to the other federal, state, and local agencies about the public health evaluation of the documents ATSDR staff reviews.
The following sections contain evaluations of available environmental data for the site. ATSDR used established methodologies for determining how people may be exposed to site-related contaminants and for evaluating what health effects, if any, can be associated with exposures to the contaminant levels found in the different media. ATSDR reviewed the environmental data collected at the Elizabeth Mine site and selected contaminants that warranted further evaluation. ATSDR evaluated the adequacy of the sampling conducted, identified the maximum concentration and frequency of detection of the contaminants found in the various media, and compared the maximum detected concentrations with health-based screening values or comparison values (CVs).
The health-based CVs used in this document are concentrations of contaminants that the current public health literature suggest are "safe" or "harmless". CVs are conservative screening values with built-in safety factors to account for uncertainties and sensitive populations (i.e., children or the elderly). ATSDR typically uses CVs as follows: If a contaminant is never found at levels greater that its CV, ATSDR concludes that the levels of the corresponding contamination are "safe" or "harmless". If, however, a contaminant is found at levels greater than the CV, it is designated as a contaminant of concern and ATSDR examines potential exposure pathways in greater detail. Because CVs are based on extremely conservative assumptions, the presence of a contaminant at concentrations greater than the CV does not necessarily suggest that exposure to the contaminant will result in adverse health effects. Appendix E provides more information about CVs and ATSDR's evaluation methods. Appendix F defines some of the terms used in this public health assessment.
Identification of contaminants of concern narrows the focus of the PHA to those contaminants most important to public health. When a contaminant of concern in one medium is selected, that contaminant is also reported in all other media. In subsequent sections, ATSDR evaluates whether exposure to these contaminants has public health significance.
In this document, ATSDR identified exposure pathways, or the ways in which a contaminant may enter a person's body (ingestion, inhalation, or skin contact). If an exposure pathway was or is possible, contaminant levels were evaluated to determine whether adverse health effects could occur. Potential exposures from drinking water, surface water, sediments, and biota (fish) were evaluated and are summarized in Appendix B, Table 1. Appendix B, Tables 2 through 4 present contaminants in each medium selected for further evaluation, along with frequency of detection, the maximum detected level, and the sample location where the maximum detected level was found. Figures showing the sample locations for each of the sampled media are provided in Appendix A.
- Environmental Data and Public Health Implications
- Drinking Water
Based on data collected from nine private wells on Old Mine Road: No current or future public health hazards were found to be associated with drinking water from private wells. Sampling data from private wells identified slightly elevated concentrations of metals, but these concentrations are below levels known to cause harm. ATSDR identified past use of well #3 as posing a health hazard from prolonged daily consumption because of elevated concentrations of cadmium, copper, and aluminum. ATSDR recommended that well #3 not be used in the 2000 health consultation. The site resident moved elsewhere shortly before this recommendation. It is not known how long well #3 was used before the resident relocated. The available data indicate that past use of other private wells posed no public health hazards. Metals are not easily released to the air; therefore, no inhalation exposure to these contaminants is expected.
The hydrogeology at the site has not been fully characterized; therefore, additional investigations are needed to fully understand the hydrogeology at and around the Elizabeth Mine site. Groundwater is likely recharged from surface water infiltration, and infiltration through the tailings piles could serve as a source of groundwater contamination. Data collected from private wells and pedometer sampling indicate that groundwater flow follows the natural surface topography of the area, flowing to the north-northeast. Private wells are located cross- or down-gradient from sources of possible groundwater contamination (i.e., the on-site tailings piles) (Arthur D. Little 2001a).
Drinking Water Sources
Towns bordering Strafford and located near the mine (Thetford, Sharon and Norwich) have eight public community systems. These systems are not located within 4 miles of the Elizabeth Copper Mine site. No public water supplies are located in Strafford, Vermont. Strafford residents, therefore, receive their water from private, individual water supplies, such as dug or drilled wells and springs. Approximately 1,400 people use groundwater from wells or springs located within 4 miles of the site (VTANR 1991). Eight residential wells are located on the mine site or within 0.5 mile of the site. A ninth well (well #3A) is also within 0.5 mile, but there are no buildings or homes on that property. These nine wells are located along Old Mine Road, west of the site. See Appendix A, Figure 3 for the private wells located along Old Mine Road.
