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ATSDR evaluates contaminants detected in environmental media at a site and determines whether an exposure to them has public health significance. ATSDR begins this evaluation by gathering reports that contain relevant environmental data for the site. To address the concerns expressed by the THAN petitioner, ATSDR evaluated environmental data for on-site air, off-site air, surface water, sediment, and groundwater. These data are reviewed to determine whether the levels of contaminants are above health-based comparison values. ATSDR's health-based comparison values are media-specific concentrations of chemicals that are not likely to result in adverse health effects under default conditions of exposure. They are used for screening purposes only; the fact that one is exceeded by a site-specific contaminant concentration does not, by itself, necessarily imply the existence of a public health hazard. Determination of the public health implications of an exposure requires further evaluation of the various factors that influence the magnitude and potential consequence of exposure. Please refer to Appendix C for additional information on health-based comparison values.

Once the environmental data have been obtained and evaluated, ATSDR staff determine whether people were, or continue to be, exposed to contaminants at levels of health concern. For further information on ATSDR's methodology, please refer to Appendix D. The following text provides ATSDR's evaluation of the THAN site.

    On-Site Air

The petitioner was concerned that potential health hazards existed from the LTTD of soils on the western parcel. Focus Environmental, Inc. conducted on-site ambient air monitoring immediately before and during transfer and processing of soil, which occurred from June 26 to October 22, 1993. Air at the site perimeter was sampled for pesticides and respirable particulates. The monitoring detected at or within the fence-line several contaminants in air that exceeded ATSDR comparison values for those chemicals (Table 1) (Focus, 1994).

A completed exposure pathway to air existed on-site in the past for workers and trespassers during the LTTD of soil from the western parcel. The transfer and processing of soil on the eastern parcel may contribute to current air exposures. Inhalation would be the main route of exposure. However, the available data indicate that the concentrations of chemicals and particulates at the THAN site were within occupational exposure limits and were below levels that might cause adverse health effects in humans.

No adverse health effects would be expected even though the maximum recorded on-site concentrations of some pesticides in ambient air exceeded cancer-based comparison values (the ATSDR cancer risk evaluation guide [CREG] and the EPA risk-based concentration for cancer effects [RBC-C]). These comparison values are based on quantitative cancer risk estimates which, in turn, are based on the assumption that 1) exposure by the designated route will be chronic and essentially life-long, and 2) the contaminant of concern can actually cause cancer in human beings via a mechanism (i.e., DNA-damage) that theoretically exhibits no threshold.

However, neither of these assumptions applies to the potential pesticide exposures at THAN site because: 1) none of these pesticides is significantly genotoxic, which is to say that the estimated on-site exposures were not likely to cause DNA damage (a prerequisite for the zero-threshold assumption mentioned above); 2) in the absence of relevant studies, it is not known whether inhalation exposure to these pesticides can cause cancer, in either animals or humans; 3) the cancer-based comparison values for these pesticides are based on equivocal data from oral studies in rodents, only some of which suggested that high-level oral exposure over most of the animals' lifetimes could result in a slight increase of liver tumors, which are normally much more common in rodents than in humans; and 4) estimated, on-site exposures at the THAN site would have been intermittent rather than chronic, would have lasted for only a small fraction of a lifetime, and would have been at low levels relative to any level known to cause adverse effects in either animals or humans. Thus, ATSDR considered that, while the cancer-based values for these pesticides were useful for screening, they were not relevant to the evaluation of plausible health implications at this site.

    Off-Site Air

The petitioner was also concerned that potential health hazards to the community existed from the LTTD of on-site soils from the western parcel. In 1993, Focus Environmental, Inc. conducted off-site ambient air monitoring immediately before and during transfer and processing of soil. Pesticides, but not respirable particulates, were sampled in off-site and downwind areas. Only one contaminant, DDT, was detected on two occasions, both times at levels just above ATSDR comparison values for chronic exposure (Table 1) (Focus, 1994).

