Skip directly to search Skip directly to A to Z list Skip directly to site content
PUBLIC HEALTH ASSESSMENT

CHEVRON CHEMICAL CO. (ORTHO DIVISION)
ORLANDO, ORANGE COUNTY, FLORIDA

ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

In this section, we review the environmental data collected at the site, evaluate sampling adequacy, and select contaminants of concern. Also in this section, we list the maximum concentration and detection frequency for the contaminants of concern in the various media (that is, water, soil, and air). We select contaminants of concern based on the following factors:

  1. Concentrations of contaminants on and off the site: although background concentrations are useful in determining if contaminants are site-related, we only eliminate contaminants from further consideration if both the background and on-site concentrations are below standard comparison values. This is necessary to assess the public health risk to all contaminants detected, whether site related or not.
  2. Field data quality, laboratory data quality, and sample design.
  3. Community health concerns.
  4. For complete and potential exposure pathways, comparison of maximum concentrations with published ATSDR standard comparison values: in selecting contaminants of concern, we did not consider contaminant concentrations in eliminated pathways such as on-site soil and ground water. The ATSDR's published standard comparison values are media-specific concentrations used to select contaminants for further evaluation. They are not used to predict health effects or to set clean-up levels. Contaminants with media concentrations above an ATSDR standard comparison value do not necessarily represent a health threat, but are selected for further evaluation. Contaminants with media concentrations below an ATSDR standard comparison value are unlikely to be associated with illness and are not evaluated further, unless there is a specific community concern about the contaminant.
  5. For complete and potential exposure pathways, comparison of maximum concentrations with toxicological information published in documents called ATSDR toxicological profiles. These profiles are chemical specific and summarize toxicological information found in the scientific literature.

We used the following ATSDR standard comparison values (ATSDR 1994), in order of priority, to select contaminants of concern:

  1. EMEG--Environmental Media Evaluation Guide--is derived from the ATSDR's Minimal Risk Level (MRL) using standard exposure assumptions, such as ingestion of two liters of water per day and body weight of 70 kg for adults. MRLs are estimates of daily human exposure to a chemical likely to be without an appreciable risk of noncancerous illnesses, generally for a year or longer.
  2. CREG--Cancer Risk Evaluation Guide--is calculated from the EPA's cancer slope factors, is the contaminant concentration that is estimated to result in no more than one excess cancer per one million persons exposed over a lifetime.
  3. RMEG--Reference Dose Media Evaluation Guide--is derived from the EPA's Reference Dose (RfD) using standard exposure assumptions. RfDs are estimates of daily human exposure to a chemical likely to be without an appreciable risk of noncancerous illnesses, generally for a year or longer.
  4. LTHA--Lifetime Health Advisory for Drinking Water--is the EPA's estimate of the concentration of a drinking-water contaminant at which illnesses are not expected to occur over lifetime exposure. LTHAs provide a safety margin to protect sensitive members of the population.

Using the methodology described above, we selected the pesticides chlordane, DDT, DDE, dieldrin, and heptachlor epoxide as contaminants of concern at this site. We only use the ATSDR standard comparison values to select contaminants of concern for further consideration. Identification of a contaminant of concern in this section does not necessarily mean that exposure will be associated with illnesses. Identification serves to narrow the focus of the public health assessment to those contaminants most important to public health. When we selected a contaminant of concern in one medium, we also reported that contaminant in all other media. We evaluate the contaminants of concern in subsequent sections and decide whether exposure has public health significance.

In Tables 1 through 10, Appendix B, we summarize the environmental sampling data for five selected contaminants of concern.

To identify industrial facilities that could contribute to the contamination near this site, we searched the 1987 to 1992 EPA Toxic Chemical Release Inventory (TRI) data bases. The EPA developed TRI from the chemical release information (air, water, and soil) provided by certain industries. The Chevron Chemical Superfund site is in the 32804 and 32808 zip code areas. Between 1987 and 1992 six facilities in these two zip codes areas reported chemical releases. These releases included hydrochloric acid, sodium hydroxide, nitric acid, phosphoric acid, ammonia, glycol ethers, and isopropyl alcohol. Citrus Central Orlando Can Division at 1900 W. Hampshire Avenue reported the release of approximately 72,000 pounds of toluene into the air between 1988 and 1990. None of these releases, however, are likely to affect the residents near the Chevron Chemical site.

In this public health assessment, we first discuss the contamination that exists on the site and then the contamination that occurs off the site.

A. On-site Contamination

For this public health assessment, we define "on-site" as the property boundary as shown in Figure 4. We divide on-site surface soil, subsurface soil, and ground-water samples into those collected before and after the 1992 cleanup. We characterize the on-site air quality based on measurements taken at the site boundary during the 1992 cleanup.

On-Site Surface Soil (0-1 Foot) Before 1992 Cleanup

In 1989 EPA contractors collected two surface soil samples (depth not specified) from the site (Figure 5, Appendix A). They found pesticides and petroleum solvents (NUS 1990). In October 1990 Chevron contractors collected 10 more on-site surface soil samples (0 to 6 inches deep) (Figures 6 and 7, Appendix A). They found pesticides and petroleum solvents (Brown and Caldwell 1990a).

Table 1 (Appendix B) lists the maximum concentrations of the five contaminants of concern found in the surface soil before the 1992 site cleanup. We consider surface soil sample CC-SS-01 representative of the background surface-soil quality. EPA contractors collected this sample 85 feet southwest of the site (NUS 1990). For this public health assessment, Chevron and EPA adequately characterized the on-site surface soil quality before the 1992 cleanup.

On-Site Surface Soil (0-1 Foot) After 1992 Cleanup

Since the 1992 cleanup, neither Chevron nor EPA has collected any surface soil samples. In 1992, after removing the contaminated soil but before replacing with clean fill, Chevron contractors collected and analyzed between 200 and 300 confirmation soil samples (depth not specified). Since they collected these samples during the soil excavation but before adding clean fill, we assume these samples were subsurface (>1 foot deep). Chevron filled the excavated areas with clean soil and covered them with sod. Because a fence surrounds the site and grass covers it, we do not recommend additional surface soil samples. Additional surface soil samples may be necessary in the future, however, if the site use changes.

On-Site Subsurface Soil (> 1 Foot) Before 1992 Cleanup

In 1981 Chevron contractors collected three 10.5 feet deep subsurface soil samples (Figure 8, Appendix A) and found pesticides (Dames & Moore 1983). We did not include these results in our assessment, however, since they reported the pesticide concentrations in terms of weight per volume of soil extract (mg/L). Since the report did not detail the extraction procedure, we cannot determine the actual soil concentrations.

In 1989 EPA contractors collected five subsurface soil samples (depth not specified) from the site (Figure 5, Appendix A). They found pesticides and petroleum solvents (NUS 1990). In October 1990 Chevron contractors collected 28 on-site subsurface soil samples (1.5 to 8 feet deep) (Figures 6 and 7, Appendix A). They found pesticides and petroleum solvents (Brown and Caldwell 1990a).

During the 1992 site cleanup, Chevron contractors collected and analyzed between 200 and 400 samples (depth not specified) of the soil they excavated and removed (Figure 9, Appendix A)(Brown and Caldwell 1992). Since these samples were collected during the soil excavation, we assume that most were subsurface (>1 foot deep). We used summary data from the Removal Action Report (Brown and Caldwell 1992) since we were unable to obtain the raw data.

In Table 2 (Appendix B) we list the maximum concentrations of the five contaminants of concern found in the subsurface soil before the 1992 site cleanup. We consider subsurface soil sample CC-SB-01 representative of the background subsurface-soil quality. EPA contractors collected this sample 85 feet southwest of the site (NUS 1990). For this public health assessment, Chevron and EPA adequately characterized the on-site subsurface soil quality before the 1992 cleanup.

On-Site Subsurface Soil (> 1 Foot) After 1992 Cleanup

In 1992, after removing the contaminated soil but before replacing with clean fill, Chevron contractors collected and analyzed between 200 and 300 confirmation subsurface-soil samples (depth not specified) (Figure 10, Appendix A). They found reduced concentrations of pesticides and petroleum solvents (Brown and Caldwell 1992; Task 1994a).

In Table 3 (Appendix B) we list the maximum concentrations of the five contaminants of concern remaining in the subsurface soil after the 1992 site cleanup. We consider subsurface soil sample CC-SB-01 representative of the background subsurface-soil quality. EPA contractors collected this sample 85 feet southwest of the site (NUS 1990). For this public health assessment, Chevron and EPA adequately characterized the on-site subsurface soil quality after the 1992 cleanup.

On-Site Surficial-Aquifer Ground Water Before 1992 Cleanup

In 1981 and 1982, Chevron contractors collected and analyzed ground-water samples from eight surficial-aquifer monitor wells (Figure 8, Appendix A). They found elevated pesticide levels (Dames & Moore 1983). Five years later in 1987, contractors for Southeast Investment Properties collected ground-water samples from seven temporary surficial-aquifer monitor wells (Figure 11, Appendix A). They found petroleum solvent contamination. They did not analyze these samples for pesticides or other contaminants (Jammal & Associates 1987). In 1989, contractors for the EPA collected and analyzed ground-water samples from five temporary surficial-aquifer monitor wells on site and one temporary background surficial-aquifer monitor well (Figure 5, Appendix A). These contractors found elevated levels of pesticides and petroleum solvents (NUS 1990). In September 1990, contractors for Chevron collected and analyzed ground-water samples from 14 surficial-aquifer monitor wells (Figure 12, Appendix A). They found elevated concentrations of pesticides and petroleum solvents (Brown and Caldwell 1990a). In September 1991 Chevron contractors collected 17 ground-water samples from the surficial aquifer on site using a Hydropunch® (locations not specified). One month later, they resampled the existing 14 on-site surficial-aquifer monitor wells and one newly installed well cluster (Figure 12, Appendix A). They found elevated levels of pesticides and petroleum solvents (Brown and Caldwell 1992).

In Table 4 (Appendix B) we list the maximum concentrations of the five contaminants of concern found in the surficial aquifer before the 1992 site cleanup. We consider ground-water samples from monitor wells MW-A and MW-D (in the southeast and southwest corners of the site) and CC-TW-01 (85 feet southwest of the site) as representative of the background quality in the surficial aquifer (NUS 1990). We assume monitor wells less than 35-feet-deep to be in the surficial aquifer. For this public health assessment, Chevron and EPA have adequately characterized the on-site surficial-aquifer ground-water quality before the 1992 cleanup.

On-Site Surficial-Aquifer Ground Water After 1992 Cleanup

As part of the 1992 site clean-up, Chevron contractors collected and treated about 126,000 gallons of contaminated ground water from the surficial aquifer on site. In April 1993, Chevron contractors collected and analyzed ground-water samples from the five remaining on-site monitor wells (Chevron 1993b). In September 1993, Chevron contractors collected and analyzed ground-water samples from the five existing and ten new on-site surficial-aquifer monitor wells (PTI 1993). Figure 13 (Appendix A) shows the locations of these on-site surficial-aquifer monitor wells.

Table 5 (Appendix B) lists the maximum concentrations of the five contaminants of concerns found in the surficial aquifer since the 1992 site cleanup. We consider ground-water samples from monitor wells MW-A and MW-D (in the southeast and southwest corners of the site) and CC-TW-01 (85 feet southwest of the site) as representative of the background quality in the surficial aquifer (NUS 1990). In this assessment, we assume monitor wells less than 35-feet-deep to be in the surficial aquifer. For this public health assessment, Chevron and EPA have adequately characterized the quality of the on-site surficial aquifer ground water remaining after the 1992 cleanup.

On-Site Air

There are no on-site air monitoring data before 1992. During the 1992 site cleanup, Chevron contractors monitored air quality at two places along the northern site boundary near the Armstrong Trailer Park. From February 2, 1992 to April 9, 1992 they collected and analyzed 57 air samples for organochlorine pesticides and PCBs (Brown and Caldwell 1992). They only detected chlordane and DDD. Both pesticides were above their comparison values (Table 6, Appendix B).

B. Off-site Contamination

For this public health assessment, we define "off-site" as the area outside the property boundary shown in Figure 4. We divide off-site surface soil contamination into samples collected before and after the 1994 surface soil removal from the Armstrong Trailer Park. We assume off-site air quality to be similar to that at the site boundary during the 1992 site cleanup. Neither the EPA nor Chevron has collected or analyzed water samples from nearby Lake Fairview. Ground-water monitoring data show that contamination has not reached Lake Fairview.

Off-Site Surface Soil (0-1 Foot) Before 1994 Removal

From September 22 to 28, and again on November 17, 1993, Chevron contractors collected 50 surface-soil samples from the Armstrong Trailer Park north of the site (Figure 14, Appendix A). Chevron contractors collected most of these soil samples from the low area in the back (west end) of the trailer park. They analyzed these samples for organochlorine pesticides (PTI 1994). Most of these soil samples were from the ground surface (0-3 inches deep) although some were one foot deep. Chevron found elevated levels of chlordane (Table 7, Appendix B). For comparison, the maximum concentration of chlordane in the trailer park soil--370 mg/kg--is less than the recommended soil concentration for termite control--512 mg/kg--(Chevron 1993a). We consider sample #1 (September 1993) taken from the front (east side) of the trailer park to represent background surface-soil quality. For this public health assessment, these samples are adequate to characterize the off-site surface-soil quality before the 1994 removal.

Off-Site Surface Soil (0-1 Foot) After 1994 Removal

In March and April 1994, Chevron contractors removed about 200 square yards of pesticide-contaminated soil from the Armstrong Trailer Park. Most of the contaminated soil was in the southwest corner of the trailer park but there were localized pockets in other areas. Following this removal, Chevron contractors collected confirmation soil samples (Table 8, Appendix B) (Chevron 1994a and 1994b). For this public health assessment, these samples adequately characterize the remaining off-site surface soil quality.

Off-Site Surficial Aquifer Ground Water (5-32 Feet Deep)

Since the City of Orlando supplies water to homes and business in the area, ground water is not a source of drinking water. Specifically, the City of Orlando supplies water to all of the residents of the Armstrong and 441 Trailer Parks (the area over the contaminated ground water) (Orange CPHU 1993).

In October 1991 and again in April 1993, Chevron contractors collected and analyzed ground-water samples from two monitor well clusters in the Armstrong Trailer Park north of the site (Brown and Caldwell 1992, Chevron 1993b). In September 1993, Chevron contractors collected and analyzed ground-water samples from these two monitor well clusters. They also sampled five monitor wells north and east of the site (PTI 1993). Figure 13 (Appendix A) shows the locations of these off-site surficial-aquifer monitor wells. They found elevated levels of chlordane and DDD in one monitor well in the Armstrong Trailer Park (Table 9, Appendix B).

We consider ground-water samples from monitor wells MW-A and MW-D (in the southeast and southwest corners of the site) and CC-TW-01 (85 feet southwest of the site) representative of the background quality in the surficial aquifer (NUS 1990). We assume monitor wells less than 35 feet deep are in the surficial aquifer. For this public health assessment, Chevron and EPA have adequately characterized the surficial-aquifer ground-water quality off site.

Off-Site Air

There is no off-site air monitoring data before 1992. Therefore, we cannot assess the public health threat from inhalation of site-related contaminated dust before 1992. From February 2 to April 9, 1992 Chevron contractors collected 57 air samples from the northern site boundary near the Armstrong Trailer Park. They analyzed these samples for organochlorine pesticides and PCBs (Brown and Caldwell 1992). We used these site-boundary air-quality data as representative of the off-site air quality. They only detected chlordane and DDD. Both pesticides, however, were above their comparison values (Table 10, Appendix B).

C. Quality Assurance and Quality Control

We assume the environmental data used in our assessment are valid since governmental contractors or contractors overseen by governmental agencies collected and analyzed the environmental samples. In preparing this public health assessment, we relied on the existing environmental data. We assumed consultants who collected and analyzed these samples followed adequate quality assurance and quality control measures concerning chain-of-custody, laboratory procedures, and data reporting. The completeness and reliability of the referenced information determines the validity of the analyses and conclusions drawn for this public health assessment.

In each of the preceding On- and Off-Site Contamination subsections, we evaluated the adequacy of the data to estimate exposures. We assumed that estimated data (J) and presumptive data (N) were valid. This second assumption errs on the side of public health by assuming that a contaminant exists when it may not exist.

D. Physical and Other Hazards

The site is level, covered with grass, completely fenced, and contains neither buildings nor equipment. We did not observe physical or other types of hazards.

PATHWAYS ANALYSES

To decide whether nearby residents have contacted contaminants migrating from the site, we evaluated the environmental and human components of exposure pathways. Exposure pathways consist of five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure, and an exposed population.

We eliminate an exposure pathway if at least one of five elements is missing and will never be present. Exposure pathways that we do not eliminate are either completed or potential. For completed pathways, all five elements exist and exposure to a contaminant has occurred, is occurring, or will occur. At least one of five elements is missing, but could exist for potential pathways. For potential pathways, exposure to a contaminant could have occurred, could be occurring, or could occur in the future.

A. Completed Exposure Pathways

We categorized incidental soil ingestion and inhalation of contaminated dust as completed exposure pathways. Refer to Table 11, Appendix B for a summary of these completed exposure pathways.

Off-Site Incidental Soil Ingestion Pathway

Incidental ingestion of off-site contaminated soil is a completed exposure pathway. Residents of the Armstrong Trailer Park were exposed to site-related contaminants via incidental ingestion of contaminated soil. Stormwater was the likely transport mechanism of contaminated soil from the site to the trailer park. Contaminated soil in the Armstrong Trailer Park is the point of exposure. Incidental ingestion is the route of exposure. The approximately 150 residents of the Armstrong Trailer Park are the receptor population.

We estimate residents of the Armstrong were exposed to contaminated soil via incidental ingestion from 1952 to 1994. Aerial photographs first showed nearby trailers in 1952. Chevron removed the contaminated soil in 1994. We err on the side of protecting public health by assuming that any one person lived in this trailer park for 42 years (1952-1994).

Off-Site Inhalation Pathway

Inhalation of contaminated dust is a completed exposure pathway. Residents of the Armstrong and 441 Trailer Parks were exposed to site-related contaminants via inhalation of contaminated dust. Contaminated soil on the site is the source of the contaminants. Strong winds blew contaminated dust to the Armstrong and 441 Trailer Parks during dry periods. Contaminated air in these two trailers parks is the point of exposure. Inhalation is the route of exposure. The approximately 300 residents of the Armstrong and 441 Trailer Parks are the receptor population.

We estimate residents of the Armstrong and 441 Trailer Parks were exposed to contaminated dust from 1952 to 1976. Aerial photographs first showed nearby trailers in 1952. Chevron ceased operations in 1976. We estimate they were not exposed from 1976 to 1992. From 1976 to 1992 vegetation covered the unpaved portion of the site and significant wind blown dust was unlikely. These residents were again exposed during the 1992 site cleanup. Since 1992 grass has covered the site and wind-blown dust is unlikely.

B. Potential Exposure Pathways

We categorize off-site ground water and off-site surface water as potential exposure pathways. Refer to Table 12, Appendix B, for a summary of these potential exposure pathways.

Off-Site Ground-Water Pathway

Off-site ground water is a potential exposure pathway. Ground water under the Armstrong Trailer Park north of the site is contaminated. Currently, the City of Orlando supplies water to all of the residents of the Armstrong and 441 Trailer Parks (the area over the contaminated ground water) (Orange CPHU 1993). Although no one currently uses this ground water, if it was ingested, the trailer park residents would be exposed to site-related contaminants. Contaminated soil on the site is the source and ground-water flow is the transport mechanism. If this contaminated ground water is ever used, private wells would be the point of exposure. Ingestion would be the predominant route of exposure. Assuming they all began using the contaminated ground water, the approximately 300 residents of the Armstrong and 441 Trailer Parks would be the receptor population.

Off-Site Surface Water Pathway

Off-site surface water is a potential exposure pathway. Although contaminated ground water has not reached Lake Fairview, if it does, recreational users would be exposed to site-related contaminants via incidental ingestion and skin absorption during swimming, boating, etc. Contaminated soil on the site is the source and ground-water flow is the transport mechanism. The water of Lake Fairview would be the point of exposure. Incidental ingestion and skin absorption would be the routes of exposure. We estimate that 500 recreational users per year would be the receptor population.

C. Eliminated Pathways

We eliminated on-site surface water as an exposure pathway since the soil is too porous and the terrain too flat for any significant accumulation of water above ground surface. Since there is no surface water on site, we also eliminated contact with sediment as an exposure pathway. Transport of contaminated soil via stormwater run-off is considered above under the Completed Exposure Pathways section. Since there is no significant hunting or gardening in this area, we eliminated consumption of plants and animals as an exposure pathway.

We also eliminated incidental ingestion of, and skin absorption from, on-site soil as an exposure pathway. Chevron and Central Florida Mack Truck occupied the site from 1950 to 1986 and thus limited public access to the contaminated soil. Although Mr Uttal leased the warehouse for public storage between 1987 and 1990, vegetation covered the rest of the site and contact with the contaminated soil was unlikely. A fence has limited public access since April 1990. As long as the site remains undisturbed, exposure to the contaminated soil and ground water is unlikely.

PUBLIC HEALTH IMPLICATIONS

In this section we will discuss possible health effects for persons exposed to specific contaminants, evaluate state and local health databases, and address specific community health concerns.

A. Toxicological Evaluation

Introduction

In this subsection, we discuss exposure levels and possible health effects that might occur in people exposed to the contaminants of concern at the site. Also in this subsection, we discuss general concepts such as the risk of illness, dose response and thresholds, and uncertainty in public health assessments.

To evaluate exposure, we estimated the daily dose of each contaminant of concern found at the site. Kamrin (1988) explains a dose in this manner:

    "...all chemicals, no matter what their characteristics, are toxic in large enough quantities. Thus the amount of a chemical a person is exposed to is crucial in deciding the extent of toxicity that will occur. In attempting to place an exact number on the amount of a particular compound that is harmful, scientists recognize they must consider the size of an organism. It is unlikely, for example, that the same amount of a particular chemical that will cause toxic effects in a 1-pound rat will also cause toxicity in a 1-ton elephant.

    Thus instead of using the amount that is administered or to which an organism is exposed, it is more realistic to use the amount per weight of the organism. Thus 1 ounce administered to a 1-pound rat is equivalent to 2000 ounces to a 2000-pound (1-ton) elephant. In each case, the amount per weight is the same: 1 ounce for each pound of animal.

    This amount per weight is the dose. We use it to decide the amount of a drug to prescribe to patients of differing weights. We use dose in toxicology to compare the toxicity of different chemicals in different animals."

In expressing the daily dose, we used the units of milligrams of contaminant per kilogram of body weight per day (mg/kg/day).

To calculate the daily dose of each contaminant, we used standard assumptions about body weight, ingestion and inhalation rates, exposure time length, and other factors needed for dose calculation (ATSDR 1992d, 1993c; EPA 1990). In calculating the dose, we assumed residents were exposed to the maximum concentration measured for each contaminant in each medium.

To evaluate health effects, the ATSDR has developed Minimal Risk Levels (MRLs) for contaminants commonly found at hazardous waste sites. An MRL is an estimate of daily human exposure to a contaminant below which non-cancer, adverse health effects are unlikely to occur. The ATSDR developed MRLs for each route of exposure, such as ingestion and inhalation. The ATSDR also developed MRLs for the length of exposure, such as acute (less than 14 days), intermediate (15 to 364 days), and chromic (greater than 365 days). The ATSDR presents these MRLs in Toxicological Profiles. These chemical-specific profiles provide information on health effects, environmental transport, human exposure, and regulatory status.

In this section, we used standard assumptions to estimate human exposure from incidental ingestion of soil, from inhalation of contaminated dust, and from drinking ground water.

To estimate exposure from incidental ingestion of contaminated soil, we made the following assumptions: 1) children between the ages of one and six ingest an average of 200 milligrams (mg) of soil per day, 2) these children weigh about 10 kilograms (kg), 3) these children were exposed for six years (period when children are most likely to ingest soil), and 4) they ingested soil at the maximum concentration measured for each contaminant.

To estimate exposure from inhalation of pesticide-contaminated dust, we made the following assumptions: 1) nearby adults inhale about 1 cubic meter (m3) of air per hour, or 24 m3 of air per day, 2) these adults weigh 70 kilograms (kg), 3) these adults have been exposed for 25 years, and 4) these adults were exposed to the maximum air concentrations measured for each contaminant. Since Chevron monitored the air at the boundary between the site and the trailer park, we assumed nearby residents inhaled the maximum measured concentration. We did not include any factor for dilution.

To estimate the potential exposure from drinking contaminated ground water, we assumed: 1) adults ingest an average of 2 liters of water per day, 2) these adults weigh about 70 kilograms, 3) in the future, these adults may be exposed for five years, and 4) for each contaminant measured in the ground water, they will ingest the maximum measured concentration. We selected a five-year exposure period based on the average time between household moves in the U.S. We also base this exposure period on our estimate of the average time between private well testing in a mixed residential/commercial/industrial area.

We did not estimate potential exposure from incidental ingestion and skin absorption of contaminants during swimming, boating, etc. in Lake Fairview. Ground-water monitoring data show that contamination has not reached Lake Fairview. Dilution, physical retardation, and biodegradation in the ground water make it impractical to predict future concentrations in this nearby lake. Without an estimate of contaminant concentration in the lake, we cannot estimate exposure or likely health effects.

Chlordane

Some adults and children living in the Armstrong Trailer Park north of the site were exposed to chlordane via breathing contaminated dust and incidental ingestion of contaminated soil. They could also be exposed to chlordane via drinking if they ever use the contaminated ground water below the trailer park.

Since there is no air monitoring data before 1992, we do not know the public health threat from breathing chlordane-contaminated dust before then. The maximum concentration of chlordane in the air during the 1992 site cleanup, however, was below the ATSDR intermediate Minimal Risk Level (ATSDR 1989a, 1992b). Therefore, we do not expect any health effects from exposure to chlordane-contaminated dust during the 1992 site cleanup. Since clean soil and grass now cover the site, we do not expect any future exposure to chlordane-contaminated dust.

Our estimate of a child's chlordane exposure via incidental ingestion of Armstrong Trailer Park contaminated soil before 1994 is slightly above the ATSDR intermediate and chronic Minimal Risk Levels (ATSDR 1989a, 1992b). ATSDR MRLs are screening levels. Exposures below an MRL are unlikely to cause illness. Exposures above an MRL may or may not cause an illness, depending on how much above the MRL and for how long. Although our estimate of a child's exposure to chlordane from Chevron is slightly above the ATSDR MRL, we do not expect any health effects. Our estimate of a child's exposure is 40 times less than the lowest exposure (dose) that did not cause liver damage in rats or mice (Vesicol 1983a, 1983b; Khasawinah and Grutsch 1989a, 1989b).

Our estimate of an adult's chlordane exposure via incidental ingestion of Armstrong Trailer Park contaminated soil before 1994 is below the ATSDR acute, intermediate, and chronic Minimal Risk Levels (ATSDR 1989a, 1992b). Therefore, we do not expect any non-cancer health effects from this exposure. Although there is no evidence of chlordane causing cancer in humans, the EPA has classified it as a probable human carcinogen based on limited animal testing. Chlordane has caused liver cancer in both rats and mice (Vesicol 1983a, 1983b; Khasawinah and Grutsch 1989a, 1989b). We estimate that some adults in the Armstrong Trailer Park are at a moderately increased risk of liver cancer from incidental ingestion of chlordane-contaminated soil before 1994. Following the 1994 soil removal from the Armstrong Trailer Park, we estimate the increased cancer risk from incidental ingestion of chlordane-contaminated soil in the future is insignificant.

Currently, we do not know of anyone drinking contaminated ground water at or near this site. Our estimate of a child's chlordane exposure via ingestion of contaminated ground water below the Armstrong Trailer Park is slightly above the ATSDR intermediate and chronic MRL. This estimate, however, is 20 times less than the lowest exposure (dose) that did not cause liver damage in rats or mice (ATSDR 1989a, 1992b). Our estimate of an adult's chlordane exposure via ingestion of contaminated ground water under the Armstrong Trailer Park is less than the ATSDR acute, intermediate, and chronic MRL. Therefore, we do not expect any non-cancer health effects in children or adults if they drank this contaminated ground water.

Although there is no evidence of chlordane causing cancer in humans, the EPA has classified it as a probable human carcinogen based on limited animal testing. Chlordane has caused liver cancer in both rats and mice (Vesicol 1983a, 1983b; Khasawinah and Grutsch 1989a, 1989b). We estimate that some adults in the Armstrong Trailer Park would be at a low increased risk of liver cancer if they drank the chlordane-contaminated ground water over a lifetime. We recommend the Southwest Florida Water Management District prohibit any new private wells in this area. Or, we recommend they prohibit domestic use of the contaminated ground water until it meets all state and federal drinking water standards.

DDD

Some adults and children living in the Armstrong Trailer Park north of the site were exposed to DDD via breathing contaminated dust and incidental ingestion of contaminated soil. They could also be exposed to DDD via drinking if they ever use the contaminated ground water below the trailer park.

Since there is no air-monitoring data before 1992, we do not know the public health threat from breathing DDD-contaminated dust before then. Although there is no ATSDR Minimal Risk Level for DDD, the maximum concentration of DDD in the air during the 1992 site cleanup was 250 times less than the EPA air unit risk for the closely related pesticide DDT (ATSDR 1989b, 1992c). Therefore, we do not expect any health effects from exposure to DDD-contaminated dust during the 1992 site cleanup. Since clean soil and grass now cover the site, we do not expect any future exposure to DDD-contaminated dust.

Our estimate of a child's DDD exposure via incidental ingestion of Armstrong Trailer Park soil before 1994 is slightly above the ATSDR intermediate Minimal Risk Levels (ATSDR 1989b, 1992c). This estimate, however, is 10,000 times less than the lowest exposure (dose) that did not cause heart, blood, or liver damage in humans (Hayes et al. 1956). Therefore, we do not expect any health effects in children from ingesting DDD-contaminated soil at the Armstrong Trailer Park.

Our estimate of an adult's DDD exposure via incidental ingestion of Armstrong Trailer Park soil before 1994 is below the ATSDR acute and intermediate Minimal Risk Levels (ATSDR 1989b, 1992c). Although there is no evidence of DDD causing cancer in humans, The EPA has classified it as a probable human carcinogen based on limited animal testing. Our estimate of an adult's DDD exposure via incidental ingestion of Armstrong Trailer Park soil, however, is below the EPA upper-bound 10-6 excess cancer-risk estimate. Therefore, we do not expect any health effects in adults from this exposure.

Currently, we do not know of anyone drinking contaminated ground water at or near this site. Our estimate of a child's DDD exposure via ingestion of contaminated ground water below the Armstrong Trailer Park is above the ATSDR acute and intermediate MRL (ATSDR 1989b, 1992c). This estimate, however, is 750 times less than the lowest exposure (dose) that did not cause heart, blood, or liver damage in humans (Hayes et al. 1956). Our estimate of an adult's DDD exposure via ingestion of contaminated ground water below the Armstrong Trailer Park is slightly below the ATSDR acute MRL but above the intermediate MRL. Our estimate, however, is three thousand (3,000) times less than the lowest exposure (dose) that did not cause heart, blood, or liver damage in humans (Hayes et al. 1956). Although there is no evidence of DDD causing cancer in humans, the EPA has classified it as a probable human carcinogen based on limited animal testing. Our estimate of an adult's DDD exposure via incidental ingestion of contaminated ground water below the Armstrong Trailer Park, however, is less than the EPA upper-bound 10-6 excess cancer-risk estimate. Therefore, we do not expect any health effects in children or adults if they drank DDD-contaminated ground water below the Armstrong Trailer Park.

Although we do not expect any health effects from drinking DDD in the ground water, we do not recommend anyone drink this water. We recommend the Southwest Florida Water Management District prohibit any private wells in this area. Or we recommend they prohibit domestic use of the contaminated ground water until it meets all state and federal drinking-water standards.

DDT

Some adults and children living in the Armstrong Trailer Park north of the site were exposed to DDT via incidental ingestion of contaminated soil. Neither Chevron nor EPA has detected DDT in the air or ground water off site.

Our estimate of a child's DDT exposure via incidental ingestion of Armstrong Trailer Park soil before 1994 is less than the ATSDR acute Minimal Risk Level but slightly above the intermediate MRL (ATSDR 1989b, 1992c). This estimate, however, is eight thousand five hundred (8,500) times less than the lowest exposure (dose) that did not cause heart, blood, or liver damage in humans (Hayes et al. 1956). Therefore, we do not expect any health effects in children from ingesting DDT-contaminated soil at the Armstrong Trailer Park.

Our estimate of an adult's DDT exposure via incidental ingestion of Armstrong Trailer Park soil before 1994 is below both the ATSDR acute and intermediate Minimal Risk Levels (ATSDR 1989b, 1992c). Although there is no evidence of DDT causing cancer in humans, the EPA has classified it as a probable human carcinogen based on limited animal testing. This estimate of an adult's DDT exposure via incidental ingestion of Armstrong Trailer Park soil, however, is below the EPA upper-bound 10-6 excess cancer-risk estimate. Therefore, we do not expect any health effects in adults from this exposure.

Dieldrin

Some adults and children living in the Armstrong Trailer Park north of the site were exposed to dieldrin via incidental ingestion of contaminated soil. Neither Chevron nor EPA has detected dieldrin in the air or ground water off site.

Our estimate of both a child and adult's dieldrin exposure via incidental ingestion of Armstrong Trailer Park soil before 1994 is less than both the ATSDR acute and chronic Minimal Risk Level (ATSDR 1993a). Although there is no evidence of dieldrin causing cancer in humans, the EPA has classified it as a probable human carcinogen based on limited animal testing. This estimate of an adult's dieldrin exposure via incidental ingestion of Armstrong Trailer Park soil, however, is below the EPA upper-bound 10-6 excess cancer-risk estimate. Therefore, we do not expect any health effects (including cancer) in children or adults from ingesting dieldrin-contaminated soil at the Armstrong Trailer Park.

Heptachlor Epoxide

Some adults and children living in the Armstrong Trailer Park north of the site were exposed to heptachlor epoxide via incidental ingestion of contaminated soil. Neither Chevron nor EPA has detected heptachlor epoxide in the air or ground water off site.

Our estimate of both a child and adult's heptachlor exposure epoxide via incidental ingestion of Armstrong Trailer Park soil before 1994 is less than the ATSDR chronic Minimal Risk Level (ATSDR 1989c, 1993b). Although there is no evidence of heptachlor epoxide causing cancer in humans, the EPA has classified it as a probable human carcinogen based on limited animal testing. This estimate of an adult's heptachlor epoxide exposure via incidental ingestion of Armstrong Trailer Park soil, however, is below the EPA upper-bound 10-6 excess cancer-risk estimate. Therefore, we do not expect any health effects in children or adults from ingesting heptachlor epoxide-contaminated soil at the Armstrong Trailer Park.

Risk of Illness

In this health assessment, the risk of illness is the chance that exposure to a hazardous contaminant is associated with a harmful health effect or illness. The risk of illness is not a measure of cause and effect; only an in-depth health study can identify a cause and effect relationship. Instead, we use the risk of illness to determine if the nearby community needs a follow-up health study and to identify possible associations.

The greater the exposure to a hazardous contaminant (dose), the greater the risk of illness. The amount of a substance required to harm a person's health (toxicity) also determines the risk of illness. Exposure to a hazardous contaminant above a minimum level increases everyone's risk of illness. Only in unusual circumstances, however, do many people become ill. We usually measure and report individual risks of illness as an expression of chance. Consequently, scientists discuss the likelihood of becoming ill, and may express the chance of becoming ill as a fraction. For example, some workers exposed to very high levels of asbestos had an estimated cancer risk of one chance in one hundred (1 in 100). However, the estimated cancer risk from exposure to the lower asbestos levels in outside air was one chance in ten thousand (1 in 10,000). Sometimes, scientists compare the severity of different risks by looking at the expected occurrences of an illness for the total exposed population. For example, in 100,000 workers exposed to high levels of asbestos in the 1930s and 1940s, scientists would expect to see 1,000 (= 100,000 x 1/100) extra cancer cases. If 100,000 people were exposed only to low levels of asbestos, scientists would expect to see 10 (= 100,000 x 1/10,000) extra cases of cancer (EPA 1990).

Information from human studies provides the Best evidence that exposure to a hazardous contaminant is related to a particular illness. Some of this evidence comes from doctors reporting unusual incidence of a specific illness in exposed individuals. More formal studies compare illnesses in people with different levels of exposure. However, human information is very limited for most hazardous contaminants, and scientists frequently must depend upon data from animal studies. We use animal studies to estimate risk of illness in humans. Hazardous contaminants associated with harmful health effects in humans are often associated with harmful health effects in other animal species. There are limits, however, in only relying on animal studies. For example, scientists have found some hazardous contaminants are associated with cancer in mammals, but lack evidence of a similar association in humans. In addition, humans and animals have differing abilities to protect themselves against low levels of contaminants, and most animal studies test only the possible health effects of high exposure levels. Consequently, the possible effects on humans of low-level exposure to a hazardous contaminant are uncertain when information is derived solely from animal experiments (EPA 1990).

Dose-Response and Threshold Ideas

The focus of toxicological studies in humans or animals is identification of the relationship between exposure to different doses of a specific contaminant and the chance of having a health effect from each exposure level. This dose-response relationship provides a mathematical formula or graph that we use to estimate a person's risk of illness. The actual shape of the dose-response curve requires scientific knowledge of how a hazardous substance affects different cells in the human body. There is one important difference between the dose-response curves used to estimate the risk of noncancer illnesses and those used to estimate the risk of cancer: the existence of a threshold dose. A threshold dose is the highest exposure dose at which there is no risk of illness. The dose-response curves for noncancer illnesses include a threshold dose that is greater than zero. Scientists include a threshold dose in these models because the human body can adjust to varying amounts of cell damage without illness. The threshold dose differs for different contaminants and different exposure routes, and we estimate it from information gathered in human and animal studies. In contrast, the dose-response curves used to estimate the risk of cancer assume there is no threshold dose (or, the cancer threshold dose is zero). This assumes a single contaminant molecule may be sufficient to cause a clinical case of cancer (EPA 1990). This assumption is very conservative, and many scientists believe a threshold dose greater than zero also exists for the development of cancer.

Uncertainty in Risk Assessments

All risk assessments require the use of assumptions, judgements, and incomplete data to varying degrees. These contribute to the uncertainty of the final risk estimates. Some more important sources of uncertainty in this public health assessment include environmental sampling and analysis, exposure parameter estimates, use of modeled data, and present toxicological knowledge. These uncertainties may cause risk to be overestimated or underestimated to a different extent (ICF Kaiser 1993). Because of the uncertainties described below, this public health assessment does not represent an absolute estimate of risk to persons exposed to chemicals at or near the Chevron site.

Environmental chemistry analysis errors can arise from random errors in the sampling and analytical processes, resulting in either an over- or under-estimation of risk. We can control these errors to some extent by increasing the number of samples collected and analyzed and by sampling the same locations over several different periods. The above actions tend to minimize uncertainty contributed from random sampling errors (ICF Kaiser 1993).

There are two areas of uncertainty related to exposure parameter estimates. The first is the exposure-point concentration estimate. The second is the estimate of the total chemical exposures (ICF Kaiser 1993). In this assessment we used maximum detected concentrations as the exposure point concentration. We believe using the maximum measured value to be appropriate because we cannot be certain of the peak contaminant concentrations, and we cannot statistically predict peak values. Nevertheless, this assumption introduces uncertainty into the risk assessment that may over- or under-estimate the actual risk of illness. When selecting parameter values to estimate exposure dose, we used default assumptions and values within the ranges recommended by the ATSDR or the EPA. These default assumptions and values are conservative (health protective) and may contribute to the over-estimation of risk of illness. Similarly, we assumed the maximum exposure period occurred regularly for each selected pathway. Both assumptions are likely to contribute to the over-estimation of risk of illness.

There are also data gaps and uncertainties in the design, extrapolation, and interpretation of toxicological experimental studies (ICF Kaiser 1993). Data gaps contribute uncertainty because information is either not available or is addressed qualitatively. Moreover, the available information on the interaction among chemicals found at the site, when present, is qualitative (that is, a description instead of a number) and we cannot apply a mathematical formula to estimate the dose. These data gaps may tend to underestimate the actual risk of illness. In addition, there are great uncertainties in extrapolating from high-to-low doses, and from animal-to-human populations. Extrapolating from animals to humans is uncertain because of the differences in the uptake, metabolism, distribution, and body organ susceptibility between different species. Human populations are also variable because of differences in genetic constitution, diet, home and occupational environment, activity patterns, and other factors. These uncertainties can result in an over- or under-estimation of risk of illness. Finally, there are great uncertainties in extrapolating from high to low doses, and controversy in interpreting these results. Because the models used to estimate dose-response relationships in experimental studies are conservative, they tend to over estimate the risk. Techniques used to derive acceptable exposure levels account for such variables through the use of safety factors. Currently, there is much debate in the scientific community about how much we over estimate the actual risks and what the risk estimates really mean.

B. Health Outcome Data Evaluation

We did not evaluate health outcome data for the community around this site. It is unlikely a search of statewide health-outcome data would detect an effect in such a small group. Therefore, there is little justification or community demand for an evaluation of health outcome data at this time. If future environmental investigations find other contaminants, we will evaluate health outcome data as considered appropriate.

C. Community Health Concerns Evaluation

In this subsection, we address the community health concerns in terms of our findings presented in the Toxicological Evaluation subsection above.

Although we interpret the health concerns in terms of our toxicological findings, it is important to remember that many individual symptoms, conditions, and illnesses reported by the community have more than one cause. Similarly, any one reported symptom may suggest many different illnesses. To distinguish between illnesses caused by substances found at the site and those caused by other agents requires an in-depth health study. Therefore, our findings in this subsection suggest health problems that are possible, instead of health problems that are likely.

Conversely, it is also important to remember that our not finding an association between a contaminant and an illness in the toxicological literature does not necessarily mean the association does not exist. There are two possible explanations for this insufficiency in the literature. On one hand, there truly may be no association between a contaminant and a specific illness, or between a contaminant at the estimated concentration and a specific illness. Consequently, we will not find certain health effects regardless of the number of studies we conduct. On the other hand, there may not be enough reliable studies to identify an existing association between a contaminant and an illness. Therefore, the associations could be found if there were more studies. Without more research, we cannot tell which alternative correctly describes the literature insufficiency.

We address community health concerns as follows:

1. A few residents of the Armstrong Trailer Park north of the site were concerned that breathing pesticide-contaminated dust during the 1992 soil removal would affect their health. Specifically, they complained of strong odors, skin rashes, burning eyes and noses, nausea, sore throats, and chest pains during that time.

    During the 1992 soil removal, Chevron measured both chlordane and DDD in the airborne dust along the boundary between the site and the Armstrong Trailer Park. The maximum concentration of chlordane in the air during the 1992 site cleanup, however, was below the ATSDR intermediate Minimal Risk Level (ATSDR 1989a, 1992b). Although there is no ATSDR Minimal Risk Level for DDD, the maximum concentration of DDD in the air during the 1992 site cleanup was 250 times less than the EPA air unit risk for the closely related pesticide DDT (ATSDR 1989b, 1992c). Therefore, we do not expect any health effects from exposure to either chlordane or DDD-contaminated dust during the 1992 site cleanup. Since clean soil and grass now cover the site, we do not expect any future exposure to contaminated dust. Since there is no air monitoring data before 1992, we do not know the public health threat from breathing contaminated dust before that time.

2. A few nearby residents are concerned that contaminated ground water will reach their private wells and affect their health.

    It is unlikely that contaminants from this site will reach private wells in the near future. Monitoring well data shows that contaminated ground water is limited to the area under the Armstrong Trailer Park north of the site. There are no known drinking water wells in this area north of the site. The City of Orlando supplies area residents and businesses with water from distant wells. Nearby residents or businesses who use private wells and are concerned about water quality can request the Orange County Public Health Unit test their water for pesticides.

3. A few nearby residents are concerned that contaminated ground water will reach Lake Fairview and affect their health via consumption of fish, incidental ingestion of water, or skin absorption.

    It is unlikely that contaminants from this site will reach Lake Fairview in the near future. Monitoring well data shows that contaminated ground water is limited to the area under the Armstrong Trailer Park north of the site. These data show that contaminated ground water has not reached Lake Fairview. The EPA is reviewing cleanup options to contain the spread of contaminated ground water.

4. One nearby resident was concerned his health had been affected by living near this site. He did not specify what illnesses he thought were site related. He was also concerned that the stress of living near a hazardous waste site had affected his health.

    We estimate that some adults in the Armstrong Trailer Park are at a moderate increased cancer risk from incidental ingestion of chlordane-contaminated soil before 1994. We are unable to relate any other illnesses to chemicals from this site at the estimated exposure levels.

    Stress can affect people's health and cause many illnesses. Living next to a hazardous waste site can add to normal stress in people's lives. Although inconclusive, the psychological literature suggests the possibility of exposure to hazardous substances can cause heightened uncertainty regarding health, demoralization, possibly increased psychological disorders, and social conflict. Until the literature is more definitive, however, we cannot evaluate the health effects from the stress of living next to a hazardous waste site. Also, we currently cannot separate the health effects caused by the stress of living next to a hazardous waste site from health effects caused by other stresses.

5. One nearby resident was concerned his emphysema was aggravated by breathing contaminated dust from the site.

    Dust, whether contaminated with pesticides or not, can aggravate emphysema and other respiratory conditions. Since there is no air monitoring data before 1992, we do not know the public health threat from breathing contaminated dust before that time. The levels of dust in the air during the 1992 site cleanup may have aggravated this resident's emphysema. None of the pesticides detected in the air, however, have been found to cause or aggravate emphysema or other respiratory problems. Since clean soil and grass now cover the site, we do not expect any future exposure to contaminated dust.

6. Some nearby residents were concerned that home-grown fruits and vegetables were no longer safe to eat.

    Although there has been no testing of any of these fruits or vegetables, there is no indication from the existing soil and ground water monitoring data that they would be unsafe to eat.

7. One residents is concerned that her children continue to suffer from skin rashes, runny noses, fever, bronchitis, and other flu-like symptoms.

    Since Chevron removed contaminated soil from the site in 1992 and from the Armstrong Trailer Park in 1994, it is unlikely these illness are due to chemicals from this site.


Next Section       Table of Contents

  
 
USA.gov: The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

A-Z Index

  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #