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PETITIONED PUBLIC HEALTH ASSESSMENT

CAROLINA SOLITE CORPORATION
(a/k/a CAROLINA SOLITE CORPORATION/AQUADALE)
NORWOOD, Stanly County, NORTH CAROLINA


SUMMARY

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 publichealth assessment of the areas surrounding the Carolina Solite facility located in Aquadale, NorthCarolina. The petition was filed on behalf of area residents. Residents are concerned aboutadverse health effects they believe are the result of long term exposure to emissions from theSolite facility.

ATSDR reviewed all available environmental and health outcome data and concludes that thedata do not suggest a current threat to human health. Data reviewed for this document indicatethat environmental media may contain chemical contamination, but below levels that have beenassociated with adverse health effects. Biological data do not reflect exposures to contaminationat 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 thecommunity are not a public health hazard. Onsite emissions are not a public health hazardto Solite employees. ATSDR was unable to assess health implications of past exposurebecause no historical environmental sampling data exists.

  • Groundwater: Current tests indicate that groundwater in this community is safe for humanconsumption. Levels of metals and volatile organic compounds detected in groundwaterare 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.

INTRODUCTION

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.


BACKGROUND

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

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

In the past, Carolina Solite has used a number of fuels to fire its kilns. In Spring of 2000, thefacility 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 thefurnaces. Carolina Solite received the HWDF via a pipeline and trucks from Giant ResourceRecovery, a contiguous permitted liquid waste blending and storage facility [3].


DEMOGRAPHICS

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 levelonly [4]. Block groups contain between 250 and 550 housing units and are often used todistinguish 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 aswell as comparison data for Stanly County.

The block groups in this area are predominantly Caucasian; approximately 90% of the 5629residents are Caucasian. African Americans account for 9.3% of the total population and about1% are of another race. Less than 1% of residents are of Hispanic origin. Median age varies forthese block groups (between 36.140.2), but average 38.4 years. This is slightly higher than thecounty, whose median age is 37.1. Figure 1 and Table 1 in Appendix B illustrate the agedistribution in this community. The median number of school years completed is 12.3. Medianhousehold income in this area varies greatly, from $30,750 to $39,318, but averages $34,815. Thisis on average higher than the median household income of the county, which is $31,652. The areaappears to be relatively stable in that the median length of residence is 15.5 years, in contrast tothe 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.


COMMUNITY HEALTH CONCERNS

In the early 1990s, residents expressed their concerns to state authorities about potentialenvironmental contamination and human exposure from site emissions. The concerns included theincidence of different types of cancers, Alzheimer's Disease, asthma, sinus conditions, andneurological illnesses. Specific cancers of concern were: leukemia and brain, kidney, colon, lung,and skin cancers. The North Carolina Department of Health and Human Services (NC DHHS)and the North Carolina Department of Environment and Natural Resources (NC DENR) haveinvestigated contamination, exposure, and compliance issues at the facility and surrounding areas.Sampling has consistently detected metals in ambient air near the facility. Groundwatermonitoring in 1991 found elevated metals in monitoring and supply well, surface water, andsediment samples collected near or on Solite property. Of particular concern to state agencies andresidents is the level of arsenic that has been detected in residential air. Currently, the UnitedStates 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.


DISCUSSION

Methods

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 exposurepathway analyses, ATSDR's health comparison values, and the methods of selectingcontaminants above comparison values), please refer to Appendix C.

Extent of Contamination

This health assessment will review air monitoring data, residential well data, and health outcomedata 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 propertiessampled in 1991 and 1999, air monitoring data on four sampling sites that were collectedthroughout 1999, personal monitoring data of employees of the Carolina Solite facility, cancerstatistics, and urine sample data for 30 residents living in the area collected during 2000. Thisanalysis is based on the site-specific data provided to ATSDR for review, which are limited inscope by the time period of the data collection and by the assumption that proper qualityassurance/quality control standards were followed in analyzing laboratory results. The results ofsoil and sediment sampling collected by the EPA will be evaluated in a future public healthconsultation. Through air monitoring, arsenic has been identified by NC DHHS and ATSDR as acontaminant of concern at this site.

