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Petitioned Public Health Assessment

Carolina Solite Corporation
EPA ID#: 980557730
Aquadale, Norwood, North Carolina

September 12, 2001

• Summary
  
• Introduction
  
• Background
  
• Demographics
  
• Community Health Concerns
  
• Discussion
  
• Methods
  
• Extent of Contamination
  
• Air
  
• Ambient Air
  
• Particulates in Air
  
• Employee Air Sampling
  
• Drinking Water Wells
  
• ATSDR Child Health Initiative
  
• Health Outcome Data
  
• North Carolina Department of Health Cancer Investigation
  
• Biological Sampling
  
• Public Health Implications
  
• Contaminants of Concern
  
• Arsenic
  
• Cadmium
  
• Chromium
  
• Physical Hazards
  
• Conclusions
  
• Recommendations
  
• Public Health Action Plan
  
• Authors/Site Team
  
• References

Appendices

• Appendix A: Site and Facility Maps
  
• Appendix B: Demographics
  
• Appendix C:Explanation of Methodology and Pathways Table
  
• Appendix D:Air Sampling Results
  
• Appendix E: Residential Well Sampling Results
  
• Appendix F: Biological Sampling Results
  
• Appendix G: Community Health Concerns
  
• Appendix H: Cancer Risk Evaluation
  
• Appendix I: Public Comments
  
  

In August 1998, NC WARN (North Carolina Waste Awareness and Reduction Network) petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a public health assessment of the areas surrounding the Carolina Solite facility located in Aquadale, North Carolina. The petition was filed on behalf of area residents. Residents are concerned about adverse health effects they believe are the result of long term exposure to emissions from the Solite facility.

ATSDR reviewed all available environmental and health outcome data and concludes that the data do not suggest a current threat to human health. Data reviewed for this document indicate that environmental media may contain chemical contamination, but below levels that have been associated with adverse health effects. Biological data do not reflect exposures to contamination at levels of health concern.

Based on all available data, ATSDR has made the following observations:

• Air:  Current ambient air contamination and particulate matter concentrations in the community are not a public health hazard. Onsite emissions are not a public health hazard to Solite employees. ATSDR was unable to assess health implications of past exposure because no historical environmental sampling data exists.
  
  
• Groundwater:  Current tests indicate that groundwater in this community is safe for human consumption. Levels of metals and volatile organic compounds detected in groundwater are within acceptable ranges of drinking water quality guidelines. Metals, such as iron, detected in low concentrations are most likely naturally occurring in this geographic zone.
  
  
• Biological:   Biological data do not indicate exposure to high levels of contamination. Inorganic arsenic was not detected in residents tested for heavy metals. Other heavy metals detected were within the range of a healthy unexposed population.
  
  

On August 8, 1998, the North Carolina Waste Awareness and Reduction Network (NC WARN) petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a public health assessment on the impact of industrial emissions from the Carolina Solite facility on area residents [1]. ATSDR reviewed and evaluated available data from the North Carolina Department of Health and Human Services (NC DHHS) and the North Carolina Department of Environment and Natural Resources (NC DENR). ATSDR evaluated community concerns and available air, groundwater, and biological data to determine the potential and extent of the exposure of residents to environmental contamination. The purpose of this document is to identify potential human exposures and to recommend appropriate public health follow-up activities.

The Solite facility is located near Aquadale, North Carolina. Aquadale is approximately 45 miles east of Charlotte. The property surrounding the facility is rural farmland and residential. The most populated area is due east approximately five miles in the town of Aquadale. Maps of this area are located in Appendix A.

Solite began operating in Aquadale in 1953, producing lightweight aggregate for the construction industry. The facility is regulated as a boiler and industrial furnace (BIF) under state and federal hazardous waste laws and regulations. The facility produces lightweight aggregate by heating slate and shale mined in an onsite quarry in four large rotary kilns. As the shale and slate are heated, gases are released causing them to expand. The expanded product, referred to as Solite^®, is lightweight, fire resistant, weather resistant, and provides insulating properties [2]. It is used in construction for masonry rocks and concrete. The Solite facility primarily consists of a quarry from which shale and slate are extracted, an inactive quarry, a storage and handling area for the raw material, the rotary kiln process area, and product storage and handling areas [2]. The facility encompasses approximately 125 acres [3].

In the past, Carolina Solite has used a number of fuels to fire its kilns. In Spring of 2000, the facility agreed to use waste oil and coal exclusively in its heating process. From 1983 until 2000, the facility burned Hazardous Waste Derived Fuel (HWDF), waste oil, and coal to fire the furnaces. Carolina Solite received the HWDF via a pipeline and trucks from Giant Resource Recovery, a contiguous permitted liquid waste blending and storage facility [3].

Demographic information was collected in a five block group area surrounding the Solite facility. Current population estimates for this area are available for 1998 at the census block group level only [4]. Block groups contain between 250 and 550 housing units and are often used to distinguish area neighborhoods. This data was collected from census tract 9910 (4), 9910 (5), 9909 (4), 9909 (3) and 9907 (3). Appendix B, Table 1 provides data for these block groups as well as comparison data for Stanly County.

The block groups in this area are predominantly Caucasian; approximately 90% of the 5629 residents are Caucasian. African Americans account for 9.3% of the total population and about 1% are of another race. Less than 1% of residents are of Hispanic origin. Median age varies for these block groups (between 36.1-40.2), but average 38.4 years. This is slightly higher than the county, whose median age is 37.1. Figure 1 and Table 1 in Appendix B illustrate the age distribution in this community. The median number of school years completed is 12.3. Median household income in this area varies greatly, from $30,750 to $39,318, but averages $34,815. This is on average higher than the median household income of the county, which is $31,652. The area appears to be relatively stable in that the median length of residence is 15.5 years, in contrast to the county which has a median length of residence of 13.8 years [4].

There are 2251 housing units in these block groups, and the vast majority are occupied (92.2%). Most people own their homes; 85% of residents living in this area own their homes. Approximately half the homes in this area were built before 1970 (50.4%), and 20.5% were built before 1949. The median housing value in this area is almost equal to that of the county ($65,434 vs. $65,283) [4]. For additional demographic information, see Appendix B.

In the early 1990s, residents expressed their concerns to state authorities about potential environmental contamination and human exposure from site emissions. The concerns included the incidence of different types of cancers, Alzheimer's Disease, asthma, sinus conditions, and neurological illnesses. Specific cancers of concern were: leukemia and brain, kidney, colon, lung, and skin cancers. The North Carolina Department of Health and Human Services (NCDHHS) and the North Carolina Department of Environment and Natural Resources (NC DENR) have investigated contamination, exposure, and compliance issues at the facility and surrounding areas. Sampling has consistently detected metals in ambient air near the facility. Groundwater monitoring in 1991 found elevated metals in monitoring and supply well, surface water, and sediment samples collected near or on Solite property. Of particular concern to state agencies and residents is the level of arsenic that has been detected in residential air. Currently, the United States Environmental Protection Agency (EPA) is analyzing soil and sediment data collected during the Spring of 2000. A discussion of these health concerns can be found in Appendix G.

In preparing evaluations of environmental data, ATSDR uses established methodologies for determining how people may be exposed to potential contamination from surrounding industry, and what effects, if any, may result from exposure to those contaminants. The ways that people may come into contact with chemical contaminants, called 'exposure pathways', are also evaluated. The exposure pathways that ATSDR evaluates include ingestion (eating), inhalation (breathing), and skin contact.

If one or more of the exposure pathways are established, ATSDR then considers whether chemicals have been or still are present at levels that may be harmful to people. ATSDR first does this by screening the concentration of contaminants detected in air, water, or soil against their health-based comparison values. Comparison values (CVs) are often based on animal studies because relevant human data are lacking. CVs are therefore derived using very conservative assumptions and often have large safety factors built into them to be protective of human health. Some CVs may be hundreds or thousands of times lower than exposure levels shown to produce effects in laboratory animals or humans. Thus, ATSDR's CVs are designed to be orders of magnitude lower than levels known to produce adverse health effects. Although chemicals detected at or below CVs are considered safe, any concentration that exceeds a CV would not necessarily be expected to produce adverse health effects. Chemicals detected above CVs require a more detailed evaluation of site-specific exposure conditions. ATSDR emphasizes that regardless of the contamination level, a public health hazard exists only if people come in contact with, or are otherwise exposed to, harmful levels of contaminated air, soil, or water.

If ATSDR has not established a CV for a chemical, then one developed by a different agency is used. If no CV of any kind is available for a chemical, then that chemical is further evaluated. For all site-related contaminants that are detected at levels above CVs, ATSDR reviews relevant scientific literature to determine if site-specific exposures could pose a hazard to public health.

For a complete discussion of these criteria (quality assurance considerations, human exposure pathway analyses, ATSDR's health comparison values, and the methods of selecting contaminants above comparison values), please refer to Appendix C.

This health assessment will review air monitoring data, residential well data, and health outcome data provided by NC DHHS and NC DENR from the Carolina Solite Corporation.

NC DHHS and NC DENR provided ATSDR with residential well data on separate properties sampled in 1991 and 1999, air monitoring data on four sampling sites that were collected throughout 1999, personal monitoring data of employees of the Carolina Solite facility, cancer statistics, and urine sample data for 30 residents living in the area collected during 2000. This analysis is based on the site-specific data provided to ATSDR for review, which are limited in scope by the time period of the data collection and by the assumption that proper quality assurance/quality control standards were followed in analyzing laboratory results. The results of soil and sediment sampling collected by the EPA will be evaluated in a future public health consultation. Through air monitoring, arsenic has been identified by NC DHHS and ATSDR as a contaminant of concern at this site.

ATSDR has identified ways in which area residents may have come in contact with site-related contamination:

1. Previous or current inhalation of contaminated ambient air.
   
   
2. Skin contact with, inhalation and ingestion of contaminated surface soils.
   
   
3. Skin contact with, inhalation and ingestion of contaminated groundwater.
   
   

ATSDR evaluated human exposure to determine whether nearby residents are exposed to contamination migrating from the site. An exposure pathway contains the following five elements: a source of contamination, transport through some kind of environmental medium (air, soil, or water), a point of exposure (a water well, or emissions stack), a route of exposure (breathing, eating, drinking), and an exposed population. In this assessment, ATSDR evaluated chemicals in the air and groundwater that people living in the nearby residences may consume or contact in some manner.

Four ambient air monitoring sites were located and operated in near the Solite property in 1999 by NC DENR, Division of Air Quality. Two additional monitoring sites were located in the area in 2000. However, only 1999 data is analyzed in this health assessment. Four of the six monitors that have been located in the area were operated until the middle or end of 2000. One of these includes a regional background site that is not expected to be impacted by facility emissions. The initial sites and one of the locations added in 2000 were placed in locations believed to be maximum impact areas. These areas were determined by NC DENR using emissions modeling techniques.

The total suspended particulate (TSP) samples collected in 1999 were analyzed for heavy metals and particulate matter. The heavy metals sampled included beryllium, chromium, manganese, cobalt, nickel, arsenic, selenium, cadmium, antimony, and lead. Of these contaminants, arsenic, cadmium, and chromium exceeded ATSDR health-based guidelines (CVs). Chromium and arsenic concentrations exceeded CVs in 168 of the 169 samples collected. Cadmium was also frequently detected; it exceeded CVs in 51 out of 169 samples collected. The results of the 1999 data, as well as a map of sampling locations can be found in Appendix D.

Arsenic and cadmium sources in ambient air have not been specifically identified. Although the facility is possibly contributing to the contamination, farming practices may also increase levels of arsenic and cadmium. The area surrounding this facility is rural and agricultural crops are common, especially cotton. Arsenic is a common ingredient in agricultural chemicals such as insecticides, herbicides, algaecides, and growth stimulants for plants and animals [5]. In 1999, Stanly County harvested 11,500 acres of cotton [6]. Monosodiummethylarsenate (MSMA) is used extensively on cotton fields to control weeds. MSMA is 46% arsenic by weight. Also, disodiummethylarsenate (DSMA) is a common herbicide used in cotton farming, but is usually applied at a higher concentrations than MSMA. State officials report that the manufacturer recommended application of MSMA is 2.1 pounds applied per acre of cotton fields, 46% of which is arsenic [7].

Upon investigation, ATSDR determined that during 1999 the highest concentrations for arsenic could not be clearly associated with harvest and summer planting months when soils are disturbed. In Stanly County, the three largest crops are soybeans, cotton, and corn. These crops are usually planted between April and June, and harvested in late September or later. For example, the bulk of cotton crops are planted by the 10^th of May. The cotton crops receive applications of MSMA and DSMA in late May when the crop is in a "two leaf" stage and plants are very young, and again in late June prior to first bloom [8]. The peaks observed in arsenic levels in 1999 were not observed during the periods of MSMA and DSMA application, but later in July and through August. The cotton planting month of May and harvesting month of October were not found to have notably high peaks to associate with arsenic levels sampled in air monitors.

Cadmium carbonate and cadmium chloride have been used as fungicides on lawns [9]. Chromium is not a common ingredient in agricultural products. Because there are many potential sources of chromium in air, sources besides the Solite facility have not been identified.

Air monitoring technology presently has the capability of monitoring air particles in a range of sizes, measured in micrometers. PM10 refers to particulates that are 10 micrometers in diameter or less, and PM2.5 refers to dust particulates that are 2.5 micrometers in diameter or less. Total suspended particulates (TSP) refers to a particulate concentration of all sizes. The total suspended particulate procedure captures measurable particulates as small as 0.1 micrometers (40 CFR50- Appendix B). EPA has established regulatory guidelines of particulate concentrations that are safe to breathe in ambient air. EPA had specific regulations for TSP of 150 g/m³ (micrograms per cubic meter) for 24-hour averages and 75 g/m³ for annual averages, but decided that more specific guidelines for the size of the particle was necessary. These guidelines are given for both average 24-hour concentrations and for average annual concentrations. In addition, samples were collected for particulate matter equal to and less than 10 micrometers in diameter (PM10). The particulate sampling technique for collected PM10 is also published in the Federal Register (40 CFR50-Appendix J). Currently, EPA has established acceptable 24-hour average concentration averages for PM10 of 150 g/m³ and 50 g/m³ for PM10 annual averages. Acceptable PM2.5 regulations are currently being negotiated by EPA.

In the community around the Solite site, particulate matter was sampled continuously for nine months at two locations, and 24-hour averages were taken every day during that time. TSP levels were recorded for the entire nine month period (January through mid-September) at two sampling sites, and PM10 was collected from mid-May through December 1999 at two sites.

All of the daily TSP and PM10 results were below the previous EPA recommended levels of 150 g/m³ (24-hour average) for three of the four 1999 monitoring locations. One TSP monitoring site was closed down by NC DENR, Division of Air Quality, when it was determined that the sampler was impacted by dust originating from a nearby dirt road. It exceeded EPA recommended levels for 5 days during the monitoring period, most likely because of its susceptibility to dust from passing traffic. The nine month averages of the monitors were within acceptable annual ranges of 75g/m³ for total suspended particulates and 50g/m³ for PM10 [10]. See Appendix D, Table 2 for particulate sampling data.

In July 2000, NC DHHS conducted an industrial hygiene survey at Carolina Solite Corporation to evaluate employee exposure scenarios and contaminant exposure levels. Exposures were measured in each department of plant operation. However, contractors employed for drilling and blasting operations were not tested. In all, 12 employees were tested for contaminant respiration in their working areas [11].

The samples were collected and analyzed for metals using appropriate equipment and testing methods designated by the Occupational Safety and Health Administration (OSHA). A sample of bulk dust was collected from a drill hole in the quarry and a bulk sample of expanded raw material ('clinker') was also analyzed. Data from this investigation is provided in Appendix D, Table 3. Only chromium was detected in the airspace of a single employee. Further discussion is provided in the contaminants of concern section of this document.

Historical permit violations have resulted in spot sampling of different areas of the Solite property. In the early 1990s, elevations of organics, such as acetone, methyl ethyl ketone, napthalene, benzene and benzene derivatives, furans, and phenanthrene were detected in creeks, ponds, and wastewater system leaks where they were illegally being discharged. Metals were also detected in these sampling efforts. They included zinc, aluminum, iron, lithium, arsenic, manganese, magnesium, cadmium, copper, chromium, and barium. Concerns about leaching of contamination into water sources prompted the investigation of potential residential water well contamination. Residential wells were sampled in 1991 and 1999. The 1991 sampling did not indicate chemical contamination of residential wells, but did indicate slight elevations of iron and manganese in several wells. The investigation concluded that the elevations of these metals were most likely naturally occurring and were not a threat to human health.

Thirteen residential drinking water wells were sampled by the North Carolina Department of Environment and Natural Resources, Division of Water Quality in October 1999. Wells were sampled for volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), and metals. Barium, copper, iron, lead, and manganese were detected, all at levels below ATSDR comparison values (CVs) and EPA risk based guidelines (RBCs). Iron was the most commonly detected in 10 of 13 wells. All metals detected were below National Primary Drinking Water Regulations for all metals except iron and manganese, neither of which have primary standard levels. Both of these metals slightly exceeded Secondary Drinking Water Regulations, which are non health-based guidelines. These are the same metals detected in 1991 in low concentrations, and are most likely naturally occurring in this geographic zone. Arsenic and cadmium as well as several other metals were below detection limits (BDL); however, the detection limit of the instrument was higher than some of the most conservative health based guidelines for arsenic and cadmium. Even if these two metals has been detected at concentrations equal to the detection limit of the instrument, they are not expected to result in adverse health conditions. Trace amounts of the toluene, styrene, 1,1-dichloroethane, and chloroform were detected at levels less than 0.5 parts per billion (ppb), all below applicable health based guidelines (Appendix E, Table 1). A map of sampling locations can also be found in Appendix E.

Children are at greater risk than adults for certain kinds of exposure to hazardous substances emitted from waste sites and emergency events. They have a greater risk of exposure for several reasons:

• The developing systems of children can sustain damage if toxic exposures occur during certain growth stages.
  
  
• Children play outside more than adults, and therefore have an increased likelihood of coming into contact with chemicals in the environment.
  
  
• Since they are typically shorter than adults, children breathe more dust, soil, and heavy vapors close to the ground.
  
  
• Children are also smaller, resulting in relatively higher doses of chemical exposure per body weight.
  
  

Therefore, ATSDR evaluated the types and quantities of chemicals detected in the air, water, and soil in the community to determine how children might be exposed and whether levels detected in the community could be associated with any reproductive or developmental effects.

While there are children living in this community, they generally do not have access to the Solite site. During site visits, ATSDR staff did not note any points of access for children to the plant property. ATSDR closely reviewed possible exposure situations for children while evaluating this site (for example, air exposure, trespassing, and soil in the community playground). In its evaluation, ATSDR used the Environmental Media Evaluation Guidelines for children (EMEGs), who are considered the most sensitive segment of the population. EMEGs are estimates of daily human exposure to a chemical that is unlikely to produce non-cancer health effects over a specific duration of time. No special chemical hazards to children were identified on the basis of available data. Because no historical air data are available for the surrounding community, no conclusions could be drawn regarding past air exposures. See Appendix D, page 2 for further explanation of comparison values used by ATSDR in this health assessment.

ATSDR reviewed two investigations conducted by the North Carolina Department of Health and Human Services. One study used existing health data and the other collected new information to examine disease in this community. The studies include a statistical investigation of cancer in Stanly county as well as biological sampling of residents in the area.

Area residents are concerned that emissions from the Solite facility may be causing excess cancer in their community. In response to these concerns, NC DHHS investigated cancer statistics for Stanly County to determine whether or not cancer rates in Stanly County are statistically different compared to rates in North Carolina and the United States. No formal report of this comparison was generated to interpret the comparison, and ATSDR analyzed raw data generated by the North Carolina State Center for Health Statistics.

Almost all diseases or health outcomes occur at different rates in different age groups. Most chronic diseases, including most cancers, occur more often among older people while other outcomes, such as many types of injuries, occur more often among younger people. Therefore, the most common health problems in a community will be influenced by the age distribution within the community.

One means of comparing the pattern of health outcomes in communities of different sizes is to calculate an incidence or mortality rate, which is the number of new cases or deaths divided by the size of the population. In chronic diseases and injuries, rates are usually expressed in terms of the number of new cases or deaths per 100,000 people per year. Adjusting rates for age allows for direct comparison between populations with potentially different age distributions. The cancer rates discussed below are age adjusted cancer rates.

In this analysis, cancer incidence rates of residents living in the same county as Carolina Solite (Stanly County) were compared to cancer rates of residents living in North Carolina and the rates of the entire US population. Stanly County and North Carolina cancer incidence rates were derived from the state cancer registry and population estimates from 1990-1995. Population estimates varied, but the average in Stanly County was approximately 53,064 people from 1990-1995. The state also varied, but averaged 6,905,124 people from 1990-1995 [12].

US cancer incidence rates were extrapolated from the Surveillance, Epidemiology, and End Results program (SEER) of the National Cancer Institute. The SEER database tracks cancers in five states (Connecticut, Hawaii, Iowa, New Mexico, Utah) and six metropolitan areas (Atlanta, Detroit, Los Angeles, Seattle/Puget Sound, San Francisco/Oakland, San Jose/ Monterey). With respect to selected demographic and epidemiologic factors, these areas are reasonably representative subsets of the United States population. The disease rates and patterns documented in the SEER database are accepted as fairly accurate representations of the disease incidence rates and patterns of the United States as a whole [13]. Therefore, the 'normal rates' of disease are often based on cancer rates in the SEER areas.

The cancer incidence and mortality data suggest that age-adjusted cancer rates for all cancers are actually lower in Stanly County than in North Carolina or the United States (336.6/100,000 vs. 367/100,000 and 410/100,000, respectively). However, Stanly County rates of cancer of the brain and central nervous system (CNS), bladder, melanoma, kidney, and liver were higher in Stanly county than in the state. However, only brain and CNS cancers in Stanly County exceeded cancer rates in the US population. These rates are difficult to compare because of the vast differences in population size between county and state and SEER rates. For example, the Stanly County rate of brain and CNS cancers is reported at 6.7 cases per 100,000 people. However, there were only approximately 50,000 residents in Stanly County during the study period. In reality, there were just three cases of brain and CNS cancers diagnosed in Stanly County in the six year study period.

Brain and CNS cancers are quite rare and in the instance of rare diseases, the larger the population from which the rate is derived the better the accuracy. The cancer rate derived from the diagnoses of three individuals is very small and therefore more likely to fluctuate, and is therefore less reliable. The rate of brain and CNS cancers diagnosed in the state and those SEER locations representing the US population cancer rates are more reliable because they are derived from a much larger population.

*estimated

¹It is common to standardize rates by reporting them as a number per 100,000 people. In actuality, Stanly County has about half that many residents, and the actual number of cancer cases reported was 3 from 1990-1995.

² These confidence intervals include 1, and are therefore not considered statistically significant.

Although the rate of brain and CNS cancers appear to be elevated in Stanly County above state and national rates, care should be taken in interpreting the meaning of these results. A further analysis of the rates was necessary to determine whether or not the rate observed in Stanly County are significantly higher than those of the state and U.S. (SEER) population. To test the difference between the numbers for statistical significance a Standardized Incidence Ratio (SIR) was calculated and then tested for significance. The SIR is calculated with a statistical formula; namely, the number of observed cases in Stanly County divided by the number of expected cases that are diagnosed in the comparison population (state or SEER population). An SIR of 1 means there is no difference between the rates of the two populations. The SIR for this analysis was 1.18 between Stanly County and the state rate and 1.098 between Stanly County and the U.S. (SEER) rate, suggesting that the rate for Stanly County is slightly higher than that of the state (18%) and slightly higher than the US population (9.8%). However, another test is necessary to determine whether or not the difference between the two numbers is statistically significant - i.e., that the numbers are different not by chance, but by some other factor.

The test for significance commonly used in statistics is called a test of confidence. This test is to determine whether the observed number of cases is truly elevated or possibly due to other factors such as a small population size, years observed, inaccurate data, and lifestyle or other risk factors that may influence the results. Although the level of confidence is determined by the investigator, a 95% confidence level is generally accepted as the most common confidence test. This means that the likelihood that the rates are different by chance alone (and that the SIR is greater than 1 by chance alone) is 5% or less. If the calculated confidence interval includes 1, then the SIR is not considered to be statistically significant; it is possible that the increase in the number of cancer cases observed in the population may be due to some other factor.

In this case, calculating the 95% confidence interval revealed that the difference between the state and national incidence rates and the Stanly County brain and CNS cancer incidence rate is not significant. The standard mortality ratio includes 1, and suggests that other factors are contributing to the brain cancers diagnosed, which may include sample size or the number of cases diagnosed. The population of Stanly County is small and the number of brain cancers (3) is also very small. Calculating reliable rates with such a small population size and such a rare cancer is very difficult.

The causes of most brain cancers in humans are unknown. The only environmental exposure for which there is strong evidence for a causal link to brain cancer in adult humans is ionizing radiation [14]. Though rare in children (incidence is approximately 25 per 1,000,000), brain tumors are the most common solid tumors in children. However, these tend to be associated with inherited conditions such as neurofibromatosis, tuberous schlerosis, and von Hippel-Landau disease [15]. Most cancers of the brain are secondary; meaning they have metastasized, or spread from another part of the body. A very small percentage of brain cancers actually originate in the brain. However, the data provided to ATSDR did not differentiate between primary and secondary brain cancers in Stanly County. The American Brain Tumor Association has stated that the incidence rate for primary malignant brain tumors in the United States is 6.6 people per 100,000, which is very similar to the Stanly County rate of 6.7 [16]. None of the contaminants detected in excess of ATSDR's CVs at this site are associated with brain cancer in humans, nor does the magnitude of the exposures and effects at this site suggest any such association.

In summary, more analysis is necessary in determining historical cancer trends in this county, and whether these trends are higher than the expected rates of cancer for Stanly County residents. More importantly, it is difficult to determine whether or not Carolina Solite is contributing to the cancer rates in the county. There are no cancer studies focusing specifically on the residential area surrounding the Solite facility. Furthermore, current environmental data do not support the association between environmental emissions and cancer in residents in this community.

The North Carolina Department of Health and Human Services conducted on-the-spot urine testing for heavy metals in April of 2000. Thirty residents living in the area around the Solite facility were asked to participate in the analysis. Participants included 18 females and 12 males. Ages ranged from 14 to 75 years. Smoking history was reported. Urine was screened for arsenic, mercury, lead, and cadmium. Although a 24-hour urine collection is considered an optimal sample due to fluctuations in excretion rates, most exposure studies, like this one, have used a first morning void or random, on-the-spot sample due to ease of collection [17]. Results were standardized by adjusting detected metals by the creatinine urine concentration.

Data from this analysis indicate that, while there were individuals with detectable concentrations of heavy metals in urine, none of the levels detected were above average ranges for a healthy, unexposed population. Of primary concern was arsenic levels in urine as a measure of exposure because of elevated arsenic in ambient air. In this investigation, arsenic was speciated, or measured in its organic and inorganic form. Speciated urinary arsenic is preferable to total urinary arsenic because the speciated forms can distinguish between exposure to toxic inorganic arsenic and its metabolites and non-toxic organic arsenic [17].

Inorganic arsenic was not detected in the 30 urine samples of residents. Organic arsenic was detected in 5 individuals. Detectable levels of organic arsenic is most likely attributable to diet. Three of the five individuals who had detectable levels of arsenic had eaten seafood within 72 hours of giving a sample [18]. Fish, shellfish, and other seafood are major sources of non-toxic organic arsenic [17]. While residential air has detectable levels of arsenic, urine analysis does not indicate elevated exposure (i.e., outside normal ranges) to inorganic arsenic. See Appendix F for biological sampling results.

'Biomarker' is a term used to describe how testing body fluids or tissues can give researchers clues about whether individuals are exposed to chemicals in their environment. A definition of biomarker is "a measurement made on body tissue, body fluid or excretion to give a quantitative indication of exposure to a chemical and which may give an estimate of the risks consequent on the exposure." Some biomarkers are more reliable than others for detecting the presence of specific chemicals and the sampling time relative to exposure duration can be critical. For example, arsenic is excreted mainly via the kidneys, with a half-life of about ten hours. Most of an ingested dose of arsenic will be cleared from the body in about 3 days [19]. Thus, urinary arsenic measurements will not reflect exposures older than that. Urine analysis is also a reliable test for measuring mercury and cadmium in the body [9,21]. However, measuring urinary lead levels is of questionable value as biomarkers of exposure because of the relatively low and fluctuating levels that are excreted in the urine. Blood lead levels are the preferred biomarkers for measuring lead exposure [22].

Arsenic was identified by NC DHHS and NC DENR as a contaminant of concern because of its elevation in community ambient air. Inhalation exposure to inorganic arsenic (primarily arsenic trioxide dust in air at copper smelters) is, in multiple studies, associated with increased risks of lung cancer in occupational settings. However, scientific literature does not support associations between lung cancer and exposure to airborne arsenic in residential settings [5]. Although serious health conditions can result from acute or long term exposure to inorganic arsenic, ATSDR does not expect adverse health conditions to result from the levels at which arsenic was detected in this community.

Arsenic is used as an animal feed additive [23]. Inorganic arsenic, in very small amounts, has been shown to be an essential nutrient in several species, e.g., chickens, goats, and rats, and although unproven, it is possible that a nutritional requirement for arsenic (estimated at between 12 and 50 ug/day) exists for humans as well [24]. Additionally, our bodies have the ability to change inorganic arsenic into organic arsenic. Negative health effects would be possible if this ability was overwhelmed. Inorganic arsenic is detoxified in the body by a biological process called "methylation". When the methylation capacity of the organism is saturated, the body begins to experience the toxic effects of the arsenic. In healthy humans, this methylation capacity prevents blood arsenic levels from rising at all until oral exposures reach at least 200 g daily. As a result, thresholds in excess of 200-250 g As/day exists for virtually all of the chronic adverse effects of arsenic (including cancer) in humans [24].

