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Site Map
Figure 1. Site Map

Geological Survey
Figure 2. Geological Survey


Demographic Statistics
Figure 1. Demographic Statistics


Quality Assurance

In preparing this report, ATSDR relied on the information provided in the referenced documentsand contact with community members and representatives, North Carolina Department of Health,and Human Services and the North Carolina Department of Environment and Natural Resources.ATSDR assumes that adequate quality assurance measures were taken during chain-of-custody,laboratory procedures, and data reporting. The validity of the analyses and conclusions drawn inthis document are dependent upon the availability and reliability of the data.

Comparison Values

ATSDR comparison values are media-specific concentrations that are considered to be safe underdefault conditions of exposure. They are used as screening values in the preliminary identificationof site-specific "contaminants of concern". The latter term should not be misinterpreted as animplication of "hazard". As ATSDR uses the phrase, a "contaminant of concern" is a chemicalsubstance detected at the site in question and selected by the health assessor for further evaluationof potential health effects. Generally, a chemical is selected as a "contaminant of concern"because its maximum concentration in air, water, or soil at the site exceeds one of ATSDR'scomparison values.

However, it must be emphasized that comparison values are not thresholds of toxicity. Althoughconcentrations at, or below, the relevant comparison value may reasonably be considered safe, itdoes not automatically follow that any environmental concentration that exceeds a comparisonvalue would be expected to produce adverse health effects. The principle purpose behindprotective health-based standards and guidelines is to enable health professionals to recognize andresolve potential public health hazards before they become actual public health consequences. Forthat reason, ATSDR's comparison values are typically designed to be 1 to 3 orders of magnitude(or 10 to 1,000 times) lower than the corresponding no-effect levels (or lowest-effect levels) onwhich they are based. The probability that such effects will actually occur does not depends onenvironmental concentrations alone, but on a unique combination of site-specific conditions andindividual lifestyle and genetic factors that affect the route, magnitude, and duration of actualexposure.

Listed and described below are the various comparison values that ATSDR uses to select chemicals for further evaluation, as well as other non-ATSDR values that are sometimes used to put environmental concentrations into a meaningful frame of reference.

CREG = Cancer Risk Evaluation Guides
MRL = Minimal Risk Level
EMEG = Environmental Media Evaluation Guides
IEMEG = Intermediate Environmental Media Evaluation Guide
RMEG = Reference Dose Media Evaluation Guide
RfD = Reference Dose
RfC = Reference Dose Concentration
RBC = Risk-Based Concentration
MCL = Maximum Contaminant Level

Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations expected to cause no more than one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors, or cancer potency factors, using default values for exposure rates. However, neither CREGs nor cancer slope factors can be used to make realistic predictions of cancer risk. The true risk is always unknown and may be as low as zero.

Minimal Risk Levels (MRL) are estimates of daily human exposure to a chemical (dosesexpressed in mg/kg/day) that are unlikely to be associated with any appreciable risk of deleteriousnoncancer effects over a specified duration of exposure. MRLs are calculated using data fromhuman and animal studies and are reported for acute (< 14 days), intermediate (15-364 days), andchronic (> 365 days) exposures. MRLs are published in ATSDR Toxicological Profiles forspecific chemicals.

Environmental Media Evaluation Guides (EMEGs) are concentrations that are calculated fromATSDR minimal risk levels by factoring in default body weights and ingestion rates.

Intermediate Environmental Media Evaluation Guides (IEMEG) are calculated from ATSDRminimal risk levels; they factor in body weight and ingestion rates for intermediate exposures(those occurring for more than 14 days and less than 1 year).

Reference Dose Media Evaluation Guide (RMEG) is the concentration of a contaminant in air,water or soil that corresponds to EPA's RfD for that contaminant when default values for bodyweight and intake rates are taken into account.

Reference Dose (RfD) is an estimate of the daily exposure to a contaminant unlikely to causenoncarcinogenic adverse health effects. Like ATSDR's MRL, EPA's RfD is a dose expressed inmg/kg/day.

Reference Concentrations (RfC) is a concentration of a substance in air that EPA considersunlikely to cause noncancer adverse health effects over a lifetime of chronic exposure.

Risk-Based Concentrations (RBC) are media-specific concentrations derived by Region III ofthe Environmental Protection Agency from RfD's, RfC's, or EPA's cancer slope factors. Theyrepresent concentrations of a contaminant in tap water, ambient air, fish, or soil (industrial orresidential) that are considered unlikely to cause adverse health effects over a lifetime of chronicexposure. RBCs are based either on cancer ("c") or noncancer ("n") effects.

Maximum Contaminant Levels (MCLs) represent contaminant concentrations in drinking water that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day.
Methodology of Evaluating Chemicals of Concern

The Agency for Toxic Substances and Disease Registry (ATSDR) has determined levels ofchemicals that can reasonably (and conservatively) be regarded as harmless, based on thescientific data the agency has collected in its toxicological profiles. The resulting comparisonvalues and health guidelines, which include ample safety factors (also known as an uncertaintyfactor) to ensure protection of sensitive populations, are used to screen contaminantconcentrations at a site and to select substances (referred to as "chemicals of concern") thatwarrant closer scrutiny. A "chemical of concern" is defined by ATSDR as any chemical that isdetected in air, water, or soil at concentrations exceeding one or more of ATSDR's comparisonvalues. (Refer to Appendix C for a more complete description of ATSDR's comparison values,health guidelines, and other values ATSDR uses to screen site contaminants.)

It is important to understand that comparison values are not thresholds of toxicity. Althoughconcentrations at, or below, the relevant comparison value may reasonably be considered safe, itdoes not necessarily follow that any concentration that exceeds a comparison value would beexpected to produce adverse health effects. Indeed, the principle purpose behind protectivehealth-based standards and guidelines is to enable health professionals to recognize and resolvepotential public health problems before that potential is realized. For that reason, ATSDR'scomparison values are typically designed to be 1 to 3 orders of magnitude lower than thecorresponding no-effect levels (or lowest-effect levels) on which they are based.

When screening individual contaminants, ATSDR staff compare the highest single concentrationof a contaminant detected at the site with the lowest comparison value available for the mostsensitive of the potentially exposed individuals (usually children or pica children). Typically thecancer risk evaluation guide (CREG) or chronic environmental media evaluation guide (EMEG) isused. This "worst-case" approach introduces a high degree of conservatism into the analysis andoften results in the selection of many contaminants as "chemicals of concern" that will not, uponcloser scrutiny, be judged to pose any hazard to human health. In the interest of public health, it isprudent to use a screen that identifies many "harmless" contaminants, as opposed to one that mayoverlook even a single potential hazard to public health. The reader should keep in mind theconservativeness of this approach when interpreting ATSDR's analysis of the potential healthimplications of site-specific exposures.

As ATSDR's most conservative comparison value, the CREG, requires special mention. ATSDR's CREG is a media-specific contaminant concentration derived from the chronic(essentially, lifetime) dose of that substance which, according to an Environmental ProtectionAgency (EPA) estimate, corresponds to a 1-in-1,000,000 cancer risk level. Note, this does notmean that exposures equivalent to the CREG are expected to cause 1 excess cancer case in1,000,000 (1x10-6) persons exposed over a lifetime. Nor does it mean that every person in apopulation of one million has a 1-in-1,000,000 risk of developing cancer from the specifiedexposure. Although commonly interpreted in this way, EPA estimates of cancer "risk" areestimates of population risk only and cannot be applied meaningfully to any individual. EPAexplicitly stated in it's 1986 Cancer Risk Assessment Guidelines that "The true risks are unknownand may be as low as zero" (EPA, 1986).


EPA, 1986. Environmental Protection Agency. Guidelines for Carcinogenic Risk Assessment. Fed. Reg., 51: 33997-33998, September 24, 1986.

ATSDR Methodology

Methods of Evaluation of Potential Public Health Implications

Based on available scientific data, much of which ATSDR has collected in its toxicologicalprofiles, ATSDR has determined concentrations of hazardous substances that can reasonably (andconservatively) be regarded as harmless. The resulting comparison values generally include amplesafety factors to ensure protection of sensitive populations. They are used to screen contaminantconcentrations at a site, and to select "contaminants of concern" that warrant closer scrutiny byagency health assessors and toxicologists. A "contaminant of concern" is defined as a substancethat is detected in air, water, or soil at concentrations that exceed one or more of ATSDR'scomparison values and warrants further evaluation.

The derivation of a comparison value uses conservative exposure assumptions, resulting in valuesthat are much lower than exposure concentrations observed to cause adverse health effects. Thisensures that the comparison values are protective of public health in essentially all exposuresituations. Therefore, if the concentration of a substance in an exposure medium is less than thecomparison value, the exposure is not of health concern and no further analysis of the exposuremedium pathway is required.

Comparison values are conservative values, and it is important to note that concentrations ofsubstances that are higher than the comparison values will not necessarily lead to adverse healtheffects. Exposure to levels of substances above their comparison values may or may not lead toadverse health effects. ATSDR's comparison values do not indicate thresholds of toxicity, andthey are not used to predict the occurrence of adverse health effects.

A level of concentration that is equal to or below a relevant comparison value is considered safe.However, the fact that a concentration exceeds a comparison value does not mean that theconcentration is expected to produce adverse health effects. ATSDR uses highly conservative,health-based standards and guidelines to assist health professionals in recognizing and resolvingpotential public health problems.

