PETITIONED PUBLIC HEALTH ASSESSMENT
CAROLINA SOLITE CORPORATION
(a/k/a CAROLINA SOLITE CORPORATION/AQUADALE)
AQUADALE, NORWOOD COUNTY, NORTH CAROLINA
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.
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.
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.
|Pathway Name||Contaminants||Source||Environmental Media||Point of Exposure||Route of Exposure||Exposed Population||Time||Comments|
|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|| |
|Current levels are below health concern.|
|Sediment Contamination|| |
Creek and river beds
|Most levels below health concern. Unlikely that anyone would be able to ingest riverbed soils.|
|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|
|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|
|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 |
2 Year with higher average is highlighted
|Date||Frog Pond |
|Medlin||Medlin (precision)||Intersection||Hill||Hill (precisions)||Chapel Road (pop exp)3|
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