Evaluation of Drinking Water Data
In March 2000, VTDEC sampled drinking water at three homes (wells #4, #5 and #7), and analyzed the samples for VOCs, SVOCs, PCBs, and metals. The following metals were detected at or above their respective CVs: copper, manganese, and iron. No VOCs, SVOCs or PCBs were detected in these samples.
In April 2000, EPA collected and analyzed drinking water samples from wells #1 through #6. Each well was analyzed for metals. Analytical results revealed the presence of aluminum, cadmium, copper, iron, and manganese above their respective CVs. Drinking water from residential wells #1 and #4 was also analyzed for VOCs and SVOCs; however, no VOCs or SVOCs were detected.
In May 2000, EPA collected and analyzed additional drinking water samples from seven residential wells (wells #1, #4, #5 and #7 were previously tested; #3, #3A and #9 were previously untested). These samples were tested for metals. Drinking water from residential well #3 contained elevated levels (above CVs) of aluminum, cadmium, cobalt, copper, iron, and manganese. Drinking water from residential well #3A contained elevated levels of iron and manganese. Samples from residential wells #1 and #5 contained slightly elevated levels of manganese. Chromium was detected slightly above its CV in well #9. No other residential well samples collected at this time (wells #4 and #7) revealed contaminants at levels above CVs.
From late 2000 to 2001, EPA conducted further testing of residential wells (wells #1 to #8, including #3A), and found arsenic, copper, iron, lead, and manganese at concentrations that exceeded the CVs. The maximum detected concentrations found over the course of well sampling and the locations of these detections are provided in Appendix B, Table 2. As the EPA collects more data, ATSDR will continue to evaluate the data.
Public Health Implications
ATSDR evaluated possible health hazards from using groundwater as a drinking water source . The following discussion describes the possible health implications of exposure to each metal found in drinking water wells at concentrations exceeding CVs.
Aluminum (31,000 parts per billion (ppb)), cadmium (16 ppb), cobalt (440 ppb), copper (13,200 ppb), and manganese (1,600 ppb) were detected at their maximum concentrations in well #3. ATSDR assessed possible health effects from exposure to each of these contaminants, except cobalt in the 2000 health consultation. For this PHA, ATSDR re-evaluated these exposures and considered cobalt data and data collected in 2000 and 2001. ATSDR calculated conservative exposure doses using the maximum detected level and conservative assumptions about exposures. For example, ATSDR assumed that adults daily consumed 2 liters of water and children daily consumed 1 liter of water. On the basis of these scenarios, the maximum exposure doses to cobalt are approximately 10 to 50 times lower than a level at which no health effects were observed in human studies (ATSDR 2000c). Doses for chronic exposure to aluminum, cadmium, and copper posed a public health hazard from prolonged daily consumption of water from well #3 based on data available for the 2000 health consultation. Therefore, ATSDR recommended that nobody drink from residential well #3 on a regular basis. Following this recommendation, a notice of poor water quality was sent to the landowner by EPA. In 2000, the resident at the property served by well #3 experienced problems with septic system contamination. The land owner assisted the resident in finding alternative housing and also removed the mobile home from the property. The resident was relocated prior to ATSDR's recommendation to close well #3 (EPA 2003a). Well #3 no longer serves as a source of drinking water.
No other wells contained aluminum, cadmium, cobalt, or copper above their CVs. Manganese, however, was detected in other private wells above its CV. Manganese was detected as exceeding the CV (50 ppb) in eight drinking water samples in wells #1, #3, #4 and #5 (from a total of 61 samples collected from March to May 2000). The highest concentration of manganese detected was 919 ppb (well #4) in the wells that are still in use. ATSDR evaluated possible health effects from consumption of water from well #3 and concluded that exposure to manganese in this well (1,600 ppb) would not pose a public health hazard from prolonged daily consumption. ATSDR considered possible exposure scenarios and chemical toxicity information as part of this evaluation. Daily consumption of water with lower manganese concentrations, as found in active private wells, would not pose a public health hazard from prolonged daily consumption.
Iron (30,900 ppb) was detected at its maximum concentration in well #3A. Only this one sample exceeded the iron CV. The land owner removed the mobile home that had been on this property, and no buildings are located on this property. This well is no longer active. It is not known whether this well has been capped.