Exposure Pathway Table
Pathway Name Contaminants Source Environmental Media Point of Exposure Route of Exposure Exposed Population Time Comments
Completed Pathways                
Past Air Emissions




Community ambient air




Past levels are uncertain due to lack of historical data.
Current Air Emissions




Community ambient air




Current levels are below health concern.
Surface Soil Contamination




Community soils




Current levels are below health concern.
Potential Pathway                
Sediment Contamination




Creek and river beds




Most levels below health concern. Unlikely that anyone would be able to ingest riverbed soils.


Year 2000 Air Monitoring Locations
Figure 1. Year 2000 Air Monitoring Locations

Table 1.

2000 Air monitoring results
Contaminant Levels in Air for Monitoring Sites in Carolina Solite Vicinity and Background and Population Monitors, 2000 (ng/m3)*
Site name Metal Average Concentration Median Concentration Range of Detection ATSDR Comparison Value (CV) Number of samples exceeding ATSDR CV EPA Risk Based Concentration (RBC) Number of samples exceeding EPA RBC
Frog Pond Site
Arsenic 2.8676 1.7695 0.0499-10.2291 CREG=0.2 ng/m3 24 of 25 samples RBC=0.45 ng/m3 23 of 25 samples
  Cadmium .8910 .3801 .1755-7.5258 CREG=0.6 ng/m3 4 of 24 samples RBC=1.1 ng/m3 3 of 24 samples
  Chromium .8218 .7976 .3375-1.5335 N/A   RBC=0.16 ng/m3 25 of 24 samples
Medlin Arsenic 1.0368 .8760 .1187-3.2393 CREG=0.2 ng/m3 36 of 38 samples RBC=0.45 ng/m3 33 of 38 samples
  Cadmium .9492 .4458 .0230-14.0156 CREG=0.6 ng/m3 13 of 38 samples RBC=1.1 ng/m3 5 of 38 samples
  Chromium 1.2683 1.0723 .002-5.0023 N/A   RBC=0.16 ng/m3 36 of 38 samples
Medlin Precision Arsenic .9232 .8984 .2695-3.2761 CREG=0.2 ng/m3 26 of 26 samples RBC=0.45 ng/m3 22 of 26 samples
  Cadmium .7238 .4534 .2061-5.0845 CREG=0.6 ng/m3 8 of 26 samples RBC=1.1 ng/m3 2 of 26 samples
  Chromium 1.2921 1.1404 .0734-5.7365 N/A   RBC=0.16 ng/m3 25 of 26 samples
Intersection Arsenic 1.4023 1.0344 .1286-10.7236 CREG=0.2 ng/m3 38 of 39 samples RBC=0.45 ng/m3 37 of 39 samples
  Cadmium .9444 .5858 .1088-12.8130 CREG=0.6 ng/m3 19 of 39 samples RBC=1.1 ng/m3 6 of 39 samples
  Chromium 1.4760 1.4253 .002-3.0853 N/A   RBC=0.16 ng/m3 37 of 39 samples
Hill Site Arsenic 1.1513 1.0015 .0367-3.6695 CREG=0.2 ng/m3 38 of 38 samples RBC=0.45 ng/m3 34 of 38 samples
  Cadmium .5076 .4579 .1910-1.3088 CREG=0.6 ng/m3 9 of 38 samples RBC=1.1 ng/m3 0 of 38 samples
  Chromium 1.1933 1.1941 .1807-3.0644 N/A   RBC=0.16 ng/m3 38 of 38 samples
Hill Precision Arsenic 1.7227 1.4703 .5043-4.0166 CREG=0.2 ng/m3 11 of 11 samples RBC=0.45 ng/m3 11 of 11 samples
  Cadmium .3894 .3664 .1657-.6922 CREG=0.6 ng/m3 1 of 11 samples RBC=1.1 ng/m3 0 of 11 samples
  Chromium 1.0375 .9098 .4291-2.1680 N/A   RBC=0.16 ng/m3 11 of 11 samples
Chapel Road (population exposure site) Arsenic 1.4582 1.1742 .2997-3.9407 CREG=0.2 ng/m3 6 of 6 samples RBC=0.45 ng/m3 5 of 6 samples
  Cadmium .6101 .4494 .3506-1.3624 CREG=0.6 ng/m3 2 of 7 samples RBC=1.1 ng/m3 1 of 7 samples
  Chromium .8010 .6071 .4626-1.8364 N/A   RBC=0.16 ng/m3 6 of 6 samples
* ng/m3= nanograms per cubic meter

Table 2.

Comparison of concentrations of metals in air, Carolina Solite facility vicinity 1999-2000
Comparison of Concentrations of Average and Median Metals Concentrations in Ambient Air, 1999-2000 (ng/m3)*
Metal 2000 Average Concentration Range 1999 Average Concentration Range 2000 Median Concentration Range 1999 Median Concentration Range
* ng/m3= nanograms per cubic meter

Contaminant Concentration Trends at Ambient Air Monitoring Stations, Median1 Ambient Air Concentrations of Contaminants of Concern 1999-20002

Table 3.

Two year comparison of ambient air concentrations of arsenic, cadmium, and chromium in Solite vicinity air monitors
Metal Frog Pond Site 2000 (Background) Medlin Site 1999 Medlin Site 2000 Medlin Precision Site 1999 Medlin Precision Site 2000 Intersection Site 1999 Intersection Site 2000 Hill Site 1999 Hill Site
Arsenic 1.7695 0.8948 0.8760 0.8948 0.8984 1.3810 1.0344 1.1532 1.0015
Cadmium 0.3801 0.4377 0.4458 0.4377 0.4534 0.5853 0.5858 0.4202 0.4579
Chromium 0.7976 0.8257 1.0723 0.8257 1.1404 0.9971 1.4253 0.6686 1.1941
1 Median values were compared because they are not as influenced as a yearly average by rare occurrences of very high or very low concentrations
2 Year with higher average is highlighted

Table 4.

Particulate dust concentrations (TSP), NC DENR 20001
Date Frog Pond
Medlin Medlin (precision) Intersection Hill Hill (precisions) Chapel Road (pop exp)3
01-Jan-00   55 55 54 42    
07-Jan-00   24 23 28 36    
13-Jan-00   23 23 28 39    
19-Jan-00   27 28 36 23    
25-Jan-00   SNOW SNOW SNOW SNOW    
31-Jan-00   SNOW SNOW 20 28    
06-Feb-00   26 24 34 22    
12-Feb-00   26 24 26 27    
18-Feb-00   22 22 27 24    
24-Feb-00   30 30 48 40    
01-Mar-00   46 48 61 127    
07-Mar-00   48 48 49 62    
13-Mar-00   23 22 22 59    
19-Mar-00   26 26 23 25    
25-Mar-00 STARTUP 55 56 72 76    
31-Mar-00 47 55 55 51 54    
06-Apr-00 39 41 42 61 80    
12-Apr-00 52 67 72 68 71    
18-Apr-00 16 29 25 21 21    
24-Apr-00 36 54 55 41 44    
30-Apr-00 VOID 38 43 42 48    
06-May-00 31 39 40 58 52    
12-May-00 61 51 53 65 70    
18-May-00 44 38 47 72 84    
24-May-00 28 30 32 31 41    
30-May-00 20 23 23 23 25    
05-Jun-00 34 32 32 42 38    
11-Jun-00 32 37 36 106 43    
17-Jun-00 29 24 22 48 41   STARTUP
23-Jun-00 32 29 VOID 37 47 STARTUP 40
29-Jun-00 23 22 CLOSED 28 27 27 40
05-Jul-00 VOID 45   52 51 50 25
11-Jul-00 46 51   55 59 58 26
17-Jul-00 VOID 29   27 40 35 65
23-Jul-00 27 30   31 26 26 41
29-Jul-00 29 29   38 37 34 31
04-Aug-00 22 23   27 35 32 20
10-Aug-00 26 25   32 28 28 29
16-Aug-00 51 54   68 VOID 90 41
22-Aug-00 39 46   41 49 48 23
28-Aug-00 24 26   30 35 36 VOID
03-Sep-00 17 18   18 19 18 49
09-Sep-00 21 32   30 43 43 29
15-Sep-00 35 38   48 38 39 41
21-Sep-00 15 16   30 32 30 23
27-Sep-00 13 20   20 18 15 VOID
03-Oct-00 34 40   72 51 52 49
09-Oct-00 17 20   22 26 25 24
15-Oct-00 35 37   38 40 41 37
21-Oct-00 47 54   75 78 79 59
27-Oct-00 48 46   50 63 VOID 49
02-Nov-00 59 68   113 102 101 72
08-Nov-00 48 64   75 62 57 55
14-Nov-00 22 23   27 26 21 22
geometric mean 30.7 33.6 34.8 39.8 41.3 38.1 35.0
Source: Reproduced from NC DENR "Stanley County Total Suspended Particulates Hazardous Air Pollutant Results Study", January 2001

TSP= Total Suspended Particulate

1 All data are reported in µg/m3= micrograms per cubic meter of air
2 Frog Pond was designated the "background site", or the site which was not thought to be impacted by facility emissions.
3 Chapel was designated as the "population exposure site", or the site which was thought to represent exposures of area residents to maximum facility emissions.
Highlighted levels exceed Air quality guidelines

North Carolina State Standard (and previous EPA Standard):
24 hour concentrations: < 150 µg/m3
Annual Geometric mean: < 75 µg/m3

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