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Exposure Pathways and Human Health Assessment

ATSDR evaluates environmental information to determine if the environmental media (i.e. soil, air, water, biota) contains contamination at levels of health concern. If people could come into contact with the contaminated media (touch it, breathe it, or ingest it), ATSDR evaluates if health effects would be likely from such an exposure. ATSDR's methodology is presented in Appendix C.

Indeterminate Public Health Hazard

Air Exposure Pathway


ATSDR will evaluate past air emissions and report the results in Phase II of the public health assessment. ATSDR determined that available data on past usage or emissions for many contaminants was insufficient or not suitable for analysis. There is evidence that past air emissions may have been greater that current air emissions. The base has agreed to perform a study to estimate past air emissions.

The indeterminate category in used when critical data are insufficient with regard to extent of exposure and/or toxicologic properties at estimated exposure levels.

Non-occupational On-base Employees

ATSDR identified on-base locations where potential exposures may have resulted in an estimated increase in cancer risk. These locations are in the immediate vicinity of the sources and need further evaluation. The air model results estimate higher exposure concentrations for non-occupational on-base employees, due to environmental (not occupational) exposures to these employees. These are employees who may be environmentally exposed to emissions outside of the immediate occupational environment generating the emissions. The present air dispersion model does not discern if any on-base workers might be exposed at levels of concern. ATSDR will perform a refined model to better evaluate the exposure conditions by investigating the behavior of air emissions in the immediate vicinity of the sources in Phase II. ATSDR does not consider it likely that current on-base exposures would result in health effects.

Lead Exposure from Soil Transport from S-1 Area (Building 1592)

ATSDR evaluated the possible exposure to soils potentially transported from the S-1 area. Residents believe that lead-contaminated soil may have been transported into the community and children playing there may have been exposed. Subsequently, they believe that lead may be the cause of below-average test scores by children in neighborhood schools (7). Residents in the North Kelly Gardens community recalled that portions of the community flooded during rainstorms. Residents wanted to know if any adverse health effects could be expected if lead in the soil in the S-1 area migrated into the community. Soil sampling was conducted on the base and along Growdon Road by Kelly AFB contractors. Private citizens of North Kelly Gardens collected soil samples off base in the community. Problems exist with both sampling events, making it difficult to determine if soil migrated from the on-base area of S-1 to the off-base area of North Kelly Gardens, resulting in elevated lead levels in the soil in the community. ATSDR recommends health education about lead exposure, about blood lead testing programs, and about environmental investigation of homes from which elevated blood leads are confirmed.

From the early 1960s to 1973, the S-1 area (shown in Figure 6, page 31) served as a temporary storage location for waste to be reclaimed off base. There was a spoil area for scrap metal, temporary storage of transformers, and storage of spent solvents and waste oil. During the time the S-1 area was used for waste storage, spills occurred. These spilled materials collected in a natural depression and contaminated the soil. After 1973, the area was abandoned, the storage tanks removed, and the area was backfilled and regraded. Residents in the North Kelly Gardens community recall that the area flooded during rainstorms, and water backed up into portions of the community. In response to community concerns, Kelly AFB conducted an investigation of surface soil in the S-1 area, adjacent on-base areas, and outside the fence along Growdon Road between the fence and the community of North Kelly Gardens.

The analysis and evaluation of surface soils at the S-1 site by Kelly AFB detected metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Analyses were also performed on samples taken from other near-by areas of Kelly AFB and in the right-of-way along Growdon Road. Except for isolated samples, contaminants detected outside of the S-1 area were near background levels and not at levels of health concern. Samples were not collected on properties in the community (8,9). Moreover, as a consequence of road work and construction of the storm drainage system, soil in the area have been graded and back-filled, making it impossible to trace any migration that may have occurred.