Available air sampling data collected in 1993 indicated that ambient air in downwind, off-site areas did not contain contaminants at levels of health concern. A completed exposure pathway to off-site air existed in the past for residents living near the site during the LTTD of soil from the western parcel, and the transfer and processing of soil on the eastern parcel may contribute to current inhalation exposures. Only one of the compounds listed in Table 1 exceeded comparison values. DDT slightly exceeded ATSDR's CREG comparison value, but the difference was neither mathematically nor biologically significant. (All of ATSDR's comparison values are rounded off to the nearest significant digit and contain substantial margins of safety, with the CREGs being the most conservative of all.) Because the CREG is based on prolonged chronic exposure, and only 2 of the 77 off-site samples contained DDT, the CREG is even less relevant to off-site exposures than it was to on-site exposures. (See explanation in the last paragraph of the preceding section.) Thus, it is unlikely that adverse health effects could result from breathing ambient air with the reported levels of DDT. Levels of respirable particles on-site were below the occupational standard of 3,000 µg/m3 (ACGIH, 1995). Levels off-site would be even lower, i.e., unless there existed another source other than the THAN site.

    Surface Water

The petitioner expressed concern about contamination of a holding pond used annually to host a fishing rodeo for children. ATSDR was unable to locate in the site documentation it collected any references to an annual fishing rodeo for children. However, the description in the petition letter says this holding pond is "very close to the site," and this resembles two nearby off-site, down-gradient areas where surface water exists: a depression area south of the site and a small Department of Transportation (DOT) surge pond (referred to as the south pond). Drainage from the southern and eastern portions of the site flows to the south pond via a culvert beneath Schley Avenue. Past, current, and future potential exposures to these off-site surface water ponds by residents (adults and children) could exist during the fishing rodeo. However, these potential exposures to surface water are likely to be infrequent and limited to dermal contact and incidental ingestion.

In 1995, the south pond and the depression area were sampled for metals, pesticides, herbicides, and volatile organic compounds (see Table 2). Atrazine, a herbicide, and manganese, an essential nutrient metal, were the only substances detected above comparison values. However, the comparison values for both are specific for drinking water and assume ingestion of 1 liter per day by a 10-kilogram child. Incidental ingestion during water activities would be much lower (e.g., 0.15 liters per day during swimming). In addition, the comparison value for atrazine includes a safety factor of 100 (IRIS, 1999a). The comparison value for manganese is not based on adverse health effects; it merely represents the high end of normal dietary intake of this essential nutrient (ATSDR, 1999c). Therefore, any exposure resulting from infrequent, incidental ingestion of or dermal contact with water contaminated with the maximum detected levels of atrazine and manganese would not pose any threat of adverse health effects to children, during the fishing rodeo or at any other time.


As mentioned previously, the petitioner expressed concern about contamination of a holding pond used annually to host a fishing rodeo for children. In 1995, sediment in the south pond and the depression area were sampled for metals, pesticides, herbicides, and volatile organic compounds (see Table 3). DDD, DDE, arsenic, cadmium, iron (an essential nutrient), and toxaphene were all detected above comparison values. However, none of these substances was present in sediment at levels that could pose a threat of adverse health effects, under site-specific conditions of exposure. First, because ATSDR has no comparison values specific for sediment, the agency uses its soil comparison values, which assume the incidental consumption of 200 milligrams (mg) of soil per day for children and 100 mg per day for adults. Daily consumption of pond sediments, if it occurs at all, is certain to be very much lower than these default rates for soil. Second, all the comparison values exceeded (i.e., CREGs or chronic child environmental media evaluation guides [EMEGs]) were based on chronic, essentially lifelong exposure, a scenario that is clearly unrealistic with regard to pond sediments. Because past, current, and future potential exposures to sediment in these off-site surface water ponds are likely to be infrequent and limited to dermal contact, ATSDR's soil comparison values will be exceedingly conservative when applied to contaminants in those sediments. Therefore, under site-specific conditions of exposure, no adverse health effects of any kind are likely to result from contact with any of the chemical contaminants in pond sediments at this site.


The petitioner expressed concern that the groundwater aquifer that supplies drinking water to the area contains contamination. Groundwater samples on or near the THAN facility were collected to characterize the nature and extent of contamination (WCC, 1992b). Groundwater samples were tested for volatile organic compounds, semi-volatile organic compounds, pesticides, and metals. In on-site groundwater, 37 contaminants were detected in 1992 above drinking water health-based comparison values (see Table 4). Recent groundwater monitoring results from on-site wells (sampled in February 1999) and perimeter wells (sampled in September 1998) are included in Table 5.

Groundwater beneath the site contains contamination at levels of health concern; however, no one uses this on-site groundwater as a drinking water source. Monitoring results for perimeter wells installed at the outer edges of the plume have not indicated any contamination at levels of health concern. Until on-site groundwater is remediated, a future potential exposure pathway exists to off-site groundwater in the vicinity of the site. Residents using private groundwater supply wells that are down-gradient from the site (i.e., east and northeast) for drinking and bathing may be exposed in the future via ingestion, inhalation, and dermal contact if the groundwater contamination plume migrates.


ATSDR identifies community health concerns as part of its evaluation of the public health implications posed by contamination at a site. These concerns and ATSDR's responses are described below:

Concern: Is the community at risk of potential health hazards from baking contaminated soils on-site (i.e., low temperature thermal desorption)?

In February 1993, ATSDR reviewed the thermal desorption work plan to ensure that the planned activity was protective of public health. No air data were available at that time to review so ATSDR could not fully comment on the health impact from LTTD. However, using available air sampling data collected later in 1993 during the LTTD of soils, ATSDR determined that ambient air in downwind, off-site areas did not contain contaminants at levels of health concern.



Is the holding pond contaminated that is used annually to host a fishing rodeo for children?


ATSDR was unable to locate any references to an annual fishing rodeo for children in the site documentation the agency collected. However, the agency did find and review data from two down-gradient ponds. Under site-specific conditions of exposure, the detected levels of contaminants in the surface water and sediment from these ponds are insufficient to cause any adverse health effects in adults and children. (See sections 4.3 and 4.4 in this public health assessment.)


Are increased numbers of cancer cases occurring in the immediate vicinity of the site?


Cancer mortality was available for Dougherty County. The cancer morality rate for Dougherty County as a whole has been documented as being higher than for the rest of the state of Georgia (Georgia Division of Public Health, 1998).

However, ATSDR was not able to determine whether an increased number of cancer cases exists in the immediate vicinity of the site, because no cancer data specific for the small community around the THAN site were available for review. Nevertheless, using a review of relevant sampling data and an evaluation of potential exposures, ATSDR can state that none of the site-related contaminants, at the current levels detected, would represent a plausible cause of cancer effects in humans. (See Section 4 for details.)



Information is lacking concerning the impact of contamination on the local area.

Response: ATSDR's Preliminary Public Health Assessment, dated June 20, 1990, contained recommendations for further characterization of the THAN site and surrounding community. Specifically, ATSDR recommended sampling soil and groundwater, surveying of private wells in use in the area, and monitoring private wells where appropriate. Since the 1990 Preliminary Public Health Assessment, extensive soil, groundwater, and surface water testing have occurred (EPA, 1993). Because contamination above clean-up goals was detected, remedial activities have occurred and are occurring on-site (EPA, 1996). In 1993, remediation of OU 1 was initiated, removing contaminated groundwater, and surface soil from the western parcel (EPA, 1993). In a baseline risk assessment dated April 28, 1995, EPA published the results of an extensive sampling effort including on- and off-site soil, sediment, and surface water samples (EPA, 1995). Since this concern was voiced in 1992, extensive information concerning the site has been gathered.

Pollution exists in the aquifer that supplies drinking water for the area.

Response: Groundwater monitoring has indicated contamination of the aquifer underlying the THAN site. A private well survey in 1991 found records of approximately 315 wells in a 3-mile radius of the site. However, perimeter wells installed at the outer edges of the plume have not indicated contamination at levels of health concern. This review of perimeter wells does not indicate any expectation that off-site private wells have been affected by site contamination. Because private wells do exist in the area, ATSDR recommends that private well sampling be performed if perimeter wells at the THAN site should ever exhibit contamination at levels of health concern.

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