PUBLIC HEALTH ASSESSMENT
DAVIS TIMBER COMPANY
HATTIESBURG, LAMAR COUNTY, MISSISSIPPI
The Davis Timber Company site is in a rural area of southeastern Mississippi, approximately 6 miles northwest of Hattiesburg, Mississippi. The facility has operated since 1966, using pentachlorophenol (PCP) as a wood preservative between the years of 1972 and 1987. The Mississippi Department of Environmental Quality (MDEQ) has documented intentional and accidental releases of contaminants from the facility's wastewater treatment holding pond. Fish kills have occurred in the lakes downstream of the site, and fish have been contaminated with PCP and various chlorinated dibenzodioxins (dioxins) and dibenzofurans (furans).
Country Club Lake Estates is located along Mineral Creek, approximately 1 mile downstream from the Davis Timber Company site. Mineral Creek, County Club Lake, and a private lake (Phillips Lake) have been contaminated with chemicals similar to those found at the Davis Timber Company site.
In 1989, the MDEQ petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a public health assessment of Country Club Lake Estates. ATSDR classified Country Club Lake Estates a public health hazard because concentrations of PCP and dioxins and furans detected in fish exceeded public health guidelines. ATSDR recommended that new environmental, toxicological, or health outcome data be reevaluated as they became available.
New environmental sampling was conducted in 1995, 1997, and 2000. Elevated levels of PCP and dioxins and furans were detected in on-site subsurface soil and on-site and off-site sediment samples. After reviewing these new data, ATSDR has concluded that the Davis Timber Company site is a current public health hazard because of physical hazards on the site. The Davis Timber Company site is a potential future public health hazard because dioxins and furans remain in on-site soils and sediments. Fish samples collected from County Club Lake contained detectable levels of dioxins and furans, although the levels are decreasing. The County Club Lake was a public health hazard in the past because residents who ate contaminated fish from the lake may have been exposed to dioxins and furans at levels of health concern. The estimated amount of dioxin exposure in some residents might have increased the possibility of altered social behavior and thyroid cancer, and caused mild damage to the immune system. ATSDR recommends more in-depth characterization of on-site surface and subsurface soils, groundwater, and contaminated fish downstream of County Club Lake.
The Davis Timber Company site was proposed for the National Priorities List (NPL) on May 11, 2000, and added to the NPL on July 27, 2000. The NPL is the list of hazardous waste sites throughout the United States with the highest priority for cleanup under the federal Superfund program.
A copy of this document was available for public comment from July 17, 2002, through September 16, 2002. To date, no comments have been received in response to the public release.
The Davis Timber Company (the facility) is located on Jackson Road, approximately 6 miles northwest of Hattiesburg, Lamar County, Mississippi. The facility comprises approximately 30 acres, bounded to the north by a power line, to the west by West Mineral Creek, to the south by a former railroad track which is now a walking trail, and to the east by Jackson Road. The site consists of a skag mill, a debarker, a pole peeler, a waste bark pile, a storage pond, an office, a treating cylinder, a cooling pond, an oil separator, two aboveground oil storage tanks, two aboveground pentachlorophenol (PCP) solution storage tanks, and a storage yard (1) (Figure 1 in Appendix A). The site is hilly with elevation increasing to the north of the site. Portions of the site are hard-packed dirt, gravel, asphalt, or concrete, while other areas are overgrown with grass, trees, and heavy vegetation (2). The site is not fenced and is accessible to the public.
The Davis Timber Company conducted timber processing and wood preserving operations in the past. The company began operations in 1966 as a producer of untreated poles at another nearby location. The facility began wood treatment operations at the present location in 1972. The treatment operations were discontinued in 1987 as a result of state regulatory actions by the Mississippi Department of Environmental Quality (MDEQ). The Davis Timber Company filed for bankruptcy and closed in 1990 (3). The current owners of the property are not believed to conduct any chemical treatment operations on the site.
During active facility operation, the Davis Timber Company produced treated pine poles, pilings, and timber. Facility operations included bark removal, treatment of wood with PCP, and product storage. In addition, a skag mill was operated at the facility to salvage timber unsuitable for poles or piling. The facility received raw wood, which was weighed and stocked in the open yard for debarking. Logs were cut to length and prepared for treatment. Poles or piles then were pulled into a treating cylinder for pressure processing. The timber was conditioned with steam. After sap fluids, steam condensate, and residual oil were removed from the cylinder walls, the timber was treated with a 5 percent PCP solution and diesel oil or a light cycle oil. Following treatment, excess preservative solution was removed from the treating cylinder by a vacuum process. Steam was then introduced to clean the poles. Treated materials were removed from the cylinder for drying and storage in the open yard before shipment (1).
The Davis Timber Company discharged process wastewater containing PCP into an on-site storage pond approximately 2 acres in size. The storage pond was occasionally intentionally drained and has overflowed during heavy rains. Wastewater contaminated with PCP was released from the storage pond into West Mineral Creek, which drains into County Club Lake. In October 1980, the storage pond was reportedly closed, backfilled, and capped with approximately 6 to 8 inches of clay. A cooling pond just west of East Mineral Creek overflowed at times releasing PCP-contaminated water into East Mineral Creek. Surface runoff from the property flows into East and West Mineral creeks. A drained pond downstream of the facility receives runoff from the site via West Mineral Creek. Other waste products produced by the facility include bark and wood fiber from the debarker and peeler; oil, steam condensate, and wood sap extract from steam seasoning; and preservative containing PCP that was spilled on the ground in the vicinity of the tanks and treating cylinder (4).