Arsenic was detected above its CV (0.02 ppb) twice out of a total of 64 drinking water samples. The maximum detected concentration (3.8 ppb) was found in well #4. Well #3 contained 0.21 ppb arsenic. The CV for arsenic was derived by applying conservative assumptions about the ability of arsenic to cause cancer and by considering results of an epidemiology study of people who developed cancers after continuous exposure to 170 to 800 ppb arsenic for over 45 years. Development of the CV assumed that exposure to any amount of arsenic will potentially result in cancer, whereas current research suggests that arsenic at low levels (as seen at the Elizabeth Mine site) is detoxified—that is, changed into a less harmful form. Regardless, ATSDR calculated conservative exposure doses using the maximum detected arsenic level and conservative assumptions about exposures. Exposure to arsenic was assumed to occur over a lifetime and with a daily consumption of 2 liters of water containing elevated arsenic levels. Daily consumption is not occurring at the Elizabeth Mine site because arsenic was found above its CV in only one of many samples collected from well #4. Estimated doses for cancer effects were 300 times lower than doses at which cancer effects were seen in the study used to develop the arsenic CV. The estimated exposure doses for non-cancer effects were slightly lower than those in an epidemiological study that found no adverse health effects. Doses for children were approximately 40 times lower and doses for adults were approximately 160 times lower than those in studies that found non-cancer health effects in humans (hyperkeratosis and hyperpigmentation) (ATSDR 1998). Therefore, consumption of water containing this level of arsenic poses no past, current, or future health hazard.
Chromium was detected in one sample at 31.9 ppb in well #9; this concentration slightly exceeds the CV (30 ppb). No other samples (out of 64 samples) had chromium levels above the CV. Chromium is a naturally occurring element found in rocks, animals, plants, soil, and volcanic gases. Chromium occurs in the environment in several forms: primarily as trivalent (III) chromium or hexavalent (VI) chromium. Trivalent chromium is less toxic than hexavalent chromium. Most chromium in the environment (e.g., soil, water) and the body is trivalent chromium, the less toxic form of chemical (ATSDR 2000c). Monitoring results for the Elizabeth Mine site report only total chromium, and do not report the speciation between trivalent and hexavalent chromium. To conduct a conservative evaluation, ATSDR assumed that all the chromium detected in drinking water was the more toxic hexavalent chromium. Even assuming daily exposure to the highest detected level of chromium, estimated doses would be more than 600 times lower for adults (over 175 times lower for children) than the lowest level at which mild symptoms, such as abdominal pain, diarrhea, and vomiting, have been observed in human studies (ATSDR 2000c). Consumption of water containing detected levels of chromium, therefore, poses no past, current, or future health hazard.
Lead (to a maximum of 32 ppb) was detected exceeding the CV (15 ppb) one time each in wells #4 and #4A. Well #4A was installed in 2001 as a replacement for well #4. Well #4 was sampled on eleven separate occasions between April 2000 and May 2001. On one occasion, lead (22 ppb) exceeded its CV. Well #4A was sampled on five separate occasions between April 2001 and December 2001. On one occasion, lead (32 ppb) exceeded its CV. Children are more susceptible to lead poisoning than adults. Lead poisoning is often evaluated in terms of its impacts to blood lead levels. The Centers for Disease Control and Prevention (CDC) uses a blood lead level of 10 micrograms per deciliter ( g/dL) as a level of concern for children. A number of studies have been conducted to correlate drinking water lead concentrations and blood lead levels. These studies have reported an increase of 0.04 to 0.25 g/dL in blood lead per ppb of lead in water consumed by children (ATSDR 1999b). Based on these studies, a child drinking water containing 32 ppb of lead might experience an increase in blood lead levels of 1 to 8 g/dL, or below levels of health concern. Furthermore, children would be exposed to lead at lower levels than the maximum detected concentration since lead was detected above its CV in only one of five samples collected from well #4A. Therefore, lead found in private wells is not expected to result in a past, current, or future health hazard.
- Surface Water and Sediment
Exposure to metals and organics in surface water and sediment are not expected to cause past, current or future public health problems for recreational users of on-site streams and downstream rivers. On-site streams may be used for recreation by trespassers. Downstream rivers are designated fisheries that are used for recreational activities, such as boating. Fifteen metals were detected above CVs in surface water. Arsenic, iron, and phenanthrene were detected in sediments at levels above CVs. Infrequent contact with these metals and organics in surface water and sediment during recreation is not expected to pose a public health concern. Surface water is not used as a source of drinking water; therefore, exposure to surface water contamination via drinking water also poses no public health hazard.
Copperas Brook originates beyond the southwestern boundary of Elizabeth Mine, by the base of TP3. This brook flows through the site into TP1, where it forms a small pond. The small pond is also fed by two unnamed streams. Surface water from the site also flows into Copperas Brook. Copperas Brook flows from the pond approximately 2,000 feet north of TP1 and discharges to the WBOR. The WBOR joins the East Branch of the Ompompanoosuc River 4.5 miles southeast of the site to form the Ompompanoosuc River. The river flows into the Union Village River Reservoir formed by the Union Village Flood Control Dam, shown in Appendix A, Figure 4. People swim and use the reservoir for recreational fishing. The Ompompanoosuc River flows into the Connecticut River 5 miles downstream of the dam (VTANR 1991). Copperas Brook discharges an estimated 726,000 pounds per year of metals from the mine to the WBOR. Approximately 80% of this is iron and the remainder consists of aluminum, copper, zinc, lead, and cadmium (Arthur D. Little 2000a).
Evaluation of Surface Water and Sediment Data
In 2000, EPA collected surface water and sediment samples at locations both upstream of, and downstream from, the Elizabeth Mine site, shown in Appendix A, Figure 6. Two sampling sites are located upstream of the site; five sites are located along Copperas Brook; six are located on-site along the mixing zone of the WBOR; three sites are located downstream of the site. One other site is located upstream of a major potential source of surface water contamination, the Air Vent. The Air Vent, located south of the Ompompanoosuc River, is a 1-foot diameter (approximately) iron pipe that connects underground mines at the site to the surface. Water from the underground mines flows continuously from this pipe. Visual evidence of iron oxide build-up in the river from this flow has been observed, indicating that the Air Vent is a source of metals in surface water (Arthur D. Little 2000a). The locations of the surface water sampling are shown in Appendix A, Figure 6. Metal levels found during spring runoff were generally comparable to, or lower than, levels during drier times of year (Arthur D. Little 2000a).
Upstream of the Elizabeth Mine site, EPA detected elevated levels of two metals, arsenic and thallium, and bis(2-ethylhexyl)phthalate, in surface water. Fifteen metals were detected above CVs in on-site samples collected from the Copperas Brook. Seven metals were detected above their CVs in samples collected on site from the mixing zone of Copperas Brook and the WBOR. Arsenic, iron and phenanthrene were detected in sediment samples. Appendix B, Tables 3 and 4 summarize surface water and sediment sampling results, respectively.
Public Health Implications
ATSDR considered possible exposure scenarios, calculated exposure doses, and reviewed the chemical-specific toxicology data to assess possible public health effects. On the basis of the available data, ATSDR concludes that no past, current, or future adverse public health effects are expected from infrequent recreational use of on- and off-site streams and rivers.
No CVs are available for surface water, so ATSDR compared the maximum detected levels of contaminants in surface water to the CVs for drinking water. Drinking water CVs are based on the assumption that a person drinks 2 liters of water per day over a lifetime. During swimming, however, exposure studies have found that people ingest only about 0.15 liters of water (EPA 1997). Accidental ingestion during boating or wading would be even lower. The cold climate in Vermont would limit swimming, boating, or wading activities on a daily basis year-round. Nonetheless, for each metal found in surface water above CVs, ATSDR calculated conservative exposure doses using the maximum detected level and conservative exposure assumptions. The resulting doses for incidental ingestion or skin contact with surface water contaminants during recreation activities, were many times lower than levels found to cause health effects in laboratory studies.
No CVs are available for sediment, so ATSDR compared the maximum detected levels of contaminants in sediment to the CVs for surface soil. Arsenic (5.79 parts per million [ppm]) exceeded its surface soil CV (0.5 ppm) in 12 of 19 sediment samples. Iron (137,000 ppm) exceeded its surface soil CV (23,000 ppm) in 7 of 22 sediment samples. Phenanthrene (0.075 ppm) was detected in one sediment sample near the intersection of Copperas Brook and the WBOR, but does not have an established CV. Surface soil CVs are based on the assumption that a person accidentally ingests 200 milligrams (mg) of soil each day for prolonged periods of time (i.e., years). Contact with sediment in on- and off-site streams and rivers would be limited by the cold climate in Vermont. Recreational users are also expected to ingest smaller quantities of sediment during occasional recreational use (boating or swimming) in these streams. Because exposure is expected to be infrequent, ATSDR concluded that no adverse health effects are expected from limited exposure to these contaminants found in sediments.
