PUBLIC HEALTH ASSESSMENT
LAIDLAW ENVIRONMENTAL SERVICES (TOC), INCORPORATED
ROEBUCK, SOUTH CAROLINA
ATSDR evaluates contaminants detected in environmental media at the site and determineswhether an exposure to them has public health significance. ATSDR selects and discusses thecontaminants based upon the following factors:
- concentrations of contaminants on- and off-site;
- community health concerns; and
- comparison of on- and off-site concentrations with ATSDR health comparisonvalues for (1) noncarcinogenic endpoints and (2) carcinogenic endpoints.
ATSDR health comparison values are concentrations of contaminants which are media specific(e.g. water, air, or soil). The comparison values are considered to be safe under defaultconditions of exposure and are used as screening values in the preliminary identification of site-specific "contaminants of concern." The "contaminants of concern" are those contaminants thatwere detected above the screening comparison values and contaminants without comparisonvalues. The fact that a contaminant is discussed does not mean that site-specific exposure to thesubstance will result in adverse health effects. Rather, the contaminant will be evaluated insubsequent discussions in the document. Please refer to the Toxicological Evaluation sectionand Appendix C for further clarification and description of the comparison values used in thispublic health assessment.
Following the preliminary identification of site-specific "contaminants of concern" which aredescribed in this section, ATSDR staff determined whether nearby residents are exposed tocontamination migrating from the site in the Pathways Analyses section of this public healthassessment. If exposure to contamination is identified, the significance of this exposure withrelation to adverse health effects is discussed in the Toxicological Evaluation section. ATSDRstaff also address specific community concerns in the Community Health Concerns Evaluationsection of this public health assessment. Lastly, based on the evaluations from all precedingsections of the public health assessment, ATSDR staff determine conclusions and preparerecommendations.
For this public health assessment, ATSDR staff obtained and evaluated environmental data forgroundwater, air, soil, sediment, and surface water. This section will discuss available samplingdata both on-site and off-site. For the purpose of this report, sampling that was conducted on theLaidlaw incineration facility property and the adjacent ABCO facility property is considered on-site and sampling in residential areas is considered off-site. The contaminants detected in eachenvironmental medium are found in table format in Appendix B. Contaminants listed in thetables will not necessarily cause adverse health effects at the levels detected.
There are 29 groundwater monitoring wells that are sampled on a quarterly basis. The purpose ofthese wells is to monitor the migration of the 'salt' and 'organic' plumes. The groundwater ismonitored for metals, pesticides/herbicides, and volatile organics as well as various water qualityindicators. Groundwater contamination has not migrated off-site (28). Groundwater monitoringdata from 1987 through 1996 were collected and reviewed. Please refer to Figure 6, Appendix A, for a location map of the groundwater monitoring wells.
The salt plume appears to originate from the former scrubber ponds. The primary constituents ofthe salt plume include chloride, barium, and sodium. Primarily, chloride appears to havemigrated toward the unnamed tributary and also appears to be migrating vertically as well (4). Barium and sodium do not appear to be migrating as rapidly as chloride (4). The scrubber pondshave been remediated.
The volatile organic compound (VOC) plume appears to originate from a source locatedupgradient of the existing wells in the area (4). Please refer to Figure 8, Appendix A, for a mapindicating the boundaries of the VOC plume as of 1996. One potential source is a spill thatoccurred prior to current ownership of the property. Please refer to Table 3 and Table 4,Appendix B, for a compilation of the results of groundwater monitoring events occurringbetween 1987-1996.
Laidlaw operated two air monitoring stations at the facility. One of these stations was locatedupwind to assess background concentrations. The other station was located in the containerstorage area for the purpose of monitoring emissions during the de-drumming process. SCDHEC provided ATSDR with hourly air concentrations from these stations for hydrochloricacid (HCL) for three days in January 1997 (the 21st-23rd) surrounding an incident at the facility. Data (24-hour average air concentrations) were also provided for each day in January throughMay, 1998. The maximum 24-hour average HCL concentration was 4.980 parts per million(ppm) at the background station in May of 1998 and 2.358 ppm at the container storage station inJanuary of 1998. Both of these values are below EPA's reference concentration (RfC) of 13.6ppm.
A soil boring program was conducted as part of the RCRA Facility Investigation. Soil sampleswere collected at the facility during 1988/1989 at various depths. A total of 14 borings weredrilled. Nine borings were located in the former blend tank area, two borings were locatedbetween the pond and storage tank areas, two borings were located in the gas tar pond area, andone boring was located in an on-site area considered background. Also in 1988, soil sampleswere taken from four pits in the gas tar pond area.
In 1982, a spill was documented in the area of the former blend tanks. A small section of pipingwhich transfers liquid feed material was corroded and leaking. The total discharge wasapproximately 3,000 gallons of chlorinated and non-chlorinated solvents including toluene,methyl ethyl ketone, lube oils, mineral spirits, organic phosphites, xylene, alcohol, phenol andwater of which approximately 700 gallons of the material escaped ABCO's containment area byflowing through a storm drainage ditch to an unnamed tributary of the Stillman Branch (29). Given the concentration of VOCs in the groundwater in this area, the soil boring programexpected to detect high concentrations of VOCs although this was not the case (4). Please referto Table 7 and Table 8, Appendix B, for the soil sampling results.
When the facility was operated by ABCO, several ponds were used on-site. During the late1970s and early 1980s, ABCO was cited for several incidents revolving around surface waterdischarges. In some instances, the unlined scrubber ponds were at the maximum level. Runofffrom the incinerator area, containing the scrubber wastes, would discharge to the spill pond. Two lines from the spill pond would then siphon wastewater out of the pond and discharge to thecreek (22). This discharge was reported as having visible foam and a light brown color. Nosamples were taken. ABCO also used a spray field for the disposal of wastewater. Ponds belowthe spray field were known to overflow. Please refer to Table 9, Appendix B, for samplingresults from the spray field ponds. As mentioned earlier, the scrubber ponds have beenremediated. Further, the spray field is no longer used.
The current facility owner, Laidlaw Environmental Services (TOC), has also been cited forincidents concerning surface water discharges in the early 1990s. Effluent from Laidlaw'swastewater treatment area combined with effluent from ABCO's wastewater treatment plant andthen traveled through pipelines to discharge to the North Tyger River. In the past, Laidlaweffluent has exceeded permitted limits for mercury, lead, cadmium, zinc, copper, antimony andnickel. Mercury excursions occurred on a regular basis.
In March of 1997, a nearby resident requested a private well sample. The resident was concernedthat ABCO's former spray field could have contaminated the drinking water. This private well islocated south of the former ABCO spray field. SCDHEC sampled this well for VOCs andmetals. No VOC contamination was detected. Cadmium was detected at 0.0001 milligrams perliter (mg/L) which is below ATSDR comparison values.
Two air monitoring stations were located in the Roebuck area to monitor emissions from thefacility. The 'Cromer' station was located north of the facility in a residential area that was notexpected to be in the prevailing wind direction. The 'Pecan' station was located east-northeast ofthe facility at the point of maximum concentration as predicted by an air modeling program (15). Both 24 hour and episodic samples were taken. Please refer to Figure 5, Appendix A, for thelocation of the air monitoring stations with respect to the facility.
Sampling began in Roebuck at the Cromer air monitoring location on August 3, 1986, and at thePecan air monitoring location on July 14, 1987. The samplers included a modified high volumeair sampler to collect particulates and metals, and a high volume organic sampler. Nonmethaneorganic compounds were continuously analyzed (15). On December 12, 1989, a sampler wasinstalled at the Cromer air monitoring location that could be activated by a key switch by the arearesidents as well as various state officials.
Air monitoring data from the 'Parklane' station was also compiled. The Parklane station islocated in Columbia which is over 100 miles away from Roebuck. South Carolina used thisstation to assess the background of areas that are not influenced by industry, but have a mix ofresidential and vehicular traffic (15). For the purpose of this public health assessment, ATSDRdoes not consider this data to indicate background conditions in Roebuck and has included thisdata for reference only.
Air monitoring data exist from 1986 to 1998. Due to community concern that the prevalence ofcancer cases is related to emissions from the facility in the past, off-site air data from 1986 to1989 was compiled for review. Of the compounds detected, naphthalene, nickel, and arsenicexceeded ATSDR comparison values. Please refer to Table 5 and Table 6, Appendix B, for theair monitoring results.
The surface water bodies closest to the Laidlaw facility are an unnamed tributary, the StillmanBranch, and the North Tyger River. Please refer to Figure 4, Appendix A, for the location ofsurface water bodies with respect to the facility. No surface water samples have been taken fromthe Stillman Branch. Even though no water quality data has been collected, the RCRA FacilityInvestigation report concluded that the unnamed tributary and the Stillman Branch are notbelieved to have been impacted by the facility (4). Monitoring well data in that area have notindicated a release of salt plume contaminants through groundwater migration and surface soildata has not indicated a release of contaminants through surface water runoff (4). Surface waterdata from the North Tyger River collected and reviewed for the RCRA Facility Investigationfrom 1978 to 1987 indicated the water quality of the river is good (4).
In March of 1997, a resident requested a surface water sample be collected from a stream on hisproperty that received runoff from the former ABCO Spray field. The resident was concernedthat ABCO's former spray field could have contaminated the surface water. SCDHEC sampledthe surface water for VOCs and metals. No VOC or metal contamination was detected.
In March of 1997, a resident requested a sediment sample be collected from a stream on hisproperty that received runoff from the former ABCO Spray field. The resident was concernedthat ABCO's former spray field could have contaminated the sediment. SCDHEC sampled thesediment for VOCs and metals. No VOC contamination was detected. The metals arsenic,barium, chromium, and lead were detected at levels of 55 milligrams per kilogram (mg/kg), 54mg/kg, 13 mg/kg, and 10 mg/kg, respectively. The level of arsenic in sediment exceeded boththe chronic child Environmental Media Evaluation Guide (EMEG) and the Cancer RiskEvaluation Guide (CREG) comparison values. However, the latter values are specific for soil(not sediment), and the assumptions on which they are based, (i.e., ingestion of 100-200 mg ofsoil per day for life), would not apply to the sediment in question (or, indeed, to most soils). Therefore, the metals detected in sediments do not pose a public health hazard.
In preparing public health assessments, ATSDR relies on the environmental data provided in thereferenced documents. ATSDR staff assumes that adequate quality assurance and quality controlmeasures were followed regarding chain-of-custody, laboratory procedures, and data reporting. The analyses, conclusions, and recommendations in public health assessments are valid only ifthe referenced documents are complete and reliable.
Of note, information regarding chain-of-custody and laboratory procedures for the on-site surfacewater data was not available for review.
Laidlaw is completely fenced and access is strictly controlled. Physical and other hazardsassociated with the operation of a liquid hazardous waste incineration facility existed. On thesite visit, bulging drums in container storage area were noted. Additionally, ATSDR receivedseveral reports documenting various spills, leaks, tank explosions, and other incidents.
To determine whether nearby residents are exposed to contamination migrating from the site,ATSDR evaluates the environmental and human components that lead to human exposure. Anexposure pathway contains the following five elements: a source of contamination, transportthrough an environmental medium, a point of exposure, a route of human exposure, and anexposed population. A completed exposure pathway exists if all five elements are present. Forcompleted exposure pathways, exposure to a contaminant has occurred, is occurring, or willoccur. Please refer to Table 1, Appendix B, for information on completed exposure pathways atthe site. A potential exposure pathway exists if one of the five elements is missing but couldexist. For potential exposure pathways, exposure to a contaminant could have occurred, could beoccurring, or could occur in the future. Please refer to Table 2, Appendix B, for information onpotential exposure pathways at the site. An exposure pathway can be eliminated if at least one of the elements is missing and will never be present.
A past completed exposure pathway existed from contamination of the ambient air. There was ahistory of odor complaints from residents in the areas surrounding the facility. Most of the odorcomplaints appeared to correlate with times at the facility when tank spills and overflowsoccurred. This would suggest that small, point source, releases were responsible for off-siteodors and not emissions from the operating incinerator. A review of off-site air monitoring datafrom 1986 to 1989 indicated naphthalene, nickel, and arsenic exceeded ATSDR comparisonvalues (Table 5 and Table 6, Appendix B).
Points of exposure included on-site workers and residents who lived and worked in the area. Approximately 50 individuals worked on-site and 1,250 individuals live within one mile of thefacility. Routes of exposure included inhalation of the ambient air in the surrounding residential area.
A future potential exposure pathway exists from contamination of the groundwater. Groundwater beneath the site is contaminated. Corrective measures have been instituted toreduce the level of contaminants present in the groundwater. The selected option for the saltplume includes a monitoring program to evaluate the degradation of contaminants throughdispersion and biodegradation. Compliance points are established at down gradient wells toensure that the plume will not pose a threat to human health as it degrades (8). The selectedoption for the organic plume includes the installation of groundwater recovery wells which willdischarge contaminated groundwater to an on-site lift station which will then pump the flows viaa force main to the Spartanburg Sanitary Sewer District (SSSD) publicly-owned treatment works(8). The facility received EPA approval for the selected choices in June 1995 and is currently inthe implementation stage.
Most of the area is provided drinking water from the Woodruff-Roebuck Water District. Agroundwater well inventory was conducted by the South Carolina Water Resources Commission(SCWRC) for the Roebuck area (4). This inventory found no groundwater wells locatedimmediately down gradient of the facility; however, fifteen private wells were identified in theRoebuck area. Of these 15 wells, 12 were verified not to be within areas that may be potentiallyimpacted by the facility (4). The locations of the other three wells are not known, but expectedto be east or southeast of the site, whereas the groundwater flow is west-southwest (4). Additionally, these wells are very deep (ranging from 155 to 400 feet) and located in the bedrockaquifer. As previously noted, only wells installed after 1986 would be included in this wellinventory. Before 1986, well drillers were not required to report the new wells they installed soadditional private wells that were installed before 1986 may exist in the area. However,additional efforts made by ATSDR staff have not identified any private drinking water wells thatcurrently draw from the contamination plume or are likely to in the foreseeable future.
Another well survey located wells within a three mile radius from to the site (4). The nearestwells, located 2,100 feet and 2,500 feet south of the site, are located on a hill. Contaminantmigration in groundwater from the Laidlaw site should not impact these wells as groundwaterflow in this area appears to flow to the north towards the facility(4). In the future, exposures togroundwater could occur if local residents install private drinking water wells in the area ofgroundwater contamination or the contaminant plume migrates to existing private wells. Routesof potential future exposure would include ingestion, inhalation, and direct skin contact. Currently, the installation of private wells in the area of groundwater contamination is consideredunlikely. ATSDR has recommended institutional controls restricting the installation of newwater supply wells in the area. Further, groundwater remediation should slow or preventadvancement of the plume and reduce the contaminant concentrations below levels of healthconcern.
A past potential exposure pathway existed for workers from contamination of the on-site pondsused during ABCO's ownership of the facility. Limited on-site surface water data indicatearsenic, chromium, copper, lead, nickel, zinc, and phenols exceeded ATSDR comparison values. Please refer to Table 9, Appendix B. Workers may have been exposed to contaminated pondwater during normal job activities. The routes of potential exposure could have included directskin contact and incidental ingestion.
In the past, during ABCO's ownership of the facility, on-site contaminated pond water may havemigrated off-site to the unnamed tributary. Some area residents use the unnamed tributary as awater source for their livestock. Also, the potential exists that children play in this tributary. The routes of potential exposure include direct skin contact and incidental ingestion. Nosampling data are available for the unnamed tributary during the time period when ABCO wasoperating the ponds; therefore, ATSDR is not able to comment on past exposures to surfacewater in this unnamed tributary. Currently, the ponds have been remediated and the spray field isno longer used; therefore, no current surface water discharges are expected. Further, a recent off-site surface water sample did not detect any VOCs or metals. Exposure to this surface water isnot expected to result in adverse health effects now or in the future.
A past, current and future potential exposure pathway exists from contamination of off-sitesediment. The level of arsenic detected in sediment from a creek located south of the old ABCOspray field exceeded both the chronic child environmental media evaluation guide (EMEG) andthe cancer risk evaluation guide (CREG) comparison values. Contaminated pond water mayhave migrated to the unnamed tributary in the past. A potential exists for children to play in thistributary. The routes of potential exposure could include direct skin contact and incidentalingestion of the sediment.
A past potential exposure pathway exists from contamination of on-site shallow and deep soil. Facility workers could have been exposed to contaminants in the shallow soil during normalwork activities before remediation took place. Workers could have been exposed tocontaminants in deep soil during excavation and remedial activities. Routes of potentialexposure would include direct skin contact.
This section addresses the likelihood that exposure to contaminants at the maximumconcentrations detected would result in adverse health effects. While the relative toxicity of achemical is important, the response of the human body to a chemical exposure is determined byseveral additional factors, including the concentration (how much); the duration of exposure(how long); and the route of exposure (breathing, eating, drinking, or skin contact). Lifestylefactors (i.e., occupation and personal habits) have a major impact on the likelihood, magnitude,and duration of exposure. Individual characteristics such as age, sex, nutritional status, overallhealth, and genetic constitution affect how a human body absorbs, distributes, metabolizes, andeliminates a contaminant. A unique combination of all these factors will determine theindividual's physiological response to a chemical contaminant and any adverse health effects theindividual may suffer as a result of the chemical exposure.
The Agency for Toxic Substances and Disease Registry (ATSDR) has determined levels ofchemicals that can reasonably (and conservatively) be regarded as harmless, based on thescientific data the agency has collected in its toxicological profiles. The resulting comparisonvalues and health guidelines, which include ample safety factors to ensure protection of sensitivepopulations, are used to screen contaminant concentrations at a site and to select substances (so-called "chemicals of concern") that warrant closer scrutiny by agency health assessors andtoxicologists. When an ATSDR comparison value does not exist for a site-related compound (asis often the case with airborne contaminants), relevant values from the Environmental ProtectionAgency (EPA) or other agencies are used, instead. Most of the comparison values used in Tables5 and 6, Appendix B, for example, are Risk-Based Concentrations (RBC) from EPA Region III,and all are based on the assumption of lifetime exposure. EPA and ATSDR comparison valuesare derived in much the same way and all include substantial safety margins. Please refer toAppendix C for a more complete description of ATSDR's comparison values, health guidelines,and other values ATSDR uses to screen site contaminants.
It is a point of key importance that ATSDR's (and EPA's) comparison values and healthguidelines represent conservative levels of safety and not thresholds of toxicity. Thus, althoughconcentrations at or below a comparison value may reasonably be considered safe, it does notautomatically follow that any concentration above a comparison value will necessarily producetoxic effects. To the contrary, ATSDR's (and EPA's) comparison values are intentionallydesigned to be much lower, usually by orders of magnitude, than the corresponding no-effectlevels (or lowest-effect levels) determined in laboratory studies. ATSDR uses comparison values(regardless of source) solely for the purpose of screening individual contaminants. In this highlyconservative procedure, ATSDR considers that a compound warrants further evaluation if thehighest single recorded concentration of that contaminant in the medium in question exceeds thatcompound's lowest available comparison value (e.g., CREGs or other chronic exposure values)for the most sensitive, potentially exposed individuals (e.g., children or pica children). Thishighly conservative process results in the selection of many contaminants as "chemicals ofconcern" that will not, upon closer scrutiny, be judged to pose any hazard to human health. However, ATSDR judges it prudent to use a screen that "lets through" many harmlesscontaminants rather than one that overlooks even a single potential hazard to public health. Eventhose contaminants of concern that are ultimately labeled in the toxicological evaluation aspotential public health hazards are so identified solely on the basis of the maximumconcentration detected. The reader should keep in mind the protectiveness of this approach whenconsidering the potential health implications of ATSDR's toxicological evaluations.
Since a contaminant must first enter the body before it can produce any effect, adverse orotherwise, on the body, this toxicological evaluation focuses primarily on completed pathways ofexposure, i.e., contaminants in media to which people are known, or are reasonably expected, tohave been exposed, such as water that may be used for drinking water and air in the breathingzone. Air represents the most important pathway of exposure at Roebuck.
Method of Evaluation:
Data from the 1986-1989 sampling suggest that off-site air at Roebuck during that period wasessentially quite "clean". Because ATSDR has relatively few comparison values for chemicals inair, the majority (31 of 54) of the comparison values used in Table 5, Appendix B, were Risk-Based Concentrations (RBC) listed by EPA Region III. These RBC were generally 10 to 10,000times higher than the concentrations reported in Table 5, Appendix B. For indene and nonane, itwas necessary to use the 8-hr Threshold Limit Values(TLVs) (37) which were orders ofmagnitude higher than the maximum concentrations of these compounds (Table 5, Appendix B).
Contaminants of Concern without Comparison Values (CVs):
For the remaining 22 compounds, no published comparison values were available and alternateapproaches had to be taken, using chemical-specific data available in the Hazardous SubstancesDatabase (HSDB) and other sources. The TLV of octane was used as a surrogate for octanal (thealdehyde of octane), which one might expect to be somewhat more irritating. However, themargin of safety between the highest concentration of octanal and the TLV of octane was over200,000, suggesting that the maximum concentration of octanal was not likely to be acontaminant of concern. A similar comparison was made between the maximum concentration ofnonanal and the TLV for nonane. Based on the levels reported in Table 5, Appendix B, the 24-hrinhalation dose of benzothiazole, an antimicrobial flavoring agent used in food, would be lessthan 1/4,000,000 the LD50 of 95,000 micrograms per kilogram (ug/kg) in mice (38).
In some cases (e.g., 2-ethyl hexanoic acid and 4-ethyl benzaldehyde), an ad hoc comparisonvalue was estimated by dividing a known, minimally-toxic effect-level by 1,000 or byextrapolating from several closely related compounds. In other cases, it was possible to determine qualitatively that the chemical of interest (e.g., 2-nitrophenol) was less toxic than arelated substance (4-nitrophenol) with a known comparison value that was well in excess of thecorresponding air concentration in Table 5, Appendix B. The latter approach was especiallyuseful with compounds in a homologous series. For example, nonane, decane, undecane,dodecane, tetradecane, hexadecane, octadecane, eicosane, docosane, and tetracosane are C9-C24alkanes (i.e., saturated straight-chained hydrocarbons 9 to 24 carbons long) of low toxicityrelative to the C-6 compound n-Hexane. Since the toxicity of saturated hydrocarbons tends todecrease with increasing chain-length, all of these alkanes are expected to be less toxic thanhexane. And since the concentrations of all of these C9-C24 alkanes were lower than the RfC forhexane (200 ug/m3) by more than a factor of ten, all of these concentrations would be considerednon-toxic.
In the case of 2-methyl naphthalene, a judgement had to be based on the fact that 1) no effects inhumans have been reported for this compound and 2) the concentrations listed on Table 5,Appendix B, do not exceed the national average of 0.086 ug/m3 (39). Similarly, the levels ofphenanthrene in air (0.030-0.035 ug/m3) in the vicinity of the Laidlaw facility (Table 5,Appendix B) were within those (0.014-0.140 ug/m3) measured at Columbia, South Carolina(40). Based on the maximum level detected at Cromer, the resulting inhalation dose (ca. 0.7ug/kg/day) would be only one millionth the LD50 of 700 mg/kg for phenanthrene in mice (40). There is no evidence to suggest that this noncarcinogenic polycyclic aromatic hydrocarbon(PAH) will cause any adverse effects in humans at such low levels of exposure.
Finally, some of the "contaminants" were natural volatiles found in the essential oils of certainplants. For example, alpha- and beta-pinene produce the fragrance of pine trees and are majorcomponents of turpentine. Isopropyl toluene (better known as p-cymene) is a natural componentof the cumin on your spice rack. Although, in liquid form, it can be an irritant, the vapor is non-irritating (41). Inhalation of pinenes, on the other hand, can cause some discomfort, but only atlevels tens of thousands of times higher than those listed in Table 5, Appendix B (42). Thelevels detected downwind of the facility were consistent with background levels in forestedareas.
In summary, the maximum concentrations of all of the atmospheric contaminants listed in Tables 5 and 6, Appendix B, were far below levels that could produce adverse effects, and only ahandful (naphthalene, arsenic and nickel) exceeded any comparison values at all. These threecompounds are discussed in more detail below, along with a few other chemicals[pentachlorophenol (PCP), bis(2-ethylhexyl)phthalate, and chrysene] that have been classified ascarcinogens.
High doses of naphthalene, a non-carcinogenic polycyclic aromatic hydrocarbon (PAH), cancause hemolytic anemia, especially in children with a genetic deficiency of the enzyme glucose-6-phosphate dehydrogenase (G-6-PD) (43). However, the levels of naphthalene detected in off-site ambient air (Table 5, Appendix B) are too low to produce any adverse health effects.
The maximum 24-hr concentration of naphthalene at the Cromer station (2.543 ug/m3) did notexceed ATSDR's chronic EMEG of 2 parts per billion (i.e., 10.5 ug/m3). Therefore, lifelongexposure at this level would be considered safe. The maximum episodic concentration (181.8ug/m3) of naphthalene did exceed ATSDR's chronic EMEG, but only marginally exceeded theRBC of 150 ug/m3. However, EPA's RBC are also based on chronic exposure. (Note: It is notunusual for different agencies to produce different comparison values for the same chemical andduration of exposure. Since health-based comparison values are estimates of levels of safety,rather than thresholds of effect, precision is not an issue. In fact, there may be as many differentofficially "safe" levels as there are differently conservative assumptions.) Neither ATSDR norEPA have any comparison values for acute inhalation exposure to naphthalene, but NIOSH (theNational Institute for Occupational Safety and Health) lists a short-term exposure limit foroccupational exposure to naphthalene (15 ppm or 79,000 ug/m3) which is over 400 times higherthan the maximum episodic exposure at Cromer. Therefore, neither chronic nor acute adversehealth effects would be expected to result from exposure to naphthalene in air, at the levelsrecorded in Table 5, Appendix B.
PCP, Bis(2-ethylhexyl)phthalate, and Chrysene:
Of all the airborne organic contaminants identified during off-site air monitoring from 1986 to1989 (Table 5, Appendix B), none were known human carcinogens, and only three have causedcancer in laboratory animals. Very high oral doses of PCP, bis(2-ethylhexyl)phthalate (DEHP),and chrysene have all caused significantly elevated incidences of liver cancers in mice (44-46).However, there is, as yet, no evidence that PCP, DEHP, or chrysene cause cancer of any kind inhumans. In addition, the maximum concentrations of these three compounds in air in Roebuck(Table 5, Appendix B) were all below their corresponding "safe" levels (as estimated from theanimal data by EPA Region III) by factors of 5, 11, and 200, respectively. Therefore, no adversehealth effects would be associated with the inhalation exposure to these chemicals at Roebuck.
Of all the metals detected during off-site air sampling between 1986 and 1989 (Table 6,Appendix B), only arsenic and nickel are known to be carcinogenic in humans (47). All othermetals were non-carcinogenic and were present at concentrations below comparison values. Themaximum concentration of arsenic in air at Roebuck was 0.00298 ug/m3. Although thisconcentration exceeds ATSDR's CREG of 0.0002 ug/m3, the latter comparison value is based onstandard assumptions that are not entirely applicable in the case of arsenic. First, it is assumedthat there is no threshold for chemically-induced carcinogenicity, even though the evidencestrongly suggests that inorganic arsenic is a non-mutagenic carcinogen with a probable thresholdof 200-400 ug/day (48, 49). Second, cancer-based comparison values are based on theassumption of lifetime exposure. However, the levels reported in Table 6, Appendix B, representmaximum levels rather than lifetime average exposures. Furthermore, since the first incineratorat Roebuck did not go "on line" until March 1978, the longest that anyone living in Roebuck canhave been exposed to these incinerator emissions is about 20 years. Based on the numerical riskestimates alone, a concentration of 0.00298 ug arsenic/m3 air, the maximum concentrationdetected at the Cromer station, would correspond to an increased cancer "risk" of 15 per millionor 0.015 per thousand over a lifetime of exposure at this level. Since the population within onemile of the incinerator is about 1,249, it follows that not even a single "excess" case of lungcancer would be expected to occur in an exposed population this size after a lifetime of exposureto the maximum concentration of arsenic detected in air at Roebuck.
It must be emphasized, however, that quantitative cancer risk assessments were never intended tobe used for the prediction of actual human health effects. Originally, the methodology wasdeveloped solely as a convenient tool that would allow the risk manager to numerically rank sitesfor cleanup. In fact, it is explicitly stated in EPA's 1986 Cancer Risk Assessment Guidelinesthat "The risk model used by EPA....does not necessarily give a realistic prediction of therisk.....The true value of the risk is unknown and may be as low as zero" (50).
Nickel refinery dust is a known human respiratory carcinogen. It is a mixture of many differentnickel compounds (mostly nickel subsulfide), and it is not certain which is the carcinogenicspecies (51). The respiratory cancers observed in studies of occupationally-exposed workerswere related primarily to exposure to more than 1,000 ug/m3 of soluble nickel compounds andmore than 10,000 ug/m3 of less soluble nickel compounds (52). By comparison, the maximumconcentrations of airborne nickel (species unspecified) detected at the Cromer (0.029 ug/m3) andPecan (0.025 ug/m3) sampling stations were 34,000 to 400,000 times lower, being within thenormal range of concentrations (0.003 - 0.03 ug/m3) in urban areas without a metallurgy industry(53), and below the maximum concentration at the "background" Parklane station (0.064 ug/m3,Table 6, Appendix B). Thus, even if these levels were representative of average, chronicexposures rather than maximum exposures, they would not be expected to produce any adversehealth effects (including cancer) above "background" levels of effect because, logically, onewould not expect a lower-than-background exposure to produce a higher-than-background effect.
The fact that the maximum concentrations at all three stations were higher than ATSDR's CREGof 0.004 ug nickel subsulfide/m3 says nothing about the "true" carcinogenicity, if any, of theselevels of nickel in air. As stated above in the section on arsenic, the levels recorded in Table 6,Appendix B, represent maximum values, only. As such, they and similar values occur onlyinfrequently and, therefore, are not comparable to the lifetime exposures on which CREGs arebased. If one knew the actual frequency with which each different concentration occurred, thenone could mathematically average the resulting dose over the entire period of exposure andcalculate a corresponding value for the associated increase in cancer "risk." However, as statedpreviously (see section on arsenic), such an exercise would be uninformative from a public healthstandpoint because "the true risk is unknown and may be as low as zero" (50). More relevant tothe potential for human health effects is the fact that the maximum recorded concentrations ofairborne nickel (and therefore all other recorded concentrations, as well) at the Cromer, Pecan,and Parklane stations were below ATSDR's EMEG of 0.1 ug/m3 for intermediate durationexposures to nickel and the RBC of 73 ug/m3 for chronic exposure to "nickel and compounds".
A shallow plume of groundwater contamination extends to the west/southwest of the incinerationfacility. The maximum concentrations of many of the substances detected in this groundwaterexceeded legally-enforceable EPA maximum contaminant levels (MCLs), secondary MCLsand/or other comparison values. Those substances included: benzene, bromodichloromethane,carbon tetrachloride, chloroform, chloromethylmethyl ether, 1,2-dichloroethane or ethylenedichloride, 1,1-dichloroethene or vinylidene dichloride, methylene chloride, tetrachloroethene orPCE, trichloroethene or TCE, 1,1,1-trichloroethane, vinyl chloride, arsenic, barium, cadmium,chromium, lead and nickel. At a consumption rate of 2 liters of water per day, the maximumdetected concentration of iron [163 ppm, Table 4, Appendix B] in this groundwater would evenexceed minimally toxic levels in humans.
However, where there is no exposure, there can be no exposure-related health effects, regardlessof the level of environmental contamination. As far as ATSDR has been able to determine, noone is using this contaminated groundwater as a source of drinking water, and no groundwaterwells (other than monitoring wells) are located down gradient of the facility. Measures should betaken to assure that this remains the case, at least until current remediation efforts are effectivelycompleted, because the levels of contamination indicated by the data presented in Tables 3 and 4,Appendix B, would be hazardous to the health of persons who drank this water. [Note: It isentirely possible that the low esthetic quality of this water would discourage anyone from drinking it, even if the opportunity presented itself.]
ABCO operated several ponds during their ownership of the incineration facility. The maximumtime frame the ponds that were sampled may have been in operation is 10 years (1978 until1988). It is not possible to say how representative the monitoring results of 1980-81 were ofconditions during the entire 10-year period. However, no significant human exposure to thispond water is likely to have occurred, because: (1) this pond was not used as a drinking watersupply, and (2) the levels of manganese and iron (10 and 30 times their respective secondaryMCLs) were such that the resulting unaesthetic qualities of the water should have discouragedeven occasional ingestion. Thus, CREGs and chronic EMEGs/RMEGs (especially those forchildren) are not the most appropriate comparison values to use with this potential source ofexposure. It is unlikely that the occasional, brief exposure to this pond water would haverepresented a toxic hazard to humans.
Since Laidlaw is completely fenced and access is strictly controlled, only comparison values foradults are presented in Tables 7 and 8, Appendix B. The most relevant data (from a healthstandpoint) in both tables is that in the second column (0-2 feet), because worker exposure will,for the most part, be limited to contaminants in surface soil. All of the chemicals listed in Table7, Appendix B, were present at levels that were well below available comparison values based onnon-cancer effects. (Note: While no CV was available for inorganic lead in soil, the maximumdetected concentration on-site is below the dose-equivalent of both EPA's 15 ppb action level indrinking water and the National Ambient Air Quality Standard of 1.5 ug/m3.)
In shallow soil samples (0-2 feet), only the concentrations of 1,1,2,2-tetrachloroethane (22 ppm),1,2-Dichloroethane (80 ppm) and, possibly, arsenic (<5 ppm) exceeded their respective CREGsof 4, 8, and 0.5 ppm. However, even if on-site excavation occurred at this site, it would notresult in chronic life-long exposures such as those on which comparison values for cancer (e.g.,CREGs) are based. Occupational cancers are typically associated with inhalation exposures,rather than soil ingestion. Therefore, considering the limited access to these mostly subsurfacesoils, the low levels of the contaminants present, the low carcinogenic potency of the chemicalsin question, and the extreme conservatism of CREGs and similar values based on the modelassumption of zero-threshold, ATSDR considers that these soils are not likely to pose anydetectable hazard, carcinogenic or otherwise, to public health.
Interestingly, the concentration of 1,1,2,2-tetrachloroethane in on-site soil is lower than anothercancer-based comparison value (EPA Region III's RBC for industrial soil). This is not unusualand is by no means indicative of a discrepancy of any sort. Health-based comparison values areestimates of levels of safety, and not thresholds of effect, and there can be as many different safelevels as there are differently conservative assumptions.
Arsenic levels of as much as 55 milligrams per kilogram (mg/kg or ppm) were detected in off-site sediment from a creek located south of the former ABCO spray field. It is unlikely thatchildren (or adults) will actually consume significant amounts of this (or any other) sediment. ATSDR has no comparison values for sediment for this very reason. ATSDR does, however,have comparison values for soil which are based on default rates of soil ingestion for picachildren (5,000 mg/day), non-geophagic children (200 mg/day), and adults (100 mg/day). ATSDR's only comparison values for arsenic in soil are its chronic pica child, child, and adultEMEGs of 0.6, 20, and 200 mg/kg, respectively. The arsenic level in the sediment of concernexceeds the first two comparison values, but not the third. However, since 1) default rates of soilingestion do not apply to sediment, and 2) exposures will not be chronic (if, indeed, they occur atall), use of these comparison values would greatly over-estimate any health risks that thesecontaminated sediments might pose to the public. A pica child would have to eat 55 mg of thissediment every day in order to get the same arsenic dose that he/she would get by eating 5,000mg of soil (the default ingestion rate) containing 0.6 ppm arsenic (ATSDR's lowest comparisonvalue for arsenic in soil). As unlikely as this exposure scenario is, it still would not be expectedto result in any adverse health effects related to the resulting arsenic intake.
In defining the health outcome of a population living near a contaminated site, the toxicity ofchemicals present must be evaluated, a plausible completed pathway of exposure defined, and thecommunity's health concerns addressed. ATSDR has reviewed the environmental contaminantson- and off-site at the Laidlaw incinerator site. Completed and potential pathways in whichresidents may be exposed to these contaminants were identified. In response to Roebuckresidents' concerns about a perceived increase in the incidence of cancer in the communityrelated to environmental exposures in the mid 1980's to hazardous chemicals at the hazardouswaste incinerator, the South Carolina Department of Health and Environmental Control(SCDHEC) analyzed cancer incidence and mortality data collected for the 10 year period from1986 -1995. Particular health concerns expressed by the community include breast, cervical,lung, and prostate cancer. ATSDR reviewed both the "Cancer Cluster Study of the Town ofRoebuck, South Carolina" final report prepared June 1, 1997 by the South Carolina Departmentof Health and Environmental Control, Division of Cancer Prevention and Control, and the "Executive Summary of the final report of the American Cancer Society's (ACS) RoebuckCancer Cluster Investigation," March 12, 1997.
Cooperative efforts by the Roebuck Community Advisory group and the SCDHEC, helpeddefine the 1.5 mile radius from the town center as the exposed area. Please refer to Figure 3,Appendix A, for a map of the 1.5 mile radius. Cooperative efforts also helped define 'residents'as members living in Roebuck for one year and a 'case' as anyone living in Roebuck or who hadlived in Roebuck and been diagnosed with cancer from January 1, 1986 to December 31, 1995. Cases were obtained by voluntary reporting, a review of medical records from state and regionalhospitals, a review of physicians records, and a review of medical records from participatingGeorgia and North Carolina hospitals. All cases were confirmed for primary site and date ofdiagnosis by contacting the attending physician listed on the form.
Cases diagnosed and confirmed during this 10 year period were defined within the study by useof Geographical Information Systems (GIS) zip code address matching. Mortality data wasobtained through the Office of Vital Records. Using GIS, the total population in the 1.5 milearea was estimated at 2,737, based on the 1990 US census data. Standard questions regarding thetype of cancer, length of residence, date of diagnosis, death, and occupation were included in thesurvey questionnaire, but questions regarding preventative health activities, habits, diet, smoking,and other risk factors were not included.
The Standard Incidence Ratio (SIR), a method used to analyze cancer incidence in a population,was calculated by dividing the observed number of cases in the population of Roebuck beingstudied by an expected number of cancer cases for the population. The expected number isdetermined by using incidence rates from a comparison population where the cancer rates wouldbe stable and represent the normal number expected in a population of that size. In this study,age-specific rate of disease were obtained from the 1987 - 1991 National Cancer InstituteSurveillance, Epidemiology, and End Results (NCI SEER) data incidence rates and multiplied bythe age specific populations in the Roebuck area to determine the expected number of cases forthe Roebuck population. An SIR value of 1.0 or less than 1.0, assumes a null hypothesis; that is,the cancer incidence in the two populations are the same or there are fewer cancer cases in thestudy population than expected. In other words, no increase in cancer is observed in thepopulation. Conversely, a ratio higher than 1.0, shows that there might be more cases in thecommunity than expected.
If the SIR is greater than 1.0, it is tested for significance or whether the observed number of casesis truly elevated or possibly due to chance. A chi-square value is used as a statistical tool toevaluate the probability that the standard incidence ratio for the type of cancer represents a trueindication of an increase in the disease. Therefore, while the SIR may be greater than 1.0, it maynot be a valid increase due to some other factor or factors influencing the results.
ATSDR reviewed the June 1, 1997 final report which included a summary table of the observedRoebuck cases, SIR, and chi-square values. Data on the age, race, sex and other data was notavailable for review. No difference in the number of cases for all types (all sites) of cancersobserved was found in the Roebuck population compared to the expected number of cases. ASIR of 1.02 was not found to be statistically significant. No conclusive evidence for a cancercluster in time and/or space was found to exist; however, the study report recommends continuedsurveillance for new cases in the future. This is a valid recommendation since some cancersdevelop more than 10 years after exposure.
In this final report, only the incidence of cancer of the Lung and Bronchus observed in Roebuckwas determined to be slightly elevated (25 cases versus 16 expected) for this population. Theanalysis showed that the 25 cases were evenly distributed over the 10 year period, except for 7cases observed in 1995 where the age of the person was 65 years or older. It is more likely thatan increase in cancer would be found in this age group. In addition, of the 25 cases observed, 20cases or 85% included smoking as a risk factor. According to the American Cancer Society(1997), smokers are approximately 10 times more likely to develop lung cancer or have a 900%increased risk of lung cancer than nonsmokers. While smoking is the major risk factor fordeveloping lung cancer, other risk factors do exist including exposure to environmentalcontaminants. However, ATSDR's toxicological review of air data obtained for the Laidlawincinerator site concludes that the contaminants at the concentrations identified would not likelycontribute to an increased risk for lung cancer.
A follow-up study to address the slight increase in the incidence of lung cancer cases in Roebuckwas conducted in 1996 by the American Cancer Society and the University of South CarolinaDepartment of Epidemiology and Biostatistics. The study evaluated cases of cancer diagnosedbetween 1986 - 1995 for risk factors for cancer including smoking history, family history ofcancer, past cancer screening history, and occupation. Of the 15 lung cancer cases obtained fromthe Spartanburg Regional Medical Center, 93.3% revealed a history of smoking. In this study,the incidence of all types of cancers in Roebuck was compared to expected rates of cancer overthe same 10 year period in other communities in Spartanburg County (Cowpens, Inman,Landrum, Lyman, Spartanburg City, and Woodruff). No excess in cancer was found in Roebuckcompared to the other surrounding communities when the population within the entire zip codearea of Roebuck was used for the analysis.
This study concluded that the interaction of smoking and environmental pollutants cannot beruled out for a potential increase in some types of cancers. Smoking is prevalent in thepopulation and 93.3% of the lung cancer cases observed during this time period were smokers. As stated previously, ATSDR's toxicological review of air data obtained for the Laidlaw siteconcludes that the contaminants at the concentrations identified would not likely contribute to anincreased risk for lung cancer. The study suggests and ATSDR concurs, that follow-upmonitoring for 3 to 5 years, comprehensive screening for cancer, and education of cancer riskfactors including a smoking cessation program would benefit the Roebuck citizens and thesurrounding communities of Spartanburg County.
ATSDR staff met with the petitioner and several concerned residents on July 10, 1996. This group of concerned residents make up the Roebuck Community Advisory Group to the SCDHEC Cancer Study. In this section, ATSDR has responded to each community concern as expressed to ATSDR staff during the community meeting.
|Community Concern # 1:||increased incidence of cancer including brain, colon, rectum, prostate, lung, ovary, breast, liver, stomach, kidney, and throat|
The South Carolina Department of Health and Environmental Control (SCDHEC) began a cancer cluster study in March of 1996 to investigate a perceived excess of cancer in Roebuck, South Carolina. SCDHEC found a slight, but statistically significant, excess of lung cancer, only. Twenty five cases were observed, while only 16 were expected. No other type of cancer was in excess, nor did the overall number of cancer cases observed over the 10-year study period exceed the number expected, based on data on the nationwide incidence of cancer. The American Cancer Society (ACS) funded an independent case review of these data. While the SCDHEC investigators and the ACS-funded case reviewer came to the conclusion that the slight, but statistically-significant, increase in lung cancer incidence identified at Roebuck, South Carolina, is most likely attributable to smoking, the interaction of smoking and environmental pollutants could not be ruled out. However, ATSDR concluded that the contaminants present at the concentrations reported in Tables 5 and 6, Appendix B, are not likely to result in an increased cancer risk. ATSDR's conclusion is based on a review of all the relevant toxicological information and the following specific considerations.
Airborne Contaminants (organics): Of all the airborne organic contaminants identified duringoff-site air monitoring from 1986 to 1989 (Table 5, Appendix B), none were known humancarcinogens, and only three have caused cancer in laboratory animals. High oral doses of PCP, Bis(2-ethylhexyl)phthalate, and chrysene have all caused significantly elevated incidences ofliver cancers in mice. However, there is no evidence that PCP, DEHP, or chrysene causes cancerof any kind in humans. Furthermore, the maximum concentrations of these three compounds inair at Roebuck (Table 5, Appendix B) were all below their corresponding "safe" levels (asestimated from the animal data by EPA Region III) by factors of 5, 11, and 200, respectively.
Airborne Contaminants (metals): Of all the metals detected during off-site sampling between1986 and 1989 (Table 6, Appendix B), only arsenic is classified as a known human carcinogen. All other metals were non-carcinogenic or were present at concentrations below comparisonvalues. The maximum concentration of arsenic in air at Roebuck was 0.00298 ug/m3. Althoughthis concentration exceeds ATSDR's CREG of 0.0002 ug/m3, the latter comparison value isbased on standard assumptions that are not entirely applicable to arsenic. For example, it isassumed that there is no threshold for chemically-induced carcinogenicity. However, availableevidence strongly suggests that inorganic arsenic is a non-mutagenic carcinogen with a probablethreshold of 200-400 ug/day. Cancer-based comparison values are also based on the assumptionof lifetime exposure. Since the first incinerator at Roebuck did not go "on line" until March1978, no one living in Roebuck has been exposed to incinerator emissions for more than 20 yearsat a maximum.
"Practical" Thresholds: Even if one interprets quantitative "risk" estimates levels literally(which is neither warranted nor recommended), then the size of the potentially affectedpopulation at Roebuck would automatically impose a practical threshold on chemicalcarcinogenicity. For example, based on a cancer slope factor of 0.0043/ug/m3, a concentrationof 0.00298 ug arsenic/m3 of air (Table 6, Appendix B) would correspond to an increased "risk"of only 15 per million or 0.015 per thousand. Since the population within 1 mile of theincinerator is only about 1,249, it follows that not even one "excess" case of lung cancer wouldbe expected as a result of a lifetime of exposure to airborne arsenic at Roebuck. It must beemphasized, however, that quantitative cancer risk assessments were initially developed only as aconvenient means of numerically ranking sites for cleanup; they were never intended to be usedto actually predict health outcomes. As EPA's 1986 Cancer Risk Assessment Guidelinesexplicitly states, "The true value of the risk is unknown and may be as low as zero" (50).
In the SCDHEC cancer study that identified excess lung cancer at Roebuck, cancer "cases" weredefined as anyone who had lived in Roebuck for at least one year during the 10-year periodbetween January 1, 1986 and December 31, 1995 and had been diagnosed with lung cancersometime during the same period. Since the first incinerator at Roebuck became operational inMarch 1978, no one at Roebuck could have been exposed to incinerator emissions for more than18 years, at the most. However, the latency period for lung cancer, i.e., the amount of time thattypically must elapse between first exposure and development of the disease, is usually listed as20 to 40 years. Thus, even if incinerator emissions at Roebuck had included carcinogenicsubstances at concentrations capable of producing excess lung cancers (and the availableevidence indicates otherwise), those cancers probably would not have shown up by the end of thestudy period.
Known Causes of Lung Cancer: There is still no convincing evidence that links air pollutionto lung cancer in the general population, especially at the levels found at Roebuck. Most of thelung cancers attributed to air pollution are associated with occupational exposures, e.g.,emissions from smelters and coke ovens. These exposures are typically orders of magnitudegreater that those encountered by the general public. Even so, only a small proportion of lungcancer (15% in men and 5% in women) is associated with occupational agents. By far thestrongest risk factor for lung cancer, and one of the most important confounding factors inoccupational studies, is smoking and other uses of tobacco products.
Smoking is the primary cause of lung cancer, accounting for 80-90% of the incidence of thatdisease (54). A 2 pack-a-day smoker is 15-25 times more likely to develop lung cancer than is anon-smoker. Cigarette smoke contains approximately 1-25 ug arsenic/cigarette (considered byEPA and IARC to be a known human lung carcinogen), in addition to a variety of othercarcinogens such as cadmium, 2-naphthylamine. 4-aminobiphenyl, benzo(a)pyrene, andbenzo(a)anthracene (54). By comparison, the maximum concentration of arsenic in air atRoebuck was 0.00298 ug/m3. Anyone breathing this air 24 hours a day for an entire year wouldinhale only 25 ug of arsenic, i.e., an amount equal to that which might be contained in a singlecigarette. During 1995, the median prevalence of smoking was 22.4% in the U.S. and 23.7% inSouth Carolina, overall (55). However, upstate where Roebuck is situated, the incidence ofsmoking is closer to 30%. The SCDHEC Cancer Cluster Investigation at Roebuck found that85% of all lung cancer cases for whom smoking history was available (20 of 25) were smokers. Of the 15 lung cancer cases diagnosed at Spartanburg Regional Medical Center from 1986-1995and abstracted during the American Cancer Society Case Review, fully 93% were smokers.
Based on all of the considerations outlined above, ATSDR considers that smoking, and not exposure to incinerator emissions, is the most plausible explanation of the slight excess of lung cancer in Roebuck, South Carolina.
|Community Concern # 2:||noxious odors, especially in the past, that cause difficulty in breathing, burning eyes, asthma, and sinus problems|
The residential community of Roebuck has reported many instances when noxious odors have migrated through their community. From a review of available air monitoring data, ATSDR has determined that since many substances may be detectable at extremely low concentrations by their odor alone, especially when heated, it is not unlikely that the incinerator has been the source of some noxious odors in the past. However, none of the chemicals listed in Tables 5 and 6, Appendix B, would produce dyspnea, burning eyes, asthma or sinus problems at the indicated concentrations. However, at sufficiently high concentrations, several of these chemicals could be irritating to the eyes, nose and throat. Although none of the data currently available to ATSDR indicates that emissions from the incineration facility were high enough to produce such effects, that does not rule out the possibility that excursions to much higher levels occasionally occurred in the past during periods not covered by existing data. Such excursions may account for some past complaints of noxious odors and burning eyes. At such times, if the levels were high enough, they might exacerbate symptoms of pre-existing asthma and sinus problems, but it is highly unlikely that they would cause those ailments. These last comments are purely speculative, however. While ATSDR accepts as valid the reported health concerns, the agency cannot identify the incinerator as the cause of those symptoms, based on the available data.
Community Concern # 3: potentially hazardous releases from the incinerator's thermal release vents
South Carolina Department of Health and Environmental Control (SCDHEC) reports from the on-site inspector indicated that the thermal release vents (TRVs) opened regularly in the past, including when the incinerator was operating 'on waste' (27). No on-site air sampling was performed during these episodic events. Controls were added to these vents to prevent their opening regularly.
In the past, the opening of the vents would have created small, point source releases. While noair monitoring was conducted on-site near an opened vent, if the wind direction was toward theair monitors in the community, any contamination would be detected. As stated earlier, the off-site air data indicated the maximum concentrations of all of the contaminants listed in Tables 5and 6, Appendix B, were far below levels that could produce adverse effects, includingrespiratory irritation.
Community Concern # 4: alleged drum burial in Roebuck
Residents voiced concern over an alleged drum burial site within the Roebuck area. One site waslocated 5-10 miles away that is currently under remediation. On several instances, SCDHECstaff attempted to locate the alleged burial site in Roebuck. On February 6, 1990, SCDHEC staffinvestigated the possibility of buried drums on land owned by the facility, land owned by aresident, and land owned by ABCO. The entire area was visually inspected and no indication ofburial activities was evident such as freshly disturbed soils or dead vegetation (25). Due tounderground high pressure gas lines, overhead transmission lines, and railroad tracks, noelectromagnetic survey was conducted.
On another instance in February of 1996, SCDHEC staff investigated an area reported by aresident as a drum burial site on a map. The area was completely planted with pine trees and theundergrowth was dense (26). No dead trees or surface depression areas were noted. Because thetrees were two to three feet apart, the metal detectors could not be used (26).
If a drum burial site is found in Roebuck, ATSDR will review any environmental data collectedand evaluate the public health impact of the drum burial site.
Community Concern # 5: contamination of former ABCO spray field
Residents expressed concern about contamination of the former ABCO spray field. Minimaldata and reports exist for the spray field. In 1976, ABCO requested to use a six acre, gentlysloping, slightly terraced area for the disposal of wastewater from the treatment plant (24). Thearea had closely spaced pines with some underbrush. The over all assessment of the site wasdescribed as "marginal" due to soil characteristics and to the variable and undeterminable natureof the effluent (24).
On many incidents, the runoff holding pond below the spray field was full and overflowing (17). A second catchment pond was created but this pond was found to overflow occasionally too. The discharge from this area on one occasion was described as dark black in color with foam(21). A Consent Order was issued which established a schedule for the installation of adequatewaste treatment facilities (17). However, several additional incidents were noted after theconsent order so SCDHEC began the process of taking further enforcement action, including theissuance of substantial civil penalties on a per discharge basis (18).
Due to a resident's concern that the former ABCO spray field may have contaminated thegroundwater and surface water on his property, SCDHEC obtained private well, surface water,and sediment samples from this residence in March of 1997. This residence is located south ofthe spray field. No VOC contamination was detected in the private well, surface water, andsediment samples that were collected. The concentrations of metals in private well and sedimentsamples were below levels of health concern. For further information on the concentrations ofmetals, please refer to the Toxicological Evaluation section of this public health assessment.
Community Concern # 6: the potential release and deposition of dioxins
Residents expressed concern that the first incinerator used by ABCO years ago may havereleased dioxin. Little information is known about this incinerator. If it was not run attemperatures high enough to destroy dioxins, then the first incinerator may well have releasedmore dioxin than do more modern incinerators with better controls. Due to this potential forgreater release and deposition of dioxins in the past, ATSDR recommends testing the soil at theperimeter of the facility for dioxin. ATSDR staff will evaluate any new data for public health significance.
ATSDR recognizes that infants and children may be more vulnerable to exposures than adults incommunities faced with contamination of their air, water, soil, or food. This vulnerability is aresult of the following factors:
- Children are more likely to play outdoors and bring food into contaminated areas.
- Children are shorter, resulting in a greater likelihood to breathe dust, soil, and heavyvapors close to the ground.
- Children are smaller, resulting in higher doses of chemical exposure per body weight.
- The developing body systems of children can sustain permanent damage if toxicexposures occur during critical growth stages.
Because children depend completely on adults for risk identification and management decisions,ATSDR is committed to evaluating their special interests at the Laidlaw Environmental Services(TOC) site, as part of the ATSDR Child Health Initiative.
Children who are the most likely to be exposed to environmental media at the Laidlaw siteinclude children living in nearby homes and children who attend the nearby day care. During thesite visit, ATSDR staff met with the petitioner and several community residents. These residentsexpressed concern over the nearness of the incinerator to the day care and playground. At thistime, however, ATSDR has reviewed available environmental data and determined that noadverse health effects are expected for residents, including children, surrounding the Laidlawincinerator site.