Between 1974 and 1987, the MDEQ noted many violations and issued several orders to the Davis Timber Company for improper operations at the facility. During the same period, the MDEQ also documented six fish kills in County Club Lake, a 66-acre lake about 1 mile downstream of the facility. Several of the fish kills were attributed to releases of PCP from the Davis Timber Company. The Country Club Lake Estates is a residential development with a golf course and County Club Lake. County Club Lake is used for boating, swimming, and sport fishing. In 1987, MDEQ issued a warning advising the public not to consume fish from County Club Lake because of high levels of dioxin detected in fish tissue samples collected from the lake (1). Phillips Lake, a private lake 2 miles downstream of County Club Lake, covers 62 acres and has also been used for recreational fishing and swimming. Fish kills have also been documented in Phillips' Lake (5).
In 1989, the Agency for Toxic Substances and Disease Registry (ATSDR) was petitioned by the MDEQ to conduct a public health assessment at Country Club Lake Estates on behalf of the residents of the community (Appendix D). In that public health assessment, released in January 1993, ATSDR classified Country Club Lake as a public health hazard because concentrations of PCP and chlorinated dibenzodioxins (dioxins) and dibenzofurans (furans) detected in the lake exceeded public health guidelines (6).
The Davis Timber Company site was proposed for the National Priorities List (NPL) on May 11, 2000, and added to the NPL on July 27, 2000. The NPL is the list of hazardous waste sites throughout the United States with the highest priority for cleanup under the federal Superfund program. Remediation efforts at the site by the U.S. Environmental Protection Agency (EPA) are in progress.
The Davis Timber site is in Hattiesburg, Lamar County, Mississippi. According to 1990 Census data, some 516 people live within a 1-mile radius of the site. The specific ethnic groups within the 1-mile radius are as follows: 452 Caucasians; 63 African Americans; 5 Hispanics; and 1 American Indian, Eskimo, or Aleut. Of the residents within the 1-mile radius, 53 are children aged 6 and younger and 35 are adults aged 65 and older. Approximately 202 housing units are within the 1-mile radius (Figure 2 in Appendix A).
Land in the vicinity of the Davis Timber site is a mixture of commercial (pine timber) and residential areas. Residential subdivisions are south and east of the site. Construction of residential homes continues in and around County Club Lake. Lamar County is expecting between 7 and 15 percent residential growth (3).
Two intermittent creeks are located on the east and west sides of the Davis Timber property. The eastern intermittent creek, East Mineral Creek, flows northeast and intersects County Club Lake about 1.25 miles downstream from the site. The western intermittent creek, West Mineral Creek, flows north and east and intersects County Club Lake about 1.25 miles from the site. Water from County Club Lake flows into Mineral Creek, which intersects the Bowie River about 3 miles northeast of the lake. A privately owned lake, Phillips Lake, is located between County Club Lake and the Bowie River. The Bowie River flows in a southeasterly direction for about 4.75 miles and intersects the Leaf River (1).
East and West Mineral creeks are intermittent and not large enough to be fished. County Club Lake is a recreational fishery and a designated recreational area. Largemouth bass, bluegill, and other sunfish are the predominant fish known to be present in the lake. Mineral Creek is large enough to support a fishery; however, it is not known to what extent the creek is fished. The Bowie and Leaf rivers are heavily fished for consumption.
The area surrounding the Davis Timber site is very rural. No other industries or companies are in the vicinity of the Davis Timber site. The site is in the Longleaf Pine Hills division of the East Gulf Coastal Plan Physiographic province. This is a belt of fertile farmland and is the state's chief timber-producing area (1).
The aquifer of concern in the area is the Citronelle/Miocene aquifer complex. The Citronelle aquifer is hydraulically connected to the underlying Miocene aquifer system, which has a depth to fresh water of about 1,000 feet below land surface. The depth of the water table, which also corresponds to the top of the aquifer, is about 15 feet below land surface. The unsaturated zone is composed of sands, clayey gravel, and sandy clays (7).
Groundwater in the area of the site is used for domestic purposes. Some private wells are in the area, particularly to the south and southeast of the site. About 202 housing units are within 1 mile of the site. A well survey conducted in the study area indicates that most homes are supplied by wells operated by area utility companies. All of the utility company wells are cased and tap into the Miocene aquifer, with an average well depth of approximately 750 feet. The nearest drinking water well is a private well located about 4,000 feet southeast of the site.
On April 10, 2001, ATSDR staff visited the Davis Timber site. As part of the visit, staff met with representatives from the MDEQ for a walking tour of the Davis Timber site. MDEQ staff explained the layout of the facility and pointed out areas of interest. To get an idea of the proximity of residences and land uses in the area, staff also drove around the area surrounding the site. During the visit, staff observed on-site and off-site conditions, including land use in areas adjacent to the site, the ease of site access, the proximity of residential areas, the presence of on-site physical hazards, and the general characteristics of the different buildings.
The residential property nearest to the site was approximately 100 feet east of the site on Jackson Road. The home is currently occupied. Several other residential properties are south of the site on Melton Street. A path immediately south of the site (along the former railroad tracks) is used by area residents for walking, biking, or jogging.
Access to the site is unrestricted. There was evidence that the site had been accessed for recreational purposes. Tracks from an all-terrain vehicle (ATV) were observed in the area near the former on-site pond. The ATV tracks could have originated from recreational trespassers or on-site facility or remedial workers. No facility or remedial workers were present on the site during the time of our visit. The northern portion of the site contained a few remaining buildings. Several windows to a locked machine shop were broken, and the broken glass lay on the ground. A mobile structure (similar to a trailer) was located beside the shop. The wooden double doors of the trailer were chained, but entrance could be gained through the top of one of the doors that was slightly ajar. The trailer appeared to contain various glass bottles and equipment. We also observed a storm drain with a loose cover west of the shop. The loosened cover could be dislodged and could present an entrapment hazard for a small child.
A small, open shed about 20 feet east of the shop appeared to be used as a makeshift machine shop. Other structures observed on-site included the remnants of the pole peeler and bark remover and several aboveground storage tanks.
