HEALTH CONSULTATION
EVALUATION OF THE USE OF COAL MINE TAILINGS FOR ROADBED CONSTRUCTION AND FILL DIRT
HARTFORD, SEBASTIAN COUNTY, ARKANSAS
BACKGROUND AND STATEMENT OF ISSUES
Hartford, Sebastian County, Arkansas, is located approximately 25 miles south of Fort Smith, Arkansas. According to the 1990 census, Hartford had a population of 762. There is an abandoned coal mine located within the Hartford city limits that is bordered by East Second Street, Olive Street and Broadway Street. A records search resulted in the discovery of limited historical records for the coal mine. Exact dates of mine operations are unknown but the mine has been abandoned since about 1942. On August 18, 1999, the Arkansas Department of Environmental Quality (ADEQ) requested that the Arkansas Department of Health (ADH) evaluate soil sample data to determine if the use of coal mine overburden and waste soils (commonly referred to as mine tailings) for roadbed material and as fill dirt posed a public health hazard.
A resident of Hartford had contacted ADEQ to inquire about the possible health implications that exposure to coal mine tailings could have on the residents of Hartford. ADH and representatives of ADEQ met with the complainant to ascertain the nature and extent of the complainant's health concerns. Concerns focused on the physical and chemical dangers of "gob" piles (mine overburden or tailings), the potential for adverse health effects associated with run-off from the site to surrounding yards, and the potential for adverse health effects associated with the use of coal mine tailings in roadbed construction and as fill dirt.
On September 29, 1999, ADH conducted a site visit. The site was fenced except for one open area along the back side of the property and was covered with mixed vegetation. Mine tailings were scattered throughout the property. One large mine waste pile, approximately 30 feet high and 100 feet long, was located near the center of the property. Approximately 10 residences surrounded the property. Based on the visual inspection of the site, there did not appear to be any abnormal physical dangers on the site. ADEQ reports that there have been no significant changes in the site conditions since the ADH site visit.
The purpose of this health consultation is to evaluate the coal mine tailings sample data and to determine if using the mine tailings for fill dirt or as roadbed material would create a public health hazard. The objective of the sampling was to determine concentrations of metals in and around the piles of overburden and waste soils since the complainant had specified waste metals in the tailings and acidic mine drainage caused by oxidation of the waste metals in the tailings as the contaminants of concern.
Sampling
On 2 June 1999, ADEQ officials collected four samples and analyzed the samples for metals. The media collected and the analysis performed were in response to a community member's formal complaint. Three of the samples were taken directly from the mine waste pile and one sample was taken from the soil adjacent to a waste pile. This limited number of samples and the limited analysis that was conducted on the samples does not allow for an accurate characterization of the site. Since three of the samples came directly from the mine tailings piles, concentrations would be anticipated to be greater than or equal to concentrations in the surrounding soils. To assess the potential health risks associated with contaminants at this site, we compared contaminant concentrations to health based screening values. Screening values are media specific contaminant concentrations. While exceeding a screening value does not necessarily mean that a contaminant represents a public health threat, it does suggest that the contaminant warrants further consideration. The public health significance of contaminants that exceed screening values may be assessed by reviewing and integrating relevant toxicological information with plausible exposure scenarios. Estimated exposures may be compared to reported "No Observable" and "Lowest Observable" Adverse Effects Levels (NOAELs and LOAELs) and to known effect levels in humans, when available. The results of the analysis and the risk based screening value for the substance are presented in the following table:
| Analyte | Sample 1 (soil) |
Sample 2 (tailings) |
Sample 3 (tailings) |
Sample 4 (tailings) |
Screening Value |
| Aluminum | 2477 | 8560 | 7410 | 9910 | 78000 ppm (EPA) |
| Arsenic | 10 | 20.5 | 21.8 | 19.2 | 20 ppm (ATSDR) |
| Barium | 61 | 65 | 55 | 69 | 4000 ppm (ATSDR) |
| Cadmium | <0.5 | <0.3 | <0.3 | <0.3 | 10 ppm (ATSDR) |
| Chromium | 13.4 | 21.6 | 19.6 | 19.9 | 210 ppm EPA |
| Copper | 20 | 35.5 | 17.8 | 27.5 | 2900 ppm EPA |
| Iron | 13615 | 31300 | 32900 | 26200 | 23000 ppm EPA |
| Magnesium | 586 | 647 | 498 | 715 | None |
| Manganese | 110 | 218 | 34 | 210 | 7,000 ppm (ATSDR) |
| Nickel | 11.3 | 23 | 9.7 | 22.9 | 1000 ppm (ATSDR) |
| Selenium | 7.8 | <5 | <5 | 7.7 | 300 ppm (ATSDR) |
| Lead | <3.1 | <2 | 13.7 | <2 | 400 ppm EPA |
| Zinc | 51.8 | 38.4 | 15.4 | 41.2 | 20,000 ppm (ATSDR) |
| A. All results are reported as parts per
million B. Bolded values indicate that concentration exceeded screening value |
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To determine if using the mine tailings for fill dirt or as roadbed material would create a public health hazard, ADH evaluated the likelihood that exposure to contaminants at the maximum concentrations detected would result in adverse health effects. When people are exposed to chemicals, the exposure does not always result in adverse health effects. The type and severity of health effects that may occur in an individual from contact with contaminants depend on the toxicologic properties of the contaminants; the amount of the contaminant to which the individual is exposed; how often and how long exposure is allowed to occur; the manner in which the contaminant enters or contacts the body (breathing, eating, drinking, or skin/eye contact); and the number of contaminants to which an individual is exposed (combinations of contaminants). Once exposure occurs, characteristics such as age, gender, nutritional status, genetics, life style, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes, and eliminates the contaminant. A unique combination of all these factors will determine the individual's physiologic response to a chemical contaminant and any adverse health effects the individual may suffer as a result of the chemical exposure.
To determine whether health effects are likely to result from exposure, ADH estimates pathway specific exposure amounts (or doses) of contaminants of concern as part of the toxicologic evaluation. Inhalation and dermal exposures were considered in the evaluation, but doses were not calculated for these routes. None of the samples contained contaminants that exceeded dermal exposure screening levels. No air samples were taken, but the exposure scenarios for inhalation exposure should be limited to occasional exposure to tailings piles and possible exposure to tailings used for fill dirt and roadbed materials. The contaminants detected in the samples are not volatile and the potential for inhalation exposure should be limited to exposure of suspended particulate. With the exception of lead, the risk of inhalation exposures to the detected metals is based on a fraction of total exposure to the contaminant [1]. Since the concentrations of the metals detected were so low, the potential for inhalation exposures that could be harmful is negligible.
Exposure doses were estimated for those analytes that exceeded the ATSDR soil comparison value and for those analytes that have no soil comparison value. The estimated doses for incidental soil ingestion are presented in the following table:
| Analyte | Concentration(mg/kg) | Estimated Soil Ingestion Dose |
| Arsenic | 21.8 | 0.0004 mg/kg/day |
| Iron | 32,900 | 6 mg/kg/day |
| Magnesium | 715 | 0.1 mg/kg/day |
| Lead | 13.7 | 0.003 mg/kg/day |
| Exposure dose = contaminant concentration x soil ingestion rate x Exposure factor (10 -6)/Body Weight | ||
The main issue addressed in this Health Consultation is whether exposure to the contaminants detected in the analysis of the coal mine tailings will adversely affect the health of the citizens in the surrounding community. Exposure points should be limited to direct exposure to the mine tailings by trespassers on the site, exposure to run-off points surrounding the site, and to potential locations where the tailings are used as fill dirt or roadbed material.
Toxicological Evaluation
Arsenic
Arsenic is an element that is widely distributed in the earth's crust. Background arsenic concentrations in soils in the United States range from about 1 to 40 parts per million (ppm) with a mean value of about 5 ppm. It is not unusual for soils in Arkansas to exceed United States background levels for arsenic. The highest sampled arsenic concentration for the site was 21.8 ppm which falls within national background ranges. Arsenic in soil may be transported by wind, by runoff, or by leaching into the subsurface soil. Because many arsenic compounds tend to partition to soil or sediment, leaching usually does not transport arsenic to any great depth but tends to concentrate and remain in upper soil layers indefinitely.