Organic arsenic, which is normally present at high levels in seafood, is relatively harmless because it is rapidly excreted. No studies exist that suggest associations between organic arsenic and adverse human health effects [5].

ATSDR's analysis suggests that concentrations of arsenic in the ambient air near the Solite facility is not a threat to human health. Mean levels of arsenic in ambient air in the United States usually range from 1 to 3 ng/m³ (nanograms per cubic meter) in remote areas and from 20 to 30 ng/m³ in urban or industrial areas. Inhalation of arsenic from ambient air is usually a minor exposure route for the general population. For example, the dose to a person who breathes 20m³ a day of air containing 20-30 ng/m³ would be about 0.4-0.6 g/day (micrograms per day) [5]. The highest level of arsenic detected in the air monitoring effort around this site was 24.7 ng/m³, but the vast majority of detects were well below that level. Arsenic was below detection limits in the breathing space of all twelve employees sampled in the industrial hygiene survey. The analytical detection level of worker exposure study (0.5g/m³) is 20 times lower than the safe occupational limit of 10g/m³ (.01 mg/m³), which is the appropriate benchmark for monitoring occupational exposures.

Arsenic was not detected in any of the 13 residential water wells sampled. In addition, urine analysis results did not reflect exposure of residents to inorganic arsenic. Instead the organic arsenic detected by urinalysis was most likely related to diet and recent exposure to seafood. Arsenic was not detected in groundwater, inorganic arsenic was not detected in urine of residents, and detected levels of arsenic in air are not expected to result in adverse health effects.

Cadmium was present in levels above environmental guidelines in ambient air approximately one-third of the time in 1999. Concentrations ranged from 0.61 to 6.3 ng/m³ (nanograms per cubic meter of air). Air cadmium levels in U.S. cities range from 1 to 40 ng/m³ [9]. The biggest sources of cadmium exposure are from food and cigarette smoke. Cadmium is found in small amounts in fruits and vegetables and in larger amounts in leafy vegetables and potatoes, shellfish, and meats [9, 19]. Smokers may inhale 1,000-3,000 ng/m³ of cadmium per day from each pack of cigarettes they smoke [9]. Although severe health effects can result from exposure to cadmium, no adverse health effects are expected to result from exposure to concentrations detected in the environmental media sampled.

While frequently above ATSDR CVs, levels of cadmium observed in the ambient air in this community do not currently pose a threat to human health. The Occupational Safety and Health Administration (OSHA) has determined that workers exposed chronically to cadmium dust or fumes in a typical workweek are safe breathing up to .005 mg/m³ ( 5 ug/m³ or 5,000 ng/m³). That safety level is approximately 800 times the highest level detected in the residential area surrounding the Solite facility. Additionally, cadmium was not observed in personal sampling of Solite employees above analytical detection limits in the state industrial hygiene study. OSHA limits for workers indicate that even at ten times the level of detection in this analysis (which all levels detected were below), the breathing conditions would be safe.

Cadmium was not detected in residential wells and is not a public health hazard at this time. Although cadmium was detected in the urine of ten of the thirty individuals sampled in the urine analysis when adjusted for creatinine levels, it was below the normal range of 5 g/L in all of tested individuals. Levels of cadmium detected in air, water, and urine do not pose a threat to human health at this time.

Chromium also exceeded ATSDR CVs in all but one air sampling effort of 1999. Chromium levels reported were not speciated, and reported levels were for total chromium. Chromium occurs naturally in the environment and has several forms. Chromium III is found in vitamins, dietary supplements, food, water, and air and is an essential nutrient for human survival. Chromium VI and chromium 0 are generally produced in industry. Chronic occupational exposure to high levels of chromium VI in air is associated with an increased incidence of lung cancer. Oral exposure to chromium VI is much less likely to pose a health threat as it is quickly and efficiently converted to the essential nutrient chromium III by the acids in beverages and bodily fluids [25].

Breathing high levels of toxic forms of chromium can result in adverse health effects [19,  25]. These results have generally been documented in factory workers who worked with chromium VI for extended periods of time. Long-term exposure to high levels of chromium VI has been associated with lung cancer. There is no evidence of these outcomes outside occupational settings. Breathing in small amounts of chromium VI does not cause health effects in most people. Levels of chromium detected in ambient air surrounding this facility are well below ATSDR comparison values, and are not expected to result in adverse health effects. These levels, which ranged from 0.18 to 5.5 nanograms (ng) per cubic meter (m³), were all well below ATSDR's chronic Environmental Media Evaluation Guides (EMEGs)/Minimum Risk Level (MRL) of 100 ng/m³ for chromium VI. Chromium was detected at 0.0003 mg/m³ in the air monitor of one of the twelve employees tested by the industrial hygiene survey. This level is below the National Institute of Occupational Safety and Health (NIOSH), OSHA, and American Conference of Governmental Industrial Hygienists (ACGIH) occupational limits of 0.5 mg/m³. Exposure to low levels of chromium measured here are unlikely to result in adverse health effects. During the 1999 sampling, chromium was not detected in the 13 residential water wells. Therefore, ATSDR considers that chromium in air and groundwater does not pose a hazard to public health in this community at the present time.

Access to Carolina Solite Corporation is restricted by fences. ATSDR has not received any information suggesting that children have access or have had access to the property in the past. Trucks regularly enter and exit the property and may pose traffic hazards to playing children and residents. Trucks are hosed off at the property line to prevent off-site contamination from dust and soils that may accumulate on truck bodies and tires while on facility property.

Available environmental data do not indicate the existence of a health hazard at this time for area residents of the Carolina Solite facility. Early in 2000, the facility agreed to discontinue the use of hazardous waste derived fuel to fire kilns, and now burns recycled oil exclusively. Ambient air sampling is needed to determine the impact of this change. Several air monitors have been added to existing stations to facilitate a more complete characterization of air contamination.

Based on data provided for this health assessment, ATSDR concludes the following:

• Air: In ambient air total suspended particulate samples, arsenic, cadmium, and chromium levels are not expected to result in any adverse health effects for area residents. In a study of Solite worker breathing conditions utilizing personal sampling filters, no contaminants were detected at levels of health concern.
  
  
• Residential Water Wells: While there is historical evidence of surface and groundwater contamination of water on Carolina Solite property, current conditions do not indicate contamination of residential water wells sampled in 1999.
  
  
• Biological sampling: None of the 30 individuals tested had urine levels of metals above normal ranges for a healthy, unexposed population. Although residents are exposed to elevated arsenic levels in ambient air, it does not appear that residents are exposed at levels high enough to constitute a health risk or to lead to bioaccumulation of organic or inorganic arsenic in the body.
  
  
• Data regarding rates of brain cancer and cancer of the central nervous system in Stanly County are inconclusive. Current environmental data do not support an association between the Solite facility and county cancer rates.
  
  

1. Air: Analyze ambient air total suspended particulates concentrations for all monitors operated through December 2000 to establish patterns in contaminant peaks, and to more fully characterize ambient air in the community.
   
   
2. Well Water: If contaminants sampled by the EPA are elevated in the sediment of streams and rivers in the area, NC DHHS and NC DENR should develop a public health action plan to monitor residential wells to ensure no leaching is occurring from the facility into groundwater.
   
   
3. Soil and Sediment: Analyze soil to fully characterize contamination on and off-site. Obtain contaminant background levels in soil and sediment from the United States Geologic Survey and the local agricultural extension service for a comparative analysis with EPA data results.
   
   

• The North Carolina Department of Environment and Natural Resources (NC DENR), Division of Air Quality has located six air sampling monitors on the perimeter of the Solite property and a background monitor approximately 6 miles from the Solite property.
  
  
• NC DENR conducted spot soil and groundwater sampling of various areas of the Carolina Solite facility in the early 1990s, and groundwater sampling of residential wells in 1999.
  
  
• EPA has taken soil and sediment samples on residential properties and rivers and streams in the vicinity of the Solite plant.
  
  
• NC DENR, Division of Air Quality monitored total suspended particulates and metals in air through December of 2000.
  
  
• EPA analyzed soil samples taken in the Spring of 2000, and submitted results to NC DENR, NC DHHS, and ATSDR.
  
  

• ATSDR is currently analyzing soil and sediment data collected by EPA in Spring of 2000.
  
  
• ATSDR is currently analyzing ambient air and total suspended particulate data collected by NC DENR from January through December 2000.
  
  
• ATSDR is currently investigating background levels of contaminants of concern with the USGS and the North Carolina Department of Agricultural.
  
  

• ATSDR will address any comments received about this public health assessment by residents, state officials, and other stakeholders.
  
  
• ATSDR will produce a public health assessment for soil, sediment, and air data.
  
  
• ATSDR will continue to give technical support, as needed, to NC DENR and NC DHHS.
  
  

Site Team/Authors

Prepared by:

Michelle A. Colledge, M.P.H.
Environmental Health Scientist
Petitions Response Section
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

Frank Schnell, Ph.D.
Toxicologist
Petitions Response Section
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

Reviewed by:

Benjamin Moore
Regional Representative
Office of Regional Operations
ATSDR Region 4

Donald Joe, P.E.
Section Chief
Petitions Response Section
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

John E. Abraham, Ph.D., M.P.H.
Branch Chief
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

15.  Casciato and Lowitz. Manual of Clinical Oncology, third ed. New York: Brown and Company, pp 258, 315; 1995.

16.  A Primer of Brain Tumors, seventh ed. The American Brain Tumor Association. Revised Nov. 2000.

17.  Imtiaz R. Exposure Investigation Protocol, Vasquez Boulevard and I-70 Site. Agency for Toxic Substances and Disease Registry. U.S. Department of Health and Human Services. Atlanta. September 2000.

18.  Residential Urine Analysis-Solite Vicinity. North Carolina Department of Health and Human Services, Division of Public Health. August 4, 2000.

19.  Goyer RA. Toxic Effects of Metals. Casserett and Doull's Toxicology, fourth ed. New York: Pergamon Press, 1991. Chapter 19, p. 630.

20.   Agency for Toxic Substances and Disease Registry. Toxicological profile for mercury. Department of Health and Human Services. August 1997. Update.

21.  Gebel TW et al. Human biomonitoring of arsenic and antimony in a case of an elevated geogenic exposure. Environ Health Perspect 106:33-39, 1998.

22.   Agency for Toxic Substances and Disease Registry. Toxicological profile for lead. Department of Health and Human Services. 1998. Update.

23.   Kotsonis et al. Food Toxicology. Casarett and Doull's Toxicology. fifth ed. New York:McGraw-Hill, 1996.

24.   Marcus and Rispin. Threshold carcinogenicity using arsenic as an example. Advances in Modern Environmental Toxicology: Risk Assessment and Risk Management of Industrial and Environmental Chemicals. Princeton Scientific Publishing Company, Princeton. pp133-57; 1988.

25.   Agency for Toxic Substances and Disease Registry. Chromium, Toxicological profile for chromium. U.S. Department of Health and Human Services. August 1998.

Appendices

Table 1.   Block Group and County Age Group Data, 1998 Projection*

*Data for this table were generated by the Compass program, with PRIZM applications

¹Where n=5,607 persons

Quality Assurance

In preparing this report, ATSDR relied on the information provided in the referenced documents and 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 in this 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 under default conditions of exposure. They are used as screening values in the preliminary identification of site-specific "contaminants of concern". The latter term should not be misinterpreted as an implication of "hazard". As ATSDR uses the phrase, a "contaminant of concern" is a chemical substance detected at the site in question and selected by the health assessor for further evaluation of 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's comparison values.

However, it must be emphasized that comparison values are not thresholds of toxicity. Although concentrations at, or below, the relevant comparison value may reasonably be considered safe, it does not automatically follow that any environmental concentration that exceeds a comparison value would be expected to produce adverse health effects. The principle purpose behind protective health-based standards and guidelines is to enable health professionals to recognize and resolve potential public health hazards before they become actual public health consequences. For that 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) on which they are based. The probability that such effects will actually occur does not depends on environmental concentrations alone, but on a unique combination of site-specific conditions and individual lifestyle and genetic factors that affect the route, magnitude, and duration of actual exposure.

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.

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 (doses expressed in mg/kg/day) that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. MRLs are calculated using data from human and animal studies and are reported for acute ( 14 days), intermediate (15-364 days), and chronic ( 365 days) exposures. MRLs are published in ATSDR Toxicological Profiles for specific chemicals.

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

Intermediate Environmental Media Evaluation Guides (IEMEG) are calculated from ATSDR minimal 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 body weight and intake rates are taken into account.

Reference Dose (RFD) is an estimate of the daily exposure to a contaminant unlikely to cause noncarcinogenic adverse health effects. Like ATSDR's MRL, EPA's RFD is a dose expressed in mg/kg/day.

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

Risk-Based Concentrations (RBC) are media-specific concentrations derived by Region III of the Environmental Protection Agency from RfD's, RfC's, or EPA's cancer slope factors. They represent concentrations of a contaminant in tap water, ambient air, fish, or soil (industrial or residential) that are considered unlikely to cause adverse health effects over a lifetime of chronic exposure. 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 of chemicals that can reasonably (and conservatively) be regarded as harmless, based on the scientific data the agency has collected in its toxicological profiles. The resulting comparison values and health guidelines, which include ample safety factors (also known as an uncertainty factor) to ensure protection of sensitive populations, are used to screen contaminant concentrations at a site and to select substances (referred to as "chemicals of concern") that warrant closer scrutiny. A "chemical of concern" is defined by ATSDR as any chemical that is detected in air, water, or soil at concentrations exceeding one or more of ATSDR's comparison values. (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. Although concentrations at, or below, the relevant comparison value may reasonably be considered safe, it does not necessarily follow that any concentration that exceeds a comparison value would be expected to produce adverse health effects. Indeed, the principle purpose behind protective health-based standards and guidelines is to enable health professionals to recognize and resolve potential public health problems before that potential is realized. For that reason, ATSDR's comparison values are typically designed to be 1 to 3 orders of magnitude lower than the corresponding no-effect levels (or lowest-effect levels) on which they are based.

When screening individual contaminants, ATSDR staff compare the highest single concentration of a contaminant detected at the site with the lowest comparison value available for the most sensitive of the potentially exposed individuals (usually children or pica children). Typically the cancer risk evaluation guide (CREG) or chronic environmental media evaluation guide (EMEG) is used. This "worst-case" approach introduces a high degree of conservatism into the analysis and often results in the selection of many contaminants as "chemicals of concern" that will not, upon closer scrutiny, be judged to pose any hazard to human health. In the interest of public health, it is prudent to use a screen that identifies many "harmless" contaminants, as opposed to one that may overlook even a single potential hazard to public health. The reader should keep in mind the conservativeness of this approach when interpreting ATSDR's analysis of the potential health implications 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 Protection Agency (EPA) estimate, corresponds to a 1-in-1,000,000 cancer risk level. Note, this does not mean that exposures equivalent to the CREG are expected to cause 1 excess cancer case in 1,000,000 (1x10^-6) persons exposed over a lifetime. Nor does it mean that every person in a population of one million has a 1-in-1,000,000 risk of developing cancer from the specified exposure. Although commonly interpreted in this way, EPA estimates of cancer "risk" are estimates of population risk only and cannot be applied meaningfully to any individual. EPA explicitly stated in it's 1986 Cancer Risk Assessment Guidelines that "The true risks are unknown and may be as low as zero" (EPA, 1986).

Reference:

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 toxicological profiles, ATSDR has determined concentrations of hazardous substances that can reasonably (and conservatively) be regarded as harmless. The resulting comparison values generally include ample safety factors to ensure protection of sensitive populations. They are used to screen contaminant concentrations at a site, and to select "contaminants of concern" that warrant closer scrutiny by agency health assessors and toxicologists. A "contaminant of concern" is defined as a substance that is detected in air, water, or soil at concentrations that exceed one or more of ATSDR's comparison values and warrants further evaluation.

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

Comparison values are conservative values, and it is important to note that concentrations of substances that are higher than the comparison values will not necessarily lead to adverse health effects. Exposure to levels of substances above their comparison values may or may not lead to adverse health effects. ATSDR's comparison values do not indicate thresholds of toxicity, and they 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 the concentration is expected to produce adverse health effects. ATSDR uses highly conservative, health-based standards and guidelines to assist health professionals in recognizing and resolving potential public health problems.

*ng/m³=nanograms per cubic meter

g/m³=micrograms per cubic meter

¹g/m³= micrograms per cubic meter

²Samples are most likely not representative of true ambient conditions because this monitor was located adjacent to a dirt road.

Table 3. Personal air monitor sampling results for Carolina Solite employees

¹g/m³= microgram per cubic meter

²The comparison values used here are NIOSH Recommended Exposure Levels (RELs), OSHA Permissible Exposure Levels (PELs), and ACGIH Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs), where applicable.

³BDL= below the detection limit of the analytical method

Table 1. 1999 Residential well investigation

¹Please note: trace amounts of the following contaminants were found at levels less than .5 ppb: toluene, styrene, 1,1-dichloroethane, and chloroform. These contaminants detected at these levels or lower are well below ATSDR and EPA health-based guidelines.

²BDL= below detection limits; or that the level detected was below the registering capability of the measuring instrument

³NPDWR (National Primary Drinking Water Standards)- legally enforceable standards that apply to public water systems. Primary standards protect drinking water quality by limiting the levels of specific contaminants that can adversely affect public health and are known or anticipated to occur in public water systems.

⁴ NSDWR (National Secondary Drinking Water Standards)- non-enforceable guidelines regulating contaminant that may cause cosmetic effects (like tooth discoloration) or aesthetic effects (taste, odor) in drinking water. EPA recommends secondary standards but does not require systems to comply. Some states adopt then as enforceable standards.