A mounded area in the western portion of the site indicated the location of the closed on-site storage pond. The shallow ditch surrounding the mound contained a black, oily substance. The substance was believed to have leached from the closed storage pond. A portion of West Mineral Creek was dammed to form a small pond. Tires, household appliances, and other debris were discarded on the path to the small pond. A black, shiny substance was observed on the surface water of West Mineral Creek adjacent to the small pond. The source of the substance was not known at the time but appeared to have resulted from an overflow of the small pond.
Dark stains were also observed on the ground near the bark remover and at the rear of the machine shop. A steep, open ditch containing a large pipe was located along the southern portion of the site. The origin or purpose of the pipe is unknown. Drainage from the pipe would flow into East Mineral Creek and/or the walking path. East Mineral Creek appeared to be dry and did not contain a lot of vegetation at its origin on the site.
A number of physical hazards were observed. Pieces of wood with protruding rusty nails were observed throughout the site. Trespassers could be injured by stepping or falling on a protruding nail. Trip and fall hazards are possible due to the uneven terrain. The grassy areas to the north and south may harbor ticks or other biting insects.
Staff also drove to the County Club Lake and observed a spillway where overflow water entered Mineral Creek. Staff observed private residences near the lake, but an area for public access to the lake was not observed.
In 1993, ATSDR released a petitioned public health assessment (PHA) for this site. The petitioned PHA evaluated the environmental data collected from 1974 to 1993 and concluded that exposure to contaminants posed a public health hazard. ATSDR also concluded that it would reevaluate and expand its PHA when new environmental, toxicological, or health outcome data became available (6).
Since environmental conditions at the site have changed, ATSDR will discuss in this PHA the new environmental data received after the petitioned PHA was released. Occasionally, historical data are referenced for trend analysis.
Tables 1 through 3 in Appendix B contain the contaminants and environmental media evaluated for this site. In a subsequent section of the PHA, ATSDR evaluates the contaminants to determine whether exposures have public health significance. The chemicals named in this section have been identified as contaminants of concern based on previous investigations at the site. Samples have been collected from a variety of environmental media since 1974; however, all historical data are not being reported in this document if more recent data exist.
The primary contaminants of concern at this site are PCP and polychlorinated dioxins and furans. Dioxins and furans are related classes of compounds formed by combustion of various chemicals, industrial wastes, and municipal wastes. They are formed naturally in most combustion processes. Humans are exposed to complex mixtures of dioxins and furans that are found in the environment. The most toxic form is 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD); the related furan is only slightly less toxic. Other dioxins and furans (based on differing number of chlorine atoms) can range from slightly less toxic to 1,000 times less toxic. The toxicological concerns resulting from exposure to these mixtures led to the development of the toxicity equivalency factors (TEF) approach. The TEF approach compares the relative toxicity of individual congeners (compounds belonging to the same class) with that of 2,3,7,8-TCDD, which is the most widely studied of chlorinated dioxins. Once this conversion is done, the amount of dioxins and furans are totaled and referred to as 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalents (TCDD TEQs), or TEQs. This approach simplifies the evaluation of a varied group of compounds and allows a comparison to ATSDR's health-based values (8).
In February 1995, MDEQ conducted an expanded site investigation of the Davis Timber site. MDEQ collected two subsurface soil samples and nine sediment samples. A subsurface soil sample was collected from the closed on-site storage pond at a depth between 4 to 4.5 feet, and a background subsurface soil sample was collected from an upgradient location. A background sediment sample was collected from Lake Serene, a lake approximately 2.5 miles from the site, for comparison to the two sediment samples collected from County Club Lake. A background sediment sample was collected from West Mineral Creek at an upgradient location. Three sediment samples were collected from West Mineral Creek downgradient of the facility. In addition, two sediment samples were collected from Mineral Creek downgradient of County Club Lake (1).
Elevated levels of dioxins and furans were detected in the subsurface soil sample collected from the on-site storage pond. The total TCDD TEQ detected was 1.074 micrograms per kilogram (µg/kg). There is no applicable comparison value for dioxins in soil. Comparison values are contaminant concentrations in specific media used to select contaminants for further evaluation. ATSDR and other agencies developed the values as guidelines for estimating media concentrations of a contaminant that are unlikely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. While concentrations at or below the relevant comparison value may reasonably be considered safe, it does not follow that any concentration that exceeds a comparison value would be expected to produce adverse health effects.
PCP was detected in the subsurface soil sample at 0.39 µg/kg, which is below ATSDR's chronic Environmental Media Evaluation Guide (EMEG) comparison value of 2,000 µg/kg (9). EMEGs are estimated concentrations in a media where noncarcinogenic health effects are unlikely to occur.
Tables 1 and 2 in Appendix B summarize the data for sediment samples collected from various on- and off-site locations. The tables include current and historical data for limited trend analysis. Table 1 in Appendix B summarizes the PCP contamination in the Mineral Creek Watershed, comprised of East and West Mineral creeks, County Club Lake, and Mineral Creek. PCP concentrations in West Mineral Creek at the on-site storage pond (i.e., the PCP lagoon ) decreased three orders of magnitude between 1991 (16,000 µg/kg) and 1995 (90 µg/kg). PCP levels in 1995 were highest just below the drained pond (360 µg/kg) and at detectable levels (80 µg/kg) between the drained pond and County Club Lake (2). The PCP levels measured in 1995 did not exceed ATSDR's comparison value for PCP of 2,000 µg/kg.
Table 2 in Appendix B summarizes the dioxin/furan concentrations in sediments from 1990 to 1995. As with PCP, the highest measured levels of dioxins and furans (TEQ of 1.4 µg/kg) were just below the drained pond. However, the levels have decreased compared with the 1990 level at that same location (2.4 µg/kg). The dioxin/furan TEQ was 0.7 µg/kg for the sample collected from the on-site storage pond.
In 1997, MDEQ collected several fish tissue samples from the County Club Lake. Three composite fish samples were analyzed for dioxins and furans. The fish tissue concentrations were highest (21.0 picograms per gram, pg/g, total 2,3,7,8-TCDD TEQ) in a large channel catfish. This catfish was thought to have been an older fish because of its large size (7.3 lbs.). Larger, older fish are more likely to contain higher levels of contaminants because they eat smaller fish and have had more time to accumulate contaminants. Bottom dwelling species such as catfish may also accumulate contaminants found in sediments. According to MDEQ staff, the ecology of County Club Lake is not believed to support many fish of this species or size. The predominant fishes in the lake are largemouth bass with an average weight between 0.4 to 0.8 lbs. (10). No channel catfish have been collected from the lake since 1997 despite the efforts of MDEQ.
In July 2000, MDEQ collected several fish from County Club Lake. MDEQ collected four largemouth bass samples consisting of 17 individual fish and one bluegill sample consisting of five individual fish. The largemouth bass were separated into four groups according to weight. According to these sampling results, dioxin levels in fish from County Club Lake continue to decline. Four of the five samples were well below 5 pg/g, which is Mississippi's lower limit for issuing consumption advisories for dioxin. The largest composite sample of largemouth bass had an average specimen weight of 4.3 lbs. and measured a total 2,3,7,8-TCDD TEQ of 5.33 pg/g, which exceeded Mississippi's criteria of 5 pg/g for dioxin.
From 1987 to May 2001, the State of Mississippi had an advisory in effect not to eat fish from County Club Lake (11). In June 2001, the Mississippi Fish Advisory Task Force reviewed sampling results and determined that the original advisory for County Club Lake should be lifted. The Task Force reported that, after years of testing, results showed that concentrations of contaminants have declined to the point that they are no longer a human health risk (12, 13).
Table 3 in Appendix B summarizes current and historical fish data for trend analysis. The level of contamination in fish tissue is decreasing. The highest total 2,3,7,8-TCDD TEQ (156.7 pg/g) was for hybrid sunfish in 1987. Largemouth bass had a total 2,3,7,8-TCDD TEQ of 103.2 pg/g in tissue samples in 1987. Depending on size, the contaminant concentrations have decreased to between 0.076 and 5.33 pg/g in the July 2000 sampling.
Identifying the potential for adverse health effects to occur from exposure to chemicals is done by evaluating human exposure pathways. These pathways are generally separated into completed and potential exposure pathways and then classified by the environmental media contaminated. An exposure pathway consists of five elements: 1) a source of contamination; 2) transport through an environmental medium; 3) a point of exposure; 4) a route of human exposure; and 5) an exposed population.
Completed pathways require that the five exposure elements exist and that exposure occurred in the past, is occurring now, or will occur in the future. Potential exposure pathways have at least one element missing, but evidence suggests that exposure could have occurred in the past, could be occurring now, or could occur in the future. Tables 4 and 5 in Appendix C list the completed and potential exposure pathways for the site.
Completed Exposure Pathways
Former workers at the Davis Timber Company may have been exposed to contaminants in on-site surface soil when the facility was operational. Other trespassers on the site may also have been exposed. On-site surface soils were found to be contaminated with PCP and various dioxins and furans. Wood products treated with PCP were stored on the ground, and PCP preservative was spilled on the ground around the tanks and treatment cylinder. These waste management practices and wood preservative spills likely contaminated the soil. Direct dermal contact and incidental ingestion of soil are the primary routes of exposure by this pathway.
Current on-site remedial or facility workers may be exposed to contaminants in on-site surface soil. The current on-site facility is reported to no longer chemically treat wood, so the levels of surface soil contamination have likely decreased. However, on-site surface soils might still have residual contamination. Access to the site is unrestricted, so trespassing may be occurring on the site. Trespassers likely use the site for recreational purposes such as riding ATVs or hunting. No surface soil sampling has been done at the site since February 1991, so current levels of exposure cannot be estimated.
Subsurface soils were also found to be contaminated with PCP, dioxins, and furans. Future residents may be exposed to contaminants in surface soil if residential homes are built on the site and contaminated subsurface soils are brought to the surface during excavation or building activities. Residents may be exposed via direct dermal contact with or incidental ingestion of contaminated soil.
Former workers at the facility were likely exposed to contaminated wastewater from the two on-site holding ponds. During its time of operation, Davis Timber Company discharged wastewater containing PCP from the pressure treating process into a storage pond on the facility property. Surface water and subsurface soil samples collected from the on-site storage pond were found to be contaminated with PCP, dioxins, and furans (2). Occasionally, workers would drain wastewater from the on-site storage pond by opening a discharge pipe located at the base of the pond. Approximately 32 former workers and an unknown number of trespassers may have been exposed to contaminants before the storage pond was closed, backfilled, and capped. Process water used for cooling was recirculated through a cooling pond east of the treating cylinder. A surface water sample collected from the cooling pond revealed the presence of PCP. Exposures would have resulted from direct contact with or incidental ingestion of contaminated surface water.
Surface Water and Sediment
Contaminated wastewater from the on-site storage and cooling ponds was released into West and East Mineral creeks, which drain into County Club Estates Lake and subsequently into a private lake (Phillips Lake). PCP and several dioxins and furans have been detected at elevated levels in sediment and surface water samples from Phillips Lake, County Club Lake, and the intermittent creeks leading from the facility. The drained pond located downstream from the facility contains high levels of PCP and dioxins and furans. People were likely intermittently exposed to contaminants in surface water and sediments during wading, swimming, boating, or other recreational activities on the lakes, creeks, or tributaries. The primary routes of exposure are dermal contact and incidental ingestion.
The consumption of contaminated fish is a past, present, and future completed exposure pathway for this site. Fish have been contaminated with PCP, dioxins, and furans directly through water and sediment and indirectly through their aquatic food chain. In 1988, MDEQ issued an advisory against fishing for commercial purposes and against consuming fish caught in County Club Lake because of the high levels of dioxins detected in fish tissue samples. Historically, fish collected from County Club Lake and Mineral Creek contained elevated levels of dioxins and furans in their tissues. Although a fish advisory had been in place for County Club Lake since 1987, there is anecdotal evidence that people continued to fish in the lake. It is likely that some of the fish caught were eaten. The most recent fish samples collected by MDEQ in July 2000 found that dioxin levels in fish are decreasing. Results of fish samples collected and analyzed since 1997 prompted the State of Mississippi to recently lift the fish consumption advisory that had been in effect since 1987.
Potential Exposure Pathways
Residents in the community adjacent to the site, or who walk on the pedestrian path next to the site, may be exposed to contaminants in surface soil. Contaminants from the facility may have migrated off-site via wind or surface water runoff and been deposited in residential yards, playgrounds, or the walking path. Direct dermal contact with and incidental ingestion of soil are the primary routes of exposure by this pathway. The nearest residence is approximately 100 feet from the site. Other residential properties are south of the site. The walking path is within 30 feet of the site. Information is insufficient to evaluate the possibility of current or past exposures to off-site surface soil. To date, no off-site surface soil samples have been collected.
Current data show elevated, but decreasing, concentrations of dioxins and furans in fish collected below County Club Lake. However, it is not known how far downstream the fish are contaminated. The fish advisory applies only to County Club Lake. Other downstream water bodies, such as the Bowie and Leaf rivers, are also fished for consumptive purposes. It is possible that fish being caught in the lower reaches of Mineral Creek or at the Bowie River are contaminated and are being consumed by people unaware of such potential contamination. Data are insufficient to define the magnitude of potential exposures by this pathway.
Nearby residents who use private wells for potable water may be exposed to contaminants in groundwater. Analytical data from groundwater samples collected from on-site monitoring wells have indicated the presence of PCP and polychlorinated dioxins and furans. The nearest private well was sampled for semi-volatile organic compounds and no contaminants were detected, although not all site-related contaminants were analyzed. The potential exists for contaminants to migrate off-site and contaminate private or municipal wells. If residential homes are built on the site in the future, the potential exists for a resident to install a private well for domestic purposes in the contaminated groundwater.
In 1993, ATSDR released a petitioned public health assessment for County Club Lake Estates, which is now known as the Davis Timber Company site. The petitioned PHA described the possibility of an increased risk of cancer in people who consume fish regularly from Country Club Lake because of dioxin and furan contamination in fish tissue. The petitioned PHA also identified on-site groundwater and dioxin contamination as a possible concern for people who might use groundwater from the site. In addition the petitioned PHA identified pentachlorophenol contamination in fish, off-site sediment, off-site surface water, and on-site soil as a health concern.
To supplement the health discussions previously provided in the petitioned PHA, this discussion focuses on new environmental data that have been collected since the petitioned PHA was released in 1993. The entire petitioned PHA can be found in Appendix D.
Dioxins and Fish
The 1993 petitioned public health assessment determined that it was not safe to eat fish from County Club Estates Lake. This public health assessment reviews current fish levels of dioxin and furans (based on TCDD TEQs) and evaluates whether it is currently safe to eat fish from Country Club Lake. A discussion of the health effects from historical exposures (mid-late 1970s to late 1980s) to contaminated fish from County Club Lake is presented in the Community Health Concerns Section, question #3, beginning on page 18.
The most significant recently collected data are for fish MDEQ collected from County Club Lake on July 18, 2000; samples of the fish were measured for concentrations of dioxin and furans. The data are summarized in Table 3 (Appendix B). The increasing amount of dioxin and furan contamination occurs with increasing weight of the fish and probably results from their increased diet of smaller fish that contain dioxin and furans.
Table A (on page 15) shows the estimated doses for people who eat largemouth bass that weigh over 4 lbs. Several questions have to be answered to determine whether it is safe to eat fish from Country Club Lake. These questions are listed here:
- Is it safe for children to eat fish?
- Is it safe for adults to eat fish?
- Will eating just one fish meal cause harmful effects?
- Will eating many fish meals over months or years cause harmful effects?
EPA calculated the amount of dioxin and furans in the tissue to be 5.33 pg TCDD TEQ per gram of fish fillet. Using the 5.33 pg/g TEQ concentration for the largemouth bass composite sample with an average specimen weight of 4.3 lbs. (Table 3, Appendix B), ATSDR estimated the amount of TEF intake for a varying number of fish meals over the year and for several age groups. Table A shows the estimated dose compared with ATSDR's Minimal Risk Level (MRL), a guideline below which noncancerous harmful effects are not likely. For instance, ATSDR has developed an acute oral MRL of 200 pg TCDD per kilogram body weight per day (or 200 pg/kg/day) for up to 14 days of exposure. As can be seen in Table A, none of the estimated doses for a single fish meal or for 3 fish meals a week will exceed ATSDR's acute oral MRL. This means that noncancerous, harmful effects are unlikely. A similar comparison can be made for an estimated monthly dose where ATSDR assumes that someone will eat 2 fish meals a month for several months. None of the estimated doses in Table A exceed ATSDR's intermediate oral MRL of 50 pg/kg/day. This means that noncancerous harmful effects are unlikely should someone eat fish from the lake for up to a year.
|Table A. Doses Based on Tissue Concentration of 5.33 pg/g.|
|Amount of fish eaten during one meal||1-time Dose(1)
|Adult male||12 oz||26||11||1.7||0.9|
|Adult female||8 oz||25||11||1.6||0.8|
|Elementary school child||6 oz||26||11||1.7||0.9|
|Preschool child||4 oz||38||16||2.5||1.3|
|Preschool child||2 oz||19||8||1.3||0.6|
|Minimal Risk Level||200
1. Dose from eating one fish meal
2. Dose from eating 3 fish meals in one week. Dose is averaged for a week.
3. Dose from eating 2 fish meals in one month. Dose is averaged over a month.
4. Dose from eating 1 fish meal a month for a year. Dose is averaged over a year.
As for chronic exposures of greater than 1 year, the estimated doses are at or below ATSDR's chronic oral MRL of 1 pg/kg/day. Only the estimated dose for a preschool child who eats 4 ounces of the most contaminated fish once a month for over a year exceeds the chronic oral MRL. The estimated dose is 1.3 pg/kg/day compared with the MRL of 1 pg/kg/day. The 1.3 pg/kg/day dose is 100 times lower than the dose that caused altered social behavior in monkeys exposed to dioxin at 120 pg/kg/day for 16 months. Because there is a 100-fold difference in dose, harmful effects are not expected in children who currently eat the most contaminated bass from the lake.
The previous discussion was developed using the highest TCDD TEQs level for the largest fish caught from Country Club Lake. Based on samples collected in 1997 and 2000, largemouth bass caught from the lake are typically much smaller, weighing about 1 lb. They also have much lower levels of TCDD TEQs, ranging from 0.076 to 1.3 pg/g. Bluegill and other sunfish are likely to be more abundant in this lake, and thus more likely to be caught. The 1997 sample of bluegill indicated only slightly higher TEQs (0.85 pg/g). The smaller bass, bluegill, and other fish are the types that people are more likely to eat repeatedly, especially when considering chronic exposure over many years. Using the TEQ level from these fish, the estimated doses will be at least 5 to 10 times lower than what was estimated in Table A, which used the fish sample with the highest TCDD TEQs. This means that for those people who eat typical fish from the lake all of the estimated doses will be below ATSDR's acute, intermediate, and chronic MRLs and that noncancerous harmful effects would be unlikely.
While there is some evidence that dioxins cause cancer in humans, the most reliable evidence comes from rodent studies involving rats and mice. The most sensitive study showed that 7,000 pg/kg/day in rats, 2 days a week for 2 years, produced thyroid cancer. At higher exposure levels in mice and rats (71,000 pg/kg/day and 300,000 pg/kg/day), cancers of the liver and lung as well as lymphoma were produced. When evaluating the possibility of cancer in residents, it is necessary to estimate the average dose over decades of exposure. This becomes difficult because TCDD levels are decreasing with time, with a 20-fold decrease in levels from 1990 to 2000.
Using TCDD TEFs for samples collected in 2000 that are considered indicative of fish typically caught from Country Club Lake, exposure to TCDD TEQs is estimated to be 0.06 pg/kg/day. This estimated dose is about 120,000 times lower than the level shown to cause cancer in the most sensitive rodent study, and is about 16 times lower than ATSDR's MRL of 1 pg/kg/day for noncancerous effects. It seems unlikely that eating fish from Country Club Lake will increase the risk of cancer or noncancer effects from dioxins.
Pentachlorophenol and Surface Water
In 1995, sediment samples from West Mineral Creek at several locations near the site contained pentachlorophenol (PCP) levels of 80, 90, and 360 ppb (see Table 1 in Appendix B). The only people who will be exposed are children and adults who might have some contact with the sediments while walking or playing along the stream. The level of PCP in the sediment is not harmful to people.
Dioxin and Furans in Sediments
Dioxin and furans reported as TCDD TEQs have been found in sediment from East and West Mineral creeks (Table 2, Appendix B). The highest level detected was 2.4 µg/kg (or ppb) TCDD TEQs in 1990 in sediment from West Mineral Creek, which still showed similar TCDD TEQ levels in 1991. TCDD TEQs measured in 1992 and 1995 samples were about 50% less than those observed in 1990 and 1991. In addition, sediment from East Mineral Creek also contains TCDD TEQs, with the highest level reported being 1.8 ppb in 1991. These levels will not cause harmful effects in children and adults who trespass on the property because the estimated amount of exposure is below ATSDR's acute, intermediate, and chronic MRLs for 2,3,7,8-TCDD.
Uncertainty exists in this conclusion, however, because only a few soil samples have been collected from the site itself, and sediment samples were not collected from East Mineral Creek in 1992 and 1995. One soil sample collected near the wood treating facility contained TCDD TEQs at 42 ppb. This level of TCDD TEQs is above the typical clean-up level of 1 ppb that has been used for residential situations. While the Davis Timber site has not been converted to a residential area, that is a possible future use of the property. Several housing developments are near the site.
Local health outcome data were not considered because current exposures are not likely to cause harmful effects in residents who trespass on the site or in residents who eat fish from the County Club Lake.
ATSDR pays special attention to children because they can be uniquely vulnerable to toxic chemicals. This unique vulnerability results sometimes from having immature, developing organs and sometimes from having higher exposures because of increased contact with the environment. To ensure that children are protected, ATSDR estimated dioxin exposure in children who might eat contaminated fish from Country Club Lake. This evaluation led to the conclusion that harmful effects might occur in some children who ate contaminated fish from the lake in the 1970s and 1980s. (See the answer to question # 3 in the next section.)
ATSDR held a public meeting on November 8, 2001, to gather health concerns from residents and community members. Staff from EPA attended to update residents on the status of the remedial investigation at the site. About 10 residents attended the meeting.
The following is a list of health concerns or questions posed by the residents either during the meeting or in letters/conversations with ATSDR staff.
- Is it safe for children to swim or canoe in County Club Lake?
- Are there any concerns about children playing in and around the creek area in the past or present?
- What are the potential health effects of consuming fish caught in the Country Club Lake?
- Is it safe for me to eat vegetables grown in my yard?
It is safe for children and adults to use a canoe or any other boat in the lake because little to no contact will occur with the water.
ATSDR has reviewed the available environmental data from the lake and determined that information is insufficient to determine if swimming in the lake is currently safe because no current water samples are available. It seems unlikely, however, that dioxin and PCP would currently be at sufficient levels in lake water to be harmful because so many years have passed since Davis Timber was operating and dumping PCP and dioxins into East and West Mineral creeks. Very small amounts of dioxins were detected in several sediment samples from the lake; however, no PCP was detected. The small amount of dioxin in lake sediment is not harmful to children or adults who might come in contact with lake sediment.
Children who played in and around the East and West Mineral creeks in the past might have been exposed to small amount of contaminants if their hands got dirty or wet and they subsequently put their hands in their mouth. From the small amounts of dioxins and PCPs that have been found in runoff along the creeks, it seems unlikely that children could have gotten sick from these brief, limited exposures.
Currently, eating fish typically caught from the lake poses no adverse health effects since the levels of dioxins in the fish are not harmful. This conclusion is based on the discussion in the Public Health Implications section about dioxins and fish and the assumptions presented in Table A. Basically, ATSDR considered the amount of dioxin exposure from eating varying amounts of fish. Since subsistence fishing does not occur at this lake, ATSDR assumed that the most likely range of exposures occurred from eating up to 12 fish a year and using the highest dioxin levels detected in the most recently caught fish.
Historically, people who ate fish from County Club Lake repeatedly from the mid-late 1970s to the late 1980s are at risk of experiencing harmful effects. Davis Timber started its wood treatment operations in 1972, and it probably took several years for dioxins to migrate from the site to the lake and for fish to build up dioxin in their flesh. In 1987, EPA measured TCDD TEQ in fillet largemouth bass at 103 picograms TEQs per gram (pg/g) of fish fillet. TCDD TEQs were measured at 156.7 pg/g in a composite whole body sample of hybrid sunfish. These are the highest dioxin levels measured in fish from the lake and levels have been dropping since 1987, probably because dumping of waste from Davis Timber stopped and because natural degradation of dioxin occurred. The estimated exposure to dioxin in residents who ate 12 fish meals from the lake throughout the year is about 6 times lower than the amount of exposure in monkeys exposed for 16 months that resulted in altered social behavior. In addition, children who ate contaminated fish from the lake in the 1970s and 1980s might be at increased risk of mild damage to their immune system. Experiments with mice have shown that low levels of dioxin can cause a decreased resistance to viral infection and suppressed immune activity.
The estimated amount of exposure in residents who ate 12 fish meals a year from the lake for many years is also about 350 times lower than the exposure in rats that resulted in thyroid cancer and about 3,500 times lower than the exposure in rats that caused liver cancer.
Based on these comparisons, some adults who repeatedly ate the most contaminated fish from the lake from the 1970s and 1980s might be at risk of altered social behavior and an increased possibility of thyroid and liver cancer. In addition, some children would have been at increased risk of mild damage to their immune system.
Results of fish samples collected and analyzed since 1997 prompted the State of Mississippi to recently lift the fish consumption advisory that had been in effect since 1987. We recommend that fish larger than 6 lbs. that are caught from the lake be provided to the Mississippi Department of Environmental Quality for testing because very few fish in this size range have been collected from the lake.
Yes, it is safe for you to grow and eat vegetables from your garden. Dioxins and PCP are not likely to be taken up by plants to any significant amount, if at all. Also, there is no evidence that residential yards are contaminated with dioxin and PCP.
The Davis Timber Company site is a current public health hazard because physical hazards on the site could cause bodily injuries to children and adults who trespass. In addition to trip and fall hazards, numerous boards with nails and broken glass are scattered around the site. The hazards at this site are compounded by buildings that are also dilapidated.
The County Club Lake was a past public health hazard (before 1990) because residents who ate contaminated fish from the lake were exposed to dioxin and furans. The estimated amount of dioxin exposure in some residents who repeatedly ate fish from the lake might have increased the possibility of altered social behavior, increased the possibility of thyroid cancer, and caused mild damage to the immune system.
Analysis of the most recent fish samples collected by MDEQ in July 2000 showed that dioxin levels in fish are decreasing. Results of fish samples collected and analyzed since 1997 prompted the State of Mississippi to recently lift the fish consumption advisory that had been in effect since 1987.
The Davis Timber Company site is a potential future public health hazard if residential homes and/or playgrounds are constructed on the property. In these settings, children and adults would have greater contact with contaminated on-site soil and sediment.
Information is insufficient about the degree of surface and subsurface soil contamination on the site. If on-site soils are contaminated, then off-site migration of contaminants can occur.
- Collect surface (0 to 3 inches) and subsurface soil samples from on-site areas and surface soil samples in nearby residential yards to determine the extent of soil contamination. Analyze for dioxins and furans as well as semi-volatile compounds, such as pentachlorophenol and its breakdown products.
- Collect surface water samples from East and West Mineral creeks to determine if PCP and dioxins are migrating from the site. Samples should be collected shortly after heavy rains since heavy rains flush contaminants from the soil.
- Characterize the extent of contamination to on-site and off-site groundwater. Public and private drinking water wells near the site should be analyzed for PCP and polychlorinated dioxins and furans.
- Continue to collect fish samples from County Club Lake and other lakes where people may fish for consumption. Consider sampling fish from waters of Mineral Creek and the Bowie River to define the geographic range of contaminated fish.
- Limit access to the site to lessen the threat posed by physical hazards.
- Provide to the Mississippi Department of Environmental Quality for testing any fish larger than 6 lbs. that is caught from the County Club Lake. Very few fish of this size or larger have been collected from the lake. Fish larger than 6 lbs. may contain higher concentrations of contaminants than the smaller fish that have typically been sampled.
- US Environmental Protection Agency. HRS documentation record. Davis Timber Company, Hattiesburg, Lamar County, Mississippi, January 2000.
- US Environmental Protection Agency. Region 4, Science and Ecosystem Support Division. Final remedial investigation work plan, Davis Timber site. Athens, Georgia, April 13, 2000.
- Michael Slack. Mississippi Department of Environmental Quality, CERCLA Division. Letter to Lt. Mark Marshall, USPHS, Remedial Project Manager, USEPA, June 26, 1995.
- US Environmental Protection Agency. Part II- HRS final rule. Hattiesburg, Mississippi, Forrest County, December 14, 1990.
- American Laboratories and Research Services, Inc. Polychlorinated dibenzo-p-dioxin and dibenzofuran contaminants in Dr. Phillips' lake, report no. 1. March 1990.
- Agency for Toxic Substances and Disease Registry. Petitioned public health assessment. Country Club Lake Estates, Hattiesburg, Forrest County, Mississippi. January 19, 1993.
- Kenneth Whitten. Mississippi Office of Pollution Control, Hazardous Waste Division. Site investigation, phase I, Davis Timber Company, Hattiesburg, Mississippi, July 19, 1991.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for chlorinated dibenzo-p-dioxins (update). Atlanta: US Department of Health and Human Services; 1998 Dec.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for pentachlorophenol (draft update). Atlanta: US Department of Health and Human Services; 1999 Aug.
- Phone conversation with Al Gibson, Biologist, Mississippi State Labs. May 8, 2001.
- Mississippi Department of Environmental Quality. Fish Advisory Workgroup. Fish sampling data, July 18, 2000.
- State of Mississippi. Press release. June 26, 2001. Majority of Mississippi waters free from DDT; be aware not alarmed is message of MDEQ fish safety study. Available from Linda Vaught (601.961.5053) and Phil Bass (601.961.5100).
- State of Mississippi Fact Sheet. August 8, 2001. Delta Fish Advisory. Available from http://www.deq.state.ms.us/newweb/homepages.nsf .
- US Environmental Protection Agency. Interoffice memorandum from Earl Bozeman to Brian Farrier. Ecological risk review for Davis Timber Company site, Hattiesburg, Mississippi MSD046497012. June 23, 1995.
Authors of Report:
Environmental Health Scientist
Superfund Site Assessment Branch
David Mellard, Ph.D.
Superfund Site Assessment Branch
W. Allen Robison, Ph.D.
Superfund Site Assessment Branch
ATSDR Community Involvement Coordinator:
Rose B. Jackson
Health Communications Specialist
Community Involvement Branch
ATSDR Regional Representative
|Sample Location||PCP Concentration (µg/kg)||Comparison Value (µg/kg)|
|WMC upstream of DTC||ND||ND||2,000|
|WMC at PCP lagoon/on-site storage pond||16,000||90||2,000|
|WMC below drained pond||NS||360||2,000|
|WMC between drained pond & CCL||NS||80||2,000|
|WMC at entry to CCL||NS||ND||2,000|
|CCL near dam||NS||ND||2,000|
|MC below CCL dam||NS||ND||2,000|
|MC downstream of CCL||NS||ND||2,000|
WMC - West Mineral Creek
DTC - Davis Timber Company
CCL - County Club Lake
MC - Mineral Creek
ND - Not detected
NS - Not sampled
µg/kg - parts per billion (ppb)
1Data extracted from June 23, 1995, document "Ecological Risk Review for Davis Timber Company Site, Hattiesburg, Mississippi MSD046497012," prepared by EPA.
|WMC upstream of DTC||NS||NS||0.001||0.0005|
|WMC at PCP lagoon/on-site storage pond||NS||0.2||NS||0.7|
|WMC below drained pond||2.4||2.2||1.1||1.4|
|WMC between drained pond & CCL||NS||NS||NS||0.1|
|WMC at entry to CCL||NS||NS||NS||0.009|
|CCL near dam||0.2||0.2||NS||0.0007|
|MC below CCL dam||NS||NS||NS||0.00068|
|MC downstream of CCL||NS||NS||NS||0.001|
|EMC downstream of DTC||0.9||1.8||NS||NS|
WMC - West Mineral Creek
EMC - East Mineral Creek
DTC - Davis Timber Company
CCL - County Club Lake
MC - Mineral Creek
ND - Not detected
NS - Not sampled
µg/kg - parts per billion (ppb)
1Data extracted from June 23, 1995, document "Ecological Risk Review for Davis Timber Company Site, Hattiesburg, Mississippi MSD046497012," prepared by EPA.
|DATE||SPECIES/Average Weight (lbs)||SAMPLE||TOTAL TEQ (pg/g)|
|7/18/00||Largemouth bass/4.3 lbs.||Fillet Composite||5.33|
|7/18/00||Largemouth bass/0.88 lbs.||Fillet Composite||0.4|
|7/18/00||Largemouth bass/0.59 lbs.||Fillet Composite||0.076|
|7/18/00||Largemouth bass/0.50 lbs.||Fillet Composite||0.2|
|7/18/00||Bluegill/0.29 lbs.||Fillet Composite||0.85|
|1997||Largemouth bass/0.46 lbs.||Fillet Composite||1.3|
|1997||Largemouth bass/0.80 lbs.||Fillet Composite||0.7|
|1997||Channel catfish/7.3 lbs||Fillet||21.0|
|12/87||Largemouth bass||Fillet Composite||103.3|
|12/87||Hybrid sunfish||Whole Composite||156.7|
|Source||Environmental Media||Point of Exposure||Route of Exposure||Exposed Population|
|Surface Soil||Davis Timber Company||Surface Soil||On-site surface soils||Dermal contact
|Wastewater||Davis Timber Company||Wastewater||On-site holding ponds||Dermal contact
|Mineral Creek and Country Club Lake||Davis Timber Company||Surface Water
Country Club Lake
|Users of Mineral Creek and surrounding lakes||Past
|Food Chain||Davis Timber Company||Fish||Residence||Ingestion||People eating fish from Country Club Lake||Past
|Source||Environmental Media||Point of Exposure||Route of Exposure||Exposed Population|
|Surface Soil||Davis Timber Company||Surface Soil||Nearby yards
Users of walking path
|Food Chain||Davis Timber Company||Fish||Residence||Ingestion||People eating fish caught in lakes downstream of Country Club Lake||Past
|Groundwater||Davis Timber Company||Groundwater||Water faucets||Dermal contact
|Nearby users of groundwater||Past
Click the following link for the County Club Lake Estates Petitioned PHA: http://www.atsdr.cdc.gov/HAC/PHA/country/ccl_toc.html