Representatives of the North Kelly Gardens community conducted their own soil sampling of private property. However, quality control and quality assurance information and the specific soil concentrations were not linked to the specific sample locations in the report. Nevertheless, ATSDR considered the reported results in evaluating the potential for health concerns. The concentrations reported in the Community Health Survey of neighborhood yards are below levels of health concern. The reported values for lead, 44.6 milligrams per kilogram (mg/kg) average and 64.5 mg/kg maximum, are considerably below the EPA soil screening value for residential soil of 400 mg/kg (7,10). The reported values for arsenic (14.2 mg/kg average, 22 mg/kg maximum) are less than the ATSDR soil screening values for chronic exposures of 20 mg/kg for a child and 200 mg/kg for an adult (7,11). If these reported values are representative of the levels in neighborhood soil, no adverse health effects would be expected.

Nationally elevated blood lead levels are generally caused by lead paint and by lead in drinking water containing lead from lead pipes and solder. Many of the houses in this area were built when such products were used, and these conditions may not have been remediated. Although Kelly AFB began operations in 1917, the area around Kelly AFB was cultivated agricultural land until community development began in the 1950s and 1960s. Therefore, it is possible that before and during the time of community development, lead and arsenic may have been used in agricultural pesticides in the area. Values reported by the Community Health Survey, which were somewhat higher than background values reported on Kelly AFB but below levels of health concern, may reflect levels of these chemicals that resulted from their use as agricultural pesticides. The land area chosen for background samples on Kelly AFB was selected because it was not impacted by base activities. Supporting evidence suggest that water quality parameters from upper Leon Creek indicate levels of arsenic that could not have been contributed by Kelly AFB, because that portion of Leon Creek does not receive drainage from Kelly AFB. The widespread detection of arsenic in Leon Creek and other streams may indicate the use of pesticides on cultivated agricultural land.

Conclusions (Indeterminate Issues)

Exposure levels to past air emissions and non-occupational on-base employees are indeterminate.

Exposure to potentially contaminated soil that may have migrated from Kelly AFB to the North Kelly Garden neighborhood is an unlikely cause of the low test scores in neighborhood schools. Limitations with environmental data make it difficult to address the migration of soil from Kelly AFB to the North Kelly Gardens community. Therefore, ATSDR concludes that exposure levels to soil contaminants are indeterminate.

Recommendations (Indeterminate Issues)

Perform a refined air dispersion model to provide data for evaluation of the past air emissions and non-occupational on-base employees pathways.

In response to high community concern and to promote prudent public health intervention, ATSDR recommends health education and promotion activities to inform community members about lead hazards and existing programs in which they can have their children's blood lead levels tested if they believe their children exhibit symptoms of lead poisoning. Homes containing children with confirmed elevated blood lead levels can be assessed through existing programs to determine the possible source of the elevated levels (such as soil, water, lead water pipes, or lead-based paint).

Figure 6
Site S-1

Building 1592 Area. July 1997.
Reproduced from Human Health Risk Assessment of Surface Soil.

No Apparent Public Health Hazard

Present Air Exposure Pathway

In response to citizen's concerns regarding possible air emissions from Kelly AFB, ATSDR looked at the contaminants that could be released into the air from the base and determined whether people could come into contact with them at concentrations that would present a threat to public health. ATSDR used an air dispersion model based on the base's current air emissions information to predict contaminant concentrations that could be present in the air. On the basis of the air model results, ATSDR has estimated that current air emissions (after 1995) from Kelly AFB would not be expected to result in health effects from either short-term (acute) exposures or long-term (chronic) exposures.

The no apparent public health hazard category indicates that people may have come into contact with contaminants, but the concentration of the contaminant was too low or the exposure too short for health effects to be expected.

Citizens in the North Kelly Gardens neighborhood reported to ATSDR that they frequently smelled odors which they believed to originate from Kelly AFB. They identified these odors primarily as a fuel odor and described another odor as a "sweet smelling" odor. Residents reported that they sometimes experienced health effects such as nausea, headaches, and difficulty breathing. They questioned whether the odors that they smelled might be related to their symptoms. They could not generally identify consistent time frames in which these odors occurred. One specific activity was identified that resulted in noticeable odors, when diesel trucks were waiting to unload fuel at the fuel tank farm, located approximately 500 feet from the nearest residence in the North Kelly Gardens neighborhood.

Sources of Air Emissions

Kelly AFB is a large industrial complex with many sources of air emissions. Over 1400 separate sources of air emissions were identified.

Industrial and Flight Line Activities

The industrial activities at Kelly AFB have involved repair and maintenance of various jet aircraft and engines, and include the capability to completely overhaul aircraft. Kelly has received 16 TNRCC air permits for a wide range of emission activities, including waste treatment emissions, in addition to maintenance and repair activities (12). The complexity and magnitude of industrial activities at Kelly AFB makes separate sampling and analysis of individual components of the many processes virtually impossible. The variable scheduling of processes and variable rate of each industrial activity, in addition to the large number of sources, do not lend themselves to traditional sampling and analysis techniques. In addition, traditional sampling and analysis cannot separate contributions by other emitters such as vehicles and other industries. However, the nature of air emissions (rate and release height); the interaction of meteorological phenomena, such as temperature, humidity, wind direction and speed, and precipitation events (rain, snow, fog); individual chemical characteristics (density, deposition, and photo reactivity); and site-specific physical obstructions (buildings), do lend themselves to computer modeling. Therefore, ATSDR used computer-assisted modeling of air dispersion at Kelly AFB as a reasonable means of estimating the concentration of contaminants to which people may be exposed. Although air dispersion modeling only gives an estimate of air contaminant concentrations, it allows ATSDR to estimate Kelly AFB's contribution to air pollution separate from all other sources (such as automobile emissions). A description of the model that ATSDR used is presented in Appendix D.

ATSDR modeled over 200 chemicals from over 1400 sources with many sources emitting multiple chemicals, resulting in over 7000 modeling inputs. ATSDR considered not only industrial emissions identified from permits, but also emissions from "grandfathered" processes, wastewater treatment processes, and flight line emissions, including takeoff and landings. Between 1990 and 1996, Kelly AFB significantly reduced emissions of hazardous substances under the Environmental Protection Agency Industrial Toxic Project. For present emissions, ATSDR used the most recent (1996) available data.

Fuel Tank Farm

The tanks possess dual covers: an outside stationary cover and an inside floating cover. In 1994, Kelly AFB changed from JP-4 to JP-8 jet fuel (13). JP-8 jet fuel is less volatile than JP-4 and contains lower levels of the BTEX compounds (benzene, toluene, ethylbenzene, and xylene)(14). In November 1994, the Air Force conducted air sampling for two days to determine if fuel components could be detected at the fence line (13). In January 1996, the Texas Natural Resources and Conservation Commission (TNRCC) conducted air sampling during one day to determine the presence of volatile organic compounds (VOCs), including fuel components, downwind from Kelly AFB (15). Fuel components were not detected at levels of health concern during either of these sampling events. In October 1997, the Air Force again conducted activities to determine the presence of fuel components in the air. Preliminary findings did not indicate the presence of fuel components above levels of health concern (16).

The odors that the residents of North Kelly Gardens community smell may in part be caused by the diesel trucks. On average, 10 trucks unload fuel at the tank farm every other day for a total weekly unloading average of approximately 85,000 gallons. While this schedule may vary, the average amount of jet fuel unloaded has remained relatively constant since the tanks were installed. The trucks often arrive early and wait with their motors idling until the facility opens and it is their turn to unload. The vapors generated by the long idling time may be substantial and could drift into the nearby community. Kelly AFB has devised a plan to relocate the trucks and has asked the trucking companies to not have their trucks idle while waiting to unload. The plan regarding relocation of the truck waiting area has been approved but has not been funded (17).

Evaluation of Present Air Emissions (after 1995)

ATSDR used concentrations estimated by the air dispersion model to evaluate potential short- and long-term exposures. The results of the screening comparison for short- and long-term noncancer effects is summarized in Table 2. Table 3 shows the results of the screening comparison for estimated cancer risks.

Health effects would not be expected from short-term exposures (acute) to estimated maximum one-hour concentrations of contaminants. The maximum one-hour average concentrations predicted by the model do not exceed ATSDR acute duration health guidelines. The estimates generated by the model do not include concentrations which may occur for periods of time less than an hour. ATSDR does not know if concentrations could be high enough for very short periods of time (less than an hour) to result in short-term health effects (such as nasal irritation). These exposures would be rare because the average hourly levels are low compared to health comparison values. Details are presented in Appendix D.

Present air concentrations estimated by air dispersion modeling of the 1996 air emissions inventory from Kelly AFB do not exceed comparison values for noncancer chronic (long-term exposures) exposures (Table 2). Chromium, 1,3-butadiene, and arsenic exceeded cancer comparison values (ATSDR cancer risk evaluation guide or CREG), as presented in Table 3. These contaminants were further evaluated using realistic exposure conditions (see Appendix D for details). For all present emissions of contaminants, it is unlikely that an increase in health effects could be observed in the population potentially exposed.

The community has expressed concern about their risk associated with the cumulative exposure to multiple chemicals. The cumulative increase in risk for developing any cancer for all present emissions of contaminants is presented in Figure 2 (page 8), which identifies the location of the highest estimated risks. These results indicate that the levels estimated by the air dispersion model would result in no apparent increased risk for developing cancer.

Screening evaluations do not indicate a need for further evaluation of potential current exposures to air emissions in the community. ATSDR concludes that health effects resulting from exposure to current emissions from Kelly AFB are unlikely. This is a conservative estimate because reasonable maximum exposure conditions were used as well as the highest estimated contaminant concentration. In addition, the use of a cumulative increase in cancer risk is likely to overestimate risk.

Long-term exposure to environmental levels of chemical mixtures represents an area of science that is poorly defined. Exposure to air emissions from Kelly AFB is difficult to separate from background levels common to ambient air in the home and an industrialized society. Modeling was used to estimate levels of many contaminants that could not be detected by conventional sampling. Based on modeling information and a consideration of all of the risks, health effects are not likely to be observed. Figure 2 (page 8) demonstrates that the cumulative risks associated with exposure are very low, both in the community and on base, except in the immediate vicinity of the source of emissions.


Current exposures to air emissions are occurring, but they are below levels of health concern; therefore, present air emissions have been classified as no apparent health hazard.



Table 2.

Present Air Quality Noncancer Screening Comparisons
Chemical Noncancer Screening Comparison a
1-Hour Max Concentration Short-term Comparison Value Exceeds Comparison Value Annual Average Concentration Long-term Comparison Value Exceeds Comparison Value
Hexavalent Chromium 0.5

0.5 a

No 0.001 0.1 b No
1,3-Butadiene - NA NA 0.014 NA NA
Arsenic - NA NA 0.0003 1.1c No
Formaldehyde 33. 60 b No 0.035 3.6 b No
Cadmium - NA NA 0.0006 0.2 c No
PCE 250. 1360 b No 0.2 271 b No
Benzene 6.9 160 b No 0.012 13 b No
2.8 1400 b No 0.005 106 b No

a All concentrations are in micrograms/cubic meter (1000 liters) of air. Concentrations are estimated from the Air Dispersion Model.
b ATSDR minimal risk level (MRL).
c EPA risk-based comparison tables
NA Not available or not applicable
All emissions data are from Kelly AFB 1996 Air Emissions Inventory.

Table 3.

Present Air Quality Cancer Screening Comparisons
Cancer Screening Comparison
Chemical Emissions (TPY) a Annual Average
Exceeds Comparison
Value d
Hexavalent Chromium 0.38 0.001 0.00008 Yes
1,3-Butadiene 0.7 0.014 0.004 Yes
Arsenic 0.017 0.0003 0.0002 Yes
Formaldehyde 6.06 0.035 0.08 No
Cadmium 0.003 0.0006 0.0006 No
PCE 9.7 0.2 2.0 No
Benzene 1.04 0.012 0.1 No
3.4 0.005 3.0 No

a TPY: Tons per year. All emissions data are from Kelly AFB 1996 Air Emissions Inventory.
b g/m: micrograms per cubic meter (1000 liters). Concentrations are estimated from the Air Dispersion Model.
c CREG: Cancer Risk Evaluation Guide.
d Further evaluated in Appendix D.

Leon Creek

In response to concerns voiced by community members, ATSDR evaluated the potential impact of environmental contamination to Leon Creek. Community members were concerned about swimming and eating fish caught in Leon Creek. ATSDR considered information provided by local residents, TNRCC, EPA, and Kelly AFB, and determined that adverse health effects would not be expected from recreational contact (swimming, wading, and eating fish) with off-base segments of Leon Creek.

Leon Creek is an urban stream that drains an area of 237 square miles. The drainage basin includes residential communities, farmlands, commercial/industrial facilities, recreational areas, and undeveloped properties. Kelly AFB occupies only 9 square miles of the drainage basin. Discharges into Leon Creek include groundwater infiltration, storm water runoff, and wastewater discharges from Kelly AFB, the city of San Antonio, and other commercial and industrial facilities. Flow in Leon Creek is extremely variable, with low flows during dry weather of less than 4 million gallons per day (MGD), to flows exceeding 300 MGD in wet weather. The flow variation results in a creek bed composed mostly of clay and gravel with pocket accumulation of organic material. Organic material retains persistent chemicals more than gravel and clay. The access to Leon Creek through Kelly AFB is restricted to the general public at the base boundaries (18,19) (page 7). This area is scheduled to be realigned as part of Lackland AFB.

ATSDR evaluated data and information obtained from local residents, TNRCC, EPA, and Kelly AFB, to assess the potential exposure through swimming, wading, and recreational fishing. Incidental ingestion of water and suspended sediment, dermal contact while swimming and wading, and consumption of fish were considered as pathways of potential concern. It is unlikely that Leon Creek would be a source of potable water or capable of supporting subsistence fishing. In the unlikely event that Leon Creek should be proposed as a source of drinking water, additional information would need to be determined (such as type of water treatment and location of intake), and potential health effects reexamined.

The selected exposure scenarios of incidental ingestion of surface water, incidental ingestion of suspended sediment, and consumption of fish caught by recreational anglers are described within each potential exposure pathway, as appropriate (Table 4). Each potential exposure pathway, the results of data evaluation, the selected exposure scenario, and the health implications associated with exposure are discussed in appropriate pathways. The assumptions used in calculating the risks associated with each exposure pathway are shown in Appendix E. Table 5 (surface water), Table 6 (sediment), and Table 7 (fish consumption) contain the maximum values detected for contaminants by Segment (for surface water and sediment) or Reach (for fish tissue concentration), comparison values used for each contaminant, and calculated risk values for each contaminant. (Segments and Reaches are short, well-defined areas of the creek). Tables 5-7 also show the type of chemical detected and the frequency of detection. Segments are described under Surface Water, and Reaches are described under Fish Consumption.

Common to all pathways, contaminants in each potential exposure pathway were screened using the Environmental Protection Agency (EPA) Region III Risk-Based Comparison (RBC) Tables. These tables identify the contaminant levels in the various media that are estimates of what EPA considers a safe level. These values were used because they are considered the most sensitive endpoint, cancer or noncancer. The maximum concentration detected for each contaminant was used as a screening estimate. The maximum exposure concentration was used as a worst case value.

Surface Water

Surface water and sediment from Leon Creek were sampled and analyzed by Kelly AFB during three separate events. Sampling was conducted according to physical lengths of the stream, termed Segments (Figure 7, page 42). Segment 1 represents the upstream portion of Leon Creek which does not receive drainage from Kelly AFB and ends at the northern base boundary. Segment 2 represents Leon Creek from the northern base boundary to the intersection of S.W. Military Drive. Segment 3 represents the portion of Leon Creek downstream of Military Drive to the southern base boundary. Segment 4 is the portion of Leon Creek downstream of the southern base boundary. Access to Kelly AFB is restricted, and the northern and southern boundaries are fenced, including a fence across Leon Creek to prohibit access. Therefore, access to the public is limited to Segment 1 (upstream of the northern base boundary) and Segment 4 (downstream of the southern base boundary). In addition, private access is available on the west bank of Leon Creek in Segment 3 via private land which is used for ranching. There is no general public or civilian private access to Segment 2; only base personnel are able to access Leon Creek along this length.

Five contaminants had values exceeding comparison values (See Table 5) (18). Two of these contaminants, benzo(b+k)fluoranthene and phenanthrene, are polycyclic aromatic hydrocarbons (PAH) which were only detected in Segment 3. Because these contaminants were not detected in any other Segment of the creek, there would be no exposure to the general public, as Segment 1 and Segment 4 are the only areas where the general public has access to Leon Creek. However, because private access is possible by the private landowners south of Leon Creek in Segment 3, these contaminants were included in the public health assessment.

The remaining three contaminants selected were volatile organic compounds (VOCs): trichloroethylene (TCE), tetrachloroethylene (PCE), and vinyl chloride (VC). The maximum concentration of each was detected in Segment 4, where public access is possible. These VOCs may have been discharged by the Environmental Process Control Facility (EPCF) at Kelly AFB or may have entered the stream from inflow of groundwater. The fate of these contaminants is likely to be short lived in Leon Creek as VOCs will volatilize from surface waters in proportion to temperature and turbulence. VOCs have a greater tendency to evaporate (volatilize) than water. Moreover, the rate at which evaporation occurs increases as the temperature rises or the rate of mixing (turbulence) increases.

ATSDR evaluated the exposure scenario of incidental ingestion of surface water while swimming or wading. ATSDR's screening process is presented in Appendix E, and the results are presented in Table 5. The comparison values used were based on drinking water and the most sensitive value chosen for comparison (whether cancer or noncancer). Potential exposure by incidental ingestion of surface water is unlikely to result in adverse health effects.

National Pollution Discharge Elimination System (NPDES) permits were reviewed for the last six years (20). TNRCC has classified Leon Creek for water quality parameters as a recreation and potential drinking water stream. Water quality parameters have been closely monitored by TNRCC and EPA, and discharges into Leon Creek are monitored routinely for chemical and physical parameters. The potential for future contamination exists due to leaching from buried landfills and waste pits located east of Leon Creek on the southwest portion of the base, as well as potential disruptions at the Environmental Pollution Control Facility (EPCF). The quality and quantity of monitoring and surveillance by TNRCC and EPA appear more than adequate to detect any significant changes in water quality in Leon Creek. This monitoring and surveillance should continue in order to ensure continued water quality and ecological health, especially during low flow conditions.


Exposure to contaminated sediment would be possible during such recreational activities as swimming, wading, and fishing. Sediment characteristics of Leon Creek are difficult to assess. Frequent scouring events occur naturally due to the type, frequency, and duration of flow variations. Flow variation results in organic material being deposited in pockets instead of uniformly dispersed along the stream bed. Most of the persistent chemicals tend to be adsorbed to sediment containing a greater fraction of organic material.

All contaminants that had any value exceeding their comparison value were selected for further evaluation and results presented in Table 6 (18). PAHs were detected in all Segments with benz(a)anthracene, benzo(b+k)fluoranthene, and benzo(a)pyrene having values exceeding comparison values. Dichlorodiphenyl-trichloroethane (DDT), a pesticide, had one value exceeding its comparison value in Segment 4. The polychlorinated biphenyl (PCB), Aroclor 1242, had only one detection exceeding a comparison value and that was in Segment 2, but was presented because PCBs were detected in fish tissue (See Table 7).

