DEKALB PEST CONTROL SERVICES, INCORPORATED
AVONDALE ESTATES, DEKALB COUNTY, GEORGIA
No physical hazards are at this site that pose a threat to public health. The area surrounding the site is approximately 50% residential and 50% commercial/industrial (Figure 3). The closest residential property is adjacent to the site. Three schools are within a mile radius of the site with the closest school approximately 2,000 feet to the southeast. Demographic information for a one-mile radius of the site is in Table Set 5.
ATSDR and GDHR evaluate chemical releases and assign categories of human exposure pathways to those releases. An exposure pathway is a description of the process by which a chemical contaminant moves from a source of contamination to a receptor population. A completed exposure pathway exists if all five of the following elements exist: 1) source of contamination, 2) a transport mechanism to the environmental medium; 3) a point of exposure; 4) a route of exposure to the body; and 5) a receptor population.
Because there was a potential exposure pathway of pesticide-contaminated soil in the past, this exposure pathway requires discussion. Though these pesticides existed at levels above the reportable quantities prior to remediation, a public health hazard only exists if there was an actual exposure to the chemical and at high enough doses to result in adverse health effects. A review of the scientific literature on possible health effects associated with the contaminants of concern was conducted, and the results are included in this section of the health consultation.
Levels of contaminants discussed in this section are not thresholds for health effects, but concentrations at or below which exposure may be considered safe. Levels of exposure above these values do not indicate that adverse health effects can be expected .
Potential Exposure Pathways
The source of and transport mechanism for contamination at this site is the improper disposal of pesticide containers and rinsate from cleaning pesticide applicators containing unused (virgin) chlorinated hydrocarbons (pesticides). The contaminants were disposed on site directly onto surface soil and foliage on the eastern border of the property.
No groundwater or air sampling was conducted at this site. No public or private water systems are within 3 miles of this site. Chlorinated hydrocarbons do not dissolve easily in water but stick strongly to soil particles at the surface. They are not likely to leach deeper into soil or enter groundwater.
Surface and subsurface soils were sampled and found to be contaminated. The point of exposure at Dekalb Pest Control Services, Inc., is contact with contaminated surface soil. The primary route of exposure to contaminants is ingestion: direct ingestion of soil (e.g. children with pica); ingestion of soil-contaminated food (e.g. handling and eating food); eating products grown in contaminated soil; ingestion of soil dust during work or recreational activity in the contaminated area (e.g. gardening), and handling pets which have contacted contaminated soil.
The site is located on private property with unlimited access. Persons who may have been exposed to contaminants at this site include tenants, employees, contractors, guests of tenants, and trespassers. The persons at greatest risk for exposure were the former tenants of the property who owned and operated Dekalb Pest Control Services, Inc., and were subsequently held legally responsible for the improper disposal of the chemicals. Pesticide labeling has the force of law, and that the applicator is responsible for use in accordance with label precautions and directions for handling, transporting, applying, disposing, and storing of these chemicals. No information is available about the operator(s) safety procedures, use of protective equipment, or health status.
Contaminants of concern
GDA sampling data from 1991 indicated the presence of three chemicals in soil samples taken from two different locations at the facility. Chemicals which were found in soil at concentrations above reportable quantities were chlordane, dieldrin, and heptachlor epoxide. These data have not been validated or replicated. All subsequent data confirms only the presence of chlordane at levels exceeding reportable quantities. These chemicals and the maximum concentrations detected in soil samples are summarized in Table 6, along with the ATSDR comparison values (CV) for each contaminant. CVs are derived from exposure scenarios used to estimate a dose at which health effects might be observed. Concentrations less than the CV are unlikely to pose a health threat, and concentrations above the CV do not necessarily pose a health threat.
On the basis of these very conservative guidelines, GDHR derived exposure doses and an excess cancer risk value for potentially exposed individuals (Table 6). Estimates for exposure to chlordane and dieldrin through ingestion of soil exceeded health guidelines (minimal risk levels [MRL]) based on chronic limited exposure (365 days/year for 15 years [length of operation of facility until remediation]). There is no MRL for heptachlor epoxide, so the highest concentration was compared to the lowest CV, which was also exceeded.. In addition, cancer risk estimates for potentially exposed individuals exceed acceptable risk value based on chronic long-term exposure (365 days/year for 70 years). CVs and cancer risk estimates are discussed in Appendix A.
The maximum level of chlordane found in soil prior to remediation was 164.8 parts per million (ppm). The CV for chronic exposure to chlordane in soil for a child is 30 ppm and for an adult is 400 ppm (Table 6).
The maximum level of dieldrin found in soil prior to remediation was 9.94 ppm. ATSDR's CV for chronic exposure to dieldrin in soil for a child is 3 ppm and for an adult is 40 ppm (Table 6).
The maximum level of heptachlor epoxide found in soil prior to remediation was 9.27 ppm. The CV for chronic exposure to heptachlor epoxide for children is 0.7 ppm and for an adult is 9 ppm (Table 6)
Potential Health Effects
The most common route of human exposure to these chemicals is inhalation exposure to contaminated indoor air from application of these pesticides. No data on indoor air levels of pesticides at the facility exist. Dermal exposure is not considered a significant route of exposure   . These pesticides are rarely found in soil except in spill or illegal disposal scenarios.
These three pesticides have been banned in the United States since 1987 because of concerns about the risk from long term dietary exposure. No actual adverse human health effects have been linked to dietary exposure. The chemical composition and potential health effects from exposure to all three of these pesticides are very similar and will therefore be discussed as a group.
The receptor population is the former owners/operators of the subject facility. Potential health effects were investigated from a possible worst-case-scenario perspective; specifically, a child with pica who has chronic exposure.
Most health effects in humans that may be linked to ingestion exposure to these chemicals involve the central nervous system and digestive systems   . These effects were mostly observed in people who swallowed mixtures containing one or more of these chemicals. There are no documented cases of high or low level ingestion exposure over a long period of time. Workers in manufacturing plants who are known to have had moderate exposure over a long period of time developed headaches, dizziness, vomiting, irritability, and convulsions. Workers removed from the source of exposure rapidly recovered from most of these effects. Scientists do not know whether these chemicals affect the ability of people to have children or whether they cause birth defects   .
We have no direct evidence that these chemicals cause cancer in humans. Studies on humans generally show no increase in cancer or deaths due to cancer. The International Agency for Research on Cancer (IARC) has determined that chlordane, dieldrin, and heptachlor epoxide are not classifiable as to their carcinogenicity to humans. The EPA has placed these three chemicals in the "probable human carcinogen" category.