Potential Exposure Pathways

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 tocontamination migrating from the site. An exposure pathway contains the following fiveelements: 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 evaluatedchemicals in the air and groundwater that people living in the nearby residences may consume orcontact in some manner.

Air

Ambient air

Four ambient air monitoring sites were located and operated in near the Solite property in 1999 byNC DENR, Division of Air Quality. Two additional monitoring sites were located in the area in2000. However, only 1999 data is analyzed in this health assessment. Four of the six monitors thathave been located in the area were operated until the middle or end of 2000. One of these includesa regional background site that is not expected to be impacted by facility emissions. The initialsites and one of the locations added in 2000 were placed in locations believed to be maximumimpact 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 metalsand 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 arsenicconcentrations exceeded CVs in 168 of the 169 samples collected. Cadmium was also frequentlydetected; it exceeded CVs in 51 out of 169 samples collected. The results of the 1999 data, as wellas a map of sampling locations can be found in Appendix D.

Arsenic and cadmium sources in ambient air have not been specifically identified. Although thefacility is possibly contributing to the contamination, farming practices may also increase levels ofarsenic and cadmium. The area surrounding this facility is rural and agricultural crops arecommon, especially cotton. Arsenic is a common ingredient in agricultural chemicals such asinsecticides, herbicides, algicides, and growth stimulants for plants and animals [5]. In 1999,Stanly County harvested 11,500 acres of cotton [6]. Monosodiummethylarsenate (MSMA) is usedextensively 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 usuallyapplied at a higher concentrations than MSMA. State officials report that the manufacturerrecommended application of MSMA is 2.1 pounds applied per acre of cotton fields, 46% of whichis arsenic [7].

Upon investigation, ATSDR determined that during 1999 the highest concentrations for arseniccould not be clearly associated with harvest and summer planting months when soils aredisturbed. In Stanly County, the three largest crops are soybeans, cotton, and corn. These crops areusually planted between April and June, and harvested in late September or later. For example, thebulk of cotton crops are planted by the 10th of May. The cotton crops receive applications ofMSMA and DSMA in late May when the crop is in a "two leaf" stage and plants are veryyoung, and again in late June prior to first bloom [8]. The peaks observed in arsenic levels in 1999were not observed during the periods of MSMA and DSMA application, but later in July andthrough August. The cotton planting month of May and harvesting month of October were notfound 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]. Chromiumis not a common ingredient in agricultural products. Because there are many potential sources ofchromium in air, sources besides the Solite facility have not been identified.

Particulates in Air

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

In the community around the Solite site, particulate matter was sampled continuously for ninemonths at two locations, and 24-hour averages were taken every day during that time. TSP levelswere recorded for the entire nine month period (January through mid-September) at two samplingsites, 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 150µg/m3 (24-hour average) for three of the four 1999 monitoring locations. One TSP monitoring sitewas closed down by NC DENR, Division of Air Quality, when it was determined that the samplerwas impacted by dust originating from a nearby dirt road. It exceeded EPA recommended levelsfor 5 days during the monitoring period, most likely because of its susceptibility to dust frompassing traffic. The nine month averages of the monitors were within acceptable annual ranges of75µg/m3 for total suspended particulates and 50µg/m3 for PM10 [10]. See Appendix D, Table 2for particulate sampling data.

Personal air samplers

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

The samples were collected and analyzed for metals using appropriate equipment and testingmethods designated by the Occupational Safety and Health Administration (OSHA). A sampleof bulk dust was collected from a drill hole in the quarry and a bulk sample of expanded rawmaterial ('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 isprovided in the contaminants of concern section of this document.

Drinking water wells

Historical permit violations have resulted in spot sampling of different areas of the Soliteproperty. 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 alsodetected in these sampling efforts. They included zinc, aluminum, iron, lithium, arsenic,manganese, magnesium, cadmium, copper, chromium, and barium. Concerns about leaching ofcontamination into water sources prompted the investigation of potential residential water wellcontamination. Residential wells were sampled in 1991 and 1999. The 1991 sampling did notindicate chemical contamination of residential wells, but did indicate slight elevations of ironand manganese in several wells. The investigation concluded that the elevations of these metalswere most likely naturally occurring and were not a threat to human health.

Thirteen residential drinking water wells were sampled by the North Carolina Department ofEnvironment and Natural Resources, Division of Water Quality in October 1999. Wells weresampled for volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), andmetals. Barium, copper, iron, lead, and manganese were detected, all at levels below ATSDRcomparison values (CVs) and EPA risk based guidelines (RBCs). Iron was the most commonlydetected in 10 of 13 wells. All metals detected were below National Primary Drinking WaterRegulations for all metals except iron and manganese, neither of which have primary standardlevels. Both of these metals slightly exceeded Secondary Drinking Water Regulations, which arenon 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 asseveral other metals were below detection limits (BDL); however, the detection limit of theinstrument was higher than some of the most conservative health based guidelines for arsenic andcadmium. Even if these two metals has been detected at concentrations equal to the detectionlimit of the instrument, they are not expected to result in adverse health conditions. Traceamounts of the toluene, styrene, 1,1-dichloroethane, and chloroform were detected at levels lessthan 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.

ATSDR Child Health Initiative

Children are at greater risk than adults for certain kinds of exposure to hazardous substancesemitted 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 duringcertain growth stages.
  • Children play outside more than adults, and therefore have an increased likelihood ofcoming 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 levelsdetected 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 theSolite site. During site visits, ATSDR staff did not note any points of access for children to theplant property. ATSDR closely reviewed possible exposure situations for children whileevaluating this site (for example, air exposure, trespassing, and soil in the communityplayground). In its evaluation, ATSDR used the Environmental Media Evaluation Guidelines forchildren (EMEGs), who are considered the most sensitive segment of the population. EMEGs areestimates of daily human exposure to a chemical that is unlikely to produce non-cancer healtheffects over a specific duration of time. No special chemical hazards to children were identifiedon the basis of available data. Because no historical air data are available for the surroundingcommunity, no conclusions could be drawn regarding past air exposures. See Appendix D, page 2for further explanation of comparison values used by ATSDR in this health assessment.

Health Outcome Data

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

North Carolina Department of Health and Human Services-1998
North Carolina Department of Health and Human Services, Division of Occupational and Environmental Epidemiology; State Center for Health Statistics

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

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

One means of comparing the pattern of health outcomes in communities of different sizes is tocalculate an incidence or mortality rate, which is the number of new cases or deaths divided bythe size of the population. In chronic diseases and injuries, rates are usually expressed in terms ofthe number of new cases or deaths per 100,000 people per year. Adjusting rates for age allows fordirect comparison between populations with potentially different age distributions. The cancerrates 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 therates of the entire US population. Stanly County and North Carolina cancer incidence rateswere derived from the state cancer registry and population estimates from 19901995. Populationestimates varied, but the average in Stanly County was approximately 53,064 people from1990-1995. 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 EndResults program (SEER) of the National Cancer Institute. The SEER database tracks cancers infive states (Connecticut, Hawaii, Iowa, New Mexico, Utah) and six metropolitan areas (Atlanta,Detroit, Los Angeles, Seattle/Puget Sound, San Francisco/Oakland, San Jose/ Monterey). Withrespect to selected demographic and epidemiologic factors, these areas are reasonablyrepresentative subsets of the United States population. The disease rates and patternsdocumented in the SEER database are accepted as fairly accurate representations of the diseaseincidence 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 ageadjusted cancer rates for all cancers areactually 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 brainand central nervous system (CNS), bladder, melanoma, kidney, and liver were higher in Stanlycounty than in the state. However, only brain and CNS cancers in Stanly County exceededcancer rates in the US population. These rates are difficult to compare because of the vastdifferences in population size between county and state and SEER rates. For example, the StanlyCounty 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. Inreality, 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.

Location Population Rate of Brain and CNS Cancers Actual number of brain and CNS cancers diagnosed (1990-1995)

SEER Locations

24,770,700

6.1/100,000

1511*

North Carolina

6,905,124

5.7/100,000

394*

Stanly County, NC

53,000

6.7/100,000

3

*estimated

Number of cases observed1 Number of cases expected Standard Incidence Ratio 95% confidence interval2
3 (rate of 6.7/100,000) 6.1/100,000 (SEER rate) 1.098 0.027-6.11
  5.7/100,000 (state rate) 1.18 0.030-6.57

1 It 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 todetermine whether the observed number of cases is truly elevated or possibly due to other factorssuch as a small population size, years observed, inaccurate data, and lifestyle or other risk factorsthat may influence the results. Although the level of confidence is determined by theinvestigator, 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 isgreater 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 thenumber 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 thestate and national incidence rates and the Stanly County brain and CNS cancer incidence rate isnot significant. The standard mortality ratio includes 1, and suggests that other factors arecontributing to the brain cancers diagnosed, which may include sample size or the number ofcases diagnosed. The population of Stanly County is small and the number of brain cancers (3) isalso very small. Calculating reliable rates with such a small population size and such a rare canceris 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.

Biological Sampling-2000
North Carolina Department of Health and Human Services

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 concentrationsof 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 exposurebecause of elevated arsenic in ambient air. In this investigation, arsenic was speciated, ormeasured in its organic and inorganic form. Speciated urinary arsenic is preferable to total urinaryarsenic because the speciated forms can distinguish between exposure to toxic inorganic arsenicand its metabolites and non-toxic organic arsenic [17].

Inorganic arsenic was not detected in the 30 urine samples of residents. Organic arsenic wasdetected 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 72hours of giving a sample [18]. Fish, shellfish, and other seafood are major sources of nontoxicorganic arsenic [17]. While residential air has detectable levels of arsenic, urine analysis does notindicate elevated exposure (i.e., outside normal ranges) to inorganic arsenic. See Appendix F forbiological sampling results.

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

Public health implications

Contaminants of Concern

Arsenic
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, hasbeen shown to be an essential nutrient in several species, e.g., chickens, goats, and rats, andalthough unproven, it is possible that a nutritional requirement for arsenic (estimated at between12 and 50 ug/day) exists for humans as well [24]. Additionally, our bodies have the ability tochange inorganic arsenic into organic arsenic. Negative health effects would be possible if thisability 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 toexperience the toxic effects of the arsenic. In healthy humans, this methylation capacity preventsblood arsenic levels from rising at all until oral exposures reach at least 200 µg daily. As a result,thresholds in excess of 200-250 µg As/day exists for virtually all of the chronic adverse effects ofarsenic (including cancer) in humans [24].

Organic arsenic, which is normally present at high levels in seafood, is relatively harmlessbecause it is rapidly excreted. No studies exist that suggest associations between organic arsenicand 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 2030 ng/m3 would be about 0.40.6 µg/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 (0.5µg/m3) is 20 times lower than the safe occupational limit of 10µg/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, urineanalysis results did not reflect exposure of residents to inorganic arsenic. Instead the organicarsenic 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, anddetected levels of arsenic in air are not expected to result in adverse health effects.

Cadmium

Cadmium was present in levels above environmental guidelines in ambient air approximatelyonethird of the time in 1999. Concentrations ranged from 0.61 to 6.3 ng/m3 (nanograms percubic meter of air). Air cadmium levels in U.S. cities range from 1 to 40 ng/m3 [9]. The biggestsources of cadmium exposure are from food and cigarette smoke. Cadmium is found in smallamounts in fruits and vegetables and in larger amounts in leafy vegetables and potatoes, shellfish,and meats [9,19]. Smokers may inhale 1,0003,000 ng/m3 of cadmium per day from each pack ofcigarettes 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 theenvironmental 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 urineanalysis when adjusted for creatinine levels, it was below the normal range of 5 µg/L in all oftested individuals. Levels of cadmium detected in air, water, and urine do not pose a threat to human health at this time.

Chromium

Chromium also exceeded ATSDR CVs in all but one air sampling effort of 1999. Chromiumlevels reported were not speciated, and reported levels were for total chromium. Chromiumoccurs 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 occupationalexposure to high levels of chromium VI in air is associated with an increased incidence of lungcancer. Oral exposure to chromium VI is much less likely to pose a health threat as it is quicklyand efficiently converted to the essential nutrient chromium III by the acids in beverages andbodily 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 setttings. 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.

Physical Hazards

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.


CONCLUSIONS

Available environmental data do not indicate the existence of a health hazard at this time forarea residents of the Carolina Solite facility. Early in 2000, the facility agreed to discontinue theuse of hazardous waste derived fuel to fire kilns, and now burns recycled oil exclusively. Ambientair sampling is needed to determine the impact of this change. Several air monitors have beenadded 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 chromiumlevels 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 groundwatercontamination of water on Carolina Solite property, current conditions do not indicatecontamination 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 associationbetween the Solite facility and county cancer rates.

RECOMMENDATIONS

  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.

PUBLIC HEALTH ACTION PLAN

Completed Activities:

  • 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 theSolite 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 CarolinaSolite 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 inair through December of 2000.

  • EPA analyzed soil samples taken in the Spring of 2000, and submitted results to NCDENR, NC DHHS, and ATSDR.

Ongoing Activities:

  • 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.

Future Activities:

  • ATSDR will address any comments received about this public health assessment byresidents, 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 NCDHHS.

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


REFERENCES

  1. North Carolina Waste Awareness and Reduction Network. Petition letter to ATSDR.Atlanta. August 8, 1998.

  2. RCRA Facility Assessment of Carolina Solite Corporation and Oldover Corporation. Submitted by A.T. Kearney, Inc. to The U.S. Environmental Protection Agency. EPA Contract Number 68-W9-0040, work assignment number R04-23-03. September 1992.

  3. Sampling and analysis plan for soil, sediment, and air monitoring near Solite Corporation in Stanly County. North Carolina Department of Health and Human Services, March 2000.

  4. Claritas, Inc. 1999 Population and Housing Estimates. 1999. Claritas, Inc: Arlington,VA.

  5. Agency for Toxic Substances and Disease Registry. Toxicological profile for arsenic. U.S. Department of Health and Human Services. April 1993. Update. Report No. TP-92-02

  6. Stanly County Crop Statistics. North Carolina Department of Agriculture. 2000.http://www.agr.state.nc.us

  7. Correspondence between Luann Williams (North Carolina Department of Health andHuman Services) and North Carolina Department of Agriculture (contact not identified),1999.

  8. Conversation between Michelle Colledge of ATSDR and A.C. York of the North CarolinaDepartment of Agriculture, February 2001.

  9. Agency for Toxic Substances and Disease Registry. Toxicological profile for cadmium.U.S. Department of Health and Human Services. Update, July 1999.

  10. Telephone conversation between Michelle Colledge (ATSDR) and Charles Davis (NorthCarolina Department of Environment and Natural Resources); September 19, 2000.

  11. Industrial Hygiene Survey. North Carolina Department of Health and Human Services,Division of Public Health. July 2000.

  12. U.S. Census Population Estimates; county and state estimates 1990-1996. Unites States Census, Population Division, Population Distribution Branch.

  13. Surveillance, Epidemiology, and End Results Program. National Cancer Institute, 2000.

  14. Inskip-et. al. Etiology of Brain Cancer in Adults. Epidemiologic Reviews 17:382-414, 1995.

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

  16. A Primer of Brain Tumors, seventh ed. The American Brain Tumor Association. RevisedNov. 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.

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