- Biota (Fish)
Consumption of fish caught downstream of the Elizabeth Mine site is not expected to pose a public health hazard. Fish sampling found mercury and thallium above CVs in fish tissue. Lead was detected, but it has no CV. On the basis of a review of potential site-specific doses and the toxicology literature, ATSDR concluded that consumption of fish containing detected levels of lead, mercury, and thallium would not result in adverse health effects.
The WBOR and the Connecticut River are considered potential fisheries by the state of Vermont. Copperas Brook, located on the Elizabeth Mine site, is not considered a fishery.
Evaluation of Biota Data
In September and October 2001, EPA collected fish samples from twelve locations in Copperas Brook, Lords Brook, and WBOR (four upstream of the site and eight downstream of the site) to assess the possible impacts to fish from the Elizabeth Mine site. Samples of game fish (brook trout, brown trout, small mouth bass, and large mouth bass) and non-game fish (brown nose dace and long nose dace) were collected and their tissues were analyzed for metals. Lead which has no CV, was found in downstream samples from game fish in 11 of 21 samples at a maximum concentration of 0.54 ppm. Mercury (to a maximum of 0.71 ppm) and thallium (to a maximum of 0.55 ppm) were also detected above their CVs, 0.14 ppm for methylmercury and 0.095 ppm for thallium. Mercury was detected above its CV in 6 of 21 samples, and thallium was detected above its CV in 1 of 21 samples (EPA 2003b).
Public Health Implications
VTDOH has issued general fish consumption advisories for Vermont based on state-wide concerns about mercury. No specific advisories are in place for the water bodies downstream of the Elizabeth Mine site. The general advisories recommend that women of childbearing age and children under 6 years eat no more than one meal a month of smallmouth bass, two meals a month of largemouth bass, and three to four meals a month of brook trout or brown trout. For the general population, no more than three meals a month of smallmouth bass, and six meals a month of largemouth bass are recommended. No advisories are in place for consumption of brook trout or brown trout by the general population (VTDOH 2003).
Lead (to a maximum of 0.54 ppm in a smallmouth bass sample) was detected in fish samples collected downstream of the Elizabeth Mine site. To assess possible public health concerns, ATSDR calculated an exposure dose by conservatively assuming consumption of fish containing the maximum detected lead concentration. ATSDR assumed consumption rates typical of recreational anglers (one 8-ounce fish meal consumed every 10 days), as identified by studies of recreational freshwater anglers (EPA 1997). The resulting dose is more than 2,900 times lower for adults (or 800 times lower for children) than the lowest dose reported in the toxicology literature as causing no adverse health effects in laboratory animals. Health effects data for lead exposures are often expressed as blood lead levels versus doses. Accordingly, CDC often uses blood lead levels to assess possible harm from lead exposures and has set 10 g/dL as the level of concern for blood lead levels in children. Scientific studies have been conducted to estimate possible increases in blood lead levels per ppm of lead ingested from fish. On the basis of the results of these studies, ATSDR estimated that daily consumption of fish containing the maximum detected lead levels would result in an estimated blood lead level 75 times lower than the 10 g/dL guideline (ATSDR 1999b).
Mercury was detected to a maximum of 0.71 ppm in a brook trout sample collected downstream of the Elizabeth Mine site. Mercury is found in several different forms in the environment; methylmercury is the predominant form (about 85%) found in fish tissue. Methylmercury is the more toxic form of mercury; therefore, ATSDR assumed that 100% of the mercury in fish was methylmercury. Applying this assumption and the exposure scenario outlined for lead, ATSDR estimated doses for adults and children exposed to the maximum concentration of mercury in fish tissue. The resulting doses were below the dose reported in a study of people who were exposed to methylmercury in their food and did not experience any adverse health effects (ATSDR 1999a).
Thallium was also found above its CV in fish tissue samples collected downstream of the Elizabeth Mine site (to a maximum of 0.55 ppm in a smallmouth bass sample). The estimated doses for consumption of fish containing the maximum detected thallium concentrations were 1000 times (adults) and nearly 300 times (children) lower than the dose reported in the toxicology literature as causing no adverse health effects in laboratory animals (ATSDR 1992).
On the basis of these evaluations and the fish consumption advisories in place, ATSDR expects no adverse health effects to result from consumption of fish caught downstream of the Elizabeth Mine site.
- Health Outcome Data Evaluation
Government agencies often collect health information from populations in different geographic areas; many state health departments have developed registries of illnesses and disease; some county and local health departments periodically collect health information; and community members and groups may also collect health information for particular areas of interest. These data can be evaluated to identify trends in populations and any unusual increases in disease in specific areas. VTDOH examined 1994-1996 incidence rates and mortality rates for Vermont counties for breast cancer, female colorectal cancer, male colorectal cancer, female lung cancer, male lung cancer, and prostate cancer, and concluded that Orange County, where the Elizabeth Mine site is located, did not exhibit statistically significant deviations from the U.S. averages for any of these categories (VTANR 2000).
Community members are concerned that the following health effects could be related to exposures to site-related contaminants: seizures, epilepsy, respiratory and digestive problems, skin irritation, and kidney problems. In the previous health consultations and this document, ATSDR identified no exposure scenarios that would be likely to result in these adverse health effects. Details of ATSDR's evaluations are provided in the Discussion section of this public health assessment and in the previous health consultations (summarized in Appendix C)
- Child Health Considerations
Children are at greater risk of health effects from exposures to hazardous substances than adults because they: (1) play outside more often than adults (increasing the likelihood of contact with chemicals in the environment); (2) are shorter than adults and more likely to be exposed to soil, dust, and heavy vapors close to the ground; (3) are smaller than adults and their exposures would result in higher doses of chemical per body weight; and (4) have developing body systems which can sustain damage if toxic exposures occur during certain growth stages. ATSDR evaluated how children might be affected by the types and quantities of the chemicals detected in site media (groundwater, surface soil, surface water and sediment, air, and biota), seeking to determine if detected contaminant levels might be associated with any reproductive or developmental effects.
When evaluating the potential exposures presented in the Discussion section of this public health assessment (e.g. exposure to contaminants in drinking water or in surface soil), ATSDR used the most conservative CVs for children while evaluating the data.
ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children require special emphasis in communities faced with environmental contamination. In evaluating potential exposures, ATSDR has taken into account that children live near the site and could be exposed to site-related contaminants. Drinking water samples obtained during April and May 2000 from residential well #3 contained increased levels of aluminum, cadmium, and copper that could pose a health threat following prolonged daily consumption. Therefore, ATSDR recommended closing this well. Prior to issuing this recommendation, the resident at the property served by well #3 experienced problems with septic system contamination. The land owner assisted the resident in finding alternate housing and also removed the mobile home from the property. Lead was also found in two samples collected from one home (residence 2) at an elevated level (430 and 1,600 ppm). ATSDR concluded in its 2001 health consultation evaluating soil, dust, and ambient air exposures that this result did not appear to be representative of overall lead levels in that home. Blood lead level monitoring in children living in this home, however, was recommended based on best available public health practices.
This section summarizes the exposure pathways associated with the Elizabeth Mine site. As part of the PHA process, one of ATSDR's first goals is to identify exposure pathways. Exposure pathways are studied to understand the different ways that contaminants move within and from a site and the different ways that people might come into contact with those contaminants. In short, the purpose of the exposure pathway evaluation is to determine (a) if anyone might come into contact with the environmental media under study; (b) when (how often, over what time period); (c) where; and (d) how. This information alone does not define exposure—it simply helps us to better understand the likelihood of exposures. The exposure pathway information is used together with the environmental data to support the health effects evaluation.
ATSDR obtained information to support the exposure pathway analysis for the Elizabeth mine site from multiple site investigation reports, previously released ATSDR documents, 2000 U.S. Census data, and through communications with other federal, local and state officials, and from community concerns provided.
To determine whether nearby residents are exposed to contaminants from the site. ATSDR evaluates the environmental and human components of exposure pathways. Exposure pathways consist of five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and a potentially exposed population.
An exposure pathway can be eliminated if at least one of the five elements is missing and will never be present. ATSDR categorizes exposure pathways that are not eliminated as either completed or potential. For completed pathways, all five elements exist and exposure to a contaminant has occurred, is occurring, or will occur. For potential pathways, at least one of the five elements is missing, but could exist. For potential pathways, exposure to a contaminant could have occurred, could be occurring, or could occur in the future. Appendix E presents more detailed information about exposure pathways. Table 1 in Appendix B summarizes exposure pathway information related to the Elizabeth Mine site.