Incidental ingestion of suspended sediment while swimming or wading was considered as a potential exposure scenario. The limited contact that swimmers and waders would have with sediment does not indicate that the dermal route of exposure would be significant. The dermal dose of organic material (at 10% absorption) is equivalent to an oral ingestion default dose by an adult (100 mg), but the contact time is much less than a day in this scenario (21).

The assumptions for risk analysis are presented in Appendix E and screening results in Table 6. The cumulative assessment indicates that potential exposure by incidental ingestion of sediment is unlikely to result in health effects.

Fish Consumption

Tissue from species of local fish was collected by Kelly AFB and analyzed during separate sampling events according to the Reach in which the fish were caught. Reaches were selected according to the relative ease in which fish might move about, taking into account the limited natural barriers in the system, such as the dam on the golf course on Kelly AFB (Figure 8, page 45). Reach 1 is the portion of Leon Creek upstream from the low water dam on the golf course. Reach 2 represents the portion of Leon Creek between the dam and the Highway 16 overpass and includes the confluence with Indian Creek. Reach 3 encompasses Leon Creek from the Highway 16 overpass to the confluence with the Medina River, which is well downstream from Kelly AFB. Reach 4 was located on Salado Creek, a comparable urban creek in San Antonio which does not receive drainage from Kelly AFB and is therefore a reference stream.

Analytical results were evaluated and contaminants of potential concern were selected by comparison with EPA Region III Risk-Based Concentration Tables. Any value of a contaminant which exceeded the comparison value was selected for further evaluation. Results indicate that PCBs were detected in fish tissue above the comparison value. Other contaminants with at least one value exceeding the comparison value included the pesticides 4,4'- DDD (dichlorodiphenyl-dichloroethane), 4,4'- DDE (dichlorodiphenyl-dichloroethene), and 4,4'-DDT, and the PAHs, benzo(a)pyrene and benzo(b+k)fluoranthene. Aroclor 1260, a PCB, was detected in fish tissue in Reaches 2, 3, and 4 (18).

A risk analysis of PCBs and other contaminants was conducted in order to assess the cumulative risk associated with consumption of fish from Leon Creek. Reach 2 contained the most contaminants at the highest concentrations. The assumptions for risk analysis are presented in Appendix E and results in Table 7. The cumulative increase in risk indicates that no apparent increase in the risk for developing cancer from any of the contaminants would be expected. In addition, PCBs and pesticides did not exceed the Food and Drug Administration Action Levels. The remaining PAHs were only found in a minority of samples. Therefore, ATSDR concludes that consumption of fish caught in Leon Creek does not pose a health threat to recreational anglers.


No apparent public health hazard would be expected from recreational contact with Leon Creek, including swimming, wading, and consumption of fish caught in Leon Creek. Levels of contaminants that are present in Leon Creek and its sediment do not pose a health threat to children, youth, or adults who swim or wade in Leon Creek. Consumption of fish caught in Leon Creek by recreational fishermen would not be expected to result in adverse health effects.



Table 4.

Leon Creek Exposure Pathways
Contaminants Leon Creek Exposure Pathway Elements Time Comments
Source Environmental Media Point of Exposure Route of Exposure Exposed
Surface Water PAHs, VOCs, Metals Abandoned Landfills, NPDES Discharges Water Swimming,
Present Potential exposure. Incidental ingestion while swimming & wading scenario. Below levels of health concern.
PAHs, PCBs, Metals,
Pesticides, Solvents
Abandoned Landfills, NPDES Discharges Sediment Swimming,
Present Potential exposure. Incidental ingestion of suspended sediment. Below levels of health concern.
Abandoned Landfills, NPDES Discharges Fish
Meals Ingestion Child
Present Potential exposure. Consumption of fish caught by recreational fisherman. Below levels of health concern.

Figure 7
Leon Creek Segments


Table 5.

Leon Creek Surface Water
Surface Water Evaluation
Chemical Chemical Type Estimated Risk Concentration (m/kg) a
Comparison Value

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