Analysis of the toxic effects of arsenic is complicated by the fact that arsenic can exist in several different valence states and as many different inorganic and organic compounds. Most cases of human toxicity from arsenic have been associated with exposure to inorganic arsenic [2]. Data provided in Table 1 was for total arsenic. For the purposes of this health consultation, the conservative approach of evaluating all arsenic concentrations as inorganic arsenic is utilized.
The minimal risk level (MRL) for arsenic is 0.0003 mg/kg/day for chronic oral exposure. An MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non-cancer health effects over a specified duration of exposure. The estimated soil ingestion exposure dose for the sample with the greatest concentration of arsenic is 0.0004 mg/kg/day. This soil ingestion exposure dose slightly exceeds the MRL for arsenic. The chronic MRL for arsenic of 0.0003 mg/kg/day was based on individuals exposed to high levels of arsenic in well water. Under these conditions, a clear dose-response relationship was observed for characteristic skin lesions. Daily intake of water from a drinking water source is generally a more severe oral exposure than incidental soil ingestion. The no observed adverse effect level (NOAEL) in this study was 0.0008 mg arsenic/kg/day. The NOAEL is the highest exposure level at which no harmful effects were seen in the organ systems of the individuals studied. The lowest observed adverse effect level (LOAEL) is the lowest dose used in a study that caused a harmful health effect. The LOAEL in this study was 0.014 mg arsenic/kg/day. At a dose of 0.014 mg arsenic/kg/day, hyper-pigmentation and keratosis of the skin were observed. This effect is considered a "less serious" effect. The calculated soil ingestion exposure dose of 0.0004 mg/kg/day is not expected to result in any non-cancer adverse health effects.
There are conflicting reports on the risk of increased cancer incidence in populations exposed to arsenic in their drinking water. There is evidence from several epidemiological studies and case reports that ingestion of inorganic arsenic increases the risk of developing skin cancer in certain populations. In most cases, the skin cancer only develops after prolonged exposure to high concentrations of arsenic in drinking water[3]. In contrast, several epidemiologic studies performed in the United States have not detected increased frequency of skin cancer in small populations consuming water with concentrations of arsenic ten times greater than the Environmental Protection Agency (EPA) maximum contaminant level of 0.05 ppm. These data suggest that even though exposure to arsenic in water is not uncommon in the United States, arsenic associated skin cancer is not a common problem in this country[1]. Since public water is available to potentially exposed populations, and public water is required to maintain concentrations below risk concentrations, the oral exposure to arsenic at the Hartford site should be limited to incidental ingestion of soil. An exposure scenario limiting arsenic exposures to soil ingestion at the concentrations detected should not increase the risk of cancer incidence to potentially exposed populations.
Iron
The EPA screening level for residential soil is 23,000 mg/kg[4]. The highest concentration of iron in site soil was 32,900 mg/kg. Adverse health effects associated with iron are generally restricted to prolonged inhalation exposure in occupational environments to highly concentrated iron oxides. Iron is an essential mineral. The recommended daily allowance is 10 mg for men and 18 mg for women. The calculated soil ingestion dose for iron was 6 mg/kg/day. This value falls below the recommended daily allowance. Iron is not expected to pose a public health hazard by the ingestion route of exposure.
Magnesium
Magnesium is an essential metal found in all human tissues. There are no health based exposure restrictions for magnesium in its elemental form. Most foods contain significant amounts of magnesium. Nuts, cereals, sea foods, and meats are particularly high. Magnesium is an essential mineral. The recommended daily magnesium allowance is 350 mg for men and 300 mg for women.[5] The calculated soil ingestion exposure dose for the site was 0.1 mg/kg/day. The presence of it in site soils is not expected to pose a public health hazard by the ingestion route of exposure.
Lead
Lead is a naturally occurring bluish-gray metal found in small amounts in the earth's crust. Sources of lead in dust and soil include lead that falls to the ground from the air, and weathering and chipping of lead-based paint from buildings and other structures. Mining wastes that have been used for sandlots, driveways, and roadbeds can also be sources of lead [6].
Foods such as fruits, vegetables, meats, grains, seafood, soft drinks, and wine may contain lead. Lead gets into food from water during cooking and into foods and beverages from dust that contains lead falling onto crops, from plants absorbing lead that is in the soil, and from dust that contains lead falling onto food during processing. The calculated soil ingestion exposure dose based on the highest concentration of lead found at the site was 0.003 mg/kg/day. There are currently no MRLs derived for lead. The LOAEL, in humans for acute and intermediate oral exposure is 0.02 mg/kg/day and 0.01 mg/kg/day, respectively. Ingestion of lead from site soils is not expected to pose a public health hazard.
Run-off from the site to surrounding yards.
Mining accelerates natural processes. The development of underground
workings, open pits, ore piles, mill tailings, spoil heaps, and the extractive
processing of ores enhance the likelihood of releasing chemical elements to
the surrounding area in large amounts and at increased rates. The site in question
has been inactive since approximately 1942. A common process that results in
dispersion of elements from a mineralized site is acid drainage, commonly referred
to as acid mine drainage (AMD). AMD is the formation and movement of highly
acidic water which is rich in heavy metals. This acidic water forms through
the chemical reaction of surface water (rainwater, snow melt, pond water) and
shallow subsurface water with rocks that contain sulfur-bearing minerals, resulting
in sulfuric acid. Heavy metals can be leached from rocks that come in contact
with the acid, a process that may be substantially enhanced by bacterial action.
The resulting fluids may be highly toxic and when mixed with groundwater, surface
water, and soil may have harmful effects on humans, animals, and plants.
Run-off from the site could impact the soil surrounding the site and groundwater beneath the site, but there are no visual indications that this is occurring and there were no samples collected to characterize the off site soil or groundwater. Based on the sample data from the tailings, potential contamination of soils by the detected metals is unlikely to occur at concentrations that would result in hazardous exposures. There is insufficient data to assess the impact of leaching from the tailings on the groundwater beneath the site. The metals detected in the samples have a wide range of soil to groundwater transfer potential, but the impact of the tailings on groundwater could not be assessed since no samples were available.
The use of coal mine tailings from the mine waste pile in roadbed construction
and as fill dirt.
The analysis of the June 1999 samples indicate that the mine tailings
contain metals, but the concentrations of the contaminants are below health
risk concentrations. An accurate assessment of the potential risks is restricted
by the limited number of samples taken. If the samples accurately characterize
all of the tailings piles and the surrounding soil, use of the tailings as roadbed
materials and fill dirt will not create a public health hazard.
Child Health Initiative
ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of soil, water, air and food. Children are at a greater risk than adults from certain kinds of exposures to hazardous substances. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. They are more likely to come into contact with dust, soil, and heavy vapors close to the ground. Also, they receive higher doses of chemical exposure due to lower body weights. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Exposure doses for children were calculated to determine if exposures could result in adverse health effects. Any potential for child exposures to lead should be restricted. Even though the sampling indicates that the potential for exposure to lead is probably minimal, additional sampling will be needed to substantiate that assumption.
Additional sampling is recommended to characterize the site. Off-site soil, sediment, and ground water samples are needed to confirm that the mine tailings have not contaminated exposure points in the community.
Past Activities
This is an initial consultation. No previous activities have occurred on
the site or in the community.
Ongoing Activities
ADH is preparing a needs assessment to determine if there are health education
or community involvement needs.
Future Action Plans
ADH will conduct educational outreach based on the findings of the needs
assessment.
This Health Consultation for the Use of Coal Mine Tailings in Hartford, Arkansas was prepared by the Arkansas Department of Health under a cooperative agreement with the federal Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.
Roberta Erlwein
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation (DHAC), ATSDR, has reviewed this health consultation and concurs with its findings.
Richard E. Gillig
Section Chief, SPS, SSAB, DHAC, ATSDR
PREPARER OF HEALTH CONSULTATION
Health Assessor:
Michael Watts
Arkansas Department of Health
ATSDR Regional Representative:
George Pettigrew
ATSDR Region VI
ATSDR Technical Project Officer:
Tammie McRae
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry
